US20040109256A1 - Magnetic recording/reproducing apparatus - Google Patents

Magnetic recording/reproducing apparatus Download PDF

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Publication number
US20040109256A1
US20040109256A1 US10/476,192 US47619203A US2004109256A1 US 20040109256 A1 US20040109256 A1 US 20040109256A1 US 47619203 A US47619203 A US 47619203A US 2004109256 A1 US2004109256 A1 US 2004109256A1
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United States
Prior art keywords
recording
time difference
heads
reproduced
signal
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Abandoned
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US10/476,192
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English (en)
Inventor
Kenichi Honjo
Yoshikazu Kato
Haruo Isaka
Toshiyuki Kori
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Panasonic Holdings Corp
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Individual
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Assigned to MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD. reassignment MATSUSHITA ELECTRIC INDUSTRIAL CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: KORI, TOSHIYUKI, ISAKA, HARUO, KATO, YOSHIKAZU, HONJO, KENICHI
Publication of US20040109256A1 publication Critical patent/US20040109256A1/en
Priority to US11/268,783 priority Critical patent/US7130147B2/en
Abandoned legal-status Critical Current

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    • 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
    • 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
    • G11B15/02—Control of operating function, e.g. switching from recording to reproducing
    • G11B15/12—Masking of heads; circuits for Selecting or switching of heads between operative and inoperative functions or between different operative functions or for selection between operative heads; Masking of beams, e.g. of light beams
    • 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
    • G11B5/008—Recording on, or reproducing or erasing from, magnetic tapes, sheets, e.g. cards, or wires
    • G11B5/00813—Recording on, or reproducing or erasing from, magnetic tapes, sheets, e.g. cards, or wires magnetic tapes
    • G11B5/00817—Recording on, or reproducing or erasing from, magnetic tapes, sheets, e.g. cards, or wires magnetic tapes on longitudinal tracks only, e.g. for serpentine format recording
    • G11B5/00839—Recording on, or reproducing or erasing from, magnetic tapes, sheets, e.g. cards, or wires magnetic tapes on longitudinal tracks only, e.g. for serpentine format recording using cyclically driven heads providing segmented tracks
    • 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
    • G11B5/592—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 using bimorph elements supporting the heads
    • G11B5/5921—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 using bimorph elements supporting the heads using auxiliary signals, e.g. pilot signals
    • G11B5/5926—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 using bimorph elements supporting the heads using auxiliary signals, e.g. pilot signals recorded in separate tracks, e.g. servo tracks
    • G11B5/5927—Helicoidal tracks

Definitions

  • the present invention relates to a magnetic recording/reproducing apparatus for recording and reproducing data signals with a rotary magnetic head to form a track oblique to a longitudinal direction of a magnetic tape.
  • a helical-scan recording method is employed using a rotary magnetic head (hereinafter referred to as “head”).
  • the data signals are divided and recorded on a group of sequential unconnected slant tracks that are oblique to a longitudinal direction of the magnetic tape.
  • a tracking control is performed to keep the head to follow the tracks during reproduction of the recorded data signals.
  • Conventional tracking control techniques using a control data obtained from a rotary head include, for instance, an ATF control method disclosed in the Television Technology, September 1985 edition, page 25-27, and a timing control method disclosed in Japanese Patent Laid-Open Publication No.07-29256, page 3.
  • ATF control method a pilot signal is recorded either in a burst-like manner on a part of a track, or superposed on a data signal, and this pilot signal is used to perform the tracking control at the time of reproduction.
  • the tracking control is performed using a tracking error data detected from a time difference between a rotation phase signal of a rotary drum (hereinafter referred to as “PG signal”) and a timing signal (hereinafter referred to in this invention as “synchronizing signal”) recorded on a track.
  • PG signal a rotation phase signal of a rotary drum
  • synchronizing signal a timing signal recorded on a track.
  • the data becomes redundantly long because it needs to record the pilot signal beside a data signal, and it makes worse the tracking accuracy due to residual pilot signal not completely erased on the track base when another data signal is overwritten.
  • a difference in timing from a PG signal to a synchronizing signal recorded on a track is likely to receive an influence of irregular rotation of the rotary drum, vibration of the magnetic tape (hereinafter referred to as “jitter” of the rotary drum) and so forth, that also make worse the tracking accuracy.
  • a magnetic recording and reproducing apparatus includes a rotary drum including first and second heads having azimuth angles different from each other and arranged along a periphery of the rotary drum, for recording data in a track oblique to a longitudinal direction of a magnetic tape, and for reproducing the data on the track, a sync-signal generator for generating a recording synchronizing signal to be recorded on the magnetic tape, and for outputting the recording synchronizing signal to the first and second heads, a sync-signal time difference detector for detecting a time difference between reproduced synchronizing signals reproduced from the magnetic tape and output from the first and second heads, respectively, and a capstan-motor controller for controlling rotation of a capstan motor advancing the magnetic tape based on the time difference output from the sync-signal time difference detector.
  • the sync-signal generator outputs the recording synchronizing signal to the first and second heads substantially simultaneously.
  • the magnetic recording/reproducing apparatus detects an accurate tracking error data not influenced easily by jitter and off-centered shaft of the rotary drum, and realizes highly accurate tracking by using this tracking error data.
  • FIG. 1 is a block diagram of a magnetic recording/reproducing apparatus according to a first exemplary embodiment of the present invention.
  • FIG. 2 is a diagrammatic illustration showing a principle of detecting a time difference of synchronizing signals in the magnetic recording/reproducing apparatus according to the first exemplary embodiment.
  • FIG. 3 is a diagrammatic illustration used to explain operation of detecting the time difference of synchronizing signals in the magnetic recording/reproducing apparatus according to the first exemplary embodiment.
  • FIG. 4 is a block diagram of a magnetic recording/reproducing apparatus according to a second exemplary embodiment of the present invention.
  • FIG. 5A and FIG. 5B are diagrammatic illustrations used to explain operation of detecting a time difference of synchronizing signals in the magnetic recording/reproducing apparatus according to the second exemplary embodiment.
  • FIG. 6 is a diagrammatic illustration used to explain operation of detecting a time difference of synchronizing signals in a disrupted synchronizing pattern in the magnetic recording/reproducing apparatus according to the second exemplary embodiment.
  • FIG. 7 is a diagrammatic illustration used to explain operation of detecting a reproduced synchronizing signal in the magnetic recording/reproducing apparatus according to the second exemplary embodiment.
  • FIG. 8 is a block diagram of a magnetic recording/reproducing apparatus according to a third exemplary embodiment of the present invention.
  • FIG. 9 is a pattern illustration showing a relation of phases of heads to tracks during normal reproduction in the magnetic recording/reproducing apparatus according to the third the exemplary embodiment.
  • FIG. 10 is a diagrammatic illustration used to explain operation of detecting a tracking position in the magnetic recording/reproducing apparatus according to the third exemplary embodiment.
  • FIG. 11 is a diagrammatic drawing for explaining operation of detecting a tracking position based on an enveloped level in the magnetic recording/reproducing apparatus according to the third exemplary embodiment.
  • FIG. 12 is a block diagram of a magnetic recording/reproducing apparatus according to a fourth exemplary embodiment.
  • FIG. 13 is a diagrammatic drawing for explaining execution of off-track operation in the magnetic recording/reproducing apparatus according to the fourth exemplary embodiment.
  • FIG. 14 is a diagrammatic illustration for explaining operation of detecting a target tracking time difference in the magnetic recording/reproducing apparatus according to the fourth exemplary embodiment.
  • FIG. 15 is a block diagram of a magnetic recording/reproducing apparatus according to a fifth exemplary embodiment of the present invention.
