JPS62147880A - High-speed search servo circuit - Google Patents

Abstract

PURPOSE:To fix a noise band by switching a reference pilot signal, during the high-speed reproduction operation, in synchronization with the switching period of a head, taking out the adjacency of the zerocross point of a tracking error signal as an error signal, and controlling the tape speed by using the error signal. CONSTITUTION:When the reproduction is operated at a speed five-times of normal reproduction speed, head loci comes to be H1, H2... in which the reference pilot signals 34a scan the five tracks of a video tape 5 at the same time. Taking an example of the head locus H1, the tracking error signal (a) comes to be H' which is such that the zerocross point exists on the tracks scanned by the recording pilot signals f1 and f3. The zerocross point alpha on the track of the recording pilot signal f1 is a lock point, while the zerocross point betaon the track of f3 is an oscillation point. A pulse signal to sample hold only the adjacency of said lock point, is supplied to a sample holding circuit 47 from a timing generator 36 to output a gate ATF error signal. And this signal is supplied to a capstan motor control circuit to control the tape speed.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A. Field of industrial application B. Overview of the invention C. Prior art D. Problem to be solved by the invention E. Means for solving the problem (Fig. 1) F. Effect G. Example G1 Configuration of servo circuit (1st Figure) Operation of G2 servo circuit (Figures 2 and 3) Other embodiments of G3 servo circuit (Figures 4 and 5) Pilot signals with different frequencies are cyclically recorded together with video signals on recording tracks formed in sequence across the running direction, and during playback, the frequencies of the pilot signals played from adjacent tracks are detected and played back. The present invention relates to a tracking control device applied to an automatic track following method (hereinafter referred to as an ATF method) in which a head is tracked to a predetermined track.

B. Summary of the Invention The present invention is a servo circuit for high-speed searching that is commonly used in the ATF system, which switches the °ζ reference pilot signal in synchronization with the switching cycle of the head during high-speed reproduction, and also corrects the error near the zero-crossing point of the tracking error signal. By controlling the tape speed using the extracted error signal, it is possible to fix the noise band and eliminate noise during high-speed playback with a simple configuration without changing the reference pilot signal for each track. Bands can be fixed.

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

A four-frequency type tracking control device that sequentially records pilot signals of four frequencies on the recording track has been proposed as an ATF type tracking control device. The state is shown in Figure 6. That is, considering the case where the track pitch and head width are approximately equal, the error signal s3 becomes O at the phase lock point 1'0, and at this time the reproducing head is controlled to a correct tracking state. On the other hand, if the reproducing head causes tracking deviation in the positive direction, the amount of tracking deviation increases by one track pinch, that is, by the slope of the pause until reaching the adjacent track TI. The amount of increase reaches its maximum value at track 'rl, and thereafter, during the range (range Tl to T3) in which the amount of tracking deviation increases by two track pinches, the error signal s3 decreases with a negative slope, and then It becomes 0 at position T2 and becomes the value of the subsequent page. This phenomenon reaches a negative minimum value at the track T3 position, and the tracking deviation amount is 1゛3 at this position.
After passing this point, the error signal increases again with a positive slope for two track pitches, and eventually becomes 0 at the position 'r4. (Thus, the error signal changes by one period during the tracking deviation T0-74 of the track pinch, and as the tracking deviation increases more than this, this cycle of every four track pitches is repeated.

In response to such changes in the error signal, the tracking control system controls the playback head so that if the error signal increases in the positive direction at the lock position TO, the amount of tracking position deviation decreases, or if the error signal decreases in the negative direction. If the amount of tracking deviation increases, the reproducing head is controlled to reduce the amount of tracking deviation. Therefore, the playback head has an error signal of 0.
It will be locked to the phase position TO. On the other hand, the error signal also becomes 0 at the phase position T2, but if the error signal slightly increases in the +E direction or decreases in the negative direction from the phase point T2, the amount of tracking deviation increases. Because the playback head is controlled, it cannot be a stable point (this is called an oscillation point).

