JPS6213738B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking control device for a magnetic recording/reproducing device such as a VTR.

In conventional rotary head type VTRs, tracking control is performed to ensure that the video track formed on the magnetic tape is scanned correctly by the rotary head during playback, based on control signals recorded on so-called control tracks at the ends of the magnetic tape. A method of controlling the rotational speed of a rotating head or the running speed of a magnetic tape is generally used.

However, in conventional devices that perform tracking control using this control signal, the relative positional relationship between the control head that records and reproduces the control signal and the rotary head must be constant for each device; If the relationship is different for each device, tracking will not be performed correctly, or if the control head's orientation and height relative to the tape are incorrect, the control signal will not be recorded and played back correctly, and tracking control will not be performed correctly. There were problems with the reliability of the device, such as instability.

On the other hand, in order to improve this problem, a method is conventionally known in which tracking is controlled using a vertical synchronization signal that is reproduced and separated from a video track without using a control signal. The conventional example is a rotating two-head type.
The case of VTR is shown in Figure 1.

This figure shows the tracking control device in playback mode. The magnetic tape 1 is driven to run by a capstan motor 5. Reference numerals 21 and 22 denote magnetic heads that alternately record and reproduce video signals on the magnetic tape 1 field by field.
It is mounted at an angle of 180 degrees and rotated together with the disk 2 by a disk motor 4. Two magnets are attached to the disk 2 at an angle of 180 degrees to each other, and by detecting these with the task head 3, a pulse (hereinafter referred to as a disk task pulse) synchronized with the rotation of the magnetic heads 21 and 22 is generated. (abbreviated as DTP) is obtained from task head 3.

The DTP signal from the tack head 3 is phase-adjusted by a phase adjustment circuit 31 so that the magnetic heads 21, 22 and the magnetic tape 1 have a predetermined relative positional relationship, and then supplied to a pulse forming circuit 32.

The pulse S output from this pulse forming circuit 32 has a duty ratio of 50 in synchronization with the DTP signal.
% pulse, whose rising phase and falling phase, the magnetic heads 21 and 22, and the magnetic tape 1
The relative relationship with is determined as follows.

FIG. 2 is a diagram showing the pattern of video tracks on the magnetic tape 1 when video signals are recorded densely so as not to generate guard bands. The relative relationship between 22 and the magnetic tape 1 will be explained.

In FIG. 2, H1 is the starting point of scanning on the magnetic tape 1 of the magnetic head 21.
1 scans the tape to form a video track T1. Similarly, H2 is the scanning start point of the magnetic head 22, and the magnetic head 22 forms an image track T2.

The relative relationship between the scanning start points of H1 and H2 and the end A of the magnetic tape 1 is determined by the relative positional relationship between the disk 2 and the magnetic tape 1 in FIG. The point is located on line H at a location on the tape a fixed distance from end A of the magnetic tape.

S1 is a point where the rising phase of the pulse S corresponds to the position on the video track T1, and similarly, S2 is the point where the falling phase of the pulse S corresponds to the position on the video track T2, The relative positional relationship between these S1 and S2 and the end A of the magnetic tape 1 is as follows in the phase adjustment circuit 31 of FIG.
Determined by the phase adjustment of the DTP signal, these S1 and S2 are located on line G at a position on the tape a certain distance from end A of the magnetic tape. V
1 and V2 are video tracks T1 and T2, respectively.
The recording position of the vertical synchronization signal VS of the video signal, which is recorded alternately for each field, is shown above.

When recording a video signal, the disk servo system is configured so that the pulse S and the vertical synchronization signal VS of the video signal to be recorded have a predetermined phase relationship, that is, S1 and S2 described above in FIG. A control operation is performed so that the recording positions V1 and V2 of the vertical synchronizing signal on the tracks T1 and T2 have a predetermined positional relationship. Figure 3 shows the video track To recorded by the disk servo control during the above recording.
FIG.

In the figure, C is the scanning center line of the video track To, Ho is the scanning start point of the magnetic head, So
is the point where the phase of the pulse S corresponds to the position on the track To, and Vo is the point on the track of the vertical synchronization signal VS.
Indicates the recording position on To. to is a time equal to the phase difference between the pulse S and the vertical synchronizing signal VS, and the disk servo system during recording performs a control operation so that this time to becomes a constant value tc. When reproducing the video track To recorded in this way, consider the case where a tracking shift occurs and the reproduction is performed along the scanning center line shown in C' in the same figure.The scanning start point of the head at this time will be Ho on the above-mentioned H. The phase of the pulse S is located at the point So' on G, and as a result, the time of the phase difference between the reproduced vertical synchronizing signal VS and the pulse S appears as to'.

