JPS58158024A - Detector of tracking control signal - Google Patents

Abstract

PURPOSE:To enable normal tracking control without mixing unnecessary components by changing over the sum and difference outputs of the delayed and undelayed signals of a reproduced pilot signal in synchronization with the rotating phase of a rotary magnetic head. CONSTITUTION:The reproduced signal from a magnetic head 1 is amplified with a reproducing amplifier 3, and is supplied to terminals 4 and an LPF5. The signal supplied to the terminal 4 is processed with a video signal circuit. The signal 1 fed from the LPF5 produces a summed signal (m) and a differential signal (n) from the nondelayed and the delayed signal respectively at a 2H delaying line 10. The drawn out signals (m) and (n) are supplied to switches 28, 29. The switches 28 and 29 are controlled by head switching pulses (k). A main burst pilot signal is obtained from an LPF11 and a burst pilot signal for errors is obtained from an LPF12, and these signals are supplied respectively to a detecting circuit 30 and a sample pulse shaping circuit 14.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a rotating magnetic head type magnetic recording and reproducing apparatus configured to superimpose a pilot signal for tracking control on a video signal to be recorded and perform tracking control during reproduction. The present invention relates to a means for obtaining a normal tracking control pilot signal at times.

A magnetic head is mounted on an electromechanical transducer such as a piezoelectric element and rotated, and a control signal is applied to the piezoelectric element to electrically control the vertical position of the rotating magnetic head. Various tracking error detection methods have been proposed for rotating magnetic head type magnetic recording and reproducing devices that maintain normal tracking at all times.0 The tracking error detection methods that have been proposed can be roughly divided into 1, A method using an auxiliary head, 2. A method in which the playback head is slightly moved in the width direction of the recording track during playback, and the track deviation direction is detected from the output level fluctuation obtained at this time (search method). 3. Track deviation detection. How to record pilot signals. is possible.

Method 1 using an auxiliary head requires an extra head (for tracking deviation detection) to be mounted accurately on the same piezoelectric element, and an extra rotary transformer and preamplifier for extracting the error signal are also required. Therefore, the structure is complicated and the cost is high.

In the second method, the response speed of the piezoelectric element is limited by the mass of the magnetic head, and control that sufficiently follows the curvature of the recording track cannot be performed, and the head gap angle is 90° with respect to the longitudinal direction of the recording track. In the case of the azimuth recording method (such as the method used in the VH8 method), when the head is vibrated in the trunk width direction during playback, this vibration appears as time axis fluctuations in the playback signal. The drawback is that this search method is difficult to use.

Various methods have been proposed for method 3, but they can be roughly divided into 3-a. Continuous pilot signals with different frequencies are recorded, and when reproduced, the pilot signal frequency reproduced from the pyro track of the main track is different. This is a method of detecting the direction of track deviation by using the
Is there a way to detect the direction of track deviation by detecting the crosstalk pilot signal levels from both adjacent tracks based on the timing of the pilot signal of the main trunk? In the case of 3-a, it is generally necessary to use three or more types of pilot signal frequencies, which requires a considerable bandwidth for pilot signal recording, reducing the video signal recording bandwidth, and the need to separate three or more types of pilot signals. There are drawbacks such as the need for a large number of narrowband filters and the need for three or more types of pilot signal generation circuits, and also the problem of damage prevention due to tracking control pilot signals leaking onto the screen during playback. occurs, making the screen difficult to see. From the above results, the impact on the screen,
When considering time axis fluctuations, cost, etc., it is considered that a good tracking control method is to intermittently record pilot signals as shown in item 3 above.

Next, a method for recording pilot signals for tracking control will be described.

FIG. 1 shows the recording positional relationship between the video signal a and the pilot signal for tracking control.
Sometimes the symbol is used. ) is recorded only during the blanking period (hereinafter referred to as the burst pilot signal). In FIG. 2, recording tracks A1. B1. A2. B2. A3. B3...
... are formed sequentially. In the blacked out area in FIG. 2, burst pilot signals are recorded every 2H. The recording frequency fp of the burst no.
It is simple in terms of circuit configuration to configure X f H≠126 (KHz). In addition, the burst no kilot signal is A
Tracks recorded by the head (A rack) and tracks recorded by the B head (B track) are recorded adjacent to each other, but each frame is recorded so that they are not adjacent to each other.

The phase of the burst pilot signal recorded on the A track is the same phase (0 degrees), and the phase of the burst pilot signal recorded on the B track is 0 degrees shifted every 2H, and the phase is 180 degrees.
recorded in degree phase. The symbols 0 and π shown in the diagram of FIG. 2 indicate the recording phase of the burst pilot signal.

