JPH0760501B2 - Error detection circuit - Google Patents

Description

The present invention relates to an error detection circuit in tracking control of a helical scan type magnetic recording / reproducing apparatus, and more particularly to a DAT.
The error detection circuit for detecting the tilt error of the rotary drum at the time of reproduction with respect to the time of recording, and the height error of the pair of heads arranged on the peripheral surface of the rotary drum at the time of recording and reproduction in the ATF control.

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

FIG. 4 (a) shows the rotating drum 40 and the magnetic tape 4 of the DAT device.
1 is a perspective view showing the relationship between the traveling routes of 1 and the rotary drum 40 is 2
Two heads ha and hb (not shown) are arranged at opposing positions on the peripheral surface thereof and at the same height position where they have the same movement locus, and are rotated in the direction of arrow J at 2000 revolutions per minute. Magnetic tape
41 is transported at a predetermined tape speed v in the direction of arrow K in the tape path formed by the guide rollers 44 and 45 that regulate the movement in the width direction, the rotary drum 40, and the inclined pins 42 and 43.

At this time, the winding angle of the magnetic tape 41 around the peripheral surface of the rotary drum 40 is about 90 degrees (provided that the outer diameter of the rotary drum is 30φ).
In addition, 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 the 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. This ATF area includes blocks P (shown by hatched portions) in which the pilot signal s ₁ is recorded, blocks A and B (in which the sync signals s _{2 of} different frequencies are recorded corresponding to the heads ha and hb, respectively). Horizontal line portion, vertical line portion), and an IBG signal-recorded block D. At the time of signal reproduction, heads ha and hb having a scanning width of about 1.5 times the track width scan alternately on the adjacent tracks,
The signal recorded on the magnetic tape is reproduced. Now, FIG. 3 shows the state of the pilot signal s ₁ reproduced when the head hb scans the track T ₄ . At this time the head hb
Each block P _{51 1} part ATF area E, P _31, P _41, and ATF area of each block P _42, P _52, P ₃₂ and sequentially scanned E _2, the pilot signal s ₁ that has been recorded in the block of this such Are played sequentially.

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. _{Even in the second} copy, the reproduction levels of the blocks P ₃₂ and P ₅₂ are the same. This is for each ATF area E ₁ , E ₂
In the section, 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 and} the width center of the head hb match.

FIG. 11B shows a reproduction level waveform when the head hb scans while 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 stored in each of the tracks T ₅ and T ₃ also increases or decreases in proportion to this deviation. Further, FIG. 7C shows a reproduced waveform when the head hb is scanned with the head track deviated to the left track T ₃ side.
The playback level of T ₃ increases and the playback level of track T ₅ 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 direction and the size of the deviation.

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

FIG. 7 shows a block diagram of an ATF control system used for conventional general ATF control.

In the figure, the reproduction signal s ₀ amplified by the RF amplifier 1 is applied to the low pass filter 2 for detecting the pilot signal s ₁ and the band pass filter 3 for detecting the sync signal s ₂ . The envelope detection circuit 4 has a reproduction frequency of 130.67kH
The pilot signal s _{1 of} z is input, and the level voltage signal s ₃ corresponding to this level is output to the subtractor 6 and the sample hold circuit (hereinafter referred to as SH circuit) 5. The control circuit 34 is
When the sync signal s ₂ is input and it is confirmed that this frequency corresponds to the scanning head, pulsed control signals s ₆ and s ₇ are output at a predetermined timing. 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 5 and 32 hold the input signals by these control signals. Therefore, the SH circuit 5 holds the level voltage of the pilot signal detected from the block P ₅₁ of the right adjacent track T ₅ ,
The SH circuit 32 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 track T ₃ . Since these hold operations are performed each time the heads ha and hb detect the corresponding sync signal s ₂ , the hold signal output from the SH circuit 32 is a tracking error voltage signal (hereinafter TE It is called a voltage signal) s ₅ .

This TE voltage signal s ₅ is averaged by the smoothing circuit 33 to become an average voltage signal s _12, and this average voltage signal s ₁₂ is a capstan motor drive circuit for driving the capstan motor 13 which is the tape transfer means. Enter 12 The capstan motor drive circuit 12 rotationally drives the capstan motor 13 so that the input average voltage signal s ₁₂ becomes 0 level, and the tape speed v is negatively fed back by the ATF control system based on the average voltage signal s _12. It is controlled.

