JPH0349275A - High frequency discharge excitation laser oscillator - Google Patents

Abstract

PURPOSE:To improve detection accuracy of discharge extinction by detecting change in the ratio of values of current which flowing on two lines which connect a high frequency power source and an electrode of a discharge tube. CONSTITUTION:A current value of lines 3a, 3b which connect a high frequency power source 2 and electrodes 4a, 4b of a discharge tube 4 is measured by current measuring circuits 6a, 5b and measured values Ai, Bi are input to an operation device 6 and a current rate operating circuit 8. The operating device 6 compares set values Ri of an output set circuit 7 with Ai to control a dc power source 1. A circuit 8 operates a ratio K of measured values Ai, Bi. The ratio K is nearly 1 during discharge; however, it increased because of a stray capacity C when discharge is extinguished. Therefore, when a ratio K is larger than a set value Kr stored in a memory 9 as compared by a comparison circuit 10, an alarm signal CSa is output to stop operation of the power source 1. Thereby, it is possible to improve detection accuracy of discharge extinction and to prevent breakdown of a high frequency power source.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a high-frequency discharge-excited laser oscillator that supplies high-frequency power to a discharge tube to perform ray → r oscillation, and particularly relates to a high-frequency discharge-excited laser oscillator that performs ray → r oscillation by supplying high-frequency power to a discharge tube. Regarding laser beam oscillators.

[Conventional technology]

Generally, in a high-frequency discharge-excited laser oscillator, a discharge current is detected and fed back to a high-frequency power source for laser gas excitation, and the current is controlled by comparing it with a command value to control the laser output.

On the other hand, in this type of laser oscillator, the discharge may disappear during the base discharge due to an abnormal increase in gas pressure inside the discharge tube. When the discharge disappears, the terminal voltage of the high-frequency power supply increases due to the rise in the impedance between the electrodes of the discharge tube. However, if an attempt is made to increase the discharge current by accidentally receiving a laser output command while the discharge is extinguished, the high-frequency power supply The output voltage may further rise abnormally and the internal semiconductor components may be destroyed.

For this reason, for example, an alarm signal is generated by detecting a voltage increase when the discharge disappears, and subsequent laser output commands are not received.

[Problem to be solved by the invention]

However, in reality, the voltage at the time of extinction of the discharge shows different values due to variations in the discharge tube, etc., so the threshold must be changed accordingly, making the adjustment complicated and causing problems with the accuracy of the alarm. was there.

The present invention has been made in view of these points, and an object of the present invention is to provide a high-frequency discharge-excited laser oscillator with improved detection accuracy of discharge extinction.

[Means for Solving the Problems] In order to solve the above problems, the present invention provides a high-frequency discharge-excited laser oscillator that supplies high-frequency power to a discharge tube to generate laser oscillation, in which one terminal is connected to the first line. A high frequency waveform connected to one electrode of the discharge tube, the other terminal of which is grounded to a predetermined ground point, and connected to the other electrode of the discharge tube via a second line from the ground point, and supplies the high frequency power. A power supply, a first current measurement circuit that measures the current value of the first line, a second current measurement circuit that measures the current value of the second line, and measurement of the first current measurement circuit. An arithmetic circuit that calculates the ratio between the current value and the all constant value of the second current measuring circuit.The value of the ratio is compared with a set value, and if it is outside the range defined by the set value, the discharge tube is in a state of discharge extinguishment. A high frequency discharge excitation laser oscillator is provided, characterized in that it has a comparison circuit that outputs a predetermined alarm signal indicative of .

[Effect]

Since one of the lines connecting the high frequency power source and the electrode of the discharge tube is grounded, a certain amount of stray capacitance exists only between the other non-grounded electrode and the ground. However, this stray capacitance is very large compared to the impedance between the electrodes during discharge, and during discharge the ratio of the current flowing through each line (current between the non-grounded electrode and the high frequency The ratio of currents in the lines connecting the power sources is approximately 1.

On the other hand, when the discharge disappears, the impedance between the electrodes of the discharge tube increases, so the current flowing through the stray capacitance cannot be ignored, and the current ratio increases. A change in this current ratio is detected and an alarm signal is output.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 is a hardware configuration diagram of a high frequency discharge excitation laser oscillator according to an embodiment of the present invention. In the figure, a DC power source 1 converts AC power from a commercial power source (not shown) into DC power and sends it to a high-frequency electric anchor 2. The high frequency power supply 2 generates a high frequency voltage V of, for example, 2M[(z) by switching it.

The output terminal 2a of the high frequency power source 2 and the electrode 4a provided on the surface of the discharge tube 4 are connected by a line 3a. Further, the output terminal 2b is grounded to a ground point PC via a line 3c, and is connected from this ground point Pe to the other electrode 4b of the discharge tube 4 via a line 3b. When a high frequency voltage V is applied between both electrodes through these lines, a discharge is generated inside the discharge tube 4, and a laser gas (not shown) circulating inside at high speed is excited to generate laser light.

