JPS6321975B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a pilot signal recording and reproducing method,
At least four types of predetermined frequency signals are cyclically switched for each track as pilot signals and recorded sequentially, and during reproduction, two types of pilot signals reproduced from tracks on both sides of the track to be scanned are selectively reproduced. Helical scan type magnetic recording and reproducing apparatuses and disk reproducing apparatuses that are capable of recording and reproducing pilot signals for obtaining track deviation information in a relatively narrow band, and that are capable of controlling the displacement of the head in particular by following track bends, etc. It is an object of the present invention to provide a pilot signal recording and reproducing method suitable for application to, etc.

In recent years, household helical scan rotary head magnetic recording and reproducing devices (hereinafter referred to as ``home VTR'') have become popular.
In conjunction with improvements in magnetic tape and increased sensitivity of rotating heads, recording and reproducing densities have been further increased, and tape speeds, track pitches, etc. have been changed to, for example, those that can be recorded and reproduced for two hours in the past. Approximately 1/
Home VTRs with long recording and playback times of 6 hours have now been commercialized.
However, in home VTRs, where the tape running system is simplified to reduce costs, the high density described above is
It becomes difficult to follow the bending of the video track and stably maintain the required tracking accuracy, especially when playing back a magnetic tape recorded on another home VTR on another home VTR (so-called compatible playback). It is difficult to maintain stable accuracy, and currently high image quality cannot be obtained.

Therefore, as a method to solve the above-mentioned tracking problem associated with high-density recording and playback, and also to eliminate noise bars during special playback (trick play) such as slow-motion playback, still playback, and fast-motion playback, we have developed a rotating head. In recent years, home VTRs have been actively developed that are equipped with a head moving mechanism that displaces the rotary head on a plane perpendicular to its rotating surface and displaces the rotary head in a direction perpendicular to the longitudinal direction of the track (that is, in the width direction of the track). ing.

A platform equipped with such a head moving mechanism
In VTR, it follows the curve of the track,
Alternatively, in order to make the track follow the head scanning locus during special playback, which is performed at a tape running speed different from that during recording, information on the relative shift between the track to be scanned and the rotating head currently scanning the magnetic tape (track shift It has a tracking servo circuit that detects the track deviation information) and generates a tracking error signal based on the tracking error signal to correct the tracking deviation of the rotary head.Accurately detecting the above tracking deviation information is the key to correcting the tracking deviation. It is extremely important for

Conventionally, as a method for detecting the track deviation information, four types of pilot signals whose frequencies are switched for each track recording unit are sent to each track so that adjacent tracks are recorded at different frequencies. There is a system that records continuously on a track, and during playback, discriminates the frequency of the playback pilot signal and detects track deviation information from the playback level. requires a circuit,
A wide bandwidth was required.

On the other hand, during playback, the rotating head is vibrated in the width direction of the track at approximately 480 Hz, and track deviation is detected from fluctuations in the playback FM level of information signals recorded in the form of frequency modulated wave signals (FM signals) on the track. There is also a conventional method, but this conventional method has the disadvantage that the influence of fluctuations in the reproduced FM level may appear in the reproduced image, and that track deviation information cannot be obtained accurately for track deviations of one track pitch or more. had.

The present invention eliminates the above-mentioned drawbacks,
Each embodiment will be described below with reference to the drawings.

FIG. 1 shows a block system diagram of an embodiment of a recording system according to the present invention. In the figure, a composite video signal that enters the input terminal 1 is branched into two, one of which is supplied to the recording signal processing circuit 2 and converted into an FM signal of a predetermined frequency band, and the other is supplied to the horizontal synchronization signal separation circuit 3. Ru. The horizontal synchronization signal extracted by the horizontal synchronization signal separation circuit 3 is frequency-divided by 1/4 by a 1/4 frequency divider 4 and then supplied to a phase comparator 5 .

