JPS59167825A - Method for generating pattern for automatic tracking of video tape recorder - Google Patents

Abstract

PURPOSE:To attain the generation of a head driving pattern with fidelity by preparing a tracking pattern and a transmission pattern as basic patterns in a pattern generator at the reproduction and combining an error pattern and the basic patterns so as to obtain a driving pattern. CONSTITUTION:When an output of an amplitude detector 14 is larger than an output of 14b at the 1/4 slow reproduction, it is meant that a video head 3a is biased toward a video track 2b on which a pilot signal f2 is recorded. Then, a moving head driving signal correcting the bias is generated at a pattern generating circuit 17 based on an output of a comparator 15 and a VTR operating mode signal 16 reprosenting the slow reproduction or the like. Further, the signal is smoothed by an LPF 18a smoothing it to a degree that an abnormal vibration is not produced to a piezoelectric element 4a and applied to the piezoelectric element 4a via a moving head driving amplifier 19a. As a result, the balance of the amount of crosstalk of a pilot signal from an adjacent track reproduced by the video head 3a is changed so as to form a servo loop, allowing to improve the tracking performance.

Description

[Detailed Description of the Invention] This invention relates to a video tape recorder (hereinafter referred to as VTR).
This invention relates to an improvement in the automatic tracking pattern generation section using a movable head.

In the helical scanning method v'ra, stationary
The video track recorded during slow playback or high-speed playback does not match the video head trajectory. Because of this, the playback image quality deteriorates, so the conventional method is to mount the video head on a piezoelectric element and match the video track and video head trajectory to obtain good image quality.Automatic tracking using a movable head (hereinafter simply referred to as AT). The AT methods include an absolute phase method that uses control pulses and the PG signal of the capstan motor, and a pilot signal method that uses pilot signals recorded at different frequencies for each video track (four types of pilot frequencies are used). (It is also called the 4f method because it is used by switching sequentially.) Here, the 4f method will be explained as an example.

The videotape pattern in the 4F system is shown in Figure 1.
Figure 2 shows the AT system block diagram, Figure 8 shows an example of the relationship between the fixed head and video track during 1/4 slot playback, and Figure 8 shows an example of the movable head drive pattern during 1/4 slot playback. FIG. 4 shows an example of a pattern memory for creating a movable head drive pattern using a conventional method, and FIG. 5 shows an example of a movable head drive pattern.

In the figure, (1) is a video tape, (2) is a video track, (8a) and (8b) are video heads attached to opposite ends of a rotating cylinder, (4a) and (4b), respectively.
) are piezoelectric elements with video heads (8a) and (8b) attached respectively, and (5) are video heads (8a) and (8b).
Head switching signal (H-8W
), (6a), (6b) are video heads (8a)y(8
The reproduced signal obtained by b), (7a) and (7b) are amplifiers, (8) is a switch circuit for selecting the reproduced signal (6aL (6b)), (9) is a filter for extracting the pilot signal, and aQ is Regenerated pilot signal P), cI
η is the carrier signal σcR), (b) is the balanced mixer, (1
8a), (18b) are band pass filters, (14a),
(14b) is an amplitude detector, (G) is a comparator, 06 is a VTIt operation mode signal, ση is a movable head drive pattern generator, (18a), (18b) are low-pass filters, (19a), ( 19b) are piezoelectric elements (4a), (4b
), (4) is the trajectory when the movable head is fixed (called the fixed head trajectory), and υ is the head trajectory on the videotape during normal recording and playback (usually called the head trajectory). ), (sha) is the speed vector for the normal playback speed (called the normal playback speed vector), (c) is 1
The velocity vector for the /4 slow playback speed (called the 1/4 slow one-speed inverse vector) is the head trajectory on the videotape during 1/4 slow playback (called the 1/4 slow temporary head trajectory). ), Ya is the movable head drive pattern during 1/4 slot playback, Kan is the movable head drive pattern during stationary playback (referred to as still pattern), and 127) is the pattern corresponding to tape movement (referred to as tape movement pattern). ),
4 is still pattern memory, - is tracking error memory (hereinafter simply referred to as error memory), r, 3
is a drive pattern memory.

