JPS60185223A - Rotary magnetic head device - Google Patents

Abstract

PURPOSE:To extract a control signal for setting a proper step on the basis of the combination of plural rotatable heads by forming an erasing/reproducing magnetic head having wider effective head width at a reproducing time as compared with that of an erasing time and controlling plural rotatable magnetic heads so that a pilot signal reproduced by the head is kept at a prescribed level. CONSTITUTION:The step between a rotary magnetic (BM) head 11A/B and a rotary erasing (FE) head 60R is adjusted by a signal from a displacement signal generator 74 through a bimorph 40A/B and the step between the heads 11A and 11B is also adjusted. A pilot signal from the FE head 60R is compared with a reference voltage Vr by a comparator 78 through an erase signal removing circuit 77, a reproducing amplifier 51, a BPF53, and an envelope detector 54. When both the values coincide with each other, a sampling signal is supplied to an S/H circuit 73 to sample-hold a replacement signal from the generator 74. Then, the driving voltage of the bimorph 40A/B is kept at a prescribed value and the step between the BM head 11A/B and the FE head 60R is maintained properly.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to helical scan video tape recorders (VTRs).
) The present invention relates to a position control device for a rotary magnetic head which is commonly used and suitable for the following.

Background Art and Problems In a helical scanning VTR, a rotating magnetic head is attached to an electro-mechanical converter such as a bimorph, and a required driving voltage is supplied to the bimorph to move the head in a direction approximately perpendicular to the scanning direction. It is well known to provide a device which allows the head to accurately scan an inclined track on the tape from beginning to end. In addition, such a device is used during variable speed playback;
(Dynamic Track
) device.

In order for a DTP device to operate properly, it is naturally necessary to be able to sense the position of the head relative to the sloping track on the tape. Regarding this head position detection, many methods have been proposed in the past.

On the other hand, even during constant speed playback of a VTR, the head accurately scans the playback track on the tape by the cab scan phase servo. In the case of this tracking servo as well, it is necessary to be able to detect the position of the head with respect to the track.

For this reason, it has been widely practiced to record a control signal on a control track provided at the edge of the tape, and use this control signal to apply tracking servo to the capstan.

However, with such a one-rack control system, only tracking information near the starting point of the recording trunk can be obtained, making it difficult to maintain the required tracking accuracy over the entire length of the track.

Therefore, as an alternative to the control track method, a method has been proposed in which a plurality of different pilot signals are sequentially and cyclically recorded on each track on a tape, and the pilot signals are referred to during playback to perform trunking servo.

First, this pilot signal system will be explained with reference to FIGS. 1 and 2.

In the pilot signal system, as shown in FIG. 1, frequencies f1 . Four types of biloft signals are set: f2+f3 and f4. The frequencies f1 to f4 of each pilot signal are, for example, as follows.

f 1 =, 102.54 kHz f 2 = 118.95 kl (z f 3 = 165.21 kllz f 4 = 148.69 kHz As can be seen from this, the following relationship holds true between the frequencies of each pilot signal.

Ifz f21=Ifa f+ 1=ft=16kHz
lf2-f31=lf4 fl 1=fH-46k)I
When recording z, the pilot signals f1 to f4 as described above are
is frequency-multiplexed with the carrier luminance signal YFM and the low frequency converted chromaticity signal CL, and is sequentially and cyclically recorded on each trunk on the tape.

FIG. 2 shows an example of the configuration of a tracking servo using the pilot signal method.

In FIG. 2, pilot signals are recorded as described above, and each track t of the tape VT traveling in the direction of the arrow is shown.
1+ t21 t 3+ t4... is the rotating head (
11), the recorded signal is sequentially scanned and reproduced. The reproduced signal from the head (11) is sent to the reciprocating amplifier (12).
), and among the outputs of the intensifier (12),
The carrier luminance signal YFM and the low frequency conversion chromaticity signal CL are supplied to a reproduction processing circuit (13) and undergo signal processing such as demodulation.

(20) shows the head position sensing device as a whole, and the pilot signal component from the amplifier (12) is filtered through a low-pass filter (
21) and supplied to the multiplier (22). The multiplier (22) is connected to a signal generator (24) via an electronic rotary switch (23) that is synchronized with the rotary head (11) sequentially scanning the tracks t1 to t4 on the edge of the tape. ), the frequencies from fl, f4 . f3.
A reference viroft signal of fx is provided cyclically in this frequency order.

