JPS60179921A - Position controller of rotary magnetic head - Google Patents

Abstract

PURPOSE:To suppress the level variation of a head position control signal by comparing the A/D conversion output of an amplitude detector with the data preceding said conversion output by one or two vertical scan cycles and replacing said data with another data preceding by at least two vertical scan cycles in case said difference exceeds the prescribed value. CONSTITUTION:An optional data Di obtained by the scan of a head 11A, for example, is supplied to a data comparison means 72 from an input terminal 71 and compared with the data Di-2 obtained by the scan of the head 11A before a frame, i.e., two vertical scan cycles. If the difference between both data exceeds the prescribed value, the data Di is decided as the data on the omission value owing to a drop-out. Thus the data Di is replaced with the data Di-2. In case said difference does not exceed the prescribed value, no replacement is carried out with the Di. The error data is converted into an error signal by a D/A converter 65 and delivered through an output terminal 58 as a position control signal of a BM head (11A, etc.). Thus the level variation is suppressed for the head position control signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to helical scan video tape recorders (VTRs).
) The present invention relates to a position control device for a 1!1 rotation magnetic head which is commonly used and suitable.

Background Art and Problems In a helical scanning VTR, a rotating magnetic head is attached to an electro-mechanical converter such as a bimorph, and a required driving voltage is supplied to the bimorph to move the head in a direction approximately perpendicular to the scanning direction. Displace it so that the head is on the tape.
It is well known to provide a device for precisely scanning two inclined tracks from beginning to end. In addition, this type of device is used during variable speed playback;
P (Dynamic Track Follotmin
g) Sometimes called a device.

In order for the DTP device to operate properly, the (
It is naturally necessary to be able to detect the position of the head relative to tJr'*u. Regarding this head position detection, many methods have been proposed in the past.

On the other hand, even during constant speed playback of a VTR, the cabzukun phase servo ensures that the tape accurately scans the playback track on the tape. In the case of this tracking servo, it is also necessary to be able to detect the position of the head relative to the track.

For this reason, it has been widely practiced to record a control signal on a control track provided at the edge of the tape, and use this control signal to apply tracking servo to the capstan.

However, with such a controlled tracking method, track knocking information can only be obtained near the starting point of the recording track, and it is difficult to maintain the required track knocking accuracy over the entire length of the track.

Therefore, as an alternative to the control track method, a method has been proposed in which a plurality of different pilot signals are sequentially recorded on each track on a tape in a circular manner, and tracking servo is performed by referring to the pilot signals during playback.

First, this pilot signal system will be explained with reference to FIGS. 1 and 2.

In the pilot signal system, as shown in FIG. 1, frequencies fz, f2 . Set pilot signals for four types of noodles f3 and f4. The frequencies f1 to f4 of each pilot signal are, for example, as follows.

f 1 = 102.54 kHz f 2 - 118.95 kHz f 3 = 165.21 kHz f 4 = 148.69 kHz Also, as can be seen, the following relationship holds between the frequencies of each pilot signal.

Iffzl=lfa-f41=fL=16kHz
l F; ra l=l f4 ft I=fH=46
During kHz recording, the pilot signal f1~
[4 is the carrier luminance signal YFM and the low-frequency conversion chromaticity signal CL
The signal is frequency multiplexed with ζ and recorded sequentially and cyclically on each track on the tape.

An example of the configuration of a tiger knocking servo using the pilot signal system is shown in Figure 2.

In FIG. 2, pilot signals are recorded as described above, and each track L of the tape VT runs in the direction of the arrow.
1 + j2 + j3 *, t'+, . The reproduction signal from the head (11) is supplied to the reproduction amplifier (12), and among the outputs of the amplifier (12),
The carrier luminance signal YFH and the low frequency conversion chromaticity signal CL are supplied to a reproduction processing circuit (13) and undergo signal processing such as "ζ" and demodulation.

(20) represents the head position detection device as a whole, and the pilot signal component from the amplifier (12) is filtered by a low-pass filter (
21) and supplied to the ζ multiplier (22). The multiplier (22) is connected to a signal generator (°ζ) via an electronic rotary switch (23) that is synchronized with the rotation head (11) sequentially scanning tracks t1 to t4 on the edge of the tape. 24) whose frequencies are fz”, , f4
．． Reference pilot signals f3','ft are supplied cyclically in this frequency order.

