JPH0563850B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention sequentially scans a rotating head diagonally across a magnetic tape to record, for example, a video signal and other signals on the extension of the video signal track. The present invention relates to a track deviation correction device in a magnetic recording/reproducing apparatus configured to record a signal and to record a pilot signal superimposed on both signals.

[Prior art]

In a conventional two-head magnetic recording/reproducing device, a magnetic tape is wound diagonally approximately 180 degrees around a head drum having two rotating heads, and each rotating head is sequentially scanned in the diagonal direction of the magnetic tape. It runs at a constant speed to sequentially form video signal tracks. Recently, magnetic tape has been wound around the head drum more than 180 degrees, for example, 220 degrees, to make each recording track longer. Each recording track records video signals for 180 degrees, and the remaining portion is wrapped around, for example, 220 degrees.
A magnetic recording/reproducing apparatus is used which is configured to record PCM audio in a time-compressed manner, and further to record a tracking pilot signal superimposed on these signals. In this case, when one rotary head is recording a video signal, the other rotary head is simultaneously recording a PCM signal at the end of an adjacent track during a part of the period, and during this period,
The pilot signal superimposed on the video signal is
It is also superimposed and recorded on the PCM signal.

FIG. 1 is a plan view showing a head drum and a manner of winding a magnetic tape in a conventional magnetic recording/reproducing apparatus. As shown in FIG. 1, a magnetic tape 1 is wound diagonally around a head drum 2 over an angle of about 220 degrees. Two rotary heads 3a and 3b are mounted on the head drum 2 at an angular interval of 180°.
During the period when one of the rotary heads is scanning a portion of 220°-180° = 40° from the entrance of the magnetic tape 1, the two rotary heads 3a and 3b are in contact with the magnetic tape 1 at the same time. . When the magnetic tape 1 is scanned at a constant speed in the direction of the arrow in the figure, when one of the rotary heads forms a recording track, the other rotary head is simultaneously adjacent to the above-mentioned track during a period corresponding to the 40° portion. A track is now forming. The track formed in this way is then
Shown in the figure. As shown in the figure, each track T ₁ ,
The PCM signal is recorded in the A part of T _{2 .} . ., and the video signal is recorded in the B part. If the tracking pilot signal is of a so-called four-frequency pilot system, pilot signals of frequencies f ₁ , f ₂ , f ₃ , and f ₄ are recorded as shown in the figure. This pilot signal is used for tracking during playback, and each rotating head reproduces the crosstalk or side leads of these pilot signals from both adjacent tracks of the track currently being scanned, and is used as a tracking error signal. Ru. For example, when the rotary head 3a is scanning a portion of track _T1 , each frequency _f2 of the pilot signals on both sides is
The crosstalk or side leads of and _f4 are reproduced by the rotary head 3b, and the frequencies f2 and _f4 of each pilot signal are reproduced.
Since a tracking deviation can be detected by the reproduction level difference of _f4 , it can be used as an error signal for feedback to these tracking servos. In order to simplify the detection system of this error signal, between the above respective frequencies, |f ₁ −f ₂ |=|f ₃ −f ₄ |=F ₁ , |f ₂ −f ₃ |=|f ₁
The relationship −f ₄ |=F ₂ is given. For example, f ₁ =
103KHz, _f2 =119KHz, _f3 =165KHz, _f4 =149KHz
At this time, F ₁ = 16KHz and F ₂ = 46KHz.

When reproducing the magnetic tape 1 on which tracks have been formed as described above, a tracking servo is applied using the crosstalk or side lead of each of the pilot signals, and the two rotary heads 3 are
The video signal PCM signal is reproduced by a and 3b.
FIG. 3 shows the envelope of the signal reproduced by both rotary heads 3a and 3b, and as shown in this figure, the above 40°
In some parts, the video signal and PCM signal are played simultaneously. These signals also include crosstalk or side leads between the pilot signal of the scanning track and the pilot signals of adjacent tracks on both sides.

FIG. 4 is a block diagram showing the tracking servo system in the magnetic recording/reproducing apparatus of FIG. 1. The operation of the tracking servo system will be explained using FIG. 4. Head drum 2 shown in Figure 1
In synchronization with the rotation of the head drum 2, an oscillator (OSC) 21 generates oscillation signals of frequencies f ₁ , f ₂ , f ₃ , and f ₄ in a repeating order every half rotation corresponding to the above-mentioned 180°. On the other hand, each reproduction signal obtained by each rotary head 3a, 3b is guided via each head amplifier 11a, 11b to a switch 20 which is controlled by a switching pulse generated every half rotation of the head drum 2. , a continuous reproduced video signal and a time-compressed reproduced PCM signal. Next, the above-described reproduced pilot signal (pilot signal from the track being scanned and pilot signals due to crosstalk or side read from both adjacent tracks) is extracted from the reproduced video signal by a bandpass filter (BPF) 22. These pilot signals and each of the above oscillation signals are applied to the frequency converter (CONV) 23,
When the output of this CONV 23 is applied to two bandpass filters (BPF) 40 and 41 having center frequencies F ₁ and F ₂ , both BPFs
At the outputs of 40 and BPF 41, signals with components of center frequencies F ₁ and F ₂ as described above are generated, and when these two components are compared in level by differential amplifier 42, the signals of each rotating head 3a, 3b are determined. The amount of track deviation is detected. As this detection signal advances by one track, the above-mentioned center frequencies _F1 and _F2 obtained from the left and right tracks become opposite to each other. 43 output or the output as is. Tracking control is performed by feeding back the detection signal derived in this way to the head drum rotation control system or the capstan control system. The above detection signal is applied to the capstan motor 26. In this way, the tracking servo operates. When the tracking servo reaches a steady state, the rotary head starts scanning over a track on which a pilot signal of a frequency corresponding to the currently generated oscillation signal is recorded. For example, if the oscillation signal has a frequency f ₁ , the rotating head 3a at this time is
This means that part B of _T1 is being scanned. As mentioned above, when the tracking control reaches a steady state,
The output of the differential amplifier 42 is zero, that is, the crosstalk or side leads of the pilot signals from both adjacent tracks are equal, and the center of the gap of the rotary head is aligned with the center line of the track to perform head scanning.

Now, as described above, a certain amount of tracking servo is applied and a reproduced video signal can be obtained.
In magnetic recording and reproducing devices using the so-called inclined azimuth recording method, various combinations of track pit and rotating head widths are adopted. The timebases for each track may not match. In such cases, the television's playback screen will switch from the playback screen of one rotary head to the playback screen of the other rotary head, or in other words, there will be a phenomenon in which the image jumps left and right at the joint of the playback screen. .
Now, as an example of one combination of track pitch and rotating head width, consider setting the rotating head width to be larger than the track pitch (for example, 1.5 of the track pitch).
Consider the case where the At this time, when recording is performed by running the magnetic tape at the above-mentioned predetermined speed, as shown in FIG. By the head,
A portion of the track is overwritten and erased, a new track is written, and then this track is also partially overwritten and erased using one of the rotary heads. Below, some of the tracks written by each rotary head in this way are overwritten,
Tracks are formed one after another to have a predetermined track width. In this example, the track width is formed to be equal to the track pitch T _P.

Next, from the track formed in this way,
When reproducing data using the rotary head, as described above, the rotary head is subjected to a tracking servo so as to scan the center of the track. This aspect is the sixth
It is shown in the figure. As shown in FIG. 6, the solid line indicates the scanning position of the rotating head during reproduction, the broken line indicates the device position of the rotating head during recording (same as the scanning position shown in FIG. 5), and the dashed line indicates the scanning position of the rotating head during recording. The center of head scanning during reproduction is shown, and the two-dot chain line indicates the center of head scanning during recording. In the above-mentioned inclined azimuth recording method, since the azimuth angles are different between adjacent tracks (for example, ±θ as shown in FIG. 5), as shown in FIG. If the scanning positions of the images are different, the time base will be distorted. The horizontal synchronizing signal is schematically shown in FIG. 7. If the rotary head is scanning the center of the track as shown by the solid line in the figure, for example, looking at the horizontal synchronizing signal above,
As shown in FIG. 7, with respect to the correct time base (based on the time of recording), the reproduced signal of the rotary head 3a is deviated by -Δt, and the reproduced signal of the rotary head 3b is deviated by +Δt, respectively. Become.
Therefore, at the seam of the playback screen as described above, the time base jumps by 2Δt.
As another example, for example, the width of the rotating head 3a may be set to 1.5 times the track pitch T _P.
When the width of the rotating head 3b is set to 1.3 times the track pitch T _P and the speed of the magnetic tape 1 is set to twice the predetermined speed mentioned above during recording, the track width becomes 1.3 times the track pitch T P as shown in FIG. The head width becomes the same, and adjacent tracks have different widths. On the other hand, the track pitch is T _P ' as shown in Fig. 8, and in this case,
T _P ′=2T _P. When reproducing such a track, the distance to both adjacent tracks is different on the left and right as shown in Figure 8, so if the tracking servo is applied so that the left and right crosstalk or side leads are equal, the rotating head Since the trajectory is different from that at the time of recording, there is a drawback that the time base is distorted as described above.

[Summary of the invention]

This invention was made for the purpose of improving the drawbacks of the conventional ones as described above.
means for sequentially reproducing a pilot signal whose frequency varies in a repeating order from each track by means of a rotary head having an azimuth angle and a rotary head having a second azimuth angle, respectively; The pilot signal reproduced by the rotary head having the first azimuth angle and the pilot signal having the same frequency as the pilot signal are reproduced from the track recorded at the second azimuth angle by the rotary head having the second azimuth angle. means to compare the phases of both reproduced pilot signals of the same frequency to obtain a first output, and to reproduce from a track recorded at a second azimuth angle by a rotary head having a second azimuth angle. A pilot signal having the same frequency as that of the pilot signal is simultaneously reproduced from a track recorded at the first azimuth angle by a rotary head having the first azimuth angle, and both of these same frequencies are reproduced simultaneously. means for obtaining a second output by comparing the phases of the reproduced pilot signals; and means for calculating the difference between the first and second outputs as an error output and correcting the track deviation of the rotating head in accordance with the error output. The present invention provides a magnetic recording/reproducing apparatus which can easily and reliably correct track deviation by having a configuration including the following.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 9 is a block configuration diagram showing a reproducing system in a magnetic recording/reproducing apparatus which is an embodiment of the present invention, in which the same parts as in FIGS. 1 and 4 are indicated using the same symbols, and the details thereof are shown. Further explanation will be omitted.
As shown in the figure, 21 is an oscillator (OSC) that sequentially generates signals of each frequency f ₁ , f ₂ , f ₃ , f ₄ ,
This OSC 21 switches the oscillation frequency according to a command from a timing signal generation circuit 19 that operates based on a rotation detector 18 that detects the rotational phase of the head drum 2.
This is done every half revolution. Further, 22 is a bandpass filter (BPF) for extracting the reproduced pilot signal, and the pilot signal extracted by this BPF 22 and the oscillation signal of the OSC 21 are applied to a frequency converter (CONV) 23, and the oscillation signal is Track deviation detection as described above is performed using the difference frequency component between the frequency and the pilot signal frequency. An error signal corresponding to the amount of track deviation is applied to the amplifier 25 to control the rotation of the capstan motor 26, thereby controlling the feeding of the magnetic tape 1. The output of each rotating head 3a, 3b is applied to a switch 20 after being amplified by each head amplifier 11a, 11b. In this switcher 20, the timing signal generation circuit 1
A video signal and a PCM signal are each extracted at appropriate timings by the outputs of 9. The video signal is
The continuous reproduction signal is applied to the BPF 22 and subjected to the processing described above, while being led to the video signal processing circuit 27 and demodulated into a television signal. The PCM signal is processed by the PCM signal processing circuit 28
The signal is then guided through processing such as time expansion and demodulated into a continuous audio signal. Each head amplifier 11
The outputs of a and 11b are further subjected to the following processing in order to achieve the track deviation correction which is the object of the present invention. Each of the above head amplifiers 11a, 11
The output of b is each bandpass filter (BPF)
12a, 12b and each band filter (BPF) 3
Applied to 0a and 30b. Each of these BPF1
The center frequency of BPF 2a, 12b and 30a, 30b is a specific frequency among the pilot signal frequencies, for example, each BPF 12a, 12b has f ₁ , and each
It is assumed that the BPFs 30a and 30b have _f2 . Therefore, each BPF 12a, 12b extracts a pilot signal of frequency _f1 from the reproduced signal, and each BPF 30a, 30b extracts a pilot signal of frequency _f2 from the reproduced signal. Assuming that the magnetic tape 1 is under running control by the tracking servo and is reproducing signals by scanning approximately the center of each rotary head 3a, 3b track, the output signal of each BPF 12a, 12b and each BPF 30a are reproduced. , 30b are as shown in FIGS. 10A, B, F, and G, respectively.
However, since attention is focused only on the above-mentioned 40° portion, only the reproduced pilot signals from the tracks scanned by each rotary head 3a, 3b are taken into consideration. That is, although the frequency _f1 or _f2 of each pilot signal due to crosstalk occurs in other sections, it is ignored. Next, each BPF above
The outputs of 12a, 12b and 30a, 30b are applied to the next phase comparison circuits 13, 31, and phase errors between the two occur, for example, as shown in FIG. 10C and H. Here, if the scanning position of each rotary head 3a, 3b does not change at all from the time of recording, since the pilot signal is simultaneously recorded in the above 40° section by each rotary head 3a, 3b, it will not change even during playback. The pilot signals reproduced from both rotating heads 3a and 3b have the same timing. Therefore, the output of each phase comparator circuit 13 and 31 becomes zero. However, if each rotary head 3a, 3b reproduces a signal in a state that is shifted from the recording strength, as shown in FIGS. 6, 7, and 8, for example, the reproduced pilot signal of the rotary head 3a and the rotation A phase difference occurs in the reproduced pilot signal of the head 3b.
An illustration of this aspect is shown in the enlarged view of FIG. For example, in the state shown in FIG. 7, as shown in FIG. 11A, for the output of the BPF 12a (solid line),
The output of the BPF 12b (broken line) will lead in phase. In addition, as shown in Figure 11B, BPF30
The output of the BPF 30b (broken line) is delayed in phase with respect to the a output (solid line). Like this,
When each rotary head 3a, 3b scans a different position from that during recording, a phase difference occurs between the pilot signals simultaneously reproduced by both rotary heads 3a, 3b during reproduction, and the phase comparator circuits 13 and 31 An error voltage is generated according to the scanning deviation. This error voltage occurs only in the 40° portion, and moreover, it occurs once every four times when each rotary head 3a, 3b successively scans the track. In other words, this occurs once every two rotations of the head drum 2.
In this way, since the error voltage is not generated continuously, the timing signal generating circuit 19 generates the 10D and I signals once every two revolutions of the head drum 2.
If a sample pulse for sampling is generated at the timing shown in FIG. 9 and applied to each sample hold circuit (S/H) 14 and 32 shown in FIG. Error outputs E and -E as shown in J are obtained.

Now, in the above explanation, each rotating head 3a,
3b described the process of generating an error voltage due to the time base deviation that occurs when scanning a position different from that during recording during playback, but this error voltage has another component due to the expansion and contraction of the magnetic tape may be mixed in. That is, if the elongation of the magnetic tape 1 during recording differs from the elongation of the magnetic tape 1 during reproduction, so-called skew distortion occurs, and in this case as well, the time base is deviated.
However, unlike the example described above, the direction of the time base deviation due to this skew distortion is not reversed for each rotary head 3a, 3b, but is the same for both rotary heads 3a, 3b as is well known. It becomes disorienting. For example, if the elongation during playback of the magnetic tape 1 is smaller than the elongation during recording, then during playback, the output of BPF 12a in FIG. 9 lags behind the output of BPF 12b, and the output of BPF 30a also
The phase lags behind the output of BPF30b. Therefore, if there is a time base deviation due to skew distortion, the above-mentioned error voltage will be affected by the false pixel component e mixed in the same direction as shown in FIGS. 10C and 10H. Error voltages as shown by the broken lines in Figures C and H are obtained. Therefore, a false error component e also appears in each S/H 14 and 32 shown in FIG. 9, resulting in error voltages as shown by broken lines in FIGS. 10E and J. When the error voltages shown in FIG. 10 E and J are then applied to the subtracter 33 shown in FIG. Component e is removed, leaving only the error voltage corresponding to the track deviation. Note that by performing subtraction by the subtracter 33 as described above, the desired error voltage increases.
There is a side benefit of increased sensitivity. The error voltage is guided to the filter 15 shown in FIG. 9 for smoothing, and the smoothed output is applied to one input of the differential amplifier 42 shown in FIG. As a result, an offset voltage is applied to the differential amplifier 42, and the balanced state of the outputs of the BPFs 40 and 41 is shifted. In other words, each rotary head 3a,
3b scans. Therefore, if the error voltage is fed back so that the shift in the equilibrium state exactly matches the scanning position during recording, that is, the output of the subtracter 33 becomes zero, the reproduction system shown in FIG. By configuring , the above time base deviation can be corrected. In this manner, each rotary head 3a, 3b can be scanned at the position shown by the broken line in FIG. 7 even during reproduction, and reproduction can be performed on the same time base as during recording. Therefore, signal jumps at the joints of the reproduced screen, which occur due to track deviation, do not occur. Here, the skew distortion was corrected by combining the frequencies f ₁ and f ₂ of each pilot signal, but which of the frequencies f ₁ and f ₄ , f ₂ and f ₃ , and f ₃ and f ₄ of each pilot signal You can also use a combination. To explain this collectively in another way, first, for example, a pilot signal reproduced by the first rotary head from a track recorded at one azimuth angle, and a pilot signal adjacent to the track recorded at this one azimuth angle. The above-mentioned 40° of the track
A reproducing pilot signal having the same frequency as the above reproducing pilot signal is simultaneously obtained from the end of the second rotary head, the phases of the two are compared, the output is sampled and held, and then the azimuth angle of the other is The pilot signal reproduced by the second rotary head from the track recorded at this other azimuth angle and from the end of the above-mentioned 40° section of the track adjacent to the track recorded at the other azimuth angle. A reproducing pilot signal of the same frequency as the above-mentioned reproducing pilot signal is obtained simultaneously by the rotary head 1, the phases of the two are compared, the output is sampled and held, and this sampled and held output is subtracted from the sampled and held output. It will be a good thing if you do.

In the above embodiment, the PCM audio is recorded at the front end of each track, and the video signal is recorded at the rear thereof, but the order of these signals may be reversed. , the same effect as the above embodiment is achieved.

Further, in the above embodiment, the pilot signal has four frequencies, but it is not necessarily limited to four.

〔Effect of the invention〕

As explained above, in a magnetic recording and reproducing apparatus, during reproduction, the present invention generates a pilot signal whose frequency changes in a repetitive order by a rotary head having a first azimuth angle and a rotary head having a second azimuth angle. means for sequentially reproducing a track from a track; a pilot signal reproduced by a rotary head having a first azimuth angle from a track recorded at a first azimuth angle; and a second pilot signal having the same frequency as the pilot signal. means for simultaneously reproducing tracks recorded at an azimuth angle by a rotary head having a second azimuth angle and comparing the phases of both reproduction pilot signals having the same frequency to obtain a first output; A pilot signal reproduced by a rotary head having a second azimuth angle from a track recorded at an azimuth angle of means for simultaneously reproducing by a rotary head having an azimuth angle of Since it has a configuration that includes an output and a means for correcting the track deviation of the rotary head according to this error output, it is possible to reliably correct the track deviation with an extremely simple configuration, and it is possible to correct the track deviation caused by this track deviation. This has the excellent effect of suppressing signal jumps at the joints of the playback screen.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the head drum and the manner in which the magnetic tape is wound in a conventional magnetic recording/reproducing apparatus, FIG. 2 is a diagram showing a track pattern on the magnetic tape in the magnetic recording/reproducing apparatus shown in FIG. 1, and FIG. 1 is a diagram showing the envelope of a signal reproduced from each rotary head in the magnetic recording and reproducing apparatus of FIG. 1, FIG. 4 is a block configuration diagram showing a tracking servo system in the magnetic recording and reproducing apparatus of FIG. FIG. 5 is a schematic diagram of the magnetic recording/reproducing apparatus shown in FIG. 4 when a track is formed by a rotating head wider than the track pitch, and FIG.
FIG. 7 shows the scanning position of the rotary head during recording and the scanning position of the rotary head during reproduction in the magnetic recording and reproducing apparatus shown in FIG. A schematic diagram showing the time base deviation between the scanning position and the playback signal,
FIG. 8 shows the magnetic recording/reproducing apparatus shown in FIG.
A diagram showing a track pattern on a magnetic tape when recording is performed at double the magnetic tape speed using rotating heads with different head widths. FIG. 9 shows a reproducing system in a magnetic recording and reproducing apparatus which is an embodiment of the present invention. FIG. 10 is a diagram of the block configuration, and FIG. 10 is a signal waveform diagram of each part in the magnetic recording/reproducing apparatus of FIG. 9. FIG. 11 is an enlarged diagram showing the phase relationship of the reproduction pilot signal in the magnetic recording/reproducing apparatus of FIG. 9. . In the figure, 1...magnetic tape, 2...head drum, 3a, 3b...rotating head, 11a, 1
1b...Head amplifier, 12a, 12b, 22,
30a, 30b, 40, 41... bandpass filter (BPF), 13, 31... phase comparison circuit, 14,
32...Sample hold circuit (S/H), 15
... Filter, 18 ... Rotation detector, 19 ... Timing signal generation circuit, 20 ... Switcher, 2
1... Oscillator (OSC), 23... Frequency converter (CONV), 25... Amplifier, 26... Capstan motor, 27... Video signal processing circuit, 28...
...PCM signal processing circuit, 33...subtractor, 42...
. . . differential amplifier, 43 . . . inverting amplifier, 44 . . . switch. In addition, in each figure, the same reference numerals are the same,
or a corresponding portion.

Claims (1)

[Claims] 1 a rotating head having a first azimuth angle and a second
Parallel inclined tracks are sequentially formed on the magnetic tape by a rotating head having an azimuth angle of The rotary head having the first azimuth angle and the rotary head having the second azimuth angle are simultaneously brought into contact with the magnetic tape, and one end of the track is provided with a rotary head of the magnetic tape. In a magnetic recording and reproducing apparatus configured so that pilot signals recorded on one track before or after the other are simultaneously recorded, during reproduction, a rotary head having the first azimuth angle and a rotating head having the second azimuth angle are used. means for sequentially reproducing from each track a pilot signal whose frequency varies in said repetition order by means of a rotary head, and reproducing by said rotary head having said first azimuth angle from a track recorded at a first azimuth angle; A pilot signal and a pilot signal having the same frequency as the pilot signal are simultaneously reproduced from a track recorded at a second azimuth angle by a rotary head having the second azimuth angle, and both reproductions of these same frequencies are performed. means for comparing the phases of pilot signals to obtain a first output; a pilot signal reproduced from a track recorded at the second azimuth angle by the rotary head having the second azimuth angle; Pilot signals of the same frequency are simultaneously reproduced from tracks recorded at the first azimuth angle by a rotary head having the first azimuth angle, and the phases of these two reproduced pilot signals of the same frequency are compared. It is characterized by comprising means for obtaining a second output, and means for calculating the difference between the first and second outputs as an error output, and correcting a track deviation of the rotary head in accordance with this error output. magnetic recording and reproducing device.