JPH0322645B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a tracking control circuit for a video disc or a video tape recorder (hereinafter simply referred to as a VTR), and in particular a tracking control circuit using a so-called pilot method using four predetermined pilot signals. This invention relates to a tracking control circuit.

BACKGROUND ART In a video disk or VTR, the track recorded on the recording medium such as a disk or tape, and the manufacturing and processing precision of the recording device etc. deviate from the designed center value. Particularly in VTRs, the tracks on the recording medium are curved in an S-shape due to the machining accuracy of the cylinder and uneven tension around the cylinder. Therefore, when reproducing a recording medium in this type of apparatus, it would be ideal if tracking could be performed automatically by moving the pickup or magnetic head that traces the track in the width direction of the track.

For this reason, several tracking control methods have been proposed for this type of device. Among them, a so-called pilot method using four types of pilot signals each having different predetermined frequencies has recently been proposed and is attracting attention.

This pilot method uses four types of pilot signals f ₁ ,
The frequency differences of f ₂ , f ₃ , and f ₄ are determined in the relationship shown in Figure 1 A and B, and the pilot signals f ₁ , f ₂ , f ₃ , and f ₄ are generated for each track. ...f ₁ , f ₂ ,
f ₃ , f ₄ . . . are sequentially switched and superimposed on the recorded signal and written onto the recording medium. Therefore, when a track on which the pilot signal f ₁ is written is played back, the pilot signals f ₂ and f ₄ recorded on the adjacent tracks on both sides will also be played back due to crosstalk. , the extracted pilot signals f _P in this case are f ₁ , f ₂ , and f ₄ . Therefore, when the extracted pilot signal f _P is mixed with the pilot signal f ₁ recorded on the playback track, the output will be |f ₂ ±f ₁ |, |f ₄ ±f ₁ |, |f ₁ ±f ₁
| appears, and if only the difference component is taken out, from the relationship shown in Figure 1 A and B, |f ₂ −f ₁ |=f _T1 , |f ₄ −f ₁ |=
f _T2 , |f ₁ −f ₁ |=0 is obtained. As a result, when a track shift occurs during reproduction, the amplitude of either f _T1 or f _T2 increases depending on the direction of the shift. For example, as shown in FIG. 2, suppose that a pick-up or magnetic head H is tracing a track in the direction of arrow A, and that this trace sequentially moves each track on the recording medium in the direction of arrow B. , four types of pilot signals f ₁ , f ₂ , f ₃ , f ₄ are sequentially transmitted to each truck... f ₁ , f ₂ ,
They are written in the order of f ₃ , f ₄ , etc. Therefore _, if the pick-up or magnetic _head H shifts as shown by
f _T1 becomes smaller than f _T2 . Therefore, if the pick-up or magnetic head H is moved in a direction perpendicular to the track or toward the recording medium so that the amplitudes of f _T1 and f _T2 are equal, the pick-up or magnetic head H becomes the first one. A normal tracking state can be maintained as shown by Z in Figure 2. For example, since a magnetic tape is used as a recording medium in a VTR, the running speed of this magnetic tape, that is, the capstan motor that runs the magnetic tape, is corrected to have the value of the amplitude difference between f _T1 and f _T2 mentioned above. Speed controlled by signal or
Alternatively, if the above-mentioned movement control for the magnetic head is performed, tracking will be automatically performed. In addition, since a disc is used as a recording medium for video discs,
In this case, tracking control cannot be performed even if the motor that rotates the disk is controlled. For this purpose, tracking adjustment is performed on video discs by moving the pickup in the radial direction of the disc.

By the way, in such a tracking control circuit using the pilot method, in order to obtain the frequency difference f _T1 and f _T2 shown in FIG. 1B, the pilot signal to be mixed with the reproduced extracted pilot signal f _P is It is necessary to switch for each track to correspond to a predetermined writing order, such as the pilot signal f ₁ for the track shown in FIG. 2 and the pilot signal f ₂ for the track. Therefore,
The magnitude relationship of the amplitudes of the frequency differences f _T1 and f _T2 with respect to the pick-up or displacement direction of the magnetic head H is 1
Since the amplitude difference value is reversed for each track, the correction signal having the above-mentioned amplitude difference value indicates which of the two magnetic heads H _A and H _B provided on the magnetic head drum is currently being traced. In response to the head switch signal SH, which is inverted for each track, the polarity is inverted for each track and then supplied to a speed control circuit such as a motor.

