JPS63133340A - Magnetic recorder - Google Patents

Abstract

PURPOSE:To prevent deterioration of a picture quality of a reproducing image by erasing a part where scanning loci are superposed, by recording information recorded in advance, erasing a pilot signal recorded in the superposed part, and recording only a prescribed pilot signal. CONSTITUTION:A magnetic tape 2 running in the direction as indicated with an arrow (a) of a magnetic recorder is wound within an angle range of about 220 deg. to a rotary drum 3 rotating in the direction as indicated with an arrow (b), and recording heads 1A, 1B are placed at an interval of 180 deg. on the drum 3. Also, erasing heads 20, 21 are provided at an angle interval of 90 deg. against the rotational direction (b) of the drum 3 of the heads 1A, 1B. These respective heads 20, 21 have head width TW3 and TW4, and attached to a position of height TH1 from a reference plane (f), respectively. These heads 20, 21 are controlled by signals obtained by allowing the signals of a control circuit 31 for detecting a kind of the tape 2 of a computer constitution, and a control circuit 25 for discriminating a recording time mode, to pass through a gate circuit 27. Also, by outputs of the circuits 25, 27, a current from an erasing power source 28 is supplied to the heads 20, 21.

Description

[Detailed description of the invention] The present invention will be explained in the following order.

A: Industrial field of application B: Overview of the invention C: Prior art (Figs. 9 to 17) D: Problems to be solved by the invention (Figs. 18 to 20) E: Means for solving the problems (Fig. 1, Fig. 3, and Fig. 4) F Effect (Fig. 1, Fig. 3, and Fig. 4) G Example (Fig. 1 to Fig. 8) H Effect of the invention A Industrial application field The present invention relates to a magnetic recording device, and is suitable for application to, for example, an 8 mm video tape recorder (VTR).

B. Summary of the Invention The present invention uses an erasing head in a magnetic recording device to erase recorded information recorded by one of the recording heads in a portion where the scanning trajectories of the recording heads overlap. This achieves a state of just tracking and prevents deterioration of the image quality of the reproduced video.

C. Prior Art Conventionally, in this type of VTR, there are two types of VTRs with different recording times.
H with different azimuth angles for two recording modes
There is a configuration in which the fl recording heads IA and IB are also used.

That is, as shown in FIG. 9, a magnetic tape 2 running in the direction of arrow a is wound in an Ω shape over an angular range of approximately 220 degrees, and is placed on a rotating drum 3 rotating in the direction of arrow A by 180 degrees.
Recording heads IA and IB are magnetic heads having different positive and negative azimuth angles separated by an angular interval of °.
is located.

Further, an erasing head 4 is attached at a position separated from the recording head IA by an angular interval of 90° in the rotational direction of the rotary drum 3.

The recording heads IA and IB are as shown in FIG.
For example, it has a head width TWI of 15 [μm], and is mounted so that its lower end surface coincides with a reference plane f perpendicular to the rotation axis of the rotary drum 3.

On the other hand, the erasing head 4 has a head width TW2 of, for example, 40 (μm), and its lower end surface extends from the reference surface f to the recording track side preceding the recording heads IA and IB by, for example, 15 [μm]. ] at a height TH.

When recording a video signal in the standard time recording mode using the above magnetic head configuration, the magnetic tape 2 travels approximately 40 Cμm during one revolution of the rotary drum 3.

As a result, during recording, as shown in FIG. 11, the recording heads IA and IB have a track pitch of 20 [μm] and a track width of 15, with the guard band portion TG in between.
Recording tracks TAI, TBI, TA2, I with azimuth angles equal to A in [μm] and date recording heads IA and IB
B2... (Hereinafter, the recording tracks TAI, TA2... corresponding to the recording head IA will be referred to as the A recording track, and the recording tracks TBI, I corresponding to the magnetic head IB.
B2 . . . are called B recording tracks) are sequentially formed on the magnetic tape 2.

The erasing head 4 scans the two recording tracks TAI and TBI in advance of the recording heads IA and IB, and erases the prerecorded video signal. In this case, since the erasing head 4 is mounted at a position separated by an angular interval of 90' from the recording head IA, While the rotating drum rotates 90 degrees, the magnetic tape 2 travels a distance of 10 (μm) toward the trailing side (i.e., 5 [μm] from the side edge TBOS of the recording track TAI).
(position shifted to the leading side).

On the other hand, when recording a video signal in the long-time recording mode, the magnetic tape 2 travels a distance of about 20 [μm], which is 1/2 of that in the standard time recording mode, during one rotation of the rotating drum 3.

Therefore, the recording heads IA and IB are 5 [μm] apart from each other.
By drawing scanning trajectories that overlap each other and overwriting video signals in the overlapping portions, recording tracks TAI, TBI, TA2, IB2, etc., having an azimuth angle equal to that of the recording heads IA and IB are created. It is designed to form...

That is, as shown in FIGS. 13 and 14, the recording head IB first scans the magnetic tape 2 which has been demagnetized by the erasing head 4 with a track width of 15 (μm), and then the recording head IB scans the magnetic tape 2, which has been demagnetized in advance. The recording heads IA, separated by an angular spacing of 180°, scan.

At this time, the magnetic tape 2 travels a distance of 10 [μm] while the rotating drum 3 rotates by the angular interval, and thus the recording head IB travels a distance of 10 [μm].
Scanning trajectories are drawn such that A overlaps by 5 [μm].

During this period, since the erasing head 4 is mounted shifted toward the recording track that precedes the recording head IB by 15 [μm], the rotating drum 3 is placed at a height of 90 [μm] at the height of 15 [μm]. The position ahead of the recording head IB is scanned by a distance of 20 [μm], which is the sum of the distance 5 [μm] that the magnetic tape 2 scans while rotating.Therefore, the position recorded on the scanning trajectory of the recording head IB is scanned. A portion of the video signal that overlaps with the scanning locus of the recording head IA is not erased by the erasing head 4, but is erased by being overwritten by the recording head IA.

In this way, a B recording track TBIL having a width equal to the azimuth angle of the recording head IB is formed in an area of width 10 (μm) on the trailing side of the scanning trajectory of the recording head 180 having a width of 15 [μm].

Similarly, the recording head IB draws a scanning trajectory that overlaps the scanning trajectory of the recording head IA by 5 μm (at this time, after the recording head IA scans, the recording head IB Between the intercostals until scanning, erasing head 4
scans the leading side of the magnetic tape 2 with a delay from the recording head IB, and thus the overlapping portion ARO is also overwritten by the recording head IB, so that the width of the recording head IB is 15 [ The A recording track TA1 is formed in an area with a width of 10 [μm] out of the scanning trajectory of [μm].

Furthermore, in this type of VTR, a pilot signal is recorded on each recording track at the same time as a video signal.
(automatic tracking follo
wing) type tracking control is used.

That is, as shown in FIG. 15, the frequencies 103 [KHz) and 119 [KHz] output from the pilot signal generation circuit 6
(KHz), 165 CKHz) and 149 (KH
z) pilot signals Sfl, Sr2, Sr3 and Sr
4 is received by the selection circuit 7. The selection circuit 7 is connected to the rotating drum 3
Pilot signals Sfl, Sr2, Sf'3 are generated at the timing of switching pulse SWP obtained in synchronization with 0 rotation.
, Sr4, the output is switched and supplied to the recording heads IA and IB.

Thus recording tracks TAI, TBI, TA2, TB2
...and TALL, TBIL, TA2L, TB
Pilot signals sB and Sr2 are sequentially applied to 2L...
, Sr3 and Sr4 are recorded together with the video signal.

During reproduction, the preceding recording track and the following recording are obtained by crosstalk of the reproduction head (in the configuration shown in FIG. 9, the recording head is used as the reproduction head by switching to reproduction operation). Detect the signal level of the pilot signal recorded on the track,
Just tracking is achieved by controlling the crosstalk amounts of the pilot signals to be equal.

That is, the reproduction signal SPB obtained through the reproduction heads IA and IB is received by the low-pass filter 8, and the pilot signal 5PBf is separated and output to the multiplication circuit 9. At this time, as shown in FIG. 16, if a tracking error occurs on the recording track side where the reproduction heads IA and IB lead, the signal level of the pilot signal recorded on the preceding recording track increases, and the signal level of the pilot signal recorded on the preceding recording track increases. The signal level of the pilot signal recorded on the recording track decreases.

On the contrary, if a tracking error occurs on the recording track side that the reproduction heads IA and IB follow, the signal level of the pilot signal obtained from the preceding recording track decreases, and the signal level of the pilot signal obtained from the preceding recording track decreases. The signal level of the obtained pilot signal increases.

Thus, when the reproducing heads IA and IB scan positions at equal distances from the preceding recording track and the following recording track (that is, when just tracking), the signal levels of the two pilot signals become equal.

The multiplication circuit 9 converts the multiplication signal SMIX of the pilot signals Sfl, Sr2, Sr3, and Sr4 output from the selection circuit 7 and the pilot signal 5PBf output from the low-pass filter 8 into center frequencies of 16 (KHz) and 47 (KHz).
Hzl to bandpass filters 10 and 11, and the output signals of the bandpass filters 10 and ]1 are outputted to a subtraction circuit 14 via diodes 12 and 13, respectively.

Therefore, the playback head IA is on the A recording track TAITA2.
When scanning ...... and TAIL, TA2L, old..., DC voltages v2 and vl proportional to the signal level of the pilot signal obtained from the preceding recording track and the following recording track are applied to the diode, respectively. It is output from 13 and 12.

The playback head IB is on B recording tracks TBI, TB2...
..., TBIL, TB2L, etc., when scanning the A recording tracks TAI, TA2..., TALL, TA2L... DC voltages 1 and V2 proportional to the signal level of the pilot signal obtained from the recording track to be used and the recording track to follow are applied to the diodes 12 and 13, respectively.
is output from.

The selection circuit 15 receives the subtraction signal 5REF output from the subtraction circuit 14 and also receives the inverted subtraction signal 15REF obtained via the inversion amplifier circuit 16, so that the reproducing head IA moves to the A recording track TAI at the timing of the switching pulse SWP. , TA2...and TALL, TA
During the period of scanning 2L..., the inverted subtraction signal I
The output is switched from 5REF to the subtraction signal 5REF.

The buffer circuit 17 receives the output and thus the 17th
As shown in the figure, when both the reproduction heads IA and IB make a tracking error on the leading side via the buffer circuit 17, the signal changes to the negative side, and conversely, when the tracking error occurs on the trailing side, the signal changes to the positive side. Tracking error signal SE
P can be obtained.

Therefore, by controlling the tracking so that the tracking error signal SER becomes O level, just tracking can be performed, thereby making it possible to obtain a reproduced video with a good signal-to-noise ratio.

D Problems to be Solved by the Invention However, since the frequency of the pilot signal is set to a relatively low frequency compared to the video signal, recording tracks cannot be formed by overwriting as in the long-time recording mode described above. In this case, as shown in FIG.
There is a problem in that the pilot signal of the adjacent recording track on the trailing side is not completely erased and remains in the overwritten portion ARO of AOL, TBOL, TAIL, TBIL, . . . .

At this time, in addition to the predetermined pilot signal, the pilot signal of the adjacent recording track is recorded in the overwritten portion ARO, and as shown in FIG. 19, the pilot signal obtained from the subsequent recording track is recorded. The overwritten portion AR shown using the song mL2 from the signal level of L1
A biloft signal L3 whose signal level is increased by the pilot signal obtained from O is obtained.

Then, the signal levels of the pilot signals L4 and L3 obtained from the leading side and the trailing side become equal at a position shifted toward the leading side by the amount of track deviation ΔT from the just tracking position, and the difference is shown in FIG. 20. , a song '41AL5 in which the pilot signal where the tracking error signal SEP is overwritten has been completely erased.
The data is shifted by the amount of track deviation ΔT to a curve L6 indicating a state in which the data cannot be completely erased.

As a result, a tracking error occurs by the amount of tracking deviation ΔT, and there is a problem in that the signal level of the reproduced video signal decreases by that amount.

When the signal level of the reproduced video signal decreases in this way, the image quality of the reproduced video deteriorates in practical terms.

Furthermore, when a magnetic tape that has been overwritten in this way is played back on a VTR equipped with a wide playback head,
By causing a tracking error on the preceding side, the video signal recorded on the adjacent recording track on the preceding side can be obtained via the reproduction head, and the S/N ratio of the reproduced video signal deteriorates accordingly. Therefore, there was a problem that the image quality of the reproduced video deteriorated.

The present invention has been made in consideration of the above points, and it is an object of the present invention to propose a magnetic recording device that can prevent the image quality of reproduced video from deteriorating even when overwriting is performed.

In order to solve this problem, in the present invention, first and second recording heads LA having different azimuth angles,
By the helical scan double azimuth recording method using IB, the recording track TAIL is recorded so that a part of the scanning trajectory of the first and second recording heads IA and IB on the magnetic tape 2 overlaps with each other. , T.B.I.
In a magnetic recording device configured to form L, TA2L, TB2L, etc., after the first or second recording head IA (IB) scans, the second or first recording head Until the IB (IA) scans, the first and second recording heads LA (IB)
Area A where the scanning trajectories of the recording heads LA and IB overlap
Erasing head 20 for erasing recorded information recorded on the RO
．． 21.

By using the F-action erasing head 20.21 to erase the recorded information previously recorded in the area ARO where the scanning trajectories overlap, the pilot signal previously recorded in the area ARO where the scanning trajectories overlap is erased. It is possible to record only predetermined pilot signals. By thus being able to prevent tracking deviations, it is possible to prevent deterioration of the image quality of the reproduced video.

G example An embodiment of the present invention will be described in detail below with reference to the drawings.

In FIG. 1, in which parts corresponding to those in FIG. 9 are given the same reference numerals, an erasing head 20 is provided in place of the erasing head 4, and the erasing head 20 is located at a position separated from the erasing head 20 by an angular interval of 180°. A head 21 for use is provided.

The erasing heads 20 and 21 have head widths TW of 40 [μm] and 15 (μm), respectively, as shown in FIG.
3 and TW4, each of which is mounted at a position at a height THI shifted by 5 [μm] from the reference plane f toward the preceding recording track.

With this configuration, the magnetic heads IA, IB, 20, and 21 operate as shown in FIGS. 3 and 4 in the long-time recording mode.
Draw the scanning trajectory shown in the figure.

That is, since the magnetic heads IA, IB, 20 and 21 are installed at angular intervals of 90 degrees, the magnetic tape is 5 [μm] travels.

Therefore, since the erasing head 21 is mounted shifted 5 [μm] to the leading side with respect to the recording head IA and is separated from the recording head IA by an angular interval of 90°, the recording head LA is When scanning the overwritten portion ARO of the recording track TBOL and the recording track TAOL,
A position shifted by 10 [μm] from the recording head IA to the leading side (i.e., the overwritten portion A of the recording track TAIL)
By scanning the recording track RO and recording track TBOL and passing a degaussing current through the erasing head 21 during this scanning, the pilot signal and video signal recorded in the overwritten portion by the recording head IA can be erased.

On the other hand, the recording head IB is mounted with a displacement of 5 [μm] from the erasing head 21 to the trailing side, and is separated from the erasing head 21 by an angular interval of 90°. scan over the scanning locus.

Similarly, the erasing head 21 is 5[
μm] toward the leading side, and is separated from the recording head IB by an angular interval of 90°. TBIL, TA2L
and four recording tracks of TB2L).

Therefore, during this period, by flowing a demagnetizing current to the erasing head 20, the pilot signal and video signal recorded in the overwritten portion ARO by the recording head IB can be erased.

The erasing heads 20 and 21 are connected to a drive control circuit as shown in FIG.

That is, the control circuit 25 having a microcomputer configuration is
Receiving the mode switching signal SMI of the standard time recording mode and the long-time recording mode and the recording/reproducing mode switching signal SM2,
A control signal SC1 is applied to the switch circuit 26 and the gate circuit 27.
and outputs SC2.

The switch circuit 26 responds to the control signal SCI to switch the VT
When R enters the recording mode, the demagnetizing current IER output from the demagnetizing power source 28 is output to the erasing head 20.

On the other hand, the index detection circuit 29 detects index holes provided in the magnetic tape cassette case 3o according to the type of magnetic tape (coated type magnetic tape in which a magnetic layer is formed by coating a magnetic material on the base). or a vapor-deposited magnetic tape with a magnetic layer formed on the base by sputtering, for example), the control circuit 31 synthesizes tape information DT representing the type of magnetic tape. Output to.