In addition to the original pilot signal recorded for each trunk, the reproduced pilot signal component includes crosstalk components from each of the preceding and subsequent adjacent tracks. Therefore, when the reproduced pyro-node signal component is multiplied by the reference pilot signal in the multiplier (22), a difference signal component as shown in the following table is generated.

These difference signal components H and fL are subjected to peak detection "W(2) through bandpass filters (25) and (26), respectively.
7) and (28). The outputs of the detectors (27) and 28) are respectively supplied to one and the other input terminals of the differential amplifier (29).

The error signal output of the differential amplifier (29) is supplied to the capstan servo circuit (30), and the output of the servo circuit (3o) is supplied to the capstan motor (3) via the drive amplifier (31).
2).

As is clear from the table above, in the multiplier (22), the frequency f is increased due to crosstalk from the preceding track.
A difference signal of H is obtained, whereas a difference signal of frequency rL is obtained due to crosstalk from the trailing track. Therefore, by comparing the levels of the difference signals fH and fL, it is detected whether the head has deviated from a predetermined track in the positive or negative direction. Therefore, in order to track a given trunk, the capstan motor (32) should be controlled so that both difference signals are at the same level and the error signal output of the differential amplifier (29) is at zero level. .

The tracking servo using the pilot signal as described above is called ATF (＾Automatic Track Fi).
This ATF type head position detection technology can be directly applied to head position detection in a DTF device.

FIG. 3 shows an example of the configuration of a DTP device using an ATF type error signal. In FIG. 3, parts corresponding to those in FIG. 2 are designated by the same reference numerals and redundant explanation will be omitted.

In FIG. 3, the bimorph (40) is connected to the drive amplifier (40).
1), an error signal output is supplied from the differential amplifier (29) of the head position detection device (20), and this error signal output causes the rotating magnetic head (11) attached to the bimorph (40) to During variable speed reproduction, the position of 'ζ is also controlled so as to accurately scan from the beginning to the end of a predetermined track.

By the way, the rotating magnetic head (
When recording using multiple 8M heads (hereinafter abbreviated as 8M heads), it is necessary to match the height of each 8M head, that is, to eliminate the step between them, to obtain a recording pattern with a uniform track pitch of □. . However, due to the hysteresis characteristic of the bimorph itself, simply returning the drive voltage to zero does not restore the initial displacement state, and there is a possibility that the track pitch may be disturbed.

Therefore, a specific frequency fs (f
A method has been proposed in which the pilot of 8M head (different from z~f4) is intermittently recorded and the amount of displacement of the 8M head is controlled so that the crosstalk of the signal of f5 from the preceding adjacent track is at a constant level (Japanese Patent Application Laid-Open No. Publication No. 54-115113)
.

In this crosstalk playback method, in order to prevent the f5 pilot signal from affecting the playback screen, one horizontal scanning period ( During IH), frequency f6 is 223k
Record the Hz signal.

Then, during the next LH, the recording current is cut off and the reproduction (P
B) Set to mode. Note that the recording period of the f5 signal of the preceding adjacent track and the reproduction mode period of the succeeding track are aligned in the width direction of the track on the tape. In this way, each 8M head will have 1
Since the crosstalk of the r5 signal recorded before the track is reproduced in burst form, if the displacement amount, that is, the quotient of each 8M head is controlled so that the level of the reproduced f5 signal is constant, each The heights of the 8M heads are made equal, and the track pitch can be made uniform.

FIG. 5 shows an example of the configuration of a BM head control circuit using the crosstalk reproduction method.

In Figure 5, two 8M heads (11^) and (1
1B) are arranged at an angle of 180° within a head drum (not shown), as is well known. Also, since the magnetic tape runs diagonally along the circumference of the head drum with a 180' (or 221°) winding at an angle, each trunk on the tape is connected to both heads (11^) and (IIB
) are scanned alternately. In the case of a track pattern as shown in FIG. 4, tracks t1 and t3 are
IA), and tracks L2 and t4 are scanned by the head (11B). Therefore, an output is taken out from each head (11A) or (IIB) for each frame.