Here, in the tracking control circuit having the above configuration, the pilot signal f _P during recording is such that f ₁ and f ₃ are supplied to one magnetic head H _A , and f ₂ and f ₄ are supplied to the other magnetic head H _B. However, during playback, the magnetic heads H _A and H _B can only be distinguished by the head switch signal, and the pilot signals f ₁ and f ₃ of the pilot signal f _P recorded in the track currently being traced can be distinguished. Or you can't tell the difference between f ₂ and f ₄ . For this reason, when starting playback from a stop or a pause, the timing of the generation of the pilot signal to be mixed with the extracted pilot signal _fP in order to extract the frequency difference f _T1 and f _{T2 is} shifted. There are cases where f ₃ is mixed in with the required amount, and in this case tracking is controlled in a direction that is off. As a result, after the above-mentioned control in the off-direction is performed for two tracks, the extracted pilot signal f _P and the mixed pilot signal match and return to normal tracking control. If the matching time is long, the problem is that the reproduced image will be distorted.

DISCLOSURE OF THE INVENTION An object of the present invention is to provide a tracking control circuit that can instantaneously detect a mismatch in a pilot signal to be mixed with an extracted pilot signal, and can quickly change the generation of a mixed pilot signal generated for a matching ratio. It is to provide.

In order to achieve these objectives, the present invention has four
Seed pilot signals f ₁ to _{f 4} are sequentially transmitted for each track.
When playing back a recording medium that is repeatedly recorded in the order of f ₁ to _{f 4} , a pilot signal is included in the playback signal.
detecting that f ₁ and f ₂ or f ₃ and f ₄ are included at a predetermined level or higher and determining the pilot signal recorded on the playback track;
When the relationship between this determination result and the head switch signal deviates from a predetermined condition, the timing of the pilot signal generated from the pilot signal generation circuit is shifted to match the pilot signal recorded on the track being played back. This is to match the generated pilot signals.

Therefore, in the tracking control circuit configured in this way, even if the relationship between the reproduced pilot signal and the generated pilot signal deviates when starting playback from a stop or pause state, the pilot signal is generated according to the determination result. By shifting the timing, a pilot signal matching the pilot signal recorded on the playback track is generated.
This has an excellent effect in that the subsequent tracking adjustment is instantaneously performed and the period of disturbance in the playback screen at the start of playback is extremely short.

BEST MODE FOR CARRYING OUT THE INVENTION FIG. 3 is a block diagram showing one embodiment of a tracking control circuit according to the present invention. In the figure, reference numeral 1 indicates a magnetic tape as a recording medium.
This will be explained using an example applied to. 2 is a capstan shaft which is rotationally driven by a capstan motor 3 to run the magnetic tape 1 in the direction of the arrow; the rotation speed of the capstan motor 3 is controlled by a motor control circuit 4; controlled. Further, recorded signals are written onto the magnetic tape 1 by a pair of magnetic heads 5a and 5b. In this case, the pair of magnetic heads 5a and 5b are mounted at positions 180 degrees apart from each other on the circumference of a rotating cylinder (not shown). Since this rotating cylinder is rotated obliquely across the longitudinal direction of the magnetic tape 1 at high speed, the pair of magnetic heads 5a and 5b trace the magnetic tape 1 obliquely.
Here, a rotating cylinder (not shown) and a magnetic tape 1
The relationship between the running speed and the running speed is determined so that each of the pair of magnetic heads 5a, 5b completes one trace on the magnetic tape 1 in one revolution of the rotary cylinder. Therefore, the pair of magnetic heads 5
a and 5b are switched in accordance with the rotation of the rotary cylinder to alternately write recorded signals onto the magnetic tape 1. As a result, one rotation of the rotating cylinder produces 2
A recording track of a book is formed on the magnetic tape 1.
Here, 6 is a switch for switching the recording signal supplied to the magnetic heads 5a, 5b in accordance with the rotation of the above-mentioned rotary cylinder.

The above is an outline of a two-head VTR using a generally well-known helical scanning system, and since its details have already been made public, the details will be omitted here.

