JPS5855573B2 - Tracking signal detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a rotating magnetic head type magnetic recording/reproducing device (hereinafter referred to as
In order to prevent so-called tracking deviation, a phenomenon that occurs when the magnetic head does not correctly scan the recorded track during playback due to elongation of the magnetic tape, dimensional errors between individual VTRs, and mutual dimensional errors in VTRs (simply referred to as VTRs). The present invention relates to a tracking signal detection device.

When a tracking error occurs in a VTR, a conventional method is, for example, to set up a tracking volume that can change the relative position between the magnetic head and the magnetic tape in advance, and then manually operate the magnetic head to record data during playback. Corrected the problem so that the tracks that were scanned were scanned correctly.

However, when considering the compatibility of VTRs, there is a drawback that such adjustments must be made each time for each VTR.

Furthermore, there is a limit to the response speed with only such adjustment using the tracking volume, and the limit is generally 30 Hz.

According to the present invention, adjacent tracks have different frequency differences fl, f2, . A plurality of pilot signals fn are recorded on each track on a magnetic tape by a magnetic head, and when reproduced, the pilot signals and the pilot signals from adjacent tracks reproduced due to tracking deviation are reproduced. It detects crosstalk components with signals, for example, fl, f2.・・・・・・
・The pilot signal fo is composed of four types of signals f1. f2. f
3. f4, and the relationship between the frequencies of these signals is fl-f
2 = f3-f4 to select pilot signal set to f3-f2 = f1-f4, fl = 110
KHz.

f:90KH2, f3=1ooKH2, f4-120K
When H2, f, -f2= f3- f4= 20
K) to lz f3- f2= f4- fl := 1
0 KHz, and each of these pilot signals f1 to f
4 is recorded on each track on the magnetic tape, and during reproduction, the frequency difference between the pilot signal reproduced through the reproduction head and the pilot signal from the adjacent track reproduced at the same time due to tracking deviation is compared, The comparison signal obtained is, for example, one of the double-side band components of the pilot signal obtained by separating the reproduced pilot signal and the pilot signal from an adjacent track that is simultaneously reproduced due to tracking deviation using a bandpass filter, and performing balanced modulation. By paying attention to the sideband components, the direction of tracking deviation can be determined, and since amplitude information is also extracted and multiplied, the amount of tracking deviation can also be detected.

That is, f, -f2=f3-f4=20KHz~f3
-f2-f4-f, = 10 KHz, and the frequency difference varies depending on the direction of track deviation of the reproducing head.

Therefore, by detecting the direction of track deviation between the playback head and the track on the magnetic tape using the comparison signal, and also extracting amplitude information, an attempt is made to obtain a signal for tracking the playback head. .

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described in detail below based on illustrated embodiments in order to further deepen understanding of the present invention.

FIG. 1 is a perspective view showing the main parts of the electromagnetic conversion system including the mechanical system of a general VTR used in the present invention. , 2b is attached.

Further, the rotary drum 1 is directly connected to a motor 4 which rotates at a frequency of 30 Hz via a rotary shaft 3, and is configured to rotate in the direction of the arrow (clockwise) in the figure.

Furthermore, 5 is a magnetic tape, and this magnetic tape 5 is wound around more than about half the circumference of the rotating drum 1, and its position is regulated by a guide post 6.6 so that it moves in the direction of the arrow in the figure.

Normally, the rotation locus of the magnetic heads 2at2b has a slight angle with respect to the longitudinal direction of the magnetic tape 5, and the track pattern of the magnetic tape 5 formed by applying signals to the magnetic heads 2a and 2b is As shown in FIG. 2, two magnetic heads 2a and 2b are formed alternately at a slight angle to the longitudinal direction of the magnetic tape 5.

However, depending on the moving speed of the magnetic tape 5, the track pattern formed in this way may have unrecorded parts (so-called guard bands) or adjacent tracks may be recorded overlapping each other. In the embodiment, the feeding speed of the magnetic tape 5 is selected to such an extent that there is almost no guard band between each track.

Next, a method for recording pilot signals f7 to f4 will be described in detail with reference to FIGS. 3 and 4.

FIG. 3 shows the already mentioned fl, f2. f3. This is a block diagram of a recording system for recording a pilot signal having a frequency of f4, in which a disc 7 is attached to one end of a rotating shaft 3 of a motor 4.

Further, one magnet piece 8 is adhesively fixed to the outer periphery of this disk 7, and this magnet piece 8 is attached to the rotating drum 1 shown in FIG.
It is configured to rotate together with the upper magnetic heads 2a and 2b.

Further, a magnetic head 9 is installed at a slight interval from the rotation locus of the magnet piece 8, and each time the magnet piece 8 passes in front of the magnetic head 9, a single A rotation pulse a (see FIG. 4) is generated.

This rotational pulse a is applied to the input terminal A of the delay circuit 10, and has a frequency of approximately 1/2 of one rotation period (30Hz) of the rotational pulse a.
A delayed pulse b (see FIG. 4) delayed by a period is obtained.

Normally, the magnet piece 8 is installed at the same rotational position as one of the magnetic heads 2a or 2b, and in this embodiment, the magnet piece 8 is installed at a position corresponding to the magnetic head 2a.

Therefore, the period (indicated by H in the figure) of the pulse (delayed pulse) b delayed from the rotational pulse a shown in FIG. The period when the delay pulse b is at a low level (indicated by L in the figure) corresponds to the period during which the other magnetic head 2b scans the magnetic tape 5.

This delay pulse b is applied to each input terminal A of the delay circuit LL12.

Here, one delay circuit 11 is triggered by the rising edge of the delay pulse b, and a delay pulse of about 1 ms is sent to its output terminal Q, and an inverted delay pulse C (see FIG. 4) is sent to its output terminal Q. can be obtained.

Similarly, the other delay circuit 12 is triggered by the falling portion of the delay pulse b, and a delay pulse of about 1 ms is sent to the output terminal Q, and an inverted delay pulse d (see FIG. 4) is sent to the output terminal Q. can get.

Next, each of these delayed pulses c, d is a logic circuit N
The signals are respectively applied to the AND gate 13, and a logic output e (see FIG. 4) is obtained.

This logic output e has a period twice that of the rotation pulse a, and corresponds to the leading edge of the magnetic tape 5 scanned by the magnetic heads 2a and 2b.

The logic output e is the aforementioned fl, f2 . f3. It is applied to the input terminal of a ring counter 140 for sequentially gating the pilot signal of frequency f4.

This ring counter 14 has flip-flop circuits 15 to
18. It is composed of a NAND gate 19 button and an inverter 20, and counts the logic output e as a count pulse, and rotates the only high level or low level as data at the cycle of the applied count pulse.

The ring counter 14 used in this embodiment rotates at a four-power count period, and gate signals f2g, h, and i (see FIG. 4) are obtained from the output terminals Q1 to Q4 of each flip-flop circuit 15 to 18.

Each of these gate signals f, g, h, i is the f1. f2
．． f3. Oscillators 21 each generating a frequency f4
, 22, 23, 24 to gate the outputs of the oscillators 21, 22.
, 23 and 24 are gated in accordance with the rotation of the magnetic heads 2a and 2b.

The oscillation outputs of the oscillators 21, 22, 23 and 24 become intermittent signals due to the opening and closing of the switches 25, 26, 27 and 28.
, l, m (see FIG. 4) are mixed to form the pilot signal f1. f2. f3. As f4, a recording/reproducing switch 29 and a rotary transformer 30 (rotating magnetic head 2a,
The pilot signal is supplied to the magnetic heads 2a and 2b via a transformer (transformer for transmitting a pilot signal to the magnetic head 2b).

Further, a recorded video signal from a recorded video signal processing circuit 31 for simultaneously recording video signals is supplied to the magnetic heads 2a and 2b, and is recorded on the magnetic tape 5 together with the pilot signal by these magnetic heads 2a and 2b. It is something that will be done.

Here, the processing circuit 31 frequency-modulates the luminance signal component, and modulates the color signal component at a low frequency (with a center frequency of 500
This is to form a recording system video signal which is frequency-converted and superimposed to a frequency (near KHz).

Next, the track pattern formed on the magnetic tape 5 by the pilot signals recorded in this manner will be explained.

Pilot signal f1 supplied to magnetic heads 2a and 2b
．． f2. f3. f4 is accurately changed from f1 to f2 to each track by a ring counter 14 and switches 25 to 28 that operate in synchronization with the rotation period of the magnetic heads 2a and 2b.
The data are sequentially recorded on the magnetic tape 5 as follows: f3→f4→f1→f2.

Next, a method for reproducing the pilot signal recorded on the magnetic tape 5 will be explained based on FIGS. 5 to 7.

Pilot signals including video signals are sent to magnetic heads 2a and 2b.
After being reproduced by the rotary transformer 30 and the recording/reproducing switch 29, the signal is applied to one input terminal X of the preamplifier 32.

Here, the preamplifier 32 is for amplifying and equalizing the characteristics of weak signals from the magnetic heads 2a and 2b.

t2 The other input terminal Y is applied with a delayed pulse b (see Fig. 6) that is delayed from the one-rotation pulse a (see Fig. 6), and is applied to the other input terminal Y. By switching overlapping portions recorded due to the magnetic tape 5 being wound for more than 100 degrees, a preamplifier output n (see FIG. 6) amplified by approximately 40 decibels is obtained from its output terminal Z. .

This preamplifier output n is applied to the input terminal IN of the reproduced video signal processing circuit 33.

This processing circuit 33 reproduces the recorded video signal recorded on the magnetic tape 5 to its original state.

The frequency-modulated luminance signal component is demodulated while limiting amplitude to reduce level fluctuations in the electromagnetic conversion system, and the color signal component is similarly demodulated to reduce time axis fluctuations in the electromagnetic conversion system. The frequency is converted to the original 3.58ME (z) and sent to the outside from its output terminal OUT as a reproduced video signal.

On the other hand, the output n of the preamplifier 33 is the recorded pilot signal fi t f2. Bandpass filters 34, 35°36.3 for separating f31 and f4 respectively
7 input terminals, respectively.

These filters 34 to 37 correspond to respective pilot signals f1t f27 f31 f4, respectively f
1 = 110 KHz, f2 = 90 KHz, f3
Separate = 100 KHz f4 = 120 KHz.

Furthermore, two types of pilot signals f1. f3 are applied to the input terminals of mixer 38, respectively.

Similarly, two other types of pilot signals f2. f4 is mixer 3
It is applied to the input terminal of 9.

Next, pilot signals f1. f3i- and f2. f4 are respectively applied to the input terminals of the balanced modulator 40.

However, as shown in FIG. 2, the track pattern formed on the magnetic tape 5 is recorded to such an extent that there are almost no guard bands between adjacent tracks, and the magnetic head 2a has the same shape for both recording and reproduction. , 2b. Therefore, when the magnetic heads 2a, 2b are correctly scanning the tracks on the magnetic tape 5, the pilot signals reproduced by the magnetic heads 2a, 2b are fl,
f2゜f3. One of the pilot signals of f4 is reproduced, but if a track shift occurs as shown in FIG. 7, the pilot signal from the adjacent track will be included in the reproduction.

For example, depending on the track deviation direction, fl and f2 ° fl and f4 [see Figure 7A] or f2 and f3 ° f2 and fl
(See FIG. 7B) will be reproduced.

Generally, the balanced modulator 40 is a circuit in which the applied carrier wave component is suppressed and only upper and lower band wave components exist, and the output of the balanced modulator 40 is as shown in FIG. Only when a track deviation as shown in the frequency spectrum occurs in F, the pilot signal f1 + f2t f3t f
4 tracking deviation component element 1±f2. f2±f3. f
, ±f4. f2±f1 is obtained.

However, in the embodiment of the present invention, as described above, the pilot signal frequency is set as fl-f2=f3-f4= during recording.
20KHz, f3-f2=fl-f4=10
KHz, and the output of the balanced modulator 40 is set to 2 KHz.
The crosstalk component of the pilot signal fx, f2t f3t f4 obtained by applying to the input terminal of the bandpass filter 41.42 selecting 0 KHz-%r and 10 KHz is 20 KHz or 10 KH
By determining whether it is z, the direction of track deviation can be known, and since the amplitude component is also extracted and multiplied, the amount of track deviation can also be detected.

Also, as is clear from FIG. 7, the recorded pilot signal f1. f3 and f2. The crosstalk components (hereinafter simply referred to as tracking myths) between the f4 track and the adjacent track (20 KHz, 10 KHz) are opposite even though the tracking deviations are in the same direction.

Furthermore, in order to construct a simpler circuit, the output of the bandpass filter 4L42 is passed through waveform shaping circuits 43 and 44, and then passed through the input terminal 4 of the tracking signal correction circuit 45.
6 and 47, respectively.

