JP2002312993A - Track shifting method and magnetic recording and reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the occurrence of a disturbance in a reproduced image due to thinning of a track width at a connection recording in a magnetic recording and reproducing device for performing recording and reproducing in both an SP mode for normal recording and an LP mode for long-term recording with a common head. SOLUTION: An envelope signal level detection circuit 2 detects the signal level of a reproduction envelope outputted from a head amplifier 1 and stores the signal level in a memory 4. A computing element 5 performs tracking control in short playing when the connection recording is performed by performing comparison operation of the signal levels of respective tracks. Track shifting to reduce protruded quantity of the head with respect to the last track of a recorded area is performed at this stage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an SP for normal recording.
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus of a type for recording / reproducing a mode and an LP mode for long-time recording with a common head, and more particularly to a track shift method for reducing a problem of a thin track at the time of continuous recording.

[0002]

2. Description of the Related Art Conventional video tape recorder (VTR)
The tracking of a magnetic recording / reproducing apparatus using a magnetic tape as a medium will be described. In a VTR, it is necessary for a head to accurately track a recording track for accurate reproduction of a recorded signal. For this reason, in an 8 mm video or digital VTR, an ATF (Automatic Trunk) that performs tracking control by superimposing a tracking pilot signal on an information signal and recording the information signal on the recording track itself and detecting the pilot signal.
ack Finding) The servo method is adopted.

In the following description, the mode for normal recording is designated as SP
The mode for long-time recording is called an LP mode. FIG. 6 is a track trace diagram for explaining the arrangement of pilot signals on a recording track and the problem of a thin track occurring at the time of continuous recording in the prior art. In the magnetic tape 31 of FIG.
Reference numerals 9 denote recording tracks on which information signals are recorded in the LP mode, respectively, and are referred to as a first track group. Of these, the first pilot signal F1 or the second pilot signal F2 having a different frequency is recorded superimposed on the information signal for each single track. Here, it is assumed that the frequency f2 of the second pilot signal F2 is higher than the frequency f1 of the first pilot signal F1 (f1 <f2).

As shown in FIG. 7, a rotary head cylinder 21 around which a magnetic tape 31 is wound has a first head 20a and a second head 20b at positions separated from each other by 180 °.
Is attached. When the second head 20b records an information signal or a video signal, the pilot signal F
Record 1 and F2. As shown in FIG. 6, for example, a second pilot signal F2 is recorded on a recording track T5,
The first pilot signal F1 is recorded on the next recording track T7, and the recording track T1 further skipped by one is recorded.
9, that is, the second pilot signal F2 is recorded on the last track of the first track group.

It is assumed that the first head 20a records only an information signal and does not record a pilot signal. Therefore, the recording tracks T6, T8, and T0 for each skip are recording tracks without a pilot signal. In the case of a digital VTR, pilot signals F1 and F2 are generated by digital modulation. The frequencies f1 and f2 of the pilot signals F1 and F2 are set to sufficiently low values so as not to be affected by azimuth loss.

During reproduction, when the first head 20a scans over the recording tracks T6, T8, and T0 without a pilot signal, the first pilot leaks due to crosstalk from adjacent tracks on both sides. Signal F
1. Signal level (amplitude value) of second pilot signal F2
Is detected. Then, the amplitude values of the pilot signals F1 and F2 are compared, and the rotation speed of the capstan, that is, the feed speed and phase of the magnetic tape 31, are controlled so that the difference value becomes zero. Accurate tracking is performed by such control.

As described above, as one of the functions of the VTR, there is a function of mixing the SP mode for normal recording and the LP mode for long-time recording and switching to either one.
This function is also employed in 8 mm video and the like. The track pitches of the SP mode and the LP mode are different from each other. The track pitch Tp2 in the LP mode is smaller than the track pitch Tp1 in the SP mode (Tp1> Tp2). Specifically, Tp2 is about (1 / 1.5) to (1 / 2.0) of Tp1.