In the VTR constructed in this way, numeral 7 is a mode command circuit for instructing switching between recording mode R and reproduction mode P, and a changeover switch 8 is switched by the generated command signal. The command signal generated from the mode command circuit 7 is also supplied to the pilot signal generation circuit 9 to inform it of which mode is present. The pilot signal generating circuit 9 generates and outputs pilot signals f ₁ , f ₂ , f ₃ and f ₄ having the same frequency as the above-mentioned four types of pilot signals in a predetermined order for each track. This predetermined order means that in the recording mode R, the pilot signals f ₁ , f ₂ , f ₃ , f ₄ , f ₁ . . .
In playback mode P, f ₁ ,
The order of f ₂ , f ₃ , f ₄ , f _{1 . .} . or the generation of f ₃ , f ₄ , f ₁ , f _{2 . .} . shifted over two tracks can be switched. The pilot signals f ₁ , f ₂ , f ₃ , f ₄ are then supplied to the first mixing circuit 10 and the second mixing circuit 11. The first mixing circuit 10 mixes the video signal RF supplied from the outside with a pilot signal f ₁ ,
By superimposing f ₂ , f ₃ , and f ₄ , the signal is supplied to the recording amplifier 12 as a recorded signal. Therefore, the recorded signal output from the recording amplifier 12 is supplied to the R side terminal of the above-mentioned changeover switch 8. When the command signal supplied from the mode command circuit 7 indicates recording mode R, the changeover switch 8 switches the magnetic heads 5a, 5b selected by the switch 6.
Either one of them is connected to the R side terminal. Further, when the command signal indicates reproduction mode P, either one of the magnetic heads 5a, 5b selected by the switch 6 is connected to the P side terminal. Therefore, in recording mode R, the recorded signal generated from the recording amplifier 12 is supplied to either one of the pair of magnetic heads 5a, 5b via the changeover switch 8 in accordance with the switching operation of the switch 6. Ru. In the reproduction mode P, reproduction signals alternately reproduced by the pair of magnetic heads 5a and 5b are supplied to the reproduction amplifier 13 via the switch 6 and the changeover switch 8. The reproduction signal output from this reproduction amplifier 13 is supplied as a video signal RF to a well-known video signal processing system, and
It is also supplied to a low pass filter 14.

Here, the relationship between the video signal RF constituting the reproduced signal and the pilot signals f ₁ , f ₂ , f ₃ , f ₄ is as follows:
While RF is generally several MHz, the pilot signal is set at approximately several 100 MHz so as not to affect the video signal RF. Therefore, only the pilot signals f ₁ , f ₂ , f ₃ , and f ₄ are extracted from the low-pass filter 15 as extracted pilot signals. Then, this extracted pilot signal is mixed with the pilot signals f ₁ , f ₂ , f ₃ , f ₄ supplied from the pilot signal generation circuit 9 in the second mixing circuit 11, so that
A beat component of a mixed two-frequency wave including two frequency differences f _T1 and f _T2 of constant frequencies shown in FIG. 1B described above and |f ₃ −f ₁ | or |f ₄ −f ₂ | is generated. This beat component is the first component that passes only the frequency difference f _T1 .
The signal is supplied to a bandpass filter 15 and a second bandpass filter 16 that passes only the frequency difference f _T2 . The frequency difference f _T1 that has passed through the first band pass filter 15 is detected in the first detection circuit 17, and the frequency difference f _T2 that has passed through the second band pass filter 16 is detected in the second detection circuit 18. Detected. Therefore, this first and second detection circuit 1
The levels of the output signals 7 and 18 are determined according to the amplitudes of the frequency differences f _T1 and f _T2 that are respectively input. The output signals of the first and second detection circuits 17 and 18 generated in this way are supplied to a comparator 19 constituted by a differential amplifier, and are set to a certain standard according to the level difference between the two input signals. Outputs a tracking control signal that changes around the value. That is, if the traces of the magnetic heads 5a and 5b are shifted in the width direction of the track,
As mentioned above, the frequency difference f _T1 ,
There is a magnitude relationship in the amplitude of f _T2 . As a result, the comparator 19 generates a tracking control signal that increases or decreases from a constant reference value depending on the direction of deviation. In this case, since the amount of change in the tracking control signal changes according to the difference between the two input levels in the comparator 19, this amount of change ultimately represents the difference in amplitude between the frequency differences f _T1 and f _T2 . Then,
This indicates the amount of tracking deviation. Furthermore, when no tracking error occurs, the level difference between the two input signals of the comparator 19 is zero, so that the generated tracking control signal is output as a signal having a constant reference value. The tracking control signal generated in this manner is inverted in polarity in an inverting amplifier 20, and then sent to an analog switch 21 controlled by a head switch signal SH.
At the output of comparator 19 or inverting amplifier 2
One of the tracking control signals of the zero outputs is selected and supplied to the motor control circuit 4.

