JPS60163479A - 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 a capacitor and a resistor series-connected between the discharge electrodes of a discharge tube. CONSTITUTION:When a high withstand voltage vacuum tube 2 turns off, the energy accumulated in the capacitor 7 flows as a micro discharge current IO 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 8, and the capacitor 7; the flowing time and the amount of current are dependent on the resistance value R of said resistor 8 and on the capacitance value of said capacitor 7. In this case, 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) then, the resistance value of the resistor 8 and the capacitance value C of the capacitor 7 are determined by formula 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, and 4 is a resistor for current limiting.

Further, FIG. 2 shows the waveform of the discharge current, 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 3 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 m3, discharge lag affects the discharge current as shown in FIG. 2, the waveform of the discharge current and the waveform of the laser beam power P become distorted, and good continuous pulse oscillation becomes impossible.

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

Therefore, it has been desired 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-mentioned 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 to 7 ZS or less.

In a gas laser oscillator that discharge-excites a medium and generates continuous pulse oscillation, a capacitor and a resistor are connected in series between the discharge electrodes of a discharge tube, and the minute discharge current 0 when the pulse is OFF is IO"'1vAc"p( -Crz tOFF) However, α= R' + R R': Resistance value between electrodes for discharging at pulse-off time R: Low resistance resistance value C: Capacitance value of capacitor vAc: Potential difference between electrodes for discharging at pulse-off time tOFF:
The capacitance value C of the capacitor and the resistance value R of the resistor are set so as to satisfy a pulse-off threshold.

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-side discharge electrode, a cathode-side discharge electrode, a high-voltage vacuum tube, a transistor, and a current-limiting resistor, respectively, as in the conventional case.

A capacitor 8 is a resistor having a resistance value H, and the capacitor 7 and the resistor 8 are connected in series and connected in parallel to the discharge tube 1.

The applied voltage is VO, the voltage at point A is vP, the resistance value between the discharge electrodes is R', and the current flowing through the discharge tube 1 is I.

The circuit operation will be explained below.

First, when the transistor 3 is off, a potential difference between the plate voltage vP from the high voltage vacuum tube 2 and the applied voltage Vo is applied to both ends of the capacitor 7.
vP), the capacitor 7 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 that time, charging of the capacitor 7 further progresses at the same time. When the high voltage vacuum tube 2 is turned off, most of the discharge currents are cut off. However, at this time, the energy stored in the capacitor 7 flows as a minute discharge current 0 in a closed circuit formed by the anode discharge electrode 1a, the cathode discharge electrode 1b, the resistor 8, and the capacitor 7 of the discharge tube 1.

At this time, this minute discharge current IO continues to flow. Therefore, due to this minute discharge current IQ, when the pulse is off,
Since the laser medium can be maintained in an ionized state, the next pulse oscillation is performed smoothly and the laser peak power is also increased.

Ru.

From Figure 3, if we set the applied voltage o, the plate voltage vP at pulse-off, the minute discharge current o, and the resistance between the discharge electrodes R' at 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 5 and 6 are negligibly large.

By setting α-R'+R8vO-vP=vAc, equation (1) is l0=ivAcexp(-100t)...
...(2) becomes.

Therefore, micro-discharge current engineering. is the pulse off time tO
FF, the -) formula is I () = : VAC@Xp (-c, t()F
F)...""' (3) This situation is illustrated in Fig. 4. The vertical axis in Figure 4 is
The horizontal axis of the minute discharge current IO2 is the pulse off time "OFF".

As can be seen from equation (3) and FIG.
Determine. Here, the minute discharge current IO must be large enough to sufficiently maintain the rise of the peak power when the pulse is on, but not so large as to cause laser power to be generated when the pulse is off.

FIG. 6 shows the waveform of the discharge current I, the waveform of the beam power P, and the waveform of the base signal S of the transistor 3 (broken line) during continuous pulse oscillation in FIG.

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

In addition, in the above embodiment, the capacitor 7 has a fixed resistance value C, and the resistor 8 has a fixed resistance value, but these are variable capacitors and variable resistors with variable values. If so, the capacitance value C of the variable capacitor kiln and the resistance value R of the variable resistance rod 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 0.1ffiS or less, and is excellent in precision machining with extremely high precision and high-speed machining. It is effective.

[Brief explanation of the drawing]

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 6 should be compared with Figure 2. It is the same characteristic diagram. 1...discharge tube, 1a...anode side discharge electrode, 1b...cathode side discharge electrode, 2
・・High-voltage vacuum tube, 3...Transistor,
4... Resistor, 6, 6... Voltage dividing resistor, 7
... Capacitor, 8... Resistor. Name of agent: Patent attorney Toshio Nakao (1st person)
1%il Figure 2 Figure 31g Figure 4

Claims (1)

[Claims] (1) In a gas laser oscillation device that excites the laser medium by discharge and generates continuous pulse oscillation, a capacitor and a resistor are connected in series between the discharge electrodes of the discharge tube, and the pulse is turned off.
When the minute discharge current IO is 1 () = , VACeXp (-, t()FF
) However, α==R'→-R R': Resistance value between electrodes for discharging when pulse is off R: Low resistance resistance value C: Capacitance value of capacitor v〇: Potential difference between electrodes for discharging when pulse is off tOFF:
A gas laser oscillation device in which the capacitance value C of the cosidenser and the resistance value R of the resistor are set so as to satisfy the pulse-off time 〇(2) The capacitor is a variable capacitor whose capacitance value can be varied,
The gas laser oscillation device according to claim 1, wherein the resistor is a variable resistor whose resistance value can be varied.