  • FIG. 16 is a block diagram of an initial tracking time difference detector of the magnetic recording/reproducing apparatus according to the fifth exemplary embodiment.
  • FIG. 17 is a diagrammatic illustration for explaining an operation of the magnetic recording/reproducing apparatus according to the fifth exemplary embodiment.
  • FIG. 18 is a block diagram of another initial tracking time difference detector of the magnetic recording/reproducing apparatus according to the fifth exemplary embodiment.
  • FIG. 19 is a diagrammatic illustration used to explain an operation of the magnetic recording/reproducing apparatus according to the fifth exemplary embodiment.
  • FIG. 20 is a block diagram of a magnetic recording/reproducing apparatus according to a sixth exemplary embodiment of the present invention.
  • FIG. 21 is a block diagram of a magnetic recording/reproducing apparatus according to a seventh exemplary embodiment of the present invention.
  • FIG. 22 is a diagrammatic drawing used to explain an operation of the magnetic recording/reproducing apparatus according to the seventh exemplary embodiment.
  • FIG. 23 is a diagrammatic illustration used to explain an operation of correcting a record timing of synchronizing signal for a splice recording in the magnetic recording/reproducing apparatus according to the seventh exemplary embodiment.
  • FIG. 24 is a diagrammatic drawing showing track patterns in the splice recording in the magnetic recording/reproducing apparatus according to the seventh exemplary embodiment.
  • FIG. 25 shows relational equations of individual parameters used to explain the magnetic recording/reproducing apparatus of the seventh exemplary embodiment.
  • FIG. 1 is a block diagram of a magnetic recording/reproducing apparatus according to a first exemplary embodiment.
  • Sync-signal generator 6 outputs a recording synchronizing signal to heads 10 a and 10 c of L-azimuth, and heads 10 b and 10 d of R-azimuth, all mounted to rotary drum 1 , through switches 9 a and 9 b, when a control signal output from recording/reproduction controller 8 is for a recording mode.
  • the prefixed characters of L and R are used solely for the purpose of distinguishing a direction of azimuth.
  • the azimuth angle is an angle formed by a head gap with respect to a widthwise direction of head core.
  • L-ch sync-signal detector 11 detects a synchronizing signal out of reproduction signals recorded on magnetic tape 3 , reproduced by L-azimuth heads 10 a and 10 c, and delivered through switch 9 a.
  • R-ch sync-signal detector 12 detects a synchronizing signal out of reproduction signals recorded on magnetic tape 3 , reproduced by R-azimuth heads 10 b and 10 d, and delivered through switch 9 b.
  • Sync-signal time difference detector 7 measures a time difference between an L-ch reproduced synchronizing signal output by L-ch sync-signal detector 11 and an R-ch reproduced synchronizing signal output by R-ch sync-signal detector 12 , and detects an error from a target value.
  • Capstan controller 5 advances magnetic tape 3 at a predetermined speed based on a frequency signal in synchronism with rotation of capstan motor 2 output by FG detector 4 , and carries out tracking control by adjusting the speed on the basis of an error signal for the synchronizing signal time difference output by sync-signal time difference detector 7 .
  • FIG. 2 shows an operating principle of detecting the synchronizing signal time difference.
  • synchronizing signals of L-azimuth and R-azimuth are recorded in an equal height in the vertical direction
  • head L of L-azimuth and head R of R-azimuth are mounted at an equal height in the vertical direction with respect to the tracks.
  • the head L and the head R for scanning these tracks in the vertical direction are off the tracks horizontally by a distance ⁇ A from their ideal positions in the reproducing operation.
  • Synchronizing signal time difference Ta representing a tracking error data in this condition can be expressed by the equation
  • Ta 2 ⁇ A ⁇ (tan ⁇ )/ V 1
  • ⁇ is an azimuth angle
  • V1 denotes a relative speed of the heads to the tracks.
  • FIG. 3 is a diagrammatic illustration used to explain an operation of detecting a time difference of synchronizing signals in the magnetic recording/reproducing apparatus of this exemplary embodiment. It shows an example of reproducing a synchronizing signal of L-azimuth and another synchronizing signal of R-azimuth recorded on the tracks by head L 1 ( 10 a ) of L-azimuth and head R 1 ( 10 b ) of R-azimuth respectively.
  • head L 1 ( 10 a ) and head R 1 ( 10 b ) are arranged with a distance equal to one synchronizing signal length in the vertical direction, and the both heads reproduce their respective synchronizing signals in the same timing.
  • a synchronizing signal time difference is detected as an error signal of positive side, as in the case of FIG. 2, and if the phase of magnetic tape 3 delays, the synchronizing signal time difference is detected as an error signal of negative side.
  • Capstan controller 5 performs the tracking control based on these error signals of synchronizing signal time difference.
  • Use of the head of L-azimuth and the head of R-azimuth to record simultaneously the respective synchronizing signals can thus prevent an error in the recording positions that is liable to occur between the synchronizing signal of L-azimuth and the synchronizing signal of R-azimuth due to jitter and off-centered shaft of the rotary drum.
  • detecting the synchronizing signals reproduced by the head of L-azimuth and the head of R-azimuth at generally the same time during the reproducing operation can also reduce substantially an adverse effect of the jitter and off-centered shaft of the rotary drum produced in detecting the individual synchronizing signals.
  • the above sync-signal generator composes “n” number of synchronizing blocks (“n” represents an integer of 1 or larger) in each track, and outputs a recording synchronizing signal for each synchronizing block.
  • n represents an integer of 1 or larger
  • Each pair of heads 10 a and 10 b, and 10 c and 10 d are arranged individually on the rotary drum with a mutual distance generally equal to an integral multiple of a length of the synchronizing block over the track on the magnetic tape.
  • the magnetic recording/reproducing apparatus of this invention can detect reproduced synchronizing signals of the individual heads at the time.
  • the structure can therefore ensure a sufficient space between heads 10 a and 10 b as well as between heads 10 c and 10 d, thereby making it possible to detect a tracking error data with scarcely an influence of jitter and of off-centered shaft of the rotary drum even though the heads are not mounted close to one another.
  • the present invention has a remarkable advantage in the practical use especially for the latest magnetic recording/reproducing apparatuses that are equipped with small rotary drums having several tens of millimeters in diameters.
  • FIG. 4 is a block diagram of a magnetic recording/reproducing apparatus of the second exemplary embodiment.
  • L-ch reproduction PLL circuit 13 generates clocks in synchronism with reproduced signals of heads 10 a and 10 c output through switch 9 a, when a control signal output by recording/reproduction controller 8 is in a reproduction mode.
  • R-ch reproduction PLL circuit 14 generates clocks in synchronism with reproduced signals of heads 10 b and 10 d output through switch 9 b.
  • L-ch delay circuit 15 delays an L-ch reproduced synchronizing signal output by L-ch sync-signal detector 11 for a predetermined time using L-ch reproduction clocks output by L-ch reproduction PLL circuit 13 .
  • R-ch delay circuit 16 delays an R-ch reproduced synchronizing signal output by R-ch sync-signal detector 12 for a predetermined time using R-ch reproduction clocks output by R-ch reproduction PLL circuit 14 .
  • Sync-signal time difference detector 70 receives inputs of the L-ch reproduced synchronizing signal output by L-ch sync-signal detector 11 , an L-ch reproduced pseudo-synchronizing signal output by delay circuit 15 , the R-ch reproduced synchronizing signal output by R-ch sync-signal detector 12 , and an R-ch reproduced pseudo-synchronizing signal output by R-ch delay circuit 16 . It then measures a time difference between any of the L-ch reproduced synchronizing signal and the L-ch reproduced pseudo-synchronizing signal and any of the R-ch reproduced synchronizing signal and the R-ch reproduced pseudo-synchronizing signal, and detects an error from a target value.
