JPS60163478A - Gas laser oscillation device - Google Patents

Abstract

PURPOSE:To obtain stable laser beam power even at a pulse width of 0.1ms or less by a method wherein the micro discharge current at the time of pulse OFF is set in a specific range by connecting one end of a resistor to one of the discharge electrodes of a discharge tube, and connecting a capacitor between the other discharge electrode and the other end of the resistor. CONSTITUTION:When a transistor 3 turns ON, a high withstand voltage vacuum tube 2 turns OFF, the energy accumulated in the capacitor 8 flows as a micro discharge current through a closed circuit made up of the anode side discharge electrode 1a of the discharge tube 1, its cathode side discharge electrode 1b, the resistor 7, and the capacitor 8; the flowing time and the amount of current are dependent on the resistance value R of the resistor 7 and on the capacitance value C of the capacitor 8. In this case, if alpha=R'+R; (R' represents the discharge electrode resistance value at the time of pulse OFF; R, the resistance value of the resistor; C, the capacitance value of the capacitor; VAC, the discharge electrode potential difference at the time of pulse OFF; and tOFF the pulse OFF time) the resistance value R of the resistor 7 and the capacitance value C of the capacitor 8 are determined by formular I .

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a gas laser oscillation device that discharge-excites a laser medium to generate continuous pulse oscillation.

Conventional configuration and problems thereof In recent years, in laser processing, processing using continuous pulse oscillation laser output has become mainstream. Furthermore, in order to shorten processing time, a laser pulse power with a remarkable laser peak power is required.

Hereinafter, a conventional example will be explained with reference to FIGS. 1 and 2 of the drawings.

FIG. 1 shows part of a discharge current control circuit of a conventional gas laser oscillation device. In Fig. 1, 1 is a discharge tube, 1a is an anode discharge electrode, 1b is a cathode discharge electrode, 2 is a high voltage vacuum tube, 3 is a transistor, 4Fi
This is a current limiting resistor.

FIG. 2 shows the waveform of the discharge current I, the waveform of the laser beam P, and the base signal S of the transistor 3 when continuous pulse oscillation is performed using the circuit shown in FIG.

The operation will be explained below. The discharge current flowing between the anode discharge electrode 1a and the cathode discharge electrode 1b of the discharge tube 1 is controlled by controlling the bias voltage applied to the cathode of the high voltage vacuum tube 2 by switching the transistor 3.

That is, the base of the transistor 30 is turned on.

Continuous pulse oscillation is performed by applying an off pulse signal.

However, in the above configuration, the pulse on,
When the off time is less than 0.1 mS, discharge lag affects the discharge current I and the laser beam power P as shown in FIG. 2, and the waveforms of the discharge current I and the laser beam power P are distorted, making it impossible to perform good continuous pulse oscillation.

Therefore, it was found that the instability of this discharge adversely affected the laser beam power during continuous pulse oscillation.

Therefore, it has been desirable to develop a gas laser oscillation device that can obtain stable laser beam power even with pulses of 0.1 ms or less.

OBJECTS OF THE INVENTION In view of the above drawbacks, it is an object of the present invention to provide a gas laser oscillation device that can obtain stable laser beam power even with a pulse width of 0.1 mS or less.

Structure of the Invention To achieve this object, the gas laser oscillation device of the present invention is a gas laser oscillation device that excites a laser medium by discharge to generate continuous pulse oscillation, in which one end of a resistor is connected to one of the discharge electrodes of a discharge tube. , and a capacitor is connected between the other discharge electrode and the other end of the resistor, and the minute discharge current when the pulse is OFF is I () = VAC'P (c, tOFF), but σ-R' +R.

R': Resistance value between electrodes for discharge during pulse-off.

R: resistance value of the resistor.

C: capacitance value of the capacitor.

vAc: Potential difference between electrodes for discharge during pulse-off.

tOFF: The resistance value R of the resistor and the capacitance value C of the capacitor are set so as to satisfy the pulse off time.

Description of examples FIG. 3 is a drawing showing an embodiment of the present invention.

This will be explained with reference to FIG.

FIG. 3 shows a part of the discharge current control circuit in one embodiment of the present invention. 1.1a, 1b.

Reference numerals 2, 3 and 4 are a discharge tube, an anode discharge electrode, a cathode discharge electrode, a high voltage vacuum tube, a transistor, and a resistor for current limiting, respectively, as in the conventional case.

6. 6 is a voltage dividing resistor that maintains a constant potential difference between the discharge electrodes during no discharge, 7 is a resistor with a resistance value of H, 8 is a capacitor with a capacitance value of C, and the resistor 7 is connected in series with the discharge tube 1. A capacitor 8 is connected in parallel to the series circuit.