(Problems to be solved by the invention) The scanning center position of the head hb for scanning the ATF area E ₁ part is
The sync signal s ₂ ′ and the level voltage signal corresponding to this head hb detected when moving across each track
s ₃ ′ (as will be described later, since the meaning is slightly different from the sync signal s ₂ and the level voltage signal s ₃ described above, they are distinguished from each other by adding ′), the change locus of each detection level is shown in FIG. b)
Shown in.

First, the level change of the singing signal s ₂ ′ shown in FIG. 5 (a) will be described with reference to FIG. Block B ₄₁
The level Vs ₄ of the sync signal s ₂ ′ detected at
The center of is at the maximum level when scanning the center of the track T ₄ , and does not change until it reaches the position d ₁ which is displaced by 1/4 track in the right adjacent track T ₅ direction (+ direction). Since the width of the head hb passing through the block B ₄₁ decreases, the level Vs ₄ linearly decreases, and eventually reaches the position d ₄ which is further shifted by 1/4 track from the center of the track T ₅ and reaches 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 in response to the + direction movement of the head hb.

The head hb left adjacent tracks T ₃ directions - sync signal s ₂ may have shifted (direction) 'are similarly detected, it is clear that changes as shown in FIG. In addition, level Vs ₂
Is the sync signal detected at block B ₂₁ of track T ₂
s ₂ ′ level.

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 34 controls the block B whose level is higher than the threshold Vf.
The control signals s ₆ and s ₇ are outputted at predetermined timings t ₁ and t ₂ shown in FIG. 3 from the time when the sync signal s ₂ ′ is detected to detect the level of the pilot signal of the adjacent track. Therefore, when the head hb is within the range w ₂ , from the time when the block B ₂₁ where the sync signal is detected is passed, the range w ₄
When it is inside the area, from the time when it passes the block B _41, and when it is inside the range w ₆ from the time when it passes the block B ₆₁ , the level of the block P scanned by the head hb at predetermined timings t ₁ and t ₂ , respectively. Take in the level of the voltage signal s ₃ ′.

Note that once the control circuit 34 detects the sync signal, it does not detect the next sync signal until it outputs the control signals s ₆ and s ₇ based on the sync signal. Therefore, the sync circuit indicated 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 voltage signal s ₃ ′ captured at the timing t ₁
Level Vp ₁ (indicated by a solid line) level and the level voltage signal s ₃ incorporated in the timing t ₂ 'Vp ₂ (shown 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. 5 (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 detecting the pilot signal of the block P ₆₁ at the timing t ₂ , so that the level Vp ₂ increases linearly again. Then, the position where the sync signal detection level of block B ₆₁ exceeds the threshold value Vf
When d ₇ is exceeded, the range becomes w ₆ described above, and the level of the level voltage signal s ₃ ′ of the block P is taken in at predetermined timings t ₁ and t ₂ from the time when the block B ₆₁ is passed. Therefore, the level Vp ₁ becomes 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 becomes the detection level of the pilot signal of the block P ₅₁ to the position d _4. It keeps the maximum level, and linearly decreases when it 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. Also, when the head hb is displaced in one 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, in the ATF area E ₂ part, FIG. 5 (a) shows a change locus of the level voltage signal s ₃ ′ detected when the scanning position of the head hb moves between the tracks.
A description will be given with reference to (c) and 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, 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 change} to the position d ₃ as in the case of the ATF area E ₁ part. However, since the block P detected at the timing t ₂ at this time does not exist even if the position d ₃ is exceeded, the level is
Vp ₂ does not increase like the ATF area E ₁ part, and maintains 0 state.
On the other hand, the detection block B ₄₂ level Vp ₁ is sync signal
From position d ₇ which replaces B ₆₂ to position d ₄ , block P ₄₂
The detection level of the pilot signal is, and as shown in the figure, it linearly decreases as the head hb moves in the + direction.

As described above, when the scanning position of the head hb moves between tracks
Although the level change locus of the pilot signal detected in the ATF areas E ₁ and E ₂ has been described, the pilot signal also changes when the head ha moves between tracks. However, in this case, in the correspondence 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, the locus of the pilot signal level changes in the ATF area E ₁ is shown in (c) of FIG.
The locus of the level change of the pilot signal in the area E ₂ has the waveform 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 head h in the ATF area E ₂ .
This is because the arrangement relationship between the block A and the block P of the sync signal corresponding to a matches.

The TE voltage signal s ₅ output from the SH circuit 32 of FIG. 7 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 conditions. Becomes FIG. 5 (d) shows a change locus obtained by drawing a solid line into a dotted line in FIG. 5 (b), and FIG. 5 (e) shows a change locus obtained by drawing a solid line into a dotted line in FIG. 5 (c). Therefore, when the scanning position of each head ha, hb moves between tracks, the head ha moves to the ATF area E.
₁ of the corresponding change in the locus on the corresponding differential voltage Vb ₂ obtained by detecting a sync signal for the drawing of the difference voltage Va ₁ and head hb obtained by detecting a sync signal ATF area E ₂ (e) moving, the difference voltage Va ₂ obtained by detecting a sync signal differential voltage Vb ₁ and head ha obtained by detecting the sync signal corresponding ATF area E ₂ of the head hb corresponding to ATF area E ₁ is It moves on the change locus of FIG.

Now, a rotary drum in which the heads ha and hb are arranged at the same height position (the position where the movement loci are the same) as during recording is set at the same reference angle θr as the angle between the axis and the tape running direction during recording every minute. It is rotated at 2000 rpm and the tape speed is almost the same as when recording.
When reproducing the ATF signal of the tape transported by vp, the scanning positions of the heads ha and hb that scan the ATF areas E ₁ and E ₂ have the same positional relationship with the center of the corresponding track Tr. Become. In this case, the differential voltages Vb ₁ and Va ₂ and the differential voltages Va ₁ and Vb ₂ on the change loci of FIGS. 5D and 5E are on the coaxial line and move.

On the other hand, when the heads ha and hb have a height difference, the scanning position of each head is the track T corresponding to each of the ATF areas E _1.
The positional relationship with respect to the center of r causes a height error wh according to the height deviation, and further, the same amount of height error wh occurs in the ATF area E ₂ . These errors wh are the difference voltages Va ₁ and Vb ₁ and Va ₂ and Vb _{2 in} FIGS. 5 (d) and 5 (e).
Can be expressed as an error in the moving position of the.

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 rotary 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, so that the head ha The positional relationship between the traveling position of the ATF area E _{1 and} the corresponding track center Tr and the positional relationship of the ATF area E ₂ relative to the corresponding track center Tr cause a tilt error ws depending on the tilt. Further, the same amount of inclination error ws occurs in the head hb as well. These errors ws
Can be expressed as an error in the moving positions of the difference voltages Va ₁ and Va ₂ and Vb ₁ and Vb ₂ in FIGS. 5 (d) and 5 (e).

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 caused when the head height and the rotary drum inclination during recording and reproduction are different.

In this case, if the tape speed fluctuates and the relative positional relationship between each head and the track shifts, it is output from the SH circuit 32.
The differential voltages Va ₁ , Va ₂ , Vb ₁ and Vb ₂ of the TE voltage signal s ₅ move along the change loci of FIGS. 5D and 5E while maintaining the errors wh and ws. For example, tape speed Vr during recording
When the relationship between the tape speed Vp and the tape speed Vp during reproduction is Vr <Vp, it moves in the + direction, and conversely, when Vr> Vp, it moves in the-direction.

As described above, in general, the ATF control negatively controls the tape speed v so that the average level of the TE voltage signal s ₅ becomes 0 level, and therefore, the level of each differential voltage is normally 5 (d), It stabilizes at the position shown in e).

As described above, the ATF control causes the heads ha and hb to scan the corresponding tracks. However, if there is a tilt error of the rotating drum during recording and reproduction, the head scanning locus is in the track direction. It is played in a state that is not parallel to the head, and during recording and playback, the heads ha and hb
If the height relationship between the two is different, the reproduction is performed in a state where the track center and the head center do not coincide with each other, and the reproduction condition deteriorates in any case.

