Coherent light generators – Particular active media – Gas
Patent
1990-04-18
1992-09-29
Epps, Georgia Y.
Coherent light generators
Particular active media
Gas
372 55, 372 64, 372 66, 372 83, H01S 303
Patent
active
051519160
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electric discharge tube for high-speed axial-flow discharge pumping type gas lasers utilizing a high-frequency electric discharge, and more particularly, to an electric discharge gas laser tube providing a laser light in a rectangular beam mode.
2. Description of the Related Art
Recent developments in high-power lasers and peripheral processing technologies have enabled a wider use of laser beams for welding metals and nonmetals and for surface treatment processes in industry. However, a circular beam mode cannot be used to obtain a uniform processing accuracy, and thus a rectangular beam mode is required for such applications.
FIG. 4 is a schematic illustration of a conventional electric discharge tube for a gas laser. In the Figure, 21 designates a discharge tube, 22a and 22b denote metal electrodes, and 23 designates a high-frequency power source which supplies a high-frequency power of 2 MHz to a fast-flowing laser gas 24 in a discharge tube 21, via the metal electrodes 22a and 22b.
The sectional form of a laser beam output from the gas laser discharge tube is circular, as designated by 24 in FIG. 5(a), and thus the transverse mode is approximately represented by a Gaussian mode as shown by 25 in FIG. 5(b).
Therefore, to carry out a welding and surface treatment processing (e.g., surface hardening), an operation is required to convert the circular beam mode to a rectangular beam mode, and usually this is effected by the use of a paraboloid converging mirror, called a segmented mirror, disposed at the end of a processing head. An example of this is disclosed in a Japanese Unexamined Patent Publication No. 63-77178.
The segmented mirror, however, is arranged such that a large number of small plane mirrors are disposed on a parabolic surface, and thus is very expensive due to its intricate shape.
SUMMARY OF THE INVENTION
In view of the disadvantages of the prior art described above, an object of the present invention is to provide an electric discharge tube for a gas laser in which the sectional form of an active medium region, which contributes to a laser oscillation, is made rectangular, thereby to provide a laser light in a rectangular beam mode.
To attain the above object, according to the present invention, there is provided an electric discharge tube for a gas laser in which a laser gas flow axis and a laser oscillation optical axis are coaxial, and a discharge direction for discharge pumping is perpendicular to those axes, characterized in that the internal sectional form of the discharge section perpendicular to the laser oscillation optical axis is made rectangular and that the internal diameter of the nondischarge section is made larger than the diagonal line of the discharge section.
The internal sectional form of the discharge section is made rectangular and the nondischarge section is formed with an internal diameter larger than that of the discharge section. The sectional form of a laser beam generated in the rectangular discharge region becomes substantially rectangular, and since the laser beam is output to the outside as it is, a substantially rectangular beam mode is obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1(a) is a schematic diagram of an electric discharge tube for a gas laser according to an embodiment of the present invention;
FIG. 1(b) is a side view of the discharge tube of FIG. 1(a);
FIG. 2(a) illustrates the sectional form of a laser beam provided by the gas laser discharge tube according to the embodiment of the present invention;
FIG. 2(b) is a diagram illustrating the transverse mode of the laser beam provided by the gas laser discharge tube according to the embodiment of the present invention;
FIG. 3 is a schematic diagram of a peripheral section incorporating the gas laser discharge tube according to the embodiment of the present invention;
FIG. 4 is a schematic diagram of a prior art gas laser discharge tube;
FIG. 5(a) illustrates the sectional form of a laser beam prov
REFERENCES:
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patent: 4126890 (1978-11-01), Fournier et al.
patent: 4373202 (1983-02-01), Laakman et al.
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patent: 4512021 (1985-04-01), Chenausky et al.
patent: 4620306 (1986-10-01), Sutter, Jr.
patent: 4703489 (1987-10-01), Ross
patent: 4785458 (1988-11-01), Kazumoto et al.
patent: 4862476 (1989-08-01), Yiming
Patent Abstracts of Japan, vol. 12, No. 420, (E-679) [3267], Nov. 8, 1988; & JP-A-63 158 886, (Fanuc Ltd.), Jan. 7, 1988.
Patent Abstracts of Japan, vol. 12, No. 234, (E-629) [3081], Jul. 5, 1988 & JP-A-63 27 077, (Fanuc Ltd.), Apr. 2, 1988.
Iehisa Nobuaki
Yamazaki Etsuo
Epps Georgia Y.
Fanuc Ltd.
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