JPS58161586A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To fix the generating position of a noise bar in a search mode, by reproducing pilot signals having different (m) types of frequencies, phases or single-room distributions of time and recorded on a video track and therefore controlling the traveling of a tape with a sample held signal. CONSTITUTION:The video signal supplied from a terminal 8 is added to the pilot signal produced by a pilot signal producing circuit 9 through an adder 10 and then supplied to video heads 5 and 6 to be recorded on the trucks of a magnetic tape 1. The pilot signals of different frequencies are used, and these frequencies are set lower than the frequency of the video signal. At the same time, the rotary phases of heads 5 and 6 are detected by a tack head 13 and compared with the reference signal by a phase comparator 16. A disk motor 7 is controlled by a phase error signal obtained from above-mentioned comparison. Then the detecting signal of the head 13 is held at a sample holding circuit 28. The output of the circuit 28 is added with the speed of revolution of a capstan 2 detected by a speed detector 18. Then a capstan motor 3 is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording and reproducing apparatus equipped with a device for fixing the position of a noise bar appearing on a screen during high-speed reproduction.

In a magnetic recording and reproducing device that uses a rotating video head to scan diagonally across a magnetic tape to record and reproduce video signals, in order to quickly find the part of the tape where a desired scene is recorded, the magnetic tape is heated faster than when recording. A quick-viewing mechanism is used that runs at high speed and plays. This quick-viewing mechanism includes a fast-forward playback mechanism that runs the tape at high speed in the same direction as during normal playback, and a rewind playback mechanism that runs the tape at high speed in the opposite direction. It is called a mechanism. During this search,
Because the video head scans across several video tracks, a bad S/H area similar to a sliver, or a noise bar, appears on the image quality. This noise bar occurs when the ratio between the magnetic tape's playback speed and recording speed is not constant.
Since it flows across the screen, it is very difficult to see and visually undesirable.

Therefore, in order to fix the position where this noise bar occurs, in conventional magnetic recording and reproducing devices, when searching, a control signal for tracking control is recorded on the control track at the bottom edge of the magnetic tape in relation to the recording position of the video track. Attempts have been made to control the tape running phase by using magnetic tape to run the magnetic tape at a constant speed. This control signal is a signal that is recorded by the control head in the longitudinal direction of the magnetic tape at the frequency of 4 of the vertical synchronization signal of the recording video signal, and is recorded on the tape at intervals according to the tape speed at the time of recording. Ru. Therefore, the generation position of the noise bar can be easily fixed by the frequency of this reproduction control signal during a search.

However, in this tracking control method using control signals, since the video head and the control head are located far apart, tracking may deviate due to changes in tape length between them, so the user must adjust the tracking by looking at the raw image. Therefore, the tracking adjustment 1aI11 structure is essential. Another drawback is that tracking errors can only be detected intermittently, making it impossible to obtain sufficient tracking control performance, especially when the pitch of the video track becomes narrower due to longer recording times.

Therefore, it is possible to constantly detect tracking errors.
An automatic tracking control method has been devised that eliminates the need for a tracking adjustment mechanism.

A typical example is tracking information during playback.
In this method, a pilot signal is superimposed on a video signal and recorded on a video track of a magnetic tape using a rotating video head. By reproducing this pilot No. 1 to form a tracking error signal and performing tracking control, automation of tracking control is achieved and its control performance is also improved.

However, on the other hand, unlike the method using control signals described above, this pilot method differs from the method using control signals in that the tape running direction
That is, there is neither a track signal recorded at regular intervals in a predetermined phase relationship with the video track in the longitudinal direction nor a control head for reproducing the track signal. Therefore, during a search, the conventional method of fixing the position of the noise bar using a noise bar signal cannot be applied, and it is necessary to devise a new method.

In view of the above-mentioned points, an object of the present invention is to provide a means for fixing the generation position of a noise bar during a search in a magnetic recording/reproducing apparatus that performs tracking control using a pilot signal recorded on a video track. It is in.

