GB2266001A - Rotary head magnetic recording and reproducing apparatus - Google Patents
Rotary head magnetic recording and reproducing apparatus Download PDFInfo
- Publication number
- GB2266001A GB2266001A GB9307395A GB9307395A GB2266001A GB 2266001 A GB2266001 A GB 2266001A GB 9307395 A GB9307395 A GB 9307395A GB 9307395 A GB9307395 A GB 9307395A GB 2266001 A GB2266001 A GB 2266001A
- Authority
- GB
- United Kingdom
- Prior art keywords
- recording
- reproducing
- magnetic
- magnetic heads
- exclusive
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 238000004804 winding Methods 0.000 claims abstract description 3
- 238000010586 diagram Methods 0.000 description 5
- 238000001514 detection method Methods 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 3
- 230000005389 magnetism Effects 0.000 description 3
- 230000005236 sound signal Effects 0.000 description 3
- 230000008054 signal transmission Effects 0.000 description 2
- 230000002411 adverse Effects 0.000 description 1
- 230000003111 delayed effect Effects 0.000 description 1
- 230000012447 hatching Effects 0.000 description 1
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
- G11B5/48—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed
- G11B5/52—Disposition or mounting of heads or head supports relative to record carriers ; arrangements of heads, e.g. for scanning the record carrier to increase the relative speed with simultaneous movement of head and record carrier, e.g. rotation of head
- G11B5/53—Disposition or mounting of heads on rotating support
- G11B5/531—Disposition of more than one recording or reproducing head on support rotating cyclically around an axis
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B20/00—Signal processing not specific to the method of recording or reproducing; Circuits therefor
- G11B20/10—Digital recording or reproducing
- G11B20/18—Error detection or correction; Testing, e.g. of drop-outs
- G11B20/1879—Direct read-after-write methods
Landscapes
- Engineering & Computer Science (AREA)
- Signal Processing (AREA)
- Digital Magnetic Recording (AREA)
Abstract
A rotary head type magnetic recording and reproducing device comprises a rotary drum (11), provided with a pair of magnetic heads (Ha, Hb) arranged at an angle of 180 DEG and a further pair of magnetic heads (Ha', Hb') deviated in phase angle from the first mentioned magnetic heads and arranged at angle of 180 DEG from each other, and a winding angle of a tape (T) in contact with the drum is smaller than the phase angle, one pair of magnetic heads being exclusive for recording while the other pair of magnetic heads being exclusive for reproducing. The gap length of the magnetic heads exclusive for reproducing is longer than that of the magnetic heads for recording. <IMAGE>
Description
ROTARY HEAD MAGNETIC RECORDING AND REPRODUCING APPARATUS
The present invention relates to a 4-head system rotary head type magnetic recording and reproducing apparatus in which, for example, PCM data sent from a computer is recorded.
It is an object of the present invention to provide a rotary head type magnetic recording and reproducing device which is designed not to produce an overwrite portion in a track being recorded in order to prevent a reproduced signal from being deteriorated and in which ATF (Automatic Track Following) detection is effected in a stable manner during reproducing operation.
According to the present invention there is provided a rotary head type magnetic recording and reproducing device in which a rotatively driven drum is provided with a first pair of magnetic heads arranged at an angle of 1800, a second pair of magnetic heads deviated in phase angle in a rotating direction from the first pair of magnetic heads and each magnetic head in said second pair of magnetic heads being arranged at an angle of 1800 from each other, the first pair of magnetic heads being exclusively for recording and the second pair of magnetic heads being exclusively for reproducing, and a winding angle of a magnetic tape in contact with the drum subtending at the centre of the drum less than said phase angle, wherein said pair of magnetic heads exclusively for reproducing have a gap length, in a direction perpendicularly intersecting a scanning direction thereof, which is longer than that of said magnetic heads exclusively for recording.
In the above-described means, a conventional recording and reproducing magnetic head is not used but a rotary head device having four heads mounted thereon is used so that one pair of magnetic heads are exclusively used for recording and the other pair of magnetic heads are exclusively used for reproducing. The recording operation is carried out by the magnetic heads exclusive for recording, and in the case where an operation of readafter-write for error monitor is carried out, the recorded data is immediately read by the magnetic heads exclusive for reproducing. The reproducing operation is carried out by the magnetic heads exclusive for reproducing.
The rotary head type magnetic recording and reproducing device is suitable for recording PCM data fed from < computer to back-up a hard disc. In DAT (Digital
Audio Tape), where an audio signal is recorded, an end of data already recorded in case of overlapping writing or the like is searched to join data continuous from the end.
To this end, a recording and reproducing magnetic head may be used. However, in case of data for computer, data need not be strictly joined. For example, as shown in Figure 11, if a recording error of data in a portion indicated at a is found when data are successively recorded, the same data can be continuously rewritten as shown at ss. It is therefore not necessary to perform searching the end by the recording and reproducing magnetic head and continuous recording from the end, and full function can be performed by the magnetic head exclusive for recording. In the case of the magnetic head exclusive for recording, only a recording circuit is connected to said magnetic head, simplifying the circuit structure as compared with the prior art in which a recording and reproducing magnetic head is used.
Unlike the conventional recording and reproducing magnetic head, the magnetic head exclusive for recording need not scan an adjacent track for ATF, so that the length of the magnetic head exclusive for recording can substantially coincide with a track pitch. Thereby, an overwrite between the adjacent tracks can be eliminated to enhance the reproducing accuracy of data. The gap length of the magnetic head exclusive for reproducing can be increased up to covering the full width of an adjacent track. Thereby, in ATF, it is possible to positively read a pilot signal of an adjacent track, and tracking can be accomplished with high accuracy.
A related invention is claimed in British Patent
Application No 89 26095.4 (GB 2 226 180A) from which the present invention is divided.
Embodiments of the invention will now be described, by way of example only, with- reference to the accompanying diagrammatic drawings, in which:
Figure 1 is a block diagram of a circuit showing a rotary head type magnetic recording and reproducing device according to the present invention;
Figure 2 is a plan view showing data being recorded on a magnetic tape from the magnetic head side;
Figure 3 is a plan view showing a state wherein a magnetic head exclusive for recording scans a track;
Figure 4 is a plan view showing a state wherein a magnetic head exclusive for reproducing scans a track Figure 5 shows a plan view showing a state wherein a magnetic head exclusive for reproducing scans a track involving an undulation;
Figure 6 is an enlarged view of Figure 5;
Figure 7 is a diagram showing the influence of an overwrite;;
Figure 8 is a block diagram of a circuit of conventional rotary head type magnetic recording and reproducing device for DAT;
Figure 9 is a plan view showing the recording operation of the conventional recording and reproducing magnetic head;
Figure 10 is a plan view showing the reproducing operation according to the conventional recording and reproducing magnetic head; and
Figure 11 is an explanatory view showing an error state when data of a computer is recorded.
Figure 8 is a block diagram showing a conventional rotary head type magnetic recording and reproducing apparatus for DAT for recording and reproducing a digital audio signal.
The figure shows a two-head system, in which a pair of magnetic heads H1 and H2 are arranged on a rotary drum 1 at an angle of 1800. The pair of magnetic heads H and h2 are both used for recording and reproducing. In
DAT, an open angle of contact length with respect to the rotary drum 1 of a magnetic tape T is 900, the tape T running in a direction as indicated at arrow. The rotary drum 1 rotates counterclockwise in the figure, and the pair of magnetic heads H1 and H2 alternately scan with respect to the magnetic tape T.
Since the magnetic heads H1 and H2 are for recording and reproducing, they are connected to a recording head amplifier 2 and a reproducing head amplifier 3 through a signal transmission means (not shown) such as a rotary transformer. A recording signal processing circuit 4 and a reproducing signal processing circuit 5 are connected to the recording head amplifier 2 and the reproducing head amplifier 3, respectively. A digital audio signal is fed to the recording signal processing circuit 4, and a format including a signal for
ATF (Automatic Track Following) or a subcode signal is formed by the recording signal processing circuit 4 and is amplified by the recording head amplifier 2 and recorded on a recording surface of the magnetic tape T by the magnetic heads H1 and H2. In the reproducing operation, the magnetic heads H1 and H2 scan the magnetic tape T and a signal being recorded is then read and amplified by the reproducing head amplifier 3 and processed by the reproducing signal processing circuit 5. A digital signal output from the producing signal processing circuit 5 is demodulated, detected and amplified.
In the conventional rotary type magnetic recording and reproducing apparatus for DAT, the magnetic heads H1 and H2 are for recording and reproducing, and therefore the gap length is also designed for use with the recording and reproducing, as shown in Figure 8. Figure 9 shows a magnetic head gap during the recording operation, and Figure 10 shows a magnetic head during the reproducing opera#i#n. As shown in these figures, in both the magnetic heads H1 and H2, the length L in a direction perpendicularly intersecting with the scanning direction of the gap G is longer than a track pitch (shown at P in
Figure 9). According to a standard of DAT, a track pitch
P is 13.6jim but the length L is in the order of 21ism.
Figures 9 and 10 show one magnetic head X1 but the other magnetic head H2 has the same gap dimension as that of the magnetic head H1 and has an azimuth angle reversed to H1.
The gap length of the magnetic heads H1 and H2 is longer than the track pitch P as described above. One reason therefor is that ATF is caused to operate during the reproducing operation. An ATF signal is recorded in areas in both ends of each track recorded on the magnetic tape but during the reproducing, the magnetic heads H1 and
H2 read ATF signals (pilot signals) of tracks (1 and 2 in
Figure 10) adjacent on both sides of a track (indicated at 2 in Figure 10) being reproduced, as shown in Figure 10.
By detecting the pilot signals adjacent on both sides as described above, a tracking error direction is detected and a capstan servo is applied accordingly.
The gap length L of the magnetic head is longer than the track pitch P as described above, and therefore, in the recording operation, when data are recorded on the magnetic tape T in order of tracks 1, 2, 3..., an overwrite portion (indicated by hatching in Figure 9) is formed between the adjacent tracks. There can be obtained the merit in that high density recording free from a clearance between the tracks becomes possible by forming the overwrite portion as described. But there also gives rise to an inconvenience caused by the overwrite. That is, when an overwrite portion is formed as shown in Figure 9, a residual magnetism in the overwrite portion cannot be completely removed, and therefore, the S/N ratio of the reproducing signal is lowered by the residual signal in the W rite portion. Figure 7 shows a deterioration of signals due to the overwrite.The axis of abscissa indicates the linear recording density, and the axis of coordinate indicates the symbol error rate when an 8-10 modulated signal is reproduced. As shown, as the linear recording density increases, the error rate increases but if an overwrite portion is present, the error rate increases as compared with the case where the overwrite is not present. In the reproducing apparatus of the overwrite, demodulation is affected because of the deterioration in signal of the overwrite- portion. At the same time, the detection of ATF is adversely affected by the overwrite portion. In the reproducing operation, when an ATF pilot signal of a track to which magnetic head is adjacent is detected, the overwrite portion is also read, and therefore, a residual magnetism results in a turbulence, lowering the tracking accuracy.
In regards to the reproducing operation alone, if the length L of the head gap G increases in order to stabilize the ATF servo, the pilot signal of the adjacent track can be read in a stable manner. However, if the length L unconditionally increases, the width of the overwrite portion shown in Figure 9 becomes excessively widened during the recording operation. In view of the foregoing, in the conventional apparatus, the gap length is set to be about 1.5 times with respect of the track pitch P. However, the head gap for scanning the adjacent track is thus limited so that if an undulation occurred in the track during recording the head gap can sometimes miss the AFT area during reproduction.
An embodiment of the present invention will now be described hereinafter with reference to Figures 1 to 6.
Figure 1 is a block diagram of a circuit showing a rotary head type magnetic recording and reproducing device according to the present invention.
Reference numeral 11 designates a rotary drum, on which four magnetic heads Ha, Hb, Ha' and Hb' are mounted. A pair of magnetic heads Ha and Hb are exclusive for recording and provided at an angle of 1800 from each other. The other pair of magnetic heads Ha' and Hb' are exclusive for reproducing. The magnetic heads Ha' and Hb' exclusive for reproducing are arranged deviated in phase angle by 900 in a rotating direction from the magnetic heads. Ha and Hb exclusive for recording. In this embodiment, an open angle of a contact length of a magnetic tape T to the rotary drum 11 is 90 .The magnetic heads exclusive for recording Ha and Hb are connected to a recording head amplifier 12 through a signal transmission means such as a rotary transformer, and the magnetic head exclusive for reproducing Ha' and
Hb' are connected to a reproducing head amplifier 13 through a rotary transformer or the like. Reference numeral 14 designates a recording signal processing circuit, and 15 designates a reproducing signal processing circuit. Reference numeral 16 designates a comparison circuit used for read-after-write, and a recording error is checked by the comparison circuit 16.
