GB2064830A - Transducer head tracking in prerecorded medium replay unit - Google Patents
Transducer head tracking in prerecorded medium replay unit Download PDFInfo
- Publication number
- GB2064830A GB2064830A GB8037680A GB8037680A GB2064830A GB 2064830 A GB2064830 A GB 2064830A GB 8037680 A GB8037680 A GB 8037680A GB 8037680 A GB8037680 A GB 8037680A GB 2064830 A GB2064830 A GB 2064830A
- Authority
- GB
- United Kingdom
- Prior art keywords
- information
- head
- error signal
- phase difference
- prerecorded medium
- 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.)
- Withdrawn
Links
Classifications
-
- G—PHYSICS
- G11—INFORMATION STORAGE
- G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
- G11B15/00—Driving, starting or stopping record carriers of filamentary or web form; Driving both such record carriers and heads; Guiding such record carriers or containers therefor; Control thereof; Control of operating function
- G11B15/18—Driving; Starting; Stopping; Arrangements for control or regulation thereof
- G11B15/46—Controlling, regulating, or indicating speed
- G11B15/467—Controlling, regulating, or indicating speed in arrangements for recording or reproducing wherein both record carriers and heads are driven
- G11B15/4673—Controlling, regulating, or indicating speed in arrangements for recording or reproducing wherein both record carriers and heads are driven by controlling the speed of the tape while the head is rotating
- G11B15/4675—Controlling, regulating, or indicating speed in arrangements for recording or reproducing wherein both record carriers and heads are driven by controlling the speed of the tape while the head is rotating with provision for information tracking
- G11B15/4676—Controlling, regulating, or indicating speed in arrangements for recording or reproducing wherein both record carriers and heads are driven by controlling the speed of the tape while the head is rotating with provision for information tracking using signals recorded in tracks disposed in parallel with the scanning direction
-
- 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
- G11B5/58—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 provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
- G11B5/584—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 provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on tapes
- G11B5/588—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 provision for moving the head for the purpose of maintaining alignment of the head relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following for track following on tapes by controlling the position of the rotating heads
Landscapes
- Adjustment Of The Magnetic Head Position Track Following On Tapes (AREA)
Abstract
Transducer head tracking is provided in a replay unit (12) relative to a prerecorded medium (10) having at least one track which includes simultaneously occuring information disposed thereon forming a chevron pattern. Separate transducers (16, 18) are disposed within the head (14) for concurrently reproducing the simultaneous information when the head is properly aligned with the track of the prerecorded medium. An error signal is derived in proportion to the phase difference (Y-Z) existing between the reproducing of the simultaneous information form each side of the chevron pattern when the head is misaligned. The error signal is then applied to reduce the existing phase difference and any head misalignment therewith. The phase error signal is produced by comparison of a delayed pulse (triggered by one head) with a ramp signal (triggered by the other), and correction may be by movement of the head or adjustment of the speed of the medium (for cross-tracks on the medium as in helical scan recorders). <IMAGE>
Description
SPECIFICATION
Transducer head tracking in prerecorded medium replay unit
This invention relates to both a method and apparatus for aligning a transducer head relative to a prerecorded medium within a replay unit, particularly in replay units where such alignment is required continuously along relatively long tracks. An important design consideration in any information recording and replay system is that the recorded medium must be interchangeably replayed by any replay units manufactured for the system. In many systems such as those using magnetic tape as the recorded medium, tracks of information are very closely spaced on the recorded medium. Consequently, problems are generally encountered with the design of the replay units for such systems because precise tracking of the prerecorded information by a transducer head is difficult to maintain.Head mistracking in such replay units is generally attributed to mechanical tolerances, temperature changes, hygroscopic expansion of the prerecorded medium and other phenomena. Furthermore, such tracking problems become more severe as the width of the information tracks on the prerecorded medium is narrowed, which is the trend in the art of recording digital information. Various head tracking techniques have been utilized in the prior art, with the most popular being the dither technique. In this technique oscillatory motion is imparted to the transducer head and introduces deviations in the signal envelope of the replayed information to thereby produce an amplitude modulated signal which is demodulated to provide the head tracking signal.All of these prior art head tracking techniques become less feasible as the width of the information tracks is narrowed; for the dither technique, difficulties arise when the amplitude of the head oscillation causes transducer overlap between adjacent information tracks.