In a VTR having such a function, when recording / reproducing a track in the SP mode for normal recording,
A dedicated head with a large width is mounted on the rotary head cylinder. Separately, when recording / reproducing a long-time LP mode track, a dedicated narrow head is mounted on the rotary head cylinder. Is desirable. However, in order to reduce the cost, it is common practice to employ a dual-purpose head system that uses the same head in the SP mode and the LP mode for recording and reproduction.

FIG. 8A shows a track trace in the normal SP mode, and FIG. 8B shows a track trace in the LP mode for long-time recording. In the LP mode, the track pitch Tp2 is considerably smaller than the head width Tw.

On the other hand, the continuous recording means that the track is continuous with the end of the area where the video signal is already recorded (recorded area), that is, the track following the end track of the first track group.
That is, another video signal is recorded from the first track of the second track group. In the case of continuous recording, once rewind the magnetic tape a little,
The magnetic tape is run while performing tracking control by the TF. This is called short play. By switching to the recording mode after the end of the short play, a new recording track is formed so as to be continuous with the end track of the recorded area. In this way, by performing continuous recording in a state where the tracks are continuous, it is possible to obtain a good image without any disturbance even at the part of continuous recording when reproduced.

[0011]

However, in a magnetic recording / reproducing apparatus employing a head that is used in both the SP mode for normal recording and the LP mode for long time recording,
If continuous recording is performed in the LP mode after recording in the LP mode for a long time recording, the track becomes thin. Although the same problem occurs in the SP mode, it is not as extreme as in the LP mode.
Let's talk in P mode.

The tracking control is performed by the ATF even during the short play. In the tracking control using the ATF, in principle, the head 20a is turned on such that the center of the head 20a in the track width direction coincides with the center of the recording track, as shown in FIG. 8B, for example. In this case, the head 20a protrudes from the adjacent track, and the protruding amount b is 0.5 × (T
w-Tp2).

As shown in FIG. 6, when the recording of the continuous recording is started from the track T0 which is the head recording area of the frame, the left edge of the head 20a protrudes toward the tape feeding side of the end track T9 of the already recorded area. As a result, the track width of the end track T9 becomes narrower than the original track pitch Tp2. This is the thin track. The track thinning amount b is
It is the same as the above-mentioned protrusion amount, and b = 0.5 × (Tw−Tp2). The track thinning amount b is considerably large.

In the case of the SP mode, the track pitch differs from Tp2 of the LP mode in FIG.
In the SP mode, Tp1 is obtained, and the track thinning amount a is also a = 0.5 × (Tw−Tp1).

Specifically, the head width Tw of the head 20a is
= 12 μm, track pitch Tp1 in the SP mode for normal recording = 10 μm, and track pitch Tp2 in the LP mode for long-time recording = 6.6 μm. In this case, the track thinning amount b in the LP mode is 2.7 μm, and the remaining track width is narrowed to 6.6-2.7 = 3.9 μm. This is only 59% of the original track pitch Tp2 = 6.6 μm. Note that, in the SP mode, the track thinning amount a = 1 μm, and the remaining track width is 10−1 =
9 μm, which is 90% of the track pitch Tp1, and is not so affected as in the LP mode.

The large track thinning in the LP mode is caused by the ordinary SP in the dual-purpose head system.
This is because the head width Tw for recording / reproducing the mode has to be considerably large when viewed from the track pitch Tp2 of the LP mode for long-time recording.

When reproducing a recording track that is significantly thinned as described above, only a small reproduction signal can be obtained from the thinned recording track. For this reason, the S / N ratio is deteriorated, and the reproduced screen is disturbed. Especially digital VT
In the case of R, problems such as deterioration of an error rate and inability to obtain a sync signal serving as a synchronization signal for reproduced data occur, and data modification occurs. As a result, a large disturbance occurs at the joint recording portion, and the image quality is degraded.

As a countermeasure against this, Japanese Patent Application Laid-Open No. 09-32614 discloses
No. 4 proposes a track shift method, the contents of which are described below.

