JPH01117384A - Control method for gas laser oscillation device - Google Patents

Abstract

PURPOSE:To enable an output laser ray with a various output pattern to be controlled stably without making an electrode large in size by a method wherein when an output instruction value of an output laser ray is zero, a prescribed pre-discharge current is made to outputted if a rise time of the output instruction value is smaller than a prescribed value and a pre-discharge current is made to be outputted immediately before the rise of the output instruction value of the output laser rays if a rise time is larger than a prescribed value. CONSTITUTION:A laser ray output instruction generator 11 which generates an output instruction value SL for an output laser ray L, a pre-discharge instruction generator 12 which generates an instruction value CS for a pre-discharge current iS, and a current instruction generator 13 are provided. When the output instruction value SL of an output laser ray L outputted from the generator 11 is zero, the instruction value CS for the pre-discharge current iS is made to be outputted if a rise time of the output instruction value SL of the output laser ray L is smaller than a prescribed value. And, the instruction value CS for the pre-discharge current iS is made to be outputted just prior to (hundreds musec before) the rise of the instruction value SL if the above rise time is larger than the prescribed value. And, the generator 13 is made to output the instruction value CL corresponding to a discharge current iL.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Advantages of the Invention) The present invention relates to a method for controlling the output of an output laser beam by controlling a discharge current in a laser gas in a gas laser oscillation device.

(Technical background and problems to be solved) Fig. 5 is a perspective view showing an example of a triaxial orthogonal type gas laser oscillation device having a laser resonator structure that refracts light multiple times, and Fig. 6 is a side view of the device. It is a diagram. This gas laser oscillation device includes a high-voltage AC power supply 1 that generates an AC high voltage, electrode devices 2^ and 2B arranged in parallel with a predetermined gap, and to which an AC high voltage is applied by the high-voltage AC power supply 1. A plurality of electrodes 3A and 3B are arranged in each electrode device 28 and 2B so as to face each other with the predetermined gap interposed therebetween, and an alternating current glow discharge occurs between the two corresponding electrodes 3A and 3B, and one end of the electrode devices 2A and 2B. A total reflection mirror 4 is disposed in the predetermined gap and totally reflects the light generated in the direction , a partially transmitting mirror 5 that outputs an output laser beam, and folding mirrors 6 and 6B that are disposed in the predetermined gaps at both ends of the electrode devices 2A and 2B, and that reflect the light 1 back and oscillate the laser beam. It is being

To explain the operation of such a configuration, when a high voltage AC voltage with a predetermined discharge current i is applied to the electrode devices 2A and 2B by the high voltage AC power supply 1, the plurality of electrodes 3^ and 3B
An alternating current glow discharge occurs in between. Since this alternating current glow discharge is performed via the capacitors 7A and 7B connected to the plurality of electrodes 3A and 3B, the plurality of electrodes 3A and 3B
This results in a stable discharge that is uniform between the two and does not transition to arc discharge. When an AC glow discharge occurs between the plurality of electrodes 3^ and 3B in this way, the laser gas G is excited and i is generated in the direction 2 of the AC glow discharge and the direction X perpendicular to the flow direction y of the laser G, resulting in total reflection. Laser oscillation occurs within a resonator made up of the mirror 41, partially transmitting mirror 5, and folding mirrors 6^, 6B, and output laser light is output from the partially transmitting mirror 5. Since the output of this output laser beam is approximately proportional to the number of molecules of the excited laser gas G, the output of the output laser beam can be controlled by controlling the discharge current i from the high voltage AC power supply 1.

Figure 7 shows the discharge current i from the high voltage AC power supply 1 and the electrode 3A.
and 3B, and the solid line a shows the characteristics in a static case where the discharge current i is gradually increased.
Indicated by In this case, stable alternating current glow discharge is occurring in region (2), and normally, when laser oscillation is performed, the discharge current i is controlled within this region (2). However, when the discharge current i is increased within the region (3), the discharge becomes unstable after the discharge voltage V rises for a period of time, and a high-intensity arc discharge occurs between the electrodes 3A and 3B. Voltage V
decreases □ and arc discharge occurs in the entire area between electrodes 3^ and 3B. In addition, the discharge current i is increased from zero to a predetermined value in several hundred μs.
The dotted line already shows the characteristics in a transient case where the change is made in a short time less than ec. In this case, a stable AC glow discharge is occurring in the region Arc discharge and electricity occur at a lower discharge current i.

Here 1. The cause of this phenomenon will be explained in detail. Potential distribution V in the discharge space in AC glow discharge,
The positive ion distribution ρ+ and the electron distribution ρ− are as shown in FIG. 8, and in order to maintain AC glow discharge, concentration and accumulation of positive ions called a cathode fall region is essential. Generally, in the initial state when the discharge current i is zero, there are no positive ions in the discharge space, so a cathode fall region cannot be formed, and after the discharge current i rises, a cathode fall region is generated by collision ionization of electrons in the discharge space. The positive ions are gradually attracted to the cathode and form a cathode fall region. However, since the kinetic speed when positive ions are attracted to the cathode is slow, it takes several hundred microseconds to form the cathode fall region, so there is no problem in the static case described above, but in the transient case For example, when the discharge current is intermittent in a pulsed manner in order to pulse the output laser light, a large discharge current i is applied before a sufficient cathode fall region is formed. Therefore, arc discharge occurs with characteristics as shown by the dotted line in FIG.

