JPS58205944A - Tracking controller - Google Patents

Abstract

PURPOSE:To speed up the response speed, by supplying a reproducing information signal from a couple of magnetic heads reproducing a couple of tilted magnetic tracks of a recorded magnetic tape to a tracking control means via an extracting circuit and a digital integrator. CONSTITUTION:An input digital signal relating to the phase difference between block synchronizing signals B1, B2 based on a tracking error is applied to a digital integrator 15 and integrated. When the tracking error is large and the digital value of the input digital signal is large, accordingly a digital value of an output digital signal is increased rapidly, an amount of phase shift of a monostable multivibrator 23 is increased rapidly and the rotation of a capstan motor 27 is increased quickly so as to apply the tracking to magnetic tracks T1, T2 with rotary magnetic heads H1, H2 and the fast response is attained. In this way, fast response is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking control device rlK suitable for digital VT and the like.

First, let's talk about the recording format of conventional digital VTRs! 5! I will clarify. Since the signal band is wide in digital VT),
For example, one field digital video signal, NTSC
The two channels are divided into five, and the PAL or SgcAM two channels are divided into six, and each channel is used to divide the channel into two channels. It was recorded on magnetic tape to form a magnetic track, which was then played back.

Therefore, in such a digital VT) 180
For example, two sets of rotating magnetic heads arranged at an angle of It consists of Then, each set of rotating magnetic heads records the digital video signal on the magnetic tape so as to alternately form a #1 magnetic track and reproduces it.

FIG. 1 shows inclined magnetic tracks T1 + T2 arranged close together.
and a rotating magnetic head H, B2 for recording and reproducing the same.
It shows. glr gz is the rotating magnetic head H1, B
The two magnetic gaps have different azimuths. Digital video signals to be recorded on these #oblique magnetic tracks T1 r T21c are divided into blocks, and encoded in units of one block or several blocks through an encoding circuit for error correction and a channel encoding circuit. Temporarily, the signal is supplied to the rotating magnetic head 1 (l, 112) and recorded on the recording magnetic tape, the magnetic tracks T1 and T2 are reproduced by the rotating magnetic head H1tB2, and the reproduced signal is sent to the channel decoding circuit and the error correction circuit 11. The signal is supplied to a regular decoding circuit and decoded to obtain the original digital video signal.

In FIG. 1, i3L is #47il+magnetic track Tl.

B1 r 82 indicates one block of the digital video signal recorded on T2, and B1 r 82 indicates a block synchronization signal for each block of the magnetic track 'r1 p' 12. In the example of FIG. 1, the adjacent magnetic tracks T1. At T2, block synchronization signals B1 and B2 are recorded in phase in a steady state. Of course, recording may be performed with a predetermined phase difference in a steady state.

The width of such inclined magnetic tracks T1 + T2 is considerably narrowed for high-density recording. Therefore, mistracking is relatively likely to occur during playback.

Therefore, the applicant first obtained a tracking error signal by using synchronization signals of the same period, such as block synchronization signals, recorded on inclined magnetic tracks close to each other, and applied tracking control in an analog manner based on this signal. I proposed a device with a 5-5 structure.

The present invention aims to provide a tracking control device that has a fast response speed and can digitally control tracking.

The tracking structure according to the present invention is a pair of gradient magnetic tracks on a magnetic tape recorded in such a way that information signals including synchronous fr signals of the same period form a pair of adjacent gradient magnetic tracks having different recording azimuths. A pair of magnetic heads for reproducing tracks, an extraction circuit for extracting first and second reproduction synchronization signals from the reproduction information signals from the pair of magnetic heads, and a number corresponding to the period of the first reproduction synchronization signal. a counter that counts clock pulses; and a latch circuit that latches the counted contents of this counter with a timing pulse that is in a predetermined phase relation to a second reproduction synchronization signal.

It comprises a digital integrator that integrates the output of this latch circuit, and tracking control means that is supplied with a tracking error signal from this digital integrator.

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIG.

In Fig. 2, H1 and B2 are rotating magnetic heads that are close to each other and have magnetic gaps gt t gz of different azimuths, and in this case are rotating magnetic heads for both recording and reproduction. One or more sets of rotating magnetic heads li1.degree. 112 are attached to a rotating drum of a tape industry drum at predetermined angular intervals.

