JPH06105324B2 - Laser light transmission device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a laser light transmission device using a metal hollow optical waveguide useful for medical treatment or laser processing, and more particularly to a highly safe laser light transmission device. is there.

[Prior Art] In recent years, carbon dioxide lasers have come to be widely used in medical processing or industrial processing fields such as welding, cutting, and heat treatment. However, since its oscillation wavelength is in the infrared region of 10.6 μm, the conventional silica optical fiber has a large loss and cannot be used as a waveguide for carbon dioxide laser light. Therefore, as the means for guiding the carbon dioxide laser light, the spatial beam transmission method using several mirrors is mainly adopted at present, but this is extremely disadvantageous in terms of operability.

Infrared optical fibers and hollow optical waveguides are currently being researched and developed as waveguides for carbon dioxide laser light.

The former infrared optical fiber uses a material such as chalcogenide or halide that is transparent in the infrared region to confine the beam in the core region with a high refractive index and transmit it.
The basic waveguide mechanism is the same as that of the conventional silica optical fiber.

On the other hand, in the latter hollow optical waveguide, the reflectance of the inner wall of the pipe-shaped waveguide is made sufficiently high, and energy is confined in the hollow region to be transmitted. As one of such hollow optical waveguides, a metal hollow optical waveguide in which a thin film having a small absorption in the wavelength band of the transmitted laser light is embedded is proposed, and a germanium-containing nickel hollow optical waveguide as shown in FIG. 3 is prototyped. (M. Miyagi, AH
ongo, Y.Aizawa, and S.Kawakami, Appl.Phys.Lett., 43,43
0 (1983). The transmission loss of the hollow metal optical waveguide 2 depends on the film thickness of the germanium layer 11, and the nickel layer 12 not only functions to maintain the mechanical strength but also contributes to the transmission loss.

[Problems to be Solved by the Invention] Now, not only in the metal hollow optical waveguide, but in the optical waveguide for the purpose of energy transmission, all the losses are converted into heat, and the thermal capacity of the optical waveguide increases as the transmission capacity increases. Destruction becomes a problem. The reason is that if a large amount of laser light is transmitted despite the destruction of the optical waveguide, the risk of laser light leaking from the damaged portion of the optical waveguide and causing burns or fires on the human body is extremely high. is there. In order to avoid this, it has been proposed to attach a temperature sensor distributed in the longitudinal direction or to use another optical fiber for temperature detection together, but the configuration is complicated and the cable for inserting the waveguide is thick. It's not practical.

The object of the present invention is, in the optical waveguide for energy transmission using the above-mentioned hollow metal optical waveguide, taking advantage of the characteristic that not only light but also electricity can be passed because the waveguide is made of metal, and it has a simple structure. It is to provide a laser light transmission device having extremely high safety.

[Means for Solving the Problems] In the laser light transmission device of the present invention, a metal protective tube and a metal hollow optical waveguide inserted in the metal protective tube are made of a heat-resistant resin or a heat-resistant resin except for the vicinity of the waveguide emission end. A measurement device that electrically insulates with a curable resin and that is electrically connected in series on the waveguide output end side, and that measures the electrical resistance between the series-connected metal hollow optical waveguide and the metal protection tube. A control device is provided to send a stop signal to the laser light source device when the resistance value exceeds a predetermined value so as to cut off the laser light propagating through the hollow optical waveguide.

As another aspect of the present invention, a metal protective tube and a metal hollow optical waveguide inserted into the metal protective tube are insulated by a thermoplastic resin over the entire length thereof, and the metal hollow optical waveguide and the metal protective tube are insulated from each other. Measuring device for measuring electric resistance value, and control device for sending a stop signal to the laser light source device to cut off the laser light propagating through the hollow optical waveguide when the measured electric resistance value becomes less than a predetermined value And are provided.