During recording, the switch S is closed, and the recording current is applied from the recording signal input terminal (50) to the BM head (11Δ) and (IIB) of 2(flit), to the capacitor C, and to each trunk via C and B. When in the playback mode, the switch S is opened by a control pulse and the 8M head (IIA) or (IIB) regenerates the crosstalk of the f5 signal from the preceding adjacent track.The 6BM head (IIA) and the capacitor The playback output of both BM heads (IIA) and CIIB is transmitted for each track through a transformer T that is bridge-connected between the connection midpoint of C^ and the connection midpoint of the 8M head (IIB > and capacitor CB). It is alternately supplied to the regenerative amplifier (51).
Only during the B mode period, a control pulse is supplied from the control terminal (52), and the amplifier (51) is put into operation. The output of the amplifier (51) is supplied to an envelope detector (54) via a bandpass filter (53). The output of the detector (54) is sent to a sample hold circuit (hereinafter referred to as S/H circuit) (55
A) and (55B) are commonly supplied.

Both S/H circuits (55/l) and (55B) perform S/H operations alternately during the reproduction mode period of each track by sampling signals supplied to their respective control terminals (56A) and (56B). be exposed. Both S/H circuits (55^
) and (55B) represent the amplitude of the crosstalk of the signal at f5 during scanning of two adjacent tracks. These output signals are supplied to a differential amplifier (57),
The output is taken out from the output terminal (58) as a position control signal for the 8M head.

The above-mentioned DTP technology using the ATF method and head control technology using crosstalk playback have already been proposed to the industry and have been adopted in a new method of compact VTRs (8 mm video, hereinafter referred to as the 8■ method) for which the standard has been unified. ing.

Here, the 8■ method will be briefly explained with reference to FIGS. 6 to 8.

As is clear from the frequency spectrum in Figure 6, 8V
In this method, the FM audio signal AFM is the carrier luminance signal Y.
A frequency domain is set between the FM and the low frequency conversion chromaticity signal CL, and frequency multiplex recording is performed with the video signal. Furthermore, as an option, as shown in the formant of FIG.
A two-channel PCM audio signal can be recorded in advance of the video signal, and only the audio signal can be recorded later (after recording). When recording and reproducing a PCM audio signal, the angle of the tape winding around the head drum is set to 22°, and the angle (recording area) of the winding of the PCM audio signal and video signal on the tape is set to 26°, respectively. 3° and 180°. Between each recording area of the PCM audio signal and video signal, there is provided an area for recording and reproducing a pilot signal using the above-mentioned Kukostalk reproduction method. Therefore, if we pay attention to the fG multiplied signal of the 8V system, the trunk pattern will be as shown in FIG. As can be seen from FIG. 7, there are some blank spaces at the beginning of each trunk.

As mentioned above, in the 8v system, the audio signal is either converted to FM and frequency multiplexed with the video signal, or converted to PCM and recorded by dividing the area into areas on the extended track preceding the video signal recording area. Therefore, the audio head used in conventional VTRs becomes unnecessary in any case. Also,
Since ATF based on pilot signals is used, a control signal head is not required, and therefore, an audio/control erase head is also not required. ``Then, if we mounted a video erasing head on a rotating disk like the video head, electronic editing would be possible.''
This is practical and improves tape running accuracy. Also,
Rotating erase heads (hereinafter referred to as FE heads) require only a few trunks to be erased at a time, significantly reducing erase power requirements compared to full tape width erases such as traditional fixed erase heads. As the erasing signal, the carrier luminance signal YFM itself or a signal with a single frequency higher than the upper limit frequency of the carrier luminance signal is used in order to avoid interference with the recording signal.

When using both the F'E head and the 8M head, as conceptually shown in Fig. 9, the head drum (rotating drum) I
A rotating body (not shown) to which two (solid 8M heads (118) and (lull) bimorphs (40A>' and (40B)) are installed - inside the ID - at an angle of 180°. ), the FE head (60) is usually installed at an angle of 90° with respect to both the BM heads (118) and (IIB).
The erasing width of 60) is set to approximately one or two times the track width.

When recording using such a rotating head system, the step difference between both BM heads (11^) and (11B) is eliminated by the aforementioned crosstalk reproduction method, and a recording pattern with a uniform track pitch can be obtained. . However, at this point, even if the relative heights between the BM head (11M) and (11B) can maintain a predetermined relationship, the BM head (11^).

(Relative height difference between (IIB) and FB head (60))
Depending on the relative height of each head, newly recorded tracks may be erased immediately after recording, or during after-recording (inserts) or splicing operations. Moreover, there is a possibility that the newly recorded first track may overlap with the old recording track, or that there may be an over-erased portion at the end.

OBJECTS OF THE INVENTION In view of the above, an object of the present invention is to provide a rotary magnetic head device having a rotary erasing head capable of extracting a control signal for setting an appropriate yi difference in combination with a rotary movable head. There is one for each.

