Dynamic magnetic information storage or retrieval – Automatic control of a recorder mechanism – Controlling the head
Reexamination Certificate
1999-06-04
2003-06-24
Holder, Regina N. (Department: 2651)
Dynamic magnetic information storage or retrieval
Automatic control of a recorder mechanism
Controlling the head
Reexamination Certificate
active
06583948
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a disc recording and/or reproducing apparatus (will be referred to as “disc drive” hereinunder) for recording and/or reproducing data to and/or from a disc-shaped recording medium such as an optical disc, magnetic disc, etc., and more particularly to a disc drive including a servo signal writing apparatus to write servo signals to a disc-shaped recording medium.
Also, the present invention relates to a servo signal writing apparatus used to write servo signals to a disc-shaped recording medium such as an optical disc, magnetic disc, etc.
2. Description of Related Art
Since tracking is controlled during write or read of data to or from a disc in a conventional disc drive such as a hard disc drive, the disc as a recording medium should have previously formed thereon tracks each defining a radial writing position.
Thus, in a disc drive before shipment from the factory, a magnetic head incorporated in the disc drive is used to write tracking servo signals to a disc used in the disc drive to form such tracks on the disc.
However, such a disc drive cannot control the position of the magnetic head if no servo signals are recorded on the disc. To write servo signals to a disc having no signal recorded thereon, a servo signal writing apparatus is used which controls the disc-radial position, etc. of the magnetic head to write servo signals to the disc.
Various servo signal writing apparatus have so far been proposed, of which a typical one is well known which has an encoder installed to a magnetic head holding arm to control the position of the magnetic head to record servo signals to the magnetic disc. In this servo signal writing apparatus, the encoder is installed with a fixing pin to the magnetic head holding arm, and the moving position of the magnetic head is controlled to record the servo signal. Since in this servo signal writing apparatus, the magnetic head holding arm is mechanically connected, however, there will take place a difference in installed condition of the magnetic head holding arm between when the servo signal is recorded on the disc and when the servo signal is used in practice, so that the servo signal can hardly be recorded with an improved accuracy. Also, since the closed disc drive has to be opened for the actual use of the servo signal, the servo signals must be written to the disc in a clean room, which will lead to an increase of manufacturing costs.
Further, in another example of the servo signal writing apparatus, a servo loop is formed for a pit or groove formed in the magnetic head holding arm to follow a laser light emitted from an optical head, and a servo loop is formed to detect, by an encoder, a moving position of the optical head emitting the laser light to control the moving position of the optical head, thereby controlling the moving position of the magnetic head to write servo signals to a disc. Since this apparatus controls the moving position of the magnetic head by the use of the laser light emitted from outside the disc drive, the servo signal can be written with no contact with the magnetic head holding arm. Therefore, different from the above-mentioned apparatus, this apparatus makes it unnecessary to write servo signals to a disc in the clean room or the like. In this servo signal writing apparatus, however, it is necessary to form the two servo loops, one for allowing the magnetic head holding arm to follow the movement of the optical head and the other for controlling the position of the optical head based on a detection output from the encoder. Thus the apparatus can hardly write servo signals with an improved accuracy and at a high speed.
To solve the above-mentioned problems involved in the conventional servo signal writing apparatuses, the Inventor of the present invention had proposed servo signal writing apparatuses as disclosed in the Provisional Publication of the Japanese Patent Application Nos. 4-351766 and 4-351767, respectively. In a hard disc drive comprising a scale provided on a magnetic head holding arm and which has a diffraction grating formed thereon, the servo signal writing apparatus detects the diffraction grating on the scale to write servo signals to the hard disc.
Referring now to
FIG. 1
, there is illustrated the servo signal writing apparatus proposed by the Inventor of the present invention.
In
FIG. 1
, the servo signal writing apparatus is generally indicated with a reference
100
, and a hard disc drive in which servo signals are written to a disc is generally indicated with a reference
110
. The hard disc drive
110
comprises an enclosure
111
, and a magnetic disc
112
, magnetic head
113
, arm
114
and an arm support
115
provided inside the enclosure
111
.
As will be seen in
FIG. 1
, the arm
114
has the magnetic head
113
provided at one end thereof. The arm
114
is installed at the other end thereof to the arm support
115
. The arm support
115
has built therein a voice coil motor which will drive the arm
114
when it is supplied with a drive current. As the arm
114
is driven by the voice coil motor provided inside the arm support
115
, the arm
114
will be turned about a pivot
114
a
provided at one end portion thereof in a plane parallel to a signal recording surface of the magnetic disc
112
. As the arm
114
turns in this way, the magnetic head
113
will move from the lead-in area toward the lead-out area, for example, of the magnetic disc
112
. Thus, the magnetic head
113
is movable radially of the magnetic disc
112
to write data on the entire recording area of the magnetic disc
112
. The rotating angle of the arm
114
varies depending upon the length of the arm
114
and size of the magnetic disc
112
. The angle of rotation is about 30°, for example.
In the hard disc drive
110
, the arm
114
has a scale
116
installed thereon near the base end thereof. As the arm
114
turns, the scale
116
is turned along with the magnetic head
113
in a plane parallel to the magnetic disc
112
. The scale
116
has formed thereon a diffraction grating indicating a disc-radial position of the magnetic head
113
. The diffraction grating formed on the scale
116
can be read by irradiating a laser light onto the diffraction grating from outside the hard disc drive
110
. For example, a portion of the enclosure
111
opposite to the scale
116
is formed from a transparent material such as acryl, glass or the like so that the diffraction grating can be read from outside.
The diffraction grating formed on the scale
116
is recorded over a width L as shown in FIG.
2
. The recorded width L is larger than the movable range of a portion of the arm
114
where the scale
116
is provided, so that the diffraction grating can be detected even when the magnetic head
113
has moved from the lead-in area to the lead-out area on the magnetic disc
112
(for example, when the arm
114
turns through an angle of about 30°).
As shown in
FIG. 1
, the conventional servo signal writing apparatus
100
to write servo signals to the disc in the hard disc drive
110
constructed as in the above, comprises an optical head
101
to irradiate a laser light onto the scale
116
and detect a reflected laser light from the scale
116
, thereby detecting the diffraction grating formed on the scale
116
, and a control circuit
102
to receive a detection signal from the optical head
101
and produce a magnetic head drive signal and servo signal for use to drive the magnetic head
113
based on the received detection signal.
The optical head
101
irradiates a laser light to the diffraction grating formed on the scale
116
. The diffraction grating diffracts the incident laser light. The optical head
101
detects the reflected laser light diffracted by the diffraction grating to detect a phase component of the reflected laser light. As the arm
114
turns, the scale
116
provided thereon also turns along with the arm
114
. The phase of the reflected laser light from the diffraction grating varies as the arm
11
Holder Regina N.
Maioli Jay H.
Slavitt Mitchell
Sony Precision Technology Inc.
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