In the conventional circuit configuration described above, the head height error and the rotary drum tilt error cannot be detected, and the reproduction condition is optimal.
Or, it was not possible to know whether the condition was within the allowable range.

It is a first object of the present invention to provide a rotary drum tilt error detection circuit capable of detecting a rotary drum tilt error during recording and reproduction.

It is a second object of the present invention to provide a head height error detection circuit capable of detecting an error in the height relationship between the head ha and hb that can be set during recording and reproduction.

(Means for Solving Problems) (1) By the helical scan method, the first and second heads arranged on the peripheral surface of the rotating drum are used to control the speed of each magnetic tape track by ATF control. Error for reproducing the pilot signals recorded in the first and second areas near both ends and detecting an angular error of the rotary shaft of the rotary drum with respect to the running direction of the magnetic tape based on the reproduced pilot signals. A detection circuit, wherein the first (second) head is synchronized with the detection of the sync signal recorded on the corresponding first (second) track in the first area, A first (second) sample and hold circuit that sequentially samples and holds level difference information of a pair of pilot signals of another track detected at timing 2; and the first (second) head , A level of a pair of pilot signals of another track which is synchronized with the detection of the sync signal recorded on the corresponding first (second) track in the second area and which is detected at the first and second timings A third (fourth) sample-hold circuit for sequentially sampling and holding difference information; an output signal of the first (second) sample-hold circuit and an output signal of the third (fourth) sample-hold circuit. It comprises a subtracter for obtaining level difference information, and tape speed control means for ATF controlling the transfer speed of the magnetic tape based on the level difference information.

(2) With the helical scan method, the first and second heads arranged on the peripheral surface of the rotary drum have the first and second heads in the vicinity of both ends of each track of the magnetic tape whose tape speed is controlled by the ATF control. An error detection circuit that reproduces a pilot signal recorded in an area and detects a height error between the heads based on the reproduced pilot signal, wherein the first head is the first (second) Of the 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 in the corresponding first track in the area The first (third) sample and hold circuit and the second head detect the sync signal recorded on the corresponding second track in the first (second) area. And a second (fourth) sample and hold circuit that sequentially samples and holds the level difference information of the pair of pilot signals of the other track detected at the first and second timings; and the first (third) sample and hold circuit. A subtractor for obtaining level difference information between the output signal of the sample and hold circuit and the output signal of the second (fourth) sample and hold circuit, and ATF controlling the transfer speed of the magnetic tape based on the level difference information. Tape speed control means.

(Operation) (1) Detecting the scanning position when the head scans the corresponding track in each of the first and second areas,
By obtaining the difference between them, the tilt error of the rotary drum at the time of reproduction from that at the time of recording is detected.

(2) Scanning position when the first head scans the first track and scanning when the second head scans the second track in the first or second area By obtaining the difference from the position, the height error between the pair of heads arranged on the peripheral surface of the rotary drum at the time of recording and reproducing is detected.

(Embodiment) FIG. 1 shows a configuration 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.

In the figure, the output terminals 14 _{1 to} 14 ₄ of the control circuit 14 are respectively
While being connected to one of the input terminals of AND circuits 20-23,
Mono Multi Vibrator (hereinafter referred to as Mono Multi) 15-
The output terminal is connected via 18 to the input terminal of the OR circuit 19 connected to the control signal input terminal of the SH circuit 5, and the output terminal
14 ₅ is connected to the other input terminal of the AND circuit 20 to 23.

The control signal input terminals of the SH circuits 7 to 10 are connected to the output terminals of the AND circuits 20 to 23, respectively, and the respective input terminals thereof are both connected to the output terminal of the subtractor 6. The output terminal of the SH circuit 7 is the input terminal of the adder 11 and the + of each of the subtracters 24 and 26.
The output terminals of the SH circuit 8 are connected to the input terminals respectively.
Input terminal of adder 11, -input terminal of subtractor 24 and + of 27
The output terminals of the SH circuit 9 are connected to the input terminals respectively.
The input terminal of the adder 11, the + input terminal of the subtractor 25, and the − of 26
The output terminals of the SH circuit 10 are connected to the input terminals respectively.
The input terminals of the adder 11 and the minus input terminals of the subtracters 25 and 27 are connected, respectively.