SUMMARY OF THE INVENTION The present invention records and reproduces a first biloft signal over the entire length of each adjacent track on a record carrier, and a second pilot signal in a first predetermined section of each trunk. a plurality of rotatable movable magnetic heads for recording a second pilot signal recorded in a first predetermined section of an adjacent preceding track in a second predetermined section of each trunk; In a rotary magnetic head device, the position of a plurality of rotatable magnetic heads is controlled by a control signal obtained from the amplitude detector, and the position of a plurality of rotary movable magnetic heads is controlled by a control signal obtained from the amplitude detector. A rotating erase/reproducing magnetic head is provided whose effective head width during reproduction is wider than the effective head width of the
This rotary magnetic head device controls the positions of a plurality of rotatable magnetic heads so that the pilot signal of the rotary magnetic head reaches a predetermined level.

According to the present invention, it is possible to maintain an appropriate level difference between both heads, and there is no possibility of erroneous erasing, overlapping recordings, or excessive erasing during continuous shooting.

Embodiment Hereinafter, an embodiment of a rotary magnetic head device according to the present invention will be described with reference to FIGS. 10 to 13.

Generally, in the case of a video head, the track width is several tens of micrometers.
As shown in FIG. 10, the core C itself has a thickness Tc sufficient to obtain the required mechanical strength, and the thickness at the joint end surface forming the gap g is approximately equal to the track width. It is ground like this.

It is known that when the thicknesses of the core ends on both sides of the gap g are different, the effective track width of the head differs between recording and reproduction.

That is, with respect to the head scanning direction shown by arrow S, the thickness of the joint surface of the front cores IIc and Q is Tp, and the thickness of the joint surface of the rear core Itc
If the thickness of the joint surface of t is Tt'(<Ti), the effective track width during recording is wl-1, and the effective track width during playback is Wp, then the following equations (1) and (21) hold true. .

vty! #Tt...+11 Wp='rt+(X (TJ -Tt)...
+2) Here, α is a constant (approximately 0.5 to 0.6).While the effective track width during recording and erasing is determined by the thickness Tt of the rear core HCt, even if the head is the same, During reproduction, the entire joint end surface of the front core 1102 contributes, and the effective track width is expanded by approximately half the difference in thickness between the two cores. Hereinafter, the wide portion of the front core corresponding to the difference in thickness (TE Tt) between both cores will be referred to as an enlarged reproduction area. The reproduction output for each minute unit width of this enlarged reproduction area is not constant, and its contribution rate (amplitude) distribution is determined by the shape of the vicinity of the core end face.

FIG. 11 shows a main part of an embodiment of a rotating magnetic helad apparatus according to the present invention based on this knowledge.

In FIG. 11, the upper edges (61a) and (62a) of each joining end surface of the front core (61) and the rear core (62) with respect to the scanning direction (arrow S) of the FE head are the head scanning direction S. The lower edges (61b) and (62b) are offset by the difference TD between the thicknesses TL and 'r' at the joint end faces of both cores (61) and (62).

In this example, ζ is the thickness T of the rear core (62), where the width of the recording trunk (track pinch) is WFL.
T, the joint end surface of the front core (61) opposite the lower edge (62b) of the rear core (62) from the second point (61c) to the lower edge (
Width T of the enlarged playback area up to 61b). are set as shown in the following equations (31 and (41), respectively.

TT≧2WR...(3) To #1.5Wa...(4) Moreover, the upper limit (61c) of the enlarged reproduction area becomes the reference point of the F'B head.

Next, with reference to FIG. 12, an example of a circuit for controlling the 8M head to maintain an appropriate level difference using the rotary magnetic head device according to the present invention will be described. 12th
In the figures, parts corresponding to FIGS. 3, 5, and 9 are designated by the same reference numerals, and redundant explanation will be omitted.

In FIG. 12, (11Δ/B) indicates two 8M heads (118) and (IIB), and as mentioned above, this 10M head (11Δ/B) is connected to the recording amplifier (71). The frequency is fl from the viroft signal generator (72).
~f4 pilot signals are supplied cyclically and sequentially. (
73) is a voltage holding circuit in which the output of the displacement signal generator (74) is connected to the drive amplifier (4) via the S/8 circuit (73).
1), and the output of the drive amplifier (41) is supplied to the bimorph (40A/B).

