JPS6216446B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a tracking device in a magnetic reproducing device, in which a pilot signal of the same frequency is intermittently magnetically recorded on each track at predetermined intervals, and the tracks on both sides of the track are In this case, pilot signals of different frequencies are magnetically recorded, and pilot signals are detected from a recording medium formed by magnetic recording so that pilot signal recording sections are not adjacent between adjacent tracks. An object of the present invention is to provide a tracking device that can accurately follow and scan a recording track.

2. Description of the Related Art A helical scan type magnetic recording/reproducing apparatus is conventionally known in which a video signal is recorded on a magnetic tape by a rotating video head by forming a video track inclined with respect to the longitudinal direction of the tape, and is then reproduced. In such magnetic recording and reproducing apparatuses, various tracking devices have been proposed for accurately scanning a rotating video head over a video track during playback. Ta.

A tracking device that wobbles a rotating video head scans a video track while wobbling (meandering) the rotating video head when reproducing a magnetic recording medium in which a guard band is formed between adjacent video tracks, and adjusts the wobbling frequency. The video track to be scanned is detected using a control signal obtained by utilizing the fluctuation of the amplitude of the video track reproduction signal in accordance with the change in the amplitude of the video track reproduction signal, and the video track is accurately scanned. However, when this conventional tracking device reproduces a magnetic recording medium in which a video track is formed without a guard band or with an extremely small guard band width, each time the rotating video head wobbles, the recorded data on the adjacent track is tracked. The drawback was that the signal was reproduced as crosstalk, resulting in a significant deterioration of the reproduced image quality.

In addition, conventional tracking devices that use pilot signals sequentially and cyclically switch between three or more types of pilot signals every track period to continuously record one type of pilot signal along with a video signal on one video track. During playback, the tracking deviation direction is detected based on whether the beat frequency between the playback pilot signal from the track being played back and the pilot signal obtained as crosstalk from the track being played back and the adjacent track is higher or lower. The rotating video head is caused to accurately follow and scan the video track to be scanned. According to a tracking device using this pilot signal, accurate tracking operation can be performed even on a magnetic tape on which a video track is formed without a guard band or with an extremely small guard band width.

However, in conventional tracking devices that use this pilot signal, it is necessary to maintain the pilot signal frequencies in a certain relationship in order to use the beats of each other's frequencies, and because all three or more types of pilot signals are used, A disadvantage is that a large number of oscillators are required, resulting in a complicated circuit configuration.

The present invention eliminates the above-mentioned drawbacks, and one embodiment thereof will be described below with reference to FIGS. 1 to 8.

FIG. 1 shows a block system diagram of an example of a recording system of a recording medium that is tracked and reproduced by the apparatus of the present invention. In the figure, 1 and 2 are oscillators that oscillate and output pilot signals of frequencies f ₁ and f ₂ , respectively.
Supply to 2V switching circuit 3. The pilot signal frequencies f ₁ and f ₂ are selected to be frequency division multiplexed with the video signal to be recorded. For example, a color video signal is separated into a luminance signal and a carrier color signal,
In a magnetic recording/reproducing device that frequency-modulates the luminance signal, converts the frequency of the carrier chrominance signal to a frequency lower than this frequency-modulated luminance signal band, and multiplexes both for magnetic recording, the frequency band of the carrier chrominance signal is low-frequency-modulated. The frequency is selected to be within the lower frequency band.

The 2V switching circuit 3 is used when the magnetic recording/reproducing device forms one video track for one field of the video signal, and is used when the magnetic recording/reproducing device forms one video track for one field of the video signal. 2 vertical scanning periods (2V) by a signal formed from the vertical synchronization signal of the video signal to be output
The pilot signals of f ₁ and f ₂ are alternately switched and output each time. Therefore, the 2V switching circuit 3 selectively outputs the pilot signal of frequency f ₁ during a certain two-field period,
During the next two field periods, the pilot signal of frequency f ₂ is switched and output, and in the next two field periods, the pilot signal of frequency f ₁ is switched and output, and thereafter the same switching operation as above is repeated.

