JPS6140157B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a laser oscillation device, and more particularly to a device for controlling the waveform of laser oscillation output.

Conventionally, in solid-state laser oscillation devices that perform welding processing, in order to form the waveform of the laser oscillation output, an LC circuit is used to form a discharge circuit for the accumulated charge of a capacitor that is discharged into an excitation tube, or a plurality of excitation lamps are connected over time. Consideration is being given to lighting the lights overlapping each other and staggering the timing. In the former case, the LC circuit becomes complicated and there are limits to the waveforms that can be obtained.In the latter case, each excitation tube requires a charging/discharging capacitor, and large currents flow into and out of the charging/discharging capacitor, resulting in loss. This resulted in a relatively large capacitor with little resistance, and the power supply was also large.

In laser welding, the output waveform of the laser beam is continuously oscillated and a pulsating current is superimposed on it. However, when the pulsating current is emitted, the life of the excitation tube is shortened. Furthermore, continuous low pulsating laser output will not melt metal unless the laser output is large. In a pulse output laser, it is impossible to increase the pulse peak value, pulse width, and pulse repetition rate because there is a limit to the permissible input of the excitation tube. On the other hand, in welding, etc., the longer the peak output and irradiation time or pulse width, the better the heat will be transmitted to the deeper parts of the welding material, resulting in better welding. However, it has been difficult to obtain these laser outputs due to restrictions in the production of the device as described above.

According to the present invention, regularly varying laser output can be obtained from a constant DC voltage power source by combining excitation tubes with different voltages and excitation efficiencies.

Hereinafter, the present invention will be explained with reference to Examples.

In FIG. 1, a pair of excitation tubes 3 and 4 for exciting a laser substance 2 installed at a common focal point of a double elliptical condensing mirror 1 are respectively arranged at the other two focal points of the condensing mirror 1. has been done. Further, a pair of laser resonators 5 and 6 are arranged at both ends of the laser material 2. A DC power supply 7, which is the main power source for lighting the excitation tubes 3 and 4, is connected in parallel with two sets of switching circuits 8 and 9, and a coil 10 is arranged on the positive side after passing through one of the switching circuits 8. is connected to one end of the Similarly, a coil 11 is arranged on the positive side passing through the other switching circuit 9 and on one end side of the excitation tube 4. In this case, in order to stabilize the discharge of the excitation tubes 3 and 4, the DC auxiliary power supply 1
Direct current discharge stabilizing resistors 13 and 14 connected in parallel to the positive side of 2 are connected to the circuits after passing through the coils 10 and 11, respectively. Each terminal side of the excitation tubes 3 and 4 and the negative side of the DC auxiliary power supply 12 are combined into one circuit line, and the circuit line is branched and negative feedback is sent to the DC power supply 7 via switching circuits 8 and 9. . Further, one switching circuit 8 is engaged with a control circuit 15 for controlling its conduction time, and the other switching circuit 9 is engaged with another control circuit 16 having the above-mentioned control function.

The present invention is constructed as described above, and its operation will be explained next. In FIG. 2, which shows the relationship between the applied voltage to the excitation tube and the laser output, a curve 30 indicates an excitation tube 3 filled with krypton gas at a low gas pressure, for example, 1 atm, and a curve 31 indicates an excitation tube 4 filled with krypton gas at a low gas pressure of 1.5 atm. This is the input/output characteristics during YAG laser rod excitation. Since the excitation tube 4 with a high gas pressure has a larger impedance during discharge, a sufficient discharge current will not flow unless a high voltage is applied, and therefore no input power will be applied and sufficient light emission will not occur. Therefore, under the same applied voltage conditions, the laser output will be lower than in the excitation tube 3 with a lower gas pressure. 2 like this
When the laser substances 2 in the laser resonators 5 and 6 are alternately excited using excitation tubes 3 and 4 with different types of characteristics, a group of pulse trains with waveforms having different peak outputs and pulse widths are alternately formed. can do. That is, by using the control circuit 15 to shorten the operating time _t1 to _t2 of the switching circuit 8, the output waveform 40 shown in FIG. Time t ₂ ~
By increasing _t3 , the output waveform 41 shown in the figure is obtained. In this case, each peak output of the output waveforms 40 and 41 is obtained as follows. The voltage of the DC power supply 7 is selected to be 180V as shown by the broken line in FIG.
The excitation tubes 3 and 4 are discharged in advance from the DC auxiliary power supply 12 through the DC stabilizing resistors 13 and 14 with a sufficiently low discharge current that no laser oscillation occurs. At this time, the DC discharge current is selected so that the voltage drop across the excitation tubes 3 and 4 is 180V or less. When the switching circuit 8 is closed, a large current flows from the DC power source 7 through the circuit 8, through the coil 10, and into the excitation tube 3. Since the characteristic of the excitation tube 3 is the curve 30 as described above, the output waveform 40 has a peak output corresponding to the intersection 33 with the broken line 32. Similarly, since the characteristic of the excitation tube 4 is the curve 31, the output waveform 41 has a peak output corresponding to the intersection 34 with the broken line 32.

By replacing the characteristics of the excitation tube 3 with the curve 31 and the characteristics of the excitation tube 4 with the curve 30, and further controlling the operation timings of the switching circuits 8 and 9, the result shown in FIG. Waveform 4 shown
It is also easy to set it to 2.43.

In this way, two excitation tubes with different voltages and excitation efficiencies are used.
By arranging two or more types of lasers in the same resonator and discharging them for a controlled period of time, it is possible to obtain a pulsed laser output that combines a waveform with a large peak output and a small pulse width and its opposite waveform. Therefore, if a group of outputs having different peak values are sequentially generated and applied to welding, the molten parts will be sufficiently mixed and a good welding process can be performed. Furthermore, since the pulse width is reduced in a state where the peak value is large, by limiting the input power to the excitation tube, the life of the excitation tube can be significantly extended.

FIG. 4 shows another embodiment in which a group of excitation tubes having the same voltage and excitation efficiency characteristics is used, and the same reference numerals as in FIG. 1 indicate the same components.

A laser substance 2 is installed at a common focal point of a double elliptical condensing mirror 1, and excitation tubes 50 and 51 are installed at the other two focal points. Reference numeral 52 denotes a single elliptical condensing mirror, and at its focal point there is another laser material 53 and an excitation tube 54.
is located. The laser materials 2 and 53 and the excitation tubes 50 and 54 are coaxial, respectively. In addition, the three excitation tubes 50, 51, 54
Both the voltage and excitation efficiency have the same characteristics. 5 and 6 are laser resonators, and laser materials 2 and 5
3 between them and coaxially with them.
The terminals 55, 56 and 57, 58 are connected to the terminals 55, 56 and 57, 58, respectively, in order to operate the excitation tubes 50, 54 connected in series to simultaneously light up and the excitation tube 51 to light up independently. Similarly, it is connected in parallel to the DC power supply. Although not shown, these two sets of excitation tube groups are connected to two sets of switching circuits that are engaged with a control circuit that performs the same operation as in the above embodiment, thereby configuring two sets of lighting circuits. .

In the above device, there is a difference in impedance between the two sets of lighting circuits, and a difference also occurs in the amount of light emitted by discharge. Therefore, by operating the two sets of lighting circuits alternately and controlling their operating times, it is possible to form an output waveform similar to that shown in FIG.

In addition to the above two embodiments, three or more excitation tubes with different voltages and excitation efficiencies are used to generate laser pulses with three different peak outputs, and the order in which they are combined is changed to generate various waveform groups. The voltage and output characteristics of an excitation tube change as the excitation tube deteriorates, so even if a new excitation tube with no deterioration is combined with another excitation tube that has deteriorated further, the peak output will change. Different waveforms can be created and the same effects as in the previous embodiment can be obtained. Therefore, the present invention can be modified in various ways without departing from the spirit thereof.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing one embodiment of the present invention, Figure 2 is a circuit diagram showing an embodiment of the present invention.
The figure is an output characteristic diagram of the excitation tube in the above embodiment, FIGS. 3a and 3b are output waveform diagrams in the above embodiment, respectively, and FIG. 4 is a main part configuration diagram showing another embodiment of the present invention. 1,52...Condensing mirror, 2,53...Laser material, 3,4,50,51,54...Excitation tube, 5,
6... Laser resonator, 7... DC power supply, 8, 9...
...Switching circuit, 15, 16...Control circuit.

Claims (1)

[Claims] 1. A double elliptical condensing mirror, a laser substance placed at the focal point of the condensing mirror, and a laser substance placed at another focal point of the condensing mirror to excite the laser substance. and a plurality of excitation tube groups having different emission voltage characteristics, a laser resonator disposed at both ends of the laser material, a DC power supply connected to each of the excitation tube groups, and the DC power supply and the excitation tube group. 1. A pulse laser device comprising a switching circuit group provided between the switching circuits and a control circuit group for operating the switching circuit group and controlling the lighting timing and opening/closing time of the excitation tube group. 2. The pulsed laser device according to claim 1, wherein the excitation tube group periodically excites pulsed laser outputs having different combinations of peak output and pulse width by applying the same voltage.