Figure 2 schematically shows a recording state of data to a magnetic tape and data format, showing a state of a recording surface of a magnetic tape T as viewed from the magnetic head.
In the magnetic heads exclusive for recording, an azimuth angle of Ha is reversed to that of Hb. In the magnetic heads exclusive for reproducing, Ha' has the same azimuth angle as that of Ha, and Hb' has the same azimuth angle as that of Hb. In Figure 2, the magnetic heads Ha and Ha' scan a track indicated at (a) and the Hb and Hb' scan a track indicated at (b). A central portion of the track is an area for recording PCM. Opposite portions of the track are areas for recording ATF and SUB codes.
Figure 3 shows a state wherein the magnetic head
Ha exclusive for recording scans the track (a), and Figure 4 shows a state wherein the magnetic head Ha' exclusive for reproducing scans the track (a). Both the magnetic heads are the same in direction of the azimuth angle of the head gap G but are different in length. The gap length L1 of the magnetic head Ha exclusive for recording substantially coincides with the track pitch P. In case of a DAT standard, L1 is approximately 13.6cm. The gap length L2 of the magnetic head Ha' exclusive for reproducing is longer than the gap length L1 of the magnetic head Ha exclusive for recording. The magnetic head Ha' exclusive for reproducing scans the tracks (b) adjacent to left and right together, whereby a pilot signal of ATF of the left and right tracks can be detected. However, the magnetic head Ha' exclusive for reproducing does not perform the recording operation, and therefore, the gap length L2 can be fully increased to cover the full width of an adjacent track. The upper limit L2MAX of the gap length L2 of the magnetic head Ha' exclusive for reproducing is given by
L2MAX = 3P - 4X ... ... (1) wherein P represents a track pitch, and X a maximum value of a linearity of a track. This linearity is an amount of undulation of the track. As shown in Figure 5, there is a possibility of occurring an undulation in a track to be recorded on a tape. In order to express the undulation, deflections in direction of plus and minus with respect to the original track direction are represented by X1 and X2, said X being the maximum value.As shown in Figure 6, it is assumed that the track is undulated from both edges (spacing of 3P) of three tracks inwardly, there sometimes occurs the case where a dimension of a portion at which the spacing between both the edges of three tracks is the minimum value is (3P - 4X). Thereby, the condition that the magnetic head Ha' exclusive for reproducing does not scan the track further adjacent to the adjacent track is that the maximum of the gap length fulfils the aforesaid formula (1).
It is noted that the dimensions of the magnetic head Hb exclusive for recording and the magnetic head Hb' exclusive for reproducing are the same as those of the head Ha and the head Ha', except that the direction of the azimuth angle is reversed.
The operation of the rotary head type magnetic recording and reproducing device shown in Figure 1 will be described hereinafter.
In the recording operation, PCM data fed from the computer is processed by the recording signal processing circuit 14 to form a format, which is amplified by the recording head amplifier 12 and recorded on the magnetic tape T by the magnetic heads Ha and Hb exclusive for recording. In the magnetic heads Ha and Hb exclusive for recording, the gap length L1 substantially coincides with the track pitch P, and therefore, as shown in Figure 3, the overwrite portion will no longer present between the adjacent tracks. Thereby, the deterioration of the reproduced data caused by the residual magnetism will not occur.
The recorded data is delayed by one frame (two tracks) as shown in Figure 2 and read by the magnetic heads Ha' and Hb' exclusive for reproducing. This read signal is amplified by the reproducing head amplifier 13 shown in Figure 1 and processed by the reproducing signal processing circuit 15. The signal is then compared with a recording signal by the comparator 16 to check an error of the recording signal.
