JP2656362B2 - Laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention applies a high-frequency voltage between a high-voltage side electrode and a low-voltage side electrode by a high-frequency power supply, and separates a high-frequency voltage across a dielectric. The present invention relates to a laser device for performing the above.

(Prior art) Laser gas pressure of 10 to used for various laser processing
FIG. 4 shows an example of a laser device for generating a high-frequency discharge at about rr to 200 torr to excite a laser. The fourth
The figure shows a high-frequency power supply and a laser oscillation unit. That is,
The high-frequency power supply 1 is composed of an excitation unit 2 and a power amplifier unit 3 and has a frequency f (normally 13.56 Hz) generated by the excitation unit 2.
The high-frequency power (± 2 KHz) is amplified by the power amplifier unit 3 and supplied to the high-voltage side electrode 6a of the laser discharge unit via a matching unit 5 for impedance matching by a coaxial cable 4 having a characteristic impedance of 50Ω. On the other hand, the low voltage side electrode 6b is grounded.

The high-frequency voltage supplied between the high-voltage side electrode 6a and the low-voltage side electrode 6b is applied to the dielectric 7a disposed adjacent to each electrode.
And 7b to the laser gas to generate a high-frequency discharge 8. Although not shown in the figure, a laser gas is supplied between the dielectrics 7a and 7b in order to prevent a gas temperature rise due to the high-frequency discharge. Further, by arranging a reflecting mirror 9 and a partial reflecting mirror 10 with the high-frequency discharge 8 interposed therebetween to constitute a laser resonator, laser oscillation is performed and laser light 11
Are configured to obtain When the laser beam 11 needs to be modulated, a pulse modulation signal 12 may be sent to the excitation unit 2 from outside.

On the other hand, the power amplifier unit 3 includes a vacuum tube 13 for amplifying a high-frequency signal and a capacitor for adjusting an output impedance.
C ₁ , C ₂ and inductance L ₁ , said vacuum tube 1
A high DC voltage for operating the vacuum tube is applied to _{3, and} a capacitor C3 for preventing this DC component from passing to the high-frequency output side is connected. The matching device 5 for impedance matching is an inverted L type,
It is formed of a variable capacitor C ₄ and the inductance L _2.

(Problems to be solved by the invention) However, in the conventional laser device having the above-described configuration, there are problems to be solved as described below.

That is, the discharge resistance changes with a change in the discharge input, causing a mismatch with the output impedance of the high-frequency power supply 1, and accordingly, reflected wave power is generated and adversely affects the high-frequency power supply 1. Further, although the conventional laser device has very excellent pulse control performance, the high-frequency power supply 1 itself is very expensive.

The present invention has been proposed in order to solve the above-mentioned drawbacks of the prior art. The purpose of the present invention is to reduce the mismatch of the circuit conditions with respect to the change of the discharge input and to reduce the reflected wave power to the high frequency power supply. An object is to provide an inexpensive laser device that can be suppressed.

[Configuration of the Invention] (Means for Solving the Problems) The present invention includes a high-voltage electrode and a low-voltage electrode arranged with a dielectric interposed therebetween, and generates a high-frequency discharge across the dielectric. In a laser device having a laser oscillation section, and a high-frequency power supply section for supplying high-frequency power between the high-voltage side electrode and the low-voltage side electrode of the laser oscillation section, the output impedance of the high-frequency power supply and the discharge in the laser oscillation section The impedance is set to a matching state in which reflected power does not return to the high-frequency power supply side, and as the high-frequency power supply,
The oscillation frequency uses a self-excited power supply having a predetermined amount of frequency fluctuation width, and the oscillation frequency of the self-excited power supply follows the increase / decrease of the discharge resistance due to the fluctuation of the discharge input from the high-frequency power supply in inverse proportion. The output impedance of the high-frequency power supply and the discharge impedance in the laser oscillation section are matched.

(Operation) Since the laser device of the present invention uses a self-excited power supply as the high-frequency power supply, the oscillation frequency fluctuates by about ± 10% in the vicinity of the oscillation frequency f determined by L and C in the oscillation circuit. Can be. Therefore, the frequency of the high-frequency power supply can be changed in accordance with the change in the discharge impedance depending on the discharge input, so that the irregular state with the discharge unit can be reduced.

(Example) Hereinafter, an example of the present invention will be specifically described with reference to FIG. The same members as those of the conventional type shown in FIG. 4 are denoted by the same reference numerals, and description thereof will be omitted.

As shown in FIG. 1, the laser device of this embodiment includes a self-excited high-frequency power supply and a laser oscillation unit (discharge unit). That is, the high-frequency oscillator 20 of the high-frequency power supply is composed of a Colpitts circuit that can easily extract the high frequency to the discharge load side by a transformer coupling, a vacuum tube (triode) 21 for oscillating the high frequency, and capacitors C ₅ and C that determine the oscillation frequency f. ₆
And it is configured from an inductance L ₃ which also serves as a coupling transformer and the load. A high DC voltage for operating the vacuum tube is applied to the vacuum tube 21.
Capacitor to prevent this DC component from passing to the high frequency output side
C ₇ is installed.

The high-frequency power having a frequency f (frequency variation of about ± 10%) generated by the high-frequency oscillation unit 20 is supplied to the high-voltage side electrode 6a and the low-voltage side electrode 6b of the laser discharge unit via the transformer coupling 22.
Is configured to be supplied. Here, under a certain discharge input condition (for example, a maximum discharge input), the transformer coupling 22 is designed to match the output impedance of the high-frequency oscillation unit 20 with the impedance of the laser discharge unit so that the primary side and the secondary side can be matched. The side turns ratio is adjusted.

