Optical: systems and elements – Lens – With support
Reexamination Certificate
2003-02-24
2004-08-31
Ben, Loha (Department: 2873)
Optical: systems and elements
Lens
With support
C359S813000, C359S824000, C369S044150, C369S044160, C369S244100
Reexamination Certificate
active
06785064
ABSTRACT:
The present disclosure relates to the subject matter contained in Japanese Patent Application No. 2002-047318 filed Feb. 25, 2002, which is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an objective lens unit for an optical pickup used in a compact disk (CD), a digital video disk (DVD), or the like, and a method of assembling an objective lens unit.
2. Description of the Related Art
As one of the techniques concerning an objective lens unit, one disclosed in JP-A-2000-348360 is conventionally known. As shown in
FIGS. 9 and 10
, this objective lens unit is comprised of a base frame
2
having a supporting shaft
1
provided uprightly on its center; a lens holder
3
for fitting a boss portion
3
a
formed in the center thereof to the supporting shaft
1
so as to be slidable along the direction of an axis O of the supporting shaft
1
and to be capable of oscillating about the axis O; a focusing coil
4
that is externally fitted on the boss portion
3
a
; a pair of tracking coils
5
respectively disposed on both side surfaces of the lens holder
3
; a pair of magnets
6
respectively disposed on both side portions of the base frame
2
with the lens holder
3
interposed therebetween; and a pair of magnets
8
respectively secured to a pair of yokes
9
respectively inserted in a pair of through holes
3
b
of the lens holder
3
. As the lens holder
3
is slid in focusing directions a and b along the axis O by energizing the focusing coil
4
, the focus of an objective lens
7
provided in the lens holder
3
is adjusted to a disk (not shown), and the lens holder
3
is oscillated in tracking directions c and d about the axis O by energizing the tracking coils
5
, to thereby follow a predetermined track of the disk.
To describe the assembling procedure, in a state in which the respective coils
4
and
5
are pressed against predetermined positions on the lens holder
3
, the respective coils
4
and
5
are energized to undergo self-heating, there by melting fusible coatings of the coils
4
and
5
. Subsequently, the energization is stopped to cool the fusible coatings, and the coils
4
and
5
are adhered and fixed to the lens holder
3
by the fusible coatings that is rehardened by that cooling.
In the above-described conventional construction, the thickness of the fusible coatings of the focusing coil
4
and the tracking coils
5
is thin, and the adhesiveness based on the fusible coatings is weak, so that the state in which the focusing coil
4
and the tracking coils
5
are adhered and fixed to the lens holder
3
is unreliable. For this reason, when the lens holder
3
is oscillated in the tracking directions c and d by energizing the tracking coils
5
, there is a possibility that the lens holder sways unexpectedly due to the resonance phenomenon and that the focus servo characteristic based on the focusing coil
4
becomes unstable.
It is conceivable to adhere the focusing coil
4
and the tracking coils
5
to the lens holder
3
by using an instantaneous adhesive. According to this method, however, since the strength of the instantaneous adhesive is small, the coils
4
and
5
are liable to peel off the lens holder
3
.
In addition, it is conceivable to adhere the focusing coil
4
and the tracking coils
5
to the lens holder
3
by using an ultraviolet-curing adhesive. According to this method, however, since the structure in which the coils
4
and
5
are mounted is complex, it is difficult to uniformly irradiate the entire portion with the ultraviolet rays, and the state of curing is liable to become uneven.
Further, it is conceivable to form pockets for accommodating the coils
4
and
5
on the lens holder
3
. According to this method, however, the shape of the lens holder
3
becomes complex due to the formation of the pockets, and the cost of a mold becomes expensive.
SUMMARY OF THE INVENTION
An object of the invention is to provide an objective lens unit that makes it possible to reliably fix a focusing coil and tracking coils at low cost, and to provide a method of assembling the objective lens unit.
To attain the above object, according to a first aspect of the invention, there is provided an objective lens unit comprising: a base frame having a supporting shaft provided uprightly on a center thereof; a lens holder having a boss portion formed in a center thereof and fitted to the supporting shaft so as to be slidable along a direction of an axis of the supporting shaft and to be capable of oscillating about the axis; a focusing coil externally fitted on the boss portion; a pair of tracking coils respectively disposed on both side surfaces of the lens holder, each tracking coil having a central hole; a pair of magnets respectively disposed on both side portions of the base frame with the lens holder interposed therebetween; reinforcing frame portions formed along an outer peripheral surface of each of the tracking coils by applying an epoxy resin adhesive to portions between the lens holder and the outer peripheral surface of each of the tracking coils; reinforcing core portions formed by filling the epoxy resin adhesive into the central hole of each of the tracking coils; and a reinforcing connecting portion formed by filling the epoxy resin adhesive into a gap defined by the lens holder, each of the tracking coils, and the focusing coil.
According to the above-described construction, by applying an epoxy resin adhesive to regions ranging from peripheries of each tracking coil to the focusing coil, a reinforcing frame portion is formed along an outer peripheral surface of each tracking coil, a reinforcing core portion is formed in a central hole of each tracking coil, and a reinforcing connecting portion is formed in a gap defined by the lens holder, each tracking coil, and the focusing coil. Consequently, since the tracking coils and the focusing coil are integrally connected securely to the lens holder, it is possible to reduce peaks of resonance of the lens holder when the lens holder is oscillated in tracking directions by energizing each tracking coil. Accordingly, the lens holder does not sway unexpectedly due to the resonance phenomenon in a conventional fashion, so that it is possible to stabilize the focus servo characteristic based on the focusing coil.
In addition, in forming the aforementioned reinforcing frame, reinforcing core portion, and reinforcing connecting portion, the epoxy resin adhesive is merely applied to regions ranging from peripheries of each tracking coil to the focusing coil. Since it is unnecessary to perform special processing with respect to the lens holder, the cost of a mold for the lens holder can be made low.
According to a second aspect of the invention, there is provided an objective lens unit comprising: a base frame having a supporting shaft provided uprightly on a center thereof; a lens holder having a boss portion formed in a center thereof and fitted to the supporting shaft so as to be slidable along a direction of an axis of the supporting shaft and to be capable of oscillating about the axis; a focusing coil externally fitted on the boss portion; a pair of tracking coils respectively disposed on both side surfaces of the lens holder; a pair of magnets respectively disposed on both side portions of the base frame with the lens holder interposed therebetween; and reinforcing frame portions formed along an outer peripheral surface of each of the tracking coils by applying an adhesive to portions between the lens holder and the outer peripheral surface of each of the tracking coils.
According to the above-described construction, since each of the tracking coils is firmly secured to the lens holder by the reinforcing frame portion formed along the outer peripheral surface of each tracking coil, it is possible to reduce peaks of resonance of the lens holder when the lens holder is oscillated in the tracking directions by energizing each tracking coil. Accordingly, the lens holder does not sway unexpectedly due to
Ben Loha
Funai Electric Co. Ltd.
Morgan & Lewis & Bockius, LLP
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