JPS61292255A - Recording and reproducing device - Google Patents

Abstract

PURPOSE:To reduce remarkably the locking time from the transient state to the stationary state by switching the signal processing state of tracking control based on the level of a specific pilot signal component reproduced from an erasure head. CONSTITUTION:An f1 component of a reproduced signal from an erasure head 24 outputted via the position P of a switch 45 is compared with a reference voltage 48 by a comparator 49 via a band pass filter 47 and a detection circuit 50 at the reproduction. When an output of the detection circuit 50 exceeds a Vref, the output of the comparator 49 goes to an H level. When the output of a 1/2 frequency divider 42 is at an H level and a switch 43 is at the position of a f1 oscillator 34, it represents a faulty state, an output of an AND gate 44 goes to H, a one-shot multivibrator 52 is triggered to invert an output of the 1/2 frequency divider 42. The switch 43 outputs a f3. Then the reproducer head traces before and after a track superimposed with the f3 signal, then the tracking control is locked quickly to the stationary state there after.

Description

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

<Summary of the Disclosure> The present specification and drawings describe a device for recording and reproducing information signals by cyclically superimposing pilot signals having four types of different frequencies on an information signal, in which tracking is performed using the reproducing output of a recording/reproducing head. 1. In the transient state of the tracking control, the signal processing state of the tracking control is switched based on the level of a specific pilot signal reproduced by the erasing head whose trace direction is the same as that of the recording/reproducing head. The present invention discloses a technique for obtaining a recording/reproducing device that can quickly bring the device into a steady state and quickly obtain a good reproduction signal.

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

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

Figure 942 shows a VTR that uses four-frequency tracking.
FIG. 3 is a block diagram showing the main parts 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. A1゜B engineering + A2tB
1t... are recording tracks recorded by heads A and B, each having a predetermined azimuth angle with respect to each other, and arrow 3 indicates the scanning direction of the heads. In the recording track 4, pilot signals of four different frequencies (indicated by f-f4) are recorded in IIC sequence for each field (that is, for each track) together with the video signal.

The recording order of the pilot signals is as shown in Figure 1.
For example, track A has f for example 102, 5KH
6.5 f H in z.

1 1' Track B has f For example, 118, 9KE (7 in z
．． 5 f H.

1 2+ Track A has f For example, 165, 2KHz
Medium 10.5fH.

2 3' Track B2 has f42, for example 9 of 148.7 KHz.
．． A pilot signal of 5fH is superimposed on the video signal and recorded. (Note that fH indicates the frequency of the horizontal synchronizing signal.) The frequency difference between the pilot signals between adjacent recording tracks is fH or 3fa, as shown in the figure.

Then head or track Ai (i -1, 2, 3,...
...), the frequency difference with the pilot signal of the adjacent track on the right side of the figure is always fH, and the frequency difference with that on the left side is always 3fH. Also, the head or Bi
(L■1.2.3...) When scanning a track, the frequency difference with the adjacent track on the right is always K3
If it is fH, the frequency difference with that on the left side will always be fH.

Furthermore, since the pilot signals f□ to f are both relatively 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. . That is, the pilot signal detected when the head is main scanning track A2 is f4. If the center of the trace trajectory of the head exactly coincides with the center line of the main scanning track (on-track), the pilot signal f2.f3 of the adjacent track is used. If f are at the same level and the head slightly shifts from track A2 to the B2 side, f4 will be larger than f2, and the head will move toward track A2.
If it does not fall or shifts to the KH2 side, f2 is reproduced larger 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.

Figure 2 is a circuit block diagram of such a four-frequency system.

In the figure, a reproduced signal in which a video signal and a pilot signal are superimposed is input from terminal 5, and a low-pass filter (L
Only the pilot signal component is separated by PF)6. A multiplier 8 multiplies the pilot signal component by the local pilot signal generated by the generation circuit 7. The local pilot signal is a signal having the same frequency as the pilot signal recorded on the main scanning track, and as described in the explanation of FIG. 941, if track A is the main scanning track, the output of the LPF 6 is f2. The frequency of the local pilot signal including f, , f3 components is f3. Therefore, the output of multiplier 8 is f2.
A signal having a frequency of the sum and difference of f, , f3 and f3 is output. The band pass filter (BPF) 9 is a circuit that extracts only the 1H and 3fH signals from the sum and difference signals, and these outputs are detected and rectified by the next-stage detection circuits 11 and 12, respectively. Ru.

