JPH0770775B2 - High frequency discharge excitation laser - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a high frequency discharge excitation laser, and more particularly to a high frequency discharge excitation laser for applying a high frequency voltage to a laser tube by a coaxial cable to obtain a laser output.

[Conventional technology]

FIG. 3 is a circuit diagram schematically showing an example of a conventional high frequency discharge excitation laser.

As shown in FIG. 3, the conventional high-frequency discharge excitation laser is roughly provided with a high-frequency power source 101, a coaxial cable 103, a matching circuit 102, and a laser tube 104. The high frequency power supply 101 is arranged in the power supply device 105 and outputs a high frequency voltage applied to the laser tube 104. The output voltage of this high-frequency power supply 101 is the coaxial cable 103
Is transmitted to the matching circuit 102 provided in the laser output device 106 via. Here, the coaxial cable 103 is inserted between the high frequency power supply 101 and the matching circuit 102. This is because, for example, the characteristic impedance of the coaxial cable is 50Ω or 75Ω, and the output of the high frequency power supply 101 having a low impedance. This is because it is impossible to achieve perfect matching without connecting to the side.

The matching circuit 102 matches the output impedance Z ₀ ′ of the high frequency power supply 101 and the impedance Z _L ′ of the laser tube 104 via the coaxial cable 103, and efficiently transfers the output voltage of the high frequency power supply 101 to the laser tube 104. belongs to. The matching circuit 102 includes a capacitor 121 connected to an outer conductor 132 of an inner conductor 131 of a coaxial cable 103,
A π-type matching circuit including a capacitor 123 connected to the two electrodes 143a and 143b of the laser tube, and a coil 122 connected in series between the inner conductor 131 of the coaxial cable and the electrode 143a of the laser tube. Is.

By the way, since the laser output device 106 provided with the laser tube 104 and the matching circuit 102 is located, for example, in the arm portion of an industrial robot or the like, it is necessary to adjust the high frequency discharge excitation laser due to aging or the like. In this case, not only the high frequency power supply 101 arranged in the power supply device 105 is adjusted, but also the matching circuit 1 in the laser output device 106 located in, for example, the arm portion of the industrial robot.
I had to adjust 02 as well, and there was a problem in terms of maintenance. Further, if the matching circuit 102 is provided at the position of the laser tube 104, a loop that generates noise becomes large, and the outside of the laser output device 106 must be completely shielded in order to block this noise. For example, there is a problem that the structure of the arm portion of the industrial robot provided with the laser output device 106 is complicated or the weight increases.

With respect to these problems, the present applicant has previously proposed a high frequency discharge pump laser as shown in FIG.

The high frequency discharge excitation laser shown in FIG. 4 has a matching circuit 10 in a power supply device 105 provided with a high frequency power supply 101.
2, the output of the matching circuit 102 and the laser tube 104
And coaxial cable 103, and then coaxial cable 1
03 is configured to be used as the capacitor 123 of the matching circuit 102, whereby the maintenance can be performed easily, and the structure of the location where the laser tube 104 is disposed is simple and lightweight, and the reliability is improved.

[Problems to be solved by the invention]

As described above, a matching circuit is conventionally provided in the power supply device 105 provided with the high frequency power supply 101 as shown in FIG.
The output of the matching circuit 102 and the laser tube 10 are provided.
4 is connected with the coaxial cable 103, and further, the coaxial cable
A high frequency discharge pumped laser has been proposed which is configured to use 103 as the capacitor 123 of the matching circuit 102. Such a high frequency discharge pump laser is a coaxial cable
The length of 103 is short and the size of the electrostatic capacitance is the matching circuit 102.
If the capacitance Q ₂ ′ of the coaxial cable 103 is too large, an extremely large capacitance is used as the capacitor 121 of the matching circuit 102. High frequency power supply 101
And the laser tube 104 via the coaxial cable 103 cannot be perfectly matched. Specifically, for example, if the connection distance l ′ of the coaxial cable 103 having a characteristic capacitance of 100 pF per meter is too long (for example, 3 meters or more), the electrostatic capacitance Q ₂ ′ of the coaxial cable 103 becomes large (for example, , 300 pF or more), and the capacitance Q ₁ ′ of the capacitor 121 of the matching circuit 102 is extremely large (for example, 8
000pF or more) must be set. Since the withstand voltage required for this capacitor 121 is extremely high, for example, several kilovolts, it is usually difficult to obtain such a high capacity and high withstand voltage capacitor. Moreover, even if such a high-capacity, high-voltage capacitor can be manufactured, such a high-capacity, high-voltage capacitor is large,
In addition, the price is high. Therefore, when the connection distance l'of the simultaneous cable 103 is long, there is a problem that the matching between the high frequency power supply 101 and the laser tube 104 via the coaxial cable 103 cannot be reliably performed by the above-described matching circuit.