Therefore, correct tracking can be achieved by controlling the servo system during reproduction so that this time to' becomes a constant value tc determined during recording.

In the case of the rotating two-head type VTR shown in FIG. 1, the disk servo system during playback is set so that the rotational speed of the disk motor 4 is equal to the frame frequency, that is, the frequency of the pulse S is set to the frame frequency. Since it is necessary to perform a control operation so that the frequency is equal to the frequency, in the tracking control system during playback, the vertical synchronization signal VF of the frame period and the vertical synchronization signal VF of the frame period that is played back every other video track recorded and formed alternately at the field period. It is sufficient to perform a control operation so that the time to' of the phase difference of the pulse S of the frame frequency becomes a constant value tc.

That is, in FIG. 1 again, the magnetic head 21
A video signal reproduced by 22 and a video signal reproducing circuit (not shown) is supplied to a vertical synchronization separation circuit 101 via a terminal 100. Vertical synchronization signal VS separated from the reproduced video signal in circuit 101
is lowered to 1/2 in frequency by the frequency lowering circuit 102, and the frame period vertical synchronizing signal VF is output to the circuit 1.
Output from 02. The phase of the vertical synchronizing signal VF from this circuit 102 is compared with the pulse S from the pulse forming circuit 32 in the phase comparison circuit 40, and a phase error signal corresponding to the phase difference between the two is outputted to the phase comparison circuit 40.
Output from 0.

This phase error signal is supplied to the disk motor 4 via the disk servo circuit 41, and is also supplied to the capstan motor 5 via the capstan servo circuit 51, resulting in the pulse S and the vertical synchronization signal VF. The servo control is performed so that the time to' of the phase difference becomes the above-mentioned constant value tc, and tracking control is performed correctly.

The above are the tracking control methods that have been attempted in the past, but in reality, in the disk servo system during recording, changes in the load torque of the disk motor 4, power supply voltage fluctuations in the servo circuit system, changes in ambient temperature and humidity, or over time There is a problem in which the rotational speed of the disk motor 4 fluctuates due to changes, etc., and the time to of the phase difference between the pulse S and the recorded vertical synchronization signal VS essentially fluctuates, and therefore to is recorded in Fig. 3. It will be recorded with fluctuations with respect to a constant target value tc set at the time.

When the tape thus recorded is reproduced using the conventional tracking control device shown in FIG. 1, the time to' of the phase difference between the pulse S and the reproduced vertical synchronization signal VF is
In addition to true tracking errors, fluctuation errors that are unrelated to tracking errors and that correspond to the fluctuations in to at the time of recording are also detected.
The servo system treats the fluctuation error that corresponds to the fluctuation of as a tracking error and controls the servo system to maintain a constant value tc, which in turn causes a tracking error and also causes a large fluctuation in to during recording. In some cases, the control system deviates from the operating range and the tracking control cannot follow it, and the control system becomes unstable, such as hunting, and tracking control is no longer possible.

Furthermore, as a result of the tracking control, the control system is stabilized at a value where to' at the time of reproduction is different from the value of to at the time of recording, for example, a value equal to the target value tc, and the rotation of the rotary heads 21 and 22 is therefore stabilized. The speed will be different from that during recording, and this will cause deviations and fluctuations in the horizontal scanning frequency of the reproduced video signal. If the deviations and fluctuations are large, the synchronization pull-in range of the horizontal AFC circuit of the television receiver will be affected. There have been problems in which the horizontal synchronization of the receiver is disrupted due to deviation from the image quality, and in the case of color images, the luminance signal and color signal are temporally shifted, resulting in color shift, resulting in extremely unstable image reproduction.

An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art, and to achieve stable image reproduction by always performing stable and reliable tracking without being affected by fluctuations in the rotational speed of the rotary head during recording and reproduction. The object of the present invention is to provide a tracking control device that can perform the following tasks.

In order to achieve the above-mentioned object, the present invention provides for detection in synchronization with the rotation of a rotary head during recording.
An index signal synchronized with the DTP signal is formed, this index signal is multiplexed with the video signal to be recorded, and during playback, the rotational speed of the rotary head or the magnetic tape is determined based on the index signal separated from the playback video signal. Tracking control is performed by controlling the traveling speed of the vehicle.

Hereinafter, the case where the present invention is applied to a rotary two-head type VTR will be explained in detail with reference to an embodiment thereof. FIG. 4 is a diagram showing an embodiment of a servo control device for recording an index signal according to the present invention. Note that a part of the servo control device for recording can be the same as a part of the servo control device for reproduction shown in FIG. 1, so the common parts are given the same numbers. Since the functions and operations of the common parts are the same as those described in FIG. 1, detailed explanation thereof will be omitted.

