JPS61292254A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce remarkably a locking time from the transient state to the steady-state by detecting two kinds of levels in a pilot signal reproduced from an erasure head and using the result of detection to apply tracking control and switching the signal processing state of the tracking control. CONSTITUTION:A local pilot signal is superimposed on an output of a head 24 to extract f1, f3 components as 3fH component and f2, f4 components as 2fH component. When the local pilot signal is applied conversely in this case, the quantity of generation of both the 2fH component and the 3fH component is decreased. A switch 49 outputs alternately the f2, f4 components at the steady state and applies the result to a multiplier 34. When both the output of comparators 41, 42 are at L level, an output A is obtained from a logic circuit 44 and the transient state is discriminated, a one-shot multivibrator 52 is triggered attended with the output and a clock pulse is fed to a 1/2 frequency divider via an OR gate. Then the local pilot signal is switched between the f2 and f4 components and the state is locked momentarily to the state close to the steady state.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a recording/reproducing apparatus, and particularly to a recording/reproducing apparatus that records and reproduces information signals by cyclically superimposing pilot signals having four types of different frequencies on an information signal. It is.

(Summary of the Disclosure) This specification and drawings describe a recording and reproducing apparatus that records and reproduces information signals by cyclically superimposing pilot signals having four types of different frequencies. , is configured to detect two types of levels in the pilot signal reproduced by the erasing head whose width is approximately twice the track pitch, perform tracking control using these levels, and also switch the signal processing state of the tracking control. By doing this, it is possible to return the signal processing state of tracking control using the pilot signal to a steady state, which makes it possible to significantly shorten the transition time from a transient state to a steady state), and to quickly generate a good reproduction signal. This invention discloses a technique for obtaining a recording/reproducing device that can obtain -.

<Prior art> In recent years, in the field of high-density magnetic recording represented by video tape recorders (VTRs), pilot signals having four different frequencies are recorded superimposed on information signals, and during playback, A method of tracking using regenerated nine pilot signals has come to be used.

Hereinafter, conventional signal processing for forming a tracking control signal will be briefly described.

Figure 2 shows tracking using a 4-frequency method.”/TR
FIG. 3 is a block diagram showing a main part of a reproducing circuit for obtaining a tracking error signal.

In FIG. 2, numeral 1 indicates a magnetic tape, and arrow 2 indicates the direction in which the magnetic tape 1 is transported.

AI + B1 + A2 + B2 . . . are recording tracks recorded by heads A and B, respectively, which have sufficient azimuth angles to each other, and arrow 3 indicates the scanning direction of the heads. Recording track 4 contains four different frequencies (indicated by f1 to f4) along with the video signal.
Each pilot signal is sequentially recorded for each field (that is, for each track).

The recording order of pilot signals is the order shown in Figure 1,
For example, trough, riAo has f□2, for example, 102.5IO
(6.5 fH in z) Rack B□ has fz, for example 1
7.5 fH in 18.9KH2,) f3 for rack A2
For example, 10.5 fH in 165.2KHz,) rack B2 has f4, for example 148.7IO (9.5 in z)
A pilot signal of fH is superimposed on the video signal and recorded. (Note that fH indicates the frequency of the horizontal synchronizing signal.) As shown in the figure, the frequency difference between the pilot signals between adjacent recording tracks is fH or 3fH.

Then head or track Al (1-1, 2, 3...
), the frequency difference with the pilot signal of the adjacent track on the right side of the figure is always KfH, and the frequency difference with that on the left side is always 3fH. Also, the head or Bi (1
-1, 2, 3...) tracks, the frequency difference with the right adjacent track is always 3 fH, and the frequency difference with the left track is always K fH.

Incidentally, since the pilot signals f□ to f4 are all comparatively low frequency signals, even in azimuth recording, the head can reproduce the pilot signals from adjacent tracks other than the main scanning track as crosstalk. In other words, the pilot signal detected when the head is main-scanning track A2 is a composite signal containing 4" 2mf frequency components, and the center of the head's trace locus is precisely aligned with the center line of the main-scanning track. If they match (on-track), the pilot signals f2.f of the adjacent tracks are at the same level, and if the head slightly shifts from track A2 to the B2 side, f4 is larger than f2, and the head is on track. If the signal deviates slightly from A2 to the B1 side, f2 is reproduced more greatly than f4.

Therefore, the difference signal between the pilot signal on the main scanning track and each pilot signal on both adjacent tracks, that is, fH and 3fH
The direction and amount of deviation of the head from the main scanning track can be determined by taking out each signal separately and comparing the levels of the two difference signals.