In accordance with the principles of the present invention, transducer head tracking is provided in a replay unit relative to a prerecorded medium having at least one track which includes simultaneously occurring information disposed thereon in a chevron pattern. In a preferred embodiment, separate transducers are disposed within the head to concurrently reproduce the simultaneous information when the head is properly aligned with the prerecorded medium. An error signal is derived in proportion to the phase difference existing between the reproduction of the simultaneous information from each side of the chevron pattern when the head is misaligned.
The error signal is then applied to reduce the existing phase difference and any head misalignment therewith.
In the Drawings:
Figure 1 illustrates the transducer head alignment concept of the present invention wherein an alignment error signal is derived through separate transducers from simultaneous information in a chevron pattern on at least one track of a prerecorded medium;
Figure 2 illustrates a transducer head misalignment condition for the arrangement of Figure 1;
Figure 3 illustrates one preferred embodiment of the comparator means shown in Figure 1;
Figure 4 illustrates the transducer head alignment concept of the present invention wherein the simultaneous information is derived from adjacent tracks on a prerecorded medium; and
Figures 5 and 6 illustrate other possible embodiments of the invention wherein the separate transducers are spaced apart along the path travelled by the information tracks on the prerecorded medium and the simultaneous information is disposed in an inverted and an offset chevron pattern respectively.
In Figure 1 a portion of a prerecorded medium 10, such as a magnetic tape, is shown disposed within a replay unit 12 of an information recording and replay system. Only a replay transducer head 14 and the apparatus of this invention are shown within the replay unit 12, however, the replay unit 12 would also include a tape drive arrangement (not shown) and could include a head drive arrangement (not shown) in a longitudinal, quadruplex or helical scan tape recording and replay system. As indicated by an arrow, the recorded medium moves relative to the head 14 and it is prerecorded with at least one path that includes simultaneous information in a chevron pattern. The chevron pattern path can be formed by adjacent tracks of the conventional aximuth recording format, or can be formed on a single track.At least two transducers 16 and 18 are disposed within the head 14to concurrently reproduce the simultaneous information from each side of the chevron pattern when the head 14 is properly aligned relative to the prerecorded medium 10 within the replay unit 12. The simultaneous information is applied independently by the transducers 16 and 18 to a comparator means 20 for deriving an alignment error signal in proportion to any phase difference existing between the reproduction of the simultaneous information from each side of the chevron pattern. An alignment correction means 22 for applying the error signal to reduce that phase difference is disposed cooperative arrangement with the comparator means 20.
In Figure 2 the head 14 is shown to be misaligned or mistracking relative to the prerecorded medium 10 within the replay unit 12 so that the simultaneous information from each side of the chevron pattern is not received concurrently by the transducers 16 and 18. The transducers 16 and 18 are individually oriented to pick up the simultaneous information from one side of the chevron pattern and only respond to the simultaneous information on their side, as is known by those skilled in the art. A phase difference between the arrival of the simultaneous information at the separate transducers 16 and 18 is caused by the misalignment. This is illustrated in
Figure 2 by the output pulses from the transducers 16 and 18 which have a phase difference therebetween equal to the time taken for the prerecorded medium 10 to travel relative to the head 14 through a distance of Y-Z.No misalignment between the prerecoded medium 10 and the head 14 exists in
Figure 1 because the distance Y is equal to the distance Z. Therefore no error signal passes from the comparator means 20 to the correction means 22.
For the misalignment between the prerecorded medium 10 and the head 14 that is shown in Figure 2 however, an error signal proportional to the distance
Y-Z passes from the comparator means 20 to the correction means 22. Consequently, the magnitude of the error signal is only dependent on the phase difference existing between the arrival of the simultaneous information at the separate transducers 16 and 18. Therefore the amplitude characteristic of the simultaneous information in unimportant.
Although many embodiments of the comparator means 20 are possible, one preferred embodiment thereof is illustrated in Figure 3. The output pulses shown in Figure 2 being derived from the simultaneous information through transducer 16 are applied to a means 24 for generating a RAMP signal in response thereto, while those output pulses being derived from the simultaneous information through transducer 18 are applied to a means 26 for generating a delayed pulse in response thereto. The outputs from the RAMP generating means 24 and the delay pulse generating means 26 are applied to a means 28 for generating the alignment error signal in proportion to the level of the RAMP signal when the delayed pulse occurs.Output from the error signal generating means 28 is applied to the correction means 22 and it may be proportional to either a leading or lagging phase difference in the output pulses from transducer 18 relative to the output pulses from transducer 16. This is so because the time duration of the delay pulse generating means 26 is fixed to assure that the output therefrom will lag the output from the RAMP generating means 24 when the maximum misalignment condition exists in the direction which causes the output pulses from transducer 18 to lead the output pulses from transducer 16. Therefore, output from the RAMP generating means 24 is always applied to the error signal generating means 28 in advance of the output from the delay pulse generating means 26.When the head 14 is properly aligned with the prerecorded medium 10 in the manner shown by Figure 1, the comparator means 20 produces a zero level error signal in response to the RAMP signal level obtained. Furthermore, error signals of opposite polarity are produced by the comparator means 20 for the conditions of misalignment wherein the output pulses from transducer 18 lead and lag the output pulses from transducer 16, respectively.
The nature of the correction means 22 will depend on the type of recording and replay system in which the replay unit 12 is utilized, but it is generally a servo means of a conventional type to those skilled in the art. In systems where information tracks are scanned substantially longitudinally along the direction in which the prerecorded medium 10 travels, the servo means could function to position the head 14 relative to the longitudinal direction of the tracks.
Such a servo means could include a piezoelectric ceramic bender element to which the head 14 would be mounted. In systems where information tracks are scanned helically across the direction in which the prerecorded medium 10 travels, the servo means could function to adjust the relative velocity between the head 14 and the recorded medium 10. Such a servo means could include a capstan motor to which the error signal is applied to control its speed.
The chevron pattern path of the simultaneous information can be disposed in adjacent tracks as shown in Figure 4 where each track contains separate information that is recorded in the conventional azimuth format. Video information is often recorded in this format with its horizontal sync portions disposed at concurrent locations along each track.
With such video information, the alignment error signal may be derived by the comparator means 20 in proportion to the phase difference existing between concurrent horizontal sync portions of the video information on the adjacent tracks. Furthermore, digital information could also be recorded in this format with its word sync portions disposed at concurrent locations along each track and the alignment error signal would be derived from the word sync portions in the same manner as previously described for the horizontal sync portions of the video information.
Those skilled in the art will realize that many variations from the previously discussed embodiments are possible within the scope of this invention. As shown in Figure 5, the transducers 16 and 18 can be disposed at separate locations along the path of the tracks to concurrently pickup the simultaneous information from each side of the chevron pattern and the direction of the chevron pattern is unimportant. Also, the chevron pattern can be offset as shown in Figure 6.
Furthermore, it should be noted that where necessary the transducers 16 and 18 could be disposed in the head 14 at separate locations along the path of the tracks to receive the simultaneous information noncurrentlyfrom each side of the chevron pattern.
When the simultaneous information is received nonconcurrently by the transducers 16 and 18, a conventional delay (not shown) would be disposed between the comparator means 20 and the transducer receiving the leading information (transducer 16 in Figure 6), to render the simultaneous information concurrent. This delay could be variable with the speed of either the recorded medium 10 orthe transducer head 14, so that the head tracking of the invention would be accomplished while these items are being brought up to speed when the replay unit 12 is initially turned on.
Claims (9)
1. Apparatus for aligning a transducer head relative to a prerecorded medium within a replay unit when at least one track including simultaneous information in a chevron pattern is disposed on the prerecorded medium, said apparatus comprising:
separate transducers disposed in the head for concurrently reproducing said simultaneous information from each side of the chevron pattern when the head is properly aligned with the prerecorded medium;
comparator means for deriving an alignment error signal in proportion to any phase difference existing between the reproduction of said simultaneous information from each side of said chevron pattern; and
alignment correction means for applying said error signal to reduce said phase difference.
2. The apparatus of Claim 1 wherein said comparator means includes:
means for generating a RAMP signal in response to the simultaneous information reproduced through one of said transducers;
means for generating a delayed pulse in response to the simultaneous information reproduced through another of said transducers; and
means for generating said error signal in proportion to the level of said RAMP signal when said delayed pulse occurs.
3. The apparatus of Claim 1 wherein said correction means includes servo means for positioning the transducer head relative to the longitudinal direction of the tracks on the prerecorded medium.
4. The apparatus of Claim 1 wherein said correction means includes servo means for adjusting the relative velocity between the transducer head and the prerecorded medium.
5. In an information replay unit of the type wherein the information is reproduced from a prerecorded medium having adjacent tracks which include simultaneous information recorded in azimuth format and wherein separate transducers are disposed within a head for reproducing the information from the adjacent tracks:
comparator means for deriving a head alignment error signal in proportion to any phase difference existing between the reproduction of the simultaneous information from the adjacent tracks; and
alignment correction means for applying said error signal to reduce said phase difference.
6. The information replay unit of Claim 5 wherein video information is reproduced from the adjacent tracks and wherein said comparator means derives said error signal in proportion to the phase difference existing between simultaneously occurring horizontal sync portions of the video information on the adjacent tracks.
7. The information replay unit of Claim 5 wherein digital information is reproduced from the adjacent tracks and wherein said comparator means derives said error signal in proportion to the phase difference existing between simultaneously occurring word sync portions of the digital information on the adjacent tracks.
8. A method for aligning a transducer head relative to a prerecorded medium within a replay unit when at least one track including simultaneous information recorded in a chevron pattern is disposed on the prerecorded medium, the method comprising:
arranging separate transducers in the head for concurrently reproducing the simultaneous information from each side of the chevron pattern when the head is properly aligned with the prerecorded medium;
deriving an alignment error signal in proportion to any phase difference existing between the reproduction of the simultaneous information from each side of the chevron pattern; and
applying said error signal to reduce said phase difference.
