JP2000221108A - Soundness inspection instrument for optical fibers - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a more convenient instrument which can inspect soundness of an optical fiber before a high output laser is introduced into an optical fiber and can inspect the state of an optical fiber, even during laser machining. SOLUTION: A soundness inspection equipment applicable to a laser machining system, comprising a laser oscillator 1 for machining, an optical fiber 3 and a laser machining head 4, includes a laser oscillator 2 for inspection generating an inspection laser light having wavelength different from that of machining laser light. The inspection laser light introduced to the optical fiber 3 and returning from the laser machining head 4 is detected in the vicinity of the emission end of machining laser light, thus detecting abnormality of the optical fiber 3 and the laser machining head 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting the soundness of an optical fiber for transporting a high-power laser, and particularly to the soundness of a light guiding fiber connected to an optical system such as a processing head. To a device that

[0002]

2. Description of the Related Art In a laser processing apparatus for processing a target object by irradiating a high-power laser beam, when light is guided using an optical fiber, laser light reflected by the workpiece returns along the same optical path as the irradiation optical path. The fiber may hit the end of the optical fiber and be damaged by heating. To prevent high-intensity laser light from returning directly to the optical fiber, the optical axis of the laser light may be slightly shifted from the normal direction of the object surface, but irregular reflection occurs at the processed part of the laser light. There is a component and a heat radiation component from the processed portion, and these converge at the exit end position of the optical fiber by following a reverse path to that in laser beam irradiation.

At this time, if the aim is deviated from the core portion of the optical fiber and irradiates the peripheral portion, the resin coating or the like having low heat resistance may be melted or burned by strong laser light and lose the function of the optical fiber. become. Further, a laser beam may leak from the damaged optical fiber and cause a fire.
Also, if the optical fiber is broken inside the optical fiber cable, not only does the processing laser not reach the target object, but the laser light leaking from the damaged part will damage the coated part and surrounding equipment and cause a fire There is danger.

[0004] In order to detect such danger at an early stage, a laser processing apparatus provided with a monitor device for inspecting the soundness of the light guide fiber has been used. As such a monitor device, for example, an illumination light for inspection is injected into the end face of the light guide fiber on the laser emission side, and the illumination light propagating in the light guide fiber is measured at the end face of the light input side. There was something that detected. The safety can be ensured by confirming that there is no abnormality in the optical fiber using the monitor device and then irradiating the processing laser. However, in this method, it is necessary to equip a special part such as an illuminating device on the processing side end face, which is inconvenient to use.In addition, while the high-power laser is supplied, there is an excessive difference in light intensity. Since detection cannot be performed, there is an inconvenience that inspection cannot be performed during execution of laser processing or the like.

On the other hand, Japanese Patent Application Laid-Open No. 60-210387 discloses
In this publication, an optical sensor is provided axially symmetrically around the laser input end of the light guide fiber, reflected by the workpiece, returned to the laser output end, propagated through the optical fiber, and emitted from the input end. An apparatus has been disclosed which detects a deviation in the emission angle distribution of laser light to detect an abnormality in the optical fiber and blocks the laser light to prevent damage to the optical fiber. According to the disclosed method, it is not necessary to provide a large device in the processing head portion, so that the processing head can be easily handled and a defect of the optical fiber can be detected during the processing. However, since a defect of the optical fiber is detected only when the processing laser is irradiated onto the optical fiber, an accident cannot be prevented by knowing the defect before use.

Further, Japanese Patent Application Laid-Open No. 5-277775 discloses a method for inspecting the soundness of an optical fiber using reference light having a wavelength different from that of the processing laser light. This method includes a mirror that selectively reflects the detection laser light at a position where a parallel light beam is formed in a collimator formed in the processing head, and irradiates the detection laser light with the processing laser light into the optical fiber, The laser beam for detection is reflected by the reflection mirror, transmitted through the optical fiber again, and returned to the incident side. During laser processing, the detector measures the intensity of the detection laser light or the presence or absence of the laser light, and based on the result, stops the output of the processing laser oscillator, thereby maintaining the safety of the laser processing device and surrounding equipment can do.

In the apparatus disclosed in the above publication, it is necessary to dispose a mirror in a collimator of a processing optical system, reflect a detection laser beam as a parallel beam, return it to the exit end of the optical fiber by following a reverse path. There is. The processing optical system is mainly designed and manufactured so as to be compatible with the processing laser. However, the inspection laser light having a different wavelength must be accurately focused at the emission end. Therefore, strict design and precise fabrication of the processing optical system are required, and the apparatus tends to be expensive.

