JPH06103555B2 - Tracking controller - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention will be described in the following order.

A Industrial field of use B Outline of the invention C Conventional technology D Problems to be solved by the invention E Means for solving the problems (Fig. 1) F Action G Example G ₁ Configuration of tracking control device ( FIG. 1) Operation of G ₂ tracking control device (FIGS. 2 and 3) H Effect of the invention A Industrial field of application The present invention is formed on a recording medium in order so as to cross the traveling direction. Automatic track tracking that records pilot signals of different frequencies together with video signals on recording tracks, detects the frequencies of pilot signals reproduced from adjacent tracks during reproduction, and tracks the reproduction head to a predetermined track. The present invention relates to a tracking control device applied to a system (hereinafter referred to as ATF system).

B. SUMMARY OF THE INVENTION The present invention is a tracking control device applied to the ATF system, in which a reference pilot signal is switched in synchronization with a head switching cycle at the time of high-speed reproduction, and a waviness of a tracking error signal becomes ± 90 °. A sample-hold circuit that samples and holds this tracking error signal is provided, and the oscillation point of the tracking loop is detected based on the tracking error signal sampled and held by this sample-hold circuit. This can be done in time, and the stability of the reproduced image can be easily achieved in a short time.

C Conventional Technology Conventionally, as a tracking device for a video tape recorder, there is one called an ATF system which has been put to practical use in 8 mm video and the like. An example of this ATF type tracking control device will be described below.

As a tracking control device of this ATF system, a 4-frequency system in which pilot signals of four frequencies are sequentially recorded on a recording track has been proposed. However, the tracking state is determined by the relationship between the tracking error signal and the tracking error signal. If it shows, it will become like FIG.
That is, considering the case where the track pitch and the head width are almost equal, the error signal S3 is 0 at the phase lock point T0.
The reproducing head is controlled to the correct tracking state at this time. On the other hand, if the reproducing head causes tracking deviation in the positive direction, the tracking deviation amount increases with a positive inclination until it reaches one track pitch, that is, the adjacent track T1. The amount of increase takes the maximum value on the track T1, and thereafter the error signal S3 decreases with a negative inclination during the range in which the tracking deviation increases by two track pitches (range T1 to T3), and the position of the track T2 decreases. Becomes 0 and then becomes a negative value. This development has a negative minimum value at the track T3 position, and when the tracking deviation amount exceeds this position T3, the error signal again increases with a positive inclination for two track pitches, and finally the error signal at the position T4. It becomes 0. Thus, the change of the error signal is 1 during the track pitch tracking deviation T0 to T4.
If a change in cycle occurs and the tracking deviation increases thereafter, the cycle for every four track pitches is repeated.

In response to such a change in the error signal, the tracking control system controls the reproducing head so that the tracking position shift amount decreases as the error signal increases in the positive direction at the lock position T0, or the error signal decreases in the negative direction. If so, the reproducing head is controlled so as to reduce the tracking deviation amount. Therefore, the reproducing head is locked at the phase position T0 where the error signal becomes zero. On the other hand, at the phase position T2, the error signal becomes 0, but if the error signal increases slightly from the phase point T2 in the positive direction or decreases in the negative direction, the tracking deviation amount increases. It cannot be a stable point because the reproducing head is controlled (this is called an oscillation point).

As an ATF type tracking control device for generating an error signal which changes in this way, the ones shown in FIGS. 5 to 7 have been proposed in principle.

That is, as shown in FIG. 5, this tracking control device receives a signal S1 which is a part of the reproduction output of a rotary video head as a recording / reproducing head in a pilot signal detecting circuit (1) having a low-pass filter structure and a magnetic tape as a recording medium. Create a playback pilot signal S2 whose component is the playback output of the pilot signal recorded in
S2 is given to the error signal forming circuit (3). The error signal forming circuit (3) sends out the tracking error signal S3 (FIG. 4) formed under the control of the reference signal generating circuit (4).