In order to achieve the above object, the present invention provides m types (m
≧3 (an integer) is recorded alternately on each video track, the pilot signal is detected during playback to generate a tracking error signal, and tracking control is performed using this signal. At a predetermined time point when the video head scans a predetermined point on the magnetic tape, the tracking error signal is sampled and held, and this sampled and held tracking error signal is supplied to the magnetic tape drive device, so that the reproduction image can be prepared. The configuration is such that the generation position of the noise bar that appears is fixed.

Hereinafter, the present invention will be explained in detail using drawings.

FIG. 1 is a block diagram showing an example of the configuration of a rotating head helical scan type magnetic recording and reproducing apparatus according to the present invention, and FIG.
This figure shows three examples of video tracks on a magnetic tape in which pilot signals are multiplexed onto video signals, and FIG. 3 is a circuit block diagram showing one embodiment of a tracking error detection device according to the present invention.

In FIG. 1, a magnetic tape 1 is driven by a capstan 2 and runs in the direction of the solid arrow. This capstan 2 is rotationally driven by a capstan motor 3. On the other hand, two video heads 5 and 6 attached to the disk 4 at a distance of 180 degrees from each other are driven by a disk motor 7 (rotating in the direction of the dashed arrow). It is attached to a rotary shaft, and is driven to rotate at the frequency of the vertical synchronization signal of the recording video signal.

Further, the tape 1 is wound around the disk 4 over approximately a little over half a circumference.

Therefore, the video heads 5 and 6 alternately scan the tape 1 in diagonal directions from bottom to top, and record the video signal on each video track in units of one field of the video signal.

The video heads 5 and 6 have different azimuth angles, and therefore can perform high-density recording without providing a guard band, as shown in FIG.

First, at the time of recording, the Eirin signal applied to the terminal 8 and the pilot signal generated at the pilot signal generation time wI9 are added by the adder 1o, then amplified by the recording amplifier 11, and then sent via the rotary transformer 12. The signal is supplied to video recorders 5 and 6 and recorded on a video track on tape 1.

As this pilot signal, the true 4 frequencies of each
An example of a video track pattern when an FK type pilot signal is used is shown in Fig. 182.

In FIG. 2, A1 and A2 are video tracks recorded by the video head 5, and B1 and B2 are video tracks recorded by the video head 6. Also f1~.
f4 indicates the frequency of the pilot signal recorded on each video track.

In this way, four-frequency pilot signals are alternately recorded for each video track. The frequencies of these pilot signals are selected to be lower than the frequency band of the video signal and so low that they are not affected much by the azimuth angle of the video hects 5 and 6. Therefore, when the video heads 5 and 6 scan the recording video track during playback, it is possible to detect not only the pilot signal of the video track that is being correctly scanned, but also the pilot signals from the video tracks adjacent on both sides. can. Therefore, by detecting the reproduction levels of the pilot signals from both adjacent tracks, it is possible to obtain an accurate tracking error signal that includes the direction and magnitude of tracking deviation, as will be described later.

Next, the operation during playback will be explained. In FIG. 1, the rotational phase of the video head 5.6 is detected by the tack head 13,
This detection signal is sent to the phase adjustment circuit 14, which outputs the head phase detection signal 8W and the reference signal RB at the terminal 15.
A phase comparator 16 compares the phase of the video head 5.6 with the reference signal RE, and supplies the phase error signal to the disk motor 7 via the motor drive circuit 17.
Rotate at a constant phase and speed determined by F. If the frequency of this reference signal RP)F is selected to be approximately equal to the frequency of the vertical synchronizing signal 3 of the recorded video signal, the rotational speeds of the video heads 5 and 6 will be approximately equal to that during recording.

By controlling the running of the tape 1 using the tracking error signal while the video heads 5 and 6 are rotated at a predetermined speed, the video heads 5 and 6 can accurately scan the desired recording video track. Tracking control is performed so that Next, this tracking control operation will be described.

First, the rotational speed of the capstan 2 is detected by the speed detector 18, and this detection signal is sent to the frequency discriminator 19 to be converted into a speed control voltage SP according to the rotational speed, and this voltage 8P is added to the addition a21. By supplying power to the capstan motor 3 via the motor drive circuit 22, speed control is performed so that the capstan 2 rotates at a predetermined speed. Note that 20 is a speed setting circuit.