In this FIG. 4, the capstan motor 5
is rotated at a predetermined constant speed by a capstan servo circuit 52, and the magnetic tape 1 is run at a constant speed.

On the other hand, the disk servo system related to the disk motor 4 receives the video signal to be recorded supplied via the terminal 100 in the same manner as described above, and the vertical synchronization separation circuit 1
The vertical synchronizing signal VS separated at 01 is down-done to 1/2 in frequency by the frequency down-down circuit 102 to obtain the vertical synchronizing signal VF of the frame period, and this vertical synchronizing signal VF and the pulse S from the pulse forming circuit 32 are combined. are compared in phase by a phase comparison circuit 40, and the rotational speed of the disk motor 4 is controlled so that the time to of the phase difference between the two becomes constant. 33 is a delay circuit which is triggered by the rising phase of the pulse S from the pulse forming circuit 32 and outputs a pulse P obtained by delaying the rising phase by a predetermined constant time t _R .

34 is an index signal forming circuit which forms an index signal I having a predetermined pulse width from the pulse P from the circuit 33 and outputs it to the terminal 200. This index signal I is a pulse synchronized with the pulse S and delayed by a time t _R from the rising phase of the pulse S.

FIG. 5 shows the waveforms and relative phase relationships of the vertical synchronizing signal VS, pulse S, pulse P, and index signal I described above.

In this Figure 5, the pulse S and the vertical synchronizing signal
The time t of the phase difference between VS varies depending on the rotational speed fluctuation of the disk motor 4, but the time _tR of the phase difference between the pulse S and the index signal I is completely unrelated to the rotational speed fluctuation of the disk motor 4. Always constant.

The index signal I thus formed is multiplexed with the video signal to be recorded in a video signal recording circuit (not shown) via the terminal 200, and then recorded on the magnetic tape 1 by the magnetic heads 21 and 22.

In the present invention, the format of the index signal is not limited to the above-mentioned pulse signal, but may be any signal format, and the multiplexing method thereof may be a method of directly multiplexing the video signal in the baseband, or a method of multiplexing the index signal with the video signal in the baseband, or modulating each other. A method of frequency multiplexing may also be used, and in any of these cases, the gist of the present invention is not departed from. In this embodiment, for the purpose of simplifying the circuit scale, the index signal I formed as described above is inserted and multiplexed within the vertical blanking period of the video signal to be recorded. The insertion position is adjusted by the delay time t _R of the circuit 33. For example, the delay time t _R is set to t _R >to, and the index signal is multiplexed at the position subsequent to the vertical synchronization signal within the vertical blanking period. Ru.

FIG. 6 is a diagram showing the pattern of the video track on the magnetic tape 1 recorded in this way.
As described in the figure, H1 and H2 are the scanning start points on the magnetic tape 1 of the magnetic heads 21 and 22, respectively, and S1 and S2 are the positions on each video track where the rising phase and falling phase of the pulse S are respectively. This point corresponds to .

_I1 indicates the recording position of _the index signal on the video track, and as is clear from the waveform diagram in FIG. S equivalent to ₁
At a point corresponding to a phase difference of a certain time t _R from the point,
It is always located on line F at a position on the tape a certain distance away from end A of magnetic tape 1, and the relative positional relationship between these is kept stable even if the rotational speed of disk motor 4 fluctuates during recording. It can be done.

Next, FIG. 7 is a diagram showing an embodiment of the tracking control device according to the present invention.

Note that a part of this tracking control device can be shared with a part of the servo control device during recording shown in FIG. 4, so the common parts are designated by the same numbers. Since the functions and operations of the common parts are exactly the same as those described in FIG. 4, detailed explanation thereof will be omitted.

In FIG. 7, reference numeral 43 denotes a reference signal generating circuit which generates a reference signal having a frequency approximately equal to the frame frequency of the video signal.

The pulse S from the pulse forming circuit 32 is phase-compared with the reference signal from the reference signal generation circuit 43 in a phase comparison circuit 42, and a phase error signal corresponding to the phase difference between the two is outputted from the phase comparison circuit 42. . This phase error signal is transmitted to the disk servo circuit 4.
1 to the disk motor 4, and as a result, the pulse S is servo-controlled so as to be phase synchronized with the reference signal.

On the other hand, a video signal reproduced from the magnetic tape 1 by the magnetic heads 21 and 22 and a video signal reproducing circuit (not shown) is supplied to an index signal separation circuit 61 via a terminal 300, and this circuit 61 outputs a reproduced video signal. As a result, the index signal I described in FIG. 4, which is multiplexed therewith, is separated.
The index signal I separated by this circuit 61
is compared in phase with the pulse S from the circuit 32 in the phase comparison circuit 60, and a phase error signal corresponding to the phase difference between the two is outputted from the circuit 60. This phase error signal is supplied to the capstan motor 5 via the capstan servo circuit 53.