When such an arc discharge occurs, output laser light cannot be obtained efficiently, and electrodes 3A and 3
It may also cause B to melt. Therefore, the maximum output of the output laser beam is determined by the discharge current i just before arc discharge occurs, which determines the maximum discharge power that can be input between the electrodes 3^ and 3B. The discharge current ip is about 60% of the discharge current ic during continuous oscillation. That is, the output command value SP of the output laser light during pulse oscillation can only be set to a smaller value than the output command value SC of the output laser light during continuous oscillation.

However, in applications such as laser processing, there is a demand for pulsed oscillation of output laser light with a short rise time and high output, and there is a problem in that it is necessary to use a larger electrode than necessary for this purpose. Ta.

(Objective of the Invention) The present invention was made in view of the above-mentioned circumstances, and an object of the present invention is to stably control output laser light such as a pulsed laser beam having a short rise time and a large output. An object of the present invention is to provide a control method for a gas laser oscillation device that can be controlled.

(Means for Solving the Problems) The present invention relates to a method of controlling the output of the output laser light by varying the discharge current with the output command value of the output laser light of a gas laser oscillation device, The above purpose is to output a predetermined preliminary discharge current when the output command value of the output laser beam is zero and the time until the output command value rises is less than or equal to a predetermined value, The above can be achieved by outputting the preliminary discharge current immediately before the output command value of the output laser beam rises.

(Function of the Invention) The control method of the gas laser oscillator of the present invention continues the discharge by flowing the preliminary discharge current even during the period when the output command value of the output laser beam is zero, so the rise time is short and Even when outputting high output pulsed laser light, it is possible to obtain high output laser light by utilizing up to the maximum discharge current of the electrodes.

(Embodiment of the Invention) FIG. 1 is a block diagram showing an example of a control device that realizes the control method of the gas laser oscillation device of the present invention, and generates a laser beam output command that generates an output command value SL of the output laser beam. 11, and a preliminary discharge current i.

When the output command value SL of the output laser light from the preliminary discharge command generator 12 which generates the command value CS and the laser light output command generator 11 is zero, the output command value S of the output laser light
When the time until L rises is less than a predetermined value, the pre-discharge command generator 12 outputs the command value CS of the pre-discharge current is, and when the time is more than the pre-determined value, the output command value of the output laser beam is output. Immediately before SL rises (several hundred before μsee)
A current command generator 13 outputs a command value C5 of a preliminary discharge current ig, and outputs a command value CL of a corresponding discharge current iL after the output command value SL of the output laser beam rises. . Then, an adder performs feedback control of the discharge current i based on the command value CL of the discharge current iL from the current command generator 13 or the command value CS of the preliminary discharge current i and the detected value CD from the current detector 17. 14. error amplifier 1
5. Power converter 16. A current detector 17 is provided.

FIG. 2 shows the command value CL of the discharge current I and the command value CS of the preliminary discharge current 13 when the time t until the output command value SL of the output laser beam rises is less than a predetermined value. , FIG. 3 shows the discharge current 11. when the time t2 until the output command value SL of the output laser beam rises is equal to or more than a predetermined value. Command value CL of and command value C5 of preliminary discharge current i3
This shows that. In this way, by flowing the preliminary discharge current is before the discharge current iL, positive ions can be generated in the discharge space in advance and a sufficient cathode fall region can be formed, so that a large discharge can be generated in a short time. Even when the current i is applied, an AC glow discharge can be obtained without generating an arc discharge. Note that this preliminary discharge current i3 is determined by the discharge current i and the output p of the output laser beam, as shown in FIG.
Since the relationship between p and p is generally non-linear, it may be set within a range (arrow a in the figure) that does not affect the output p of the output laser beam at all.

(Effects of the Invention) As described above, according to the control method of the gas laser oscillation device of the present invention, it is possible to stably control the output laser light of various output patterns without increasing the size of the electrode. It is possible to obtain high output laser light. Furthermore, since damage to the electrodes due to arc discharge is eliminated, the reliability of the gas laser oscillation device can be improved.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of a control device that implements the control method of the gas laser oscillation device of the present invention, FIGS. 2 and 3 are diagrams showing the control signals, and FIG. 4 is a general gas laser oscillation device. A diagram showing the relationship between the discharge current of the device and the output of the output laser beam, FIG. 5 is a perspective view showing an example of a general gas laser oscillation device, FIG. 6 is a side view thereof, and FIG. 7 is a diagram showing the discharge current and output of the output laser beam. FIG. 8 is a diagram showing the relationship with discharge voltage, FIG. 8 is a diagram showing the state in the discharge space, and FIG. 9 is a diagram showing control signals according to a conventional control method of a gas laser oscillation device. . 1... High voltage AC power supply, 2^, 2B... Electrode device, 3
A. 3... Electrode, 4... Totally reflecting mirror, 5... Partially transmitting mirror, 6A. 6t... folding mirror, 7A, 7B... condenser, 11
... Laser light output command generator, 12 ... Preliminary discharge command generator, l3 ... Current command generator, 14 ... Adder, 15 ... Error amplifier, 16 ... Power converter ,1
7... Current detector. Applicant's representative Yuji Yasugata 2nd 3rd day output L-sample 6th 70th

Claims (1)

[Claims] When controlling the output of the output laser beam by varying the discharge current with the output command value of the output laser beam of the gas laser oscillation device, if the output command value of the output laser beam is zero, this output command value rises. When the time up to that point is less than or equal to a predetermined value, a predetermined pre-discharge current is output, and when the time is greater than or equal to the predetermined value, the pre-discharge current is output immediately before the output command value of the output laser beam rises. A control method for a gas laser oscillation device characterized by the following.