Then, the applied voltage is VO, the voltage at point A is vP, the resistance value between the discharge electrodes is t/L, and the current flowing through the discharge tube is 1.

The circuit operation will be explained below.

First, when the transistor 3 is off, there is a potential difference between the plate voltage Vp caused by the high voltage vacuum tube 2 and the applied voltage V□ across the capacitor 8, and that potential difference (■o
-vP), the capacitor 8 is charged.

Next, when the transistor 3 is turned on, the plate voltage of the high voltage vacuum tube 2 drops by several kilovolts and a discharge current begins to flow. At the same time, the capacitor 8 is further charged. When the high voltage vacuum tube 2 is turned off, most of the discharge current I is cut off. However, at this time, the energy stored in the capacitor 8 flows as a minute discharge current o in a closed circuit formed by the anode discharge electrode 1a, the cathode discharge electrode 1b, the resistor 7, and the capacitor 8 of the discharge tube 1.

At this time, this minute discharge current ■o continues to flow. Therefore, this minute discharge current 0 can keep the laser medium in an ionized state when the pulse is turned off, so that the next pulse oscillation is performed smoothly and the laser peak Power also increases.

Next, the resistance value R of the resistor 7 and the capacitor 8
A method for determining the capacitance value C will be explained.

From FIG. 3, if we set the applied voltage vo, the plate voltage vP during pulse-off, the minute discharge current IO, and the discharge interelectrode resistance R' during pulse-off, the following equation holds true when transitioning from pulse-on to pulse-off. However, it is assumed that the resistance values of the voltage dividing resistors 6, 6 are so large that they can be ignored.

・・・ ・ −・ ・・・(1) Here, σ= R'+ R, V□ −V p = VA
C, then formula (1) becomes I() --"AC"p(Gt)---(2).

Therefore, micro-discharge current engineering. is the pulse off time tO
If it is FF, the formula C2) becomes I The horizontal axis of the minute discharge current IO2 is the pulse off time tOFF.

As can be seen from equation (3) and FIG.
Determine. Here, micro-discharge current engineering. It must be large enough to sufficiently maintain the rise in peak power when the pulse is on, but not so thick that it generates laser power when the pulse is off.

Figure 5 shows the discharge current I during continuous pulse excavation in Figure 3.
, the waveform of the beam power P, and the waveform of the base signal S of the transistor 3 (broken line).

As can be seen by comparing FIG. 6 and FIG. 2, the waveform of the discharge current (2) has also increased, distortion has decreased, and it is flowing stably. In addition, the beam power P has also been significantly increased, making it possible to obtain a powerful pulse output with high peak power.

In the above embodiments, the resistor 7 has a fixed resistance value, and the capacitor 8 has a fixed capacitance C, but these may be variable resistors or variable capacitors with variable values. For example, the resistance value R of the variable resistor 7 and the capacitance value C of the variable capacitor 8 may be adjusted based on the setting of the pulse-off time.

Effects of the Invention As described above, the present invention makes it possible to increase the pulse output and ensure stability especially in the region where the pulse width is 0.1 mS or less, and is excellent in extremely high-precision precision machining and high-speed machining. It has the following effects.

[Brief explanation of drawings]

Figure 1 is a partial circuit diagram of a conventional gas laser oscillation device;
Figure 3 is a partial circuit diagram of a gas laser oscillation device according to an embodiment of the present invention, Figure 4 is a time-dependent characteristic diagram of minute discharge current, and Figure 5 should be compared with Figure 2. It is the same characteristic diagram. 1...discharge tube, 1a...anode (i
ll discharge electrode, 1b... cathode side discharge electrode, 2... high voltage vacuum tube, 3... transistor, 4... resistor, 5, 6... ...Voltage dividing resistor, 7...Resistor, 8...Capacitor. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Toe pulse time

Claims (2)

[Claims] (1) In a gas laser oscillation device that excites a laser medium by discharge to generate continuous pulse oscillation, one end of a resistor is connected to one of the discharge electrodes of the discharge tube, and the other end of the resistor is connected to the other discharge electrode. Connect a capacitor and create a minute discharge current when the pulse is off. However, σ=R'0R,. R': Resistance value between electrodes for discharge during pulse-off. R: resistance value of the resistor. C: capacitance value of the capacitor. vAC = potential difference between electrodes for discharge when pulse is off. tOFF: A gas laser oscillation device in which the resistance value R of the resistor and the capacitance value C of the capacitor are set so as to satisfy a pulse off time. (2) The gas laser oscillation device according to claim 0, wherein the resistor is a variable resistor whose resistance value can be varied, and the capacitor is a variable capacitor whose capacitance value can be varied.