Optical: systems and elements – Lens – With support
Reexamination Certificate
2004-02-06
2004-08-31
Dang, Hung X. (Department: 2873)
Optical: systems and elements
Lens
With support
C359S824000, C369S044150
Reexamination Certificate
active
06785065
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an apparatus and a method of driving an optical pickup actuator, and more particularly, to an apparatus and a method of driving an optical pickup actuator in which a focus coil, a track coil, and a tilt coil which drive an optical pickup in a focus direction, a track direction, and a tilt direction, respectively, are provided at both sides of a bobbin to secure the remaining sides of the bobbin, and the focus coil is also used as the tilt coil.
2. Description of the Related Art
In general, optical pickups are adopted in optical recording/reproducing apparatuses. An optical pickup performs recording and/or reproduction of information with respect to a recording medium, such as an optical disk, placed on a turntable in a non-contact manner while moving in a radial direction of the optical disk.
The optical pickup includes an objective lens which forms a light spot on the optical disk by focusing light emitted from a light source, and an actuator which controls the objective lens in a track direction, a focus direction, and a tilt direction so as to accurately place the light spot formed by the objective lens on the optical disk.
The optical pickup actuator includes a double axes driving actuator which drives the optical pickup in the track direction and the focus direction. Recently, to perform a high density recording, the N/A of the objective lens has been increased and the wavelength of a laser has been decreased. However, a margin in tilt of the optical pickup actuator decreases in response to increase of the N/A and decrease of the wavelength. To compensate for the reduced tilt margin, three axes or four axes driving actuators capable of driving an optical pickup in the tilt direction are needed in addition to the existing double axes driving actuator. The three axes driving refers to driving in the focus direction, the track direction, and the tilt direction. The four axes driving refers to driving in the focus direction, the track direction, a tilt radial direction, and a tilt tangential direction. Referring to
FIG. 1
, the focus direction, the track direction, the tilt radial direction, and the tilt tangential direction are indicated by L-L′, M-M′, N, and O, respectively.
FIG. 1
shows a conventional optical pickup actuator which includes a base
100
, a holder
103
fixed to the base
100
, a bobbin
107
where an objective lens
105
is mounted, wires
109
which connect the bobbin
107
to the holder
103
, and a magnetic driving portion (described below) which moves the bobbin
107
in the track direction, the focus direction, or the tilt direction.
The magnetic driving portion includes a couple of a focus coil
110
and a tilt coil
112
(see
FIG. 2A
) provided at each of the opposite side surfaces
107
a
of the bobbin
107
, a track coil
115
arranged at each of the other side surfaces
107
b
where the focus coils
110
and the tilt coils
112
are not arranged, and first and second magnets
117
and
119
installed on the base
100
to face the focus coils
110
, the tilt coils
112
, and the track coils
115
with corresponding predetermined intervals therebetween. Outer yokes
118
and
120
which fix the first and second magnets
117
and
119
are installed on the base
100
. Inner yokes
122
are installed on the base
100
at corresponding positions facing the first magnets
117
to guide the bobbin
107
. The outer yokes
118
and
120
and the inner yokes
122
guide a path of magnetism generated by the first and second magnets
117
and
119
to direct the bobbin
107
to a desired location.
Each of the wires
109
has one end soldered to a corresponding area of both the opposite and other side surfaces of the bobbin
107
and the other end connected to the holder
103
, and is electrically connected to a circuit portion (not shown) which applies current to the magnetic driving portion.
FIG. 2A
shows an example of the polarity of the first magnet
117
and the direction of current I to disclose the relationship of forces by the interaction between the focus coil
110
and the tilt coil
112
, and the first magnet
117
corresponding thereto. Here, the focus coil
110
provided at each of the opposite side surfaces
107
a
of the four side surfaces of the bobbin
107
receives a force F
f
by Fleming's left hand rule so that the bobbin
107
is moved in the focus direction L. Where the direction of the current I changes to the opposite, the focus coil
110
receives a force in the opposite direction L′.
The tilt coil
112
is provided at both opposite side surfaces
107
a
of the bobbin
107
, forms a couple with the corresponding focus coil
110
, and interacts with the corresponding first magnet
117
. Here, where the same currents flowing in the opposite directions are applied to the tilt coils
112
, the forces F
ti
received by the both tilt coils
112
become opposite so as to drive the optical pickup in the tilt direction, in particular, in the radial tilt direction (N).
FIG. 2B
shows an example of the polarity of the second magnet
119
and the direction of current I to disclose the relationship of forces by the interaction between the track coil
115
and the second magnet
119
corresponding thereto. The direction and magnitude of forces between a magnet and a coil is determined by Fleming's left hand rule. Thus, the track coil
115
provided at each of the other side surfaces
107
b
of the four side surfaces of the bobbin
107
, where the focus coils
110
and the tilt coils
112
are not arranged, receives the force F
t
in the track direction by the second magnet
119
so as to move the bobbin
107
in the track direction M. Here, where the direction of current I changes to the opposite, the track coil
115
receives a force in the opposite direction M′.
Typically, six wires
109
of the optical pickup actuator are provided to drive the bobbin
107
in the focus direction, the track direction, and the tilt direction. But, more wires may be needed for a four axes driving actuator.
However, since the optical pickup actuator is very small, where all four side surfaces of the bobbin
107
are used to install the focus coils
110
, the track coils
115
, or the tilt coils
112
, a sufficient space may not be present to install the wires
109
. In addition, when the number of the wires
109
increases, it is very difficult to attach the additional wire(s) in such a small space. Accordingly, the defective ratio of the conventional optical pickup actuators increases.
Also, when coils are arranged using all four side surfaces of the bobbin
107
, wiring of the coils is complicated. Furthermore, since a magnet is provided at each of the focus coil
110
, the tilt coil
112
, and the track coil
115
, the number of parts constituting the optical pickup actuator increases, decreasing the productivity. Additionally, interference with a spindle motor (not shown), which rotates a disc, is generated by the first magnet
117
arranged at the opposite side surfaces (left and right sides) of the bobbin
107
. Therefore, the spindle motor is not accurately controlled.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an apparatus and a method of driving an optical pickup actuator in which a focus and tilt coil and a track coil which drive an objective lens in the focus direction, the track direction, and the tilt direction are arranged at both side surfaces of a bobbin so as to secure a sufficient space provided at the other side surfaces of the bobbin, wherein driving in the focus direction and the tilt direction can be controlled together by a single coil.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and other objects of the present invention, there is provided a method of driving an optical pickup actuator havi
Shin Kyung-sik
Song Byung-youn
LandOfFree
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