On the tape (5), as shown in FIG. 6, integers having different frequencies, for example, four kinds of pilot signals f ₁ , f ₂ , f ₃ , f ₄
Of the four video tracks T1, T2, T3, T4 recorded together with the video signal are obliquely closely formed so as to be cyclically repeated. Recording / playback head (6)
The effective width of the video head that constitutes
The value is selected to be almost equal to the width of T4, so that when the reproducing head (6) is correctly tracking the track currently being reproduced and scanned (this is called a reproducing track) as shown by the solid line in FIG. By reproducing only the pilot signal recorded on the track, the number of pilot frequency components included in the reproduction output becomes one. On the other hand, as shown by the broken line, the head (6) shifts to the right or When it is in the left shift state, the pilot signal recorded on the track adjacent to the right side or the left side of the reproduction track is also reproduced, so that the pilot frequency component included in the reproduction output becomes two kinds and each pilot frequency component The size should be the same as the facing length of the playback head that faces the corresponding track. To have.

However, the frequencies f _{1 to} f ₄ of the four types of pilot signals are selected in the lower band of the color components converted to the low frequency range (600 to 700 [KHz]), and are odd numbers in the four circulating tracks T1 to T4. The frequency difference with the pilot signal of the right track is Δf _A and the frequency difference with the pilot signal of the left track is Δf _B centering on the second track T1, T3, and the even number With respect to the tracks T2 and T4, the frequency difference with the pilot signal of the right track is Δf _B , and the frequency difference with the pilot signal of the left track is Δf _A.

Therefore, when the head (6) is reproducing the odd-numbered tracks T1 and T3, if there is a signal component with a frequency difference Δf _A as the frequency component of the pilot signal included in the reproduction signal, the head (6) is in the right shift state. If there is a signal component with a frequency difference of Δf _B , it can be seen that the head (6) is in a left-shifted state, and if there is no signal component with a frequency difference of Δf _A and Δf _B , the tracking is performed correctly. I know that it is done.

Similarly, when the head (6) is reproducing the even-numbered tracks T2, T4, if there is a signal component with a frequency difference Δf _B as the frequency component of the pilot signal included in the reproduction signal, the head (6) moves to the right. It can be seen that the head (6) is in the left shift state if there is a signal component with a frequency difference of Δf _A.

In the case of this embodiment, the first, second, third and fourth tracks
T1, T2, T3, the frequency f ₁ which is assigned to _{T4, f 2, f 3,} f 4 is
f ₁ = 102 [kHz], f ₂ = 116 [kHz], f ₃ = 160 [kHz], f ₄ = 1
46 [kHz], therefore the difference frequencies Δf _A and Δf
_B is Δf _A = | f ₁ −f ₂ | = | f ₃ −f ₄ | = 14 [kHz] (1) Δf _B = | f ₂ −f ₃ | = | f ₄ −f ₁ | = 44 [kHz] --- Selected in (2).

The reproduction signal S1 having such contents obtained from the head (6) is given to the pilot signal detection circuit (1) having a low-pass filter configuration, and the reproduction pilot signal S2 obtained by extracting the pilot signal included in the reproduction signal S1 is generated. It is given to the multiplication circuit (14) as a first multiplication input. The reference pilot signal S11 of the reference signal generation circuit (4) is applied to the multiplication circuit (14) as a second multiplication input.

The reference signal generator circuit (4) is a pilot signal generator circuit (1) that generates four types of pilot frequency outputs of frequencies f _{1 to} f _4.
6) and a head switching pulse RF-SW (FIG. 7A) that changes the logic level each time the tape scanning head of the two video heads is switched in association with the circuit drum (not shown). And a switch circuit (17). In the case of this embodiment, the switch circuit (17) is a head switching pulse RF.
It has a quaternary counter circuit that counts each time the level of -SW changes, so that the gate signals corresponding to the first to fourth tracks T1 to T4 can be sequentially repeated from this counter circuit. Gates are opened by the gate signals of the tracks T1 to T4, and as shown in FIG. 7B, the pilot frequency f _{1 of the} pilot signal generating circuit (16)
The outputs of ~ f ₄ are sequentially transmitted as the reference pilot signal S11.