Therefore, the motor control circuit 4 controls the rotational speed of the capstan motor 3 in accordance with the tracking control signal generated in this way to correct the tracking deviation.

On the other hand, 22 is an extraction pilot signal detection circuit for detecting pilot signals f ₁ and f ₂ of a predetermined level or higher contained in the reproduced signal, and extracts f from the reproduced pilot signal output from the filter 14. A bandpass filter 23 extracts only ₁ or _f2 , a detector 24 detects the output signal of this bandpass filter 23, and a pilot signal detection signal PD when the output signal level of this detector 24 exceeds a reference value Vr. and a comparator 25 for controlling switching of the generation order of the generated pilot signals to the pilot signal generating circuit 9. In other words, this extraction pilot signal detection circuit detects the reproduction of the track on which the pilot signals f ₁ and f ₂ are recorded by detecting the extraction pilot signals f ₁ and f ₂ at a level exceeding the reference value Vr. That means you are doing it.

Next, the extraction pilot signal generation circuit 9 includes an oscillation circuit 91 and a frequency dividing circuit 9, as shown in FIG.
2, a switch circuit 93, a waveform converter 94, and a switch control circuit 95.
The oscillation circuit 91 generates a reference clock signal of a predetermined frequency in synchronization with the horizontal synchronization signal HD included in the video signal RF. The oscillation circuit 91 that performs such an operation is, for example, a voltage controlled oscillator 91.
1, a phase difference detection circuit 912, and a frequency dividing circuit 913
and a low-pass filter 914. The reference clock pulse generated from the reference oscillation circuit 91 is transmitted to the frequency dividing circuit 92.
By dividing the frequency at the output terminal O ₁ as the aforementioned four pilot signals f ₁ , f ₂ , f ₃ , f _4
.about.O4 are individually output as rectangular waves, and are supplied in parallel to the input ports _P1 to _P4 of the switch circuit 93, respectively. The switch circuit 93 selects one of the four pilot signals f ₁ , f ₂ , f ₃ , f ₄ by selection control signals e ₁ to e ₄ supplied to the input ports P ₁₁ to P ₁₄ from the switch control circuit 95, respectively. Select one type and output. The selected type of pilot signal is supplied to the waveform converter 94, where it is first integrated and converted into a triangular wave, and then converted into a positive waveform by a well-known polygonal function generator or the like and output. .

On the other hand, the switch control circuit 95
4 kinds of pilot signals f ₁ , f ₂ , f ₃ , f ₄ for 3
Selection control signal e ₁ to select one type from among
Generate e ₄ . And this switch control circuit 9
5 is a frequency dividing circuit 951 that divides the frequency of the head switch signal SH by two, and an output signal X of this frequency dividing circuit 951.
and the pilot signal detection signal PD supplied from the extraction pilot detection circuit 22, and the exclusive OR circuit 95.
AND gate 953 for determining the coincidence between the output of 2 and the command signal R/P generated from the mode command circuit 7
An exclusive OR circuit 954 receives the output signal of the AND gate 953 and the output signal of the frequency divider circuit 951, and inputs the head switch signal SH and the output signal Y to the lower input terminal A and the upper input terminal B, respectively. , performs binary-decimal conversion 2
Hex-decimal decoder (hereinafter referred to as decoder) 955
It is composed of:

In the circuit configured as described above, when the mode command circuit 7 is set to the recording mode, the command signal R/P becomes "L", the switching circuit 8 selects the terminal R, and the pilot signal is generated. The AND gate 953 shown in FIG. 4 of the circuit 9 is closed and its output signal continues to be in the "L" state. Next, when the 15C/S head switch signal SH shown in FIG. 5a is supplied, the frequency dividing circuit 951 shown in FIG. occurs. In this case, since the output signal of the AND gate 953 continues to be in the "L" state, the output signal Y of the exclusive OR circuit 954 is output to the frequency dividing circuit as shown in FIG. 5c. 95
It becomes the same as the output signal X of 1. Since the input/output relationship of the decoder 955 is determined as shown in FIG. 6, the input signals SH, shown in FIGS. 5a and 5b,
For X, selection control signals are repeatedly generated from the output terminals O ₁ to O ₄ in the order of e ₁ , e ₂ , e ₃ , e ₄ , e _{1 .} . . and supplied to the switch circuit 93. switch circuit 9
3, the types of pilot signals to be selectively outputted for the selection control signals _e1 to _e4 are determined as shown in FIG. Therefore, in this case, the pilot signals f ₁ , f ₂ , f ₃ , f ₄ , f ₁ . . . are output from the pilot signal generation circuit 9.
will be output repeatedly in sequence. The pilot signal generated in this way is mixed with the video signal RF supplied from an external device such as a camera in the first mixing circuit 10, and is further amplified in the recording amplifier 12 before being sent to the switching circuit. The data are recorded on the magnetic tape 1 alternately by the magnetic heads 5a and 5b via the magnetic head 8. In this case, since the head switch signal SH is generated in synchronization with the switching of the switch 6, the pilot signals _f1 to _f4 are sequentially repeated on each track on the magnetic tape 1. It will be recorded.