Fig. 2 is a circuit block diagram of such a four-frequency system.
Only the pilot signal component is separated. The multiplier 8 multiplies the pilot signal component by the local pilot signal generated by the generating circuit 7. The local pilot signal l-i is a signal with the same frequency as the pilot signal recorded on the main scanning track, and as described in the explanation in FIG. 1, if track A2 is the main scanning track, the output of LPF6 is is f2. f4. The frequency of the local pilot signal including the f3 component is f3. Therefore, the output of multiplier 8 is f,
, f4. A signal having a frequency of the sum and difference of f, and f3 is output. The band pass filter (BPF) 9 is a circuit for extracting only the sum and difference signals υfH, and the BPFIO is a circuit for extracting only the 3fH signal), and these outputs are detected and rectified by the next-stage detection circuits 11 and 12, respectively.

Next, the fH signal component and the 3fH signal component are supplied to a level comparison circuit 13, which outputs a signal corresponding to the level difference between them. That is, when the reproduction level of the fH signal is higher than the reproduction level of the 3fH signal, a positive potential corresponding to the level difference is extracted, and in the opposite case, a negative potential is extracted. Since this button outputs a signal containing information on the amount and direction of the head's track deviation, this can be used as a tracking error signal.

Next, as explained in FIG. 1, if this continues, the relationship between track Ai and track B with the head deviation direction tracking error signal will be opposite to each other. It is necessary to provide a switching circuit 16 that selectively outputs what passes and what does not pass by the head switching signal 15.

<Problems to be Solved by the Invention> By the way, in a steady state, it is possible to reproduce a video signal while always performing good tracking as described above, but below we will consider tracking signal processing in a transient state. View. Now, when starting playback, the main scanning
Assuming that ν is A2 in FIG. 1 and the local pilot signal component to be multiplied at this time is fl, the fH acid component fa component is outputted from the detection circuits 11 and 12, respectively, as in the steady state. However, in this case, since the polarity is opposite to that in the steady state, tracking control is performed so that the playback head deviates further from track A2 in the direction in which it deviates.

Finally, the pilot signal recorded on the main scanning track and the local pilot signal come to match.

However, when the playback head is just tracking track A2, the fH component and the 3fH component are at approximately the same level, and when the playback head is shifted in either direction of arrow 2 or vice versa, the pilot of the main scanning track is It took a long time for the signal to match the local pilot signal. Therefore, there was a problem in that the reproduced image quality deteriorated during this period.

SUMMARY OF THE INVENTION In view of the problems typified by the above, an object of the present invention is to provide a recording and reproducing device that can quickly bring the tracking control to a steady state even in a transient state and quickly obtain a good reproduction signal. With the goal.

Means for Solving the Problems> In order to solve the above problems, the present invention uses an erase head whose trace direction is the same as that of the recording/reproduction head and whose width is approximately twice the track pitch. The system is configured to detect two types of levels in the pilot signal, use them to perform tracking control, and to also switch the signal processing state of the tracking control.

<Operation> By configuring as described above, it is possible to return the signal processing state of the tracking control using the pilot signal to the steady state, thereby making it possible to significantly shorten the time required to transition from the transient state to the steady state. became.

<Example> Hereinafter, an example in which the present invention is applied to a VTR as described above will be described in detail. Figure 1 is a diagram showing the schematic configuration of a VTR as an embodiment of the present invention;
5 is a diagram showing the head arrangement of the VTR of this embodiment, and FIG. 5 is a diagram showing the state of playback by the VTR of this embodiment.

In FIG. 4(2) and 4), reference numerals 21 and 22 indicate recording and reproducing heads, which are mounted on the rotating drum 23 with a phase difference of 180°. Further, 24 is an erasing head, which is attached with a phase difference of 90° with respect to the heads 21 and 22. Further, when the track pitch is Tp, the lower end is shifted by approximately 2.5 track pitches on the rotating drum. Accordingly, tracing is performed with a shift of three tracks during recording and reproduction. This is shown in FIG.

Next, the principle of steady state pull-in of tracking control in this embodiment will be explained. Recording/playback head 21.2
2 is superimposed on f□, f20, the rotating erasing head 24 moves f3.2 as shown in FIG. f
Trace the two superimposed tracks of 4. Also, on the contrary, the heads 21.22 are f3. While simultaneously tracing the superimposed tracks f, the rotary erasing head 24 simultaneously traces the two superimposed tracks fl and f2. This situation is shown in FIG.

If the head 21 is now in the position shown in FIG. 5, it can be seen that a tracking error signal can be obtained by comparing the f3 component and the f4 component that are output multiple times by the rotary erasing head 24.

Also, while the heads 21 and 22 are tracing the superimposed tracks of f3 and f4.

A tracking error signal can be obtained by comparing the f0 configuration and the f2 configuration in which multiple outputs are generated from the rotary erasing head. However, if all of these are detected and processed, the circuit scale will become large, so a local pilot signal as shown in FIG. 4 is superimposed on the output of the head 24. As a result, f□,
f3 component is 3fa component, f2. The f4 component can be extracted as a 2fH component.

At this time, if the local pilot signal is applied in the opposite manner, the amount of both the 2fH component and the 3fH component generated will be reduced. Determining this as an abnormal situation, the local Baylot signal is f2→
All you have to do is switch between f4. This allows cutting time to be shortened.

Hereinafter, the operation of the first part will be explained in order.

The signals reproduced by the recording/reproducing heads 21 and 22 are converted into a format compliant with television signals by the video signal processing circuit 31 and outputted from the terminal 32o. On the other hand, when recording, terminal 3
A video signal inputted from 21 is converted into a format suitable for a recording button by a circuit 31, and is recorded on a recording medium by a head 21.22.

During recording, the output signal of the erase signal generating circuit 36 is supplied to the head 24 as an erase signal. During reproduction, the Baylot signal component is separated from the output signal of the head 24 by the LPF 33, and is supplied to the multiplier 34,
The 2fH component from the output signal of the multiplier circuit 34 is multiplied by the local (Ilot signal) of 4.
The components are separated by a BPF 38, and then sent to a detection circuit 39.
The wave is detected at 40.・Compare the outputs of these detection circuits 39 and 40! 41 and 42 and compared with a reference voltage 43. The outputs of comparators 41, 42 are fed to logic circuit 44. Vref is set to be slightly smaller than the level of the pilot signal to be reproduced by 112 minutes.

If the outputs of the comparators 641 and 42 are both at high level 0, it is assumed that the track state is almost on track, and the capstan control circuit 45 is free-run by only speed control. Comparator 41
When the output of the comparator 42 is at a low level υ, the head is shifted in the opposite direction of the arrow 2, so the capstan phase is controlled in a direction that reduces the tape running speed. At this time, the illustrated C output is obtained from the logic circuit 44.

When the output of the comparator 41 is high and the output of the comparator 42 is H, a B output is obtained from the logic circuit 44, and the phase of the capstan is controlled to increase the running speed of the tape.

When the outputs of the comparators 41 and 42 are both 21, the logic circuit 44
More human output can be obtained and it can be determined that there is a transient state.

The one-shot multivibrator 52 is triggered by this output, and the clock signal is sent to the 14 frequency divider via the OR gate.
Supply Kurusu.

In a steady state, a one-cycle rectangular wave signal obtained from the rotation detector 48 of the rotating drum 23 is supplied to the edge detection circuit 50 for each rotation of the drum, and the output of this circuit 50 is used as the clock of the frequency division 453.・I feel tired. Accordingly, the switch 49 selectively switches f2. Outputs f4 and multiplier 3
Supply to 4. Therefore, when there is a human output of the logic circuit 44,
The local pilot signal switches between f, , f4, and it is possible to instantly enter a state close to a steady state.

In the above embodiment, the capstan control can also be performed by comparing the outputs of the detection circuit 39 and the detection circuit 40. In addition, the erasing head is further removed from the recording/reproducing head.
B if the layout is shifted by one track pitch.
The configuration is such that PF37 or fH and BPF38 separate the 2fH component.

<Description of Effects> As explained above, according to the present invention, it is possible to obtain a recording/reproducing device that can quickly return to a steady state even in a transient state of tracking control and can quickly obtain a good reproduction signal. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a VTR as an embodiment of the present invention, FIG. 2 is a diagram showing a recording pattern on a magnetic tape, and FIG.
The figure shows a conventional tracking signal processing circuit, Figure 4 (B) shows the head arrangement of the VTR shown in Figure 1, and Figure 5 shows the state of tape tracing by the VTR shown in Figure 1. , FIG. 6 is a timing chart for explaining the operation of the first part. 21.22 is a recording/reproducing head, 24 is an erase signal, 37.
38 is a band pass filter, 39.40 is a detection circuit, 4
5 is a capstan control circuit. 20th Punishment 3 troubles P6 Figure 6

Claims (1)

[Claims] A device for recording and reproducing information signals by cyclically superimposing pilot signals having four types of different frequencies on a track having a predetermined pitch, including a recording and reproducing head whose tracing direction is the same as that of the recording and reproducing head, an erasing head having a width approximately twice the track pitch; means for detecting two types of levels in the pilot signal reproduced by the erasing head; and means for performing tracking control using the output of the detection means; A recording/reproducing apparatus comprising means for switching a signal processing state of the tracking control means using the output of the detection means.