(601?) is the FE head, and an amplifier (
75) from the erasure signal generator (76).
eD>fx~f4) is supplied, and F
The reproduction output of the E head (60R) is supplied to the reproduction amplifier (51) via the erasure signal removal circuit (trap) (77). (78) is a comparator, one input terminal of which is supplied with the output of the envelope detector (54), and
The reference voltage ■1 is supplied from the terminal (79) to the other input terminal. The output of the comparator (78) is connected to the S/11 circuit (73
).

The operation of the circuit of FIG. 12 is as follows. Initially, the relative height difference between the FE head (60R> and the 8M head (IIA/B)) is not appropriate, so an appropriate displacement signal is output from the generator (74), and the 8M head (lll'l/B) is
) to the lower limit of its displacement range. Then, both BMs are
The steps between the heads (IIA) and (IIB) are matched.

A pilot signal is supplied from the signal generator (72) via the recording amplifier (71) to the 8M head (11Δ/B), which has achieved proper mutual relationship after the step alignment has been completed, and at the same time, the bimorph (40A/B) It is driven by, for example, a sawtooth wave displacement signal (gradient wave signal) from a generator (74).

Therefore, the 8M head (11/l/B) is displaced upward while maintaining proper mutual relationship, and at the same time the pilot signal is recorded on the tape VT.

The 8M head (IIA/B) continues to move upward, and the F
When the height difference with the E head (6011) decreases, the recording trunk by the 8M head (118/B) becomes the FE head (6011).
0) It gradually overlaps with the enlarged reproduction area glue L trace of 1). Then, the FB head (60R) starts reproducing the pilot signal recorded by the 8M head (118/B), and the level of the reproduced pilot signal increases in accordance with the displacement of the 8M head (118/B).

As the full width of the enlarged playback area of the FE head (60R>) scans the recording track of the 8M head (IIA/B),
The level of the reproduced pilot signal from the FE head (60R) reaches its maximum value. After that, 8M head (118/B
) rises and the recording track is placed on the FB head (60
Even if it overlaps with the locus of the rear core (62) of F
Since the E head (60R') D is supplied with the erase signal fe, the part of the recording track of the 8M head (118/B) that overlaps with the trajectory of the rear head (62) is erased. It does not contribute to increasing the playback level.

Since the track newly recorded by the 8M head (IIB) is not erased by the FE head (60R), the upper edge (reference point) of the 8M head (IIB) is the reference point of the FE head (601?) on the tape pattern. You can't go beyond the point. Furthermore, since it is better to have less unerased data from the previous recording, the smaller the distance d between the reference points of both heads on the tape pattern, the better.

Therefore, it is desirable that this distance d falls within the range expressed by the following equation (5).

Q<d<WR...(5) The regenerated pilot signal from the FB head (60R) is sent to the envelope detector (54) via the cancellation signal removal circuit (77), the regenerative amplifier (51) and the bandpass filter (53). The wave is detected by The output of the detector (54) is compared in the comparator (78) with the reference voltage vR set to satisfy the relationship of equation (5) above, and when the two are equal, the comparator (78) An output is generated in the S/11 circuit (73) as a sampling signal, and the output is supplied to the S/11 circuit (73) as a sampling signal.
74) is sampled and held. From then on,
The drive voltage of the bimorph (40A/B) is maintained at a predetermined value, and the 8M head (118/B) is
) can maintain an appropriate level difference.

Furthermore, with reference to FIG. 13, another example of a circuit for controlling the 8M head to maintain an appropriate level difference using the rotary magnetic head device according to the present invention will be described. 1st
In FIG. 3, parts corresponding to those in FIG. 12 are given the same reference numerals and redundant explanation will be omitted.

In FIG. 13, (538) and (53B) are fl, f3 and f2. It is a bandpass filter that passes the frequency of f4, and the output of the regenerative amplifier (51) is passed through the double bandpass filter (53^) and (53) depending on the frequency.
B), each envelope detector (54A
) and (54B). The output of the detector (54A) is immediately supplied to one input terminal of the comparator (78), and the output of the detector (54B) is supplied to the other input terminal of the comparator (78) via an attenuator (80). Supplied. The rest of the structure is the same as that in FIG. 12.

The operation of the circuit of FIG. 13 is as follows.

As mentioned above, the fl and f3 pilot signals are recorded by the 8M head (IIA), and the f2 and f4 pilot signals are recorded by the 8M head (IIB). Therefore, in the configuration of FIG. 13, the level of the pilot signal reproduced from the A track recorded by the head (118) is determined by the comparator ( 78) for comparison.