The reference pilot signal S11 obtained at the output end of the switch circuit (17) is sent to the video head (6) as a recording pilot signal S4 via the signal line (18) during recording, and thus the video head (6) is It has been made so as to record given to each track T1~T4 sequentially video heads (6) a pilot signal of frequency f ₁ ~f ₄ corresponding while scanning the fourth track T1~T4 .

In this way, the reproduced pilot signal S2 obtained at the output end of the pilot signal detection circuit (1) while the head (6) scans the first to fourth tracks T1 to T4, respectively.
By multiplying the reference pilot signal S11 generated in synchronization with the reproduction track, to the frequency component included in the reproduction pilot signal S2 when there is a track error,
A multiplication calculation force S12 including a signal component having a frequency different from the frequency of the reference pilot signal S11 is obtained (actually, the multiplication calculation force S12 also includes other signal components such as a sum frequency component). This multiplication calculation force S12 is applied to the first and second difference frequency detection circuits (20) and (21) each composed of a bandpass filter. The first difference frequency detection circuit (20) extracts the signal component of the difference frequency Δf _A based on the above formula (1) when the multiplication calculation force S12 contains it, and extracts it to extract the direct current conversion circuit (22 ) To obtain a first DC level error detection signal S13. Similarly, the second difference frequency detection circuit (21) extracts the signal component of the difference frequency Δf _B based on the above equation (2) from the multiplication calculation force S12, and extracts the signal component to make the direct current conversion circuit (23 ) To obtain the second error detection signal S14.

Here, when the head (6) is trying to track the first, second, third, and fourth tracks T1, T2, T3, T4 (thus, the stitch circuit (17) causes each track as shown in FIG. 7B). At the timing corresponding to T1, T2, T3, T4, the frequency is f ₁ ,
When f _2, f _3, and transmits the reference pilot signal S11 f ₄₎ are shifted to the right, shown in Fig. 7 C1 to reproduction pilot signal S2 obtained based on the reproduction signal S1 of the head (6) As described above, the pilot signals of the frequencies f ₁ and f ₂ , f ₂ and f ₃ , f ₃ and f ₄ , f ₄ and f ₁ are included, and as the multiplication calculation force S12,
As shown in Figure D1, the difference frequency Δf _A (= f _{1 to} f ₂ ), Δf
_{B (= f 2 ~f 3)} , Δf A (= f 3 ~f 4), Δf B (= f 4 ~f 1)
A signal sequentially containing On the other hand, head (6)
Is shifted to the left, the reproduced pilot signal S2 is shown in FIG. 7C2.
Sequential frequencies f ₄ and f ₁ , f ₁ and f ₂ , f ₂ and f ₃ , f ₃
And the pilot signal of f ₄ is included, and accordingly, the multiplication calculation force S12 is set to the difference frequency Δf _B (= f
_{4 to} f ₁ ), Δf _A (= f _{1 to} f ₂ ), Δf _B (= f _{2 to} f ₃ ), Δf _A
(= F _{3 to} f ₄ ) are sequentially included.

Thus, as shown in FIGS. 7E and 7F (for example, showing a right shift state), the first and second error detection signals S13 and S13 in which the DC level rises from 0 every time the head (6) switches the track to be scanned. S14 can be obtained from the DC conversion circuits (22) and (23).

The first and second error detection signals S13 and S14 are given to the subtraction circuit (24) as an addition input and a subtraction input, respectively, so that the first and second error detection signals S13 and S14 are generated as shown in FIG. 7G. A subtraction output S15 that changes in an alternating manner each time it is obtained alternately is obtained. The subtraction output S15 is directly applied to the first input terminal a1 of the changeover switch circuit (25) and the polarity thereof is inverted in the inverting circuit (26) and applied to the second input terminal a2. The changeover switch circuit (25) performs a changeover operation to the first input terminal a1 side by the head changeover pulse RF-SW when the head (6) scans the odd-numbered tracks T1 and T3, while the changeover circuit is an even-numbered track. When scanning the tracks T2, T4, the switching operation to the second input end a2 is performed, and thus, when the head (6) is in the right shift state as shown in FIG. 7H, a positive electrode having a size corresponding to the right shift amount. Direct current level output
S16 is obtained (on the contrary, the DC level output S16 has a magnitude corresponding to the left shift amount and has a negative polarity in the left shift state), and this is output through the output amplifier circuit (27) which is a DC amplifier. And is output as a tracking error signal S3. By the way, if the head (6) is displaced to the right, for example,
When the reproduction tracks are odd-numbered T1 and T3, a signal component of the difference frequency Δf _A appears at the output end of the multiplication circuit (14), so that the output from the first difference frequency detection circuit (20) side is subtracted from the subtraction circuit (24). ), And since the changeover switch circuit (25) is changed over to the side of the first input terminal a1 at this time, it outputs the tracking error signal S3 of a positive DC level. On the other hand, when the reproduction tracks are even-numbered T2 and T4, the signal component of the difference frequency Δf _B appears at the output end of the multiplication circuit (14), so that the output from the second difference frequency detection circuit (21) side It is given to the subtraction circuit (24), and at this time, the changeover switch circuit (25) is switched to the second input terminal a2 side, so the negative output of the subtraction circuit (24) is inverted by the inversion circuit (26). Then, the tracking error signal S3 having a positive DC level is transmitted.

Therefore, if this tracking error signal S3 is used as a correction signal in the phase servo circuit of the capstan servo loop, correction is made so that the tape running speed is slowed when the tape is positive, and is increased when the tape is negative, the video head and the reproduction track are The phase shift can be corrected and thus the correct ATF tracking servo can be realized.

In the above-mentioned principle configuration, the principle has been described on the assumption that no difference frequency component is generated at the output terminal of the multiplication circuit (14) when the head (6) correctly tracks each track.
Actually, even in this tracking state, the pilot signals of the tracks adjacent to the left and right sides are generated in the reproduction signal S1 of the head.

That is, in practice, when a card band is not provided between tracks during recording, the tracks to be newly recorded in the recording mode are sequentially recorded so as to partially overlap the already recorded tracks. Therefore, in this case, the width of the head (6) is larger than the width of each of the tracks T1 to T4, so that the head (6) sticks out to the tracks adjacent to the left side and the right side when correctly tracked. Therefore, since the head (6) reproduces the pilot signals of the tracks adjacent to the left side and the right side, the error detection signals S13 and S14 (Fig. 6E) corresponding to the signal component of the difference frequency having a size corresponding to the protruding length are shown. And F) are generated from the DC conversion circuits (22) and (23).

When the guard band is provided, the width of the head (6) is almost equal to the width of the track, but the pilot signals recorded on the tracks adjacent to the left and right sides are reproduced as crosstalk signals by the head (6). It gets mixed in the signal. Therefore, the error detection signals S13 and S14 include the signal component of the difference frequency corresponding to the crosstalk signal.

However, the pilot signal mixed in the reproduction output S1 of the head (6) from the adjacent track in this way is multiplied by the multiplication circuit (14).
The error detection signals S13 and S14 cancel each other when they are subtracted from each other in the subtraction circuit (24), because they are simultaneously generated as signal components of the difference frequencies Δf _A and Δf _B at the output terminal of the. Moreover, when the head (6) is tracking correctly, the head (6) is located symmetrically with respect to the tracks adjacent to the left side and the right side, so that the protruding lengths of the head (6) are substantially equal to each other on the left and right sides. The magnitude of crosstalk is almost the same for the left and right sides, and eventually the calculation output S15
Is equivalent to the above case where the width of the head (6) is considered to be almost equal to the width of the track. Therefore, the tracking operation of the tracking control device is performed because the head width is larger than the track width or due to crosstalk. There is no adverse effect of the difference frequency component that occurs simultaneously from the two tracks on the same side.

In the error signal forming circuit (3) described above, the signal components of the difference frequencies Δf _A and Δf _B of the pilot signals of the reproduced track and its adjacent track are obtained, and the error detection signals S13 and S14 are obtained based on this signal component. was so Alternatively, the level of the reproduced pilot signal frequency f ₁ ~f ₄ detected by the reproduction pilot signal detecting circuit of each band-pass filter configuration, to obtain an error detection signal S13 and S14 on the basis of the detection output You may do it.

Considering the timing at which the reference pilot signal S11 of FIG. 7B transmits the pilot signal of the frequency f _{1 in} the above configuration, for example, the phase lock position T 0 (fourth In the state shown in the figure), the content of the reproduced pilot signal S2 is the frequency f ₁ , so that the output S12 of the multiplication circuit (14) does not include any of the difference frequencies Δf _A and Δf _B. When the reproducing head causes tracking deviation in this direction from this state, the reproducing head (6) comes to face the track T2, so that a component of frequency f ₂ is generated in the reproducing pilot signal S2 and it depends on the tracking deviation amount. As the area facing the track T2 gradually increases and then passes by and gradually decreases, the frequency f ₂ component also gradually increases and decreases through the maximum value, so the output of the multiplication circuit (14) The difference frequency component Δf _{A of} S12 is the phase position T0 to T
As it goes through 1 to the T2 position, it gradually increases and then decreases through the maximum value. Accordingly, the value of the error signal S3 correspondingly increases in the positive direction and decreases through the maximum value, which is shown in FIG.

Eventually reproducing head (6) of the frequency components f ₄ toward the T4 position through the T3 position from the generated frequency components f ₄ and head T2 located in a reproduced pilot signal S2 becomes to face the track T4 Since the size gradually increases and decreases through the maximum value, the multiplication circuit (1
The frequency component of Δf _B is generated at the output S12 of 4), and thus the error signal S3 is transmitted from the points T2 to T3 as described above with reference to FIG.
As it goes through T4, it decreases in the negative direction and increases through the minimum value.

In this way, in the four-frequency FTF type tracking control device, there is one lock position for four tracks, which means, for example, the time until the servo control device enters the lock state at the time of rising (that is, the lock position). It means that the intime) is quite large. By the way, the control signal (CTL signal) is recorded along with the tape feed direction by a fixed head in the past by recording a pulse signal whose polarity is inverted for each vertical synchronizing signal of the television signal (hence for each track). A so-called CTL tracking servo system that performs tracking control by using the ED has been used. In this case, the change of the error signal with respect to the tracking deviation amount corresponds to FIG. 4, and as shown in FIG. 8, when the tracking deviation occurs at the phase positions T0, T1, T2, T3 ... Lock point T0 , T2 ... is the oscillation point T3
, And so on, which means that one lock point occurs for two tracks.
Therefore, comparing the case of the CTL method of FIG. 8 with the case of the ATF method of FIG. 4, etc., if the servo time constant characteristics are selected to be equal to each other, the lock-in time of the ATF method is stochastically ATF.
It will require twice as long as the lock-in time of the system.

Therefore, the applicant of the present invention has previously proposed a tracking control device that shortens the lock-in time in the ATF method (Japanese Patent Laid-Open No.
5848). This tracking control device generates a lock-in error detection signal from the lock-in error detection circuit when the difference frequency component generated in the multiplication calculation force of the reproduction pilot signal and the reference pilot signal is not within the predetermined lock-in range, and detects the reference by the detection output. The skip control circuit skips the pilot signal circulation order by a predetermined number of steps. According to such a tracking control device, in a state in which the reproducing head is located outside the lock-in range of the tracking control device, the circulation order of the pilot frequencies of the reference pilot signal is skipped by a predetermined number of steps.
The tracking controller can be locked in the phase servo system of the video tape recorder in a relatively short time.

D Problems to be Solved by the Invention By the way, when a tape is sent at a speed different from the normal reproduction speed, a noise band is generally generated on the reproduction screen, and it is necessary to control so that the noise band is not uncomfortable. is there. For this reason, the present applicant has previously proposed a video signal reproducing device (Japanese Patent Laid-Open No. 57-202185) for controlling this noise band in a 4-frequency ATF tracking device. This video signal reproducing device can fix the reproduction phase to an optimum state by adjusting the switching period of the reference pilot signal to the reproduced pilot signal, and reduce the noise band generated when crossing the track. It can be fixed or fixed.

However, when the tape reproducing speed becomes high, the reference pilot signal must be switched at high speed, and the control becomes very complicated. Further, at the time of high speed reproduction, there is a drawback that it is difficult to time-divide the reference pilot signal for lock detection because a signal delay occurs due to the pilot signal processing system circuit. Therefore, for example, when the high speed reproduction is performed from the normal reproduction, it may be possible to go to the oscillation point depending on the rising phase, and at that time, it takes a longer time than usual for the noise band to stabilize.

FIG. 9 is a diagram showing an example of the locked state of this phase,
For example, assume that the reference pilot signal (FIG. 9B) is sequentially switched to f ₁ , f _2, ... In synchronization with the reference signal switching pulse signal (FIG. 9A). Then, assuming that the VTR playback is fast-forwarding at 5 times speed, the locus of the head is 9th.
It is assumed that the locus shown in FIG. At this time, the servo error sample pulse signal (FIG. 9F) is used to shift the vicinity of the zero crossing point of the tracking error signal (solid line or broken line in FIG. 9D) which is sequentially switched by the polarity inversion pulse signal (FIG. 9E). The sample and hold is performed as shown in G, and the tracking signal is obtained from the sample and hold signal. Here, for example, when the locus of the head at the time of rising is as shown in FIG. 9H, if a tracking error signal is obtained at this time as shown by the solid line in FIG. The noise band is locked stably, but when the tracking error signal is as shown by the broken line in FIG. 9D, the so-called back lock state is set, and the head locus moves to or as shown in FIG. 9H. Then lock it. Therefore, the noise band during this period is not stable, and it takes a long time to stabilize the noise band.

The present invention has been made in view of the above problems, and an object thereof is to provide a tracking control device capable of fixing a noise band in a short time even during high-speed reproduction.

E means the present invention the tracking control device for solving the problem, a recording pilot signals f ₁ frequency is changed sequentially and _{cyclically, f 2, f 3, f} 4 recorded ... tracks T _1, T ₂ · ..Recorded on recording tracks T ₁ , T ₂ ...
When reproducing, recorded pilot signals f ₁ , f ₂ ... Reference pilot signals f ₁ , f ₂ , f ₃ , f ₄ whose frequencies sequentially cyclically change with respect to the reproduced pilot signals obtained by reproducing ·························· In a tracking control device configured to control the tracking position of the reproducing head by detecting a tracking error signal based on the multiplication calculation force, a reference is synchronized with the head switching cycle during high-speed reproduction The reference pilot switching means (34) for switching the pilot signals f ₁ , f ₂ ... And the polarity of the tracking error signal is inverted within each reference pilot switching section of the reference pilot switching means during high speed reproduction, Polarity inverting means (46) for aligning the slopes near the zero cross point to the same polarity, and zero of the output signal of the polarity inverting means in synchronization with the polarity inversion. First sample and hold means (50) for sample and hold near the loss point, second sample and hold means (51) for sample and hold near the maximum or minimum value of the tracking error signal in synchronization with polarity reversal, and The tracking error signal sampled and held by the second sample and hold means (51) is compared with a predetermined level, and the oscillation point of the tracking loop is determined based on the output of the comparison means (58) during high speed reproduction. It is designed to be detected.

According to the tracking control device of the present invention, the oscillation point of the tracking loop is detected based on the tracking error signal sampled and held by the sample and hold circuit (51). It can be done in a short time even when locked from the back, and the lock-in time until the noise band in the playback screen becomes stable becomes short.

G Embodiment Hereinafter, one embodiment of the tracking control device of the present invention will be described.
Description will be made with reference to FIGS.

Configuration of G ₁ Tracking Control Device The tracking control device of the present example performs tracking by the 4-frequency ATF method as in the conventional example. FIG. 1 shows the configuration of the tracking control device of this example, and (31) in the drawing shows a reproduction pilot signal supply terminal. The reproduction pilot signal obtained at the reproduction pilot signal supply terminal (31) is multiplied by the multiplier (35) through the low-pass filter (32).
It is supplied to one of the multiplication input terminals. Also, the pilot signals f ₁ , f ₂ , f ₃ , f ₄ of the first to fourth predetermined frequencies output from the pilot signal generator (33) are supplied to the switch circuit (34), and the switch circuit (34) This pilot signal is sequentially switched at the timing commanded by the timing control signals (36a) and (36b) from the timing generator (36) described later, and the multiplier (35) is used as the reference pilot signal (34a).
It is supplied to the other multiplication input terminal of. This multiplier (35) multiplies the reproduction pilot signal and the reference pilot signal,
The multiplication calculation force signal is sent to the first band pass filter (37) and the first
To the series circuit with the DC conversion circuit (39) and the series circuit with the second bandpass filter (38) and the second DC conversion circuit (40), and output signals of the respective series circuits to the first series circuit. It is supplied to one comparator (41) and one and the other comparison signal input terminals. The first comparator (41) detects a difference between the reference pilot signal and the reproduction pilot signal, and a tracking error signal corresponding to the detection of the difference is sent to the first switch (46) via the inverter (42). And the tracking error signal is directly supplied to the second fixed contact (46b) of the first switch (46). The switching control of the first switching device (46) is performed by a signal from the timing generator (36). That is, the timing generator (36) judges the reference signal (the switching pulse signal and the VTR operation signal supplied from the VTR mode bus line (44)) supplied from the switching pulse signal supply terminal (43) synchronized with the head switching. Then, the timing control signals (36a) and (36b) for determining the reference signal are supplied to the switch circuit (34), and an ATF switching pulse is applied to one input terminal of the exclusive NOR circuit (48). The signal (36c) is supplied from the timing generator (36) via the inverter (45) to the first fixed contact (47a) of the second switch (47) and the second switch (47). The reverse polarity pulse signal (36d) is supplied to the second fixed contact of).
Switching of the movable contact (47c) of the second switching device (47) is controlled by an output signal of a flip-flop (59) described later, and a polarity reversal pulse signal (36d) on the side to which the movable contact (47c) is connected. Is supplied to the other input terminal of the EX NOR circuit (48). The output signal of the EX NOR circuit (48) controls the switching of the movable contact (46c) of the first switching device (46). The tracking error signal obtained at the movable contact (46c) controlled in this way is supplied to the first and second sample hold circuits (50) and (51) via the signal amplifier (49). First and second sample and hold circuits (50)
The timings of sample and hold of (51) and (51) are controlled by the timing control signals from the timing generator (36). Then, the output signal of the first sample hold circuit (50) is supplied to the gate tracking error signal output terminal (53) through the signal amplifier (52). Further, the output signal of the second sample hold circuit (51) is passed through the signal amplifier (54) and the resistor (55) as the back lock signal (54a), and the one comparison signal of the second comparator (58). The reference power source (57) is supplied to the other comparison signal input terminal of the second comparator (58). This second
The output signal of the comparator (58) is supplied to the input terminal of the flip-flop (59). The one comparison signal input terminal and the output terminal of the second comparator (58) are connected via the resistor (56). Then, the output signal of the flip-flop (59) is supplied to the control input terminal of the second switching device (47), and the output signal of the flip-flop (59) causes the second switching device (4).
Control the movable contact (47c) of 7).

Operation of G ₂ Tracking Control Device The operation of the tracking control device of this example configured as described above will be described with reference to FIGS. 2 and 3.

The tracking control device of this example includes a timing generator (3
6) to the first sample-hold circuit (50), as shown in FIG. 2F, an ATF error sample pulse signal (FIG. 2F) for sample-holding the vicinity of the zero crossing point of the tracking error signal (FIG. 2D). The gate ATF error signal (FIG. 2H) which is supplied and sample-held in the vicinity of the zero-cross point of the tracking error signal is output by this sample pulse signal, and this gate ATF error signal is output from the gate tracking output terminal (55). A back lock determination sample for holding the timing generator (36) to the second sample and hold circuit (51) immediately before the polarity of the tracking error signal (D in FIG. 2) is inverted as shown in FIG. 2G. A pulse signal (FIG. 2G) is supplied, and a back lock discrimination signal (FIG. 2I) is sampled and held immediately before the polarity of the tracking error signal is inverted by the sample pulse signal. This back lock discrimination signal shows the minimum value as shown in FIG. 2I in the case of the tracking error signal (state of FIG. 2D) when the head locus of FIG. The maximum value (not shown) is obtained in the case of the tracking error signal in the case of the head locus (state opposite to that in FIG. 2D). Then, this back lock discrimination signal is supplied to the second comparator (58), and this comparator (58) compares the reference voltage of the reference power source (57) with the back lock discrimination signal. In this comparison, for example, as shown in FIG. 3, by setting the reference voltage V _R to a value slightly higher than the 0 V point of the ATF error signal voltage, the head scanning is near the oscillation point (± α from the oscillation point). Phase), the output of the comparator (58) becomes high level, and when it is not near the oscillation point, it becomes low level. The back lock is detected by the high level output signal of the comparator (58), and the connection of the second switch (47) is switched via the flip-flop (59). This second switching device (47)
Is inverted, the polarity inversion pulse signal (36d) input to the other input terminal of the EX NOR circuit (48) is inverted,
Depending on the state of the ATF switching pulse signal (36c) input to one terminal, the connection of the first switching device (46) is switched and the tracking error signal is inverted. In addition, the comparator (5
At the time of 8) low level signal, the tracking error signal is maintained as it is.

