Objective lens driving device

Details Objective lens driving device Objective lens driving device

2001-02-22

2003-12-02

Klimowicz, William (Department: 2652)

Dynamic information storage or retrieval

Dynamic mechanism subsystem

Specified detail of transducer assembly support structure

C369S244100, C369S044160

Reexamination Certificate

active

06657944

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an objective lens driving device in an optical information recording or reproducing apparatus for a disk-shaped recording medium.
2. Description of Related Art
An objective lens driving device controls and drives an objective lens in two axis directions, namely, the direction perpendicular to a disk-shaped recording medium (referred to as a focusing direction in the following) and the radial direction of the disk-shaped recording medium (referred to as a tracking direction in the following), thereby suppressing a defocusing of the objective lens with respect to an information recording plane of the disk-shaped recording medium (referred to as a disk in the following) and a deviation of an optical axis of the objective lens from a disk track.
In recent years, along with the densification of disk information and the acceleration of disk rotation, it has become necessary to improve the accuracy of the above-described control performance to a higher level. This increases a demand for a wider frequency band and reduced undesired resonance in dynamic characteristics of the objective lens driving device.
On the other hand, it also has become necessary to reduce the size, in particular, the thickness of driving devices. In an optical head including the objective lens driving device, efforts are made to achieve a thinner device by shortening a working distance (referred to as WD in the following) of the objective lens and by reducing a mechanical space between the disk and a lens holder.
However, since the vibration amount of the disk surface is a standard value (for example, the standard for CDs is ±0.5 mm), when the objective lens WD is shortened excessively, the objective lens or the lens holder and the disk collide. Accordingly, measures need to be taken with respect to a damage of the disk and the objective lens caused by the collision.
In response to such demands, a protector system against the collision has been suggested in a conventional objective lens driving device, as disclosed in JP 11(1999)-312322 A.
The following is a description of the conventional objective lens driving device (disclosed in JP 11-312322 A), with reference to the accompanying drawing.
FIG. 6
is an exploded perspective view showing a configuration of the conventional objective lens driving device.
In
FIG. 6
, numeral
101
denotes an objective lens, numeral
102
denotes a lens holder, numeral
103
denotes a focusing coil, numerals
104
a
and
104
b
denote tracking coils, and numerals
105
a
and
105
b
denote coil substrates (the coil substrate
105
b
is not shown in this figure). The objective lens
101
and the coil substrates
105
a
and
105
b
are fixed firmly to the lens holder
102
in their desired position. Furthermore, the focusing coil
103
and the tracking coils
104
a
and
104
b
are wound directly around the lens holder
102
, and lead terminals of these coils are fixed by soldering to lands of circuit patterns that are formed on the coil substrates
105
a
and
105
b
. In the following, a portion constituted by the lens holder
102
and the components described above is referred to as a movable portion.
Numeral
107
denotes a holder substrate, and numeral
109
denotes a suspension holder. As on the coil substrates
105
a
and
105
b
, circuit patterns and lands are formed on the holder substrate
107
. The suspension holder
109
and the holder substrate
107
are fixed to a back yoke
112
b
, which will be described below, by a fixing screw
115
. Numerals
106
a
,
106
b
,
106
c
and
106
d
denote metal wire springs (the metal wire spring
106
d
is not shown in this figure), whose one ends are fixed to the lands on the coil substrates
105
a
and
105
b
in the movable portion and the other ends are fixed to the lands on the holder substrate
107
by soldering respectively. They support the movable portion elastically so as to be movable in the focusing direction F and the tracking direction T. A driving current applied to a terminal (not shown in the figure) on the holder substrate
107
is supplied to the focusing coil
103
and the tracking coils
104
a
and
104
b
via the metal wire springs
106
a
to
106
d.
Numeral
112
denotes an actuator base, in which a base portion
112
a
having a surface parallel to a disk
116
and plate-like back yokes
112
b
and
112
c
that are provided in this base portion
112
a
so as to protrude toward the disk
116
side and to be perpendicular to the disk
116
are formed as one piece. Magnets
113
a
and
113
b
are fixed firmly to the back yokes
112
b
and
112
c
respectively, with their north poles facing each other. In a magnetic gap of a magnetic circuit formed by the magnets
113
a
and
113
b
and the back yokes
112
b
and
112
c
, a part of the focusing coil
103
and a part of the tracking coils
104
a
and
104
b
are arranged. An electromagnetic force that is generated by a magnetic field in this magnetic gap and the driving current passed through these coils drives the movable portion in the focusing direction F and the tracking direction T. Numeral
114
denotes a shielding yoke for shielding an external magnetic influence.
Numeral
110
denotes a protector, which surrounds the objective lens
101
and is fixed firmly to an upper part of the lens holder
102
by glue
111
so as to protrude furthest from the movable portion toward the disk
116
.
The following is a description of an operation of the protector
110
. When the movable portion approaches the disk
116
too closely because of a malfunction in the focusing direction F or the like, the protector
110
protruding furthest from the movable portion toward the disk
116
alone collides with the disk
116
, thereby preventing the disk
116
and the objective lens
101
from colliding. Also, the protector
110
is formed of a material such as silicone rubber or POM resin, so that the disk
116
is not damaged when colliding.
However, in the conventional objective lens driving device with the above configuration, the protector
110
formed of silicone rubber is fixed firmly to the lens holder
102
by the glue
111
. In order to prevent the disk from being damaged, it is indeed appropriate to form the protector
110
with silicone rubber, POM resin or the like, but the silicone rubber and POM resin have an extremely small bonding strength with the glue.
Therefore, there is a problem that the repeated collision causes the protector
110
to come off from the lens holder
102
.
Also, the glue has to be applied so as not to be adhered to the colliding surface while fixing the protector
110
firmly. This poses a problem of lowering the working efficiency.
SUMMARY OF THE INVENTION
In view of the above-described problems of the conventional objective lens driving device, it is an object of the present invention to provide an objective lens driving device in which a protecting member that is formed of an elastic member such as silicone rubber can be installed without using glue and a damage prevention system that achieves a sufficient holding power even after repeated collisions is provided.
In order to achieve the object mentioned above, the objective lens driving device of the present invention has the following configuration.
A damage prevention system that is provided in the objective lens driving device of the present invention includes a protecting member formed of an elastic member and a fitting portion that is provided in the lens holder and in which the protecting member is inserted while being deformed. Only deforming the protecting member elastically and inserting it in the fitting portion complete the installation of the damage prevention system. Accordingly, it is possible not only to obtain a stable damage-prevention function even without using glue or the like, but also to achieve a protector system that can reduce manufacturing steps considerably.
Also, it is preferable that the protecting member is substantially spherical. This eliminates the need for a co

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