Consider a tracking control in short play when performing continuous recording in the LP mode on a magnetic tape recorded in the LP mode. in this case,
In order to reduce the amount of protrusion of the head with respect to the end track of the already recorded area, the reproduction level of the first pilot signal is stored in the memory as the storage value S1 when reproducing the part recorded in the SP mode. Then, the reproduction level of the second pilot signal is stored in the memory as a storage value S2. Next, when reproducing the magnetic tape recorded in the LP mode, the reproduction level of the first pilot signal is stored in the memory as the storage value S3, and the reproduction level of the second pilot signal is stored in the memory as the storage value S4. Then, based on the stored values, the track shift offset value SS is calculated using the following equation. SS = (S3-S1) + (S4-S2)

This value is stored in the memory, and the track shift offset value SS read out from the memory during the short play at the joint recording is added to the tracking error signal ΔS, thereby tracking the track shift offset. Combine with the error signal.

In this case, since the track shift offset for reducing the track thinning is calculated based on the reproduction level of the pilot signal actually measured by the magnetic recording / reproducing apparatus itself, the value of the track shift offset is Therefore, variations in the head output and the amplifier system are automatically expected.

However, such a countermeasure method does not consider variations in the head width Tw. That is,
Regardless of whether the head width variation is large or small, SS is the value obtained by adding the difference between the SP mode and LP mode pilot signals between the first pilot signal and the second pilot signal. Is not calculated. Therefore, when the variation in the head width is large, track thinning occurs even when the above-described countermeasure method is used at the time of continuous recording.

The present invention has been made in view of such a conventional problem, and a track shift method for performing a track shift by avoiding the influence of a head width and reducing a track thinning is disclosed. It is an object to realize a magnetic recording / reproducing apparatus using the method.

[0024]

According to the first aspect of the present invention, a head mounted on a rotary cylinder of a magnetic recording and reproducing apparatus has a head width larger than a track pitch,
During playback, tracking control is performed by aligning the center of the head with the track pattern of the magnetic tape, and following the end track of the first track group in which the video signal is already recorded,
This is a track shift method used at the time of continuous recording in which another video signal is recorded so that tracks of a new second track group are continuous, and a portion which has been previously subjected to continuous recording is reproduced to detect an envelope signal level. Means for detecting the amplitude values of the reproduction envelope signals of the first track group and the second track group, and detecting the amplitude value by the envelope signal level detection means, except for the end track of the first track group for the same head. The amplitude value Sa of the reproduction envelope signal of the track and the amplitude value Sb of the reproduction envelope signal of the end track of the first track group are stored in the amplitude value storage means, and the amplitude values Sa and The track thinning amount in the splicing recording unit is calculated and stored using Sb, and when the splicing recording is newly performed, the already recorded area The track shift amount for reducing the amount of protrusion of said head with respect to end track, is characterized in that determining on the basis of the data of the track skinny amount.

According to the invention of claim 2 of the present application, two kinds of tracking pilot signals having different frequencies are superimposed on a video signal and recorded alternately every other track of the magnetic tape, and the track pitch is different. In order to perform recording or reproduction in two types of modes, the head has a larger head width than the larger track pitch, and during reproduction, the head scans a track on which no pilot signal is recorded and two types of pilots from adjacent tracks on both sides while scanning. A track shift method for a magnetic recording / reproducing apparatus that performs tracking control by detecting a signal and controlling a capstan rotation based on a tracking error signal that is a difference between crosstalk components of the two types of pilot signals, When performing seamless recording, the amplitude value of the playback envelope signal is stored in the amplitude value storage means, and Using the amplitude value held in the amplitude value storage means, the amount of protrusion of the head is calculated to calculate a track shift offset, the track shift offset is stored in the track shift amount storage unit, and a new transition recording is performed. In the tracking control in the short play at the time of performing, the track shift for reducing the amount of protrusion of the head with respect to the end track of the recorded area is performed based on the track shift offset.