Next, in the reproducing operation, the magnetic heads Ha' and Hb', exclusive for reproducing, scan tracks to read a recording signal. The signal is amplified by the reproducing head amplifier 13, processed by the reproducing signal processing circuit 15 and stored with the processed PCM data in a buffer memory or the like, after which it is fed to the computer. As shown in Figure 4, the gap G of the magnetic heads Ha' and Hbf exclusive for reproducing scans adjacent tracks but the direction of the azimuth angle of the recording signal is different, and therefore, a cross talk level of the PCM data or the like is very small. However, the pilot signal in the area of recording ATF is recorded by frequency which can detect even the reverse azimuth.Thereby, the pilot signal is detected by a portion of the head gap G forced out toward the adjacent track. A capstan is supported by the detection of signal and tracking takes place.
It is noted that in the magnetic head exclusive for recording, the gap length L1 does not necessarily coincide positively with the track pitch P but is made to be slightly larger than the track pitch so as to make the overwrite portion with the adjacent track small to an extent such that reproducing is not affected.
As described above, in the present invention, a pair of magnetic heads exclusive for recording and a pair of magnetic heads exclusive for reproducing are provided on a rotary drum. The circuit structure can be simplified by the separate provision of the recording and reproducing magnetic heads as just mentioned. Particularly, only the circuit of the recording system need be connected to the magnetic heads exclusive for recording, and therefore, the circuit connection can also be simplified.
Furthermore, the gap length of the magnetic head exclusive for reproducing is set to be longer than that of the magnetic head exclusive for recording, and therefore, in the recording operation, the overwrite area of the adjacent track can be eliminated or an area thereof can be minimized. Moreover, in the reproducing operation, the
ATF pilot signal of the adjacent track can be positively read by the magnetic head exclusive for reproducing, and the tracking accuracy is enhanced. In addition, even if an undulation of the track occurs as shown in Figure 5, the track can be positively scanned by the magnetic head exclusive for reproducing.
Claims (3)
1. A rotary head type magnetic recording and reproducing device in which a rotatively driven drum is provided with a first pair of magnetic heads arranged at an angle of 1800, a second pair of magnetic heads deviated in phase angle in a rotating direction from the first pair of magnetic heads and each magnetic head in said second pair of magnetic heads being arranged at an angle of 1800 from each other, the first pair of magnetic heads being exclusively for recording and the second pair of magnetic heads being exclusively for reproducing, and a winding angle of a magnetic tape in contact with the drum subtending at the centre of the drum less than said phase angle, wherein said pair of magnetic heads exclusively for reproducing have a gap length,: :in a direction perpendicularly intersecting a scanning direction thereof # which is longer than that of said magnetic heads exclusively for recording.
2. A rotary head type magnetic recording and reproducing device according to Claim 1, wherein a signal to the magnetic heads exclusive for recording and a signal from the magnetic heads exclusive for reproducing pass through a common circuit for comparison.
3. A rotary head type recording and reproducing device as claimed in Claim 1 and substantially as hereinbefore described with reference to, and as illustrated by, Figures 1 to 7 of the accompanying drawings.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP63319248A JP2589168B2 (en) | 1988-12-17 | 1988-12-17 | Rotating head type magnetic recording / reproducing device |
| GB8926095A GB2226180A (en) | 1988-12-17 | 1989-11-17 | Rotary head magnetic recording and reproducing apparatus |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB9307395D0 GB9307395D0 (en) | 1993-06-02 |
| GB2266001A true GB2266001A (en) | 1993-10-13 |
| GB2266001B GB2266001B (en) | 1994-02-09 |
Family
ID=26296223
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB9307395A Expired - Fee Related GB2266001B (en) | 1988-12-17 | 1993-04-08 | Rotary head magnetic recording and reproducing system |
Country Status (1)
| Country | Link |
|---|---|
| GB (1) | GB2266001B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9153246B1 (en) | 2014-09-25 | 2015-10-06 | International Business Machines Corporation | Magnetic tape rewind overwrite data protection |
-
1993
- 1993-04-08 GB GB9307395A patent/GB2266001B/en not_active Expired - Fee Related
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9153246B1 (en) | 2014-09-25 | 2015-10-06 | International Business Machines Corporation | Magnetic tape rewind overwrite data protection |
| US9520145B2 (en) | 2014-09-25 | 2016-12-13 | International Business Machines Corporation | Magnetic tape rewind overwrite data protection |
Also Published As
| Publication number | Publication date |
|---|---|
| GB2266001B (en) | 1994-02-09 |
| GB9307395D0 (en) | 1993-06-02 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19941117 |