The output error voltage of the phase comparator 5 passes through a loop filter 6 to variably control the output oscillation frequency of a voltage controlled oscillator (VCO) 7, and the output oscillation frequency of this VCO 7 is divided by a counter 8 to obtain the horizontal scanning frequency _fH. The frequency is 1/4 times as high as 1/ _4fH , and is supplied to the phase comparator 5, where the phase is compared with the signal of frequency 1/ _4fH from the 1/4 frequency divider 4. That is, the phase comparator 5, loop filter 6, VCO 7, and counter 8 each constitute a well-known phase locked loop (PLL), and the output oscillation frequency of the VCO 7 is the frequency division ratio of the counter 8 divided by 1/M. Then, it becomes f _H /4·M and becomes a signal synchronized with the output signal of the 1/4 frequency divider 4.

Here, the frequency division ratio 1/M of the counter 8 is configured to be varied in accordance with a control signal applied from the control circuit 10 through the line 11.
0 switches and outputs a control signal of a different value each time the rotary head 13 forms one track on the magnetic tape 14 in response to a drum pulse from the input terminal 9.

As a result, for example, the frequency division ratio of the counter 8 is 1/25, 1/34, 1/35, 1/25, 1/34, 1/35,
Four types of frequency division ratios are sequentially and cyclically switched such as /26, 1/25, and so on. As a result, the output oscillation frequency of the VCO 7 is 25/4f _H (=f ₁ ), 34/4f _H (=f ₃ ), 35/4f _H (=f _{4 )} for each track recording unit.
), 26/4f _H (=f ₂ ). this
The output oscillation frequency of the VCO 7 is supplied to the mixing circuit 12, where it is frequency division multiplexed with the FM video signal from the recording signal processing circuit 2, and then sent to the rotary head 13.
The data is recorded on the magnetic tape 14 by.

FIG. 2 shows a track pattern on the magnetic tape 14 recorded by the rotating head 13, and the tracks inclined with respect to the longitudinal direction of the magnetic tape 14 are t ₁ , t ₂ , t ₃ , t ₄ , t ₅ , They are formed sequentially in the order of t ₆ ,... Here, tracks t ₁ , t ₂ , t ₃ , t ₄ , t ₅ , t ₆
In addition to the FM composite video signal, the frequencies f ₁ , f ₃ ,
Pilot signals of f ₄ , f ₂ , f ₁ and f ₃ are recorded respectively.

In this embodiment, the first frequency group of an arbitrary number i that satisfies the formula f _ai = (2N _i −1) f _x /2 (1) is used as a pilot signal.
From f _a1 ~ f _ai , f ₁ of frequencies that are more than 2fx apart from each other,
Select f ₄ and select an arbitrary number j of second frequency groups that satisfy the following formula: f _bj = (2N _j −1) f _y /2 (where f _x ≠ f _y ) (2)
From f _b1 to f _bj , select frequencies f ₂ and f ₃ that have a difference of 2fx or less from the frequencies f ₁ and f ₄ , and combine the frequencies of the first frequency group and the frequencies of the second frequency group. They were recorded in the order of f ₁ , f ₃ , f ₄ , f ₂ by alternating and switching every track recording unit so that extremely close frequencies were recorded on adjacent tracks ( (The order may be f ₂ , f ₄ , f ₃ , f ₁ ). In addition
In formulas (1) and (2), N _i and N _j are natural numbers, and f ₁ to f ₄ are, for example, It is. However, the pilot signals f ₁ to _{f 4} are in a lower band than the FM video signal band, and f _x = f _H /2 and f _y = f _H.

By the way, as pilot signals, equations (1) and (2)
In the same way as above, two sets of frequencies are calculated from each frequency group that satisfies the following expressions: f _ai ′=N _i・f _x (4) f _bj ′=N _j・f _y (5) Frequencies f ₁ ', f ₄ ', f ₂ ', f ₃ ' may be used as pilot signals instead of f ₁ , f ₄ , f ₂ , f ₃ .
Here, f ₁ ′ to f ₄ ′ are, for example It is. However, in formulas (4) and (5), f _x = f _H /2, f _y = 3/
4 f _H.

Next, the operation of the reproduction system according to the present invention will be explained. FIG. 3 shows a block system diagram of a first embodiment of the regeneration system according to the present invention. In the figure, a signal reproduced by a rotary head 13 from a magnetic tape 14 having a track pattern as shown in FIG. The signal is then subjected to predetermined signal processing and reproduced into the original composite video signal, and the other signal is applied to a charge coupled device (CCD) 22, which is an example of a variable delay element.