According to a third aspect of the present invention, in the track shift method of the second aspect, the track shift offset to be stored in the track shift amount storage section is determined by a reproducing operation of a link recording section of the magnetic recording and reproducing apparatus. When setting, the amplitude value of the reproduction envelope for several frames is stored in the amplitude value storage means, and the track information of the recording change point is detected, whereby the amplitude of the reproduction envelope signal of the end track of the stored recording area is stored. The value Sb is compared with the amplitude value Sa of the reproduced envelope signal one track before recorded by the same head as the value Sb, and based on the comparison result, the track shift amount is determined as the track shift offset unique to the magnetic recording / reproducing apparatus. Ts = (Sa−Sb) × Tp
/ Sa is obtained.

According to a fourth aspect of the present invention, a magnetic recording / reproducing apparatus uses the track shift method according to any one of the first to third aspects.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A track shift method according to an embodiment of the present invention and a magnetic recording / reproducing apparatus using the method will be described with reference to the drawings. In the following description, the magnetic recording / reproducing apparatus is a DV system VTR.

FIG. 1 is a block diagram showing the main configuration of the magnetic recording / reproducing apparatus according to the present embodiment. In the adjustment step of the production line or the splicing recording adjustment, the splicing recording section is reproduced and the track shift amount is adjusted. Represents a block for obtaining. FIG. 6 shows a track pattern at the time of adjustment, and FIG. 2 shows a waveform of a reproduction envelope signal at that time.

In FIG. 1, during reproduction, a head output is input to a head amplifier 1 and amplified by about 1000 times.
The reproduction envelope signal at this time is as shown in FIG.
The reproduced envelope signal is input to the envelope signal level detection circuit 2, and the signal level (amplitude value) of the reproduced envelope for each track is detected. Then, the signal level in each track is stored in the memory 4 as the amplitude value storage means. This memory 4 can store signal levels over several frames.

The envelope signal level detection circuit 2
Are also input to the track information detection circuit 3 to detect the track information. Here, by detecting the recording start point using the recording start information and the like, the signal level Sb of the reproduction envelope of the end track T9 of the recorded area stored in the memory 4 and the signal level Sb of the same head 20
The signal level Sa of the reproduction envelope corresponding to the track T7 two tracks before recorded in b is obtained. Note that the signal level Sa may be an average value of the signal levels of the odd-numbered tracks located before the track T9.

In the continuous recording section, the track becomes thin, so that Sa ≧ Sb. These values are input to the arithmetic unit 5 and compared. The reproduction envelope signals of T7 and T9 are reproduced by the same head 20b, and the reproduction frequency characteristics of the head are the same, and the head amplifier 1 also has the same channel, so that the characteristics of the head and the head amplifier system are the same.

The frequency component of the reproduced envelope signal has a recording frequency of 41.85 MHz as shown in FIG.
It is distributed between DC and about 20 MHz, and the signal component near about 10 MHz is the largest. Pilot signal F
Although the frequencies f1 and f2 of F1 and F2 are different from each other, they are usually set to sufficiently low values so as not to be affected by azimuth loss. For example, f1 = 465 KHz, f2 =
697.5 KHz. However, when the output is viewed as a reproduction envelope, these components hardly change.

The detection of the signal level of the reproduction envelope can be obtained quite accurately by performing, for example, 83.7 MHz A / D conversion. Therefore, the output levels Sa and Sb of the reproduced envelope signals of T7 and T9
Is equal to the ratio of the track widths of T7 and T9.

When the track pitch is Tp, the final track width c is c in the LP mode as shown in FIG.
= Tp2-b, and Sb / Sa = c / Tp2 holds. From this equation, b = (Sa−Sb) × Tp2 / Sa is obtained. Since the track thinning amount b corresponds to the track shift amount, generally, when the track pitch is Tp, the intrinsic track shift amount Ts of the magnetic recording / reproducing apparatus is expressed by the following equation (1). Ts = (Sa−Sb) × Tp / Sa (1)

The reproduction envelope signal may be obtained in an adjustment process of a production line. A connection recording adjustment mode is prepared in the main body, and the reproduction envelope signal is generated only in this mode. It may be obtained and recorded in the memory 4. At the time of normal recording, the information is read from the memory 4 only at the time of continuous recording as a fixed value of the magnetic recording / reproducing apparatus.