In addition to the original pyro 7) recorded for each trunk, the reproduced pilot signal component includes crosstalk components from each preceding and subsequent adjacent track. ) smell °ζ, multiplication of the regenerated pilot signal component by the reference pilot If number produces difference signal components as shown in the following table.

These difference signal components H and fL are passed through bandpass filters (25) and (26), respectively, to a peak detector (27).
) and (28). Detector (27) and (2
The outputs of 8) are respectively supplied to one and the other input terminals of a differential amplifier (29).

The error signal output of the differential amplifier (29) is supplied to the capstan servo circuit (30), and the output of the servo circuit (30) is supplied to the capstan motor (3) via the drive amplifier (31).
2).

As is clear from the table above, the multiplier (22) smell ζ
is the frequency [
A difference signal of 8 is obtained, whereas a frequency fLO difference signal is obtained due to crosstalk from the trailing track. Therefore, by comparing the levels of the difference signals fH and r, it is detected whether the head has deviated from the predetermined trunk in either the stop or negative direction. Therefore, in order to track a predetermined track, the capstan motor (32) should be controlled so that both difference signals are at the same level and the error signal output of the differential amplifier (29) is at zero level. .

ATF (＾utomaLic Track Fi) performs tracking servo using pilot signals as described in E.
This ATF type head position detection technology can be directly applied to head position detection in an L D 'I'' F device.

An example of the configuration of a DTP device using an ATF type error signal is shown in FIG. In FIG. 3, parts corresponding to those in FIG. 2 are designated by the same reference numerals and redundant explanation will be omitted.

In Figure 3, C, bimorph (40) is the drive amplifier (4
1), an error signal output is supplied from the differential amplifier (29) of the head position detection device (20), and this error signal output drives the rotating magnetic head (11) attached to the bimorph (40). Even during variable speed playback, the position of a predetermined track is controlled so as to accurately scan from the beginning to the end.

By the way, when recording is performed using a plurality of rotating magnetic heads (hereinafter referred to as BM heads) attached to a bimorph, the height of each 8M head is adjusted to match, that is, the height difference between them is eliminated, and uniform recording is performed. It is necessary to obtain a recording pattern of track pitches. However, due to the hysteresis characteristic of the bimorph itself, simply returning the drive voltage to zero does not restore the initial displacement state, and there is a possibility that the track pitch may be disturbed.

Therefore, a specific frequency fs (f
A method has been proposed in which pilots (different from f1 to f4) are recorded intermittently, and the amount of displacement of the 8M head is controlled so that the crosstalk of the f5 signal from the preceding adjacent track is at a constant level (Japanese Patent Application Laid-Open No. Publication No. 54-115113)
.

In this crosstalk reproduction method, in order to prevent the pilot signal of f5 from affecting the reproduced meat surface, one horizontal scanning period is set within the vertical retrace period at the beginning of writing of each track, as shown in During (IH), frequency f5 is 223k
Record the Hz signal.

Then, during the next IH, the recording current is cut off and playback (PB
) mode. Note that the recording period of the 15 signals of the preceding adjacent track and the reproduction mode period of the succeeding track are aligned in the width direction of the track on the tape.
There is. In this way, each 8M head will reproduce the crosstalk of the f5 signal recorded one track ago in a burst, so the displacement of each 8M head will be changed so that the level of the reproduced f5 signal will be constant. By controlling the amount, that is, the crystallinity, the quotient of each 8M head becomes equal, and the track pitch can be made uniform.

An example of the configuration of a BM head control circuit using the crosstalk repopulation method is shown in FIG.

In FIG. 5, two 8M heads (IIA) and (I
As is well known, the IB) is arranged at an angle of 180° within a head drum that does not have an oral bearing. Also, since the magnetic tape runs diagonally along the circumferential surface of the head drum for 180° (or 221"), each track on the tape is covered by both heads (IIA) and (IIA).
IB). In the case of a track pattern as shown in FIG. 4, tracks t1 and t3 are scanned by the head (11^), and tracks t2 and t4 are scanned by the head (IIB). Therefore, an output is taken out from each head (118) or (IIB) every l frame.