Similarly to the above, the 8M head (IIA
/B) is displaced upward while recording a pilot signal, first, the B trunk and the enlarged reproduction area of the FB head (60R) begin to come into contact with each other, and an output is generated at the detector (54B). The 8M head (11^/B) is displaced by 4,
When the enlarged reproduction area of the FE head (60R) comes into contact with the full width of the B track, the output level of the detector (54B) reaches its maximum value.

The 8M head (IIA/B) continues to be displaced further, and when the A track and the enlarged reproduction area of the FE head (60R) begin to come into contact with each other, an output is also generated from the detector (54A). At this time, the output level of the wave detector (54B) maintains its maximum value.

As shown in equation (4) above, the width TD of the expanded playback area of the FE head (60R) is 1.5 d of the track pitch WR.
Therefore, when the 8M head (,118/B) continues to be displaced and the distance d between its reference point and the reference point of the FB head (60R) becomes d→0, the output of the detector (54B) continues to be the maximum value, whereas the output of the detector (54A) never exceeds 1/2 of the maximum value of the output of the detector (54B).

That is, even if the reproduction output contribution rate of the expanded reproduction area of the FE head (60R) is uniformly distributed (the effective trunk width is expanded to the full width of the expanded reproduction area), the detector (54^)
The output is 1/2 of the output of the detector (54B).

When the reproduction output contribution rate is 0 at the lower end (61b) of the expanded reproduction area and increases linearly to 1 at the upper end (61c,), the output of the detector (54A) is
54B). Therefore, if the attenuation amount of the attenuator (80) is set appropriately, the FB head (60R) and 8M head (IIA/B)
When the level difference between the detector and the detector falls within the appropriate range, the output of the detector (54A) becomes equal to the output of the detector (54B) via the attenuator (80), and the output of the comparator (78) becomes equal to the output of the detector (54B) via the attenuator (80). The output of the displacement signal generator (74) is sampled and bolded. The 8M head (118/B) can maintain an appropriate level difference with respect to the FE head (60R).

Effects of the Invention As detailed above, according to the present invention, since a rotary erasing head is used which can reproduce a pilot signal as a displacement signal during reproduction of the rotary movable head as a head displacement detection signal during recording, both It is possible to maintain an appropriate level difference between the heads, and there is no possibility of erroneous erasure, overlapping recordings, or excessive erasure during continuous shooting.

[Brief explanation of the drawing]

Figures 1 and 2 are frequency spectra and block diagrams for explaining the conventional ATF system, and Figure 3 is the conventional ATF system.
FIGS. 4 and 5 are block diagrams showing an example of the configuration of a DTP device using the F technology, and FIGS. 8 is a frequency spectrum, formant, and track pattern for explaining the 8V system, FIG. 9 is a plan view of a rotary head for explaining the present invention, and FIG. 1O is a plan view of the main parts of the erasing/reproducing head. FIG. 11 is a plan view showing essential parts of an embodiment of a rotating magnetic head device according to the present invention, and FIGS. 12 and 13 are block diagrams showing an example of the configuration of a control circuit for the rotating magnetic head device according to the present invention. . (11), (11Δ), '(IIB) and (1
18/B) is a rotating movable magnetic head, (20) is a head position detection device, (54), (54A), (54B)
) is an amplitude detector, (60R) is a rotating erasing/reproducing magnetic head, (72) is a pilot signal generator, and (78) is a comparator.

Claims (1)

[Claims] recording and reproducing a first pilot signal over the entire length of each adjacent track on the record carrier;
A second pilot signal is recorded in a first predetermined section of each of the tracks, and the second pilot signal is recorded in the first predetermined section of an adjacent preceding track in the second predetermined section of each of the tracks. and an amplitude detector that detects the amplitude of the self-reproducing pilot signal by the plurality of rotatable magnetic heads, and a control signal obtained from the amplitude detector to detect the amplitude of the self-reproducing pilot signal. In a rotating magnetic field device configured to control the position of a rotary movable magnetic head, a rotating erase/reproducing magnetic head is provided whose effective head width during reproduction is wider than the effective head width during erasing, and the rotary erasing/reproducing magnetic head is A rotary magnetic head device characterized in that the positions of the plurality of rotatable magnetic heads are controlled so that the first pilot signal reproduced by the reproducing magnetic head reaches a predetermined level.