[Operation] In the case where the metal protection tube and the metal hollow optical waveguide are insulated by a heat resistant resin or a thermosetting resin and electrically connected in series, when the temperature of the waveguide increases due to damage or the like , The total resistance of the series circuit becomes abnormally high. Therefore, the measured electrical resistance value exceeds the predetermined value of the control device, a stop signal is sent to the laser light source device, and the laser light propagating through the hollow optical waveguide is blocked.

Further, in the form in which the metal protective tube and the metal hollow optical waveguide are insulated by the thermoplastic resin, when the temperature of the waveguide rises due to damage or the like, the thermoplastic resin melts due to the temperature rise, The metal protection tube and the metal hollow optical waveguide are short-circuited, and the resistance value between the two becomes abnormally low. Therefore, the measured electric resistance value falls below a predetermined value of the control device, a stop signal is sent to the laser light source device, and the laser light propagating through the hollow optical waveguide is blocked.

Therefore, in any of the embodiments, it is possible to reliably detect the temperature rise of the metal hollow optical waveguide containing the thin film having a small absorption in the wavelength band of the transmitted laser light and prevent the waveguide from being damaged.

[Embodiment] An embodiment of the present invention will be described below with reference to FIGS. 1 and 2.

In FIG. 1, a metal hollow optical waveguide 2 is inserted into a metal protective tube 1, and the metal protective tube 1 and the metal hollow optical waveguide 2 are made of a heat-resistant resin or a thermosetting resin except for the vicinity of the exit end of the optical waveguide. It is insulated by the resin layer 3. Also,
The metal protection tube 1 and the metal hollow optical waveguide 2 are in contact with each other at the light emitting end of the optical waveguide either directly or through the metal holder 4, and thus both are electrically connected in series. Reference numeral 5 denotes a measuring device for measuring the resistance value of the series circuit of the metal protective tube 1 and the metal hollow optical waveguide 2.
A control device 6 for outputting a laser light transmission stop signal is connected to the laser light source device depending on the measurement result.

Copper or stainless steel is usually used for the metal protection tube 1, and the cross-sectional area thereof is sufficiently larger than the area of the metal hollow optical waveguide 2. Therefore, the total electrical resistance value when the both are connected in series is the metal hollow optical waveguide 2 Is almost equal to the electric resistance value of. On the other hand, the metal hollow optical waveguide 2 comprises, for example, the germanium-containing nickel hollow optical waveguide shown in FIG. Here, the thickness of the germanium layer 11 is about 0.5 μm, but since the nickel layer 12 not only contributes optically but also serves to maintain mechanical strength, the thickness is set to about 100 μm.
Since the thickness of the germanium layer 11 is sufficiently smaller than that of the germanium layer 12, the electric resistance of the metal hollow optical waveguide 2 in the longitudinal direction is determined exclusively by the nickel layer 12. Therefore, the total resistance value of the series circuit measured by the measuring device 5 is also determined by the resistance of the nickel layer 12.

In detail, the specific resistance of nickel at room temperature is 7 × 10 ^-6
Since it is Ωcm, if the inner diameter of the metal hollow optical waveguide is 1.5 mm and the length is 1 m, the total resistance value from the entrance end to the exit end of the metal hollow optical waveguide is 0.14 Ω.

Now, the length of 10 cm in the hollow metal optical waveguide 2 is 300 ° C (specific resistance 2
3 × 10 ^-6 Ωcm), the total resistance is 0.17
If the resistance increases to Ω and reaches 700 ° C (specific resistance 40 × 10 ^-6 Ωcm), the total resistance increases to 0.20Ω. When the measuring device 5 outputs a measurement result of such a high resistance value which is different from usual, the control device 6 connected thereto sends a stop signal to the laser light source device (not shown) to cause the laser Block light. Since the melting point of nickel is 1455 ° C., by cutting off the laser light immediately when the electric resistance value is detected, as a result, the laser light is cut off before the metal hollow optical waveguide 2 is thermally damaged. it can. Further, the phenomenon that the electric resistance of the metal hollow optical waveguide 2 changes to a high value is caused not only by the local temperature rise but also by the crack of the metal hollow optical waveguide due to mechanical fatigue, and thus the laser light The shutoff of the metal acts as an effective safety measure against mechanical damage as well as thermal damage.

As described above, in the present invention, the metal layer forming the metal hollow optical waveguide also serves as a temperature sensor, and the laser light is blocked when the electric resistance value of the metal portion exceeds a predetermined value. It is a feature.

As a material of the heat resistant resin or the thermosetting resin 3 which insulates the metal protective tube 1 and the metal hollow optical waveguide 2 from each other, a fluororesin, an epoxy resin, a polyimide resin, a urethane resin or the like is used, and its thickness It is desirable that the length is several tens of μm or more.

FIG. 2 shows a thermoplastic resin 30 in which the metal protective tube 1 and the metal hollow waveguide 2 are provided over the entire length of the metal hollow waveguide 2 in the form in which the metal hollow optical waveguide 2 is inserted into the metal protective tube 1. It is the example insulated by.

In the embodiment shown in FIG. 2, when the temperature of the hollow metal optical waveguide 2 suddenly rises, the thermoplastic resin 30 is melted and an electrical short circuit occurs between the metal protective tube 1 and the hollow metal optical waveguide 2. Therefore, the electric resistance value between them shows an extremely small value.
When the measuring device 5 measures this extremely small electric resistance value, the control device 6 generates a stop signal and shuts off the laser beam as in the above case. Therefore, it is possible to prevent the laser light from leaking without damaging the metal hollow optical waveguide 2 or the metal protection tube 1. Examples of the thermoplastic resin 30 include polyethylene, ethylene ethyl acrylate, and ethylene vinyl acetate, and the thickness thereof is preferably several μm or less.

The third type of metal hollow optical waveguide used in the present invention is
The present invention is applicable not only to those shown in the drawing, but also to the case where a metal other than nickel, for example, copper, silver, etc. is used, or where these different kinds of metals are multilayered.

[Advantages of the Invention] As described above, according to the present invention, it is possible to reliably detect the temperature rise of the metal hollow optical waveguide from the change in the measured resistance value and prevent damage to the waveguide in advance. As a result, a highly safe laser light transmission device can be obtained.

Further, the metal layer of the metal hollow optical waveguide has heretofore merely made an optical or mechanical contribution, but the present invention positively utilizes the electrical characteristics of the metal hollow optical waveguide itself. Therefore, when transmitting high-power laser light, it is not necessary to add a special sensor for temperature detection to the optical waveguide, and the configuration is extremely simple.

[Brief description of drawings]

1 and 2 are vertical cross-sectional views showing an embodiment of the laser light transmission device of the present invention, and FIG. 3 is a cross-sectional view of a metal hollow optical waveguide to which the present invention is applicable. In the figure, 1 is a metal protective tube, 2 is a metal hollow optical waveguide, 3 is a resin layer made of heat resistant resin or thermosetting resin, 4 is a metal holder, 5 is a measuring device, 6 is a control device, and 11 is a germanium layer. , 12 is a nickel layer, 13 is a hollow region, and 30 is a thermoplastic resin layer.

Claims (2)

[Claims] 1. A metal protective tube and a metal hollow optical waveguide inserted into the metal protective tube are insulated by a heat resistant resin or a thermosetting resin except for the vicinity of the waveguide emission end, and
A measuring device that is electrically connected in series on the output end side of the waveguide and that measures the electrical resistance value between the metal hollow optical waveguide and the metal protection tube connected in series, and the measured electrical resistance value exceeds a specified value. And a control device for interrupting the laser light propagating in the hollow optical waveguide by sending a stop signal to the laser light source device. 2. A metal protective tube and a metal hollow optical waveguide inserted into the metal protective tube are insulated by a thermoplastic resin over the entire length thereof, and an electric resistance value between the metal hollow optical waveguide and the metal protective tube is measured. A measuring device for measuring and a control device for interrupting the laser light propagating through the hollow optical waveguide by sending a stop signal to the laser light source device when the measured electric resistance value becomes a predetermined value or less are provided. A laser light transmission device characterized by the above.