  • FIG. 5A and FIG. 5B are diagrammatic illustrations showing an operation of detecting a time difference of synchronizing signals in the case head L 1 ( 10 a ) and head R 1 ( 10 b ) are arranged in positions where a distance between them is not equal to an integral multiple of a length of synchronizing block in a widthwise direction of the tape.
  • sync-signal time difference detector 70 uses the L-ch reproduced synchronizing signal output by L-ch sync-signal detector 11 and the R-ch reproduced pseudo-synchronizing signal output by R-ch delay circuit 16 .
  • the R-ch reproduced pseudo-synchronizing signal is delayed from the R-ch reproduced synchronizing signal output by the R-ch sync-signal detector by a period of time T 0 using R-ch reproduction clocks output by R-ch reproduction PLL circuit 14 .
  • FIG. 5A shows that head R 1 ( 10 b ) is located in a position behind the preceding synchronizing signal by just a period of time T 0 when head L 1 ( 10 a ) reproduces a synchronizing signal.
  • FIG. 5B shows that head R 1 ( 10 b ) is in a position behind the preceding synchronizing signal by just a period of time T 0 when head L 2 ( 10 c ) reproduces another synchronizing signal.
  • sync-signal time difference detector 70 measures a time difference between a reproduced synchronizing signal of head L 1 output by L-ch sync-signal detector 11 and a reproduced pseudo-synchronizing signal of head R 1 output by R-ch delay circuit 16 , and outputs a deviation from the target value as a tracking error data to capstan controller 5 . Also, in the state of FIG. 5A, sync-signal time difference detector 70 measures a time difference between a reproduced synchronizing signal of head L 1 output by L-ch sync-signal detector 11 and a reproduced pseudo-synchronizing signal of head R 1 output by R-ch delay circuit 16 , and outputs a deviation from the target value as a tracking error data to capstan controller 5 . Also, in the state of FIG.
  • sync-signal time difference detector 70 measures a time difference between a reproduced synchronizing signal of head L 2 ( 10 c ) output by L-ch sync-signal detector 11 and a reproduced pseudo-synchronizing signal of head R 1 output by R-ch delay circuit 16 , and outputs a deviation from the target value as another tracking error data to capstan controller 5 .
  • Capstan controller 5 thus carries out tracking control in the same manner as described in the first exemplary embodiment.
  • the apparatus is able to detect a time difference by the first head and the second head disposed with their distance generally not equal to an interval of the recorded positions of the synchronizing signals, with the aid of reproduced pseudo-synchronizing signals, even at different positions from the synchronizing signals recorded at the same time.
  • this structure can further alleviate limitation on the mounting positions of the first head and the second head as compared to the first exemplary embodiment, thereby allowing arrangement of the first head and the second head freely without regard to the integral multiple of the length of the synchronizing blocks. Accordingly, this further increases flexibility of arranging the individual heads to the rotary drum in making the magnetic recording/reproducing apparatus of this invention into practical use.
  • this embodiment uses a time difference of the reproduced synchronizing signals output by the second head and the third head to avoid a problem in which the tracking error data produced from the time difference of the reproduced synchronizing signals output by the first and the second heads may be disrupted in the longitudinal direction of the tracks.
  • an influence of jitter of the rotary drum can be reduced by recording the recording synchronizing signals at the same timing with the first, the second, and the third heads, thereby expanding a detectable range of the tracking error data in the longitudinal direction of the tracks.
  • a structure may be composed in the following manner in the above case to alleviate limitation on the mounting positions of the first head, the second head and the third head.
  • the sync-signal generator composes each track with “n” number of synchronizing blocks (“n” represents an integer of 1 or larger), and outputs a recording synchronizing signal for each synchronizing block.
  • the first head and the second head are arranged on the rotary drum with a mutual distance generally equal to an integral multiple of a length of the synchronizing block over the track on the magnetic tape, and the second head and the third head are also arranged on the same rotary drum with a mutual distance generally equal to an integral multiple of the length of the synchronizing block over the track on the magnetic tape.
  • the sync-signal generator outputs a first recording synchronizing signal to the first head, a second recording synchronizing signal to the second head, and a third recording synchronizing signal to the third head, in a manner that the first recording synchronizing signal is output with a lag of a predetermined time T 2 after the second recording synchronizing signal, and the third recording synchronizing signal is output with another lag of a predetermined time T 3 after the second recording synchronizing signal.
  • the sync-signal time difference detector detects a time difference between a first reproduced pseudo-synchronizing signal, which is produced by delaying a second reproduced synchronizing signal reproduced by the second head by a number of reproduction clocks equivalent to the predetermined time T 2 , and a first reproduced synchronizing signal reproduced by the first head, when the first head is in the reproducing operation.
  • the sync-signal time difference detector also detects another time difference between a second reproduced pseudo-synchronizing signal, which is produced by delaying the second reproduced synchronizing signal reproduced by the second head by a number of reproduction clocks equivalent to the predetermined time T 3 , and a third reproduced synchronizing signal detected by the third head, when the third head is in the reproducing operation.
  • the above operation can record and reproduce the synchronizing signals by correcting variations in the mounting position among the three heads.
  • FIG. 6 is a diagrammatic drawing illustrating an operation, which realizes detection of a time difference of synchronizing signals even when such tracks are reproduced.
  • FIG. 7 is a diagrammatic illustration showing L-ch reproduced synchronizing signals detected when the tracks shown in FIG.
  • head L 1 ( 10 a ) L-ch reproduced pseudo-synchronizing signals produced in L-ch delay circuit 15 by delaying the L-ch reproduced synchronizing signals by a period of time T 1 with L-ch reproduction clocks output by L-ch reproduction PLL circuit 13 , and R-ch reproduced synchronizing signals detected when reproducing by head R 1 ( 10 b ), with the abscissa designating a time sequence.
  • sync-signal time difference detector 70 compares any of the reproduced synchronizing signals from head L 1 ( 10 a ) and the reproduced pseudo-synchronizing signals from head L 1 with the reproduced synchronizing signals from head R 1 ( 10 b ), it compares only those synchronizing signals that lie within a range of ⁇ Tw as marked by arrows shown in FIG. 7 as synchronizing signal time difference detecting points.
  • the apparatus is able to detect a tracking error data by detecting the time differences of any of the reproduced synchronizing signals and the reproduced pseudo-synchronizing signals output by the second head with the reproduced synchronizing signals output by the first head, even in the tracks where the synchronizing signals are not recorded at regular intervals.
  • FIG. 8 is a block diagram showing a structure of a magnetic recording/reproducing apparatus of the third exemplary embodiment. Components of like functions as those of the magnetic recording/reproducing apparatus of the first exemplary embodiment are designated with like reference numerals, and their details will therefore be skipped.
  • a track number data is recorded on each of tracks as a position data for the track, as a single unit, on which each head scans, as will be described later.
  • description is provided hereinafter of a method of detecting a tracking position in order for each head to reproduce data it recorded in the same track by providing another reproduction mode, which transfers a magnetic tape at a different speed than the normal speed.
  • Sync/track number generator 60 outputs a synchronizing signal and a track number data to be recorded to heads 10 a and 10 c through switch 9 a, and also to heads 10 b and 10 d through switch 9 b, when a control signal output by recording/reproduction controller 8 is in a recording mode.
  • Error rate/envelope detector 17 detects any of error rates and envelope levels of signals reproduced by heads 10 a and 10 c through switch 9 a, as well as those of signals reproduced by heads 10 b and 10 d through switch 9 b, when the control signal is for a reproduction mode.
  • Track number detector 18 detects an L-ch reproduced track number reproduced by heads 10 a and 10 c through switch 9 a and an R-ch reproduced track number output by heads 10 b and 10 d through switch 9 b, when the control signal output by record signal controller 8 is in a reproduction mode.