Next, in the playback mode, the mode command circuit 7
Since the command signal P generated from the input signal becomes "H", the AND gate 953 shown in FIG. 4 opens and supplies the output signal of the exclusive OR circuit 952 to the exclusive OR circuit 954. Switching circuit 8
selects terminal P.

On the other hand, one of the pair of magnetic heads 5a, 5b traces one track in which pilot signals are recorded in the order of f ₁ , f ₂ , f ₃ , f ₄ as shown in FIG. If so, the low-pass filter 14 outputs the extracted pilot signal.
f ₁ and f ₂ due to crosstalk from adjacent tracks.
f ₄ is output and supplied to the second mixing circuit 11.

In this case, the bandpass filter 23 constituting the extraction pilot signal detection circuit 22 detects and outputs the extraction pilot signal f ₂ , and after this output signal is detected in the detection circuit 24 , the comparator 25
If it is determined that the signal exceeds the reference value Vr,
The pilot signal detection signal PD is set to "H" and is supplied to the pilot signal generation circuit 9. In other words, the extraction pilot signal detection circuit 22 detects the pilot signal
When reproducing a track on which f ₁ and f ₂ are written, a pilot signal detection signal PD of "H" level is generated, and the relationship between the recorded pilot signal and the pilot signal detection signal PD is as shown in Fig. 7. Become. In this case, if the extracted pilot signal and the generated pilot signal match, the pilot signal detection signal PD and the frequency dividing circuit 95 are connected as shown in FIG.
The output signals X of 1 match. If these two signals match, the exclusive OR circuit 95
The output signal Z of No. 2 continues to be held at "L" as shown in FIG. Since this "L" signal is supplied to the exclusive OR circuit 954 via the AND gate 953, the output signal X of the frequency dividing circuit 951 is
An output signal Y similar to
and the pilot signal f ₁ shown in FIG.
Continue to run the control to cause ~f ₄ to occur repeatedly.

Also, at the start of playback, due to some factor, the pilot signal generation circuit 9 is shifted by two tracks to generate the pilot signal _f3 or _f4 with respect to the extracted pilot signal _f1 or _f2 . In this case, the pilot signal detection signal PD generated from the extraction pilot detection circuit 22 and the output signal X generated from the frequency dividing circuit 951 do not match, and the output signal Z of the exclusive OR circuit 951 becomes as shown in FIG. As shown, it becomes "H". As a result, exclusive OR circuit 9
54 inverts the phase of the output signal X of the frequency dividing circuit 951 and outputs the output signal Y' shown in FIG.
Supply to 5. In this case, since the decoder 951 uses the output signal Y' as the upper input of the 2-bit input, the generation of the selection control signal is e ₁ ,
The order of occurrence is shifted from the order of e ₂ , e ₃ .e ₄ , e _{1 . .} . to the order of e ₃ , e ₄ , e ₁ , e 2 . Therefore, the pilot signals generated from the pilot signal generation circuit 9 in the order of f ₁ , f ₂ , f ₃ , f ₄ , f _{1 .} . . are sent to the exclusive OR circuit 95.
2 detects the track deviation and sets the output signal Z to “H”
, the generated pilot signal is shifted by two steps to become f ₃ , f ₄ , f ₁ , f ₂ , f _{3 .} . . , so as to match the extracted pilot signal. Then, when a mismatch occurs again between the extracted pilot signal and the generated pilot signal, the exclusive OR circuit 952
The output signal Z of is inverted to "L", and the frequency dividing circuit 95
By supplying the output signal Y having the same phase as the output signal X of 1 to the decoder, the generation order of the pilot signals is again shifted by two steps, thereby matching the generated pilot signal to the extracted pilot signal. If such an operation is illustrated in a diagram, it will be as shown in FIG.