9. Transducer head aligning apparatus substantially as hereinbefore described with reference to the accompanying drawings.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US9835879A | 1979-11-28 | 1979-11-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| GB2064830A true GB2064830A (en) | 1981-06-17 |
Family
ID=22268929
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8037680A Withdrawn GB2064830A (en) | 1979-11-28 | 1980-11-25 | Transducer head tracking in prerecorded medium replay unit |
Country Status (4)
| Country | Link |
|---|---|
| JP (1) | JPS5690420A (en) |
| DE (1) | DE3044524A1 (en) |
| FR (1) | FR2476361A1 (en) |
| GB (1) | GB2064830A (en) |
Cited By (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0054419A2 (en) * | 1980-12-13 | 1982-06-23 | Sony Corporation | Tracking control arrangement in a magnetic recording and reproducing device |
| EP0103463A2 (en) * | 1982-09-15 | 1984-03-21 | Ampex Corporation | Apparatus and method for positioning subsequent recordings on a video tape relative to an existing recording |
| WO1986000163A1 (en) * | 1984-06-07 | 1986-01-03 | Deutsche Thomson-Brandt Gmbh | Magnetic tape apparatus |
| US4720754A (en) * | 1983-12-08 | 1988-01-19 | Fujitsu Limited | Digitally responsive system for positioning a transducer of a storage apparatus |
| EP0285365A2 (en) * | 1987-03-31 | 1988-10-05 | Matsushita Electric Industrial Co., Ltd. | Tracking error signal producing apparatus |
| US5055951A (en) * | 1989-03-10 | 1991-10-08 | Irwin Magnetic Systems, Inc. | Method and apparatus for servo-positioning movable transducer heads |
| US5083227A (en) * | 1989-02-13 | 1992-01-21 | U.S. Philips Corporation | Arrangement for reproducing an electric signal |
| US5132861A (en) * | 1989-10-02 | 1992-07-21 | Behr Michael I | Systems using superimposed, orthogonal buried servo signals |
| US5223994A (en) * | 1989-10-02 | 1993-06-29 | Behr Michael I | System using superimposed, orthogonal buried servo signals |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60133524A (en) * | 1983-12-21 | 1985-07-16 | Yokogawa Hokushin Electric Corp | Magnetic disc storage device |
-
1980
- 1980-11-25 GB GB8037680A patent/GB2064830A/en not_active Withdrawn
- 1980-11-26 DE DE19803044524 patent/DE3044524A1/en not_active Withdrawn
- 1980-11-27 FR FR8025176A patent/FR2476361A1/en not_active Withdrawn
- 1980-11-28 JP JP16901880A patent/JPS5690420A/en active Pending
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0054419A3 (en) * | 1980-12-13 | 1983-01-26 | Sony Corporation | Tracking control arrangements for magnetic recording and reproducing devices |
| EP0054419A2 (en) * | 1980-12-13 | 1982-06-23 | Sony Corporation | Tracking control arrangement in a magnetic recording and reproducing device |
| EP0103463A2 (en) * | 1982-09-15 | 1984-03-21 | Ampex Corporation | Apparatus and method for positioning subsequent recordings on a video tape relative to an existing recording |
| EP0103463A3 (en) * | 1982-09-15 | 1986-11-20 | Ampex Corporation | A new auto tracking method |
| US4689706A (en) * | 1982-09-15 | 1987-08-25 | Ampex Corporation | Apparatus and method for adjusting the respective positions of a magnetic head and video information along a magnetic track |
| US4720754A (en) * | 1983-12-08 | 1988-01-19 | Fujitsu Limited | Digitally responsive system for positioning a transducer of a storage apparatus |
| WO1986000163A1 (en) * | 1984-06-07 | 1986-01-03 | Deutsche Thomson-Brandt Gmbh | Magnetic tape apparatus |
| EP0285365A2 (en) * | 1987-03-31 | 1988-10-05 | Matsushita Electric Industrial Co., Ltd. | Tracking error signal producing apparatus |
| EP0285365A3 (en) * | 1987-03-31 | 1990-11-14 | Matsushita Electric Industrial Co., Ltd. | Tracking error signal forming circuit |
| US5083227A (en) * | 1989-02-13 | 1992-01-21 | U.S. Philips Corporation | Arrangement for reproducing an electric signal |
| US5055951A (en) * | 1989-03-10 | 1991-10-08 | Irwin Magnetic Systems, Inc. | Method and apparatus for servo-positioning movable transducer heads |
| US5132861A (en) * | 1989-10-02 | 1992-07-21 | Behr Michael I | Systems using superimposed, orthogonal buried servo signals |
| US5223994A (en) * | 1989-10-02 | 1993-06-29 | Behr Michael I | System using superimposed, orthogonal buried servo signals |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3044524A1 (en) | 1981-08-27 |
| JPS5690420A (en) | 1981-07-22 |
| FR2476361A1 (en) | 1981-08-21 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| WAP | Application withdrawn, taken to be withdrawn or refused ** after publication under section 16(1) |