Next, the operation will be explained. In Fig. 1, the pilot signals f, ft, f, f, recorded using the 4f method of a helical scanning VTR are each 102KH.
z, txsKHz, 164K) (Z, 148K
H2 is a sufficiently low frequency compared to the Y signal and C signal, and the difference between adjacent pilot signals is set to a predetermined value such as 16 KHz and 46 KHz. -f and f3 are on one azimuth (CH1 head) side,
ft and f are superimposed on the video track on the other azimuth (CH2 head) side. In FIG. 2, video heads (8a) and (8b) have different azimuths and are attached to ends (180° position) opposite to the fourth eye of a rotating cylinder. (Not shown.) The video head (8a),
(ab) are piezoelectric elements such as bimorph (4a), (4b)
The movable head 9 is attached to the top of the rotary cylinder and is configured to be movable in a direction perpendicular to the rotating surface of the rotary cylinder. Video head (8a) and (8b)
It is assumed that when the switching signal (H-SW) (51) is "H", the video head (8a) is in the recording/reproducing state. That is, the video head (8a).

(3b) are respectively the CHI side and the CH2 side. Assume that the video head (8a) is now tracing the video track (2a) on which the pilot signal f1 is recorded. Pilot signals f2 and f4 recorded on adjacent tracks are mixed into the reproduced signal (6a) as a crosstalk signal. The reproduction signal (6a) is amplified by the reproduction amplifier AMP 1 (7a), and the reproduction pilot signal fPQ (I is obtained by the filter LPF8 (9) which selectively passes the pilot signal through the switch sw (ski). fPαO includes crosstalk with fl and this ft, f4.Carrier signal f
Set to the same frequency as cR (1ηt-ft, fPOLI
I and fcRQη in a balanced mixer MIX02. MIXQ2 (7) For the output, l ft-f+ i =
46KHz and 1ft-ftl=1aKHz components are generated. Center frequency 16 KHz and 46 KHz (7) Bandpass filter BPF 1 (113a) and BrF3 D
8b) Extract the D component and convert the detection circuit DTI (
14a), converted to DC level by DT2 (14b),
Each is compared by a comparator COMP(g). If DTl
If the output of (14a) is similar to DT2 (tab), it means that the video head (8a) is biased toward the video track (2b) where the pilot signal f2 is recorded. Pattern generation circuits P and T, which are composed of microcomputers, etc., generate movable head drive signals for correcting unevenness of the gap, as well as VTR operation mode signal signals indicating output, normal playback, static playback, slow playback, etc.
, Gαη, the movable head drive signal is smoothed by a low-pass filter LPF 1 (18a) that smooths the movable head drive signal to such an extent that the piezoelectric element (4a) does not generate abnormal vibration, and the movable head drive amplifier HDI (19a) is smoothed. A piezoelectric element (4
a). As a result, the balance of the amount of crosstalk between pilot signals from adjacent tracks reproduced by the video head (8a) changes, and a servo loop is formed. Further, the same applies to the CH2 side. Although the explanation is omitted here, the video head (sa), (8
The capstan motor control system is also operated to reduce the signal for correcting the bias in b).

Next, the control of the movable head in slow playback will be explained. In FIG. 8, the normal head trajectory can be expressed as a composite vector of the trajectory of the video head (8a) or (8b) and the normal playback speed vector 4. Therefore, if the video tape (1) moves at the same speed as during recording, the normal head trajectory remains parallel to the video track (2). However, when the moving speed of the videotape is reduced to 1/4, a 1/4 slot temporary head trajectory is obtained as a composite vector of the 1/4 slot speed vector 1/4 vs. the glance. Also, this 1/4 slot temporary head trajectory (241 is a video tape (
With the movement of 1), (24a), (24b),
It changes like (24c), o and (24d),
In order to obtain a good signal, the piezoelectric element (4a) is displaced and the video head (8a) is moved to the head trajectory &1 during normal playback.
Must match 1. 1/4 slot temporary head trajectory (24a) in FIG. (24d)
In Fig. 4, the video head drive pattern for
1/4 slot playback head drive pattern (25a) ~ (
25d). These 1/4 slot one playback head drive patterns (25a) to (25d) are l-1-8W (2
A tape movement pattern corresponding to the movement of the video track (2a) and a triangular steal pattern that becomes -IP in 1/2 period of 19. It is obtained by combining with η.In the conventional 4F system, the tape Since no external signal is used to create the movement pattern (271), the tape movement pattern penalty must be obtained from a signal corresponding to the amount of mistracking.

