Coherent light generators – Particular active media – Gas
Reexamination Certificate
1999-04-27
2003-12-16
Scott, Jr., Leon (Department: 2828)
Coherent light generators
Particular active media
Gas
C372S034000, C372S055000, C372S058000
Reexamination Certificate
active
06665327
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention concerns a gas laser assembly with at least one laser discharge tube with laser gas flowing through it in the flow direction, and in which at least one laser beam runs in the direction of the axis of the discharge tube, and at least one feed line for laser gas opens into the laser discharge tube through which the laser discharge tube is connected to a pressure source for laser gas, for example a laser gas pump, and the laser gas is introduced into the laser discharge tube.
In the case of a known generic gas laser arrangement, the a laser gas circulates by means of a laser gas pump. A heat exchanger is provided, both coming, between the laser gas pump and the laser discharge tube, i.e., in the feed line for the laser gas, and going, between the laser discharge tube and the laser gas pump. As a result, the laser gas that is heated inside the laser discharge tube when the laser arrangement is operating is cooled. The cooled laser gas is introduced into the laser discharge tube through a tubular section of the feed line, whose axis lies in a plane with the discharge tube axis and runs perpendicular to it.
Since the feed line extends at an angle to the laser discharge tube, at least with the tubular section described above, the laser gas entering the laser discharge tube experiences a deflection in its flow, namely with a deflection in the flow direction inside the discharge tube. Because of this, at least in the area of the laser discharge tube adjacent the opening to the feed line, when seen in cross section, the flow ratios for the laser gas introduced into the laser tube are uneven. This results in an uneven beam intensity profile, i.e., a non-uniform distribution of the power of the laser beam, over the cross section of the laser discharge tube.
This invention has set the goal of making an improvement in the distribution of the power of the laser beam over the cross section of the discharge tube.
SUMMARY OF THE INVENTION
The invention solves this problem in a gas laser arrangement of the type described at the beginning, by providing in the feed line to the laser discharge tube at least one spiral guide running about an open central cross section to the discharge tube. At least some of the laser gas is fed to the laser discharge tube through the spiral guide. By running at least some of the laser gas introduced into the laser discharge tube along a spiral guide path, especially in the area where the feed line opens into the laser discharge tube and in the section of the laser discharge tube adjacent that area, more uniform flow ratios for the laser gas are produced. In turn, this produces a distribution of the laser gas power over the discharge tube cross section that is relatively even. In addition, the spiral guide is characterized by the fact that a relatively long route for the laser gas is available with a small structural volume.
The invention offers a number of ways for making the spiral guide for the laser gas. Thus, the guide can be made by a corresponding machined spiral groove or channel for the guide track or by inserting a separate spiral-shaped guide element in the feed line. For example, it is conceivable to use a corresponding screw-shaped or spiral-shaped guide tube. as a spiral-type guide for the laser gas, the invention preferably has a corresponding open central portion aligned with the discharge tube for the laser beam. Because of its geometry, this type of guide channel is comparable to a guide thread or a section of a guide thread.
To achieve the desired guide effect with optimum results, the depth of this type of guide thread or channel is chosen so that it is relatively large. The invention provides that the depth of the guide channel be at least one fourth the inner diameter of the accompanying laser discharge tube.
Another version of the invention provides that the spiral-type guide for the laser gas have at least one corresponding guide spiral channel on the inner wall of the feed line for laser gas. The design and alignment of the guide spiral can influence the flow ratios produced.
One preferred embodiment of the gas laser arrangement in the invention is characterized by the fact that the spiral-type guide channel for the laser gas is provided in a guide tube forming the inside wall of at least one part of the feed line for the laser gas and disposed prior to the laser discharge tube in the direction in which the laser gas flows. The functional separation described between the laser discharge tube and the guide pipe makes sure that the laser gas flow, as soon as it reaches the area of the laser assembly in which the discharge takes place, is already optimized. It is also possible to combine guide tubes with different designs with the same laser discharge tube or to vary the flow ratios by corresponding alignment of the guide pipe in relation to the laser discharge tube to which it is connected.
To make the laser gas flow take the flow direction desired in the guide pipe along the shortest possible flow path, the invention provides that the guide tube have an inlet for the laser gas which is tangential to its cross section and the spiral guide channel in the direction in which the laser gas flows. The features mentioned prevent unwanted deflection and swirling when the laser gas enters the guide tube and thus create a condition which requires that the laser gas flow be guided over only a short distance for its alignment.
In this sense, another variation of the invention makes use of the feature that the inlet for the laser gas in the guide tube is designed as a tubular inlet line and the axis of the inlet line runs in the direction of the section of the spiral guide connected to the inlet line. This avoids unwanted unevenness of flow when the laser gas enters the guide tube which would, if necessary, make it difficult to produce optimized flow ratios in the laser discharge tube downstream from the guide pipe.
According to the invention, the spiral-type guide can be designed to be single-threaded. In one preferred embodiment, however, a multi-threaded spiral-type guide is provided.
The flow ratios produced can be influenced by the geometry of the spiral-type guide. Structurally very simple embodiments are produced when the spiral-type guide is designed with a constant diameter of the free cross section at the discharge tube of the laser beam and/or with a constant spiral pitch. When the diameter of the free cross section of the spiral-type guide is constant, the guide path takes a spiral course. But, as stated already above, the guide track can, if necessary, also have a spiral shape, and then the diameter of the free cross section of the spiral-type guide can change in the direction of the spiral axis. According to the invention, the spiral pitch can also be chosen so that it changes in the direction of the axis of the spiral.
Finally, it is an advantage for the flow ratios in the laser-discharge tube if—as also provided in the invention—the spiral axis of the spiral-type guide runs in the flow direction and preferably coincides with the discharge-tube axis.
REFERENCES:
patent: 4242646 (1980-12-01), Macken
patent: 4242647 (1980-12-01), Macken
patent: 4500998 (1985-02-01), Kuwabara et al.
patent: 4504954 (1985-03-01), Guers et al.
Henschler Detlef
von Borstel Michael
Jr. Leon Scott
Pepe & Hazard LLP
Trumpf GmbH & Co.
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