Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2001-01-29
2003-01-14
Edun, Muhammad (Department: 2653)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S044140, C369S112010, C369S119000
Reexamination Certificate
active
06507543
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk apparatus used for performing data-processing with optical disks. The data-processing may include recording, reading or deleting of data. The optical disk may include a magneto-optical disk with which magnetic field modulation or optical pulse modulation may be used for performing required data-processing.
2. Description of the Related Art
FIGS. 36 and 37
of the accompanying drawings show a conventional disk apparatus disclosed in JP-A-11(1999)-213419. As illustrated, the conventional apparatus includes an elongated swing arm
90
, a flexible suspension
91
, a fine adjustment actuator
92
, a mirror
93
and a slider
94
. The suspension
91
is attached, at one end, to the swing arm
90
, while carrying, at the other end, the actuator
92
, the mirror
93
and the slider
94
. The swing arm
90
is attached to a spindle
95
which in turn is connected to a motor Ma. Upon turning on the motor Ma, the swing arm
90
is caused to rotate forward or backward about the axis of the spindle
95
, whereby the slider
94
, together with the actuator
92
and the mirror
93
, is moved in the tracking direction Tg over the disk D. The fine adjustment actuator
92
is designed to make fine adjustments to the position of the mirror
93
and the slider
94
in the tracking direction Tg. As shown in
FIG. 37
, the slider
94
carries a lens assembly consisting of two objectives
96
.
Further, the conventional apparatus includes a spindle motor Mb arranged below the disk D. In operation, the disk D is rotated at high speed by the motor Mb. The rotation of the disk D causes air to be drawn between the slider
94
and the disk D, whereby the slider
94
floats above the disk D due to the air introduced between the slider
94
and the disk D.
The conventional disk apparatus also includes a light source
97
to emit a laser beam and a mirror
98
disposed in the path of the laser beam. As shown in
FIG. 36
, the laser beam is reflected on the mirror
98
, to travel toward the other mirror
93
. The laser beam is reflected on the mirror
93
, to be directed downward and enter the objectives
96
. The objectives
96
focus the laser beam and form a beam spot on the recording layer of the disk D.
The seeking operation of a desired one of the tracks of the disk D is performed while the swing arm
90
is being caused to pivot on the spindle
95
. Once the required track is found, the beam spot may need to remain on the target track for a while. For this purpose, tracking control is carried out by driving the fine actuator
92
for finely adjusting the position of the mirror
93
and the slider
94
in the tracking direction Tg, so that the mirror
93
and the slider
94
can follow the deviation of the target track.
Though provided with the fine actuator designed to move the relevant components in the tracking direction Tg, the conventional optical disk apparatus has been found disadvantageous in the following points.
When the disk D is rotated at high speed, the disk surface may fluctuate in the focusing direction shown by an arrow Fs in FIG.
37
. The fluctuation may be caused by unstable rotation of the disk spindle, initial geometrical error of the disk D or warping of the disk D due to gravity.
When such fluctuation occurs in the disk D, the slider
94
will rise and fall to maintain the prescribed constant distance between the disk surface and the slider
94
. Hence, the mirror
93
, mounted on the slider
94
, also moves up and down. On the other hand, the level of the laser beam traveling toward the mirror
93
does not change. This means that the height of the laser beam relative to the mirror
93
is not constant during the fluctuation of the disk D.
Specifically, it is assumed that normally (i.e., with no disk fluctuation), the center C
1
of the laser beam strikes upon apoint n
1
of the mirror
93
, as shown in FIG.
37
. However, when the disk D moves downward, as shown in
FIG. 38
, the center of the laser beam (C
2
) strikes upon a higher point n
2
on the mirror
93
. As a result, the light path extending from the mirror
93
to the objectives
96
will shift toward the spindle
95
(see arrow Na). Likewise, when the disk D moves upward, the light path will shift in the opposite direction or away from the spindle
95
.
When such shifting of the light path occurs, the center of the laser beam will deviate from the optical axis of the objectives
96
, which may make it difficult or even impossible to properly form an appropriately small beam spot on the recording layer of the disk D. In particular, when a small, solid immersion lens is used for the lower objective
96
a
of the lens assembly, the laser beam may utterly miss the lower lens
96
a.
It should be noted here that the fine actuator
92
cannot help to solve the problems, since the actuator
92
moves the mirror
93
and the slider
94
only in the tracking direction Tg (FIG.
36
), which is perpendicular to the shifting direction Na of the light path.
SUMMARY OF THE INVENTION
The present invention has been proposed under the circumstances described above, and its object is to overcome the conventional problems stemming from the fluctuation of an optical disk, so that data-recording operation or data-reading operation with an optical disk is properly performed.
According to a first aspect of the present invention, there is provided an optical disk apparatus which includes: a light source for emitting a laser beam; an objective for focusing the laser beam; a slider holding the objective and arranged to float relative to an optical disk; a suspension for supporting the slider; a first mirror supported by the suspension and spaced from the slider in a focusing direction, the first mirror being arranged to reflect the laser beam traveling in a first direction which is non-parallel to the focusing direction, so that the reflected laser beam enters the objective; and a seek mechanism for moving the suspension so that the first mirror and the slider are moved in a tracking direction. The first mirror is rotatable about a first axis for causing the reflected laser beam to shift in the first direction.
Preferably, the first mirror may be rotatable about a second axis which is non-parallel to the first axis for causing the reflected laser beam to shift in a second direction which is non-parallel to the first direction.
Preferably, the apparatus of the present invention may further include a second mirror for reflecting the laser beam between the light source and the first mirror. The second mirror may be rotatable about a third axis for causing the reflected laser beam to shift in a third direction which is non-parallel to the first direction.
According to a second aspect of the present invention, there is provided an optical disk apparatus which includes: a light source for emitting a laser beam; an objective for focusing the laser beam; a slider holding the objective and arranged to float relative to an optical disk; a suspension for supporting the slider; a first mirror supported by the suspension and spaced from the slider in a focusing direction, the first mirror being arranged to reflect the laser beam traveling in a first direction which is non-parallel to the focusing direction, so that the reflected laser beam enters the objective; a seek mechanism for moving the suspension so that the first mirror and the slider are moved in a tracking direction; and a second mirror disposed between the light source and the first mirror for reflecting the laser beam emitted by the light source toward the first mirror. The second mirror is rotatable about a first axis for causing the reflected laser beam to shift in the focusing direction.
Preferably, the second mirror may be rotatable about a second axis for causing the reflected laser beam to shift in a second direction which is non-parallel to the first direction.
In a preferred embodiment of the present invention, the first mirror may be rotatable about a third axis for causing the refl
Fujimaki Tohru
Izumi Haruhiko
LandOfFree
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