The output terminal of the adder 11 is connected to the input terminal of a capstan motor control circuit 12 that controls the capstan motor 13. Furthermore, the output terminals of the subtracters 24 and 25 are connected to the input terminals of the adder 28, and the output terminals of the subtractors 26 and 27 are connected to the input terminal of the adder 29, respectively.

In the above configuration, the control circuit 14 inputs the sync signal s _2, while confirming that it corresponds to the head the frequency of the sync signal s ₂ is scanning, the head ha, of hb, both ATF detected by the head and shown in Fig. 2
After confirming whether detected in either of the areas E _1, E ₂ area, the corresponding output terminal with a sequence "H" state at the timing of t ₁ shown in FIG. 3, t ₂ from the output terminal 14 ₅ The control signal s ₇ is output at the timing of. That is, FIG. 6 (a)
The output signal waveform of the output terminal 14 ₁ shown in FIG. ₂ is in the “H” state based on the sync signal s ₂ detected in the block A when the head ha scans the corresponding track of the ATF area E ₁ , The output signal waveform of output terminal 14 ₂ shown in
Becomes the “H” state based on the sync signal s ₂ detected in the block A when the corresponding track of the ATF area E ₂ is scanned. Similarly, the output signal waveform of the output terminal 14 ₃ shown in FIG. 7C is the same as the output signal waveform of the output terminal 14 ₄ shown in FIG. 7D when the head hb scans the corresponding track of the ATF area E ₁ . The signal waveform becomes “H” state based on the sync signal s ₂ detected in the block B when the head hb scans the corresponding track of the ATF area E ₂ .

Further, as described above, the timing when each of these output terminals becomes the “H” state is the timing of t ₁ shown in FIG.

Note that the control circuit 14 will not describe in detail how to identify these, but it is possible to identify which head is scanning by obtaining the rotation information of the rotating drum, Whether or not the head is scanning the corresponding track can be determined by identifying the frequency of the sync signal reproduced by the head as described above.
Furthermore, the regularity of the reproduced sync signal s ₂ , that is, the head ha
Syncs the sync signals detected in each ATF area E ₁ and E _2.
Let a ₁ , sa ₂ and the sync signals detected by the head hb in each ATE area E ₁ , E ₂ be sb ₁ , sb ₂ , respectively. These are… sa ₁ , sa ₂ , sb ₁ , sb ₂ , sa ₁ Appear with regularity in this order, and by utilizing this regularity, the "H" timing of each output terminal can be obtained.

The mono-multis 15 to 18 output a pulse having a predetermined width in synchronization with the rising edge of the input signal. Therefore, the pulse of the pulse-shaped control signal s ₆ output from the OR circuit 19 is transmitted by the head to each ATF.
The SH circuit 5 appears at the timing of t ₁ shown in FIG. 3 every time the area is scanned, and the SH circuit 5 holds the level voltage of the level voltage signal s ₃ at the timing of “H”. On the other hand, AND circuit 20
23 to 23, the output signals of the control circuit 14 and the control signal s ₇ are input, and the AND signals s _{8 to} s ₁₁ shown in FIG.
Output to 10 control signal input terminals. SH circuits 7-10
Input the level difference signal s ₄ and sample and hold at the "H" timing of the AND signal. Therefore, the SH circuit 7 the difference voltage Va _1, SH circuit 8 the difference voltage Va _2, the SH circuit 9 difference voltage Vb _1, SH circuit 10 TE voltage signal s ₅₁ to sequentially update the differential voltage Vb ₂ ~ Output s ₅₄ respectively.

The voltages of the TE voltage signals s _{51 to} s ₅₄ are shown in FIGS. 5 (d) and 5 (e).
FIGS. 6 (k) to 6 (n) show a state in which the voltage is sequentially updated based on each stable differential voltage in the level state shown in FIG. In this case, the TE output by each SH circuit 7-10
The difference voltage Va ₁ , Va ₂ , Vb ₁ , Vb ₂ of the voltage signal does not change,
When the position of the differential voltage shown in FIGS. 5 (d) and 5 (e) moves along each locus in accordance with the change of the tape speed v, it is apparent that the level of each differential voltage changes for each sampling.

Further, the adder 11 outputs the added voltage signal s ₁₂ obtained by adding the TE voltage signals s _{51 to} s _54, and the voltage level of the added voltage signal s ₁₂ is the differential voltages Va ₁ , Va ₂ , which are sequentially updated, Average level of Vb ₁ and Vb ₂ , that is, ATF scanned by each head ha, hb
The average position of the center position of the head with respect to the track center of the areas E ₁ and E ₂ is shown, and changes depending on the tape speed fluctuation.
The operations of the capstan motor control circuit 12 and the capstan motor 13 which input the added voltage signal s ₁₂ are the same as the operations in FIG. Although the smoothing circuit is not provided after the adder 11 in the above embodiment, a smoothing circuit may be provided as necessary for the purpose of making the ATF control have desired characteristics.

The subtracter 24 outputs the level difference between the TE voltage signals s ₅₁ and s ₅₂ , that is, the slope error signal s ₁₃ of (Va ₁ −Va ₂ ), and the subtractor 25
Is the level difference between the TE voltage signals s ₅₃ and s ₅₄ , that is (Vb ₁ −V
The tilt error signal s ₁₄ of b ₂ ) is output. As is clear from the description of FIGS. 5 (d) and 5 (e), the respective levels of the respective tilt error signals s ₁₃ and s ₁₄ are the same as those at the time of recording in the angular relationship of FIG. It appears as a negative voltage when the angle of the rotating drum at the time of reproduction is inclined in the − direction with respect to the angle θr of the rotating drum, and appears as a positive voltage when the angle of the rotating drum is inclined in the + direction, and its magnitude is It is almost proportional to the error angle.

However, the above relationship holds true for the difference voltages Va ₁ , Va ₂ , Vb.
₁ and Vb ₂ are present in the range wa shown in FIG. 5, and the trajectories within this range are not in a straight line, the levels of the tilt error signals s ₁₃ and s ₁₄ are Depending on the state, it is not exactly proportional to the error angle.

On the other hand, the subtracter 26 outputs the level difference between the TE voltage signals s ₅₁ and s ₅₃ , that is, the height error signal s ₁₆ of (Va ₁ −Vb ₁ ), and the subtractor 2
7 is the level difference between the TE voltage signals s ₅₂ and s ₅₄ , that is (Va ₂ −Vb
₂ ) Height error signal s ₁₇ is output. As is clear from the description of FIGS. 5 (d) and 5 (e) above, the respective height error signals ₁₆ and s ₁₇ have different levels with respect to the height position of the head hb with respect to the head ha during reproduction. When the height is lower than the height of the head hb with respect to the head ha at the time of recording, it appears as a positive voltage, and when it is high, it appears as a negative voltage, and its magnitude is substantially proportional to the height error.

However, the above relationship holds true for the difference voltages Va ₁ , Va ₂ , Vb.
₁ and Vb ₂ are within the range wa shown in FIG. 5, and the trajectories within this range are not in a straight line, the levels of the error signals ₁₆ and s ₁₇ depend on the state. Is not exactly proportional to the height error.

In the embodiment of FIG. 1, the tilt error signals s ₁₃ and s ₁₄ are added by the adder 28 to form the tilt error output signal s ₁₅ .
The information contained in these signals is considered to be almost the same.
Further, the height error output signals s ₁₈ are formed by adding the height error signals ₁₆ and s ₁₇ by the adder 29, but the information contained in these signals is considered to be almost the same.

FIG. 8 is based on these error output signals s ₁₅ and s ₁₈ ,
FIG. 3 is a configuration diagram of a display unit showing an example of use of the circuit of the present invention, which enables visual confirmation of inclination error and / or height error.
The operation will be described.

In FIG. 8 (a), the display drive circuit 22 inputs an error output signal to its input terminal 21, and turns on each dot of the display 23 corresponding to this level. That is, when the input level of the error output signal is positive, the dot on the plus side displayed on the display 23 and at a position where the distance from the zero position is approximately proportional to the input level is lit, and when the input level is negative, Similarly, the corresponding dot on the minus side is turned on, and when the input level is 0V, the dot at the zero position is turned on.

When the dots other than the zero position are turned on, it is possible to drive all the dots between this dot and the dot at the zero position to be turned on.