The pilot signal selectively output from the 2V switching circuit 3 is supplied to the gate circuit 4, where the gate signal is intermittently output every horizontal scanning period (1H) using a pulse formed from a horizontal synchronization signal separated from the video signal, for example. be done. Therefore, the output signal of the gate circuit 4 is a pilot signal that is intermittently output every 1H, and whose frequency is alternately switched every two fields. The output pilot signal of the gate circuit 4 is frequency division multiplexed with a video signal in the form of a signal to be recorded, and is recorded by a rotating video head 5 forming an inclined track on a magnetic tape 6. Note that the rotating video head is, for example, two rotating video heads having different azimuth angles from each other, which alternately form one video track in sequence. This is representatively shown in the head.

FIG. 2 shows an example of a track pattern of a magnetic tape recorded by the above recording system. In the same figure,
t ₁ , t ₂ , t ₃ , and t ₄ are inclined video tracks on which the video signal of one field is recorded together with the pilot signal, and tracks t ₁ and t ₂ are adjacent to each other with an H shift of 1.5H. The horizontal synchronizing signal recording positions of the tracks are aligned (so-called H alignment) and recorded. If the video signal to be recorded now is a video signal with 525 horizontal scanning lines per frame, the above H deviation is
Since it is 1.5H, the first part of the video track _t2
If the 263rd horizontal scanning period is adjacent to the second horizontal scanning period of video track _t1 , and the intermittent recording of the pilot signal of frequency _f1 is repeated every 1H of video track _t1 , , just the first
A pilot signal of frequency _f1 is recorded in the 263rd horizontal scanning period, and the pilot signal recording section of video track _t1 and the pilot signal recording section of video track _t2 are not adjacent to each other. In other words,
The pilot signal recording section and the pilot signal non-recording section are adjacent to each other in adjacent tracks _t1 and _t2 .

Similarly, if the recording of the pilot signal is repeated every 1H, the pilot signal of frequency f ₂ will be recorded on video tracks t _{3 and} t ₄ , but as shown in FIG. truck
A track pattern is formed which is not adjacent to the pilot signal recording section of video track _t2 and which is not adjacent to the pilot signal recording section of video track _t4 .

Therefore, when the H deviation is 1.5H, 3.5H, etc., by always performing the gate operation of the gate circuit 4 every 1H, the pilot signal recording section is adjacent to the pilot signal non-recording section on adjacent video tracks. , and some video track (e.g.
A desired track pattern is formed in which the pilot signal frequencies recorded on tracks _t1 and _t3 on both sides of t2) are different frequencies from _{f1 and f2} . Note that if the H shift is selected to be 0.5H, 2.5H, etc., in order to obtain the above-mentioned desired track pattern, it becomes necessary to shift the recording phase of the pilot signal by 1H every 1V, making the circuit configuration complicated.

Next, the operation of the device of the present invention will be explained. Third
The figure shows a block system diagram of an embodiment of the device of the present invention. In the figure, reference numeral 6 denotes a magnetic tape having a tape pattern as shown in FIG. 2, which is reproduced by a rotating video head 5. First, a case will be described in which the rotating video head 5 sequentially scans the video tracks shown as _t1 to _t4 in FIG. 2 accurately without any tracking deviation. , is supplied to the pilot signal frequency detection circuit 7, where the self-track f ₁ or
Only the frequency component of f ₂ is separated and extracted. Therefore,
When no tracking deviation occurs, the output signal of the pilot signal frequency detection circuit 7 is as shown by a in FIG. , are supplied to the gate circuit 9 and the 1V delay circuit 10, respectively.

The 1H pulse generation circuit 8 generates a 1H cycle pulse b shown in FIG. 4B, which is at a high level during a period when no pilot signal is recorded on the video track being scanned, and at a low level during a period when a pilot signal is recorded. This circuit generates the 1H period pulse b and outputs it to the gate circuit 9 as a gate pulse. As a result, the gate circuit 9 gate-outputs the input signal from the pilot signal frequency detection circuit 7 only during a period when no pilot signal is recorded on the video track being scanned, but when no tracking deviation occurs, f ₁ , f Since the _two frequency components are at zero or negligibly low levels, the output signal of the gate circuit 9 is not generated as shown by c in FIG. 4C. Therefore, it is provided after the gate circuit 9, and outputs a detection voltage of negative polarity and in accordance with the input signal level, for example, when the input signal frequency is _f1 ,
On the other hand, when the input signal frequency is _f2 , the output signal of the pilot signal detection circuit 11, which is configured to output a detection voltage of positive polarity and in accordance with the input signal level, also becomes zero as shown by g in FIG. 4G. becomes.