Next, one of the pair of magnetic heads 5a and 5b tracing the recording track records pilot signals f ₁ , f ₂ , f ₃ , and f ₄ in the order shown in FIG. Assuming that one track is being traced, the low-pass filter 14 outputs f ₁ as an extraction pilot signal, and f ₄ and f ₂ due to crosstalk from adjacent tracks, which are supplied to the second mixing circuit 11 . In this case, as described above, the pilot signal generation circuit 9 automatically generates a pilot signal that matches the pilot signal recorded in the track in the trace that has the highest level among the extracted pilot signals. During tracing, a pilot signal _f1 is generated and supplied to the second mixing circuit 11, where it is mixed with the extracted pilot signal _f1 . Therefore, the output of the second mixing circuit 11 is |f ₄ ±f ₁ |, |f ₂ ±f ₁ |,
|f ₁ ±f ₁ |. This output signal is shown in FIG.
As explained earlier using B, it is a mixed two-frequency beat component including a predetermined constant frequency frequency difference f _T1 and f T2, and is a beat component of a mixed two-frequency wave including a frequency difference f T1 and f _T2 of a predetermined constant frequency, and is a beat component of a mixed two-frequency wave including a frequency difference f T1 and f T2 of a predetermined constant frequency. In , the above f _T1 = |f ₂ −
Only f ₁ | and f _T2 = |f ₄ −f ₁ | are extracted.

At this time, if the pair of magnetic heads 5a and 5b are not shifted in the width direction of the track, the magnitudes of f _T1 and f _T2 become f _T1 = f _T2 , and as mentioned above, the comparator 19 A signal having a certain reference value is sent to the motor control circuit 4 via an analog switch 21.
The rotation of the motor 3 is maintained as it is by supplying the tracking control signal to the tracking control signal.

Next, if the magnetic head 5a or 5b shifts to the next adjacent track side, the above-mentioned crosstalk becomes f ₄ < f ₂ , so the above-mentioned frequency difference f _T1 , f _T2
becomes f _T1 < f _T2 . Therefore, the comparator 19 generates an output having a value that is either greater or less than the above-mentioned fixed reference value. Also,
If the magnetic head 5a or 5b shifts to the previous adjacent track (unmarked) side, the above-mentioned crosstalk will occur.
Since f ₄ > f ₂ , the above-mentioned frequency difference f _T1 and f _T2
becomes f _T1 < f _T2 . Therefore, the comparator 22 generates a correction signal having a value that is opposite to the above-mentioned deviation to correct the track deviation.

Next, if the magnetic head 5a or 5b traces the next trace, the low-pass filter 14 outputs f2 as an extraction pilot signal and _f1 and f3 as crosstalk between adjacent tracks, and outputs _f1 and _f3 as an extraction pilot signal to the second mixing circuit 11. supplied to In this case, since the pilot signal generating circuit 9 generates the pilot signal f ₂ and supplies it to the second mixing circuit 11 as described above, the output of the second mixing circuit 11 is |
f ₂ ±f ₁ |, |f ₂ ±f ₂ |, |f ₃ ±f ₂ |. As a result, the first and second low pass filters 15, 16
takes out |f ₂ -f ₁ |=f _T1 and |f ₃ -f ₂ |=f _T2 , respectively, and supplies them to the comparator 19 via the first and second detection circuits 17 and 18. At this time, the magnetic head 5a
Alternatively, if there is no deviation in 5b, a signal containing the same reference value as in the case described above is generated from the comparator 19, and this is supplied to the motor control circuit 4 as a tracking control signal.

Here, if the magnetic head 5a or 5b shifts to the next adjacent track side, the above-mentioned crosstalk f ₁ and f ₂ will be f ₁ < f ₃ , so the above-mentioned frequency difference f _T1 and f _T2 will be f _T1 < f _T2 . Therefore, the output of the comparator 19 in this direction of deviation becomes a tracking control signal in the opposite direction to the direction of deviation in the case of tracing the track described above.
In order to solve this inconvenience, switch 2
1 is switched for each track by the head switch signal SH, the output signal of the comparator 19 and the output signal of this comparator 19 are switched to the inverting amplifier 20.
The signal whose polarity has been inverted by being inverted and amplified is taken out via the switch 21 which is switched by the head switching signal SH, so that a tracking control signal with matched polarity can be taken out.