  • Head switching generator 25 generates a head switching signal (HSW_L) for heads 10 a and 10 c and another head switching signal (HSW_R) for heads 10 b and 10 d from a PG signal in synchronism with rotation of rotary drum 1 which is output by PG detector 20 .
  • tracking position detector 19 can detect a position to be tracked based on a synchronizing signal time difference error data output by sync-signal time difference detector 7 , an error rate data or an envelope level data output by error rate/envelope detector 17 , a reproduction track number data output by track number detector 18 , and head switching signals HSW_L and HSW_R output by head switching generator 25 .
  • capstan controller 50 can perform tracking control based on the tracking error data output by tracking position detector 19 .
  • FIG. 9 is a pattern illustration showing a relation of phases of heads to tracks during a reproducing operation at the normal speed.
  • head L 1 and head R 1 record on tracks of even numbers
  • head L 2 and head R 2 record on tracks of odd numbers respectively, assuming that the recording is made consecutively on pairs of tracks beginning with number 0 to number 5, as these pairs are numbered serially from 0, 1, 2, 3, 4, 5, 0 and so on, as depicted in the figure.
  • FIG. 10 represents a case in which advancing speed of magnetic tape 3 is set with capstan controller 50 to ⁇ fraction (10/9) ⁇ (ten-ninth) of the normal speed in the reproducing operation, wherein it shows head switching waveforms (HSW_L and HSW_R) for scanning the individual tracks, track numbers to be reproduced by the individual heads, time difference of reproduced synchronizing signals between head L 1 and head R 1 or between head L 2 and head R 2 , an error rate of a reproduced signal from any of the heads or a mean error rate of reproduced signals from a plurality of the heads, and an envelope detection level of the reproduced signal from any of the heads or a mean envelope detection level of the reproduced signals from the plurality of heads.
  • HSW_L and HSW_R head switching waveforms
  • the following may be cases in the time difference of the reproduced synchronizing signals.
  • the reproduced synchronizing signals have no time difference between them in the on-track condition.
  • the reproduced synchronizing signals have a time difference therebetween in the on-track condition.
  • tracking position detector 19 outputs a time difference of synchronizing signals as a tracking error data shown in FIG. 10, which will be described in detail later.
  • the tracking position is plotted as point ( 1 ) in time difference of the synchronizing signals in FIG. 10.
  • This tracking position can be taken in two ways, i.e. to establish either a midpoint between the maximum value and the minimum value of the time difference of synchronizing signals within a range ( 8 ) shown in FIG. 10, as one method, or a mean value of the time difference of synchronizing signals within the same range, as another method.
  • Both of these methods are useful for detecting a center position from a point where the synchronizing signal begins being reproduced to another point where the synchronizing signal becomes not reproducible. Accordingly, it makes possible to detect a tracking position, which yields a maximum margin from one track to be scanned by a given head to another track of the same azimuth located next to the adjacent track.
  • this tracking position can be given as a point of the lowest error rate output by error rate/envelope detector 17 . Therefore, detection of the error rate may be used together to make correction of errors that results in the time difference of synchronizing signals due to changes in temperature and humidity during recording and reproducing operations.
  • FIG. 11 is a diagrammatic drawing illustrating an operation of detecting the tracking position using a detected level of envelope.
  • FIG. 11A shows an example of detecting output levels reproduced by head L 1 at point A, point B and point C, on an assumption that a scanning locus of the head is curved with respect to the track as shown.
  • An actual waveform of the reproduced output by the head is shown in FIG. 11B.
  • one of the curves in a dotted line indicates a center of the locus where head L 1 scans when a phase of magnetic tape 3 is slightly advanced.
  • FIG. 11B shows an actual waveform of the reproduced envelope when the phase is slightly advanced in the same degree.
  • FIG. 10 for changes of detected levels of the envelopes with respect to time at the point A, point B and point C, it is found that the tracking positions are deviated from points of maximum value in the envelope level at both the point A and the point C, although the tracking position at point B is in line with the point of maximum value in the envelope level. Since the track is deviated in the opposite directions at the point A and the point C, as shown in FIG. 11A, it is known that a point where the envelope levels detected at the point A and the point C balance with each other, that is, the point at which the lowest points (the minimum values) Vb of these envelope levels become equal, as shown in FIG.
  • the tracking position is regarded as the tracking position.
  • detection is made for envelope levels at a plurality of points within a scanning duration of the heads.
  • the tracking position is then determined as a position where the lowest point of the envelope level becomes the largest.
  • a synchronizing signal time difference in value equivalent to a phase of two tracks is added to the actual synchronizing signal time difference, as shown by line ( 4 ).
  • a synchronizing signal time difference in value equivalent to a phase of two tracks is subtracted from the actual synchronizing signal time difference as shown by line ( 5 ).
  • the last synchronizing signal time difference is held.
  • Broken line ( 2 ) indicates the last synchronizing signal time difference, which is held immediately prior to line ( 4 ) where the synchronizing signal time difference became not reproducible when the tracking position is shifted from line ( 4 ) to line ( 1 ) in the case tracking control is carried out with the normal speed.
  • Broken line ( 7 ) indicates a tracking position when a reproducing operation is carried out with unmatched track number.
  • tracking position detector 29 detects positions of the heads as to which tracks they are scanning, by replaying a tape with its advancing speed faster than the normal speed, and outputs corrected synchronizing signal time difference to capstan controller 50 .
  • tracking control can be carried out in a manner that head L 1 and head R 1 reproduce data they recorded on the same tracks of even number, and head L 2 and head R 2 reproduce data they recorded on the same tracks of odd number, by switching back to the normal speed in the subsequent reproducing operation.
  • the tracking control in this manner in a periodicity of four tracks, individual heads can reproduce the data they recorded on the same tracks.
  • the apparatus can therefore reduce substantially a deviation of time difference of the reproduced synchronizing signals under the on-track condition caused by variations in mounting heights of the individual heads disposed on rotary drum 1 .
  • a process of the tracking control can be simplified when the magnetic tape is started from the standing state and reproduced again at the normal speed, because the tracking positions need not be detected for the second time.
  • this magnetic recording/reproducing apparatus can also detect an accurate tracking error data not liable to the influence of jitter and off-centered shaft of a rotary drum even when the apparatus is provided with reproduction-only heads separate from the recording heads, by arranging a distance between the two reproduction heads for detecting a time difference of the reproduced synchronizing signals into the same distance with the two recording heads for recording the synchronizing signals.
  • FIG. 12 is a block diagram of a magnetic recording/reproducing apparatus according to the fourth exemplary embodiment.
  • a track number data is recorded on each of tracks as a position data for the track, as a single unit, on which each head scans, as will be described later.
  • this exemplary embodiment will disclose a method of detecting a tracking position for use by a head to reproduce data from a track recorded by the head itself, and a time difference of synchronizing signals (hereinafter referred to as “target tracking time difference”) corresponding to an optimum tracking position with high accuracy and in a short time while detecting a condition of reproducing operation, by way of reproducing a magnetic tape at the normal speed, and gradually adding or subtracting an offset value to the time difference of the synchronizing signals being detected. Since this allows detection of an error data on deviation of the time difference of the reproduced synchronizing signals under the on-track condition, caused by variation of mounting height and the like of the individual heads disposed on the rotary drum, the apparatus can detect an optimum tracking position for each track.
  • Recording heads 100 a and 100 c of L-azimuth and recording heads 100 b and 100 d of R-azimuth are mounted on rotary drum 1 , and a mounting angle of head 100 b is A degree (hereinafter referred to as “head-stagger angle A”) with respect to head 100 a.
  • head-stagger angle A A degree
  • head 100 d is also mounted at head-stagger angle A with respect to head 100 c.
  • reproducing heads 101 a and 101 c of L-azimuth and reproducing heads 101 b and 101 d of R-azimuth are also mounted on rotary drum 1 . All the heads are mounted at the same head-stagger angle A.
  • Reproducing head 101 a is arranged to such a head height that it can reproduce data on a track recorded by recording head 100 a at almost the same time
  • reproducing heads 101 b, 101 c and 101 d are also arranged in the like manner to such head heights that they can reproduce data on tracks recorded by recording heads 100 b, 100 c and 100 d respectively at almost the same time.
  • Head switching generator 25 generates a head switching signal (HSW_RL) for recording heads 100 a and 100 c, a head switching signal (HSW_RR) for recording heads 100 b and 100 d, a head switching signal (HSW_PL) for reproducing heads 101 a and 101 c, a head switching signal (HSW_PR) for reproducing heads 101 b and 101 d, by taking a PG signal in synchronism with rotation of rotary drum 1 , output by PG detector 20 .
  • HSW_RL head switching signal
  • HSW_RR head switching signal
  • HW_PL head switching signal
  • HW_PR head switching signal
  • Recording clock generator 102 defining a reference clock (hereinafter referred to as “REFCLK”) is used for generating a recording synchronizing signal, and it includes a quartz oscillator or the like.
  • Recording data generator 150 generates an L-channel recording data in synchronism with the head switching signal HSW_RL, the L-channel recording data including a recording data containing a recording synchronizing signal for heads 100 a and 100 c and track number, and a parity data for detecting an error of the data.
  • Recording clock generator 102 generates R-channel recording data in synchronism with the head switching signal HSW_RR, the R-channel recording data including recording data containing a recording synchronizing signal for heads 100 b and 100 d, and a parity data for detecting an error of the data.
  • L-ch data delay circuit 103 delays the L-channel recording data by a predetermined number of clocks B with a periodicity of RECCLK.
  • R-ch data delay circuit 104 delays the R-channel recording data for a variable period from 0 to (B ⁇ 2) number of clocks with the periodicity of RECCLK. Recording synchronizing signal time differences among individual recording synchronizing signals can be adjusted within a range of ⁇ B to +B by adjusting a delay time of R-ch data delay circuit 103 .
  • Reference recording divergence memory 105 stores the delay time of the R-ch data delay circuit (the delay time for use to record on a tape with a recording synchronizing signal time difference equal to that of the reference tape) individually at both high side and low side of the head switching signal HSW_RR, as a reference recording divergence time, which will be described later (P27, line 13 et seq.).
  • a delayed L-channel recording data output by L-ch data delay circuit 103 is recorded on magnetic tape 3 by recording heads 100 a and 100 c after passed through a recording amplifier (not shown in the figure).
  • a delayed R-channel recording data output by R-ch data delay circuit 104 is recorded on magnetic tape 3 by recording heads 100 b and 100 d after passed through another recording amplifier (not shown in the figure). It is assumed at this time that both heads 100 a and 100 b form tracks of track number 0 , and both heads 100 c and 100 d form tracks of track number 1 for recording the data respectively.
  • head 101 a, head 101 c, head 101 b and head 101 d detect an L-azimuth track of track number 0 , an L-azimuth track of track number 1 , an R-azimuth track of track number 0 and an R-azimuth track of track number 1 respectively among the recording tracks formed on magnetic tape 3 .
  • the detected signals are decoded while being passed through reproduction amplifiers and reproduction equalization circuits (not shown in the figure), and input to L-ch sync-signal detector 11 and R-ch sync-signal detector 12 .
  • L-ch sync-signal detector 11 executes a pattern matching of a synchronizing signal from the L-ch reproduced data obtained from reproducing heads 101 a and 101 c, and outputs an L-ch synchronizing signal pulse which is brought to high-level only by one period of a clock wherefrom the synchronizing signal is detected.
  • R-ch sync-signal detector 12 also executes a pattern matching of a synchronizing signal from the R-ch reproduced data obtained from reproducing heads 101 b and 101 d, and outputs an R-ch synchronizing signal pulse, which is brought to high-level only by one period of a clock wherefrom the synchronizing signal is detected, in the like manner.
  • L-ch clock reproduction circuit 106 reproduces a clock (hereinafter referred to as “CLK_L”) synchronized with the L-ch reproduced data.
  • R-ch clock reproduction circuit 107 reproduces another clock (hereinafter referred to as “CLK_R”) synchronized with the R-ch reproduced data.
  • CLK_L a clock
  • CLK_R another clock
  • Sync-gate generator 113 outputs an exclusive OR of the head switching signals HSW_PL and HSW_PR, in principle, as a synchronizing gate pulse.
  • a synchronizing signal in a high-level area of this pulse is of a combination of reproducing head 101 a and 101 d, or a combination of reproducing head 101 b and 101 c.
  • a time difference obtained in any of these combinations may occasionally diverge significantly from a synchronizing signal time difference obtained from an original combination (a combination of heads 101 a and 101 b, or heads 101 c and 101 d, which are on tracks of the same track number).
  • Any synchronizing signal time difference of significant divergence is removed by any of L-ch sync-signal delay circuits 103 and R-ch sync-signal delay circuits 104 , in order to avoid an erroneous detection.
  • L-ch sync-signal delay circuit 108 delays the L-ch synchronizing signal in a low-level section of the synchronizing gate pulse by a predetermined number of clocks B of a periodicity of CLK_L.
  • R-ch sync-signal delay circuit 109 delays the R-ch synchronizing signal for a variable period from 0 to (B ⁇ 2) number of clocks of a periodicity of CLK_R. Time differences among the individual reproduced synchronizing signals can thus be adjusted within a range of ⁇ B to +B.
  • Reference reproduction divergence memory 110 stores a delay time of the synchronizing signals (i.e. a delay time of reference reproduction divergence, as is discussed later) obtained when a reference tape prepared by another reference apparatus is replayed with the delay time of the R-ch sync-signal delay circuit, in a low-level section of the synchronizing gate pulse.
  • Both of a delayed L-ch synchronizing signal pulse output by L-ch sync-signal delay circuit 108 and a delayed R-ch synchronizing signal pulse output by R-ch sync-signal delay circuit 109 are input to sync-signal time difference detector 7 and sync-signal counter 114 .
  • Sync-signal time difference detector 7 counts a time difference between the delayed L-ch synchronizing signal pulse and the delayed R-ch synchronizing signal pulse on the basis of RECCLK, and outputs a reproduced synchronizing signal time difference as a negative time difference when the delayed R-ch synchronizing signal pulse is in the foreside with respect to the delayed L-ch synchronizing signal pulse, or as a positive time difference when it is in the backside.
  • Sync-signal counter 114 counts a number of the delayed L-ch synchronizing signal pulses within one period of the head switching signal HSW_PL, and outputs it as a number of synchronizing signals in the L-ch head switching period, to circuit operation controller 122 .
  • sync-signal counter 114 counts a number of the delayed R-ch synchronizing signal pulses within one period of the head switching signal HSW_PR, and outputs it to circuit operation controller 122 , as a number of synchronizing signals in the R-ch head switching period.
  • Error rate detector 115 takes the L-ch and R-ch reproduced data as its input, detects an amount of errors in one period of the head switching signal of the recorded data from each of parity data, and outputs to circuit operation controller 122 , as an error rate of the L-ch head switching period and an error rate of the R-ch head switching period.
  • Track number detector 116 takes the L-ch and R-ch reproduced data as an input, detects track numbers corresponding to the synchronizing signal data of individual channels one after another, and outputs them to circuit operation controller 122 as L-ch track numbers and R-ch track numbers.