During recording, the switch S is closed and the recording current is supplied from the recording signal input terminal (50) to the two 8M heads (11
^) and (IIB) with capacitors C^ and cB, respectively.
The signal is alternately supplied to each track via the . When in regeneration mode, switch S is opened by a control pulse and 8
The M head (IIA) or (11B) regenerates the crosstalk of the 16 signals from the preceding adjacent track. Both BM heads (11^) are
) and (IIB) are alternately supplied to the reproducing amplifier (51) for each track. A control pulse is supplied from the control terminal (52) only during the PB mode period in FIG.
The amplifier (51) becomes operational. The output of the amplifier (51) is passed through a bandpass filter (53) to an envelope detector (54).
). The output of the detector (54) is passed through a sample hold circuit (hereinafter referred to as S/8 circuit) (55^) and (5
5B).

Both S/H circuits (55^) and (55B>) perform S/H operations alternately during the reproduction mode period of each track by sampling signals supplied to their respective control terminals (56A) and (56B). .Both S/H circuits (
The output signals at 55A) and (55B) represent the amplitude of the crosstalk of the signal at f5 during scanning of two adjacent tracks. These output signals are supplied to a differential amplifier (57), and the output thereof is taken out from an output terminal (58) as a position control signal for the 8M head.

- As mentioned above, the section where the f5 signal is intermittently recorded is limited to the edge of the track, and its length is I
Since it is as short as H, there is a drawback that if a dropout occurs in this part and the reproduced f5 signal is lost, the height relationship of the plurality of 8M heads will be disturbed.

In this case, the time constant of the detector is set to, for example, the vertical scanning period (V).
Although it is possible to make the length several times longer than the length, it is not a good idea because the response of the servo system will be slow.

OBJECTS OF THE INVENTION In view of the above, an object of the present invention is to provide a head position control device in which the height relationship of a plurality of rotary movable heads is not disturbed even if an intermittent recording pilot signal is lost due to dropout. It's there.

SUMMARY OF THE INVENTION The present invention provides for
a plurality of rotatable magnetic heads for recording a pilot signal in a predetermined section of each track and reproducing a pilot signal recorded in a first predetermined section of an adjacent preceding track in a second predetermined section of each track; A rotary magnetic head comprising an amplitude detector for detecting the amplitude of a reproduced pilot signal by a plurality of rotatable magnetic heads, and a control signal for controlling the amount of displacement of the plurality of rotatable magnetic heads is obtained from the amplitude detector. The position control device includes an A/D converter that A/D converts the output of the °C1 amplitude detector;
data subtraction means for obtaining the difference between the output data of the converter and the data one vertical scanning cycle before, and whether the difference between the output data of the A/D converter and the data two vertical scanning cycles before exceeds a predetermined value. data comparison means for comparing whether or not the data is present, and data replacement means for replacing the output data of the A/D converter with data including data from at least two vertical scanning periods ago in response to the comparison result of the data comparison means; This is a position control device for a rotating magnetic head, which includes a D/A converter for D/A converting output data of a data subtracting means.

According to the present invention, recording can be performed at a uniform track pitch without disturbing the height relationship of a plurality of rotary movable heads due to dropout of an intermittent recording pilot signal.

Embodiment Hereinafter, an embodiment of a position control device for a rotating magnetic head according to the present invention will be described with reference to FIGS. 6 to 9.

FIG. 6 shows the configuration of an embodiment of the present invention. In FIG. 6, parts corresponding to those in FIG. 5 are designated by the same reference numerals, and redundant explanation will be omitted.

In Figure 6, (60) is the input/output interface (
61) A microcomputer consisting of a central processing unit (CPU) (62) and a memory (63), which performs S/D for each track via an A/D converter (64).
The output of the H circuit (55) is supplied.

The output data of the computer (60) is sent to the D/A converter (6
5), and the output of the D/A converter (65) is taken out to the output terminal (58).

The operation of this embodiment is as follows. As shown in FIG.
), the pulsed output of the detector (54) ■
There will also be substantial dropouts and substantial omissions. On the other hand, during the reproduction mode period, the S/H circuit (55) is connected to the terminal (5
6) is supplied with the sampling signal ■ as shown in Figure 7C, and the output ■ of the S/H circuit (55), as shown by the solid line in Figure 7, is used for the next control after a dropout occurs. Until the arrival of the signal pulse, its level drops significantly.

As shown in Figure 7, the A/D converter (64) converts the analog output of the S/lr+1 path (55) into digital data at a timing that is appropriately delayed from the sampling signal O shown in Figure C. and manually input it to the computer (60).

A functional block diagram and a flowchart of the microcomputer (6o) are shown in FIGS. 8 and 9.

In Fig. 8, ζ, one head from the input terminal (71),
For example, arbitrary data Di obtained by scanning (11^) is supplied to the data comparator nvtz>, and
It is compared with the data Di-2 obtained by scanning the same head (IIA) one vertical scanning period ago.

When the difference IDi -Di-2l between both data exceeds the predetermined value Replaced with 2. This data replacement is equivalent to interpolating the output of the S/H circuit (55), as shown by the broken line in Figure 7. lDi
If Di-2l does not exceed the predetermined value X, it is assumed that no dropout has occurred, and the data Di is not replaced.

The data Di that has been replaced or not replaced as described above is compared with the data Di-z one field before by the data subtraction means (76). Data Di-
Since x is due to the scanning of the other head, for example (11B), the difference between both data Di-D i-1 is the error data between both heads (11^) and (IIB), and this error data is converted into an analog error signal by a D/A converter (65), and taken out from an output terminal (58) as a position control signal for the 8M head.

In this embodiment, data at the time of dropout occurrence is replaced with data from one frame before, thereby suppressing fluctuations in the head position control signal signal.

Note that the replacement data may be not only single data from one frame before, but also average data from several frames before.

Effects of the Invention As detailed above, according to the present invention, recording can be performed at a uniform track pitch without disturbing the crystallinity of a plurality of rotating heads due to dropouts of intermittent recording pilot signals. A position control device for a rotating magnetic head can be obtained.

[Brief explanation of the drawing]

Figures 1 and 2 are frequency spectra and block diagrams for explaining the conventional ATF system, and Figure 3 is the conventional ATF system.
FIGS. 4 and 5 are block diagrams showing an example of the configuration of a DTP device based on the F technology. 7 is a block diagram showing an embodiment of the position control device for a rotating magnetic head according to the present invention, and FIGS. 7 to 9 are a time chart, a functional block diagram, and a flowchart of the embodiment of FIG. 6. (11) , (11^) and (IIB) are rotating magnetic heads, (20) is a head position V detection device, (40) is a bimorph, (54) is an amplitude detector, (55) is a sample hold circuit, (60) is a microcomputer, (72)
is a data comparison means, (74) is a data replacement means, (76
) is a data subtraction means.

Claims (1)

[Claims] A pilot signal is recorded in a first predetermined section of each adjacent track on the record carrier, and the pilot signal is recorded in the first predetermined section of an adjacent preceding track in a second predetermined section of each track. It has a plurality of rotary movable magnetic heads that reproduce signals, and an amplitude detector that detects the amplitude of the reproduced pilot signal by the plurality of rotatable dynamic magnetic heads, and the amplitude detector detects the amplitude of the reproduced pilot signal from the plurality of rotatable dynamic magnetic heads. - In a position control device for a rotating magnetic head that obtains a control signal for controlling the amount of displacement of the magnetic head,
an A/I) converter for A/D converting the output of the amplitude detector; a data subtraction means for obtaining a difference between the output data of the A/D converter and data one vertical scanning period before the A/D converter;
data comparing means for comparing whether the difference between the output data of the /D converter and the data two vertical scanning periods before exceeds a predetermined value;
data replacement means for replacing the output data of the /D converter with data including data from at least two vertical scanning periods earlier;
D/A converting the output data of the data subtraction means to D/A.
1. A position control device for a rotating magnetic head, comprising: an A converter.