Therefore, P, T, and Ga4 in FIG. 2 are configured with a microcomputer, etc., and one field as shown in FIG. 5 is divided into eight, for example, and still pattern memory, error pattern memory, and It has a drive pattern memory 0υ for driving the movable head,
The tape movement pattern I271 is made to correspond to the contents of the error pattern memory. For example, consider block 4. 4th content o4 of driving pattern memory c])
is composed of the sum of the fourth contents of the still pattern memory and the error pattern memory, 04=P, +1.・・・・・・・・・
...... It is expressed as (1). The result of driving the movable head with this o4 is Fig. 2 c7) DTI (15a)
(7) If the output is thicker than DT2 (15b), the video head (8a) must be lowered. Therefore, it is necessary to increase the error E4 by a predetermined value. Let the current error be E< (to), and the error after correction be Mt(tt).
, if the predetermined value is α, then H4(tl) = h=< (
to) + a re-song--(2).

Conversely, if the output of DTI (15a) is small, H4(it
) = H4(t6)-α ・・・・・・Song・
... (3). The contents of the example error pattern memory thus obtained are tape movement patterns. It basically matches the sword. Figure 6 is a representation of the rotation pattern in Figure 4 using the memory in Figure 6, and the still pattern (32 ,
Error pattern - driving pattern (good).

Now, the error ha (N=1.2..., 8) is the above (
Although it is corrected by formula 2) or formula (3), it is a correction for A and A in Figure 4 and does not give BIB3. Therefore, in order to obtain a drunken melon, the tilt of the kite is calculated by △8. Then, ΔA is added to the error pattern memory corresponding to A and As. Let the contents of the error pattern memory be EN (N: 1, 2..., 8), and let the slope (A
If the difference between I and A2) is △, then EN (tl) = EN (to)±αHΔ...
It can be expressed as (4). Also, whether to move from D, B3 to E, B3 or to 2 = r A, As is determined by the obtained & (11),
If you want to move to revision, EN(tl) = EN(to)±α+2△-2P
・-Old-river=・Correct the contents of the error pattern memory as shown in (5). FIG. 7 shows an example of a four-slot temporary drive pattern using the above method. Person, →A2→凋→B1
→...→C4→D1 is necessarily a pattern based on the above equation (4), and Dt→D4-+A; is a pattern based on equation (5). In addition, in FIG. 7, the number N of divisions of one frame is set to infinity for the sake of simplicity.

Since the conventional head drive pattern during slow playback was generated by the method described above, the drive pattern is A in Fig. 7.
Acute angle portions occurred at point 2, point A4, point B2, and point 84. If a piezoelectric element such as a bimorph is driven in a pattern with such acute angles, abnormal vibrations may occur at the acute angle portions, so it is necessary to use a filter that cleans the acute angle portions. Also, please check the error pattern,
Since the driving pattern must be predicted and determined, this predictive calculation takes time, and the number of divisions of one field cannot be increased.

This invention was made in order to eliminate the drawbacks of the above-mentioned conventional devices.The speed of slow playback is set in advance by a controller that controls the operation mode of the VTR, or the tape speed is detected, and a basic drive pattern corresponding to the speed is set. is programmed into the microcomputer that constitutes the entire pattern generation circuit, and generates a driving pattern that is a combination of the above basic driving pattern and an error pattern representing the amount of mistracking, and reduces the number of smoothing filters. It is an object of the present invention to provide a movable head AT device for a VTR that can generate a good drive pattern by increasing the number of divisions of one field.

An embodiment of the present invention will be described below with reference to the drawings. 8th
In the figure, (8a) to (19b) are the same as those in FIG. 2, the digit is the basic pattern selection section, ←1 is the tape speed signal, and (4 is the basic pattern selection signal).

