JPH0318753B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a preliminary discharge type gas laser oscillation device.

[Technical background of the invention and its problems]

TEA, one of the gas laser oscillation devices
(Transversely Excited Atmospheric
Pressure) CO ₂ lasers and excimer lasers use a pressure higher than atmospheric pressure as the operating pressure of the laser gas medium, so pre-ionization means for uniform discharge generation is required. One such means uses corona discharge, which supplies charged particles and ultraviolet light. TEACO ₂ with corona discharge preionization means
An example of a laser is shown in FIG. That is, 1 is an airtight container in which a laser gas medium consisting of a mixed gas of CO ₂ , H ₂ , He, etc. is sealed and maintained at a pressure of around 1 atmosphere. Inside the container 1, in an atmosphere of a laser gas medium, a semicylindrical cathode 2 constituting a main discharge electrode and an anode 3 having substantially the same shape as the cathode 2 are arranged facing each other, and are connected to a power source 4 that supplies a pulse voltage. ing. On the surface of the cathode 2 facing the anode 3, several V-grooves 5 of equal pitch are provided parallel to each other in the longitudinal direction. Each of these V-grooves 5 is provided with a preliminary discharge electrode 8 having a structure in which a core wire 7 is housed within a glass pipe 6. Each of the preliminary discharge electrodes 8 is composed of a single piece or a plurality of pieces. The core wires of the preliminary discharge electrode 8 are combined into one wire and connected to the anode 3. Further, a peaking capacitor 9 is provided between the cathode 2 and the anode 3 in a short-circuited manner with a short lead wire.

In the above configuration, the number of preliminary discharge electrodes 8 is set to narrow the width of the main discharge portion. By the way, in such an arrangement of the pre-discharge electrodes, pre-ionization becomes stronger in the central part of the arrangement, and the current density in the main discharge region 10 also becomes higher in the central part. The intensity distribution of the laser beam obtained by such a main discharge action becomes a mountainous intensity distribution as shown in Figure 6, which causes problems such as uneven processing in marking and other laser processing. Ta.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a gas laser oscillation device that can adjust the current density of the main discharge part and obtain a laser beam with a flat intensity distribution.

[Summary of the invention]

In order to achieve the above object, the electric field strength or equivalent capacitance of the preliminary discharge electrodes arranged in multiple rows near the cathode is made smaller according to the central arrangement.

[Embodiments of the invention]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings showing the embodiment, parts corresponding to those in FIG. 4 are given the same reference numerals.

FIG. 1 shows a first embodiment of the present invention, in which the core wire 16 of the central pre-discharge electrode 15 is made thicker than the core wires 7 of the other pre-discharge electrodes 8. In FIG. FIG. 2 shows a second embodiment of the present invention, in which a preliminary discharge electrode 18 made of an insulating glass tube 17 with a thicker wall than the others is disposed in the center. Furthermore, FIG. 3 shows a third embodiment of the present invention, in which a preliminary discharge electrode 20, which surrounds the core wire 7 with a glass tube 19 having a larger diameter than the others, is similarly placed in the center. In addition to this, although not shown, it is not a dimensional change of the core wire or glass tube,
A preliminary discharge electrode having a structure in which a core wire is surrounded by an insulator having a low dielectric constant may be placed in the center.

In any of the above embodiments, the main discharge area 1
At 0, the preliminary ionization at the center is weakened, and even when a main discharge occurs, a main discharge is generated in which the center is weakened and the periphery is strengthened. As a result,
As shown in FIG. 4, a laser beam having a trapezoidal energy distribution 21 is obtained.

By the way, the following factors can be considered to cause the strength of preliminary discharge to vary. That is, the first is the electric field strength at the time of preliminary discharge occurrence. The electric field strength becomes weaker as the core wire becomes thicker, and as the starting voltage for pre-discharge generation increases, pre-ionization becomes inactive. In the first embodiment, the core wire 16 was a copper wire with a diameter of 1 mm, and the diameter was set to 0.5 mm. The second is to adjust the equivalent capacity of the preliminary discharge electrode. Letting the thickness d, outer diameter b, and dielectric constant of the preliminary discharge electrode be ε, the equivalent capacitance C is given by the following equation.

C=2πε/log(b/b−d) Here, the equivalent capacitance C becomes smaller by increasing the wall thickness d, increasing the outer diameter b, and decreasing the dielectric constant q. When the equivalent capacitance C becomes smaller, when the same voltage V is applied, the amount of charge Q (=CV) stored in the equivalent capacitance C becomes smaller, the number of electrons supplied by pre-discharge decreases, and the pre-ionization decreases. become weak.
In this example, Pyrex glass is used as the insulator.
Glass tubes such as quartz glass and electrical lead glass (ε=
4-8) and alumina pipe (ε=~8), and the outer diameter and wall thickness are 3-5 and 0.8, respectively.
A material with a diameter of about 2 mm was used.

In this example, a groove is provided on the surface of the cathode, and a pre-discharge electrode is embedded in this groove. Similar effects can be obtained when a similar preliminary discharge electrode is arranged on the back surface.

In addition, as the core wire of the preliminary discharge electrode, diameters of 0.5 and 1
Although we have shown an example using copper wire with a diameter of 1 mm, metal wires other than copper wire (Mo, W, Ni, Al, Fe, etc.), thin wires with a diameter of 0.5 mm or less, and thick wires with a diameter of 1 mm or more may be used. The same effect can be obtained when using

In this example, examples were shown in which Pyrex glass, quartz glass, electrical lead glass, and alumina pipes were used as insulator pipes of available sizes, but the same effect can be obtained even if inorganic materials other than the above are used. It will be done.

〔Effect of the invention〕

Since laser light with a uniform intensity distribution can be obtained, unevenness in processing such as marking has been eliminated, and processing with high energy utilization efficiency has become possible.

Furthermore, the good utilization effect of the laser beam allows the required processing with relatively low energy, and the requirements for the fracture threshold of the coating surface of the output mirror are relaxed, leading to the durability of the output mirror.

On the other hand, the laser output energy is proportional to the amount of charge stored in the main capacitor of the power supply circuit, but if the desired processing can be performed with a low laser output energy, the capacitor capacity, charging power supply, and voltage capacity can be saved and the size can be reduced. At the same time, the demands on switch elements such as gear switches and thyratrons are also relaxed.

[Brief explanation of the drawing]

1 to 3 are side views of main parts showing an embodiment of the present invention, FIG. 4 is an energy distribution diagram of the laser beam obtained by the present invention, and FIG. 5 is a configuration diagram showing a conventional example.
FIG. 6 is an energy distribution diagram of laser light obtained in a conventional example. 2...Cathode, 3...Anode, 8, 15, 18, 2
0... Preliminary discharge electrode, 10... Main discharge area.

Claims (1)

[Claims] 1. an airtight container enclosing a gas laser medium; a pair of main discharge electrodes each having a substantially flat plate shape with curved edges and disposed opposite to each other in the airtight container;
A main discharge area is provided with a plurality of preliminary discharge electrodes arranged at least on one discharge surface of the main discharge electrode at a pitch forming a continuous main discharge area, and facing the other discharge surface of the main discharge electrode and performing corona discharge. A gas laser oscillation device that performs pre-ionization to generate a main discharge to perform pulsed laser oscillation, characterized in that the equivalent capacity of the pre-discharge electrode at the center of the arrangement is smaller than the equivalent capacity of the other pre-discharge electrodes. Gas laser oscillation device.