[0008]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a simpler inspection method capable of inspecting the soundness of an optical fiber before introducing a high-power laser into the optical fiber. It is an object of the present invention to provide an apparatus and a simpler optical fiber soundness inspection apparatus capable of inspecting the state of an optical fiber even during laser processing.

[0009]

In order to solve the above problems, an optical fiber soundness inspection apparatus according to the present invention comprises a processing laser oscillator for generating a processing laser light, an optical fiber for conveying the processing laser light, and , Which is applied to a laser processing device equipped with a laser processing head that converges the processing laser light emitted from the optical fiber and irradiates the object with the laser light, and generates an inspection laser light with a different wavelength from the processing laser light Inspection laser oscillator that detects the optical fiber abnormality by introducing the inspection laser light into the optical fiber and detecting the inspection laser light returning from the laser processing head near the emission end of the processing laser It is characterized by doing.

An optical fiber soundness inspection apparatus according to the present invention detects a component of an inspection laser beam transmitted through an optical fiber and reflected (including irregular reflection) upon hitting an optical system of a laser processing head. It is not necessary to focus on the processing laser light emitting end.
The soundness of the optical fiber can be confirmed without using a complicated and precise optical system such as that disclosed in Japanese Patent Publication No. 75-75. Since the optical fiber soundness inspection device of the present invention performs inspection using an inspection laser beam different from the processing laser beam, the soundness of the optical fiber is checked before passing the high-power processing laser beam. Can be highly secure.

Further, even during the laser processing, the inspection laser light reflected from the laser processing head can be captured and the abnormality of the optical fiber can be continuously monitored. In addition, when there is an abnormality in the optical system of the laser processing head, such as when the lens surface is stained due to the adhesion of metal fume or the like and the lens is overheated due to the absorption of the laser beam and the lens is damaged, the detection laser An abnormality can be detected by measuring the light intensity.

The photodetector may be constructed by providing an optical sensor near the laser light emitting end of the optical fiber. However, the photodetector may have a second light receiving end adjacent to the laser light emitting end of the optical fiber. May be guided to a remote light detection sensor by the optical fiber. When the second optical fiber is used in this manner, the second optical fiber is housed together in a sheath that houses the optical fiber through which the processing laser light is transmitted, and the light receiving end is the pole of the processing laser light emitting end. If they are arranged close to each other, the structure of the end portion of the optical fiber is simple and small, and the handling is easy.

It is preferable that the surface of the optical element of the laser processing head is provided with a coating for reflecting the inspection laser light. By applying a coating that has a high reflectance with respect to the inspection laser light and prevents reflection with respect to the processing laser light, it is possible to increase the optical fiber abnormality detection capability without lowering the processing efficiency.
Alternatively, a protective glass may be provided at the position closest to the workpiece in the optical system of the laser processing head, and the protective glass may be provided with a coating for reflecting the inspection laser light. The protective glass, together with the purge of the assist gas, prevents the metal fume generated in the processing portion from contaminating the optical system.

Since the protective glass is a flat plate, it is relatively easy to apply a wavelength-selective coating to the surface. At the position of the protective glass, the laser light is a light beam that tends to converge, so the inspection laser reflected by the protective glass does not focus on the emission end of the processing optical fiber,
The light spreads greatly on the laser light emitting surface of the optical fiber, and is incident on the optical sensor installed adjacent to the emitting end or the light receiving end of the second optical fiber. Note that an iodine laser generator can be used as a processing laser oscillator.
The iodine laser is an infrared laser and can be relatively easily increased in output, and can be used for laser processing utilizing thermal action such as welding and fusing.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on embodiments with reference to the drawings. FIG. 1 is an overall configuration diagram showing a laser processing apparatus using a first embodiment of an optical fiber soundness inspection apparatus of the present invention, FIG. 2 is an electric circuit block diagram of the photodetector, and FIG. FIG. 4 is a cross-sectional view of a laser processing head used in the second embodiment, FIG. 4 is a diagram illustrating an optical path of the inspection laser light, and FIG. 5 is a configuration diagram illustrating a photodetector used in the third embodiment of the present invention. It is.