The result of the operation performed by the arithmetic unit 5 is given to a track shift amount storage unit 6 composed of a buffer memory, and is stored as a track shift amount. During the short play when performing the link recording, the system controller 7
Sends an instruction to the capstan control circuit 8 using the stored data of the track shift amount, and performs phase control or speed control of the magnetic tape. Thus, the track shift can be performed.

FIG. 4 shows a track pattern of a joint recording section that is track-controlled by such a track shift method.
Shown in Here, the tracks in the already recorded area are: T5 to T
9, and the tracks of the new recording area are T0 to T4. Generally, seamless recording is performed in frame units, that is, at frame boundaries. Assuming that one frame is composed of 10 tracks, the boundaries between the frames are tracks T9 and T0.
It will be located between. Phase control of magnetic tape
Since it involves the servo control of the capstan motor, some time is required. Therefore, the phase control is performed during the short play as described above. Therefore, the head position on the tracks T6 and T8 shown in FIG. 4 indicates the scanning position of the head immediately before the transition recording, in the track shift operation. Therefore, the recording mode has not been entered here.
New recording is started from the track T0.

When the magnetic tape on which the video signal is recorded in this way is reproduced, the video signal is smoothly demodulated because the track pitch Tp2 in the continuous recording section is constant.

On the other hand, when the head height varies and the recording pitch without the pilot signal and the track on which the first and second pilot signals are recorded are not the same, and there is an extreme difference, Does not apply to the above equation (1). However, there is a method of performing a track shift while monitoring the level of a reproduction envelope signal during reproduction as shown in FIG.

When the head is at the position C in FIG. 5A, it is a tracking position during normal reproduction. Here, when the track is shifted to the right, the level of the reproduction envelope signal does not change up to position B, but at position A, the level of the reproduction envelope signal becomes smaller than that during normal reproduction. Similarly, when the track is shifted to the left, the level of the reproduction envelope signal does not change up to the position D, but at the position E, the level of the reproduction envelope signal becomes smaller than in the normal reproduction.

This position D is a position where the left end of the track and the left end of the head become the same. In order to prevent the track from becoming thin during the continuous recording, the continuous recording should be started at the position D. If the track shift is in this state, the pilot signal F1 is also obtained by the reproduction fringe, so that tracking can be performed.

As described above, in the continuous recording, the track shift offset for reducing the thinness of the track is calculated in the magnetic recording / reproducing apparatus itself while the level of the reproduced envelope signal is stored. The value of the track shift offset thus calculated is
Not only the head output and the head amplifier system but also variations in head width are taken into account. In this way, a unique track shift amount of the magnetic recording / reproducing apparatus can be found.

It should be noted that NTSC is used throughout this embodiment.
Has been described with respect to the DV system VTR corresponding to
DV system VTR compatible with the system (the number of tracks is 12)
However, a similar effect can be obtained. Further, the present embodiment has been described for the LP mode, but the same effect can be obtained in the SP mode.

Two types of tracking pilot signals having different frequencies are superimposed and recorded on the information signal for each track of the magnetic tape, and recording / reproduction is performed in two modes having different track pitches. To do so, have a larger head width than the larger track pitch,
At the time of reproduction, the head scans a recording track without a pilot signal and inputs a tracking error signal, which is a difference between crosstalk components of two types of pilot signals from adjacent tracks on both sides, and performs capstan rotation based on the tracking error signal. By performing the control, the same effect can be obtained in a magnetic recording / reproducing apparatus having a tracking control unit that performs tracking control.

[0046]

As described above, according to the track shift method of the present invention, it is effective for the variation of the head width, which is a problem in the conventional track shift. It is possible to realize a magnetic recording / reproducing apparatus which eliminates the occasional reproduction screen disturbance.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a main configuration of a magnetic recording and reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a waveform diagram of a playback envelope signal of a connection recording unit.

FIG. 3 is a frequency characteristic diagram of a reproduced envelope signal.

FIG. 4 is a track pattern diagram of a joint recording unit when the track shift method of the present embodiment is used.

FIG. 5 is a characteristic diagram showing a relationship between a track trace position and an output level of a reproduction envelope signal.

FIG. 6 is a track pattern diagram of a connection recording unit.

FIG. 7 is a layout diagram of cylinder heads in the magnetic recording / reproducing apparatus of the present embodiment.

8A is an explanatory diagram of tracking during normal reproduction in the SP mode, and FIG. 8B is an explanatory diagram of tracking during normal reproduction in the LP mode.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Head amplifier 2 Envelope signal level detection circuit 3 Track information detection circuit 4 Memory 5 Computing unit 6 Track shift amount storage unit 7 System controller 8 Capstan control circuit 20a First head 20b Second head 21 Rotating head cylinder 31 Magnetic tape

Claims (4)

[Claims] A head mounted on a rotary cylinder of a magnetic recording / reproducing apparatus has a head width larger than a track pitch, and performs a tracking control by aligning a center of the head with a track pattern of a magnetic tape during reproduction. This is a track shift method used in splicing recording in which another video signal is recorded so that a new track of a second track group is continued following an end track of the first track group on which a video signal is recorded. Reproducing a portion which has been previously connected and recorded, and detecting the amplitude values of the reproduced envelope signals of the first track group and the second track group using envelope signal level detecting means; Means for reproducing a track other than the end track of the first track group for the same head. The amplitude value Sa of the signal and the amplitude value Sb of the reproduction envelope signal of the end track of the first track group are stored in the amplitude value storage means, and the connection is made using the amplitude values Sa and Sb stored in the amplitude value storage means. The amount of track thinning in the recording section is calculated and stored, and when newly performing continuous recording, the track shift amount for reducing the amount of protrusion of the head with respect to the end track of the already recorded area is set to the track thinning amount. A track shift method characterized in that the track shift method is determined based on the data of (1). 2. A two-track mode, wherein two types of tracking pilot signals having different frequencies are superimposed on a video signal and recorded alternately every other track of a magnetic tape, and recorded or recorded in two modes having different track pitches. In order to perform reproduction, the head has a larger head width than the larger track pitch, and the head detects two types of pilot signals from adjacent tracks on both sides while reproducing a track on which no pilot signal is recorded during reproduction. This is a track shift method of a magnetic recording / reproducing apparatus that performs tracking control by controlling capstan rotation based on a tracking error signal that is a difference between crosstalk components of different types of pilot signals. The amplitude value of the reproduction envelope signal is stored in the amplitude value storage means, and stored in the amplitude value storage means. Using the calculated amplitude value, the amount of protrusion of the head is calculated to calculate a track shift offset, the track shift offset is stored in the track shift amount storage unit, and a short play when performing a new continuous recording is performed. In the tracking control described in (1), a track shift for reducing an amount of protrusion of a head with respect to an end track of a recorded area is performed based on the track shift offset. 3. When the track shift offset to be stored in the track shift amount storage section is set by a reproduction operation of a splicing recording section of the magnetic recording / reproducing apparatus, the amplitude value of the reproduction envelope is adjusted by several frames. By detecting the track information of the recording change point, the amplitude value Sb of the reproduction envelope signal of the stored end track of the recorded area and the amplitude value Sb of the previous track recorded by the same head are stored. It compares the amplitude value Sa of the reproduction envelope signal with the track shift amount T as an inherent track shift offset of the magnetic recording / reproducing apparatus based on the comparison result.
3. The track shift method according to claim 2, wherein s = (Sa-Sb) * Tp / Sa is obtained. 4. A magnetic recording / reproducing apparatus using the track shift method according to claim 1.