From the reproduced composite video signal taken out from the reproduced signal processing circuit 21, only the horizontal synchronizing signal is separated and extracted by the horizontal synchronizing signal separating circuit 23, and then sent to the phase comparator 24.
is supplied to This phase comparator 24 is connected to a PLL along with a loop filter 25, a VCO 26, and a counter 27.
It consists of The frequency division ratio of the counter 27 is set to 1 of the rotary head 13 by a control signal from the control circuit 28.
It is alternately switched between 1/455 and 1/910 for each track reproduction unit. Therefore, the output oscillation frequency of VCO26 is
Alternately for each track playback unit of the rotary head 13
Switchable between 455f _H and 910f _H.

The output oscillation frequency 455f _H or 910f _H of the VCO 26 is divided by 1/2 by the 1/2 frequency divider 29 and then applied to the CCD 22 as a clock pulse. CCD22
consists of 455 stages, and when the clock pulse frequency is 455/2f _H , the reproduced signal is delayed by 2H (H is the horizontal scanning period);
When 910/2f _H , the reproduced signal is delayed by H and output. The output delayed reproduction signal of the CCD 22 is sent to the adder 30.
where it is added to the undelayed reproduced signal from preamplifier 20. This results in
The CCD 22 and the adder 30 constitute a so-called comb filter consisting of a delay circuit with a delay time T and an adder circuit, and its frequency characteristics are shown in FIG.
When the delay time T of 2 is 2H, it becomes as shown by a solid line, and when the delay time T is H, it becomes as shown by a broken line.

Therefore, in the output signal of the adder 30, CCD2
Pilot signals f ₂ and f ₃ may be included during one track playback period when the delay time T of 2 is 2H.
Pilot signals f ₁ and f ₄ are blocked and are not included. Also, during one track reproducing period when the delay time T of the CCD 22 is H, the pilot signal f ₁ ,
f ₄ is taken out by adder 30, but pilot signals f ₂ and f ₃ are blocked.

The output signal of the adder 30 is passed through a bandpass filter 31 having a characteristic of passing the pilot signals of frequencies f ₁ and f ₂ as _shown by the curve in FIG _. and a bandpass filter 32 having a characteristic of passing the pilot signal. The output signal of the band filter 31 is supplied to the fixed terminal 33a of the changeover switch 33 and the fixed terminal 34b of the changeover switch 34 through a detection circuit (not shown), respectively.
The output signal passes through a detection circuit (not shown) to the fixed terminal 33b of the changeover switch 33 and the changeover switch 3.
4 fixed terminals 34a, respectively. The changeover switches 33 and 34 are switched in conjunction with each other.

In addition, the changeover switches 33 and 34 are connected to the control circuit 28.
The rotating head 13 reproduces the track on which the pilot signals _f1 and _f3 are recorded. During the period, the fixed terminals 33b and 34a are connected to the fixed terminals 33a and 34a, respectively, and during the period of reproducing the tracks on which the pilot signals _f2 and _f4 are recorded, the fixed terminals 33b and 34a are connected to the fixed terminals 33a and 34a, respectively.
4b side, respectively.

By the way, during reproduction, during the period when the rotary head 13 is reproducing the track on which the pilot signal f ₁ is recorded, the pilot signals f ₂ and f ₃ from the adjacent tracks are generated as crosstalk, respectively, as can be seen from FIG. will be played. During this reproduction period, the frequency division ratio of the counter 27 is set to 1/455, and the changeover switches 33 and 34 are connected to fixed terminals 33a and 34a, respectively. As a result, during this reproduction period, the pilot signal f ₁ from the track to be reproduced is blocked by the comb filter consisting of the CCD 22 and the adder 30.
In addition, pilot signals f ₂ and f ₃ reproduced as crosstalk are supplied to band filters 31 and 32. As a result, the pilot signal f ₂ regenerated as crosstalk is extracted from the bandpass filter 31 and passed through the changeover switch 33 to the differential amplifier 35.
is applied to the positive phase input terminal of On the other hand, the pilot signal _f3 reproduced as crosstalk is taken out from the band filter 32, and is further output to the selector switch 3.
4 and is applied to the anti-phase input terminal of the differential amplifier 35.