  • Circuit operation controller 122 controls later described target tracking time difference detector 118 , offset time difference controller 119 and switch 120 individually on the basis of the number of synchronizing signals in the L-ch and R-ch head switching periods, the error rates of the L-ch and R-ch head switching periods, and the L-ch and R-ch track numbers.
  • Switch 120 is initially connected to “a” side by a command of the circuit operation controller, and sends zero (0) output to subtracter 121 .
  • Subtracter 121 thus outputs the synchronizing signal time difference, as it is output by sync-signal time difference detector 7 , and sends it to capstan controller 151 as a synchronizing signal time difference error.
  • Capstan controller 151 forwards magnetic tape 3 at a predetermined speed according to an FG signal output by FG detector 4 in synchronism with rotation of capstan motor 2 .
  • the individual heads thus reproduce data on the tracks numbered with a predetermined relation according to the data from circuit operation controller 122 (the predetermined relation means use of both reproducing head 101 a and 101 to reproduce data on tracks of track number 0 , and both reproducing head 101 c and 101 d to reproduce data on tracks of track number 1 ).
  • Capstan controller 151 executes tracking control by adjusting the speed of magnetic tape 3 in a manner to bring the synchronizing signal time difference error close to zero at all the time.
  • offset time difference controller 119 When switch 120 is connected to the “b” side, offset time difference controller 119 outputs a value produced by addition and/or subtraction of a number, which is gradually increased in a predetermined increment from zero according to a command of circuit operation controller 122 , and causes subtracter 121 to keep providing the synchronizing signal time difference with predetermined values of offset.
  • target tracking time difference detector 118 detects a synchronizing signal time difference when any of the number of synchronizing signals and the error rate changes for the worse during the head switching period, takes the synchronizing signal time difference as a maximum time difference when it is in the positive side of offset, or as a minimum time difference when it is in the negative side of offset, and outputs one-half the sum of these detected values as a target tracking time difference.
  • FIG. 13 is a diagrammatic drawing for use to explain execution of off-track operation.
  • FIG. 13( a ) shows two tracks formed in a vertical direction, on which synchronizing signals of L-azimuth and R-azimuth are recorded in an equal height in the vertical direction, and head L of L-azimuth and head R of R-azimuth mounted in ideally aligned positions on the tracks but with different heights by a distance X with respect to each other in the vertical direction.
  • Slanted dotted lines on the individual tracks indicate patterns of synchronizing signals (i.e. recorded loci).
  • synchronizing signal time difference Tx is detected as X/V1, since the individual heads scan the tracks at a head-to-track relative speed of V1.
  • the system of controllers shown in the previous FIG. 12 controls its operation in a manner to shift the tracking positions off the track centers by a distance ⁇ A (which equals) so that there is no time difference.
  • FIG. 14 is a diagrammatic illustration for explaining operation of detecting a target tracking time difference, wherein mark (a) shows tracking positions of heads on the tracks as they moves with time, mark (b) shows a value of synchronizing signal time difference (i.e. an output of sync-signal time difference detector 7 of FIG. 12) under this tracking condition, and mark (c) is a value of the number of synchronizing signals (i.e. an output of sync-signal counter 114 of FIG. 12) in a head switching period, showing a degree of degradation of the reproducing condition at these points of time.
  • mark (a) shows tracking positions of heads on the tracks as they moves with time
  • mark (b) shows a value of synchronizing signal time difference (i.e. an output of sync-signal time difference detector 7 of FIG. 12) under this tracking condition
  • mark (c) is a value of the number of synchronizing signals (i.e. an output of sync-signal counter 114 of FIG. 12) in a head switching period,
  • Offset time difference controller 119 outputs an offset value by gradually increasing it to the positive side according to a command of circuit operation controller 122 , to provide the synchronizing signal time difference with this offset via subtracter 121 . This causes an output of sync-signal time difference detector 7 in FIG. 12 to shift gradually toward the positive side in a period shown by mark D′ in FIG. 14( b ).
  • the number of synchronizing signals in the head switching period decreases to a level F into a range of detecting the off-track condition.
  • circuit operation controller 122 finds the level F under the condition of positive side offset, it sends the detected result as a flag data (i.e. the level F) to target tracking time difference detector 118 .
  • target tracking time difference detector 118 stores the synchronizing signal time difference of this point of time as a maximum off-track time difference.
  • offset time difference controller 119 Upon completion of detecting the maximum off-track time difference, offset time difference controller 119 outputs another offset value by gradually subtracting it to the negative side based on a command of circuit operation controller 122 , and provides the synchronizing signal time difference with an offset of the reverse side via subtracter 121 . This causes the output of sync-signal time difference detector 7 in FIG. 12 to shift gradually toward the negative side in a period shown by mark E′ in FIG. 14( b ). When the synchronizing signal time difference reaches to the point shown by mark E as the tracking condition shifts to a state of mark C in the figure, the number of synchronizing signals in the head switching period decreases to a level G into a range of detecting the off-track condition.
  • Target tracking time difference detector 118 stores the synchronizing signal time difference of this point of time as a minimum off-track time difference based on this detected flag data.
  • target tracking time difference detector 118 calculates one-half the sum of the maximum off-track time difference and the minimum off-track time difference. The calculated value corresponds to the time Tx in FIG. 13.
  • circuit operation controller 122 turns switch 120 into connection with “c” side to make subtracter 121 subtract the time Tx from the synchronizing signal time difference, thereby realizing the tracking in the ideal on-track position as shown in FIG. 13( a ).
  • a distance of the tracking movement required to detect the target tracking time difference is twice the track pitch or less according to the circuit configuration of this fourth exemplary embodiment.
  • the method discussed in the third exemplary embodiment requires a moving distance of four times the track pitch in the worst case, because it obtains the maximum and the minimum off-track time differences by advancing magnetic tape 3 at a speed ⁇ fraction (10/9) ⁇ (ten-ninth) of the normal speed.
  • the target tracking time difference can be detected within one-half or less of the time needed in the third exemplary embodiment.
  • target tracking time difference detector 118 stores a value given by averaging the synchronizing signal time difference D in the tracking position B of FIG.
  • Target tracking time difference detector 118 then produces one-half the sum of these mean maximum and mean minimum off-track time differences as a target tracking time difference to be output. Variations in the detected results of the target tracking time differences can be thus alleviated, and the desired detecting accuracy obtained in this manner. It is also evident with the method of this exemplary embodiment that a time required to detect and obtain the averaged synchronizing signal time difference is shorter as compared to that of the third exemplary embodiment. The reason is that the method of this exemplary embodiment needs the magnetic tape to move only a distance twice that of the track pitch or less, whereas the third exemplary embodiment requires a distance four times that of the track pitch multiplied by the number of times necessary to obtain the mean value.
  • the fourth exemplary embodiment makes possible to detect the target tracking time difference highly accurately within a short time.
  • magnetic tape 3 shown in FIG. 12 represents a reference tape having necessary data recorded by a standard apparatus.
  • the data is reproduced, and a target tracking time difference is detected according to the method described above.
  • a delay time of L-ch sync-signal delay circuit 108 is B
  • a delay time of R-ch sync-signal delay circuit 109 is 2B.
  • Target tracking time difference is not detected if mounting heights and staggers of reproducing heads of the apparatus under the adjustments are equivalent to those of the standard apparatus. Therefore, it is known that the target tracking time difference detected by reproduction of the reference tape corresponds to an amount of mounting deviation of the reproducing head.
  • the target tracking time difference of each head is forwarded to reference reproduction divergence memory 110 via circuit operation controller 122 , where it is stored as a reference reproduction divergent time.
  • R-ch sync-signal delay circuit 109 adjusts a delay time of R-ch synchronizing signal (pulse) by subtracting the reference reproduction divergent time for each head from the delay time 2B. In other words, this makes an adjustment possible to eliminate the target tracking time difference when the reference tape is replayed even if mounting positions of the reproducing heads are different from those of the standard apparatus.
  • a delay time of R-ch data delay circuit is 2B at this time. Since a synchronizing signal time difference output by sync-signal time difference detector 7 in this operation represents a divergence of recording head stagger, the synchronizing signal time difference for each head is forwarded via circuit operation controller 122 to reference recording divergence memory 105 for storage as a reference recording divergence time (the reference recording divergence time becomes zero if the recording head stagger is equivalent to that of the standard apparatus).
  • R-ch data delay circuit 104 takes a delay time by subtracting the reference recording divergence time for each head from the delay time 2B. In other words, this makes an adjustment possible to allow the apparatus capable of recording the data with same time difference of the synchronizing signal as the reference tape even if the head stagger of the recording heads are different from those of the standard apparatus.
  • FIG. 12 Described above in the fourth exemplary embodiment (FIG. 12) is the magnetic recording/reproducing apparatus equipped with recording heads and reproducing heads.
  • the method discussed above in which a delay time of the R-ch data delay circuit is set by storing a reference recording divergence is obviously applicable to any magnetic recording/reproducing apparatus that uses all of recording heads 100 a, 100 b, 100 c and 100 d to also serve as reproducing heads.
  • FIG. 15 is a block diagram of a magnetic recording/reproducing apparatus according to the fifth exemplary embodiment. Components of like functions as those of the magnetic recording/reproducing apparatus of the fourth exemplary embodiment are designated with like reference numerals, and their details will therefore be skipped.
  • initial tracking time difference detector 123 and adder 124 are added as new components to the structure of the fourth exemplary embodiment.
  • Initial tracking time difference detector 123 has a function of detecting an initial tracking time difference from a synchronizing signal time difference input by sync-signal time difference detector 7 based on a data from capstan controller 151 and a command of circuit operation controller 122 .
  • switch 120 is connected to “a” side by a command of circuit operation controller 122 , and capstan controller 151 controls tracking in a manner so that an output of sync-signal time difference detector 7 becomes equal to the initial tracking time difference.
  • a command of circuit operation controller 122 turns switch 120 into connection with “b” side.
  • Offset time difference controller gives an offset to the initial tracking time difference via adder 124 , so as to perform an offsetting operation in the same manner as described in the fourth exemplary embodiment.
  • target tracking time difference detector 118 detects a target tracking time difference in the course of this process, a command of circuit operation controller 122 turns switch 120 into connection with “c” side to proceed into a normal state of on-tracking operation.
  • FIG. 16 is a block diagram depicting an example of initial tracking time difference detector.
  • the synchronizing signal time difference is input from sync-signal time difference detector 7 .
  • a time difference detection pulse A is a holding pulse for holding the last or present individual synchronizing signal time differences at a time a reproducing condition is satisfactory in a predetermined track number during a period wherein a head switching signal is at a high level.
  • a time difference detection pulse B is a holding pulse for holding the last or present individual synchronizing signal time differences at a time a reproducing condition is satisfactory in a predetermined track number during a period wherein a head switching signal is at a low level.
  • Initial tracking time difference detection control signals are control signals, each of which changes to a high level only for a period necessary to detect an initial tracking time difference, and they are each output by circuit operation controller 122 . (here, satisfactory reproducing condition means that either a number of the synchronizing signals shown in FIG. 15 is equal to a predetermined number or more, or an error rate is equal to a predetermined level or less.)
  • Each of subtracters 163 subtracts a negative side value from a positive side value, and each of adders 165 adds both inputs.
  • Each of dividers 164 divides its input by a predetermined divisor.
  • Each of delay elements 166 latches its input with a predetermined pulse.
  • AND element 167 ANDs both of its inputs.
  • Multiplexer 168 selects a high side input when control terminal S is at a high level, and a low side input when the control terminal S is at a low level.
  • Each combination of these components 163 , 164 , 165 and 166 in this drawing constitute a low-pass filter of a predetermined time constant (hereinafter “LPF”).
  • LPF predetermined time constant
  • LPF “A” having the above structure of FIG. 16 takes synchronizing signal time differences in a predetermined track number during a period in which a head switching signal is at a high level, and averages them with the predetermined time constant.
  • LPF “B” also takes synchronizing signal time differences in a predetermined track number during a period in which a head switching signal is at a low level, and averages them with the predetermined time constant in the like manner.
  • an initial tracking time difference detection control signal turns into a low level so as to hold the initial tracking time differences to Tsh′ and Tsl′ respectively.
  • These initial tracking time differences Tsh′ and Tsl′ are input to subtracter 121 via switch 120 , to ensure positive tracking at a given off-track position, although it is not an ideal on-track condition.
  • offset time difference controller 119 uses the synchronizing signal time differences Tsh and Tsl for its offset operation at the same time, it can initiate the offset operation steadily.
  • FIG. 18 shows a block diagram of another embodied example of initial tracking time difference detector 123 .
  • head switch H-side center detector 160 detects a maximum value and a minimum value of one cyclic period of head switching signal among the synchronizing signal time differences during a period wherein a tape advancing speed is slower than the normal speed and a head switching signal is at a high level, in a predetermined track number, and outputs a value one-half the sum of these maximum and minimum values.
  • Head switch L-side center detector 161 also operates in the same manner.
  • Initial tracking time differences in this operation gradually reach values close to Tsh and Tsl with every head cycle, as shown in FIG. 19, and in the like manner as described in the previous example.
  • an initial tracking time difference detection control signal turns into a low level so as to hold the initial tracking time differences to Tsh′ and Tsl′ respectively.
  • these initial tracking time differences Tsh′ and Tsl′ are input to subtracter 121 via switch 120 , to ensure positive tracking at a given off-track position, although it is not an ideal on-track condition.
  • offset time difference controller 119 uses the synchronizing signal time differences Tsh and Tsl for its offset operation at the same time, it can initiate the offset operation steadily.
  • this structure increases a scale of the circuitry, as shown in FIG. 17, a significant advantage is its ability of detecting the initial tracking time difference within an initial start-up period before a rotational speed of the rotary drum and a tape forwarding speed reach their regular speeds while the reproducing heads are scanning the tracks diagonally. In other words, it can enter into the offsetting operation more quickly as compared with the other embodied example shown in FIG. 16. If the magnetic recording/reproducing apparatus is a type that plays a cassette tape and the like, it can further shorten the time from tape loading to data reproduction.
  • provision of the initial tracking time difference detector enables the apparatus to ensure stable initial tracking and to start the offset operation smoothly by way of detecting an initial tracking time difference at the start of a reproduction operation (i.e. a transition period of the operation) instead of using a fixed value of initial target tracking time difference.
  • FIG. 20 is a block diagram of a magnetic recording/reproducing apparatus according to the sixth exemplary embodiment.
  • Components of like functions as those of the magnetic recording/reproducing apparatus of the fifth exemplary embodiment are designated with like reference numerals, and their details are therefore skipped.
  • Sync-signal time difference enhancing circuit 125 replaces a synchronizing signal time difference signal from subtracter 121 with a predetermined value based on a data received from circuit operation controller 122 , and outputs it to capstan controller 151 instead of the synchronizing signal time difference signal.
  • sync-signal time difference enhancing circuit 125 brings the tracking back to the negative side by delivering a predetermined positive value for interpolation to capstan controller 151 .
  • sync-signal time difference enhancing circuit 125 brings the tracking back to the positive side by delivering a predetermined negative value for interpolation to capstan controller 151 .
  • sync-signal time difference enhancing circuit 125 performs a similar replacement operation when the track number data does not agree to a predetermined relation with respect to a synchronizing signal time difference even if the synchronizing signal time difference is obtained.