In this way, by inverting the tracking error signal at the time of back lock, the phase is locked from this time of inversion, and good tracking can be performed with almost no lock-in time required. Therefore, even when the back is locked, it does not take time to lock like the case where the trajectory of the head moves to lock the phase,
It is no longer locked after the noise band in the playback screen moves.

In the above embodiment, the phase is locked by switching the second switching device (47), but the second comparator (58) is used.
The reference pilot signal is skipped by 2 fields according to the comparison output signal of (for f ₁ , f _{3 for} f ₁ , f _{4 for} f ₂ , f ₃
The same tracking error signal can be obtained by performing f ₂ ) at f ₁ and f ₄ , and the phase can be locked immediately. Furthermore, the present invention is not limited to the above-described embodiments, and it goes without saying that various other configurations can be adopted without departing from the gist of the present invention.

H According to the tracking control device of the present invention, the oscillation point of the tracking loop is detected based on the tracking error signal sampled and held by the sample and hold circuit, so that the oscillation point can be easily discriminated during high speed reproduction. It will be locked in a short time even when locked on the back,
There is an advantage that the lock-in time until the noise band in the playback screen becomes stable is short.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the tracking control device of the present invention, and FIGS. 2 and 3 are diagrams for explaining the example of FIG. 1, FIG. 4, FIG. 6, and FIG. 7, respectively. , FIG. 8 and FIG. 9 are diagrams for explaining the ATF system, respectively, and FIG. 5 is a configuration diagram for explaining the ATF system. (36) is a timing generator, (51) is a second sample and hold circuit, and (58) is a second comparator.

Claims (3)

[Claims] 1. A recording pilot signal having a frequency that cyclically changes cyclically is recorded on a recording track, and the frequency is sequentially cyclical with respect to a reproduction pilot signal obtained by reproducing the recording pilot signal when reproducing the recording track. In a tracking control device configured to control the tracking position of the reproducing head by multiplying the reference pilot signal that changes to, and detecting the tracking error signal based on the multiplication calculation force, the head switching cycle is changed during high-speed reproduction. Reference pilot switching means for switching the reference pilot signal in synchronism, and the polarity of the tracking error signal is inverted within each reference pilot switching section of the reference pilot switching means at the time of high speed reproduction, and the zero cross point of the tracking error signal is inverted. Slopes in the vicinity have the same polarity Polarity reversing means for aligning, and first sample and hold means for sampling and holding near each zero-cross point of the output signal of the polarity reversing means in synchronization with the polarity reversing to generate a tracking position control signal at the time of the high speed reproduction, Second sampling and holding means for sampling and holding near the maximum value or the minimum value of the output signal of the polarity inverting means in synchronization with the polarity inverting, and a tracking error signal sampled and held by the second sampling and holding means A tracking control device comprising a comparison means for comparing with a level, and detecting the oscillation point of the tracking loop based on the output of the comparison means during the high speed reproduction. 2. The tracking control device according to claim 1, wherein the tracking error signal is inverted at the detected oscillation point of the tracking loop. 3. The tracking control device according to claim 1, wherein the reference pilot signal is skipped by a predetermined field at the detected oscillation point of the tracking loop.