[0016]

Embodiment 1 In this embodiment, a reference laser having a wavelength different from that of a processing laser is applied to an optical fiber, transmitted and propagated through the optical fiber, reflected by an optical system of a laser processing head, and returned. This is an optical fiber soundness inspection device that detects an abnormality of an optical fiber by observing a laser. The optical fiber soundness inspection apparatus according to the present embodiment includes a first laser oscillator 1 that generates a processing laser, a second laser oscillator 2 that generates a reference laser, and an optical fiber cable 3 that transmits laser light. , A laser processing head 4, and a photodetector 5 for receiving a reference laser reflected from the laser processing head 4.

The first laser oscillator 1 is an iodine laser generator, and the second laser oscillator 2 is a He-Ne laser generator. The optical fiber cable 3 contains a first optical fiber 31 and a second optical fiber 51. First optical fiber 3
1 is for transmitting a processing laser and an inspection laser (reference light), and the second optical fiber 51 is an optical fiber for transmitting a reflected reference light and an iodine laser. The first optical fiber 31 is connected to an incident optical system for guiding laser light from the laser oscillators 1 and 2 and the second optical fiber 51 is connected to a branch fitting 32 disposed in the middle of the optical fiber cable 3.
Are branched so as to be connected to the light detection end 53.

An incident optical system for injecting a laser beam into the first optical fiber includes a reflecting mirror 11 and a converging lens 13.
The reflecting mirror 11 is surface-treated so as to totally reflect the iodine laser and transmit the He-Ne laser. The iodine laser emitted from the first laser oscillator 1 is reflected by the reflecting mirror 11 and injected into the first optical fiber 31 by the focusing lens 13. The reference laser emitted from the second laser oscillator 2 passes through the reflecting mirror 11 and is injected into the first optical fiber 31 through the focusing lens 13 with the same optical axis as the iodine laser. The distal end of the first optical fiber 31 is inserted into the root of the laser processing head 4, and the laser light emitted from the distal end is converged by the processing lens system and irradiates the processing position of the processing target object 8, for welding fusing and the like. Laser processing.

The reference laser beam transmitted through the first optical fiber 31 is reflected by the collimator and enters the second optical fiber 51. Light receiving end 52 of second optical fiber 51
Is provided close to the optical axis of the first optical fiber 31. Since the reference laser beam received by the light receiving end 52 may be irregularly reflected by the optical system of the collimator, it is not necessary to provide an optically precise structure as in the conventional method. By applying a surface treatment to the optical lens in the collimator portion for transmitting the processing laser and reflecting the reference light having a different wavelength from the processing laser, it is possible to increase the reference light capture rate while maintaining the processing efficiency.

The reference laser beam incident on the second optical fiber 51 from the light receiving end 52 is transmitted to the light detecting end 53 of the photodetector 5, and the light intensity and the presence or absence of light are measured and detected to determine the quality of the optical fiber 31. Then, the iodine laser device 1 is controlled to ensure the safety of the device. The configuration of the photodetector 5 is as shown in FIG. The second optical fiber 51 is connected to an optical connector 54,
The reference laser captured by the light receiving end 52 is transmitted to the optical sensor 56. The optical sensor 56 is a photodiode having sensitivity to visible light. A photocell or the like can be used in addition to the photodiode.

The optical connector 54 is provided with a filter 55 for selectively transmitting the wavelength band of the reference laser to shield light other than the reference light, and only the reference laser light reaches the optical sensor 56. It has become. The output of the optical sensor 56 is amplified by an amplifier 57 and sent to a comparator 58. The comparator 58 compares the output with a threshold value. When the output does not belong to a predetermined range and when the output is small, it is determined that there is an abnormality and the alarm lamp 60 is turned on. Then, a signal is sent to the output circuit 61. The output circuit 61 operates a contact relay or a non-contact relay based on this signal to supply a drive signal 62 to a laser generator or the like.
The laser generator receives a drive signal and closes a shutter or stops laser beam oscillation to ensure the safety of the device. The threshold value used in the comparator 58 is the external setting signal 59
Can be set.

For the optical fiber laser processing, an infrared laser capable of increasing the output, such as an iodine laser or a YAG laser, is used. In this embodiment, a high-output iodine laser is used. However, there is no difference in the technical idea of the present invention whatever the laser for laser processing. The reference laser may be any laser that has a wavelength different from that of the iodine laser used for laser processing and can be easily distinguished optically. In this embodiment, a He-Ne laser, which is a visible light laser that is easy to handle, is selected. did.

