Coherent light generators – Particular temperature control – Heat sink
Reexamination Certificate
2002-10-18
2004-12-28
Wong, Don (Department: 2828)
Coherent light generators
Particular temperature control
Heat sink
C372S044010, C372S050121
Reexamination Certificate
active
06836491
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor laser device which is provided in an optical pickup apparatus used to record or reproduce information on or from an optical recording media.
2. Description of the Related Art
A semiconductor laser device is installed in an optical pickup apparatus and used to record or reproduce information on or from an optical recording media.
FIGS. 11A and 11B
are simplified perspective views showing the construction of a semiconductor laser device
1
of the prior art. In the semiconductor laser device
1
, a semiconductor laser chip
4
is mounted on one surface
3
of a first member
2
which is shaped into a circular disc and made of metal, and a heat sink
5
which efficiently diffuses heat generated when the semiconductor laser chip
4
emits a laser beam and a photodiode
6
which receives part of a light beam emitted from the semiconductor laser chip
4
and monitors laser output are firmly attached to each other by a die bond.
Optical output of the semiconductor laser chip
4
detected by the photodiode
6
is inputted to an APC (automatic power control), which is a system controller provided with a CPU (central processing unit) not shown in the drawings. The APC responds to optical detection output and controls a driving current of the semiconductor laser chip
4
, thereby keeping output of the semiconductor laser chip
4
constant.
The semiconductor laser chip
4
and the photodiode
6
are electrically connected by wires
9
made of metal to lead pins
8
. The lead pins
8
are fixed to the first member
2
and their surfaces are insulated by glass sealing parts
7
. A hollow second member
15
made of metal is disposed so as to cover the semiconductor laser chip
4
. The second member
15
is shaped like a cylinder having a bottom so as to have a peripheral wall
14
of a cylindrical shape and an end wall
13
which blocks a base end
12
of the peripheral wall
14
. Accordingly, an opening
11
is formed on an open end
10
of the second member
15
. To the end wall
13
of the second member, a laser beam emitting glass window
16
is disposed. At the open end
10
of the second member
15
is formed a flange
10
a
which protrudes radially outward from the circumference of the peripheral wall
14
. The second member
15
is joined to the first member
2
by resistance welding in a state where an end face
17
of the flange
10
a
of the open end
10
abuts onto the one surface
3
of the first member
2
.
At the time of attaching the semiconductor laser device
1
to an optical pickup apparatus, the one surface
3
of the first member
2
is made to adhere to an attachment face of the optical pickup apparatus, and fixed by a resin or the like after angular displacement of the semiconductor laser device
1
is made and a mounting position is adjusted so that a light beam emitted from the semiconductor laser chip
4
is focused in an appropriate position on an optical recording media. In an optical pickup apparatus provided with the semiconductor laser device
1
, a light beam focused and reflected on an optical recording media is diffracted by a beam splitter or the like and focused on a signal reading photodiode, where signals are detected.
In cases where an optical pickup apparatus provided with a semiconductor laser device is installed in a portable optical disc player and the like, a semiconductor laser device is required to be small and lightweight for portable use. Another prior art for realizing miniaturization of a semiconductor laser device is disclosed in Japanese Unexamined Patent Publication JP-A 6-5990 (1994).
FIGS. 12A and 12B
are simplified perspective views showing the construction of another semiconductor laser device
18
of the prior art. The semiconductor laser device
18
is characterized in that the projected shape onto the plane parallel to one surface
20
of a first member
19
is substantially elliptic. More specifically, in the first member
19
, a part not used to mount the semiconductor laser chip
4
and so on is removed, whereby the device is miniaturized so as not to wastefully occupy a space when installed in an optical pickup apparatus or the like.
On one surface
20
of the first member
19
having a substantially elliptic shape, a heat sink
22
on which the semiconductor laser chip
4
and a signal reading photodiode
21
are mounted and the laser output monitoring photodiode
6
are firmly attached by a die bond.
A second member
23
is shaped like a cylinder having a bottom so as to have a peripheral wall of a substantially elliptic shape and an end wall
24
which blocks a base end of the peripheral wall. A laser beam emitting glass window
25
is disposed to an end wall
24
of the second member
23
. A hologram device
26
is firmly attached on the laser beam emitting glass window
25
by an epoxy resin. The hologram device
26
is set and fixed so that, in order to obtain desired signals from reflection light from an optical recording media, diffracted reflection light is received in an appropriate position on the signal reading photodiode
21
.
Also in this semiconductor laser device
18
of the other prior art, at an open end of the second member
23
is formed a flange
27
a
which protrudes radially outward from the circumference of the peripheral wall. The second member
23
is joined to the first member
19
by resistance welding in the state where an end face
28
of the flange
27
a
of the open end
27
abuts onto the one surface
20
of the first member
19
.
Moreover, at the time of measuring characteristics such as threshold current values, oscillation modes and the like of the semiconductor laser devices
1
,
18
, the semiconductor laser devices
1
,
18
are mounted on a mounting portion of a measurement apparatus at the one surfaces
3
,
20
of the first members
2
,
19
, whereby each measurement is done.
The semiconductor device
1
of the aforementioned prior art and the semiconductor laser device
18
of the other prior art have the following problems.
As described before, the first members
2
,
19
provided in the respective semiconductor laser devices
1
,
18
are joined to the second members
15
,
23
by resistance welding at the one surfaces
3
,
20
. In resistance welding, spatters, which are droplets of molten metal, are generated frequently, and when spatters are generated, the spatters fuse with the one surface, or even when not fuse, because of collisions of the spatters, rough and large irregularities are formed at collision spots on the one surface. There is such a problem that after the second member and the first member are joined together, when the first member is attached to an attachment portion of, for example, an optical pickup apparatus or a measurement apparatus at the one surface of the first member, the spatters fusing on the one surface of the first member and the rough and large irregularities formed thereon worsen attachment precision to the apparatus.
Moreover, although it can be thought to mount to an apparatus by making the first member larger and using a rim portion of the first member, which is rarely influenced by spatters due to resistance welding, as one means for solving the problem on the one surface caused by resistance welding, there is such a problem that in cases where the device is used in an optical pickup apparatus installed in a portable optical disc player and the like as described before, the device becomes larger by making the first member larger, and handiness and portability of a portable optical disc player are impaired.
SUMMARY OF THE INVENTION
An object of the present invention is to provide semiconductor laser device which can be attached to a desired apparatus with precision by preventing roughness of a surface of a joint member due to welding.
The invention provides a semiconductor laser device, comprising:
a semiconductor laser chip for emitting a laser beam;
a first member on which the semiconductor laser chip is mounted, the first member having one s
Nguyen Dung (Michael) T
Sharp Kabushiki Kaisha
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