At this time, the oscillation frequency f generated by the high-frequency oscillator 20 is In addition, the oscillation frequency f changes with a change in the discharge load, and has a function of reducing the reflected power due to the mismatch state.
Further, in the case of this embodiment, when pulse-modulating the laser light 11, a pulse-modulated signal
Just send 12.

The operation of the laser device of this embodiment having such a configuration will be described below.

That is, in the laser device of the present embodiment, the discharge resistance r as viewed from the load side of the transformer coupling 22 is expressed as the resistance value of the primary side in a relationship depending on the turns ratio of the primary side and the secondary side of the transformer. Can be. Therefore, considering the circuit of FIG. 1 equivalently, discharge resistance r of the secondary side can be regarded as a resistance component R which are connected in series to the inductance L ₃ of the primary side. That is, in the case of an ideal transformer, if the number of turns on the primary side and the number of turns on the secondary side are n ₁ and n ₂ respectively, then R = (n ₁ / n ₂ ) ² · r. At this time, the oscillation frequency f ₀ of the high-frequency oscillator 20 is
By considering the parallel resonance circuit, It is expressed as Therefore, the change in the discharge resistance r, the oscillation frequency f ₀ of the high frequency oscillation section 20 is seen to vary.

The effect of the present embodiment will be described with reference to FIGS. That is, in FIG. 2 showing the relationship between the discharge input and the discharge resistance r, the discharge resistor r increases with an increase in the discharge input of the high frequency discharge, and the third shows the relationship between the oscillation frequency f ₀ and the discharge resistance r. in the figure, it can be seen that the discharge resistor r is decreased by an increase of the oscillation frequency f _0. In this example, the discharge input was set to 1000 W and the oscillation frequency was set to 10 M
The discharge circuit is matched at Hz. For example,
At this time, when the discharge input is reduced, the discharge resistance r is reduced according to FIG. 2, but in the conventional laser device, since the oscillation frequency does not change, the matching state of the discharge circuit is not satisfied, The reflected power returns to the high frequency power supply,
This had an adverse effect on high frequency power supplies. However, in the present embodiment, a change in the oscillation frequency f ₀ in accordance with equation (2). That is, when the discharge resistance r decreases, the equivalent resistance value R
Since but decreases, increases the oscillation frequency f _0, as a result, high-frequency power supply itself acts so they can maintain a consistent state.
Specifically, in the present invention, the configuration of the circuit itself is such that the frequency Δf ₀ changes in accordance with the variation Δr of the discharge load, and the matching state is always maintained under the conditions. Therefore, as shown in FIG.
In the power supply according to the present invention, the frequency f _{0 is} changed as shown in FIG. 3 to satisfy the matching condition. Therefore, even if the discharge input is changed, the mismatch between the discharge unit and the high-frequency power supply can be reduced.

As described above, according to this embodiment, the mismatch state between the high-frequency discharge unit and the high-frequency power supply can be reduced, and the adverse effect on the high-frequency power supply due to the reflected power caused by the mismatch state can be eliminated. Further, since the configuration is simple, a high-frequency power supply for laser can be obtained at a lower price than a conventional high-frequency power supply.

Note that the present invention is not limited to the above-described embodiment, and similar effects can be obtained even if the automatic high-frequency power supply is configured using a semiconductor. Further, a matching device may be used in the load circuit on the secondary side.

[Effects of the Invention] As described above, according to the present invention, by using a self-excited power supply whose oscillation frequency changes with a load change of a high-frequency discharge as a high-frequency power supply, a change in discharge input can be prevented. In addition, it is possible to provide an inexpensive laser device that can mitigate mismatch of circuit conditions and suppress reflected wave power to a high-frequency power supply.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing one embodiment of a laser device of the present invention,
FIG. 2 is a diagram showing a relationship between a discharge input and a discharge resistance, FIG. 3 is a diagram showing a relationship between an oscillation frequency and a discharge resistance, and FIG. 4 is a circuit diagram showing an example of a conventional laser device. DESCRIPTION OF SYMBOLS 1 ... High frequency power supply 2 ... Excitation part 3 ... Power amplifier part 4 ... Coaxial cable 5 ... Matching device 6a ... High voltage side electrode 6b ... Low voltage side electrode 7a, 7b …… dielectric, 8…
... High frequency discharge, 9 ... Reflector, 10 ... Partial reflector, 11 ...
... Laser light, 12 ... Pulse modulation signal, 13 ... Vacuum tube, 20
… High-frequency oscillator, 21… Vacuum tube, 22… Transformer coupling.

Claims (1)

(57) [Claims] 1. A laser oscillating unit comprising a high-voltage side electrode and a low-voltage side electrode arranged with a dielectric material interposed therebetween, and generating a high-frequency discharge through the dielectric, and a high-voltage side of the laser oscillating unit. In a laser device having a high-frequency power supply for supplying high-frequency power between an electrode and a low-voltage side electrode, the output impedance of the high-frequency power and the discharge impedance of the laser oscillation unit are matched so that reflected power does not return to the high-frequency power. The state is set as the high-frequency power supply, and the oscillation frequency uses a self-excited power supply having a predetermined amount of frequency fluctuation width. The frequency is made to follow in inverse proportion so as to ensure a matching state between the output impedance of the high-frequency power supply and the discharge impedance in the laser oscillation section. The laser apparatus characterized by the.