As an ATF type tracking control device that generates an error signal that changes in this way, those shown in principle in FIGS. 7 to 9 have been proposed.

That is, as shown in FIG. 7, this tracking control device receives a part of the signal st of the playback output of a rotating video head as a recording/playback head through a pilot signal detection circuit +11 having a low-pass filter configuration, and transfers it to a magnetic tape as a recording medium. A reproduced pilot signal S2 whose component is the reproduced output of the recorded pilot signal is generated, and this reproduced pylon 1
- Giving the signal S2 to the error signal forming circuit (3). The error signal forming circuit (3) generates a tracking error signal 33 (Fig. 6) formed under the control of the reference signal generating circuit (4).
Send out.

On the tape (5), as shown in FIG.
r3. Four video tracks TI, T2 . r4 are recorded together with the video signal. The pairs of T3 and T4 are formed diagonally and closely together in a cyclical manner. Here, the effective width of the video head constituting the recording/reproducing head (6) is selected to be approximately equal to the width of tracks T1 to T4, for example, so that the reproducing head (6) is currently positioned as shown by the solid line in FIG. The track being scanned for playback (
This is called the playback track). When tracking correctly on the playback track, the pilot 4g recorded on the track
By reproducing only the signal, only one type of pilot frequency component is included in the reproduced output.On the other hand, when the head (6) is shifted to the right or left with respect to the track as shown by the broken line, By also reproducing the pilot signal recorded on the track adjacent to the right or left side of the reproduction track, the pilot frequency components included in the reproduction output become two types, and the magnitude of each pilot frequency component corresponds to the track. The size corresponds to the facing length of the reproducing head facing the reproducing head.

However, the frequencies of the four types of pilot signals "1 to f4 are selected as the low frequency band of the color component converted to the low frequency (600 to 700 (1lz)), and are circulated in the four tracks "1 to T4]. For example, centering on the odd-numbered tracks TI and T3, the frequency difference with the pilot signal of the right-hand track is ΔfA, and the frequency difference with the pilot signal of the left-hand track is ΔfB, and the frequency difference with the pilot signal of the right-hand track is ΔfB. Centering on tracks T2 and T4, the frequency difference with the pilot signal of the right track is ΔrB, and the frequency difference with the pilot signal of the left track is ΔfA.

Therefore, the head (6) is an odd numbered track Tl, T3.
When reproducing a signal, if there is a signal component with a frequency difference of ΔfA as a frequency component of the pilot signal included in the reproduced signal, it can be seen that the head (6) is shifted to the right. If there is a component, it can be seen that the head (6) is shifted to the left, and the frequency difference is ΔrA.
It can be seen that tracking is performed correctly when there is no Iha component of ΔfB.

Similarly, when the °ζ head (6) is reproducing even-numbered tracks T2 and T4, if there is a signal component with a frequency difference Δ[B as a frequency component of the pilot signal included in the reproduced signal, the head (6) is found to be in a right-shifted state,
Also, if there is a signal component with a frequency difference of Δf^, the head (6)
It can be seen that it is shifted to the left.

In this embodiment, the first. Second, third and fourth tracks Tl, T2 . T3. Frequency f1. assigned to T4. f2. f3. r* is ft=102 (kHz),
f2=116(kllzJ, fi=
'160 (kllzJ, f 4 = 146 (k
Hz), so the difference frequencies ΔfA and ΔfB are ΔfA=lft-f21=lfx [+l= 14
(kllz) −(1)AfB=lf
2-fl 1=lf4 fl 1=44 (kll
z ) ・= −(Selected as 21.

The reproduced signal S1 having such content obtained from the head (6) is given to a pilot signal detection circuit (1) having a low-pass filter configuration, and a reproduced pilot signal S2 is obtained by extracting the pilot signal included in the partial body signal S1. is given to the multiplication circuit (14) as the first multiplication input.

The multiplication circuit (14) is given 1/3 of the reference signal generation times (41 reference pilot No. 1m Sll) as the second multiplication power.

The reference signal generation circuit (4) is connected to a pilot signal generation circuit (16) that generates four pilot frequency outputs of frequencies f1 to f4, and a rotating drum (not shown) that generates tape among the two video heads. Head switching pulse RF- that changes the logic level every time the scanning head switches
3W (FIG. 9A). In this embodiment, the switch circuit (17) has a Z>quaternary counter circuit that performs a counting operation every time the level of the head switching pulse RF-3W changes. Track Tl~1゛4
The gate signal corresponding to the gate signal can be sequentially repeated,
The gates of these tracks 1'1 to T4 are opened by the gates Hi<, respectively, and the outputs of pilot frequencies f1 to f4 of the pilot signal generation circuit (16) are sequentially sent out as the reference pilot signal Sll, as shown in FIG. 9B. It is done like this.

Note that the reference pilot signal Sll obtained at the output end of this switch circuit (17) is sent to the video head (6) as a recording pilot signal s4 via a signal line (18) during recording.
), and while the video head (6) is scanning the first to fourth tracks T1 to T4, pilot signals of the corresponding frequencies f1 to f4 are sequentially applied to the video head (6) to scan each of the tracks T1 to T4. The data is recorded on tracks Tl-T4.

In this way, while the head (6) scans each of the first to fourth tracks TI-T4, the reproduced pilot signal S2 obtained at the output terminal of the pilot signal detection circuit (1) is applied to the corresponding reproduced track. By multiplying by the synchronized reference pilot signal Sll, when there is a tracking error, a signal component having a frequency that is the difference between the frequency component included in the regenerated pilot No. 14 S2 and the frequency of the reference pilot signal Sll is obtained. Multiplication output S containing
12 (actually, the multiplication output S12 also includes other signal components such as the frequency component of the sum). This multiplication output S
12 are provided in the first and second difference frequency detection circuits 173 (20) and (21), each of which is constituted by a band-pass filter. The first difference frequency detection circuit (20) extracts the signal component of the difference frequency Δ[A based on equation 11 described above when the multiplication output S12 contains ) to obtain a DC level first error detection signal 313.

Similarly, the second difference frequency detection circuit (21) extracts the (m component) of the difference frequency Δf8 based on the above-mentioned equation (2) from the multiplication output 512 and converts it into a direct current circuit ( 23) to obtain the second error detection signal S14.

Here, the head (6) moves to the eleventh second, third, fourth tracks Tl, T2 . T3. When attempting to track T4, a switch circuit (17) is activated to track each track TI, T2 . The frequencies are fl and fl at the timing corresponding to 'I'3°T4.

If the base Y-pilot signal Sll of f3+f4 is shifted to the right, the reproduced pilot signal S2 obtained based on the reproduced signal Sl of the head (6) will be
As shown in FIG. 9, pilot signals of frequencies f1 and fl, fl and f3+f3 and f+, f→ and fl are included, and the difference frequency Δf^ (=f1 to f2) is obtained as the multiplication output S12 as shown in FIG. 9 Di. , Δf8 (=f
2 to f3), ΔfA (= fi to f4), ΔfB (=
f4 to ft) in sequence. On the other hand, if the head (6) is shifted to the left, the reproduced pilot signal S2 will sequentially have frequencies f4 and rt, as shown in FIG. 902.
rt and fl, fl and f3+ fl and f4 pilot signals are included, and the multiplication output S
12 is the difference frequency ΔfB (=f4~
f1), ΔfA (=ft~f2).

ΔfB (=f2~f3), ΔfA (=fa~f+)
′ will be included sequentially.

Thus, as shown in FIGS. 9E and F (for example, showing a right-shifted state), the DC level of the first and second error detection signals S13 rises from 0 every time the head (6) scans a different track. and 314 can be obtained from the DC conversion circuits (22) and (23).

The first and second error detection signals S13 and 514 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 SI3 and S14 are generated as shown in FIG. 9G. A subtraction output S15 that changes in an alternating current manner is obtained each time it is obtained alternately. This subtraction output S15 is applied to the first input terminal a1 of the direct changeover switch circuit (25), and the polarity is inverted in the inverting circuit (26) and applied to the second input terminal a2. The changeover switch circuit (25) uses the head changeover pulse RF-3W to switch the head (6) to odd-numbered tracks TI, T, for example.
When scanning 3, it switches to the first input terminal AL side,
On the other hand, even-numbered tracks '1' and '2'. When scanning T4, a switching operation is performed to the second input terminal a2, and thus when the head (6) is shifted to the right as shown in FIG. Level output S
16 is obtained (on the other hand, when there is a left shift state, the DC level output SL6 has a magnitude corresponding to the left shift amount and becomes negative polarity), and this is transmitted through the output amplification circuit (27) consisting of a DC amplifier. The tracking error signal S3 is sent out as a tracking error signal S3.

Incidentally, if the head (6) is shifted to the right, for example, the reproduced track will be the odd numbered track T'1. Multiplication circuit (14) when T3
As a signal component of the difference frequency Δr^ appears at the output terminal of the , the output from the first difference frequency detection circuit (20) is given to the subtraction circuit (24), and at this time, the changeover switch circuit (25) Since it is switched to the first input terminal al side, a tracking error signal S3 of a positive DC level is sent out. On the other hand, the playback track is the even numbered track T2.
At T4, the output terminal of the multiplication circuit (14) has a difference frequency Δr.
When the signal component B appears, the output from the second difference frequency detection circuit (21) side is given to the subtraction circuit (24), and at this time, the changeover switch circuit (25) is applied to the second manual power @a2 side. Since the subtraction circuit (24) is switched, the polarity of the negative output of the subtracting circuit (24) is inverted by the inverting circuit (26) and sent out as a tracking error signal S3 of a positive DC level.

Therefore, if this tracking error signal S3 is used as a correction signal in the phase servo circuit of the capstan servo loop to correct the tape running speed to be faster when it is IF and slower when it is negative, it is possible to correct the difference between the video head and the playback track. The phase shift can be corrected, thus realizing correct ATFI-ranking servo.

In the above principle configuration, the principle has been described assuming that no difference frequency component occurs at the output end of the multiplication circuit (14) when the head (6) correctly tracks each track, but in reality, even in this tracking state, the head Pilot signals of adjacent tracks on the left and right sides are generated in the reproduced signal Sl.

That is, in practice, when no card band is provided between tracks during recording, newly recorded tracks are sequentially recorded in a recording mode so as to partially overlap already recorded tracks. Therefore, in this case, the width of the head (6) is larger than the width of each track T I -T 4, so that when tracking correctly, the head (6) protrudes into the adjacent tracks on the left and right sides. Therefore, since the head (6) reproduces the pilot signals of the tracks adjacent to the left and right sides, error detection signals 313 and 31 corresponding to signal components of difference frequencies corresponding to the length of the overflow
4 (Fig. 9 E and F) to DC converting circuits (22) and (23)
) occurs from

In addition, when a guard band is provided, the width of the head (6) becomes almost equal to the width of the track, but the pilot signal recorded on the adjacent tracks on the left and right sides is reproduced by the head (6) as a crosstalk signal. mixed into the signal. Therefore, the error detection signals 313 and S14 include a signal component of a difference frequency corresponding to a crosstalk signal.

However, the pilot signal mixed into the reproduction output S1 of the head (6) from the adjacent track is processed by the multiplication circuit (1
Since the signal components of difference frequencies Δf^ and ΔfR are generated simultaneously at the output terminal of 4), they cancel each other out when the error detection signals 313 and 314 are rapidly subtracted in the subtraction circuit (24). . Moreover, the head (6)
When the head (6) is tracking correctly, the head (6) is in a symmetrical position with respect to the adjacent tracks on the left and right sides. The left and right sides are almost equal,
In the end, the content of the calculation output S15 is equivalent to the above case where the width of the head (6) is considered to be approximately equal to the width of the track.
Therefore, in the tracking operation of the tracking control device,
Because the head width is larger than the track width or due to crosstalk, there is no adverse effect of the difference frequency components occurring simultaneously from adjacent tracks on both sides.

In addition, in the above-described error signal forming circuit (3), the signal components of the difference frequencies Δf^ and ΔfB between the pilot signals of the reproduced track and its adjacent tracks are obtained. However, instead of this, the levels of the reproduced pilot signals of frequencies fl to r4 are detected by respective reproduced pilot signal detection circuits each having a band-pass filter configuration, and error detection signals S13 and S14 are obtained based on the detected outputs. You can also do it.

On the other hand, in a video tape recorder equipped with a 4-frequency ATF type tracking device that performs tracking control, the tracking control device (Japanese Unexamined Patent Application Publication No. 59-1979
31456) was previously proposed by the present applicant. This tracking control device utilizes the fact that when the playback head crosses multiple tracks when traveling at a speed different from the recording speed of the pilot signal, the level of the error signal of the tracking control device periodically undulates. A tape speed detection output corresponding to the tape running speed is obtained.

D. Problems to be Solved by the Invention By the way, when a video tape recorder performs high-speed playback that is different from the recording speed in this way, playback scanning is performed across gart bands between tracks or tracks with different recording azimuths. A noise band appears on the surface of the regenerated meat. When this noise band appears, the playback screen becomes difficult to see.

For this reason, the present applicant previously proposed a video signal reproducing device (Japanese Unexamined Patent Publication No. 57-202185 eu) that controls this noise band in a 4-frequency ATF type tracking device.This video signal reproducing device By adjusting the switching period of the reference pilot signal to match the reproduced pilot signal, the reproduction phase can be fixed at an optimal state, and the noise band that occurs when crossing the track can be reduced or fixed. be.

However, as the tape valve speed increases, the reference pilot signal must also be switched at high speed, making the control extremely complex.Furthermore, during high-speed playback, the pilot signal processing circuitry Due to the delay, there is a drawback that it is difficult to time-divide the reference pilot signal for lock detection. For this reason, if a video signal reproducing apparatus that controls the noise band in this manner is actually configured, the circuit configuration etc. will be extremely complicated.

To this end, it is an object of the present invention to provide a high-speed search zap circuit that can fix the noise band during high-speed reproduction with a Wi-car configuration.

E. Means for Solving the Problems According to the servo circuit for high speed search of the present invention, as shown in FIG. 1, for example, recorded pilot signals ft*f2*f3. Record f4 on the recording track Tr,'! '2... is recorded on the recording track T1. Reference pilot signal fl+f whose frequency sequentially changes cyclically with respect to the reproduced pilot signal obtained by reproducing the recorded pilot signal during reproduction of T2...
In a high-speed search servo circuit that controls the tracking position of the playback head by multiplying . The reference pilot signal f1+r2. f3
+r4, the vicinity of the zero-crossing point of the tracking error signal is extracted as an error signal, and the tape speed is controlled by this extracted error signal.

F Function According to the servo circuit for high-speed search of the present invention, the noise band can be fixed by extracting the vicinity of the zero-crossing point of the tracking error signal as an error signal and controlling the tape speed using this error signal. , it is possible to fix the noise band during high-speed playback with a simple configuration that only extracts the 1 m error without changing the reference pilot signal for each track.

G. Embodiment An embodiment of the servo circuit for high-speed search of the present invention will now be described with reference to FIGS. 1 to 3121.

Structure of G1 servo circuit The servo circuit for high-speed search in this example has 4 parts as in the conventional example.
Tracking is performed using a frequency ATF method. FIG. 1 shows the configuration of the high-speed search servo circuit of this example, and in the figure (31) is the reproduced pilot signal supply terminal. The reproduced pilot signal obtained at the nasal pilot signal supply terminal (31) is supplied to one multiplication input terminal of a multiplier (35) via a low-pass filter (32). Further, the pilot signal generator (33) outputs pilot signals fx+, f2 . [3
゜f4 is supplied to a switch circuit (34), and the switch circuit (34) sequentially switches this pilot signal at timings commanded by timing control signals (36a) and (36b) from a timing generator (36), which will be described later. A multiplier (
35) to the other multiplication input terminal. This multiplier (
35), the reproduced pilot signal and the reference pilot signal are multiplied, and the multiplied output signal is passed through the first bandpass filter (35).
7) and the first direct current converting circuit (39) and the second
bandpass filter (38) and second DC converting circuit (4)
0), and the output signals of these series circuits are supplied to one and the other comparison signal input terminals of the first comparator (41). ) detects the difference between the reference pilot signal and the regenerated pilot signal, and sends a tracking error signal corresponding to the detected difference to the first switch of the first switch (46) via the inverter (42).
The tracking error signal is directly supplied to the second fixed contact (46b) of the first switch (46). This first switch (4
The switching control 6) is performed by a signal from the timing generator (36). That is, the reference signal switching pulse signal supplied from the switching pulse signal supply terminal (43) synchronized with head switching and the VTR operation signal supplied from the VTR mode pass line (45) are sent to the timing generator (36).
The timing control signal (36a), (
36b), and also supplies an ATF switching pulse signal (36c) to the control terminal of the first switching device (46). The tracking error signal obtained at the drive contact (46c) of this first switch (46) is supplied to a sample and hold circuit (47), and this sample and hold circuit (47)
Sample and hold the tracking error signal supplied by . The timing of this sample and hold is determined from the timing generator (36) to the sample and hold signal (36).
6d). Note that this sample-and-hold pulse signal (36d) is set at a predetermined timing by a timing setting signal supplied from the sample-and-hold timing setter (44) to the timing generator (36). The tracking error signal sampled and held by the sample and hold circuit (47) at this set timing is used as the ATF error signal by the amplifier (
48) through the “ζday 1-ATF error signal output terminal (
49), and the gate ATF error signal obtained at this output terminal (49) is supplied to a capstan motor control circuit (not shown) to control the capstan.

Operation of the 02 Servo Circuit The operation of the high-speed search servo circuit of this example configured as described above during a high-speed search will be described with reference to FIGS. 2 and 3.

When performing servo during high-speed search using the servo circuit of this example, first, the head switching pulse signal (Fig. 2A) supplied from the timing generator (36)' to the switch circuit (34) from the terminal (43) is applied. A signal is synchronized to sequentially change the °ζ reference pilot signal (second path I B ), and the reference pilot signal is switched in synchronization with the head switching, and when this reference pilot signal is fL and f3, Compare with f2 and f4! (
The ATF switching pulse signal (3
Output 6a). Due to this inversion, the tracking error signal becomes a signal that undulates at regular intervals, as shown in the second figure. Here, in this example, the sub-time IM for high-speed search is
If playback is performed at a speed five times faster than the normal playback speed using a video tape recorder equipped with a video tape recorder, as shown in FIG. 2G, 11, f2 + f3, f4.

A head trajectory H1r 82 rHl that scans five tracks at once on a video tape (5) in which fl... and a reference pilot signal are sequentially recorded for each track.
...becomes... Here, for example, the head! When scanning is performed using the reference pilot signal f1 at the time of 1L trace H1,
The tracking error signal during scanning of H1 is shown in Figure 2G.
The signal has a zero cross point at track 3.

At this time, since the reference pilot signal is rl, the recording pilot signal [The zero-crossing point of track 1 (point α in FIG. 2) is the lock point, but the recording pilot signal f3
The zero-crossing point of the track (point β in FIG. 2) is the oscillation point. Therefore, as shown in FIG. 2E, a sample-and-hold pulse signal is supplied from the timing generator (36) to the sample-and-hold circuit (47) to sample and hold only the vicinity of this lock point, and as shown in FIG. The sample and hold circuit (47) outputs a gate ATF error signal obtained only from the vicinity of the point.The tape speed is then controlled by supplying this gate ATF error signal to the capstan motor control circuit.That is,
For example, if playback is performed at 3x speed, when good tracking is performed as shown in Fig. 3, the trajectory and error signal will be Ha shown in Fig. 3 A and D.
The ATF error signal (Fig. 3 D) at the time of gate by the sample and hold pulse signal (Fig. 3 E) is at the time of locking, but when it tries to deviate from this trajectory Ha to one trajectory Hb, the voltage of the error signal increases. The capstan motor is controlled to accelerate and returns to the trajectory Ha. Also, the trajectory Ha
When an attempt is made to deviate from the trajectory Hc to the other trajectory Hc, the voltage of the error signal decreases, the capstan motor is controlled to decelerate, and returns to the trajectory Ha. Tracking control is performed in this way.