As a result, servo control is performed so that the time t of the phase difference between the pulse S and the reproduction index signal I becomes the reference value t _R determined at the time of recording, and tracking is performed correctly.

However, as described in FIG. 6 above, the recording position _I1 of the index signal is at the point _S1 corresponding to the rising phase of the pulse S, completely independent of the rotational speed fluctuation of the disk motor 4 during recording. Since it is at a fixed position corresponding to a phase difference of a fixed time t _R , the time t of the phase difference between the pulse S detected by the circuit 60 and the reproduction index signal I during reproduction is a true tracking error, and The problem of tracking malfunction due to fluctuations in the rotational speed of the disk motor 4 during recording, as described in the conventional example of FIG. The fluctuation error of the phase difference in time t is extremely small, and
Since tracking errors do not occur, tracking control can always be performed stably and reliably.

In addition, in the disk servo system shown in Fig. 7,
Since the magnetic heads 21 and 22 are rotated at almost the same rotational speed as during recording, there is almost no deviation in the horizontal scanning frequency of the reproduced video signal, making it possible to perform stable image reproduction.

In the embodiment shown in FIG. 7, the reference signal generation circuit 43
However, FIG. 8 shows an embodiment in which the circuit configuration is simplified without using this. That is, in the embodiment of FIG. 8, the circuits 43 and 4 in FIG.
2 is omitted, and the phase error signal from the phase comparator circuit 60 is supplied to the disk servo circuit 41 instead.As in the case of FIG. 7, tracking control can be performed stably and correctly.

The embodiments shown in FIGS. 4, 7, and 8 are cases in which the present invention is applied to a rotating two-head type magnetic recording/reproducing device, but the present invention is not limited to this. It can be applied to a magnetic recording/reproducing device having any number of heads such as a head type or a four-head type, and the embodiment shown in FIG. However, the number is not limited to this, and the number may be arbitrary, such as multiplexing at a field period, and in any of these cases, the gist of the present invention is not departed from.

As described above, according to the present invention, in a rotary head type magnetic recording/reproducing device, even if the rotary head changes in rotational speed during recording and reproduction, tracking is always stable and accurate without being affected in any way. In addition, it is possible to perform stable and faithful image reproduction by making it difficult for deviations in the horizontal scanning frequency of the reproduced video signal to occur.

Furthermore, since the control head that has conventionally been commonly used for tracking control can be eliminated, the apparatus can be made smaller and lighter, and tape running can be stabilized.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a conventional tracking control device, FIGS. 2 and 3 are plan views showing track patterns of a conventional magnetic tape, and FIG.
The figure is a block diagram showing an embodiment of the servo control device during recording according to the present invention, FIGS. 5a to 5d are waveform diagrams of various parts thereof, and FIG. FIG. 7 is a block diagram showing one embodiment of the tracking control device according to the present invention, and FIG. 8 is a block diagram showing another embodiment of the tracking control device according to the present invention. 101... Vertical synchronization separation circuit, 102... Frequency down-down circuit, 40, 42, 60... Phase comparison circuit, 31... Phase adjustment circuit, 32... Pulse forming circuit, 33... Delay circuit, 34... Index signal forming circuit, 61... Index signal separation circuit, 43... Reference signal generation circuit, 4... Disk motor, 5... Capstan motor, 41... Disk servo circuit, 51, 52, 53... Car Pustan servo circuit, 2... disk, 21, 22
...magnetic head, 3...tack head, 1...magnetic tape.

Claims (1)

[Scope of Claims] 1. A pulse generator that generates a pulse signal synchronized with the rotation of the magnetic head in a magnetic recording and reproducing device that records and reproduces video signals on a magnetic tape using a rotating magnetic head; an index signal generator that forms an index signal synchronized with a pulse signal from the index signal generator; and a recording/reproducing device that multiplexes the index signal from the index signal generator with a video signal to be recorded, and records and reproduces the video signal using the magnetic head. an index signal separator that separates the index signal multiplexed thereon from the reproduced video signal from the recording and reproducing circuit; and an index signal separator that separates the index signal from the index signal separator and the pulse signal from the pulse generator. A phase comparator that compares phases and outputs a signal representing the phase difference; and a control circuit that causes the magnetic head to normally scan a recording track formed on the magnetic tape using the phase difference signal from the phase comparator. A tracking control device comprising: 2. Claim 1, characterized in that the recording circuit of the recording/reproducing circuit is configured to multiplex the index signal from the index signal generator during the vertical blanking period of the video signal to be recorded. tracking control device.