In view of the problems in the above-described conventional high-frequency discharge pumped laser, the present invention connects an inductance element in parallel to the high-frequency power source side of the coaxial cable, and reduces the capacitance of the coaxial cable by this inductance element, It is an object of the present invention to reduce the value of a capacitance element connected in parallel to an output terminal of a power supply so that a high-frequency power supply and a laser tube via a coaxial cable can be reliably matched with a small matching circuit.

[Means for solving problems]

FIG. 1 is a block diagram showing the principle of a high frequency discharge pump laser according to the present invention.

According to the present invention, a high-frequency discharge excitation laser for obtaining a laser output by applying a high-frequency voltage to a laser tube 4 by means of a coaxial cable 3, the high-frequency power source 1 outputting the high-frequency voltage.
A capacitance element 21 connected in parallel to the output terminal of the high frequency power supply 1, and a matching element 22 connected in series between the high frequency power supply 1 and the coaxial cable 3.
There is provided a high frequency discharge excitation laser including an inductance element 23 connected in parallel to the high frequency power source 1 side of the coaxial cable 3.

[Work]

According to the high frequency discharge excitation laser of the present invention having the above-described configuration, the capacitance element 21 is connected in parallel to the output terminal of the high frequency power source 1 that outputs a high frequency voltage, and between the high frequency power source 1 and the coaxial cable 3. Is a matching element 22
And the inductance element 23 is connected in parallel to the high frequency power source 1 side of the coaxial cable 3. By the inductance element 23, the capacitance of the coaxial cable 3 can be reduced and the value of the capacitance element 21 can be reduced to match the high frequency power supply 1 with the laser tube 4 via the coaxial cable 3.

〔Example〕

An embodiment of a high frequency discharge pump laser according to the present invention will be described below with reference to the drawings.

FIG. 2 is a circuit diagram schematically showing an embodiment of the high frequency discharge pump laser of the present invention.

As shown in FIG. 2, in one embodiment of the high frequency discharge pump laser of the present invention, for example, a voltage of a frequency of several MHz is applied between the two electrodes 43a and 43b of the laser tube 4 to output a laser beam. The high frequency power supply 1, the matching circuit 2, the coaxial cable 3, and the laser tube 4 are provided. The high frequency power supply 1 is arranged in the power supply device 5 and outputs a high frequency voltage of, for example, several hundreds of volts. A capacitor 21 is connected in parallel to the output terminal of the high frequency power supply 1, and a coil is provided at one of the output terminals.
22 are connected in series. The inner conductor 31 and the outer conductor 32 at one end of the coaxial cable 3 are connected to one output terminal of the high frequency power source 1 and the other output terminal of the high frequency power source 1 via the coil 22 and the coil 23 are connected in parallel. At the other end of the coaxial cable 3, the inner conductor 31 and the outer conductor 32 are connected to both electrodes 43a and 43b of the laser tube 4, respectively.
As a result, the output voltage of the high frequency power supply 1 is supplied to the laser tube 4.

The matching circuit 2 for matching the high frequency power supply 1 and the laser tube 4 includes a capacitor 21 connected in parallel to the output of the high frequency power supply 1, one output terminal of the high frequency power supply 1 and an inner conductor 31 of the coaxial cable 3. Coil 22 connected in series to
The coil 23 connected to the inner conductor 31 and the outer conductor 32 of the coaxial cable 3 and the electrostatic capacitance Q ₂ of the coaxial cable 3 itself constitute a π type matching circuit. Then, the amount of electrostatic capacitance Q ₂ due to the coaxial cable 3 having the connection distance l is reduced by the coil 23, and the value of the electrostatic capacitance Q ₁ of the capacitor 21 is reduced.

In this matching circuit 2, the capacitance Q ₂ of the coaxial cable 3 increases as the connecting distance 1 of the coaxial cable 3 increases, so the inductance value of the coil 23 must be increased according to the length of the coaxial cable 3. . As a result, the output voltage of the high frequency power supply 1 is sufficiently boosted, and
The output power of the high frequency power supply 1 can be effectively supplied to the laser tube 4 by properly matching the impedance Z ₀ of the high frequency power supply 1 and the impedance Z _L of the laser tube 4 via the coaxial cable 3. Specifically, for example, a coaxial cable 3 having a characteristic capacitance of about 100 pF per meter 3
Connection distance l is, for example, 3 meters (coaxial cable 3
When the electrostatic capacity Q ₂ of the matching circuit ₂ is about 300 pF) and the coil 23 is set to 30 μH, the electrostatic capacity Q ₁ of the capacitor 21 of the matching circuit 2 is set to 2000 pF and the impedance Z ₀
And impedance of laser tube 4 via coaxial cable 3
The output power of the high frequency power supply 1 can be effectively supplied to the laser tube 4 by properly matching Z _L.

By the way, actually, the impedance Z _L of the laser tube 4 is
Depending on the operating state of the high frequency discharge excitation laser, for example, 50
It varies from 0Ω to 3KΩ. Therefore, the impedance Z _L of the laser tube 4 and the output impedance Z ₂ of the matching circuit 2 including the electrostatic capacity Q ₂ of the coaxial cable 3 cannot always be matched, but the laser tube normally used. A perfect match can be achieved for the four operating points. Here, the characteristic impedance of the coaxial cable 3
Z _w is, for example, 50 Ω or 75 Ω, which is significantly different from the impedance Z _L of the laser tube 2, but
Impedance Z _L , output impedance Z ₂ of matching circuit ₂ and characteristic impedance Z _{w of} coaxial cable 3
Even if the high frequency voltage is reflected from the laser tube 4 side to the matching circuit 2 side via the coaxial cable 3 without being completely matched with the laser tube 4, the reflected high frequency voltage is again transmitted via the coaxial cable 3 to the laser tube 4 side. Since it is reflected by the laser tube 4, the output power of the high frequency power source 1 is supplied to the laser tube 4 with high efficiency, so that it does not cause a problem.

Next, briefly describing the laser output operation of the laser tube 4,
The laser tube 4 is disposed in the laser output device 6, and is made of, for example, quartz glass 42 and the quartz glass tube 42.
It is provided with electrodes 43a and 43b provided above and below, respectively. The output voltage of the high frequency power source 1 is boosted by the matching circuit 2 and applied to the electrodes 43a and 43b of the laser tube 4 via the coaxial cable 3, but the high frequency voltage applied to the electrodes 43a and 43b of the laser tube causes A high frequency discharge is generated inside the quartz glass tube 41. Due to this glow discharge, carbon dioxide gas inside the quartz glass tube 42 (actually CO ₂ ,
A mixed gas of N ₂ and He) is excited. That is, the CO ₂ molecule inside the quartz glass tube is excited to a high-level vibrational state, and in the process of transitioning from this high-level molecular vibrational state to a low-level molecular vibrational state, the CO ₂ molecule has a predetermined level. Emits light of wavelength. This light is resonated by two reflecting mirrors (not shown) provided in parallel on both sides of the laser tube 4, and a part of the light is extracted as a laser output.

In this way, for example, only the laser tube 4 is provided in the laser output device 6 located on the arm of the industrial robot or the like, and the loop that generates noise is the both electrodes 43 of the laser tube 4.
Since only a connection point between a and 43b and the coaxial cable 3 is small, noise from the laser output device 6 hardly occurs, and the outside of the laser output device 6 does not have to be completely shielded. Therefore, for example, the arm part of the industrial robot provided with the laser output device 6 does not need to have a complicated structure. Even if the output voltage from the high frequency power supply 1 is set to a considerably long distance to the arm part of the industrial robot and the long distance is supplied by the coaxial cable 3, the high frequency power supply 1 and the coaxial cable 3 It is possible to perfectly match the laser tube 4 with the laser tube 4, and the output power from the high frequency power source 1 can be effectively supplied to the laser tube 4.

In the above-mentioned embodiment, the carbon dioxide gas laser is used as the high frequency discharge excitation laser, but the high frequency discharge excitation laser of the present invention is not only a carbon dioxide gas laser but also He-Ne, Co.
It can be applied to all other gas lasers such as (carbon monoxide) and excimer.

〔The invention's effect〕

As described above in detail, the high-frequency discharge pump laser according to the present invention has an inductance element connected in parallel to the high-frequency power source side of the coaxial cable, and the inductance element reduces the electrostatic capacitance of the coaxial cable. By reducing the value of the capacitance element connected in parallel to the output terminal of, the high-frequency power source and the laser tube via the coaxial cable can be reliably matched with a small matching circuit.

[Brief description of drawings]

FIG. 1 is a block diagram showing the principle of a high frequency discharge excitation laser according to the present invention, FIG. 2 is a circuit diagram schematically showing an embodiment of the high frequency discharge excitation laser of the present invention, and FIG. 3 is a conventional high frequency discharge. FIG. 4 is a circuit diagram schematically showing an example of a pump laser, and FIG. 4 is a circuit diagram schematically showing another example of a conventional high frequency discharge pump laser. (Description of symbols) 1 ... High frequency power supply, 2 ... Matching circuit, 3 ... Coaxial cable, 4 ... Laser tube, 21 ... Capacitance element, 22 ... Matching element, 23 ... Impedance element.

Claims (1)

[Claims] 1. A high-frequency discharge excitation laser for obtaining a laser output by applying a high-frequency voltage to a laser tube by means of a coaxial cable, the high-frequency power source outputting the high-frequency voltage, and a high-frequency power source connected in parallel to the output terminal of the high-frequency power source. A capacitance element, a matching element connected in series between the high frequency power supply and the coaxial cable, and an inductance element connected in parallel to the high frequency power supply side of the coaxial cable. A high frequency discharge pumped laser, characterized in that the capacitance of the coaxial cable is reduced and the value of the capacitance element is reduced to match the high frequency power source and the laser tube through the coaxial cable.