Further, the current value of the line 3a is measured by the current IJll+constant circuit 5a, and the measured value A1 is manually inputted to the calculator 6. The calculator 6 calculates the difference between the set value Ri from the output setting circuit 7 and the measured value A1, and instructs the DC power source 1 to output the actual DC output based on this difference.

Therefore, the discharge current in the discharge tube 4 is controlled to approximately the set value R, and a laser output is generated in accordance with this current value.

On the other hand, the current value of the line 3b is measured by the current measuring circuit 5b, and the measured value Bi is input to the current ratio calculation circuit 8 together with the measured value Ai from the current measuring circuit 5a.

By the way, since the line 3b is grounded, there is a stray capacitance C of, for example, several p farads between the electrode 4a and the ground, and therefore, the current value of the line 3a and the current value of the line 3b are equal to each other. The only difference is the current. This relationship will be explained with reference to FIGS. 2(a> and 2(b)).

FIG. 2(a) is an equivalent circuit of the connecting portion of the discharge tube 4 during discharge. In the figure, an impedance 210 during discharge and an impedance Zc of a stray capacitance C are connected in parallel to the electrode 4a, and a current ral flows through the line 3a. The ground side electrode 4b is connected to the ground point Pe by a line 3b, and a current 1bl flows through the line 3b.

Note that the impedance 210 during discharge is, for example, several Ω, which is sufficiently smaller than the impedance 2C of the stray capacitance C. Therefore, the ratio Kl of the current 1bl and the current 1al is Kl = Ia1/Ib1- Z10/
(Z10+Zc) 1 .

On the other hand, when the discharge disappears, the impedance between the electrodes 4a and 4b increases to a value of 220, which is about the same as the impedance Zc, as shown in FIG. 2(1)). Then, the current ratio of 2 at this time becomes K2=Ia2/rb2 220/(Z20+Zc) 1 +220/Z c , which is larger by 220/Zc than the current ratio of 2 during discharge.

Returning to FIG. 1, the current ratio calculation circuit 8 manually calculates the ratio K (Ai/Bi) of the measured values Ai and B1. The comparison circuit 10 compares the ratio K with the set value K' stored in the memory 9, and generates an alarm signal C3a if it is larger than the set value Kr.Then, the control circuit 11 receives the alarm signal C3a as input. By being
The operation of the DC power source 1 is stopped, and thereby the high frequency power source 2 is also stopped.

In the above description, the operation of the DC power supply 1 is stopped by the alarm signal C3a, but at the same time, for example, an alarm indicating extinction of the discharge may be displayed on the display device.

[Effects of the Invention] As explained above, in the present invention, the extinction state of the discharge is determined based on the change in the ratio of the current value of the line on the ground side connected to the electrode of the discharge tube and the current value of the line on the non-ground side. Since it detects
There is no need to change the threshold value depending on variations in discharge tubes, etc., and adjustment becomes easy. Furthermore, since the operation of the high-frequency power source is immediately stopped when extinction of the discharge is detected, even if a laser output command is erroneously issued at this time, the high-frequency power source will not be destroyed, improving reliability.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a high-frequency discharge excitation laser oscillator according to an embodiment of the present invention, FIG. FIG. 2(b) is an equivalent circuit diagram of the discharge tube portion at the time of discharge extinguishment in one embodiment of the present invention. 3a to 3C 5a, 5b 0 Ai, B High frequency power line discharge tube current measurement circuit Comparison of current ratio calculation circuit Circuit measurement value ratio Kr Set value Sa Alarm signal stray capacitance

Claims (2)

[Claims] (1) In a high-frequency discharge-excited laser oscillator that supplies high-frequency power to a discharge tube to perform laser oscillation, one terminal is connected to one electrode of the discharge tube through a first line, and the other terminal is connected to a predetermined connection. a high frequency power source that is grounded at a point and connected to the other electrode of the discharge tube via a second line from the ground point and supplies the high frequency power; and a first current that measures the current value of the first line. a measuring circuit; a second current measuring circuit that measures a current value of the second line; and calculating a ratio between a measured value of the first current measuring circuit and a measured value of the second current measuring circuit. A comparison circuit that compares the value of the ratio with a set value and outputs a predetermined alarm signal indicating a discharge extinguishing state of the discharge tube when the value of the ratio is outside the range defined by the set value. High frequency discharge pumped laser oscillator. (2) The high frequency discharge excitation laser oscillator according to claim 1, wherein the high frequency discharge excitation laser oscillator is configured to stop the operation of the high frequency power supply in response to the alarm signal.