As described above, according to the fast search servo circuit of this example, good tracking can be performed without changing the switching period of the reference pilot signal even during high-speed search.
For this reason, the noise band is also fixed. Note that the fixed position of the noise band can be set using the sample and hold timing setter (
44) can be set for sample hold.

Other Embodiments of G3 Servo Circuit In the above embodiment, only the tracking error signal of the lock point was used, but for example, as shown in FIG. ) and an inverter (50) and a second switch (51) are provided between the pJ moving contact (51c) of the second switch (51).
) is connected to the first fixed contact (51a), the output signal of the first switch (46) is supplied to the sample hold circuit (47) via the inverter (50), and the movable contact ( 51c) is the second fixed contact (51b
) side, the first switch (46)
The output signal is supplied as is to the sample hold circuit (47). Then, this second switch (51
) is controlled by a polarity inversion pulse signal (36e) from a timing generator (36). The other configurations are the same as the example in FIG. With this configuration, for example, during high-speed playback at 5x speed, as in the example in Figure 2,
As shown in Fig. 5E, the timing generator (36) outputs a polarity inversion pulse signal that switches every half of the head switching period (to Fig. 5), and the tracking error signal (Fig. 5D) is output at the oscillation point. is an error signal (FIG. 5F) which is inverted so that it becomes the same as the lock point. and,
By supplying a sample and hold pulse signal (FIG. 5G) so as to extract each zero-crossing point of this error signal, a good gate A TF error signal as shown in FIG. 5H can be obtained.

In addition, when inverting the polarity of the error signal as in the example in Fig. 4, instead of sample-holding,
An equivalent ATF error signal can also be obtained by integrating error No. 46 shown in FIG.

Furthermore, it goes without saying that the present invention is not limited to the above-mentioned embodiments, and can take various other configurations without departing from the gist of the present invention.

H. Effects of the Invention According to the servo circuit for high-speed search of the present invention, the noise band can be fixed by extracting the vicinity of the zero-crossing point of the tracking error signal as an error signal and controlling the tape speed using this error signal. This has the advantage that the noise band can be fixed during high-speed reproduction with a simple configuration that only takes out the error (fi) without changing the reference pilot signal for each track.

[Brief Description of the Drawings] Fig. 1 is a configuration diagram showing an embodiment of a servo circuit for high-speed search of the present invention, Figs. 2 and 3 are diagrams for explaining the example in Fig. 1, and Fig. 4 is a configuration diagram showing another embodiment of the present invention,
Fig. 5 is a diagram for explaining the example in Fig. 4, Fig. 6, Fig. 8, Fig. 9, and Fig. 1θ are diagrams for explaining the ATF method, respectively, and Fig. 7 is a diagram for explaining the ATF method. FIG. (36) is a timing generator, and (47) is a sample and hold circuit.

Claims (1)

[Claims] A recording pilot signal whose frequency sequentially and cyclically changes is recorded on a recording track, and when the recording track is reproduced, the frequency sequentially cycles with respect to a reproduced pilot signal obtained by reproducing the recording pilot signal. In a high-speed search servo circuit that controls the tracking position of a playback head by multiplying a reference pilot signal that changes over time and detecting a tracking error signal based on the multiplied output, Switching the reference pilot signal in synchronization with the switching cycle, and extracting the vicinity of the zero cross point of the tracking error signal as an error signal,
A servo circuit for high-speed searching, characterized in that the tape speed is controlled by the extracted error signal.