JPS58224435A - Magnetic recording and reproducing device having automatic scanning function - Google Patents

Abstract

PURPOSE:To reduce guard band width and to improve recording density, by reproducing a pilot signal recorded in a guard band part through auxiliary and main heads by the main head, and controlling tracking. CONSTITUTION:Pilot signals of which frequency is different each other are recorded in a tape to be herically scanned by an auxiliary head having wide width. When these signals are recorded in the main head, the pilot signals corresponding to the record 2 are erased and the pilot signals 4, 5 of which frequency is different each other are kept recorded in the guard band parts on both sides of the record 2. If tracking is controlled so that the reproduced outputs of the parts of the signals 4, 5 which are generated due to crosstalk at the reproducing by the main head go to ''0'', tracking control is performed highly accurately without using a control head or the like. In said constitution, the guard band width is reduced and the recording density is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention has a main head and an auxiliary head, and has three cylinders.
Wrapping less than 60° is on magnetic tape wrapped in Ω at the corner.
The present invention relates to a five-head helical scan VTR in which the main head records most of the video signal and the auxiliary head records the vertical blanking period. This invention relates to a VTR equipped with a means for automatically scanning the main head without shifting the main head.

In the so-called 1,5 head system found in the C format of 1-inch helical scan VTRs for broadcasting, it is not possible to use an azimuth head, so a wide guard band area is provided to prevent adjacent tracks from being played during playback. However, there is a drawback that the recording density on the magnetic tape is effectively reduced.

The present invention has been made to eliminate the drawbacks of the prior art as described above, and therefore, an object of the present invention is to reduce the guard band width and increase the effective recording density. 1, 5-head helical scan VTR
Our goal is to provide the following.

The present invention uses the auxiliary head of a 1.5-head VTR to send a tracking pilot signal to the guard area on the tape.
The pilot signal is recorded in advance in a way that extends beyond the track area, and then the main head overwrites and erases the previously recorded pilot signal except for the guard area, and during playback, the tracking pilot signal is written in the guard band area using the main head. is reproduced and used to correct the track misalignment of the main head.

The present invention will now be described in detail with reference to the drawings.

Fig. 1 is an explanatory diagram showing the running system of a 1, 5 head type VTR to which the present invention is applied, Fig. 2 (α) is a top view of the tj cylinder section, Fig. 2 (A) is a view from the I side of the same; FIG. 5 is an explanatory diagram of the recording pattern on the tape.

See these figures. As shown in FIG. 1, the magnetic tape 1 is spirally wound around the cylinder 8 at an angle slightly less than 360 degrees. As shown in FIG. 2, the cylinder 8 is an upper cylinder 25 that rotates with a lower cylinder 24! l
The upper cylinder 26 has a main rotating magnetic head 6 (hereinafter referred to as the main head) and an auxiliary rotating magnetic head 7 (hereinafter referred to as the auxiliary head) in the arrangement relationship shown in FIG. Fixed.

In this example, although not shown in the figure, the main rotating controller 6 is fixed to the free end of a piezoelectric bimorph supported on a cantilever like the playback head of a broadcast helicopter VTR, and rotates. The axial position can be controlled by external electrical signals. As shown in FIG. 2, the auxiliary head 7 is
It is attached at a position preceding the main head 6, and is arranged so as to record at a preceding position on the magnetic tape 1.

FIG. 1 shows the tape running system of this example. A supply reel 9 and a take-up reel 21 are arranged within the tape 5 cassette 22. Magnetic tape 1 fed out from supply reel 9
is tape guide 10 in cassette, tenshiranbosuto 11
, the full-width erasing head 12, the moving tape guide 15.14, and is wrapped around the cylinder 8 approximately 5,600 times. The magnetic tape 1 coming out of the cylinder 8 is moving tape guide +5.16
, audio head 17, capstan 19, pinch roller 1
8. The tape passes through the tape guide 20 in the cassette and is wound up onto the reel 21. 15, 14, 15, and 16 are movable tape guides for pulling out the magnetic tape 1 from inside the cassette 20 and winding it around the cylinder 8. The rotation of the upper cylinder 25 is synchronized with the field period of the video signal, and in the case of an NTSC signal, it rotates at 560 rpm.

A recording pattern recorded on the magnetic tape 1 is shown in FIG. 2 is a record of the video signal recorded by the main head 6; 4
5 is a record trace of a pilot signal of frequency C recorded by the auxiliary head 7, and 5 is a record trace of a pilot signal of frequency 12 recorded by the auxiliary head 7. 5 is a recording trace of the vertical retrace period portion of the video signal recorded in the auxiliary hect 7.

As is clear from FIG. 2.5, the pilot signal record trace 4.5 is recorded before the video signal record trace 2, and furthermore, the pilot signal record traces 4 and 5 are one of the first in the main hector 6. The head positional relationship is selected such that the parts are overwritten and erased. That is, the auxiliary head 7 is arranged in a positional relationship to scan the center of the girt band portion of the main head, and its head track width is selected to be slightly wider than the girt band width.