Conversely, it goes without saying that the same effect can be obtained by recording the A track with a phase shift of 0 and a phase of 180 degrees every 2H and the B track with the same phase (0 degrees), but it is necessary to obtain a primary tracking error signal. The reproducing circuit system will be explained below.

FIG. 3 is a block diagram of the reproducing circuit system, and the Nth is the fourth
The waveforms of each part of the figure are shown. In FIG. 3, a signal reproduced from a rotating magnetic head 1 is amplified by a regenerative amplifier 3 via a switch 2 connected to the reproducing side (P, B terminals), and its output is sent to a low-pass filter 6 (hereinafter referred to as LPF). ) and terminal 4. Terminal 4 is connected to the video signal processing circuit (
(not shown). A burst pilot signal a is obtained from the LPFs. It is assumed that the magnetic head 1 is scanning a recording track A3 shown in FIG. The burst pilot signal reproduced at this time provides an output as shown in FIG. 4a.

In P P of FIG. 4, 1 is recorded on track A3,
3, the main pilot signal recorded on track B3 and the adjacent pilot signal recorded on track B3 (the crosstalk component from the adjacent track is referred to as an error burst high lot signal).

) is the superimposed signal.

Also, burst pilot signal P2. P4 is trunk B
This is the error pilot signal recorded on 2.

The phase inversion circuit 6 is a circuit for making the phases of the burst high lot signals from the main track to be scanned for reproduction in the same phase. In this configuration example, it is a B track, and the reproduced burst pilot signal is inverted every 2H to obtain signals that are all in phase. Since the reproduction signals of the A track are all reproduced in the same phase, it is not operated when the A track is reproduced. The phase inversion circuit 6 is controlled by obtaining a head switching signal (hereinafter referred to as a head switching pulse) supplied from a terminal 7 and a 1/4 fH signal supplied from a terminal 8 via a NAND circuit 9. There is. The output of the phase inversion circuit 6 is supplied to the 2H delay line 1o to obtain a sum and difference signal of the before and after delay signals. From the obtained sum signal, only the burst pilot signal reproduced from the main track is extracted. As for the groove difference signal, only the error burst pilot signal reproduced from the adjacent track is extracted. This means that when the burst high lot signal before delay and the burst pilot signal after delay are summed, the reproduced burst pilot signal from main track A3 is in phase, and both adjacent tracks B2. The reproduced burst pilot signal from B3 is in reverse phase every 2H, so the burst pilot signal from main track A3 is +
Both adjacent tracks B2. The burst pilot signal from B3 is canceled and a regenerated burst pilot signal, ie, a main burst pilot signal, is extracted from main trunk A3. If a difference is taken, the reproduced burst pilot signal from the main track A3 is canceled and the reproduced burst pilot signals from both adjacent tracks B2 and B3, that is, the error burst high lot signal are extracted.

The extracted sum and difference signals are LPFll and LPF'
+2. From the LPF 11 and LPF 12, the signals shown in FIG. 4C are obtained. In FIG. 4, PA3 is the burst pilot signal reproduced from the main track A3, and Pb0 in FIG. 4C is the signal from the track B2. Pb0 is a signal obtained from track B3.

The error pilot signal C is detected by the detection circuit 30 and supplied to the peak hold circuit 13, where the error value is held. The peak hold circuit is configured to be reset by a reset pulse 27 every 1H, and the peak hold circuit 13 is configured to be reset every 1H.
A control device that outputs a hold value according to the error burst pilot signal output that is reproduced every time (Fig. 4 d). On the other hand, LPF
The output from 11 is supplied to a sample pulse shaping circuit 14. The sample pulse shaping circuit 14 creates sample ring pulses f and q from the burst pilot signal reproduced from the main trunk and supplies them to a sample hold circuit 16 and a sample hold circuit 16 (hereinafter referred to as S/H). The error burst pilot signal from the peak value hold is sent to the S/H15 and S/H15.
1 (sample and held at 16, and each signal corresponding to the reproduced output of Pb0.Pb0 of the error burst pilot signal C is supplied to the differential amplifier 17.
At step 7, the levels of PB and Pb0 are compared and a signal corresponding to the difference in power between the two is obtained. The signal obtained from the differential amplifier 17 is a signal corresponding to the track deviation.

This is because when the magnetic head 1 scans and reproduces the track A3 shown in FIG. 2, if the magnetic head 1 shifts toward the track B3, the level of the error burst pilot signal PB3 reproduced from the track B3 increases. Also B
If scanning is shifted to the 2 side, the level of the error burst pilot signal PB2 reproduced from the track B2 will increase, and the level of the error burst pilot signal PB3 will decrease. Therefore, the error burst pilot signal PB2. reproduced from track B2 and track B3. If the levels of Pb0 and Pb0 are controlled to be equal, the magnetic head 1 can accurately scan the track A3. As is clear from the figure, when the magnetic head 1 scans the A trunk and when the B track is scanned, there is a difference in the track deviation direction of the magnetic head 1 and the level difference between the error burst pilot signals obtained from both adjacent tracks. For example, when the magnetic head 1 scans and reproduces track A, the track where the burst pilot signal is recorded at the same position in the track width direction as the burst pilot signal reproduced from the main track A is The track located on the right side in the above, and in which the burst pilot signal is recorded at the same position as the burst pilot signal reproduced from main track B at this time when the magnetic head 1 is reproducing and scanning the B track, is shown on the paper. Located on the left. Therefore, it is necessary to reverse the polarity of the tracking error signal obtained between the head and the B head. The inversion circuit 18 shown in FIG. 3 is provided for this purpose. The switch 19, to which the inverted signal and the original signal (non-inverted signal) from the inverting circuit 18 are supplied, is switched by a switching pulse from the terminal 7 and alternately outputs the inverted signal and the original signal, so that the output signal is can get. This signal is a tracking error signal, and if the magnetic head deviates to the right with respect to the recording track, a higher voltage will be obtained compared to the on-track voltage, but if it deviates to the left, a lower voltage will be obtained. . The tracking error signal is separated by gate circuits 2° and 22 into independent tracking error signals i and j for the A and B heads. This separated signal outputs a tracking error signal only while each head is in contact with the magnetic tape, and holds the value of the previous tracking error signal while the other magnetic head is in contact with the magnetic tape.

Circuits 21 and 23 are piezoelectric element drive circuits and drive piezoelectric elements 24 and 26.

With the above configuration, the piezoelectric element is driven in accordance with a relatively high frequency (1/2 fH) tracking signal to control the height direction position of the rotating magnetic head.
) is configured as an auto-tracking control system that can follow track bends with sufficient gain.

As explained above, the phase inversion circuit 6 is referred to as B in this explanation.
) Only the rank is inverted every 2H, and after the inversion, the signal is supplied to the 2H delay line 1o, and the sum and difference of the signals before and after the delay are calculated. However, in the case of such a configuration, the phase inversion circuit 6 converts (H) every 4H depending on the circuit configuration.
When a pulse is added and only the burst pilot signal portion is inverted in polarity (0 degrees, 180 degrees), the switching noise or DC change is extracted and riding on the one burst pilot signal. Although it may be possible to reduce this switching noise or DC variation by configuring the circuit, it is difficult to completely eliminate it. Therefore, when such a signal is added to the 2H delay line 1o, the delay line 1o calculates the sum or difference between the signal on which switching noise or DC change is added and the signal on which switching noise or DC change is not added. Otherwise, the main burst pilot signal and the error burst pilot signal cannot be completely separated, resulting in a normal main burst pilot signal or an error burst pilot signal, and the main burst pilot signal contains an error burst pilot signal component or switching noise. Otherwise, the main burst pilot signal component or switching noise may remain in the error burst pilot signal.

In particular, the error burst pilot signal extracts the signals on both sides of the main track, and the error burst pilot signal itself is low in level, resulting in a poor signal-to-noise ratio of the error burst pilot signal itself, which is normal. This may cause inconveniences such as not being able to perform accurate tracking control or tracking being disturbed by unnecessary components.

FIG. 5 shows an embodiment of the present invention. 3 in Figure 6
Components that function in the same way as the conventional example shown in the figure are given the same numbers. In Fig. 6, during playback (switch 2 is set to P
The reproduction signal from the magnetic head 1 (connected to the B side) is supplied to the reproduction amplifier 3 via the switch 2 and amplified by the reproduction amplifier 3, and its output is supplied to the terminal 4 and the terminal 4 which is supplied to the LPF 5. The signal is the same as the conventional example, using the video signal circuit (
(not shown) and processed. It is assumed that the magnetic head 1 scans A3 during the A track period and B3 during the B track period. A burst pilot signal (FIG. 6 1) is obtained from the LPF 5.

Pl and P3 of burst pilot signal No. 1 in FIG. 6 are signals in which the main pilot signal recorded on track A3 and the error burst pilot signal of track B3 are superimposed, and pp is a signal in which the main pilot signal recorded on track B21 4 is the main recorded on track B3. A signal in which the pilot signal and the error burst pilot signal of track A3 are superimposed, P1
2. P14 is an error burst pilot signal recorded on track A4.

The signal l from the LPFcs is supplied to the 2H delay line 1o. A 2H delay line 10 obtains a sum and difference signal from the signals before and after the delay. The obtained sum signal is, as shown in FIG. taken out. Also, the difference signal is
During the A track reproduction period, the error burst pilot signal is reproduced from the adjacent track, and during the B track reproduction period, the high error burst pilot signal is reproduced from the main track.

A burst high lot signal was extracted. This means that
As explained in the conventional example, in the recording pattern shown in FIG. 2, the main track A3 during the A track reproduction period.
The reproduced burst pilot signals of adjacent tracks B2. The regenerated burst pilot signal from B3 is in reverse phase. Also, the B track playback period is main track B3.
The reproduction burst pilot signal from the adjacent track AA is in reverse phase, and the reproduction burst pilot signal from the adjacent track AA is 3.
ν 4 In-phase. Therefore, the sum and difference signals are shown in Fig. 6 m and n.
A signal like this is extracted.

The extracted signals m and n are sent to the switches 28 and 29.
supplied to Switches 28 and 29 are controlled by a head switching pulse k.

For example, assume that the switch operates when the control voltage of the switch is (High). (LOW) for the A track playback period switching pulse, therefore switches 28 and 2
9 is not operated and the switches 28 and 29 remain connected as shown, L P Fll is supplied with the signal m of the sum of the 2H delay lines 1o, that is, the main burst pilot signal, and the LPF 12 is supplied with the signal m of the sum of the 2H delay lines 1o. During the 0th order B trunk regeneration period in which the difference signal n error burst pilot signal is supplied, the switching pulse is (: Hiqh
) and coloring switches 28 and 29 are operated and connected to the opposite terminals shown. Therefore, LPFll has a 2H delay line 11.
The difference signal n of the main burst pilot signal is supplied to the LPF 12, and the sum signal m of the 2H delay line 10 is supplied to the error burst pilot signal. Therefore, LPFl
A main burst pilot signal shown as signal q is obtained from the LPF 12 during both the A track playback period and the B track playback period, and an error burst high lot signal shown as signal r is obtained from the LPF 12 during both the A track playback period and the B track playback period. The obtained signals are respectively supplied to the detection circuit 3o and the sample pulse shaping circuit 14. The subsequent operations are the same as those in the conventional example, and a description thereof will be omitted. With the above configuration, 2H can be achieved as explained in the conventional example.
There is no need to invert every 4H of one field (for example, during the B track playback period) before the delay line 1o, and switching noise or DC changes are not generated during the inversion operation. It is possible to remove unnecessary components from the error burst pilot signal without mixing the error burst signal component, the switching noise, DC variation, etc. into the main burst pilot signal.It is also possible to remove unnecessary components from the error burst pilot signal. Normal tracking control can be performed without contamination.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing the timing relationship between the video signal and the burst pilot signal used in the present invention, and FIG. 2 is a part of the recording pattern on the magnetic tape of the burst pilot signal used in the present invention. and a schematic diagram of the shape of the magnetic head; FIG. 3 is a block diagram showing a conventional reproduction system;
Fig. 4 is an operating waveform diagram of the conventional example shown in Fig. 3, Fig. 6 is a schematic block diagram of the reproducing system of one embodiment of the overlapping moe, and Fig. 6 is an operating waveform diagram of each part of Fig. 6. be. 1・me・・・Rotating magnetic head, 2, 19, 28° 29
...Switch circuit, 3...Regenerative amplifier, 5 11 12 26-----LPF, 1O--
---2H delay circuit, 13...Peak hold circuit, 14, 016. Pulse shaping circuit, 15, 1
6------Sample hold circuit, 17...
・Differential amplifier, 18...--inverting circuit, 20, 22
...Gate circuit, 21.23...Piezoelectric element drive circuit, 24, 25...0...Piezoelectric element, 3o
...Detection circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Hunting and Figure 4 Ov

Claims (1)

[Claims] The pilot signal for tracking control is intermittently applied so that the pilot signal is aligned perpendicularly to one of the adjacent image recording tracks, and not aligned between the other adjacent track. It is superimposed on the video signal and recorded on magnetic tape by a rotating magnetic head.
During reproduction, the reproduced signal from the rotating magnetic head is guided to a comb-shaped filter including a delay circuit, and the comb-shaped filter obtains a sum output and a difference output of the delayed output and the non-delayed output, thereby controlling the rotation of the rotating magnetic head. The sum output and the difference output are alternately switched by a switching signal synchronized with the phase, and the main pilot signal from the main recording track where the pilot signal is to be reproduced is separated from the error pilot signal from the adjacent track. A tracking control signal detection device characterized by: