JPS6231056A - Information signal reproducing device - Google Patents

Abstract

PURPOSE:To shorten the control lead-in time of tracking by detecting the differential frequency component between a reference signal whose frequency is equal to that of a pilot signal and a pilot signal that a head in reproducing operation reproduces. CONSTITUTION:Frequency detecting circuits 8 and 9 detect the differential frequency component between the reference signal whose frequency is equal to that of the pilot signal recorded on an object track by one of a couple of playback heads A and B, i.e. one head other than the other head in reproducing operation and the pilot signal reproduced by the playback head and the reference signal by which the output of the head to be traced next through a multiplier 5 is selected according to the contents of the detected differential frequency component. Consequently, the leading-in time of servocontrol is shortened.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an information signal reproducing device, and in particular, a pair of reproducing heads from a recording track in which a plurality of different pilot signals are cyclically recorded together with an information signal for each track. The present invention relates to an apparatus for reproducing the information signal using sequentially the information signals.

[Conventional technology]

Fig. 2 is a block diagram showing a tracking control method in a conventional device using a so-called 4-frequency system, and Figs. 3, 4, and 5 are for explaining the conventional tracking control method. FIG.

2 and 5, 1 is a head switching circuit, 2 is a pilot signal detection circuit, 3 is a magnetic tape, 4 is a track, 5 is a multiplier, 6 is a reference signal generation switching circuit, and 7 is a pilot signal generator. , 8 and 9 are first and second difference frequency detection circuits, 10.11 is a direct current conversion circuit, 12 is a differential amplifier, 13
14 is an inverter circuit, 14 is a switching circuit, and A and B are magnetic heads (hereinafter referred to as "Hered").

In the apparatus configured as described above, output signals from the reproduction heads A and B are passed through a head switching circuit and a pilot signal detection circuit 2 having a low-pass filter configuration to extract only the pilot signal component.

The pilot signals are distributed on the tape 3 at different frequencies f,
, f2. Four signals, fs and f4, are sequentially recorded together with the video signal by tape running and head scanning, and during playback, the head width is set to be slightly wider than the recording track. , D trace.

Looking at the relationship between the head and track during playback, the third
As shown at position 4a in the figure, when the track currently being played back is correctly tracked, not only the fl pilot signal recorded on the playback track, but also the adjacent pilot signal from the adjacent track. f4 and f2 are also detected. In contrast, the dashed line position 4b in the figure
, 4c, when the head is shifted to the right or left with respect to the relevant track, in addition to the main pilot signal f8, only one of the adjacent pilot signals, that is, only f2 and only f4 is reproduced. become.

However, for example, the frequencies f, - of four types of pilot signals
f, as shown in Figure 3, is (+) f, -f2 =ΔfA=fa (If)f
, -f4==Δf B=3f H(fll)fs -f
4 =ΔfAtefH(fV)fs-fz=Δf B=3
fH However, fH is set to be the horizontal scanning frequency.

Therefore, the reproduced pilot signals f, , f from the adjacent tracks are reproduced at the same level as fI of the reproduced pilot signal when the head is tracing correctly (position 4a), so that f.

−f4=ΔfB and f and −f2=ΔfA are detected as equal values. Further, when the vehicle is off-track on a certain placement plate as indicated by the broken line positions 4b and 4c, the pilot signal of one adjacent track is not detected. That is, in the case of 4b, f
Knee f2 = ΔfA only, fl-f4 = Δf in case of 4c
Only B.

Head) The obtained reproduced signal has the above content and is applied to the pilot signal detection circuit 2 having a low-pass filter configuration, and the reproduced pilot signal is input to the multiplier 5.
A local pilot signal from a reference signal generation switching circuit 6 is applied to the multiplier 5 as another input.

The reference signal generation switching circuit 6 switches four pilot frequency outputs of frequencies f1 to f4 generated by the pilot signal generator 7 between high level and low level every 1/60 seconds in synchronization with the rotation of the rotating drum. Switching is controlled based on a head switching signal (hereinafter referred to as 30PG).

Incidentally, during recording, this local pilot signal is also used as the aforementioned recording pilot signal sent to the video head.

By multiplying the regenerated pilot signal obtained at the output end of the pilot signal detection circuit 2 in this way by the local pilot signal that is switched for each head trace, the frequency components contained in the regenerated pilot signal and the local pilot signal are Obtain a multiplication output containing signal components with frequencies that are the difference between the frequencies of . This multiplication output is the first and second difference frequencies (Δf
A and ΔfB) are applied to detection circuits 8 and 9. This first
, the second difference frequency detection circuits 8 and 9 each extract the signal component of the difference frequency ΔfA+ΔfB, and further convert it into direct current in the subsequent stage DC converting circuits 10 and 11 each consisting of a rectifier circuit. 12 is input. That is, when the head is in a state where there is no tracking deviation as in position 4a, the difference signal of the pilot signals is ΔfA
and ΔfB are at the same level, the output of the differential amplifier 12 is 0.
It is.

On the other hand, in the state of position 4b shifted to the right, ΔfA is output but ΔfB is not output, so the differential amplifier 1
The output of 2 outputs a positive voltage, and conversely the output of 4C shifted to the left.
In this state, although ΔfB is output, ΔfA is not output, so the output of the differential amplifier 12 is a negative voltage. As a result, the output of the differential amplifier 12 changes depending on the deviation from the track traced by the head, and positive and negative signals are also output in the direction of the deviation, so the head changes depending on the tracking error voltage. It is only necessary to control the relative position of the tape, and since the direction of the tracking error voltage changes for each field, the inverting amplifier 13 in the next stage
The switching circuit 14 is switched and outputted for each track.

In the 4-frequency method, as shown in FIG. 6, point T is in a correct tracking state. Turn the head in the L direction,
, 'I', , T, and the tendency of the tracking error signal is shown in FIG.

FIG. 5 shows the relationship between the head position and the tracking error signal when the head moves to each point on the track 6. In the figure, point T. At T, which is the center of the adjacent track, the error voltage becomes 0, and at T, which is the center of the adjacent track, the error voltage becomes maximum in the direction of fA, and at point T2, it becomes Q again.
Returning again, at point T, when the maximum value is reached in the ΔfB direction, when the pilot signal reaches the fourth track, that is, the track fl, it is in a state of correct tracking and the error voltage becomes O. The cycle ends. [Problems to be Solved by the Invention] As is clear from the above, there are points where the error voltage becomes 0 in addition to the point T0 where correct tracking is performed. That is, in the four-frequency system, there is no problem at all in the vicinity of the on-tock, but when the control range is expanded, it can be seen that there are pseudo-stable points in addition to stable points.

This pseudo-stable point causes a problem in that the control lock-in time (lock-in time), especially at the time of start-up, becomes long.

The present invention has been made to solve such problems, and an object of the present invention is to provide an information signal reproducing device that can shorten the tracking control pull-in period.

[Failure to solve the problem]

In the apparatus according to the present invention, during a period when one of a pair of playback heads is busy on a track to be controlled by the other head, a reference signal having the same frequency as a recorded pilot signal is sent to the head being played back. Detect the difference frequency component from the pilot signal being reproduced, determine the frequency of the subsequent reference signal according to the content of the detected difference frequency component, and perform tracking using the corresponding 7 allens signals and the reproduced pilot signal. It is designed to perform control.

[For production]

In the above configuration, the content of the difference frequency component between the pilot signal being reproduced in a pair of reproduction heads and the pilot signal recorded in the track to be controlled by the other head is By suggesting the closest track to be controlled by the head and determining the frequency of subsequent reference signals based on this, the control lead-in time can be shortened.

〔Example〕

FIG. 1 shows a circuit diagram showing the main structure of an embodiment of the present invention.
15 is the input terminal for the playback start signal, 1
6 is a polarity determination circuit for determining the polarity of the tracking error voltage, and 17 is a local piezo signal switching control circuit which receives the polarity determination circuit 16 as an input. The embodiment shown in FIG. 1 can be performed by microcomputer/control, and FIG. 6 shows a flowchart when microcomputer control is performed. In FIG. 1, the same reference numerals as in FIG. 2 indicate the same or corresponding parts.

In the tracking control device configured as described above, which head is tracing is detected in the first field based on the signal from the 30PG. If head A is currently tracing, this first
The field is set by the local pilot signal switching control circuit 17 to a pilot signal fz that is not recorded in the track controlled by head A (recorded in the track controlled by head B). Therefore, the signal of frequency f2 is multiplied by the multiplier 5 to detect the error voltage. That is, when the head A is currently at position 4aK, the main component of the reproduced pilot signal is f, so a large signal of 1f knee fzl = ΔfA is output. Moreover, when the pilot signal f8 is reproduced as shown at position 4d in FIG. 3, a large signal of 1-f, 1=4 fB is output. This corresponds to head A in FIG.
When is within the track deviation range of T-1 to T1, the ΔfA signal tends to be increased, and when it is within the track deviation range of T, to T, the ΔfB signal tends to be outputted to a large extent.

When ΔfA is output, it is assumed that head A exists near the track where the pilot signal of frequency fl is recorded, and the local pilot signal of head B in the next track, that is, the second field, is of frequency f2. Just choose it as a signal. Conversely, when outputting 1ΔfB, it is assumed that head A exists near the track where the pilot signal of frequency f1 is recorded, and head B on the next track outputs the frequency f as a local pilot signal.
All you have to do is choose signal number 4.

Similarly, when the first field is head B, instead of the local pilot signal recorded on the track to be controlled by head B, a signal having a frequency of, for example, f is supplied to the multiplication circuit 5, As described in the case of head A, the tracking error voltage is determined by the polarity determination circuit 16, and in the next field, the local pilot signal to be multiplied by the output pilot signal of head A is selected as the f or fl signal. It is something to do.

Similarly, the frequency of the local pilot signal that head A first multiplies during playback is f2, and the frequency of the local pilot signal that head B multiplies first during playback is fl, but f4. It is also possible to multiply by f.

In this case, the occurrence rate of ΔfA7Δ, fB is f2. Since it is the opposite of when multiplied by fl, the frequency of the local pilot signal to be multiplied from the next field onwards is also f2 and f,
, f, and fl, respectively.

〔Effect of the invention〕

As described above, the present invention is such that the other head of a pair of playback heads reproduces a reference signal having the same frequency as the pilot signal recorded on the track to be controlled. Since a means is provided to detect the difference frequency component with the pilot signal and select a reference signal to be multiplied by the output of the head to be traced next according to the content of the detected difference frequency component, the servo pull-in time can be reduced. This makes it possible to obtain an information signal reproducing device that can be significantly speeded up.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main part configuration of an information signal reproducing device as an embodiment of the present invention, FIG. 2 is a block diagram showing a tracking control method in a conventional device, and FIG. 3 is a block diagram showing a conventional tracking control method. Diagram 4 for explaining the control method
The figure shows the arrangement of pilot signal frequencies, Figure 5 shows the tendency of tracking error voltage when the head is moved condylarly on the tape, and Figure 6 shows the example of Figure 1 controlled by a microcomputer. This is a flowchart when the process is performed. In the figure, 1 is a head switching circuit, 2 is a pilot signal detection circuit, 3 is a magnetic tape, 4 is a track, 5 is a multiplier, 6 is a reference signal generation switching circuit, 7 is a pilot signal generator, 8.9 is each 1st. second difference frequency detection circuit, 10
．． 11 is a DC conversion circuit, 12 is a differential amplifier 6. 13 is an inverting amplifier, 14 is a switching circuit, 15 is an input terminal, 1
6 is a polarity determination circuit, 17 is a local pilot signal switching control circuit, and A and B are magnetic heads. Agent Patent attorney 1) Kitatake Haruichi Katsurai-L- L-Kiichi Ichigo---Figure 6

Claims (1)

[Claims] In a device that sequentially uses a pair of reproducing heads to reproduce an information signal from a recording track in which a plurality of pilot signals having different frequencies are sequentially and cyclically recorded along with an information signal for each track, one of the pair of reproducing heads Detecting a difference frequency component between a reference signal having the same frequency as a pilot signal recorded on a track to be controlled by the other head during playback and a pilot signal being played back by the head being played back; An information signal reproducing device characterized in that the frequency of a subsequent reference signal is determined according to the content of a difference frequency component, and tracking control is performed using this reference signal and a reproduced pilot signal.