As shown in Figure 5, the pilot signal is not recorded in the guard area between the main head recording area and the auxiliary head recording area, but this is done in consideration of the case where there is another signal track in the tape longitudinal direction in this area. However, especially if there is no such track, pilot signals may be recorded continuously. Note that the pilot signal f1. C is recorded superimposed on the video signal. As the pilot signal, it is desirable to use a frequency outside the band used for the video signal. For example, when recording the video signal by FM modulation, it is preferable to use a low frequency side outside the band, or to separate the video signal into a luminance signal and a color signal. FM luminance signal
If you want to convert the frequency of the color signal to the lower side of the luminance FM signal band and record it with eyebrow/f'i FM modulation, the luminance FM
It is preferable to provide it between the signal and the low color signal band, or on the lower side of the low color signal band. Further, the pilot signal frequency is alternately switched between 11 and fl for each field, that is, for each scan. The pick-up record trace 6 and the record trace 4 (or 5) in its extending direction record pilot signals of the same frequency.

By doing the above, as shown in Figure 6, fl or f can be placed on the left and right guard band parts of the main head record trace.
l pilot signals can be recorded alternately. C. If f2 is a low frequency signal, when the main head 6 scans the recording trace 2, as a crosstalk component from the adjacent part,
In order to reproduce the pilot signal of frequency flj2, if the position of the main head 6 is controlled so that the component of frequency C is equal to the component of frequency 12 among the reproduced pilot signal components, correct scanning can be achieved.

As shown in Figure 3, the main head scanning position and the auxiliary head scanning position deviate in the scanning direction, but this deviation is actually about 1/15 of the total length of the recording trace 2, and is caused by this deviation. The guard band portion of the pilot signal that is not recorded, this is the portion shown at 25 in Figure 5, is small, and even if a method such as holding the tracking error signal at its previous value is used in this portion, , there is no problem in practical use. Also, the amount of track deviation cannot be detected in the 30th part of the recording trace, but since this part is short and synchronous, there may be some s.
There is no problem with 7y deterioration.

As is clear from FIG. 3, the pilot signal frequencies of the left and right guard band portions of the main head recording trace 2 are alternated. If the current left girt band is C and the right girt band is f8, then in the next track the left girt band will be fl and the right girt band will be ft. Therefore, in order to match the polarity of the tracking deviation amount, it is necessary to alternately invert the polarity of the difference between the pilot signal reproduction output level of fl and the pilot signal reproduction output level of 13 for each track. This can be determined depending on whether the pilot signal frequency detected from the record trace 6 is 12 or fl.

This will be explained with reference to FIG. In Figure 5, when the auxiliary head has finished scanning the recording trace 5'.

It is assumed that the head arrangement relationship is determined so that the main head is located at the starting end of the recording trace 2'. In recording trace 6, the pilot signal of frequency f2 is reproduced, so when there is a pilot signal of fl in the vertical retrace part, the left guard band of the subsequent video signal recording trace is the pilot signal of frequency ft, the right The guard band becomes a pilot signal of frequency 12. In the next field, the pilot signal is detected in the vertical retrace part, and the pilot signal frequency in the guard band part is opposite to the above case on the left and right.If the positional relationship between the auxiliary head and the main head is set correctly, Tracking error signals can be detected without error.

FIG. 4 is a block diagram showing one embodiment of the present invention. Refer to the same figure. A signal reproduced from the magnetic tape 1 by the main head 6 fixed to the free end of the piezoelectric bimorph 26 is amplified by the preamplifier 27 and supplied to the switch 29. On the other hand, the reproduction signal from the auxiliary head 7 is transmitted to the preamplifier 2.
8) is amplified and also supplied to the switching device 29. The switch 129 is a switch that receives a head switching signal and switches and outputs only the control amount corresponding to the playback section of the main head 6 and the auxiliary head 7, respectively. The output of the switch 29 is demodulated into a video signal by a video signal demodulation circuit 50. The head switching signal is output from a switching signal generator 51 in response to an output from a head tact signal generator 50 provided in the cylinder section.

On the other hand, the output of the switch 29 has a center frequency of fl.
and fl bandpass filters 52 and 55. The outputs of the bandpass filters 52 and 55 are input to envelope detection circuits 54 and 35, respectively.

The level difference between the outputs of the envelope detection circuits 54 and 55 is sent to a difference detection circuit 66. A 57-digit polarity determining circuit determines whether to invert the polarity of the output of the difference detection circuit 66, or output it as is without inverting it, like the output of the flip-flop 400. The outputs of the envelope detection circuits 54 and 55 are sampled and shaped by the sampling selection shaping circuits 58 and 59, and the output only during the period in which the auxiliary head is reproducing, which is determined by the head switching signal, is sampled and shaped. 400 set, fed to the reset input. That is, for example, if a pilot signal with a frequency of ft is detected in the vertical retrace portion of the auxiliary head 7, the output of the flip-flop 40 is set to a high level, and if a pilot signal of f2 is detected, the output of the flip-flop 40 is set to a low level.

The output of the polarity determining circuit 37 is supplied to a correction circuit 41, which determines a period in which no tracking error amount is detected from the head switching signal, and holds the tracking error amount immediately before this period, for example, throughout this period.

The output of the correction circuit 41 is a tracking error signal,
This is supplied to a low pass filter 42, and the output of the low pass filter 42 controls the capstan 190 rotations.
The tape running is controlled so that the tracking error signal becomes 0, and the tape running is controlled to the correct state. The tracking error signal is also supplied to the piezoelectric bimorph control circuit 45, which controls the piezoelectric bimorph 26 to set the tracking error amount to 0 even for high-frequency track deviation amounts and to correctly determine the head position. Let me.

The position of the main head 6 is adjusted to the side.

44 is a drive amplifier for driving the pressure-raised bimorph. Of course, if the tracking error of high frequency components can be ignored, the piezoelectric bimorph may not be used, the main hector 6 may be fixed to the upper cylinder 25, and only the capstan rotation may be controlled. Moreover, for the displacement of the main head 6, not only the piezoelectric bimorph but also other electromechanical transducers such as electromagnets may be used.

11 In the explanatory diagram of the recording pattern shown in FIG. 5, the tracking pilot signal is recorded continuously, but it may be recorded intermittently. For example, in the case of a tape pattern with R alignment, the frequency 1 is intermittently applied only to the guard band portion adjacent to the horizontal retrace portion of the main head recording track 2.
Pilot signals 1 and 12 may be recorded. A part of the recording pattern in this case is shown in FIG.

In FIG. 5, reference numeral 47 indicates a horizontal retrace section of the video signal, and reference numeral 48 indicates a pilot signal recording portion of frequency f1. 49 indicates a pilot signal recording portion of frequency 12. In this case, the influence W of the pilot signal on the reproduced image can be further reduced. Also f,
, f2 using two-frequency pilot signals, 1
The left and right pilot signals may be distinguished by using a pilot signal of different frequencies and recording the phase of the pilot signal while changing its phase.

In this case, for example, a pilot signal with a reference phase is recorded in the vertical retrace section, and during playback, this is used as the reference phase, and the phase of the reproduced pilot signal is determined to determine the amount of tracking error and its direction. I can do it.

Furthermore, if the main head is not a recording/reproducing head, but the recording head and the reproducing head are separate, it is also possible to reproduce the pilot signal with the recording head during reproduction. An example of the head arrangement in this case is shown in FIG.

In the figure, 45 is a recording main head, and 46 is a reproduction main head. Further, G indicates a helad gap.

Generally, the head gap width of a recording-only head is wide, making it unsuitable for high-frequency reproduction, but since the pilot frequency is generally a low frequency, reproduction at a sufficient level is possible. Therefore, as shown in FIG.
By aligning the center of the head track width of the main playback head 46 with the scanning direction and making the head track width of the playback head a little narrower than that of the recording head, fluctuations in the playback level can be reduced and furthermore, the influence of the pilot signal on the playback screen can be reduced. This enables playback with less distortion. When a piezoelectric bimorph 26 is used, these two kerihenodes may be fixed on the same piezoelectric bimorph.

According to the present invention, since capsun control is performed using pilot signals, the control head conventionally used in helical scan VTRs becomes unnecessary.

According to the present invention, auto-tracking using a tracking pilot signal is possible without increasing the number of heads, and the reproduction circuit can also be made extremely inexpensive.

In addition, there is no need for a control head, and by improving the frequency characteristics of the servo circuit, highly accurate tracking that follows track curves is possible, and complete compatibility and playback are possible with narrow recording track widths. This can be realized even in the case of 1, the guard band can be made extremely narrow, and the effective recording density can be increased.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the running system of a 1,5 head type VTR to which the present invention is applied, FIG. 2 (α) is a top view of the cylinder section, FIG. 2 (b) is a side view of the same, 4 is a block diagram showing an embodiment of the present invention. FIG. 5 is an explanatory diagram of a recording pattern on tape in another embodiment of the present invention. FIG. FIG. 7 is an explanatory diagram of head arrangement in yet another embodiment of the invention. Code explanation 1: Magnetic tape, 2: Main head recording trace, 4.5:
Pilot signal recording trace, 6: Main rotating magnetic head, 7: Auxiliary rotating magnetic head, 8; Cylinder, 26: Piezoelectric bimorph, 52.55;
bandpass filter. 71 fig. 2 fig. 1 228-f に fig.

Claims (1)

[Claims] 1) Has a main head and an auxiliary head, and has a 360° angle to the cylinder.
The main head records most of the video signal, and the auxiliary head records the remainder on a magnetic recording medium that is wound in Ω at the corner. In the magnetic recording and reproducing apparatus, means for pre-recording a tracking pilot signal in a guard band portion of a recording track recorded by a main head on the magnetic recording medium, a means for reproducing the pilot signal at the time of reproduction, and a means for reproducing the pilot signal during reproduction; A magnetic recording and reproducing device having an automatic scanning function, characterized by comprising a control means for detecting a deviation of the main head with respect to the recording track from the pilot signal and controlling the traveling position of the main head so that the deviation is eliminated. . 2. The magnetic recording and reproducing apparatus according to claim 1, wherein the pilot signal is a pilot signal composed of two frequencies.