On the other hand, the signal reproduced from the tape 1 by the video head 5.6 is sent to the preamplifier 2 via the rotary transformer 12.
3# is sent and amplified. This amplified reproduction signal R
F is further sent to the video signal reproduction circuit 24 to become a desired reproduction video signal, and is also sent to the tracking error detection circuit 26 via the low-pass filter 25.

The low-pass filter 25 removes the high-frequency video signal from the reproduced signal RF, and only the pilot signal PL is separated and extracted. From this pilot signal PL, the tracking error detection circuit 26 forms a tracking error signal TR using the method described in FIG. 3 below.

This tracking error signal TR is sent to the adder 21 via the first switch 29, added to the speed control voltage SP, and sent to the capstan motor 3 via the motor drive circuit 22.
The rotation of the capstan 2 is controlled by supplying the same. As a result, the running phase of the tape 1 is controlled according to the tracking error signal TR, and tracking control is performed so that the video heads 5 and 6 correctly scan the video tracks. Note that 41 is a gate signal forming circuit.

Next, an example of forming the tracking error signal TR from the reproduced pilot signal PL will be described with reference to FIG.

Now, the frequencies of the four-frequency pilot signal shown in Fig. 2 are fl-10, 5fH+, fz-9-5fn + 1
3=6.5fu+f4=7.5fH (here, h is the frequency of the horizontal synchronization signal of the video signal), video track A1. When scanning A2, if the tracking shifts to the right, the fx - h - fs - f4 = h component increases, and if the tracking shifts to the left, ft - h - fs - f2 = III
3fH component increases. Also, when scanning video tracks Bt and Bt, if the tracking shifts to the right, fz
-h■A-f1 3. When the fH acid component increases and shifts to the left, fz-f1 fa-f3 heavy fHF! The minute increases.

Therefore, in FIG. 3, a local pilot signal F having the same frequency as the pilot signal recorded on the main video track to be scanned is generated by the pilot signal generation circuit 9 during playback, and this local pilot signal F and The reproduced pilot signal PL is sent to a mixer circuit 3o consisting of, for example, a double-balanced modulator, and a signal having a frequency that is the difference between the frequencies of the two signals, that is, a composite signal of the fn component and the three fm components, is obtained at its output. . Next, from this composite signal, band pass filters 31 and 32ζ are applied. The fa acid component and the 3fH component are separated, and the envelope detection circuits 33 and 34 generate voltage signals P1 . After P2, the difference between the two is determined by the differential amplifier 35, and the differential voltage signal T, T, between the five components and the 3fH component is obtained as the differential output. The differential voltage signals T, T represent the level difference between pilot signals detected from adjacent tracks on both sides of the main track to be scanned.

At this time, when the main track is Al or phantom.

B1 or B! As described above, the direction of increase/decrease of the difference frequency signal with respect to the direction of tracking deviation is opposite to the case of . Therefore, the differential amplifier 35 outputs two signals with different polarities.
two differential voltage signals k(Pt-P2)mT, k(P2-
Ps) m T , (k: constant) is outputted, each of these differential outputs T and T is supplied to the gate circuit 3637, and the head phase detection signal SW and this are sent to the inverter circuit 4.
By using signals with opposite polarity at 0 as gate signals GT and GT, and gating them during each high level period of the respective date signals GT and GT, differential voltage signals with different originalities for each track are connected. , a continuous correct tracking error signal T is obtained.

Note that in FIG. 3, the gate signal forming circuit 414 is also composed of the second switch 38 and the inverter circuit 39. This second switch 38 is switched to the contact 1 side during normal playback as described above.