The rotating magnetic heads H1eB2 are connected to the respective aJ moving contacts a of changeover switches swl and SW2 which have a movable contact a, a recording side fixed contact r, and a reproducing side fixed contact p and are switched in conjunction with each other. (28t) is one recording input terminal, which is connected to the recording side identification contact r of the changeover switch SW1 via the recording amplifier (291). (2
82) is the other recording input terminal, and the recording amplifier (292)
It is connected to the recording side fixed contact ryc of the changeover switch SW2 via. Input terminal (281)? This is a signal obtained by dividing a yield digital video signal into two channels using a channel encoding circuit.

Each playback side fixed contact p of the cut-back switch sw, , SW2
are connected to each input side of the reproduction amplifiers (11) and t(12).

The output side of the playback amplifier (11) is the focus synchronization circuit (21)
and the input side of PLL (31), respectively. The output side of the reproduction amplifier (12) is connected to the bit synchronization circuit (2) and P
LL (32) human power 1lIIK are connected respectively. Also, P
The clock signal obtained from LL (31) is supplied to the bit synchronization circuit (21). Similarly, the clock signal obtained from the PLL (32) is supplied to the bit synchronization circuit (22).

The digital video signal and clock signal from the bit Yoshimasa circuit (21) and PLL (31) are then supplied to the block synchronization signal extraction circuit (41). Similarly, the digital video signal and clock signal from the bit synchronization circuit (22) and PLL (32) are supplied to the block Mfg number extraction circuit (42). Then, the block synchronization number 46 extraction circuit (41) l (42) outputs the first and second reproduced block synchronization signals B1 e B2 as shown in FIG.
is obtained. Incidentally, the pulses indicated by the broken lines in FIGS. 3A and 3H indicate the omission of the block synchronization signals B1 v B2.

The first reproduction block synchronization signal B1 is supplied to a monostable multivibrator (5), whereby a wind signal WD as shown in FIG. 3CK is obtained. In addition, the second reproduction pron> synchronization key signal B2 is supplied to a delay circuit (6) K, and the cycle lock synchronization signal B1 + 82 of the block synchronization signal B1 r 82 is magnetically activated with a predetermined phase difference. When recording on tracks T1 and T2, this delay circuit f
6J becomes unnecessary. Then, simply the outputs of the constant multivibrator (5) and the delay circuit (6) and the control signal d (Fig. 3D) from the input terminal (8) which becomes "1" at the time of playback and rOJ at the time of editing and recording. It is supplied to an AND circuit (7). A pulse e as shown in FIG. 3E is obtained from the AND circuit (7). Pulse e cannot be obtained when any of the block synchronization signals B1+82 is missing or when Rinto recording is performed. This pulse C has a constant phase difference with respect to the block synchronization signal B2, but the phase difference with respect to the block synchronization signal B1 changes depending on the tracking deviation.

(9) is a clock oscillator, and the clock pulses from this (instead, the reproduced clock signals from PLL (31) and (32) may be used) are supplied to the counter (11 and counted. , this counter (II) is cleared by the clock synchronization signal B1. Therefore, this counter (11) counts the number of clock pulses according to the period of the first clock synchronization signal B1.

The count contents of the Kakunta decoy are supplied to the latch circuit 00.

The latch contents of the launch circuit αυ are changed every time the pulse e arrives, and the latch contents are not changed when the pulse e does not arrive.

The digital signal from the latch circuit αυ is supplied to the synthesizer Q3, from which a digital signal of a predetermined digital value from the A-D converter side is subtracted. The digital value of the digital signal from the A-D converter side corresponds to the analog voltage obtained at the movable terminal of the potentiometer α connected between the power supply and ground. This potentiometer α floor is
It is variably adjusted according to the phase difference of block synchronization signal bitB20 recorded on the adjacent magnetic track Tl*T2. When the phase difference is constant on any recorded magnetic tape, combiner H, potentiometers a and A
- The results on the D converter side are all negative.

It is assumed that tracking is achieved when the digital value of the digital signal from the synthesizer α is O.

The digital signal from the combiner u2) is sent to the digital divider (1
5). This digital divider (19 is composed of a synthesis d4H for adding digital signals and a latch circuit Q7). The digital signal from the synthesizer a2 is supplied to the synthesizer (161), the digital signal from the synthesizer Oe is supplied to the latch circuit a1, and the digital signal from the latch circuit Q71 is further supplied to the synthesizer (161). It is added to the digital signal from Q4. Also, input terminal 0
The horizontal or screen synchronizing signal is supplied to the variable frequency divider (7) and its frequency is divided into 1/N, and the divided synchronizing signal and the control signal e from the input terminal (8) are is supplied to the AND circuit υ, and its output is a latch Igl (Q7)
supplied to Then, the output digital signal from the synthesizer (161) is supplied to the D-Ai converter 081, where it is converted into A-A converter 081, and as shown in FIG. The tracking error signal f is then supplied to the tracking control means □□□.

In this example, the tracking control means (c) is provided in the cab stan servo circuit. (20 is a capstor/motor. The playback (recording) duty synchronizing signal from the input terminal (2) is supplied to the phase comparator Masuda via the monostable multivibrator t2i as a transition incest, and the magnetic head c! The phase is compared with the control g1 signal (CTL signal) from 4), and the comparison output is supplied to the capstan motor (2) via an amplifier (to).

As the tracking control means, rotating magnetic heads H1 and Hl are attached, and an electric head such as a bimorph which is biased in a direction perpendicular to the scanning direction with respect to the magnetic tape is attached.
A mechanical converter may also be used.

Next, the operation of the tracking control device shown in FIG. 2 will be explained. The digital integrator α9 is supplied with an input digital signal related to the block synchronization signal H1, 820 phase difference based on the tracking error and integrated, so when the tracking error is large and the digital value of the input digital signal is large, the output is output. The digital value of the digital signal rapidly increases, the amount of phase shift of the monostable multivibrator (total) rapidly increases, and the rotating magnetic heads H1, Hl perform one tracking on the magnetic tracks Tl, T2. The rotation speed of the motor (b) increases rapidly. In other words, the response is fast.

Also, when the tracking error is small and the digital value of the input digital signal is small, the digital value of the output digital signal of K gradually increases, and the amount of phase shift of the monostable multivibrator (C) gradually increases, resulting in a one-rotation magnetic head. kll, H
The rotational speed of the capstan motor (c) gradually increases so that tracking of the magnetic tracks T1 e T2 by 1 is achieved. νIJ, the response is stable.

In addition, by varying the dividing ratio 1/N of the Loe variable frequency divider (to), the degree of integration of the digital integrator U [with] tJI
4 adjustments can be made.

Also, when editing and recording (when assembling or inserting), the latch circuit αυ side 7) is held in the hold state.

Tracking error just before that 4. ．． No. 3 is retained at the time of editing record.

According to the present invention described above, it is possible to obtain a tracking control device that has a fast response speed and can digitally control tracking (2).

[Brief explanation of drawings]

@Figure 1 is a diagram showing the magnetic track pattern and magnetic head in a conventional digital VTR, Figure 2 is a block diagram showing an embodiment of the present invention, and Figure 3 is a waveform diagram used for PM clarity. . Hl, Hl are a pair of rotating magnetic heads, TI, T2 are a pair of # oblique magnetic tracks, (41) t (4g) is a Tsukuda circuit, 0I is a counter, Uυ is a latch circuit, aω is a digital integrator, ( c) is a tracking control means. Figure 1 Figure 3

Claims (1)

[Claims] a pair of magnetic heads for reproducing a pair of #l oblique magnetic tracks of a magnetic tape on which information signals including synchronizing signals of the same period are recorded so as to form a pair of closely inclined oblique tracks having different recording azimuths; , an extraction circuit for extracting the first and second reproduction synchronization signals from the reproduction information signals from the pair of magnetic heads, and a number of glue/lock pulses corresponding to the cycle of the first reproduction dokan thousand signal. a counter for counting, a latch circuit for latching the count contents of the counter with a timing pulse having a pfr constant phase relationship with respect to the second reproduction synchronization signal, a digital integrator for integrating the output of the launch circuit; A tracking control device comprising a tracking control means to which a tracking error signal is supplied from a digital divider.