The control circuit 31 controls the VT based on the tape information DT.
When coated magnetic tape is loaded on R, gate time! A control signal sc3 is output to the terminal 27.

On the other hand, the control circuit 31 stops outputting the control signal SC3 when the vapor-deposited magnetic tape is loaded.

Incidentally, in the case of a vapor-deposited magnetic tape, the residual magnetic flux B of the coated magnetic tape shows the magnetization characteristic as a curve MSP, as the magnetization characteristic is shown as a curve SE in FIG.

The residual magnetic flux B is large compared to , and the coercive force HC1 is smaller than the coercive force HCP.

Therefore, the vapor-deposited magnetic tape has the characteristic that it is more easily magnetized and demagnetized than the coated magnetic tape, and the pilot signal can be easily erased even by overwriting.

The gate circuit 27 controls, based on the control signals SC2 and SC3, when the VTR is set to the recording mode and the long-time recording mode and the coated magnetic tape is loaded.
The control 31 signal SC4 is output to the switch circuit 32, and the degaussing current IER is supplied to the erasing head 21.

In this way, in the overwritten portion ARO described above with reference to FIGS. 3 and 4, the pilot signals and video signals recorded by the recording heads IA and IB that run first are demagnetized by the erasing heads 20 and 21. Thereafter, new video signals and pilot signals are recorded by the subsequent recording head IB or IA.

Therefore, in the overwritten portion ARO, only a predetermined pilot signal is recorded, and just tracking can be achieved during reproduction.

On the other hand, if the magnetic tape loaded into the VTR is a vapor-deposited magnetic tape, the switch circuit 32 is turned off, and as a result, only the erasing head 20 operates.

At this time, A recording track TALL, TA2L...
In the overwritten portion ARO of . will be deleted.

Further, B recording tracks TBIL and TB where the recording head IB first traveled and recorded the pilot signal and video signal
In the overwritten portion ARO of 2L..., after the erasing head 20 is demagnetized, the recording head IA records a predetermined pilot signal and video signal.

In fact, in vapor-deposited magnetic tapes, the pilot signal can be erased effectively even by overwriting, and as a result, even when only one erasing head 20 is operated as described above, playback is possible. You can just track it at any time.

Therefore, when a vapor-deposited magnetic tape is used, since the degaussing current rER is not supplied to the erasing head 21, the power consumption of the VTR as a whole can be reduced accordingly.

Incidentally, in the standard time recording mode, each magnetic head I
A, IB, 20 and 2I draw scanning trajectories as shown in FIGS. 7 and 8.

That is, the erasing head 20 erases the recording tracks TA1 and T.
After scanning BI, these recording tracks TAI, and the guard band portion TG on the trailing side of TBIO, the recording head 1
scans the A recording track TA2. Next, the erasing head 20 erases the width of 10 Cμ on the trailing side of the B recording track TBIO.
m] and the guard band portion TG on the trailing side thereof, the recording head IB moves to Bgtl! The recording head TB scans.

At this time, regardless of the type of magnetic tape, the switch circuit 32
is turned off, and as a result, new video signals and pilot signals can be recorded while sequentially erasing the video signals and pilot signals previously recorded on the recording track using only the erasing head 20.

Therefore, power consumption can be reduced in the same way as when using the above-described vapor-deposited magnetic tape.

According to the above configuration, the pilot signal recorded on the subsequent recording track does not remain in the overwritten portion, so that just tracking can be performed during reproduction.

Therefore, it is possible to avoid a decrease in the signal level of the reproduced video signal, and thus it is possible to prevent the image quality of the reproduced video from deteriorating.

Also, when a magnetic tape recorded in this way is played back on a VTR equipped with a wide playback head,
Mixing of video signals from adjacent tracks on the preceding side can be prevented, and as a result, a reproduced video signal with a good SN ratio can be obtained.

In the above embodiment, each magnetic head is rotated at 90°.
In the above description, the recording heads IA and IB are arranged on the rotating drum with an angular interval of 180° apart, but the present invention is not limited to this. The erasing heads 20 and 21 may be arranged at different angles, and the height positions relative to the recording heads IA and IB may be set accordingly.