FIG. 9 is a diagram of the internal pattern memory of P, T, and Gαη according to the present invention, and is an example of a 1/4 slow pattern.

(48a) to (48d) are patterns for video track tracing (referred to as tracking patterns); (44a)
(44d) is a memory containing a pattern (referred to as a forwarding pattern) for moving the video head to the starting point of the next tracking pattern (c). The error pattern memory and drive pattern memory o are the same as those shown in FIG.

Next, the operation will be explained. Basic pattern selection section (6)
generates a basic pattern selection signal O4 corresponding to the VTR operating mode signal a. and tape speed signal U. According to this basic pattern selection signal 02, 9, P, T.

Goη selects a predetermined basic pattern 0, e.g. 1/4
``If it is the slow playback mode, 1/4 slow pattern memory (c), 1 fathom is selected within the P, T, and Gα forces. The 1/4 slow pattern is shown in FIG.

In the figure (45a) to (45d), (46a) to (46
d) is the tracking pattern (48a) to (4) in FIG.
8d) corresponds to the forwarding patterns (44a) to (44d). Again A4, A2, B1
, B2, C1, C2, B4, DI, B, and A2 indicate parts similar to those in FIG. As is clear from FIG. 10, only the acute angle portions A, , 81, etc. of the basic pattern according to the present invention are considerably improved compared to the portions 4 t B, etc. of FIG. 7. ing. Note that although the forwarding patterns (44a) to (44d) were made linear, A2. It is also possible to create a pattern that allows sharp edges such as B to be made smoother.

The actual driving pattern is obtained by combining the basic pattern and the error pattern. An example of this is shown in FIG. In the figure, f41, t461, and f471 are examples of the basic pattern, error button, and drive pattern according to the present invention, respectively. Tracking drive pattern (47a)
tOα1,0α2. ..., Oα8, if the forwarding drive pattern (47b) is Oβ1, 0β2+”'10β8, then 0αN-PAN+EN (N-1, 2,
..., 8)... (6) O voice-P, IN+Eq-N
(N-1, 2, . . . , 8) (7). However, what should be noted here is AI A2 + A2
Drive pattern (47a) corresponding to B11 BI B2
, (47b), (47c) as 0txN, 0
βN e 07N + error pattern (46a), (4
6b), (46c) as EαN′ + EpN + E7
This point is set as N. In this way, by making the error pattern (46b) for correcting the forwarding pattern (45b) and the error pattern (46c) for correcting the following tracking pattern (45c) the same and reversing the order, the video head The forwarding drive pattern and the video track tracing drive pattern are especially B.
The advantage of extremely natural connection in part 1 was obtained, and the drawbacks of the above-mentioned conventional methods could be overcome. In addition, since the error pattern can be obtained by simply correcting a predetermined tracking error value, there is no need to predict the error pattern, which shortens the time required to generate a lever turn, making it possible to generate finer patterns. became.

In addition, although only the Cf41 side was explained in the above-mentioned example, the same applies to CH29111. Also, CHI
The explanation was made assuming that and CH2 have different azimuth angles, but
A similar effect can be obtained even when the azimuth angles are the same. Also, although the explanation was given using 1/4 slow playback as an example,
/2, 1/4, '1/8 slow playback, reverse direction (7
) It goes without saying that reproduction at other speeds such as 1/2, 1/4, and 1/8 slot playback is also effective.

It is also effective when the conventional method is used in conjunction with static playback or very slow slow playback. Furthermore, although a piezoelectric element has been described as an example of an electromechanical displacement transducer, it goes without saying that other types such as a moving coil may also be used.

Further, although the case where one field is divided into eight parts has been described, it goes without saying that the number of divisions may be larger or smaller than eight. Furthermore, although the VTR system has been described as a 4f system, it goes without saying that a system in which an error pattern is obtained by increasing or decreasing the level of the reproduced video signal may also be used.

As described above, according to the present invention, a tracking pattern and a forwarding pattern according to the playback speed are prepared as basic patterns in the auto-tracking pattern generator,
The driving pattern of the movable head is obtained by combining the error pattern indicating the amount of mistracking with the above-mentioned basic pattern, so that a very smooth and accurate movable head driving pattern can be generated. Moreover, this can be expected to improve tracking performance, and furthermore, a filter for preventing abnormal vibrations of actuators such as piezoelectric elements can be easily provided.