FIG. 8 (b) shows another method of the display means. The display drive circuit 22 'inputs the error output signal to its input terminal 21', and the arrow-shaped lighting portion 2 of the display 23 '.
3 _{'1, 23' 2} lights. That is, when the input level is within a predetermined range near 0V, both the lighting parts 23 ' ₁ and 23' ₂ are turned on, and when the input level is less than the predetermined range, the lighting part 23 ' ₁ is turned on.
Only ₂ is turned on, and when it is on the plus side of this predetermined range, only the lighting part 23 ' ₁ is turned on.

The present invention is not limited to the embodiment shown in FIG. 1, and it goes without saying that various modes can be obtained.

(Effect of the Invention) According to the present invention, the inclination error amount of the rotary drum or the height error amount of the pair of heads arranged at a predetermined position on the peripheral surface of the rotary drum can be detected. Available for For example, by configuring each correction control device by combining with the inclination correction means of the rotating drum, the height correction means of the head, or the like, accurate tracking without such errors can be realized.

Further, if the inspection jig using the present invention is used in the production line, it is possible to use it for various purposes such as checking the variation error in the production by reproducing the reference tape prepared in advance. .

[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 in respective parts of FIG. 7th
FIG. 8 is a block diagram of an ATF control system used for conventional general ATF control, and FIG. 8 is a configuration diagram of display means showing an application example of the present invention. 1 ... RF amplifier, 2 ... Low-pass filter, 3 ... Band-pass filter, 4 ... Envelope detection circuit, 5, 3
2, 7-10 ... Sample and hold circuit, 6, 24-27 ...
Subtractor, 11, 28, 29 ... Adder, 12 ... Capstan motor drive circuit, 13 ... Capstan motor, 14, 34 ...
Control circuit, 15-18 …… Mono multivibrator, 19 ……
OR circuit, 20-23 …… AND circuit, 33 …… Smoothing circuit.

Claims (2)

[Claims] 1. A first and a second head arranged on the peripheral surface of a rotary drum by a helical scan method, in which the first and second heads in the vicinity of both ends of each track of a magnetic tape whose tape speed is controlled by ATF control. An error detection circuit for reproducing the pilot signal recorded in the area 2 and detecting an angular error of the rotation axis of the rotary drum with respect to the running direction of the magnetic tape based on the reproduced pilot signal; Another track in which the (second) head is synchronized with the detection of the sync signal recorded on the corresponding first (second) track in the first area and is detected at different first and second timings. A first (second) sample and hold circuit for sequentially sampling and holding the level difference information of the pair of pilot signals, and the first (second) head in the second area. Corresponding to the detection of the sync signal recorded on the corresponding first (second) track, and sequentially sample and hold the level difference information of the pair of pilot signals of the other tracks detected at the first and second timings. A third (fourth) sample-and-hold circuit for obtaining the level difference information between the output signal of the first (second) sample-and-hold circuit and the output signal of the third (fourth) sample-and-hold circuit. An error detection circuit comprising a calculator and tape speed control means for ATF controlling the transfer speed of the magnetic tape based on the level difference information. 2. A first and a second heads arranged on the peripheral surface of a rotary drum by a helical scan method, wherein the first and the second heads in the vicinity of both ends of each track of a magnetic tape whose tape speed is controlled by ATF control. 2 is an error detection circuit for reproducing the pilot signal recorded in the area 2 and detecting a height error between the heads based on the reproduced pilot signal, wherein the first head is the first (first) In the area 2), in synchronization with the detection of the sync signal recorded on the corresponding first track, and the level difference information of the pair of pilot signals of the other tracks detected at different first and second timings is sequentially sampled and held. A first (third) sample and hold circuit for detecting the sync signal recorded on the corresponding second track in the first (second) area. And a second (fourth) sample-and-hold circuit that sequentially samples and holds the level difference information of the pair of pilot signals of the other tracks detected at the first and second timings. ), A subtractor for obtaining level difference information between the output signal of the sample and hold circuit and the output signal of the second (fourth) sample and hold circuit, and the transfer speed of the magnetic tape based on the level difference information. An error detection circuit comprising a tape speed control means for controlling.