  • the structure described above makes the apparatus capable of maintaining stable tracking by an appropriate interpolation even under unstable tracking condition when the synchronizing signal time difference is not obtainable during the offsetting operation.
  • offset time difference controller 119 also functions at the same time to subtract a predetermined value from the offset value when it is in the positive side, or to add a predetermined value to the offset value when it is in the negative side, to stabilize the offsetting operation.
  • FIG. 21 is a block diagram of a magnetic recording/reproducing apparatus according to the seventh exemplary embodiment. Components of like functions as those of the magnetic recording/reproducing apparatus of the sixth exemplary embodiment are designated with like reference numerals, and their details are therefore skipped.
  • Tracking time difference correction detector 126 detects a correction value for correcting a target tracking time difference detected by target tracking time difference detector 118 based on a delayed L-ch synchronizing signal pulse output by L-ch sync-signal delay circuit 108 .
  • FIG. 22 is a diagrammatic illustration for explaining an operation of tracking time difference correction detector 126 .
  • FIG. 22 ( a ) represents a relation between tracks and heads at a point of time when target tracking time difference detector 118 detects a target tracking time difference. It is obvious from the figure that the target tracking time difference is zero at this point of time.
  • Head L and head R are mounted apart with a distance, or a head stagger, corresponding to four synchronizing signals (i.e. 4 ⁇ Y).
  • rotary drum 1 expands with temperature rise of the apparatus, which results in an increase in its diameter.
  • this figure (b) shows a distance X as an amount of increase in the head stagger from the head L to the head R.
  • This change of distance X causes a divergence Tx in synchronizing time difference in a proportional ratio, which can result in an off-track by a deviation of ⁇ A as shown in FIG. 22( c ).
  • Equation 22(a) gives a circumferential velocity of the rotary drum
  • equation 22(b) gives a track angle.
  • ⁇ represents (sin ⁇ L/sin ⁇ t).
  • a head-to-tape relative speed under the condition of FIG. 22( b ) is given by the equation 22(d) when (sin ⁇ L/sin ⁇ t) is denoted by ⁇ , considering that it is about equal to (sin ⁇ L/sin ⁇ t′), since the change ⁇ t is small.
  • distance X of FIG. 22( b ) is given by equation 22(e)
  • a synchronizing signal time difference resulting from the distance X is given by equation 22(f).
  • time difference Tx is a value derived by subtracting a time required to reproduce data over a length of four synchronizing signals (a time duration corresponding to a distance of the head stagger) in FIG. 22( b ) from a time required to reproduce data over a length of four synchronizing signals (a time duration corresponding to a distance of the head stagger) in FIG. 22( a ).
  • Tracking time difference correction detector 126 has the following function and it operates in a manner as described hereinafter. First, it measures and stores, as an initial stagger distance reproduction time, a time required to reproduce the data over the length of four synchronizing signals (4Y/Vht), when target tracking time difference detector 118 detects a target tracking time difference (at the point of time represented by FIG. 22( a )). It detects a change in diameter of the rotary drum as it varies due to a thermal effect, by measuring a value (4Y/Vht′) from time to time. It then outputs the time difference Tx given by the equation 22(f) to target tracking time difference detector 118 , which in turn makes correction of the target tracking time difference detected previously.
  • 4Y/Vht a time required to reproduce the data over the length of four synchronizing signals
  • a stagger distance reproduction time i.e. the time required to reproduce data over a number of synchronizing signals corresponding to a distance of the head stagger
  • the above-described structure can maintain optimum tracking by automatically following variations in the target tracking time difference, even if they occur after detection of the target tracking time difference due to thermal expansion and contraction of the rotary drum with changes in temperature of the apparatus.
  • FIG. 23 is a diagrammatic illustration for use to explain an operation of correcting a timing of synchronizing signal when making a splice recording.
  • Subtracter 201 subtracts a recording/reproducing time difference output by tracking time difference correction detector 126 from a synchronizing signal time difference output by sync-signal time difference detector 7 .
  • Adder 202 adds a target tracking time difference T 2 output by target tracking time difference calculator 203 to a recording/reproducing time difference output by tracking time difference correction detector 126 .
  • Target tracking time difference calculator 203 calculates a target tracking time difference based on an output of subtracter 201 .
  • FIG. 24 is a diagrammatic drawing showing track patterns in the splice recording, wherein FIG. 24( a ) is a diagram showing positional relations of heads with respect to tracks during a pre-rolling operation, and FIG. 24( b ) is another diagram showing positional relations of the heads with respect to the tracks during a splice recording.
  • sync-signal time difference detector 7 outputs a time difference T between reproduced L-ch synchronizing signal and R-ch synchronizing signal. Although there is a shift Tm of the synchronizing signals between L-ch track and R-ch track, as shown in FIG.
  • Value Tm+ ⁇ Ta is input to target tracking time difference calculator 203 inside target tracking time difference detector 118 , and it is subjected to a filtering process by being passed through a low-pass filter inside thereof, which obtains value Tm as target tracking time difference T 2 .
  • the tracking control can be carried out steadily during the pre-rolling operation even if there is a deviation in time difference between L-ch and R-ch synchronizing signals in reproduction due to thermal expansion of the rotary drum, deviation of the recorded synchronizing signals, and so forth.
  • reference recording divergence memory 105 has a time data stored in advance for adjustment of a delay time of recording data for R-ch with respect to L-ch in order to record the data with a time difference of synchronizing signal equal to that of the reference tape.
  • the splice recording is made based on the corrected delay time.
  • the delay time of recording data for R-ch can be corrected by a period Tm with respect to L-ch, as shown in FIG. 24( b ), and thereby this embodiment can make recording positions of synchronizing signals for both R-ch and L-ch in alignment with respect to each other before and after the point of splice recording.
  • a synchronizing signal time difference output by sync-signal time difference detector 7 is Tm+ ⁇ Ta.
  • Target tracking time difference calculator 203 inside tracking time difference detector 118 obtains value Tm as target tracking time difference T 2 , and target tracking time difference T 1 is also equal to value Tm.
  • an output of subtracter 121 becomes ⁇ Ta, which can therefore realize stable tracking control based on accurate tracking error data following the point of splice recording in the same way as that before the point of splice recording.
  • the embodied structure has a similar effect of correction even if an expansion or contraction of the tape occurs at the same time due to changes in temperature and humidity.
  • the invention can realize stable tracking performance even if there are variations in mounting of heads, changes of mounted positions of the heads due to temperature change, changes in track positions on a tape due to temperature and humidity change, and so on.

Landscapes

  • Adjustment Of The Magnetic Head Position Track Following On Tapes (AREA)
  • Television Signal Processing For Recording (AREA)
  • Signal Processing For Digital Recording And Reproducing (AREA)
US10/476,192 2001-06-12 2002-06-06 Magnetic recording/reproducing apparatus Abandoned US20040109256A1 (en)

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PCT/JP2002/005589 WO2002101739A1 (fr) 2001-06-12 2002-06-06 Appareil d'enregistrement/reproduction magnetique

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JP6248727B2 (ja) * 2014-03-18 2017-12-20 富士通株式会社 磁気テープ制御装置、制御プログラム、及び制御方法

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US5212603A (en) * 1988-08-26 1993-05-18 Canon Kabushiki Kaisha Tracking control means for a multi-channel reproducing apparatus
US5325246A (en) * 1992-06-01 1994-06-28 Datatape Incorporated Automatic tracking method for helical scan magnetic tape recorder using reproduced timing signal to sample two out-of-phase reference signals
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CN1500268A (zh) 2004-05-26
WO2002101739A1 (fr) 2002-12-19
CN1272788C (zh) 2006-08-30
US7130147B2 (en) 2006-10-31
US20060056102A1 (en) 2006-03-16

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