[Brief explanation of the drawing]

Figure 1 is a principle diagram showing the videotape recording pattern in the 4F system, Figure 2 is a conventional AT system block diagram, and Figure 8 is a block diagram of a conventional AT system.
The figure shows the principle of the relationship between the fixed head and the video track during 1/4 slot playback, Figure 4 shows the waveform relationship of the movable head drive pattern during 1/4 slot playback, and Figure 6 shows the movable head according to the conventional method. A configuration diagram of a pattern memory for creating a head drive pattern, FIG. 6 is a diagram of the drum-shape relationship for creating a movable head drive pattern, and FIG. 7 is a diagram of waveform relationships of the movable head drive pattern during 1/4 slot playback using the conventional method. FIG. 8 is an AT system block diagram according to an embodiment of the present invention, FIG. 9 is a configuration diagram of a pattern memory diagram inside P, T, and G according to the present invention, and FIG.
The figure is a waveform relationship diagram of a 1/4 slow pattern according to an embodiment of the present invention, and FIG.
FIG. 3 is a waveform relationship diagram of a four-slot temporary drive pattern. In the figure, (1) is a video tape, (21 is a video track, (3) is a video head, (4) is a piezoelectric element, (
5) is a head switching signal, (6) is a reproduction signal, (7) is an amplifier, (8) is a switch circuit, (9) is a filter, and Q(
I is the regenerated pilot signal, αυ is the carrier signal,
(A) is a balanced mixer, (to) is a bandpass filter, C1
41 is an amplitude detector, 09 is a comparator, O is a tape speed signal, Qη is a movable head drive pattern generator, (G)
is a low-pass filter, (+9) is a movable head drive amplifier, (A) is a fixed head trajectory, ``Kiri'' is a normal head trajectory, ``Kan'' is a normal playback speed vector, and inside is a 1/4 slot speed vector. (241 is 1 /4 slot temporary head trajectory, (20 is 1
/4 slot movable head drive pattern during playback, (2I5 is still pattern, cutting η is tape movement pattern, (to) is memory for still pattern, - is memory for error pattern, 6υ is memory for drive pattern, country is still pattern,
I31 vanilla pattern, (341 is driving pattern, (
4 is the basic pattern selection section, ←l is the tape speed signal, ←
4 is a basic pattern selection signal, 03i is a tracking pattern memory, (441 is a forwarding pattern memory,
/4 slow tracking pattern, u6) is a 1/4 slow one-time feed turn, i4 cover 1/4 slow driving pattern. In addition, in the figures, the same reference numerals indicate the same or corresponding parts. Agent Makoto Kuzuno - Figure 1 2 2a, 26 - Before procedural amendment (on his own initiative) Mr. Commissioner of the Japan Patent Office 1. Case description Patent Application No. 48886/1986 2. Name of the invention Method for generating automatic tracking patterns for video tape recorders 3. Relationship with the case of the person making the amendment Patent Applicant Address 2-2-3 Marunouchi, Chiyoda-ku, Tokyo Name (601) Mitsubishi Electric Co., Ltd. Representative Katayuni Part 8 Part 5, Invention of Specification Subject to Amendment vI Part 6 of the detailed explanation of the above, Contents of amendment (1) The specification is amended as follows.

Claims (1)

[Claims] at least one pair of movable heads comprising a video head driven by a head drive actuator; an error detection device for detecting a tracking error of the movable head from a reproduction signal obtained from the movable head; In an auto-tracking video tape recorder comprising a pattern generator that generates a drive pattern for the movable head according to the operation mode of the tape recorder, and a device that drives the movable head according to the drive pattern, the operation mode It has a basic pattern in the form of integer division of one field, which has both a video track tracing pattern corresponding to the slow playback speed and a video head forwarding pattern, and corresponds to the above tracking error and corresponds to the division of the above basic pattern. An auto-tracking pattern generation system characterized in that an error pattern is created from the tracking error signal, and the error pattern is sequentially combined with the video track tracing pattern and combined in a reverse order to the video head forwarding pattern. Method.