Four-axial driving actuator for optical pickup

Details Four-axial driving actuator for optical pickup Four-axial driving actuator for optical pickup

2001-08-24

2004-04-20

Edun, Muhammad (Department: 2655)

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

C369S044140, C359S823000

Reexamination Certificate

active

06724696

ABSTRACT:

CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Patent Application No. 2000-74796 filed on Dec. 8, 2000, in the Korean Industrial Property Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a four-axial driving actuator for an optical pickup, and more particularly, to a four-axial driving actuator for an optical pickup in which the winding starting ports of a focusing coil, tracking coil, and tilt coil are separate from one another and the winding end ports thereof are combined as a common ground so that moving characteristics of a bobbin are improved.
2. Description of the Related Art
In general, an optical pickup is a device employed in an optical recording/reproduction apparatus to record information on and/or reproduce information from a disc mounted as a recording medium on a turn table in a non-contact manner while moving in the radial direction of the disc. The optical pickup includes an objective lens that focuses a beam emitted from a light beam source to form a beam spot on the disc, and an actuator that controls the objective lens in the track direction, focus direction, and tilt direction such that the beam spot from the objective lens can be accurately focused on an intended position in the optical disc.
An actuator for an optical pickup is classified as either a hinged type, plate spring type, wire type, or an axial sliding type according to its bobbin support structure. The wire type is advantageous in that current can be supplied to a driving coil using a wire supporting the bobbin.
Referring to
FIG. 1
, a conventional wire-type optical pickup actuator includes a base
100
, a holder
103
fixed on the base
100
, a bobbin
107
to which the objective lens
105
is fixed, wires connected between the bobbin
107
and the holder
103
, and a magnetic driving unit driving the bobbin
107
in the track, focus or tilt direction.
The magnetic driving unit includes a first magnet
110
and a second magnet
112
, each facing a corresponding first and second magnet
110
and
112
, respectively, with the bobbin
107
therebetween, an outer yoke
115
which is mounted on the base
100
and to which the first magnet
110
is fixed, an inner yoke
117
mounted on the base
100
facing one of the first magnets
110
to guide the bobbin
107
, a focusing coil
120
wound around the outer wall of the bobbin
107
, a tracking coil
122
wound at the side wall of the bobbin
107
facing one of the first magnets
110
, and portions of a tilt coil
125
wound at each of the side walls of the bobbin
107
facing the second magnets
112
.
FIG. 2
is a front view of the bobbin
107
of FIG.
1
. Referring to
FIGS. 1 and 2
, the wires includes focusing coil wires
130
connecting the focusing coil
120
to the winding starting port
127
and the winding end port
129
thereof, tracking coil wires
135
connecting the tracking coil
122
to the winding starting port
132
and the winding end port
133
thereof, and tilt coil wires
140
connecting the tilt coil
125
to the winding starting port
137
and the winding end port
139
thereof. The wires
130
,
135
, and
140
serve as a support for the bobbin
107
driven by the magnetic driving unit by connecting the bobbin
107
to the holder
103
, as well as serving as electric wires through which current is applied to the focusing coil
120
, the tracking coil
122
, and the tilt coil
125
.
A general actuator includes four wires including a pair of focus coil spring wires
130
and a pair of tracking coil spring wires
135
. In addition, tilt coil spring wires may be elastically connected between the bobbin
107
and the holder
103
to support the bobbin
107
, further elastically biasing the bobbin
107
toward the holder
103
. As a result, motion of the bobbin
107
is further limited. Taking into account this problem, the tilt coil wires
140
are arranged loosely over the holder
103
and connected to the rear wall of the holder
103
, as shown in FIG.
1
.
The bobbin
107
is driven by the magnetic driving unit having the configuration above in four axial directions, i.e., in the focus direction A, track direction B, tangential tilt direction C, and radial tilt direction D.
FIG. 3
shows a voltage apply circuit for each of the coils. Although the circuit for only the focusing coil
120
is illustrated here, the tracking coil
122
and the tilt coil
125
have the same structure.
Referring to
FIG. 3
, the focus coil circuit includes an input generator
145
, comparators
147
, the winding starting port
127
of the focusing coil
120
to which a driving voltage is applied from one of the comparators
147
, and the winding end port
129
through which a current flowing through the focusing coil
120
is output. This circuit structure is also applied to both the tracking coil
122
and the tilt coil
125
, and thus a total six wires are needed for the actuator.
In the conventional four-axial driving actuator having the configuration above, the six wires are complexly arranged, and moving characteristics of the bobbin
107
are affected by the length or position of the tilt coils
125
, causing a secondary resonance or a rolling of the bobbin
107
to occur in driving the bobbin
107
.
SUMMARY OF THE INVENTION
To solve the above and other problems, it is an object of the present invention to provide a four-axial driving actuator for an optical pickup, in which the winding starting ports of a focusing coil, a tracking coil, and a tilt coil are separate from one another and the winding end ports thereof are combined as a common ground so that moving characteristics of a bobbin are improved.
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.
The foregoing objects of the present invention are achieved by providing a four-axial driving actuator for an optical pickup, comprising: a base; a holder fixed on the base; a bobbin to which an objective lens is fixed; spring wires connected between the bobbin and the holder; and a magnetic driving unit driving the bobbin in the focus, track, or tilt direction with a focusing coil, a tracking coil, and a tilt coil, wherein the magnetic driving unit comprises a circuit unit including winding starting ports for the focusing coil, tracking coil, and tilt coil, and a common ground port at which winding end ports for the focusing coil, tracking coil, and tilt coil are grounded, and the circuit unit applies a voltage to the focusing coil, tracking coil, and tilt coil.
The magnetic driving unit may comprise a first magnet and a second magnet, each facing a corresponding first and second magnet, respectively, with the bobbin therebetween; an outer yoke which is mounted on the base and to which a first magnet is fixed; and an inner yoke mounted on the base facing the first magnet to guide the bobbin, wherein the focusing coil is wound around the outer wall of the bobbin, the tracking coil is wound at the side wall of the bobbin facing the first magnet, and the tilt coil is wound at the side wall of the bobbin facing the second magnet. It is to be noted that the positioning of the magnets, and also the number of magnets used shall not be limited by this description, but may vary such that the desired effect is obtained.
The circuit unit may also comprise an input generator to generate a voltage to be applied to the focusing coil, tracking coil, or tilt coil; and a filter that removes a high-frequency noise component from the voltage applied from the input generator to supply a noise-free voltage to the focusing coil, tracking coil, or tilt coil. In the alternative, a separate input generator may be provided for each of the focusing coil, tracking coil, and tilt coil.


REFERENCES:
patent: 6091553 (2000-07-01), Song et al.
patent: 6501710 (2002-12-01), Yokoyama et al.
patent: 6507554 (2003-01-01), Son

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