On the other hand, the 1V delay circuit 10 consists of a monostable multivibrator triggered by the pilot signal _f1 and a monostable multivibrator triggered by the pilot signal _f2 , and the pilot signal to be reproduced is switched from _f2 to _f1 . It outputs a signal at a high level for a 1V period from the time the signal goes off, and a signal at a high level for a period of 1V from the time the pilot signal to be reproduced switches from _f1 to _f2 . Therefore, when a magnetic tape with a track pattern as shown in _FIG . A signal e which is at a high level during the _t3 scanning period is outputted and supplied to the 2V pulse generation circuit 12.

The 2V pulse generation circuit 12 outputs a rectangular wave f as shown in FIG. 4F, which rises at the fall of the input signal d and falls at the fall of the input signal e. Therefore,
The output rectangular wave (2V pulse) f of the 2V pulse generation circuit 12 becomes a high level rectangular wave during the reproduction period of video tracks _t2 and _t3 , and becomes a low level rectangular wave during the reproduction period of video tracks _t1 and _t4 . Here, such a rectangular wave f was generated because _, as is clear from _the tape pattern shown in FIG. While the pilot signal frequency of the adjacent track that is reproduced as crosstalk is _f1 , when video tracks _t1 and _t4 are reproduced, the pilot signal is similarly reproduced as crosstalk even if the tracking shift direction is upward. Since the frequency is different from _f2 , this is used as a signal for switching the correction control polarity for the direction of tracking deviation depending on the frequency of the pilot signal detected as crosstalk every 2V cycle.

This rectangular wave f is supplied to the 2V inversion circuit 13,
Here, for example, the polarity of the signal g from the pilot signal detection circuit 11 is inverted only during the 2V period that is the low level. However, since no tracking deviation has occurred here, the signal g is zero as described above, and therefore the output signal of the 2V inversion circuit 13 is zero volts as shown by h in FIG. do not have. The output signal h of this 2V inversion circuit 13
is supplied to the tracking servo circuit 14. The tracking servo circuit 14 displaces the rotating video head 5 in a predetermined direction upward or downward in a direction perpendicular to the scanning direction of the video track according to the polarity of the output signal of the 2V inversion circuit 13.
The video head 5 rotates according to the output signal level of 3.
The above displacement amount is controlled. Here, since the signal h is zero volts, it is detected that no tracking error has occurred, so the rotating video head 5 is not displaced.

The tracking control mechanism for displacing the rotating video head 5 in a direction perpendicular to the scanning direction of the video track may be one using a conventionally known bending bimorph or other various mechanisms.

Next, as shown at 5a in FIG. 5, the operation is performed when the rotating video head 5 straddles and reproduces the upper video track _t2 at the same time in addition to the video track _t3 to be scanned, as shown by 5a in FIG. I will explain about it. In this case, the output signal of the pilot signal frequency detection circuit 7 is as shown in FIG. 6A.
The reproduced pilot signal _f2 from video track _t3 and the low-level pilot signal _f1 reproduced as crosstalk from video track _t2 alternate for 1H.
It appears every cycle. Here, the relative level relationship between the reproduction pilot signals f ₁ and f ₂ is such that as the amount of tracking deviation increases, the level of f ₂ becomes smaller and the level of f ₁ becomes larger. In addition, Fig. 6 A to H
In the figure, the period indicated by _T1 is the period in which a tracking deviation occurs on the video track _t2 side when video track _t3 is scanned, and the period indicated by T2 in A to H in the same figure is the period in which tracking deviation occurs on the video track _t2 side when video track _t4 is scanned. Track t Indicates the period during which tracking deviation occurs on _{the 3} side.

The signal waveforms shown in FIGS. 6B, D, E, and F are the same as the signal waveforms shown in FIGS. 4B, D, E, and F. That is, the output signal waveforms of the 1H pulse generation circuit 8, the 1V delay circuit 10, and the 2V pulse generation circuit 12 are always the same regardless of the presence or absence of tracking deviation if the reproduction mode is the same.