In the above embodiment, a case has been described in which the extraction pilot signal detection circuit is configured to detect recording tracks of f ₁ and f ₂ , but it is configured to detect recording tracks of f ₃ and f ₄ . Needless to say, it may be configured.

As explained above, according to the tracking control circuit having the above configuration, the pilot signal generated to obtain a beat with the pilot signal recorded on the adjacent track is different from the reproduced pilot signal of the track currently being traced. Since it is possible to immediately identify this and instantly match the generated pilot signal to the reproduced pilot signal, the tracking settling time is extremely short, and as a result, when stopping or starting playback from a pause, The period during which the reproduced image is disturbed becomes extremely short.

Furthermore, in the present invention, the extracted pilot signal detection circuit detects whether the pilot signal recorded on the own track being reproduced is either f ₁ , f ₂ or f ₃ , f ₄ . The circuit configuration can be relatively simplified.

[Brief explanation of drawings]

Figure 1A is a spectrum diagram showing an example of the frequency array of the 4-frequency pilot system, Figure 1B is a diagram showing the relationship between the four frequencies and the beat component of their difference, and Figure 2 is a diagram showing the recording track and magnetic field on the recording medium. FIG. 3 is a circuit diagram showing an embodiment of the tracking control circuit according to the present invention; FIG. 4 is a circuit diagram showing an example of the pilot signal generation circuit in FIG. 3. , Figure 5 a-d
6 is a diagram showing the waveforms of various parts and the relationship between input and output for explaining the operation of the circuit shown in FIG. 4, and FIG. 7 is a diagram showing the relationship between the extracted pilot signal and the generated pilot signal. DESCRIPTION OF SYMBOLS 1... Magnetic tape (recording medium), 2... Capstan, 3... Motor, 4... Motor control circuit, 5a, 5b... Magnetic head, 6... Switch, 7... Mode command circuit, 8... ...Selector switch, 9...Pilot signal generation circuit, 10,1
1... First and second mixing circuits, 12... Recording amplifier, 13... Playback amplifier, 14... Low pass filter, 15, 16... First to fourth band pass filters, 17, 18... First ~Second detection circuit, 19
... Comparator, 20 ... Inverting amplifier, 21 ... Switch, 22 ... Extraction pilot signal detection circuit, 2
3...Band pass filter, 24...Detection circuit,
25... Comparator.

Claims (1)

[Claims] 1. Four types of pilot signals f ₁ , f ₂ , f ₃ , having predetermined frequencies different from those of the recorded signal;
One type of f ₄ is written for each track, and the writing order of each pilot signal f ₁ , f ₂ , f ₃ , f ₄ is repeated for each track in the order from f ₁ to f ₄ . By sequentially tracing each of the tracks one by one on the recorded recording medium, the recorded signal of the track is detected;
An extracted pilot signal including a pilot signal of any one of the self-tracks among the pilot signals f ₁ , f ₂ , f ₃ , f ₄ and a pilot signal of the crosstalk component due to this trace is reproduced, and A frequency difference between a pilot signal of an adjacent track and a pilot signal of the self-track obtained by shifting the position toward one of the adjacent tracks is detected, and this frequency difference is detected as a difference in frequency between the pilot signal of the adjacent track and the pilot signal of the self-track. It is predetermined to have two types of constant frequencies, one for when the trace position shifts to the other track side, and one when the trace position shifts to the other track side.By detecting the type and amount of this constant frequency, the shift of the trace position can be detected. A tracking control circuit that detects and corrects tracking deviations detects that f ₁ , f ₂ or f ₃ , f ₄ in the extracted pilot signal included in the reproduced signal exceeds a predetermined level. If the pilot signal recorded on the self-track being played back is f ₁ , f ₂ or
An extraction pilot signal detection circuit detects whether or not f 3 and f ₄ and generates a pilot signal detection signal _, and normally extracts the pilot signal from the recording track in the order of f ₁ , f ₂ , f ₃ , and f ₄ . The generation timing of the pilot signal, which is generated in synchronization with the reproduction of the magnetic head and which is generated when the relationship between the pilot signal detection signal and the head switch signal for selecting two magnetic heads deviates from a predetermined relationship, is two-track. 1. A tracking control circuit comprising: a pilot signal generating circuit that transitions over a period of minutes.