Coherent light generators – Optical fiber laser
Reexamination Certificate
2000-06-22
2003-10-21
Ip, Paul (Department: 2828)
Coherent light generators
Optical fiber laser
C356S344000
Reexamination Certificate
active
06636535
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a laser apparatus and in particular to fiber adjustment of the laser apparatus.
A solid-state laser apparatus will be discussed as an example of the laser apparatus.
FIG. 10
is a schematic diagram to show an oscillator head and a laser beam path of a solid-state laser apparatus in a related art. Numeral
1
denotes an oscillator head, numeral
2
denotes a resonator, numeral
3
denotes a partial reflecting mirror, numeral
4
denotes a total reflecting mirror, numeral
5
denotes an excitation light source, numeral
6
denotes a solid-state component of an excitation medium, numeral
7
denotes a cavity (box) containing the excitation light source
5
and the solid-state component
6
, numeral
8
denotes a laser beam emitted from the resonator
2
, numeral
9
denotes a magnifying lens, numeral
10
denotes a collimating lens, numeral
11
denotes a beam shutter, numeral
12
denotes a reflecting mirror, numeral
14
denotes a damper, numeral
20
denotes a condensing lens, numeral
21
denotes a fiber holder, numeral
22
denotes a fiber incidence section having the condensing lens
20
and the fiber holder
21
, numeral
23
denotes an optical fiber, numeral
24
denotes a machining head, and numerals
25
a
and
25
b
denote machining lenses.
The operation of the described solid-state laser apparatus is as follows: In the laser apparatus in
FIG. 10
, the solid-state component
6
is excited by excitation light of the excitation light source
5
and the partial reflecting mirror
3
and the total reflecting mirror
4
placed so as to sandwich the solid-state component
6
cause lasing to occur. The laser beam
8
emitted from the resonator
2
is widened after passing through the magnifying lens
9
and becomes a collimated beam after passing through the collimating lens
10
, and the collimated laser beam is incident on the fiber incidence section
22
.
The beam shutter
11
is placed between the collimating lens
10
and the fiber incidence section
22
, so that the laser beam
8
can be shut off when it is not wanted to emit the laser beam
8
to the outside of the laser oscillator. The beam shutter
11
consists of the reflecting mirror
12
for reflecting the laser beam
8
and the damper
14
for absorbing the laser beam
8
and converting it into heat. The reflecting mirror
12
is movable. When the reflecting mirror
12
is at a position A, the laser beam
8
passes through the beam shutter
11
; when the reflecting mirror
12
is at a position B, the laser beam
8
,is reflected on the reflecting mirror
12
to the damper
14
. The surface of the damper
14
is formed of a laser beam absorber for converting energy of the laser beam
8
into heat. Although not shown, the damper
14
is water-cooled for releasing the amount of heat absorbed.
The collimated laser beam
8
incident on the fiber incidence section
22
is gathered by the condensing lens
20
in the fiber incident section, and is incident on an end face
23
i
of the optical fiber
23
held by the fiber holder
21
, and propagates in the optical fiber
23
. adjustment in an optical axis direction to match the optical axis direction position of the focus of the gathered laser beam
8
with the optical fiber incidence end
23
i
, and the fiber holder
21
is made movable for adjustment in a direction perpendicular to the optical axis to match the focus position with the center of the plane of the optical fiber incidence end
23
i.
The laser beam
8
passing through the optical fiber
23
is emitted from an emission end
23
o
of the optical fiber
23
connected to the machining head
24
. The laser beam
8
guided into the machining head
24
is gathered by the condensing lenses
25
a
and
25
b
and is used for machining, etc.
The fiber incidence section
22
is adjusted seeing the characteristic of the laser beam
8
emitted from the emission end
23
o
of the optical fiber
23
.
Generally, in the solid-state laseroscillator, the light quantity of the excitation light source
5
is changed to change oscillation output. That is, the heat energy given to the solid-state component
6
is changed and by extension optical heat distortion of the solid-state component
6
itself changes. Specifically, the solid-state component
6
is cooled from the periphery, thus the temperature of the center becomes higher than that of the periphery and the solid-state component
6
has remarkably a nature like a convex lens; the strength degree of the convex lens changes. In this kind of solid-state laser oscillator, the characteristic of the solid-state component
6
in the resonator as the lens changes, thus if the strength of the excitation light source
5
, namely, output of the laser beam
8
is changed, the propagation characteristic of the laser beam
8
emitted from the resonator
2
changes and consequently the optimum adjustment value of the fiber incidence section
22
changes.
Therefore, to make the above-described adjustment, it is necessary to cause 500-W lasing to occur to machine in 500 W in a laser oscillator of output equivalent used for actual machining, for example, rated output 500-W output; otherwise, the propagation characteristic of the laser beam
8
at the adjustment time differs largely from that at the actual machining time, and the reliability of the adjustment itself is impaired.
The above-described adjustment is made finally with the laser beam
8
of machining output of high output. When adjustment to the fiber incidence section
22
differs largely from the optimum position, if the laser beam
8
of high output is made incident on the fiber incidence section
22
suddenly, there is a possibility that the optical fiber
23
and any other part will be damaged. Then, the fiber incidence section
22
is adjusted in such low output as not to damage the optical fiber
23
or any other part and while output is increased gradually, adjustment of the fiber incidence section
22
is repeated. Finally, the adjustment is made in actual machining output, then is completed.
FIG. 11
shows a solid-state laser apparatus as an example of a laser apparatus in another related art. The laser apparatus differs from that previously described with reference to
FIG. 10
in beam shutter section structure. In the laser apparatus shown in
FIG. 11
, numeral
30
denotes a beam absorber and numeral
31
denotes a reflecting mirror. The reflecting mirror
31
has a little, for example, 0.2% passing characteristic, namely, reflects most of an incident laser beam
8
and allows some output to pass through. The laser beam
8
passing through is absorbed in the beam absorber
30
. The beam absorber
30
acts as a laser beam shield. It is placed so that the beam absorber
30
can be removed from the rear of the reflecting mirror
30
, so that the laser beam
8
passing through the reflecting mirror
31
can be made incident on a fiber incidence section
22
as required.
The operation of the laser apparatus shown in
FIG. 11
is as follows: To adjust an optical path in an oscillator shown in
FIG. 11
, the beam shutter is closed, namely, the reflecting mirror
31
is set to a position of B and the beam absorber
30
is removed, then the laser oscillator is made to laser in output equivalent to that at the actual machining time, for example, 500 W. Then, the laser beam
8
reflected on the reflecting mirror
31
is absorbed in a damper
14
and a laser beam of small output passing through the reflecting mirror, in the example, 500 W×0.2%=1 W is emitted from an oscillator exit, namely, a condensing lens
20
. At this time, input to a solid-state component
6
is equivalent to that at the actual machining time, thus optical heat distortion of the solid-state component
6
is equivalent to that at the actual machining time and therefore the propagation characteristic of the laser beam
8
emitted from a resonator is equivalent to that at the actual machining time.
At this time, the propagation characteristic of the laser beam
8
passing through the reflecting
Iwashita Yoshitaka
Otani Akihiro
Ip Paul
Mitsubishi Denki & Kabushiki Kaisha
Nguyen Dung
Sughrue & Mion, PLLC
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