As shown in FIG. 6C, the output signal of the gate circuit 9 is a pilot signal f ₁ which is reproduced as crosstalk from the adjacent track t ₂ during the above period T ₁ , and during the above period T 1 .
At _T2 , the pilot signal _f2 is reproduced as crosstalk from the adjacent track _t3 . The output signal of this gate circuit 9 is supplied to a pilot signal detection circuit 11, and is converted into a detection signal as shown in FIG. 6G according to the pilot signal frequency and level.
This detected signal is supplied to the 2V inversion circuit 13, and is converted into a signal as shown in FIG. 6H by the rectangular wave f shown in FIG. 6F. In other words, in both the above periods _T1 and _T2 , the tracking error signal of negative polarity is
It is taken out from the 2V inverting circuit 13. This tracking error signal of negative polarity indicates that the tracking error of the rotating video head 5 is shifted in the upper tracking direction of the tape pattern in FIG. 2, and its level indicates the amount of tracking error. Therefore, the tracking servo circuit 14 to which this tracking error signal is supplied controls the rotating video head 5 to accurately scan the video track to be scanned.

Next, an explanation will be given of the operation when a tracking deviation occurs, in which the rotating video head 5 simultaneously straddles and reproduces not only the video track to be scanned but also the adjacent video track below (to be scanned next). FIG. 7 shows a position where the rotating video head 5 is at a position indicated by 5b, that is, a tracking deviation state in which the video track _t3 and the adjacent video track _t4 are played back simultaneously. Such tracking deviation occurs during the period shown as _T3 in FIGS. 8A to 8D, and during _the period shown as _T4 in FIGS. ₅ (not shown in FIG. 2) is also played back at the same time. In addition, the fourth
The signal waveforms corresponding to figures B, D, E, and F are omitted because they are the same.

During the above tracking deviation playback, the gate circuit 9
The output signal of t is a pilot signal from an adjacent track that is reproduced as crosstalk as described above, and therefore, in the above period T ₃ , the video track t ₄
The pilot signal f ₂ recorded in is played back,
During the period _T4 , the pilot signal _f1 recorded on the video track _t5 is reproduced as crosstalk. Further, assuming that the amount of tracking deviation is larger in period T ₄ than in period T ₃ , the output signal of the gate circuit 9 is smaller than the pilot signal f ₂ reproduced in period T ₃ , as shown in FIG. 8B. Also, the reproduction level of the pilot signal _f1 reproduced during the period _T4 is higher. This means that the larger the amount of tracking deviation, the more
This is because the area of the portion of the rotating video head 5 that makes sliding contact with the adjacent video track becomes relatively large.

Therefore, as shown in FIG. 8C, the output signal of the pilot signal detection circuit 11 becomes a detection signal of positive polarity and a small level during period _T3 , while it becomes a detection signal of negative polarity and a relatively large level during period _T4 . When the voltage is passed through the 2V inverting circuit 13, a positive tracking error signal as shown in FIG. Since this tracking error signal has a positive polarity, the rotating video head 5 is shifted in the direction of the next video track to be scanned in both periods T ₃ and T ₄ , and furthermore, during period T ₃
The level of T ₄ is greater than the period T ₄
This shows that the amount of tracking deviation is larger.

This tracking error signal causes the rotating video head 5 to be displaced upwardly of the track by an amount equal to the absolute value of the tracking deviation amount, so that only the track to be scanned can be accurately scanned.

The above has described each operation in the case of normal reproduction at the same tape running speed as during recording. When playing video, the output signal of the 2V pulse generation circuit 12 is set to a constant voltage of positive or negative polarity depending on the same video track that is played repeatedly (for example, when video track t2 is played repeatedly, the output signal of the 2V pulse generation circuit ₁₂ is set to a constant voltage of positive or negative polarity. (When reproducing _t4 repeatedly, a constant voltage of negative polarity is used.) As a result, even when playing still images, the same video track can be played back accurately and repeatedly. It goes without saying that the pulse period of the 2V pulse generation circuit 12 is determined in accordance with the speed ratio during fast motion reproduction or slow motion reproduction.

In addition, in the above embodiment, the pilot signal is set to 1H.
Although the data is recorded over the entire period, it may be possible to record only a certain period within 1H, such as a horizontal blanking period. When reproducing a magnetic tape on which a pilot signal is recorded for the entire 1H period, a bistable multivibrator is generally used for the 1H pulse generation circuit 8, and a magnetic tape on which the pilot signal is recorded only for a certain period within 1H is generally used. When playing back a tape, a monostable multivibrator is used as the 1H pulse generating circuit 8.

Furthermore, in the above embodiments, the information signal to be recorded and reproduced was described as a video signal, but an apparatus that magnetically records and reproduces a signal in a form similar to a video signal by adding a composite synchronization signal to a signal obtained by pulse code modulating an audio signal, etc. The present invention can also be applied to

Furthermore, the recording medium does not have to be a magnetic tape;
Other recording media such as magnetic disks may also be used. Furthermore, it is desirable that the track pattern does not have a guard band, but since the pilot signal has a low frequency, it is likely to be picked up as crosstalk from adjacent tracks. You can go to Still further, the pilot signal may be inserted into the horizontal blanking interval, in which case the pilot signal frequency may be selected within the low-conversion carrier chrominance signal frequency band.

As described above, in the tracking device of the magnetic reproducing apparatus according to the present invention, a pilot signal of the same frequency for detecting a tracking error is intermittently recorded on each track at predetermined intervals, and
Pilot signals of different frequencies are multiplexed and recorded on information signals on both sides of the track, and magnetic recording is performed so that the pilot signal recording sections are not adjacent between adjacent tracks. When the pilot signal is separated and extracted from the reproduced signal, and the frequency of the pilot signal obtained by the separation and extraction is switched at every predetermined period and reproduced, the recorded pilot signal of the track to be scanned is recorded. A tracking error signal is obtained based on the frequency of the pilot signal other than the section and its reproduction level, and this tracking error signal is used to intermittently reproduce the pilot signal of the same frequency for each track reproduction (i.e., the track to be scanned). Since the signal converting element is configured to be displaced upward in the direction perpendicular to the track scanning direction (so that the pilot signal is not reproduced outside of the previously recorded pilot signal recording section), it is possible to use a track pattern without a guard band or with an extremely small guard band width. It can be applied to recording media reproducing devices, and since the pilot signal frequency is lower than conventional ones, the signal conversion element can be tracked and controlled with a simple circuit configuration, and it can also be used to reproduce recording media at a speed different from the recording speed. It has the advantage of being able to obtain high quality reproduction information signals.

[Brief explanation of the drawing]

FIG. 1 is a block system diagram showing an example of a recording system of a recording medium tracked and reproduced by the apparatus of the present invention, and FIG. 2 is a diagram showing an example of a track pattern on a magnetic tape obtained by the recording system of FIG. , FIG. 3 is a block system diagram showing one embodiment of the device of the present invention, FIGS. 4A to 4H are signal waveform diagrams for explaining the operation during normal tracking in FIG. 3, and FIGS. 5 and 7 are respectively Enlarged views showing the state in which the rotating video heads have tracking deviations, FIGS. 6A-
H and FIGS. 8A to 8D are signal waveform diagrams for explaining the operation of FIG. 3 during tracking deviation reproduction shown in FIGS. 5 and 7, respectively. 5... Rotating video head, 6... Magnetic tape,
7... Pilot signal frequency detection circuit, 8...
1H pulse generation circuit, 9...gate circuit, 11...
... Pilot signal detection circuit, 12 ... 2V pulse generation circuit, 13 ... 2V inversion circuit, 14 ... Tracking servo circuit, t ₁ to t ₅ ... video track.

Claims (1)

[Claims] 1. An information signal having a synchronization signal is recorded by sequentially forming tracks by a signal conversion element, and
In a magnetic reproducing apparatus that uses a signal converting element to reproduce a magnetic recording medium in which the synchronizing signal recording device on the recording track records data aligned in a fixed direction between each recording track, the synchronizing signal recording device on each track on the magnetic recording medium A pilot signal of the same frequency for tracking error detection is intermittently recorded at predetermined intervals, and pilot signals of different frequencies are multiplexed with the information signal and recorded on both sides of the track. At the same time, the pilot signal is separated and extracted from a signal reproduced from a magnetic recording medium in which the pilot signal recording sections are recorded so that they are not adjacent between adjacent tracks, and the pilot signal obtained by the separation and extraction is When the frequency of the pilot signal is switched and reproduced every predetermined period, a tracking error signal is obtained based on the frequency and reproduction level of the pilot signal other than the recorded pilot signal recording section of the track to be scanned, and this tracking error signal is The signal converting element is displaced upward in a direction perpendicular to the track scanning direction so that a pilot signal of the same frequency is intermittently reproduced by the signal every time each track is reproduced, and the signal converting element follows and scans the track to be scanned. A tracking device in a magnetic reproducing device characterized by: