JPS6217284B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a recording track tracking method in a magnetic recording/reproducing device for television signals, etc., in which a multi-channel magnetic head is used during reproduction, and the multi-channel magnetic head is adjusted according to track deviation. The present invention provides a method for automatic tracking by selecting one of the magnetic heads.

An azimuth recording method that utilizes azimuth loss has been put into practical use as a method for realizing high-density recording in magnetic tape recording and reproducing devices for television signals. This azimuth recording method uses magnetic heads with different head gap directions for recording between adjacent recording tracks. During playback, even when playing across adjacent tracks, the adjacent track signals are suppressed due to azimuth loss. This method obtains a reproduced signal without interference.

If such an azimuth recording method is used, even in a helical scan VTR, recording can be performed without providing a guard band between tracks, and the recording density can be significantly improved.

Although such recording is easy to achieve in a system in which two heads alternately record, it is difficult to put it into practical use when a magnetic tape is wound 360 degrees around a rotating cylinder and recorded in one rotating head.

The one-rotation head system is advantageous over the two-rotation head system in terms of adjustment man-hours, number of parts, cost, etc., but since the azimuth recording method described above cannot be put to practical use, it is difficult to achieve high-density recording. teeth,
It has been considered to be inferior to the two-head system.

In addition, as a method for realizing high-density recording without using azimuth recording, a deviation from the recording track is detected during playback, and a piezoelectric element on which a magnetic head is mounted is controlled to utilize electro-mechanical conversion. Various methods have been proposed for automatically tracing a track by mechanically deflecting the reproducing magnetic head, and some methods have already been put into practical use.

However, in the case of automatic tracking by controlling the piezoelectric element, the circuit for driving the piezoelectric element is complicated, and a high voltage (for example, 100 V or more) is required to obtain the desired amount of deviation. 2-head method In this case, there are problems such as the difficulty of regulating the height difference between the two heads during recording, and when such a system is introduced, the device becomes complicated and expensive.

In contrast, the present invention uses a multi-channel reproducing magnetic head to reproduce a recorded track, and also switches to an optimal channel according to the amount of track deviation to reproduce a reproduced signal without interference from adjacent tracks. This method allows tracking to be performed entirely electronically, and will be explained in detail below.

FIG. 1 is a diagram for explaining the general configuration when the present invention is applied to a one-head type VTR.

A recording magnetic head 2 and a reproducing magnetic head 3 are mounted on a rotating cylinder 1, and a magnetic tape 4 is spirally wound around the cylinder 1 over approximately 360 degrees. 5
The tape 4 is driven by the pinch roller 6. 7 is an audio signal recording/reproducing head.

FIG. 2 shows the magnetization pattern on the tape recorded by the apparatus of FIG. Recording head 2
The video signal recorded by......T _o-1 ,
They are recorded as inclined tracks on the magnetic tape 4, such as T _o , T _{o +1 .} . . , and a non-recording band (guard band) G is provided between the tracks. Also, audio signals are recorded on the tape end 8 in the longitudinal direction. In the case of such one-head recording, a signal deletion portion occurs, and various correction methods have been proposed for this deletion portion.

The reproduction head 3 used in the present invention is shown in FIG.
As shown in the example, it is a composite head consisting of three magnetic head elements H _A , H _B , and H _C , and the gaps g _A , g _B , and g _C of each head element are on a straight line (inline). They are lined up.

Next, an example of signal processing during recording and FIG. 4 will be described. The video signal inputted from the terminal 9 is guided to the FM modulation circuit 10 where it is converted into an FM modulated wave, passes through the adder circuit 11, and is guided to the recording magnetic head 2 through the recording amplifier 12. On the other hand, a horizontal synchronizing signal is separated from the input signal by the circuit 13 and guided to the flip-flop circuit 14, which outputs the pilot signal f from the oscillator 16.
_P is gated every other horizontal scanning section by the circuit 15,
The adder circuit 11 adds the signal to the FM wave described above and records the result. Note that color signal recording is omitted because it is not directly related to the present invention. As shown in FIG. 5, the recording magnetic pattern is such that the horizontal synchronizing signal recording position is aligned perpendicularly to the recording track, and the signal deviation α _H with respect to the adjacent track is 0.5H (H
is the recording length of one horizontal scanning period), then the pilot signal f _P is recorded in alternate horizontal periods every 1H, and the recording position of the pilot signal is shifted between adjacent tracks.

As mentioned above, the condition for the horizontal synchronizing signal recording positions of each track to be lined up in a straight line (H alignment condition) is that in the case of the 1-head system, α _H is expressed by the following formula: α _H =
This holds true when 2n-1/2.

V _t =α _H・f _V・(πD) ² /(n _H ±α _H ) ・(πD) ² −W ² …(1) However, V _t : Tape running speed f _V : Field frequency (for NTSC signal 60
Hz) D: Cylinder diameter n _H : Number of lines in one field W: Video signal recording width on the tape α _H : Amount of signal deviation between adjacent tracks (in H units), and the compound is the cylinder rotation direction and tape running If the directions are the same, it is +, and if they are opposite, it is -.

If the specifications are selected to satisfy equation (1), the H alignment condition is established, and the case of FIG. 5 corresponds to the case where α _H =0.5 and the cylinder rotation direction and tape running direction are the same. As shown in FIG. 5, when α _H =0.5, the odd-numbered horizontal synchronization period and the even-numbered horizontal synchronization period correspond between adjacent tracks, so the output pulse of the flip-flop 14 in _FIG.
If gated, the pilot recording periods will automatically be arranged alternately between adjacent tracks as shown in FIG.

When α _H = 1.5, the odd-numbered horizontal synchronization sections are aligned between adjacent tracks, so the flip-flop shown in FIG. 4 is reset for each field to invert the polarity of the output pulse. Therefore, it is possible to perform recording so that the pilot signal recording sections do not correspond between adjacent tracks.

If the cylinder rotation direction and tape running direction are opposite, the recording pattern will change, but recording can be done using the same concept.

Further, even if α _H in equation (1) is not 2n-1/2, it is possible to record the pilot signal recording periods so that they are not aligned between adjacent recording tracks, although the configuration is somewhat complicated.

Note that the pilot signal f _P can be recorded in a frequency band lower than the frequency band of the lower band of the FM wave, and when recording a color signal using known low frequency conversion, it is recorded in a frequency band even lower than the color signal band. Can be recorded.

Now, a method for reproducing the signals recorded in this way using a composite magnetic head as shown in FIG. 3 will be described below.

As shown in FIG. 6, the composite head 3 (H _A , H
_B , H _C ) are assumed to scan immediately like broken lines, and the recorded tracks T _o-1 , T _o , T _o+1
Assume that it is curved as shown in the figure.

Immediately after the start of scanning each track during playback ( _PO point)
First, the central head H _B of the composite head is controlled so as to be located approximately at the center of the recording track T _o (described later).

Then, the reproduced signal from H _B is compared with the reproduced signals from H _A and H _B , and based on the comparison level difference, the head that best reproduces the signal on track T _o is selected from among the composite heads. Therefore, even if the track is curved, it is configured to reproduce a signal without beat interference with adjacent tracks. For example, in FIG. 6, between points _P2 and _P3 , the signal levels reproduced by the H _B and H _C heads from the track _To are reversed. Therefore, it is only necessary to switch from the H _B head to the H _C head between P ₂ and P ₃ . Also P ₄ and P ₅
In between, the H _C head is switched again to the H _B head.

Next, a configuration example for performing the above-described head selection will be explained with reference to FIGS. 7 and 8.

In FIG. 7, signals reproduced from composite heads H _A , H _B , H _C are transmitted to preamplifiers 17 and 1, respectively.
8,19. Then, a PG signal (or a reproduced vertical synchronization signal may be used) obtained from the head rotation phase, which is a signal corresponding to the scanning start point of each track, is led to the input terminal 20, and this signal triggers the monostable multi 21. Then, a pulse with a vertical blanking period or a little longer than that is generated at the output. During this pulse period, the pilot signal levels in the output signals of the preamplifiers 17 and 19 are compared, and the error signal (terminal 23) is fed back to the capstan motor to drive the heads H ₄ and _HC . The tape running system is controlled so that the pilot signal levels to be reproduced are equal. In this case, in order to compare the levels of the pilot signals reproduced at the same timing by heads _HA and _HC , the comparison is made at a timing different from the timing at which the pilot signals are reproduced by the _HB head. Therefore, if the tape running system is controlled so that the levels at which H _A and H _C reproduce the pilot at the same timing are the same, then at the start of track scanning, head H _B will be at the same level as shown in FIG. It is controlled to be located approximately at the center of the track T _o .

In this way, after the head H _B is controlled to be on the center of the track T _o immediately after the start of track scanning, the signals of the heads H _A , H _B , H _C are transmitted to the preamplifiers 17, 18, 19. are led to input terminals A, B, and C of switch 26, respectively, and one output selected from terminals A, B, and C is obtained at output terminal 27 of switch 26. A video signal demodulated by the reproducing circuit 28 is then obtained at the output terminal 29.

The switching signal of the switch 26 is the comparator circuit 24 and 2
The output of the preamplifier 17 and the output of the preamplifier 18 are led to the input of the comparator circuit 24, and the pilot signal levels of both inputs at the same timing are compared. . The output pulse of the detection circuit 30 is guided to the comparison circuit 24 so that the comparison timing is compared with the pilot signal timing detected by the pilot detection circuit 30 from the output of the output terminal 27 of the switch 26.

Similarly, the output of the preamplifier 18 and the output of the preamplifier 19 are led to the comparator 25, and the pilot signal levels in both input signals are compared at the timing of the output pulse of the pilot detection circuit 30. Also, in order to prevent the switching timing of the switch 26 from appearing on the screen, the horizontal sync signal is separated from the playback signal in the circuit 31 so that the switching pulse is generated at the horizontal sync signal timing, so that the switching timing of the switch 26 does not appear on the screen. 31 horizontal synchronizing pulses are applied to comparator circuit 2.
4 and 25, respectively.

The switch circuit 26 is connected to the contact B at the start of track scanning, and the signal from the head H _B is guided to the output 27. During the period when the output from the head H _B is greater than the output from H _A and H _C , the contact Connected to B. Then, when the output of H _A becomes larger than the output of H _B , the output of the comparator 24 becomes Hi level, and is connected to contact A, so that the output of the head H _A is guided to the output 27. Further, when the output of H _C becomes larger than the output of H _B , the output of the comparator 25 becomes Hi level, and the signal at the contact C is guided to the output 27 of the switch. Also, when the switch is connected to contact A or C, the output of head H _B is higher than H _A or H.
If the output is greater than the output of _C , the switch is connected to contact B. It is desirable that the switching timing of such a switch is performed during the horizontal blanking period as described above, but in some cases, it is instantaneous, so even if the timing is other than horizontal blanking, there will be no significant adverse effect.

Now, let's consider how much track curvature can be tolerated when a reproduction method such as that of the present invention is adopted. As shown in FIG. 9, the width of the recording track is T _W and the width of the non-recording band (guard band) between the tracks is G _W , and the dimensions of the reproducing magnetic head 3 are as shown in _FIG . Let the track width of H _B and H _C be H _W and the width between the heads be ΔH. in this case,
The state in which the head H _B is in the center of the recording track (P _b
position), and the position just before the track turns to the H _A side and the head H _A comes off the track (P _a
(position Pc), or the track is allowed to shift toward the H _C side and turn to the position just before the head H _C deviates from the track (position P _c ).

Therefore, if the amount of bending from the position of P _b to the position of P _a is Δl, then Δl≦T _W /2+H _W /2+ΔH (2) Also, if the other head ( _H 2H _W +ΔH≦T _W +G _W ...(3) In equations (2) _{and (} 3), suppose that the recording track width T _W
= 30 μm, guard band G _W = 5 μm, guard width between heads ΔH = 5 μm, then becomes.

In the current VTR, the amount of track bending is less than ±10 μm, which satisfies condition (4), and it is sufficient to make adjustments with a considerable margin for track bending.

In addition, when T _V = 20 μm, G _W = ΔH = 5 μm When T _W = 15 μm, G _W = ΔH = 5 μm Therefore, it can be seen that if |Δl|≦10 μm, sufficiently stable tracking is possible even when the recording track width is 15 μm or less.

Now, the composite magnetic head used in the above explanation requires a very narrow space ΔH between each head element, which is extremely difficult to achieve with a conventional wire-wound type magnetic head, but using vapor deposition technology. This can be fully realized by using a magnetoresistive head. In the case of a deposition head, it is easy to inline each gap of a composite head, and the required performance of a composite magnetic head such as that used in the present invention can be obtained.

The above explanation deals with the case where the recording track width is very narrow, but in the case of a wide track with a track width of several hundred microns, the desired composite magnetic field can be achieved using a conventional wire-wound head without using a vapor deposition head. You can get a head.

The specific example explained so far is the case where the present invention is applied to a one-head type VTR as shown in Fig. 1, but it is also possible to apply the present invention to a one-head type VTR as shown in Figure 1. It is clear that the present invention can be similarly applied to recording/reproducing systems. However, in this case, in order to separate the recording head from the playback head,
The problem is that the number of heads increases and the configuration becomes complicated. Furthermore, even if applied to a device that performs azimuth recording using a rotating two-head system and performs solid recording by eliminating guard bands between tracks, if the pilot signal is recorded on the low frequency side, the pilot signal will be free from the effects of azimuth loss. The present invention can be similarly applied to this case as well.

Furthermore, as shown in FIG. 3 as a composite magnetic head, the case has been described in which the track widths H _W of H _A , H _B , and H _C are equal; however, they do not necessarily have to be equal, and the track widths ( By adjusting the gain of the preamplifier depending on the sensitivity), it is possible to configure the same operation. Furthermore, even if three or more elements, four elements, or five or more elements are used as a composite magnetic head, the same idea can be applied and the head with the optimal tracking state can be selected (selecting multiple head elements). It is possible to obtain a reproduced signal without noise and without interference from adjacent track signals.

In addition, as a recording method of the pilot signal, as shown in Fig. 10, the pilot signal is recorded at equal intervals, and the pilot signal recording positions are not lined up with the adjacent tracks, but are recorded on the adjacent track one track apart. Even if you record so that the pilot recording positions line up,
A similar operation can be performed.

Also, as shown in Figure 11, the pilot signal is 1.
Although it is possible to record at a position where the tracks do not line up on adjacent tracks, the circuit processing becomes somewhat complicated.

Furthermore, even if the horizontal synchronizing signal recording positions of each track are not lined up in a straight line (if the H alignment condition is not satisfied), the pilot recording position can be set in the same way.

Furthermore, if the pilot signal is recorded as a continuous signal instead of intermittently, the pilot frequency can be changed and recorded for each track, and the optimum head can be selected by identifying the difference in frequency. .

In the case of still image playback, if the tape running direction and the rotating head running direction are the same as shown in Fig. 12, the head (H _A in the figure) located in the tape running direction during normal tape running will be The head with the higher output level (H A in the figure) compares the output with the center head H _B to see which one has the higher output at the start of each track scan, and selects the track that the head with the higher output level (H _A in the figure) starts scanning as the track during still image playback (in the figure). T _o ), and then playback is performed while comparing the output level from track T _o of the head H _A and the head located to the right, and the playback output level of the H _B head is greater than the playback output level from the H _A head. If this happens, switch to the H _B head, then compare the levels of the H _B output with the head H _C further to the right, and if the H _C output becomes greater than the H _B output, control is performed so that the head is switched to the H _C head. This will result in a still image with no blemishes. For example, at P ₁ point H _A , P ₂ , at P ₃ points H _B , P ₄ ,
At _P5 point, H _C is selected.

Furthermore, if the head scanning direction is opposite to the tape running direction, the head scanning angle when the tape stops running is in the direction of _the larger _one . The head and its track are used as a still image track.
Thereafter, while comparing the output level with the head located on the left side, if the output level of the left head becomes higher, the head may be switched to the left head.

In the case of slow motion playback, a noise-free slow motion playback image can be obtained using the same controls as in the case of still image playback.

It is clear that the present invention can also be applied to recording devices such as magnetic disk recording.

Further, it can be similarly applied to tape longitudinal recording or tape width recording methods.

As described above, according to the present invention, it is possible to perform reproduction that follows the curvature of a recording track without using a mechanically movable element such as a piezoelectric element, and there is no interference from adjacent tracks. Suitable for recording, etc. Furthermore, unlike piezoelectric elements, there is no hysteresis phenomenon or displacement due to changes over time, so stable reproduction is possible.

You can also obtain still images, slow playback, etc. without noise.

Furthermore, if the present invention is used, the control track conventionally used in VTRs becomes unnecessary.

[Brief explanation of the drawing]

FIG. 1 is a plan view of a main part for explaining the outline of the present invention, FIG. 2 is a diagram explaining an example of a recording pattern of the present invention, and FIG. 3 is a diagram showing an example of a composite magnetic head used in the present invention. FIG. 4 is a block diagram showing an example of the recording side circuit of the present invention, FIG. 5 is a diagram showing an example for explaining the signal recording pattern of the present invention in more detail, and FIG. FIG. 7 is a block diagram showing an example of the reproducing circuit configuration of the present invention, and FIG.
9 is a diagram showing the tracking state at each track scanning start point, FIG. 9 is a diagram for explaining the tracking margin, FIGS. 10 and 11 are diagrams for explaining other examples of recording signal patterns, and FIG. FIG. 12 is an explanatory diagram at the time of still image reproduction. 17, 18, 19... preamplifier, 20...
PG signal input terminal, 21...monostable multi, 22
... Pilot signal comparison circuit, 24, 25 ... Comparison circuit, 26 ... Changeover switch, 28 ... Regeneration circuit, 30 ... Pilot detection, 31 ... Synchronization separation circuit, H _A , H _B , H _C ... Reproduction head element.

Claims (1)

[Claims] 1. A magnetic medium on which television signals are sequentially recorded as a plurality of adjacent recording tracks is recorded using a composite magnetic head consisting of at least three magnetic head elements with magnetic reproduction gaps arranged in a straight line. The recorded track is reproduced, the main track output reproduced from the outer head element is compared with the main track output reproduced from the inner head, and head elements in the optimum tracking state are sequentially selected based on the comparison output. A magnetic reproducing system characterized in that it is configured to obtain a reproducing signal that follows the curvature of a recording track and is free from interference from adjacent tracks. 2. The composite head is composed of three head elements, and the central magnetic head element is controlled so as to be located approximately at the center of the reproduction track at the start of scanning of each recording track. The magnetic reproduction method according to item 1. 3 Pilot signals are not recorded in adjacent positions of adjacent tracks in the recording signal, but pilot signals are recorded in adjacent positions of one track, and the levels of the reproduced pilot signals are compared to determine the optimum head element. The magnetic reproducing system according to claim 1, characterized in that the magnetic reproducing system is configured so as to be selectively selected. 4. Claims characterized in that different pilot signals are recorded on tracks adjacent to the recorded signal, and the head element is configured to compare the reproduction levels of the reproduced pilot signals and select the optimum head element. The magnetic reproduction method according to item 1. 5. During still image or slow motion playback, at the start of each track playback, the playback outputs of one of the outer head elements and the inner head element are compared, and the head element with the larger output is identified from that track; 2. The magnetic reproducing system according to claim 1, wherein the magnetic reproducing system is configured to switch to the head element that reproduces the highest output from the track and reproduce the reproduced image without noise.