Next, the operation at the time of search will be explained. First, in Figure 1,
The speed setting circuit 2 therefore sets the rotational speed of the capstan 2 so that the running speed of the tape I is around a predetermined speed faster than that during recording. Next, the first switch 29 is switched to the contact 2 side, and the head phase detection signal SW, which is the output of the phase adjustment circuit 14, is transferred to the pulse generation circuit 27.
A sample link pulse 8 is generated at a predetermined point of the signal SW, and this pulse 8 is sent to the sample hold circuit 2.
Send to 8. A tracking error signal TR, which is the output of the tracking error detection circuit 26, is added to the sample hold circuit 28, and this tracking error signal T
R is sampled and held by a sampling pulse 8, and a tracking error signal TH at a predetermined time point is output. This sampled and held tracking error signal TH is transferred to the first switch 29. Adder 21. By applying it to the capstan motor 3 via the motor drive circuit 22, the rotation of the capstan 2 is controlled, and the running phase of the tape I is controlled so that the position where the noise bar is generated is fixed during the search.

Next, a method of fixing the generation position of a noise bar during a search will be explained. First, a case of 5x speed search in the fast forward direction will be explained as an example. In this case, the first switch 29 is switched to the contact 2 side and the second switch 38 is switched to the contact 1 side in FIG.

and the scanning trajectory of the video hects 5 and 6 when the tape 1 is run at 5x speed in the fast forward direction. In FIG. 4, solid lines indicate recording video tracks, broken lines indicate scanning trajectories of the video heads 5 and 6 during fast-forward playback, and diagonal lines indicate positions where noise bars occur. This noise bar is generated when the video hects 5 and 6 scan a track recorded at an azimuth angle different from the azimuth angle of the video hector 5, 6.

Assuming that the video head 5.6 always accurately scans the video track with the same azimuth angle when it starts scanning the tape 1 as shown in Figure 4, the time at which the noise bar occurs is is always constant, and therefore the position of the noise bar on the playback screen is fixed.

Next, in Figure 5, like the fourth factor, in the fast forward direction, 5f1!
A timing chart showing the signal waveforms of each part when tape 1 is running and playing at high speed? 'be.

In FIG. 5, C, (1) is the tracking error signal TR at the time of search, and the signal TH1 (2) obtained by sampling and holding this error signal TR is a pulse pulse based on the rising and falling points of the head phase detection signal 8W. The sampling pulse S1(3) generated once by the generation circuit 27 is a head phase detection signal sw as a gate pulse GT.
(4) is a local pilot signal F generated by the pilot signal generation circuit 9 and applied to the mixer circuit 30.

- The high level (H) period of the rad phase detection signal SW is the period during which the video hector 5 is scanning the tape l,
The low level (L) period is a period during which the video head 6 is scanning the tape 1. The point in time when this signal SW switches from H to L and the point in time when it switches from L to 1 corresponds to 4u when the video heads 5 and 6 start scanning the tape 1, respectively.Every time the level of this signal SW switches, , a sampling pulse S shown in FIG. 5(2) is formed directly at the switching point, and this pulse S samples and holds the tracking error signal TR as shown in FIG. 5(1), as shown by the broken line. An error signal TH shown is obtained.

The horizontal axis of the tracking error signal TR shown in FIG. 5 (1) indicates the time axis. As shown in the figure, if the l track pitch is P and the scale is scaled on this time axis, the video head will move on the tape l. It also represents the amount of tracking deviation at the time when scanning starts. Further, the connecting axis is the voltage value of the error signal TR.

If the tracking is shifted to the left at the time when the video heads 5 and 6 start scanning as shown at points A and B in FIG. 4, for example, 'V'A in FIG.
, V'r=, the voltage of the tracking error signal TR increases. Conversely, if it deviates to the right, the error signal T
The voltage across R drops.

When the video head 5.6 starts scanning, if the recording track is correctly scanned, a five-component signal P1
and the signal P2 of the a f>+ component become equal, and the voltage of the tracking error signal TR, which is the difference No. 1, becomes VA and VB, respectively, which are equal to the average value, as shown in FIG. 5 (1).

