Dynamic information storage or retrieval – Dynamic mechanism subsystem – Having power driven transducer assembly
Reexamination Certificate
1998-04-15
2002-09-10
Miller, Brian E. (Department: 2153)
Dynamic information storage or retrieval
Dynamic mechanism subsystem
Having power driven transducer assembly
Reexamination Certificate
active
06449238
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a skew adjustment mechanism for an optical pick-up used in an optical disc drive, and in particular relates to a tangential skew adjustment mechanism for an optical pick-up used in an optical disc drive.
2. Description of the Prior Art
Optical disc drives are apparatuses which emit a laser beam to a signal surface (recorded surface) of a recording medium such as a compact disc (CD) or a CD-ROM, and then reproduces (playing back) the recorded information which is recorded on the signal surface through a great number of pits formed spirally on the surface based on changes in light intensity of the reflected laser beam. Examples of such optical disc drives include a CD-ROM drive and a CD-R (recordable) drive and the like.
These optical disc drives are provided with an optical pick-up which emits a laser beam to the optical disc and receives the beam reflected therefrom.
FIG. 23
is an exploded view which shows the structure of one of the conventional optical disc drives.
As shown in the drawing, the optical pick-up is generally composed of a pick-up base
110
which is guided in the radial direction of the optical disc by means of two guide rods
102
,
104
, an actuator base
120
which is held on the pick-up base
110
, a damper base
130
which is mounted to the actuator base
120
, a lens holder
150
which is supported displaceably in the focusing direction (F) and the tracking direction (Tr) through suspension springs
140
, and an objective lens
160
provided in the lens holder
150
.
In more details, the pick-up base
110
is formed from aluminum or other metal material using a diecasting process or the like. As shown in
FIG. 23
, the pick-up base
110
includes a laser diode (LD)
113
which emits a laser beam, a beam splitter
114
which reflects the beam fed from the laser diode
113
, a mirror
115
which reflects the beam from the beam splitter
114
toward the objective lens
160
and a photodiode
116
which receives a reflected beam reflected on the signal surface of the optical disc through the objective lens
160
, the mirror
115
and the beam splitter
114
and then generates electrical signals in response to changes in light intensity of the received laser beam. Further, the pick-up base
110
includes a pair of supporting surfaces
112
for supporting the actuator base
120
rockably about the virtual center axis (A) which extends in the radial direction of the optical disc in parallel with the guide rod.
The actuator base
120
includes a base frame
121
which is formed from a substantially square plate having a substantially square opening at the roughly central portion thereof. Therefore, the base frame
121
is comprised of a front plate portion
121
a
and a rear plate portion
121
b
which are spaced with each other along the longitudinal direction of the guide rod
102
, and a right plate portion
121
c
which is positioned at the side of the guide rod
102
and a left plate portion
121
d
which is positioned at the side of the guide rod
104
. On the outer edges of the front plate portion
121
a
and the rear plate portion
121
b
, there are integrally formed a pair of erected wall portions
122
,
122
, respectively, so as to direct upwardly. Each of these erected wall portions
122
,
122
has receiving surfaces which are adapted to be in abutment with the supporting surfaces
112
,
122
of the pickup base
110
, respectively. Further, on the outer edge of the right plate portion
121
c
of the base frame
121
, there is integrally formed a damper base supporting portion
124
so as to direct upwardly, and the damper base
130
is mounted to this supporting portion
124
. Furthermore, on the inner and outer edges of the left plate portion
121
d
of the base frame, there are integrally formed yokes
126
,
127
, respectively, so as to direct upwardly. On the inner surface of the inner yoke
126
, there is provided a magnet
128
.
As stated in the above, on the damper base supporting portion
124
of the actuator base
120
, the damper base
130
is mounted through a screw
132
. From the upper and lower portions of both sides of the damper base
130
, four suspension springs
140
extend toward the lens holder
150
to support the lens holder
150
so as to be displaceable in both the tracking direction and the focusing direction.
On the lens holder
150
, there are provided a focusing servo coil
152
and a tracking servo coil
154
. These coils are arranged such that the yoke
126
of the actuator base
120
is positioned within the tracking servo coil
152
and the yoke
127
is positioned so as to face the focusing servo coil
154
, respectively, when the damper base
130
is mounted to the supporting plate portion
124
of the actuator base
120
.
In the optical pick-up having the above structure, the beam emitted from the laser diode
113
is reflected by the beam splitter
114
toward the mirror
115
, and the beam reflected on the mirror
115
is focused onto the signal surface of the optical disc through the objective lens
160
. The beam reflected on the signal surface of the optical disc passes the objective lens
160
and the beam is then reflected on the mirror
115
again and passes through the beam splitter
114
, and then the beam is received by the photodiode
116
. In this way, electrical signals responsive to changes in the light intensity of the received beam are produced in the photodiode
116
, and based on thus produced electrical signals, the information recorded on the signal surface of the optical disc are reproduced.
In order to accurately read out the information recorded on the signal surface of the optical disc using the optical pick-up
100
having the above described structure, it is required that an optical axis of the beam emitted toward the optical disc through the objective lens
160
is directed vertically with respect to the signal surface of the optical disc such that the beam is properly focused on the signal surface.
However, the optical pick-up is composed of a plurality of components or parts as described above, so that there is a case that the beam is not always emitted to the signal surface of the optical disc vertically because of dimensional deviations of the respective components or parts and deviations caused upon assembling.
For this reason, the optical pick-up is provided with a skew adjustment mechanism for adjusting the direction of the beam when assembling the components and parts. In general, the skew adjustment is carried out through a radial skew adjustment and a tangential skew adjustment.
The radial skew adjustment means to adjust the beam emitting direction along the radial direction of the optical disc. In the prior art optical pick-up, such a radial skew adjustment is carried out by appropriately rotating the damper base
130
about the screw
132
in the directions indicated by the arrow (R) in the drawing.
For this purpose, in this prior art optical pick-up, a screw hole
135
is formed on the lower surface of the damper base
130
at one side thereof, and a screw
137
which passes the base frame
121
of the actuator base
120
is threaded thereinto, as shown in FIG.
24
. Further, on the other side of the lower surface of the damper base
130
which is opposite to the screw hole
135
, a concave portion
136
is formed and a spring
138
is disposed between the bottom of the concave portion and the actuator base
120
. This spring
136
urges the damper base
130
so that the damper base can rotate about the screw
132
in the anti-clockwise direction.
When the radial skew adjustment is to be carried out, first the screw
132
is loosened so that the damper base
130
can be pivoted about the axis of the screw
132
. Then, the screw
137
is adjusted from the underside of the actuator base
120
to rotate the damper base
130
to a desired position, and in this state the screw
132
is fastened to fix the damper base
130
onto the supporting plate portion
124
at that position. In this wa
Furukawa Ken′ichi
Imi Kazutomo
Manabe Satoru
Teranishi Kouji
Kupstas Tod
Miller Brian E.
Mitsumi Electric Co. Ltd.
Patents & TMS, P. C.
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