On the other hand, another input terminal 4 of the tracking signal correction circuit 45
The above-mentioned delay pulse b is applied to the magnetic heads 2a and 2b, and the tracking signal correction circuit 45
The tracking signal is inverted according to the rotation of the

The tracking signal thus obtained is applied to an electro-mechanical transducer 49, for example a piezoelectric element that is displaced by applying a voltage, and the relative positions of the magnetic heads 2a, 2b with respect to the tape 5 are determined by the electro-mechanical transducer 49. When controlled by the control output of 49, the relative positions of the magnetic heads 2a, 2b and the magnetic tape 5 can be automatically corrected, and tracking deviation can be automatically corrected.

1, the pilot signal of the frequency fl l f2 + f31 f4, band pass filters 34 to 37, balanced modulator 40, band pass filters 41 and 42, waveform shapers 43 and 44, tracking signal correction circuit 45, electrical
A negative feedback control loop is formed by the mechanical transducer 49 and the magnetic heads 2a and 2b, and the electro-mechanical transducer 49 is driven in a direction opposite to the track deviation direction of the magnetic heads 2a and 2b, thereby automatically correcting head tracking. It is possible.

In this embodiment, the frequencies of the pilot signals are f1=110KH2 and f2=90KHz, respectively.

f3=100 KHz, f4=120 KHz
However, for example, in a simple VTR, the video signal that is recorded and reproduced by being superimposed as a pilot signal has its luminance signal component frequency modulated to 3.8 MHz to 5 MHz, and has a center frequency of 3.58 MHz and an IMHz band. Since the color signal component is converted to a low frequency with a center frequency of approximately 500 KHz, the color signal component converted to a low frequency (100
KHz to IMHz) and the above pilot signal are recorded in a slightly different pattern, but this color signal component is usually at a low level, and the pilot signal is also recorded to the extent that it does not interfere with the low frequency converted color signal component. There is no problem if you set the level.

Further, in this embodiment, the pilot signal f1. f2゜f3.
As long as the frequency of f4 is within a range that does not affect the video signal recorded at the same time, this pilot signal can be easily configured as the tracking signal during playback described above without interfering with the video signal. .

As described above, since the tracking signal detection device of the present invention obtains the tracking signal by multiplying the pilot signal obtained by the band-pass filter, it is possible to detect the direction of track deviation based on the frequency, and also detect the amount of track deviation based on the amplitude information. can be detected.

This makes it possible to reliably detect both the track deviation direction and the amount of track deviation even when reproducing with a magnetic head that is wider than the recording track. If the system is implemented without auto-tracking, it will bring about a great effect.

[Brief explanation of the drawing]

Figure 1 is a schematic perspective view showing the rotating drum part of a video tape recorder, Figure 2 is an explanatory diagram of the track pattern recorded on the magnetic tape, and Figure 3 is a recording system for recording pilot signals on the magnetic tape. FIG. 4 is a waveform diagram of each part in FIG. 3, FIG. 5 is a block diagram of main parts showing an embodiment of the present invention, FIG. 6 is a waveform diagram of each part in FIG. 5, and FIG.
Figures A and B are explanatory diagrams showing the relative relationship between the magnetic head and the magnetic tape that have caused track misalignment, and FIGS. 7 0-F show frequency spectra after a state where track misalignment has occurred. 2a, 2b...Magnetic head, 5...Magnetic tape, 14...Ring counter, 21-2
4...Oscillator, 25-28...Switch, 34-37...Band-pass filter, 3B, 3
9...mixer, 40...-balanced modulator,
fl, f2. f3. f4...Pilot signal.

Claims (1)

[Claims] 1. A rotating magnetic head scans successive adjacent tracks on the magnetic tape at predetermined intervals, and each track on the magnetic tape is given the following information: fl-f2=f3-f4=
f3-f2=f, -f4 frequencies fl, f2. f3. The pilot signal f4 is sequentially and repeatedly recorded, and the pilot signals f, , f2 . f3. a bandpass filter that decompresses each pilot signal of frequency f4;
, or with a balanced modulator that multiplies f3 by the pilot signal of f2 or f4 fl f2"" f3
A tracking signal detection system characterized in that the frequency component of f4 + f3 h= fl f4 is detected, the direction of track deviation is detected using the frequency component, and the amount of track deviation is further detected using the level component. Device.