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.

As a result, a signal containing information on the amount and direction of the head's track deviation is output, so this can be used as a tracking error signal.

Next, as explained in FIG. 1, if this continues, the relationship between track A and track Bi in 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 using the head switching signal 15.

<Problems to be Solved by the Invention> By the way, as mentioned above, in a steady state, video signals can be played back while always performing good tracking. Let's consider it. Now, when the main scanning track is A2 in FIG. 1 at the start of playback, and the local pilot signal component to be multiplied at this time is fl, the f Each of the 3fH components is output. However, in this case, since the polarity is opposite to that in the steady state, tracking control is performed so that the playback head is further shifted in the direction in which it is shifted from track A2.

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

However, when the playback head just trunks to track A2, the fH acid component 3 is at approximately the same level as the fH component, and when the playback head is shifted in either direction of arrow 2 or vice versa, the pilot of the main scanning track 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.

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

Means for Solving the Problems> In order to solve the above problems, tracking control is performed using the playback output of the recording/playback head, and reproduction is performed by an erasing head whose tracing direction is the same as that of the recording/playback head. The level of a specific pilot signal component is detected, and the signal processing state of tracking control is switched based on the detected level.

By configuring as described above, the signal processing state of the tracking control using the pilot signal can be returned to the steady state, and as a result, it is possible to significantly shorten the transition time from the transient state to the steady state. Ta.

<Example> Hereinafter, an example in which the present invention is applied to the above-mentioned VTR will be described in detail.

FIG. 1 is a diagram showing a schematic configuration of a VTR as an embodiment of the present invention, FIG. 4 is a diagram showing a head configuration of a VTR of this embodiment, and FIG. FIG. 3 is a diagram showing how a recording medium is traced.

As shown in FIG. 4, the head configuration is a recording/reproducing head 21.2.
2 are mounted on the rotating cylinder 20 with a phase difference of 180°, and the rotating erase head 24 is mounted with a phase difference of 90° on these heads 21,22. It is assumed that the head width of the erasing head 24 is approximately twice the recording track width.

Further, arrow 23 indicates the direction of rotation of each head.

Here, the rotating erasing head must trace the track recorded before the recording/reproducing head 21, 22. For example, when the head 21 is at the position shown in FIG. It is placed in the position shown in the figure. In this case, the main scanning track of the playback head 21 is A.
If it is set to 1, the head 24 starts tracing in the latter half of the scan, and the main scanning track of the reproducing head 22 becomes B1, and the post-tracing ends.

During this period, a reproduced pilot signal of frequency f0 is obtained from the rotating erasing head 24, and the arrangement is such that there is no reproduced pilot signal. On the other hand, when the main scanning track of the head 21 is A2 and the main scanning track of the head 22 is B2, the reproduced output of the head 24 contains many f1 configurations.

Therefore, in this embodiment, when the track on which f□ or f2 is recorded is the main scanning track, when the f1 component is reproduced by the rotary erasing head 24, it is determined that there is an abnormality.

Hereinafter, the operation of the section shown in FIG. 1 will be explained using the timing chart shown in FIG. 6. In FIG. 1, the numbering used in FIGS. 3 and 4 is used.

The recording and reproducing heads 21 and 22 are video signal processing circuits 32
The video signal input from 331 is recorded, and the reproduced video signal is output from 330.

40 in the figure detects 200 rotations of the rotating drum, and 1 rotation is 1 rotation.
This is a rotation detector that outputs a rectangular wave (H8W) with a period, and the output of this 2 controls the head switch 31. The output of the head switch 31 undergoes tracking signal processing in a circuit with an LPF of 6 or less, and a tracking control signal is obtained from the differential amplifier 13. However, in this case, it is supplied to the capstan control circuit 36 without going through an inverting amplifier, and the above-mentioned H8W is used to control the output of the differential amplifier 13 when fl and f3 are the main pilot signals of the scanning track. I am trying to use it. Furthermore, the local pilot signal is used as a local pilot signal, and is configured to be selectively supplied to the multiplier 8 by a switch 43.

Reference numeral 42 denotes a frequency divider for frequency dividing H8W by % using the output of the edge detector 51, and a switch 43 is switched based on the output of this frequency divider. Therefore, as shown in FIG. 6, fl is used as the local pilot signal when the main scanning track is f and f2, and f3 is used as the local pilot signal when the main scanning track is f3 and f4.

When the output of the frequency divider RA 42 is at a high level, the switch 43 supplies the output from the f□ oscillator 34 to the multiplier 8,
When the D-level is υ, the output from the 13 oscillator 34 is applied to the multiplier 8.
shall be supplied to Therefore, the output of the frequency divider 42 becomes H.
In this case, if the output of the rotary erasing head 24 contains a large amount of the f1 component, it can be seen that there is an abnormal situation.

The switch 45 is for recording/reproducing switching, and is for switching between head 2 and
According to 1.22, it is connected to the R side when recording is being performed, and to the P side when reproduction is being performed. During recording, the erase signal output by the erase signal generator 46 is supplied to the head 24, and the head 24 performs an erase operation. On the other hand, during playback, f of the playback signal output via the P side of the switch 45.
□ Acid component is separated by a band pass filter (BPF) 47. The output of the BPF 47 is detected by a detection circuit 50, and this detection output is a reference (Vref) voltage 48.
and is compared by a comparator 49. When the output of the detection circuit 50 exceeds Vref, the output of the comparator 49 becomes H, and as described above, if the output of the % frequency divider 42 is H at this time, an abnormal situation occurs. At this time, the output of the AND gate 44 becomes H, which triggers the shift multiplier 52 and becomes the clock input of the I frequency divider 42. Therefore, the output of the % frequency divider 42 is inverted,
The switch 43 is configured to output f3. At this time, the playback head should be tracing the front and back of the track on which f3 is superimposed, so the tracking control can be quickly brought back to a steady state.

In the above-described embodiment, even during tracking transitions such as at the start of playback, it is possible to quickly return to a steady state.

In the above configuration, when the pilot signal of the main scanning track is f□ or f2, the rotating erase head
An abnormal state is assumed when a large number of .

Also, the tracking control method is the same as before. '
It is also possible to use a well-known method of generating a local pilot signal at the top of the rotation of l'3*f4. At this time, f1→f3. f2→f4゜f3→f□
, by switching the local pilot signal from f4 to f2, it became possible to quickly enter a steady state.

<Effects of the Invention> As explained above, according to the present invention, the temperature state of tracking control can be quickly brought to a steady state, and an extremely good reproduction signal can be obtained even at the start of reproduction. A reproduction device is obtained.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a schematic configuration of an embodiment in which the present invention is applied to a VTR, Figure 2 is a diagram showing a recording pattern on a magnetic tape, Figure @3 is a diagram for explaining tracking signal processing, vg4 The figure shows the head arrangement of the VTR shown in Fig. 1, Fig. 5 shows the state of tape tracing by the VTR shown in Fig. 1, and Fig. 6 shows the timing for explaining the operation of the first doctor's section. It is a chart. In the figure, 21 and 22 are recording/reproducing heads, 24 is a rotary erasing head, 41 is an OR gate, 42 is a frequency divider, 43 is a switch, 44 is an AND gate, 47 is a bandpass filter,
48 is a reference voltage, 49 is a comparator, 50 is a detection circuit, 51 is an edge detection circuit, and 52 is a one-shot multivibrator. ￥Z diagram No. 30 No. 6 (I8

Claims (1)

[Claims] A device for recording and reproducing by cyclically superimposing pilot signals having four different frequencies on an information signal, the device comprising: a recording/reproducing head; an erasing head having the same trace direction as the recording/reproducing head; and the recording/reproducing head. means for performing tracking control using the pilot signal reproduced by the erasing head; and means for detecting the level of a specific pilot signal component reproduced by the erasing head and switching the signal processing state of the tracking control means based on the detected level. A recording and reproducing device comprising: