JPS5894128A - Controlling system for tracking - Google Patents

Abstract

PURPOSE:To eliminate the noise component leaking into a pilot signal, by superposing the pilot signal for controlling the tracking on a recorded information signal for recording and performing tracking control by utilizing the pilot signal at the time of reproduction. CONSTITUTION:Signals reproduced at a magnetic head 1 are amplified by a reproducing amplifier 2 through a switch SW1 connected to the reproducing side, and the output is supplied to a low-pass filter LPF4 and a terminal 3. The output supplied to the terminal 3 is further sent to a picture signal processing circuit. By an LPF4, a pilot signal (a) for controlling the tracking is obtained. Moreover, a phase inverting circuit 5 lockes the phase of a signal 9 from the reproducing main track to the phase of said signal (a). To control the phase inverting circuit 5, a head switching signal (hereinafter called the switching pulse) supplied from a terminal 6 and a signal of 1/4fH supplied from another terminal 7 are obtained through an NAND circuit 8.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a magnetic recording and reproducing apparatus configured to record a tracking control pilot signal superimposed on an information signal to be recorded during recording, and perform tracking control using the pilot signal during playback. This invention relates to a tracking control method for an apparatus, and is characterized by a method for removing noise components that leak into a pilot signal for tracking control during playback.

A magnetic head is mounted on an electromechanical transducer such as a piezoelectric element and rotated, and by applying a control signal to this piezoelectric element, the vertical position of the rotating magnetic head is electrically controlled. Various tracking error detection methods have been proposed for rotary head type magnetic recording and reproducing devices that maintain normal tracking at all times.

Tracking error detection methods that have been proposed in the past can be roughly divided into: (1) a method that uses an auxiliary head, and (2) a method that slightly changes the playback head in the width direction of the recording track during playback to prevent this much-anticipated output level fluctuation. A method for detecting the direction of track deviation (search method).

(3) This is a method of recording a pilot signal for detecting track deviation.

The auxiliary head method (1) requires an extra head (for tracking deviation detection) to be mounted accurately on the same piezoelectric element, and also requires an extra rotary transformer and preamplifier to extract the error signal. The disadvantage is that the structure is complicated and the cost is high.

In method (2), the response speed of the piezoelectric element is limited by the mass of the magnetic head, etc., making it difficult to perform control that sufficiently follows the curvature of the recording track, and the gap angle of the head is 90° with respect to the longitudinal direction of the recording track. In the case of an azimuth recording method (the method used in VHS VTRs, etc.) in which the head is vibrated in the track width direction during playback, this vibration will appear as time axis fluctuations in the playback signal. , this search method has the disadvantage that it is difficult to use.

Various methods have been proposed for (3), but
Broadly speaking, 3-A: Record continuous pilot signals with different frequencies, and use the fact that during playback the pilot signal is different from the pilot signal of the main track, and that the pilot signal frequencies played back from the adjacent tracks are different. A method to detect the direction of deviation.

3-A conceivable method is to record pilot signals intermittently and detect the crosstalk pilot signal levels from both adjacent tracks using the track as a reference to detect the direction of track deviation.

In the case of 3-a, it is generally necessary to use three or more types of pilot signal frequencies, which requires a considerable additional band for pilot signal recording, reducing the video signal recording band, and it is difficult to separate three or more types of pilot signal frequencies. There are disadvantages such as the need for a large number of narrowband filters, the need for three or more types of pilot signal generation circuits, and the fact that tracking control pilot signals leak onto the screen during playback. This causes interference and makes it difficult to see the screen. From the above results, when considering the influence on the screen 1 time axis fluctuation, cost, etc., the method of recording pilot signals intermittently as shown in 3-1 above is considered to be the worst tracking control method. It will be done.

Next, a method for recording a tracking control pilot signal, which is the object of the present invention, will be described. Figure 1 shows the recording positional relationship between the video signal a and the tracking control pilot signal. Recording is performed only during the ranking period (hereinafter referred to as the "Ironoto signal"). In FIG.
．． B2. It is assumed that unevenness, B3, etc. are formed sequentially, and the recording position of the horizontal synchronization signal on each recording track is aligned with the horizontal synchronization signal recording position of the adjacent track (H arrangement). are doing). The blacked out area is where the burst pilot signal is recorded every 2H. In terms of circuit configuration, it is easy to configure the frequency jp of the burst pilot signal to be n x fH (n is an integer, fH is the horizontal synchronization signal frequency), for example, 8·fH=126 (KHz). In addition, the burst pilot signals are marked adjacent to each other between the tracks recorded with Muhenodo and the tracks recorded with the B head (B rack), and so that they are not adjacent to each other for each frame. recorded. Also, the phase of the burst pilot signal recorded on the A track is the same phase (0 degrees), and the -stop pilot signal recorded on the B track has a phase shift of ○ every 2H and a phase of 180 degrees. It will be recorded as follows. In the figure, 0 and π indicate the recording phase of the burst pilot signal. Conversely, the same effect can be obtained by recording the Mu track with a phase shift of ○ every 2H and a phase of 18 degrees, and the B track with the same phase (0 degrees). In addition, in FIG. 2, the track width TW of the magnetic head HD is equal to the track pitch TP.
Suppose that it is approximately equal to, but slightly larger. ('r
Even if w is slightly narrower than 'rp, if the recorded frequency is low, the signal from the adjacent signal can be reproduced due to leakage magnetic flux. ) and the core width VC of the magnetic head in contact with the tape is Wc (7Tp).Assume that the burst pilot signal is recorded as shown in FIG. Considering the case, when the burst pilot signal regenerated by the head is passed through a comb-shaped filter using a two-horizontal scanning period delay line (2H-DL) 51 as shown in FIG. and the output terminal 56 of the subtracter 54
The signals shown in FIG. 4a and b are obtained respectively. Fourth
In the figure, A5. The signals such as B2 and B3 are respectively M3. B2. B3) Shows the playback signal from the rack, Δ1
2. Δm4. ΔBj, ΔB4, etc. are also MU2. Mua
, Bl, B4) shows the reproduction signal from the rack, but shows that the reproduction level is low. That is, this comb-shaped filter separates the signals so that only the signal components recorded by the track recorded by the B head are outputted from the addition side, and only the signal components recorded by the B head are outputted from the subtraction circuit side.

In FIG. 4a, since M3>ΔM2+ΔA4, the position where the burst pilot signal is recorded on the M3 track can be identified. Using this identified position as a reference, B2+ΔB4 and B3+ΔB1 can be separated from the b signal, and B2>ΔB4. Since B3>ΔB1 (
Since B2 and B are applied to the tracks of the magnetic head, the output is large, but the Ba) rack and Bt track are 3 track pitches away from the A3) rack played by the magnetic head, so their output is relatively small)B2+Δ
B4zaB2. B3+ΔB1+B5, and B2 and B3 can be separated. By comparing the sizes of B2 and B3, it is possible to identify whether the human head is shifted to the B2 side (left side) or B5 side (right side) when playing the M3 track. truck and 8
3) Correct tracking can be achieved by controlling the height position of the muhenod so that the levels of reproduction signals from the racks are equal. If the B head is B, then the output of the output terminal 3 of the adder 2 of the comb filter when reproducing the rack is as shown in Fig. 4 a', and the output of the output terminal 5 of the subtractor 4 is as shown in Fig. 4 b'. By controlling the reproduction signal processing circuit in this manner, correct reproduction tracking can be similarly performed when reproduction is performed by the B head.

In this case, the B head recording track signal component is output to the addition circuit output of the comb filter, and only the A rad recording track signal component is output to the subtraction circuit side, so that the track components recorded by the human head and the B head are separated. It turns out.

Next, the basic configuration of the reproducing circuit system for obtaining the double racking error signal will be explained using FIGS. 5 and 6. FIG. 5 is a block diagram of the reproduction circuit system, and FIG. 6 shows waveforms of various parts in FIG. In FIG. 6, the magnetic head 1
The regenerated signal is amplified by a regenerative amplifier 2 via a switch SW1 connected to the reproducing side (PB terminal), and its output is supplied to a low pass filter 4 (hereinafter referred to as LPF) and a terminal 3. Terminal 3 is sent to a video signal processing circuit (not shown). A tracking control pilot signal a (hereinafter referred to as a burst pilot signal) is obtained by the LPF 4. It is assumed that the magnetic head 1 is scanning the recording track 3 shown in FIG. At this time, the output of the reproduced burst high lot signal as shown in FIG. 6a is obtained.

pl and p3 are signals in which the main pilot signal recorded on track B3 and the error pilot signal (crosstalk component from the adjacent track) recorded on track B3 are superimposed. Also, burst pilot signal P2. P4 is an error pilot signal recorded on track B2. The phase inversion circuit 5 is a circuit for making the phases of the burst pilot signals from the main track to be reproduced the same. In this embodiment, phase inversion is performed on the B track, and when the B track is reproduced, the reproduced burst pilot signal is inverted every 2H to obtain signals that are all in phase. Since all the reproduction signals of the Mutrak are reproduced in the same phase, it is not operated when the Mutrak is reproduced. This phase inversion circuit 5 is controlled by obtaining a head switching signal (hereinafter referred to as a switching pulse) supplied from a terminal e and a 1/4 fH signal supplied from a terminal 7 via a NAND circuit 8. The output of the phase inversion circuit 5 is 2
A sum and a difference signal are obtained from the pre-delay and post-delay signals supplied to the H delay line 9. From the obtained sum signal, only the burst pilot signal reproduced from the main track is extracted. Further, as the difference signal, only the error pilot signal reproduced from the adjacent track is extracted. The extracted sum and difference signals are supplied to LPFlo and LPF11. From the LPF10 and I, PFi1,
The signals shown in FIGS. 6 and 6 are obtained. In Figure 6, P
A3 is the signal reproduced from the main track 5, and Pb2 in FIG.
2, Pb5 is a signal obtained from track B3.

The error pilot signal C is sent to the peak hold circuit 12.
The peak value is held by the peak hold circuit 12. The peak value hold circuit 12 is 1H.
The 9bit value hold circuit 12 is configured to be reset by the reset error e every time, and outputs a hold value according to the error error signal output that is reproduced every 1H.

(Figure 6d). On the other hand, the output from the LPF 10 is supplied to a sampling pulse shaping circuit 13. The sampling pulse shaping circuit 13 generates a pilot signal reproduced from the main track for approximately 1!2H period and 1.2H period, respectively.
Sampling pulses f and g delayed by 5H period are created, and the error pilot signal d of the sampling and holding circuit 14 and the sampling and holding circuit 16 is sampled and held in the sampling and holding circuits 14 and 16, and the error pilot signal C is Signals corresponding to the reproduced outputs of Pb2 and Pb0 are supplied to the differential amplifier 16. In the differential amplifier 16, the PB2 and Pb0
are compared in level, and a signal corresponding to the difference in power between the two rivers is obtained.

The signal obtained from the differential amplifier 16 is a signal corresponding to the track deviation. This is the track As shown in Figure 2.
When the magnetic head 1 performs reproducing scanning, the magnetic head 1 reads B3.
) When scanning is shifted toward the rack side, the error pilot signal P83 level reproduced from track B5 becomes high, and when scanning is shifted toward the rack side, the error pilot signal FB2 level reproduced from track B2 becomes large. Therefore, the PBs level becomes smaller. Therefore, if the error pilot signals PB2 and Pb5 reproduced from tracks B2 and B3 are controlled to have the same level, the magnetic head 1 can scan over the track 3. As is clear from FIG. 2, when the magnetic head 1 scans the A track and when the magnetic head 1 scans the B track, there is a difference in the track deviation direction of the magnetic head 1 and the level of error pilot signals obtained from both adjacent tracks. The relationship is in the opposite direction. For example, when the magnetic head 1 reproduces and scans the main track, 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 is the track located on the right side of the paper. When the magnetic head 1 reproduces and scans the B track, the track in which the burst pilot signal is recorded at the same position as the burst pilot signal reproduced from the main track B at this time is located on the left side on the paper. . Therefore, it is necessary to reverse the polarity of the tracking error signal obtained between the head and the B hect. Inversion circuit 17 shown in FIG.
It was set up for the doves. The inverted signal and original signal (non-inverted signal) from the inverting circuit 1 are sent to the switch SW.
Supply to 2. The switch 8W2 is switched by the head switching pulse of the terminal 18, and the inverted signal and the original signal are alternately outputted, and an output signal is obtained. This signal is a tracking error signal, and when the magnetic head deviates to the right with respect to the recording track, for example, a higher voltage than the on-track voltage is obtained.
When shifted to the left, a lower voltage is obtained. The tracking error signal is separated into independent error signals 1 and j by gate circuits 19 and 2o. These signals output a tracking error signal only while each head is in contact with the tape, and hold the value of the previous error signal while the other head is in contact with the tape. Circuits 21 and 22 are drive circuits for piezoelectric elements, and drive piezoelectric elements 23 and 24.

With the above configuration, by driving the piezoelectric element according to a relatively high frequency (-fH) tracking signal and controlling the height direction position of the rotating head, sufficient gain can be achieved even for track bending of several tens of Hz. 9))
It is possible to configure a racking control system.

In this embodiment, a detailed explanation of the recording system is omitted, but to briefly explain the recording of the burst high lot signal for tracking, as is well known, the recording of the video signal in VH3 VTR etc. The luminance signal is converted to FM modulation, and the chroma signal is converted to FM modulation, and the chroma signal is converted to the color subcarrier frequency fC (for NTS C signals = 3).
．． The frequency is converted from 5796 us [MHz]) and recorded as a low frequency (for example, 755 KH2 in 48 fH) superimposed on the above-mentioned FM modulation signal. In the case of this embodiment, it is also necessary to record a burst pilot signal for tracking (in this embodiment, 126 [Saturday] in 8 fH), and a low-frequency conversion color signal is superimposed on the FM modulation signal. The burst high lot signal is superimposed and recorded.

The center frequency of the burst pilot signal in the present invention is 8
・It is 126 [KH2] in fH, but it is a burst signal, and the frequency spectrum of the pilot signal is 1
2e (KHz)±12oCKHzE is distributed in the vicinity. Therefore, the LPF4 is set to 126 (KHz), for example.
If you extract the burst pilot signal using a resonant circuit, ringing or the like will occur in the extracted burst pilot signal, making it impossible to extract a normal burst pilot signal. Therefore, the LPF 4 needs to extract in a band of about 250 CKHz'l to 300 kHz (KHz: l). When extracting with an LPF of such a band, the band of the above-mentioned low-frequency conversion color signal is in the low range. It is distributed from 200 (KHz) to 25Q (KHz'l), and the chroma signal cannot be completely removed.
It may leak into the burst pilot signal. In addition, noise such as leakage of the horizontal synchronization signal of the video signal from around the ground during playback, jump from the air, etc. may be superimposed on the burst pilot signal. When this noise increases, as mentioned above, the peak value is held and sampling and hold is performed, and the period other than the burst pilot signal (between the pilot signal and the next pilot signal because it is burst-like) If noise is present and the noise is larger than the burst pilot signal, peak value hold may be performed with that signal, which may cause the tracking control system to malfunction as described above. In addition, when there are multiple recording/reproducing magnetic heads as in this embodiment, at the time of switching the magnetic heads during reproduction, the level fluctuation due to the difference in the reproduction phase from the M and B heads, or the response characteristics of the rising edge of the switching circuit. Due to level changes, etc., envelope fluctuations in the switching section occur, resulting in level fluctuations in the burst pilot signal, resulting in malfunction of the tracking control system as described above. If the tracking control is not carried out normally, problems such as a distorted reproduced image or deterioration of the S//H of the reproduced signal will occur, as is well known. Next, to briefly explain the necessity of the peak value hold circuit 12, as mentioned above, the burst pilot signal is recorded during the blanking period of the horizontal synchronization signal, and the center frequency of the burst pilot signal is 8·fHHI.
326 CKHz], therefore the synchronization is about 8 [MS]. Also, the blanking period of the horizontal synchronization signal is approximately 10 (MS)
It is. Therefore, only one cycle period can be recorded during the blanking period, and recording is performed in bursts of one cycle. Therefore, in order to perform sampling hold without peak value hold, the above period (6 to 10 (MS)
)). However, as mentioned above, the sampling pulse is formed by the horizontal synchronization signal of the playback signal from the main track, and the error signals from both adjacent tracks of the main track are sampled and held, and H jumps may occur for some reason during recording. 180') If there is an error, etc., the reproduction timing of the error pilot signal will be shifted and the peak value will not necessarily be held. Therefore, by inserting the peak value hold circuit 12 described above and lengthening the peak value hold period (approximately 40 (MS) in this embodiment), sampling and holding is always performed at the peak value.

As described above, the peak value hold circuit 1 of the present invention
The purpose of this invention is to prevent malfunctions due to changes in the peak value held at 2, and one embodiment of the present invention is shown in FIGS. 7 and 8. In FIG. 7, parts having the same functions as those in FIG. 5 are given the same numbers. In FIG. 7, a head switching pulse (k in FIG. 8) is supplied to the terminal 6, and the gate generating circuit 27 generates a period (1
A gate signal l having a width of 3H period) is generated. The output l from the gate generation circuit 27 is supplied to an AND gate circuit 29. A reproduced horizontal synchronizing signal m is supplied from the terminal 26 and input to the gate generating circuit 28. The gate generation circuit 28 generates a gate pulse n having a burst pilot signal insertion period width in synchronization with the reproduced horizontal synchronizing signal, and supplies it to the AND gate circuit 29 .

In the AND gate circuit 29, the gate generator 27.2
An AND gate signal 0 is generated from signals m and n from 8 and is supplied as a control signal to switch SW3. With such a configuration, when the operation explained in FIG. 5 is performed, the tracking signal a taken out is turned into a signal with the head switch a' in FIG. This is what was done.

As described above, the present invention provides a method in which a burst pilot signal recorded intermittently superimposed on an information signal for tracking control is extracted during reproduction, and tracking is controlled by the level of the reproduced burst pilot signal. Since the structure is such that only the section where the burst pilot signal is inserted is gated to extract the burst pilot signal component, there is no possibility of errors caused by noise occurring outside the section where the burst pilot signal is inserted. In addition, in sections where fluctuations in the playback signal level near the time of head switching may change significantly, the burst pilot signal is not extracted and control is performed according to the burst pilot signal level before that section. This also eliminates malfunctions caused by fluctuations in reproduction level when switching heads.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the timing relationship of the video signal (ironoto signal) used in the present invention, and Fig. 2 is a diagram showing a part of the recording pattern of the pilot signal used in the present invention on the magnetic tape and the magnetic head. Fig. 3 is a block diagram showing an example of a comb-shaped filter; Fig. 4 shows the recording pattern in Fig. 2. The magnetic head shown in Fig. 2 reproduces the M3 track and B3) rack. FIG. 5 is a block diagram showing the basic configuration of the tracking control method of the present invention, FIG. 6 is an operation waveform diagram of FIG. 6, and FIG. 7 is a block diagram showing an embodiment of the present invention. , FIG. 8 is an operating waveform diagram of FIG. 7. 1...Magnetic head, 2...Regenerative amplifier, 4゜10.11...Low pass filter, 5.
... Phase inversion [1, e + 1s ... Head switching pulse input terminal, 8 ... Nandt gate circuit, 9 ... Delay circuit, 12 ...・
...Peak hold circuit, 13...Sampling pulse generation circuit, 14.15...Sample hold circuit, 16...Differential amplifier, 19°20
......gate circuit, 21.22...drive circuit. IT diagram Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] A video signal on which a tracking control pilot signal of a constant frequency is intermittently superimposed for a predetermined period is extracted by sequentially switching a plurality of magnetic heads, and the tracking control signal is extracted. A tracking control method characterized in that the position of the magnetic head is controlled according to a level until the next tracking control signal.