Now, as shown at point B' in Fig. 4, the local pilot signal F
is the period fl, and if the tracking is shifted to the left at the time when the video head 6 starts scanning the tape 1, that is, if the running speed of the tape 1 is slow, then fl-fa -5fa component signal P2 is small
, fl-fl-fr (component signal P1 is dominant,
The voltage of the tracking error signal T, which is the difference signal, is
The height increases as shown at 6 in FIG. 5(1). Therefore, the tracking error signal TH sampled and held at this point also becomes high. Therefore, in the adder 21, the control voltage PH, which is the sum of the speed control voltage SP and the tracking error signal TH, also becomes high, the motor drive power of the drive circuit 22 increases, and the rotation speed of the capstan motor 2 increases. , the tape running speed becomes faster. On the other hand, when the tracking is shifted to the right, that is, when the tape running speed is high, the signal P of the 3fH component among the frequency difference components
2 increases, and the voltage of the tracking error signal TR drops. Therefore, the control voltage PH applied to the drive circuit 22 drops, and the cab stamina slows down.

By controlling in this manner, it is possible to keep the tape running speed constant, and also to cause the video head 56 to correctly track and scan the recording sickle track at the time when it starts scanning on the tape 1, and as a result, the speed in the fast forward direction During the 5x speed search, it is possible to fix the position of the noise bar.

Next, the search in the rewinding direction will be explained.

The sixth figure shows the running trajectory of the video heads 5 and 6 when the tape 1 is run at five times the speed in the rewinding direction and the sickle video track on the tape 1. In Fig. 6, the solid line indicates the recorded video track, the broken line indicates the travel trajectory of the video head 5.6 when rewinding and playing back at 5x speed change, and the diagonal line indicates the position where the noise bar occurs. Similarly to the case of fast-forward playback at 5x speed, when the video heads 5 and 6 are alternately correctly scanning the video tracks having the same azimuth angle at the start of scanning.

The position of the noise bar is fixed. Also, in FIG. 7, (1) shows the tracking error signal TER during the search and the signal TH obtained by sampling and holding this error signal TR.
, (2) is the sampling pulse S, and (3) is the signal 8W1 (, i) of the opposite polarity of the head phase detection signal SW as the gate pulse GT is the local pilot signal F.

In the case of this rewinding and 5x speed playback, as shown in FIG. 7(1), at the start of scanning of the video heads 5 and 6, as the tracking shifts to the right, the voltage of the tracking error signal TR increases, and the voltage of the tracking error signal TR increases, as shown in FIG. For tracking control, it is necessary to operate the signal TR so that the voltage of the signal TR decreases as the signal shifts to the left. The direction of increase/decrease in the tracking error signal TR with respect to the direction of the tracking deviation is opposite to that in normal playback and fast-forward playback. Therefore, in rewinding playback, the second switch 3 shown in FIG.
8 to the contact 2 side and the inverter circuit 39 applies gate pulses ()T, G to the gate circuits 36 and 37.
By reversing the polarity of T, the polarity of the tracking error signal TR is reversed. In this case, the rotation rate of the local pilot signal F generated by the pilot signal generation circuit 9 and applied to the mixer circuit 30 is set to f4.
It is necessary to reverse fa-fl and fl.

Now, as shown at point B in FIG. 6, when the pilot signal F is in period f4 and the tracking is shifted to the right at the time when the video head 6 starts scanning on the tape 1, that is, when the tracking is shifted to the right, If the running speed is slow, fa
- There is almost no signal P1 of the fs-fu component Φ, and f4-
The fl-3fH acid component signal P2 becomes dominant, and the voltage of the tracking error signal TR, which is the difference signal therebetween, becomes high as shown by VB in FIG. 7(1). Therefore, the tracking error signal TH sampled and held at this point
It also becomes more expensive. Therefore, the control voltage PH applied to the drive circuit 22 increases, the rotational speed of the capstan motor 2 increases, and the tape running speed increases.

If the reverse tracking is shifted to the right, i.e.
When the tape running speed is high, the five-component signal P1 increases and the voltage of the tracking error signal T decreases. Therefore, the control voltage PH applied to the drive circuit 22 drops, the rotation of the capstan motor 2 slows down, and the tape running speed slows down.

By controlling in this manner, the tape running speed can be kept constant and the video head 56 can correctly track and scan the η recording track at the time when it starts scanning on the tape 1. As a result, When searching at 5x speed, it is possible to fix the position of the noise bar on the playback screen.

Next, FIG. 8 is a circuit block diagram of a tracking error detection device showing a second embodiment of the present invention. FIG. 7 is a diagram illustrating an example of a configuration in which control is performed to fix the generation position of a noise bar. Figure 9 also shows how the equipment shown in Figure 8 can be used to increase heat resistance as shown in Figure 4.
7 is a timing chart showing signal waveforms of various parts when fast forward playback is performed at double speed.

In FIG. 8, 27' is a pulse generation circuit, and the third
This circuit block corresponds to the pulse generation circuit 27 of the first embodiment shown in the figure. The head phase detection signal SW shown in FIG. 9(7) is added to the mono-multi circuit 42 constituting this pulse generating circuit 27', and a rectangular wave signal M with a duty ratio of approximately 50 degrees as shown in FIG. 9(5) is generated. is formed. This signal M is applied to the pulse generating circuit 43, and a pulse 81 shown in FIG. 9(3) is generated. On the other hand, the square wave signal M is
The polarity is inverted by the inverter circuit 44, and the ninth
A rectangular wave signal M shown in FIG. 6 is formed. This signal M
From this, the pulse generating circuit 45 generates a pulse S2 shown in FIG. 9(4). The sampling pulse S shown in FIG. 9(2) is formed by the OR circuit 47 from this pulse S2 and the above pulse S1.

On the other hand, the output signal M of the mono multi-circuit 42 and a signal M having a layer opposite thereto are applied to the contacts 2ζ of the fourth switch 48 via the switch @3.

Contact 1 of this switch 48 has a head phase detection signal SW.
is added, and during normal playback, the signal S on the contact 1 side
W is selected and supplied to the tracking error detection circuit 26 as a gate pulse GT. The operation during normal reproduction is as described in the first embodiment.

The switch 46 is a switch that can be changed when searching in the fast forward direction and when searching in the rewinding direction.When searching in the fast forwarding direction, the signal M is selected, and when searching in the rewinding direction, the signal M is selected. pulse gt
The signal is supplied to the tracking error detection circuit 26 as a signal.

Now, switch 46 in Fig. 8 is set to contact 1 open, switch 4
8 is switched to the contact 2 side, and tape 1 is run at five times the speed in the fast forward direction as shown in FIG. 4, gate circuits 36 and 37 close the high level period of signals M and fH output from the differential amplifier 35ρ)
The difference voltage signals T and 'r of the acid component 3fH component are alternately gated every four fields, and the tracking error signal TR shown in FIG. 9(1) is obtained. The rotation frequency of the local pilot signal F to be applied to the mixer circuit 30 is as shown in FIG. 9 (8).

In this way, when playing fast forward at 5x speed, #! When using the gate pulse GT formed by the device shown in FIG.
), the tracking error signal TR changes in the same way between the period in which the video head 56 scans the first half of the video track and the period in which it scans the second half. this is,
When the tape 1 is running at a predetermined search speed and the position of the noise bar is fixed, for example, as shown in FIG. 4, the video head 6 accurately scans the track on which the pilot signal of frequency f2 is recorded at the scanning start point B. This is because the track in which the pilot signal of the frequency M is recorded is accurately scanned at the midpoint of the video track, and thereafter the scanning rate of the video track on the right changes in the same way.

During this one field period, a signal with a frequency f2 is applied to the mixer circuit 30 as a local pilot signal F, but the signals of the ft-f4 and 2f components are fy and 3.
Since the signal is attenuated by the fH bandpass filters 31 and 32, there is no particular effect when the main track changes from f2 to f4. However, the first half of the scan gradually becomes f2-fs-3f.
While the H component signal P2 increases, in the latter half of scanning, the f2-fx■9 component signal Pl gradually increases, so that the polarity of the tracking error signal TR with respect to tracking deviation becomes reversed. Therefore, by using the rectangular wave signal M shown in FIG. 9(5) as the gate signal GT as shown in FIG. 8, the h-component signals P1 and 3 are
Signals T and T having opposite polarities, which are difference signals from the fH component signal P2, are selected, respectively, to obtain a tracking error signal TR with a field period as shown in FIG. 9(1).

Therefore, from FIG. 9(1), at the time when the video head 5.6 starts scanning and when scanning the middle point of the video track, the voltage of the tracking error signal TR increases as the tracking shifts to the left, and vice versa. At the time when the error signal point and the track midpoint are scanned as the error signal shifts to 1, the sampling pulse S shown in FIG.
The tracking error signal T of 1) is sampled and held, and the capstan motor 3 is controlled by the sampled and held error signal TR, thereby controlling the running phase of the tape 1 so that the position where the noise bar is generated is fixed. In addition,
The operation of sample-holding the tracking error signal TR at the scanning start point and fixing the noise bar generation position is as explained using FIGS. Since the principle of operation when sample-holding is also the same, detailed explanation will be omitted. Furthermore, the position of the noise bar can be fixed even in the case of five-times speed playback in the rewinding direction in which the switch 46 in FIG. 8 is switched to the contact 2 side. This place □
The operation at this time can be inferred from the operation at the time of 5x speed playback in the fast forward direction, so the explanation will be omitted.

As in the second embodiment shown in FIG. 8, it is better to sample and hold the tracking error signal T twice per field to control the position of the noise bar.
Compared to the case where the error signal TR is sampled only once per field as in the first embodiment shown in the figure, the phase control of the tape 1 is corrected more frequently, resulting in more stable and accurate position control of the noise bar. becomes possible. In addition, the present invention is based on this #! The first and second embodiments are not limited to the number of samplings described in the examples, but can also be modified such as by making the sampling period longer than in the first embodiment, or by making the sampling period shorter by 1 than in the second embodiment. This is also effective when increasing or decreasing the number of samplings per hour.

Next, a third embodiment of the present invention will be described using FIGS. 10 and 11. In the above embodiments, the TrlA double-speed search was explained, but the third embodiment shows a method of fixing the generation position of the noise bar in the case of an even-numbered double-speed search. As an example of this even-numbered speed search, 4x fast-forward playback will be described below.

FIG. 10 depicts the recording video track on the tape 1 and the scanning trajectory of the video heads 5 and 6 when the tape 1 is run at 4x speed in the fast forward direction. In FIG. 10, solid lines indicate recording video tracks, broken lines indicate the scanning locus of the video head during fast-forwarding and quadruple speed playback, and diagonal lines indicate the positions where noise bars occur. As in the case of the odd-numbered multiple speed search, when the video heads 5 and 6 start scanning the tape 1, the position where the noise bar is generated is fixed while the video heads 5 and 6 are correctly scanning the sickle video track alternately. However, in the case of this even-numbered multiple speed search, unlike the odd-numbered multiple speed search, at the start of scanning, one of the video heads 5, 6 scans on a recording track with the same azimuth angle as that of the other head, and Since the head scans a recording track with an azimuth angle different from that of the head, the number of noise bars appearing on the playback screen is twice as many as in the odd-numbered multiple speed search.

Also, Fig. 11 shows 10a! ! 1 is a timing chart showing signal waveforms at various parts when the tape 1 is played back by running it at four times the speed in the fast forward direction as shown in FIG. In FIG. 11, (1) is the tracking error signal TR at the time of search.
and a signal T obtained by sampling and holding this error signal TR.
H1(2) is the sampling pulse 8. In (3), the head phase detection signal 5W1 (4) is the local pilot signal F.

In the case of this fast forward quadruple speed playback, the local pilot signal F to be added to the mixer circuit 30 in FIG.
As shown in FIG. 11 (4), a pilot signal of frequency fx is always used, and in FIG. When the gate circuit 37 is turned off and the gate circuit 37 is always turned on, the tracking error signal TR at this time becomes a signal that changes with the field period as shown in FIG. 11(1).

Therefore, if the tracking is shifted to the right from the target video track where the pilot signal of frequency f1 is recorded when the video head 6 starts scanning the tape 1, as shown at point B in FIG. That is, when the running speed of the tape 1 is high, the voltage of the tracking error signal TR becomes low as shown by VB in FIG. 11(1). Therefore, the tracking error signal TH sampled and held at this point also becomes low.

The rotational speed of the capstan motor 2 decreases, and the tape speed decreases. Conversely, when the tracking is shifted to the left, the tracking error signals TR and TH become high and the tape speed increases.

By controlling in this way, the tape running speed is kept constant during the quadruple speed search in the fast forward direction, and the video head 5.6 correctly moves on a predetermined recording track when it starts scanning on the tape 1. Tracking scanning can be performed, and the position of the noise bar on the playback screen can be fixed.

Although the examples of the 5x search in the fast forward direction and the rewind direction and the 4x search in the fast forward direction have been described above, the present invention is not limited to these examples, and the present invention is not limited to these. It can be applied to playback by running at an arbitrary integer multiple speed.

Further, in the above embodiment, the case where the video head 5.6 is controlled to accurately scan the recording track at the time when it starts scanning, but it is controlled to accurately scan the recording track at any point after the start of scanning. The present invention is also effective when controlling to scan. Further, the local pilot signal F and gate signal GT can also be changed as appropriate from the settings in the above embodiment.

Furthermore, in the above embodiment, a method was explained in which pilot signals of four different frequencies are recorded alternately for each video track, but a method using pilot signals of three or five or more frequencies may be used. For example, in the case of a method of recording 4 pilot signals of a constant frequency with different phases for each video track, or recording a continuous lζ pilot signal on a video track, for example, the horizontal retrace of a television receiver is used. The present invention can also be applied to a method in which the phase and recording timing of a one-frequency signal are intermittently varied only during a predetermined period within a period, and the temporal and spatial arrangement is changed for each video track. be.

As described above, according to the present invention, m! Since a continuously accurate tracking error signal can be obtained by reproducing pilot signals with different frequencies or phases or different temporal and spatial locations (convergence of m≧3), it is possible to obtain sufficient tracking error signals even during long-term recording. Automatic tracking control of performance has been achieved, and by controlling the running phase of the magnetic tape according to a signal obtained by sampling and holding the tracking error signal at a predetermined point in time during a search, the position of noise bar generation during a search is fixed, and playback is improved. The screen becomes noticeably easier to see.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the configuration of a magnetic recording/reproducing apparatus according to the present invention, FIG. 2 is a tape pattern diagram showing video tracks on a magnetic tape, and FIG. 83 is a circuit block diagram showing an embodiment of the present invention. , FIG. 4, FIG. 6, and FIG. 10 are tape pattern diagrams showing the video tracks on the magnetic tape and the running locus of the video head during search, and FIGS. 5, 7, 9, and 11 are A signal waveform diagram for explaining the present invention in detail, and FIG. 8 is a circuit block diagram showing a second embodiment of the present invention. 1... Magnetic tape 2... Capstan 5.
6...Video head 9...Pilot signal generation circuit 22...Capstan motor drive circuit 26...Tracking error detection circuit 27.27'...Pulse generation circuit 28...Sample and hold circuit agent Patent attorney Susuki 1) Ri 4, Yuki 5 Ji,; ”',: ” N 7 1 Roa Z Diagram T 3 Diagram b Diagram? 7 Figure...,...' fs nio 8
figure

Claims (1)

[Claims] Rotating video head and mf that scan the magnetic tape diagonally
a circuit for generating a pilot signal of class i (an integer of m≧3); and a device for repeatedly recording the pilot signal of class mli on each video track on the magnetic tape by superimposing it on a video signal by the video head. a device for reproducing the pilot signal from the magnetic tape by the video head; a tracking error detection circuit for generating a signal according to the tracking error of the video head from the reproduced pilot signal; A magnetic recording and reproducing apparatus comprising: a device for performing tracking control so that a video head correctly scans the video track; A circuit is provided that samples and holds the tracking error signal at a predetermined time point when the video head scans a predetermined point on the magnetic tape, and supplies the sampled and held tracking error signal to a high-speed drive device for the magnetic tape. A magnetic recording/reproducing device characterized in that the generation position of a noise bar appearing in a reproduced image is fixed.