Dynamic magnetic information storage or retrieval – General processing of a digital signal – Data in specific format
Reexamination Certificate
1998-11-13
2002-01-29
Neal, Regina Y. (Department: 2651)
Dynamic magnetic information storage or retrieval
General processing of a digital signal
Data in specific format
C360S077120
Reexamination Certificate
active
06342983
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording apparatus for recording data on a recording tape medium compatible with a so-called timing ATF (Automatic Track Following) servo system as tracking servo control, a recording tape medium on which recording is to be done by this recording apparatus, and a measuring apparatus for measuring a reference value for timing ATF servo in reproducing data from this recording tape medium.
2. Description of the Related Art
Digital data storage equipment (DDS equipment) enabled to record and reproduce computer data has been developed by using a digital audio tape player (DAT recorder/player) for recording and reproducing digital audio data on and from a magnetic tape, for instance, or a DAT system similarly using a magnetic tape, as a data storage system for the computer.
In these apparatuses, high density recording is made possible by causing them to perform recording/reproducing scanning by a helical scanning system using magnetic heads on a rotary drum by having a magnetic tape run in a state wherein the tape is wound round the rotary drum in a lap angle of, for instance, 90° and at the same time rotating the rotary drum.
In this case, inclined tracks TKA and TKB, for instance, are formed on the tape as shown in FIG.
20
. The inclined tracks TKA and TKB are tracks formed by a pair of heads (head A and head B) mounted on the rotary drum and differing in azimuthal direction, i.e. tracks considered to have inverse azimuths to each other.
Incidentally, whereas the magnetic heads should accurately trace tracks TK on the tape during reproduction, systems to control this tracking include, for example, tracking servo control operation, which is known as timing ATF system, for DDS reproducing apparatuses.
This timing ATF system measures the length of time (tracking detection period) from the reference phase position of the rotary drum until a prescribed signal (timing detection signal) is detected from a track by a head, and the measured value is compared with a reference value, with the error equivalent being used as servo error information.
And, it is caused to be reflected in the tape running speed by controlling the rotating speed of the capstan motor for tape running according to that servo error information. Thus the relative speed with respect to the rotating speed of the drum and the running speed of the tape is adjusted by regulating the running speed of the tape so as to achieve a satisfactory tracking state.
Suppose, for instance as illustrated in
FIG. 21
, that the phase position of the rotary drum is the reference position when the scanning position of the magnetic head relative to a certain track has come to a positional state corresponding to a line (timing) indicated as TRA in the figure. Since the configuration is such that, at the time when the reference phase position is arrived at during the rotation of the drum, a pulse signal is generated from a pulse generator (PG) arranged on the drum motor, for example, the timing TRA at which the rotary drum has come to the reference phase position can be detected. After that, as the magnetic head comes into contact with the magnetic tape and scans the track TKA, a timing detection signal is detected in a prescribed position PTTP on the track as reproduced data. This timing detection signal is supposed to provide a pulse in the position PTTP predetermined on the basis of a sync signal in the data and the detection of an address.
Whereas three ways of scanning differing in tracking phase state relative to the track TKA are shown here as {circle around (1)}, {circle around (2)} and {circle around (3)} in the figure, the period from the timing of the reference phase position of the rotary drum (the position of the line TRA) until the timing at which the position PTTP is reached (the tracking detection period) varies in length with the way of scanning, {circle around (1)}, {circle around (2)} or {circle around (3)}, as indicated by t1, t2 and t3.
For the tracking detection period, the time length t1, which is obtained when the magnetic head is in a satisfactory tracking state for the track TK, i.e. in a state wherein the center of the track TKA is traced as in {circle around (1)}, is preset and, therefore, if scanning as in {circle around (1)} is performed and the time length t1 is measured as the tracking detection period while under tracking servo control, the measured value and the reference value will coincide with each other. Thus, in this case, there is no error between the measured value and the reference value, and a satisfactory tracking state is found to be achieved. On the other hand, if scanning is performed in a tracking phase state as in {circle around (2)} or {circle around (3)}, the measured value of the tracking detection period will be t2 or t3, and there will be an error compared with the reference value. In this case, there is a tracking lag equivalent to that error, and servo control toward a just tracking state can be executed by causing this to be reflected in the tape running speed.
Whereas the reference value should be identified in advance in executing such timing ATF servo, this reference value, as stated above, is the length of time from the timing of the reference phase position of the rotary drum in the just tracking state until the timing at which a timing detection signal is obtained. As the timing detection signal is generated in accordance with, for instance, the detection of a sync signal at a prescribed address on the track, its position PTTP is fixed on each track of various tapes, but in practice mechanical errors and the like in various recording apparatuses and reproducing apparatuses inevitably give rise to positional lags between a plurality of tracks formed even in a single round of continuous recording. For this reason, when certain file data are to be reproduced with a DDS reproducing apparatus, the reference value on that particular tape (that file data track) should be measured in advance of executing the reading of those data to be reproduced.
For measuring this reference value, such processing is accomplished that scanning of the track is executed in various tracking phase states to calculate an average, for example, from the tracking detection periods measured in those scanning procedures and to use it as the reference value.
Its image is shown, for example, in FIG.
22
. If, as illustrated, the track TKA is scanned in a plurality of different tracking phase states, such as TJ
1
to TJ
5
for instance, and an average is calculated from the different tracking detection periods measured during the scanning procedures, a tracking detection period in the approximate vicinity of the tracking phase state TJ
3
in the figure will be obtained. This can be regarded as the tracking detection period substantially in the vicinity of the just tracking state, and accordingly this is used as the reference value.
Incidentally, here is considered a case in which a plurality of recorded areas each formed by one continuous recording operation known as streaming, i.e. execution of a series of actions from the start of recording until the end of recording without stopping the running of the magnetic tape on the way (hereinafter such recording areas may also be referred to as “streaming recorded areas”) are linked to form a recorded area on the magnetic tape.
In this case, in streaming recorded areas each formed by a single round of streaming, the position of the track recorded on the magnetic tape may shift from one streaming recorded area to another, affected by a difference in recording apparatus or, even if recording is performed by the same recording apparatus, by various conditions including mechanical action errors or temperature variations at the time of recording.
Here even if, for instance, a common value is set, as the reference value for the above-mentioned timing ATF servo, by mere scanning for a recorded area formed by linking of a plurality of streaming recorded areas such as described above, this
Nonoyama Hideki
Uchida Tomonao
Chang Dexter T.
Frommer William S.
Frommer & Lawrence & Haug LLP
Neal Regina Y.
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