Coherent light generators – Particular active media – Gas
Reexamination Certificate
1999-06-28
2001-03-27
Scott, Jr., Leon (Department: 2881)
Coherent light generators
Particular active media
Gas
C372S055000, C372S029011, C372S081000, C372S034000
Reexamination Certificate
active
06208676
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an axial flow gas laser oscillator of which axial directions of a discharge tube and a laser beam coincide with each other.
BACKGROUND OF THE INVENTION
A conventional axial flow gas laser oscillator is described hereinafter with reference to drawings.
FIG. 10
shows a schematic diagram of the construction of a conventional gas laser oscillator. In
FIG. 10
, discharge tubes
1
are made of an insulator such as glass and have anodes
2
and cathodes
3
disposed in the interior thereof. High-voltage direct current or HVDC power supplies
4
are connected to the anodes
2
and the cathodes
3
, and apply a voltage, for example 30KV, between the anodes
2
and the cathodes
3
. Discharge spaces
5
exist within the discharge tubes
1
across the anodes
2
and the cathodes
3
. Connecting tubes S are made of an insulator such as glass and a total reflection mirror
6
and a partial reflection mirror
7
are connected to the discharge tubes
1
on the cathodes
3
side via the connecting tubes
8
. A laser beam
9
(an arrow) is output from the partial reflection mirror
7
. The other arrows
10
indicate the flow direction of the laser gas circulating within the axial flow gas laser oscillator. A blower
11
forces the laser gas to flow in the axial direction of the discharge tubes
1
. Heat exchangers
12
cool the laser gas which has been warmed up by an electric discharge in the discharge spaces
5
and the blower
11
. The blower
11
effects a flow speed of the gas of approximately 200 m/sec in the discharge spaces
5
. A gas outlet pipe
13
made of an insulator exhausts the laser gas from the anodes
2
side of the discharge tubes
1
, and forms a part of a circulation route of the laser gas. Gas inlet pipes
14
made of an insulator supplies the laser gas from the cathodes
3
side of the discharge tubes
1
, and form a part of the circulation route of the laser gas. The anodes
2
are disposed in the center of a resonator and is applied with a high voltage. The cathodes
3
are disposed, one on each end of the resonator without being grounded, so as to maintain the balance of the discharge current of a plurality of discharge tubes. As a result, the potential of the cathodes
3
is constantly high during operation. Therefore, an electrical insulation distance in a laser gas atmosphere must be maintained between the cathodes
3
and grounded heat exchangers
12
as well as between the cathodes
3
and the total reflection mirror
6
and the partial reflection mirror
7
. To secure this, a gas outlet pipe
13
and gas inlet pipes
14
, both made of an insulator are disposed between the cathodes
3
and the heat exchangers
12
, and connecting tubes
8
also made of an insulator is disposed between the cathodes
3
and total reflection mirror
6
and partial reflection mirror
7
.
The construction of the conventional axial flow gas laser oscillator has been described above.
Next, the operation of the conventional axial flow gas laser oscillator is described.
A high voltage is supplied across the anodes
2
and cathodes
3
by the HVDC power supplies
4
to generate a glow-discharge in the discharge spaces
5
. The laser gas flowing through the discharge spaces
5
gets excited by gaining this discharge energy. The excited laser gas then is optically resonated by an optical resonator comprising the total reflection mirror
6
and partial reflection mirror
7
, and the laser beam
9
is output from the partial reflection mirror
7
. The laser beam
9
is used for a wide range of laser beam machining applications.
With the construction described above, if the discharge is continued after impurities have been introduced into the laser gas flowing in the discharge tubes
1
or gas mixing ratio has been changed, the discharge in the discharge tubes
1
becomes unstable, resulting in wide fluctuation of the potential of the cathodes
3
. A fluctuation in the potential of the cathodes
3
allows a micro discharge current to flow in the laser gas inside the connecting tubes
8
thereby degrading the total reflection mirror
6
and the partial reflection mirror
7
employed as internal mirrors of the resonator.
The present invention aims at solving the problem mentioned above and to provide a gas laser oscillator which realizes a stable laser beam mode and laser output for a long time.
SUMMARY OF THE INVENTION
The gas laser oscillator of the present invention comprises such elements as: discharge tubes; power supplies for supplying energy to the discharge tubes; internal mirrors of the resonator disposed in the discharge tubes; detecting means for detecting at least one of a micro discharge current flowing near the internal mirrors of the resonator and the physical phenomenon generated by the micro discharge current; a control circuit for controlling the energy to be supplied to the discharge tubes by responding to the output signals output from the detecting means.
According to the gas laser oscillator of the present invention, the energy to be input into the discharge tubes can be controlled by the control circuit by comparing the output signals output from the detecting means with reference signals. Therefore, the occurrence of the micro discharge current can be restricted, which in turn, prevents the degradation of the internal mirrors of the resonator caused by the micro discharge current.
REFERENCES:
patent: 3790899 (1974-02-01), Dessus et al.
patent: 4351052 (1982-09-01), Sasaki et al.
patent: 4573162 (1986-02-01), Bakowsky et al.
patent: 5426659 (1995-06-01), Sugiyama et al.
patent: 5450435 (1995-09-01), Yamane et al.
patent: 0 224 710 (1987-06-01), None
patent: 0 429 652 (1991-06-01), None
patent: 60-095984 (1985-05-01), None
patent: 60-171777 (1985-09-01), None
patent: 62-242377 (1987-10-01), None
Jr. Leon Scott
Matsushita Electric - Industrial Co., Ltd.
Ratner & Prestia
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