Further, in the above embodiment, a case was described in which the head width of the erasing head 21 was made equal to the head width of the recording heads IA and IB, but the present invention is not limited to this, and the point is that the recording head scans first. The head width may be set so that the video signal and pilot signal recorded in the overwritten portion can be erased.

Furthermore, in the above-described embodiment, a case was described in which the erasing heads 20 and 21 scan so that their lower end surfaces coincide with the trailing side surfaces of each recording track, but leakage magnetic flux of the erasing heads 20 and 21 Since a part of the video signal and pilot signal recorded on the trailing recording track may be erased due to this, the mounting positions of the erasing heads 20 and 21 may be shifted to the preceding side by that amount.

Furthermore, in the above embodiment, the VTR is equipped with two recording modes: a standard time recording mode and a long-time recording mode.
Although the present invention has been described with reference to the case where the present invention is applied, the present invention is not limited to this, and can also be applied, for example, to a case where the scanning trajectories of the recording fields overlap each other in a VTR having only one recording mode. I can do it.

Furthermore, in the above embodiment, the case where the present invention is applied to an 8 mm video format VTR is described, but the present invention is not limited to this, but can be widely applied to VTRs of various formats, and is not limited to VTRs. It can be widely applied to magnetic recording devices that record recorded information by sequentially forming recording tracks diagonally on a magnetic tape.

H Effects of the Invention As described above, according to the present invention, only a predetermined pilot signal can be recorded on the recording track, so it is possible to perform just tracking during playback, thereby preventing deterioration in the image quality of the playback video. It is possible to obtain a magnetic recording device that can prevent this.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing the configuration of a rotating drum of a VTR according to the present invention, FIG. 2 is a side view showing the side surface unfolded, and FIG.
4 and 4 are route diagrams showing the scanning loci of each magnetic head in long-time recording mode, FIG. 5 is a block diagram showing the drive control circuit of the erasing head, and FIG. 6 is a coating type magnetic tape and Fuji A characteristic curve diagram showing the magnetization characteristics of type magnetic tape,
Figures 7 and 8 are route maps showing the scanning trajectories of each magnetic head in standard time recording mode, and Figure 9 is a diagram of a conventional VTR.
10 is a plan view showing the configuration of the rotating drum, FIG. 10 is a side view showing the side surface of the rotating drum developed, FIG.
Figure 2 is a route map showing the scanning locus of each magnetic head in the standard time recording mode, Figures 13 and 14 are route maps showing the scanning locus of each magnetic head in the long time recording mode, and Figure 15 is an ATF map. 16 and 17 are signal waveform diagrams for explaining the operation of the tracking control circuit. FIG. 18 is a route map showing the recording pattern of pilot signals in long-time recording mode.
9 and 20 are signal waveform diagrams for explaining the operation. IA, IB... Recording head, 2...
Magnetic tape, 3...Rotating drum, 4.20.2
1...Erasing head, 25.31...
Control circuit, 26.32...Switch circuit, 28
・・・・・・Power supply for degaussing. Configuration of the rotating tram Part I] Expanded configuration of the rotating drum package $ 2 Figure -, Heud canter control circuit for the consumer Figure S 72, #111 Figure 6 Rotating tram Structure of Figure 9 Rotating Drawer A Structure Related to Blind F) To Figure A D Tracking Enlightenment Q Node Circuit Figure 15 Ha0 Iro Shito Value Chi J% 16 Cause Tracking 1 Rai Hold 17 Figure Thousand Hour Record At the 7th hour, you will receive a letter of the letter Asahi! Figure 8 Pilot number 19 Figure 1 Tracking 1 Figure 20

Claims (1)

[Claims] By a helical scan double azimuth recording method using first and second recording heads having different azimuth angles, one of the scanning trajectories of the first and second recording heads on the magnetic tape is recorded. In a magnetic recording device configured to form a recording track by recording in such a manner that portions overlap each other, after the first or second recording head scans, the second or first recording head is scanned. The first or second recording head scans the first and second recording heads until the recording head scans.
1. A magnetic recording device comprising an erasing head for erasing recorded information recorded in a portion where the scanning trajectories of the recording heads overlap.