If the rotary head 13 now moves upward in FIG. 2, the crosstalk level of the pilot signal _f3 will be relatively high compared to the crosstalk level of the pilot signal _f2 . The output track deviation detection voltage of the differential amplifier 35 is lower than when there is no track deviation. Conversely, if the rotary head 13 moves downward in FIG. 2, the crosstalk level of the pilot signal _f3 will be relatively low compared to the crosstalk level of the pilot signal _f2 , so the difference The output track deviation detection voltage of the dynamic amplifier 35 is higher than when there is no track deviation.

Next, the rotary head 13 receives the pilot signal _f2 from FM.
During the playback period in which the track recorded together with the video signal is played back, the counter 27 is set at a frequency division ratio of 1/910, and the playback pilot signal _f2 from the track to be played is blocked by the comb filter, and , pilot signals f ₁ and f _{4 reproduced as crosstalk from adjacent tracks are waved, and then a pilot signal f 1 is} waved from a band filter 31 and a pilot signal f ₄ is waved from a band filter 32, respectively. Also, during the reproduction period of the recorded track of the pilot signal _f2 , the changeover switches 33 and 34 are switched to the fixed terminals 33b and 34b.
Pilot signal reproduced as crosstalk and extracted from band filters 31 and 32
f ₁ and f ₄ are applied to the negative phase and positive phase input terminals of the differential amplifier 35.

Therefore, in this case, if the rotary head 13 is shifted upward in FIG. 2 and reproduction is performed, the crosstalk level of the pilot signal _f1 will be relatively higher than the crosstalk level of the pilot signal _f4 . Therefore, the differential amplifier 35 output terminal 36
The track deviation detection voltage output to is lower than when there is no track deviation. Conversely, when the rotary head 13 is shifted downward in FIG. 2 and reproduction is performed, the track shift detection voltage becomes higher than when there is no track shift, contrary to the above.

Next, in the example of FIG. 2, the previously recorded track of the pilot signal _f4 is reproduced by the rotary head 13, but during this reproduction period, the frequency division ratio of the counter 27 is switched to 1/455, and the changeover switch is switched to 1/455. 33 and 34 are also switched and connected to the fixed terminals 33b and 34b. As a result, as is clear from the above explanation, the pilot signals f ₂ ,
f ₃ is applied to the negative phase and positive phase input terminals of the differential amplifier 35. Therefore, the track deviation detection voltage is low when the track deviation is upward in FIG. 2, and high when it is downward.

Similarly, during the reproduction period of the recorded track of the pilot signal _f3 , the frequency division ratio of the counter 27 is (1/910).
At the same time, the changeover switches 33 and 34 are also connected to the fixed terminals 33a and 34a. As a result, the pilot signals f ₄ and f ₁ reproduced as crosstalk from the adjacent tracks by the bandpass filters 31 and 32 are applied to the positive phase and negative phase input terminals of the differential amplifier 35. Therefore, the track deviation detection voltage is low when the track deviation occurs in the upward direction in FIG. 2, and becomes high when the track deviation occurs in the downward direction.

In this way, the pilot signals reproduced as crosstalk from the adjacent tracks on both sides of the track to be reproduced are extracted from the band filters 31 and 32, and the rotary head 13 causes the track to shift upward in FIG. The track deviation detection voltage is output from the output terminal 36 and has a low value depending on the amount of track deviation when the track is being played back, and a high value depending on the amount of track deviation when playing with a downward track deviation. It is output from Therefore, it is clear that the track deviation can be corrected based on this track deviation detection voltage.

Note that the signals that control the changeover switches 33 and 34 are generated by dividing the frequency of the drum pulse by 1/2 (not shown), so at the start of playback, the changeover switches 33 and
34, the rotary head 13 receives pilot signals f ₁ and f ₃
During the period when playing the recorded track,
They are connected to the fixed terminals 33a and 34a, respectively, and may be connected to the fixed terminals 33b and 34b, respectively, during the period of reproducing the track on which the pilot signals _f2 and _f4 are recorded. However, in the case of this sequence, if the rotary head 13 shifts upward even slightly, the output of the differential amplifier 35 becomes low, and the output is controlled to shift further upward, resulting in 2
The sequence shifts up by the track pitch and becomes stable, becoming the same as the above sequence. Furthermore, if there is even a slight shift downward, the output of the differential amplifier 35 becomes high, and control is performed to shift it further downward, eventually shifting downward by two track pitches, resulting in the same sequence as described above and stabilization.

FIG. 5 shows a block system diagram of a second embodiment of the regeneration system according to the present invention. In this embodiment, the magnetic tape 1
On the inclined track above 4', instead of _the pilot signals f ₁ to _{f 4} shown in FIG. The same parts as in FIG. 3 are given the same reference numerals and their explanations will be omitted.

In Fig. 5, counter 3 that constitutes the PLL
8 is a 1/4 frequency divider with a frequency division ratio of 1/1365 during the period in which the rotary head 13 reproduces the recorded track of the pilot signal f ₂ ' or f ₃ ' according to the output control signal of the control circuit 37. The delay time of the CCD 22 to which the clock pulse is applied from 43 is set to 4/3H, and on the other hand, during the reproduction period of the recorded track of the pilot signal f ₁ ' or f ₄ ', the frequency division ratio is set to 1/910 and the delay time of the CCD 22 is set to 4/3H. It will be 2H. The output delay signal of CCD22 is output by adder 4
0, it is added to the reproduced signal that has been inverted and amplified by the inverting amplifier 39. That is, the reproduced signal from the preamplifier 20 is subtracted from the reproduced signal delayed by the CCD 22. The CCD 22, the inverting amplifier 39, and the adder 40 each constitute a comb filter, and when the delay time of the CCD 22 is 2H, the frequency characteristics shown by the solid line in FIG. The frequency characteristics indicated by broken lines are shown in a.

Therefore, the rotary head 13 receives the pilot signal.
The period for playing back the recorded track of f ₁ ′ or f ₄ ′ is as follows:
With the above comb filter, f ₂ ′ and
f ₃ ′ is waved, and f ₁ ′ and f ₄ ′ are blocked. On the other hand, during the reproduction period of the recorded track of the pilot signal f ₂ ′ or f ₃ ′, f ₁ ′ and f ₄ ′ are waved, and f ₂ ′,
f ₃ ′ is blocked. The signals extracted from adder 40 are supplied to bandpass filters 41 and 42, respectively.

The bandpass filter 41 has frequency characteristics that pass the frequencies f ₁ ' and f ₂ ' as shown by _the curve in FIG. It has frequency characteristics that allow the ₄ ' frequency to pass through. Therefore, the band filters 41 and 42 are supplied with pilot signals reproduced as crosstalk from the tracks on both sides of the reproduced track of the rotary head 13 extracted by the above-mentioned comb filter, and each of these is frequency-selected. will be output.

The output signals of the bandpass filters 41 and 42 are supplied to a differential amplifier 35 via changeover switches 33 and 34, and a track deviation detection voltage is outputted from an output terminal 36 in the same manner as in FIG.

Note that if the pilot signal frequency is selected to have a certain relationship with the composite video signal to be superimposed and recorded, a variable delay element such as a CCD or bucket brigade device (BBD) will cause wow, flutter, etc. to occur in the reproduced pilot signal. The pilot signal can be easily distinguished even if it contains a variation. Furthermore, if time axis fluctuations such as wow and flutter can be ignored, there is no need to select the pilot signal frequency to have a constant frequency relationship with the composite video signal.
Instead of using a variable delay element such as the above, it is also possible to switch and use an element with a fixed delay time such as an inexpensive glass delay element.

As mentioned above, the pilot signal recording/reproducing method according to the present invention is f _ai = K _i ·f _x (where K _i is N _i −1/2 or N _i where N _i is any i natural number. (where f _x is a predetermined frequency) From the first frequency group consisting of i frequencies that satisfy the formula,
and the second frequency, respectively, and f _bj = K _j・f _y (where, k _j is N _j −(1/2) or N _j when any j natural numbers are N _j From the second frequency group consisting of j frequencies satisfying the formula f _y ≠ fx), a third frequency whose difference from the first frequency is 2fx or less and the second frequency The first to fourth frequencies are frequency-division multiplexed to the information signal as pilot signals, and the information signal is sequentially divided into one track unit at a time on the recording medium. , 4th, 2nd
and the third order (or the reverse order) to record the entire track, and during playback, the tracks on both sides of the track to be played that are included as crosstalk in the playback signal are recorded. The frequency of the pilot signals having different frequencies is selected by a variable filter circuit including a delay circuit whose delay time can be changed every track reproduction period, and the track deviation information is obtained from the level difference between these two pilot signals. Since the third, second, and fourth frequencies are very close to each other, the frequency bandwidth required for discrimination and separation is just over two frequencies, and the four types of pilot signals can be separated in a relatively narrow band. Recording and playback possible, frequency f _x , f _y
If is set to a value related to the horizontal scanning frequency, the pilot signal can be easily distinguished using a variable filter circuit even if fluctuations such as wow and flutter are included, and the pilot signal can be set to a value related to the recording frequency band of the information signal. Since the frequency is selected to be lower than that of the azimuth recording/reproducing method, the pilot signal of the adjacent track can be efficiently reproduced as crosstalk even in an azimuth recording/reproducing type magnetic recording/reproducing apparatus.

[Brief explanation of the drawing]

FIG. 1 is a block system diagram showing an embodiment of a recording system according to the present invention, FIG. 2 is a diagram showing an example of a track pattern on a magnetic tape recorded and reproduced according to the present invention, and FIG. 3 is a diagram showing an example of a track pattern according to the present invention. The first method of reproduction system
4a and 4b are diagrams showing the frequency characteristics of each part of FIG. 3, respectively. FIG. 5 is a block system diagram showing a second embodiment of the reproduction system of the present invention. 6a and 6b are diagrams showing the frequency characteristics of each part in FIG. 5, respectively. 1...Composite video signal input terminal, 3, 23...Horizontal synchronization signal separation circuit, 8, 27, 38...Counter, 9
...Drum pulse input terminal, 14...Magnetic tape, 2
2...Charge coupled device (CCD),
30, 40...Adder, 31, 32, 41, 42...
Band filter, 33, 34...Switch switch, 35
...Differential amplifier, 39...Inverting amplifier.

Claims (1)

[Claims] 1 f _ai = K _i fx (where K _i is N _i -(1/2) or N _i when any i natural numbers are N _i , and fx is a predetermined frequency ) from the first frequency group consisting of i consecutive frequencies, select the first frequency and the second frequency that are separated from each other by 2fx or more, and f _bj = K _j・f _y (however, , K _j is N _j - (1/2) or N _j where N _j is any j natural number, and the second frequency group is made up of j frequencies that satisfy the formula f _y ≠ fx) , a third frequency whose difference from the first frequency is 2fx or less and a fourth frequency whose difference from the second frequency is 2fx or less are selected, respectively. The fourth frequency is used as a pilot signal and is frequency division multiplexed onto the information signal to sequentially transmit the first, fourth, and second frequencies on the recording medium in units of one track.
and the third order (or the reverse order) to record the entire track, and during playback, the tracks on both sides of the track to be played that are included as crosstalk in the playback signal are recorded. The frequency of the pilot signals having different frequencies is selected by a variable filter circuit including a delay circuit that can change the delay time for each track reproduction period, and track deviation information is obtained from the level difference between these two pilot signals. A pilot signal recording and reproducing method. 2. The information signal shall be a composite video signal, and the frequency
2. The pilot signal recording and reproducing method according to claim 1, wherein fx and _fY are values related to a horizontal scanning frequency. 3. The pilot signal recording and reproducing method according to claim 1 or 2, wherein the first to fourth frequencies are selected to be frequencies lower than the information signal recording frequency band.