In the laser processing apparatus incorporating the optical fiber soundness inspection apparatus of the present embodiment, it is only necessary to expose the light receiving end 52 of the second optical fiber to the laser processing head 4 and there is no need to provide an extra attachment. . Further, since the second optical fiber 51 having high flexibility is merely attached to the optical fiber cable 3 and does not impair the flexibility of the cable, the laser processing head 4 can be freely operated, and the laser Does not hinder operability in processing. Also, the processing head 4 can use the conventional one as it is, and there is no need to modify it to use this optical fiber soundness inspection apparatus.

In the laser processing apparatus to which this embodiment is applied,
The reference light is injected before the processing laser is injected into the first optical fiber 31, and the reference light reflected from the laser processing head 4 after passing through the first optical fiber 31 is observed. At this time, if there is an abnormality in the first optical fiber 31, the reference light is not sufficiently transmitted to the end and the amount of received light is reduced, so that the soundness of the first optical fiber 31 can be confirmed. Also,
When there is no lens in the laser processing head 4, the amount of received light is small, and when the lens or the like is contaminated with metal fume or the like, the amount of received light is large.

For this reason, by detecting the intensity of the reference light, a high-output processing laser is injected into an unhealthy optical fiber to cause an accident such as a fire or use an abnormal laser processing head. Can be reliably prevented.
In addition, even during laser processing, an inspection laser is injected into the first optical fiber 31 together with the processing laser, and the amount of light received by the inspection laser is observed. Can be detected.

[0026]

Embodiment 2 The second embodiment of the present invention is different from the first embodiment in that a laser processing head is provided with a protective glass, and the protective glass transmits a processing laser and reflects an inspection laser. This optical fiber soundness inspection device differs only in that the surface treatment is performed. Hereinafter, portions different from the first embodiment will be described in detail. In the following description, components having the same functions as in the first embodiment will be simplified by using the same reference numerals.

FIG. 3 is a partial sectional view showing a portion of the laser processing head 4. The first end of the laser processing head 4
The optical fiber cable 3 containing the optical fiber 31 and the second optical fiber 51 is inserted and optically connected. The axis of the first optical fiber 31 is aligned with the central axis of the laser processing head 4, and the tip of the second optical fiber 51 is exposed at a position slightly eccentric from the central axis. The laser processing head 4 has a cylindrical shape, and two sets of convex lens systems 41 and 42 and a protective glass 48 are incorporated in the internal cavity. The protective glass 48 is subjected to a surface treatment that transmits a processing laser and reflects an inspection laser. Since the protective glass 48 is a flat plate, the surface treatment is much easier than applying it to the lens.

An assist gas is introduced downstream of the protective glass 48 from a gas nozzle 44 provided on the side surface, and generates an air flow for purging toward the opening of the processing nozzle 45 at the tip of the laser processing head 4, thereby causing a laser beam. The optical system in the processing head 4 is prevented from being contaminated by metal fumes or the like generated in the processing section. A processing laser and an inspection laser are emitted from the first optical fiber 31. As shown by the solid line in FIG. 4, the processing laser is converted into a parallel beam by the first convex lens system 41, converged by the second convex lens system 42, passes through the opening at the tip of the processing nozzle 45, and To perform laser processing. The processing laser may be reflected at the processing portion, but this reflection component follows an optical path opposite to that at the time of irradiation, focuses on the distal end position of the first optical fiber 31, and moves backward through the first optical fiber 31. Emitted from the entrance end.

On the other hand, the inspection laser is reflected by the protective glass 48 provided at a position where it becomes a converging light beam, passes through the two sets of lens systems 42 and 41, and returns to the distal end position of the optical fiber cable 3. Since this return path is diffused at the tip end of the optical fiber cable 3 unlike the path in the irradiation direction, as shown by the broken line in FIG. 4, the reflected inspection laser is transmitted to the light receiving end 52 of the second optical fiber 51. Incident. The inspection laser incident on the second optical fiber 51 changes its light intensity when there is an abnormality such as damage to the first optical fiber 31 or when the lens system is contaminated, and when there is no lens system or when the protective glass is used. When the laser beam is broken, the laser beam does not return.

If there is an error in the optical system, it deviates from the core of the first optical fiber 31 and hits a thermally weak coating portion.
The optical fiber cable 3 may be burned. In such a case, the light generated due to the combustion is mixed and the intensity of the light transmitted to the light detection sensor via the second optical fiber 51 becomes unstable, so that the failure can be estimated.

[0031]

Embodiment 3 FIG. 5 is a block diagram showing a photodetector used in a third embodiment of the present invention. In this embodiment,
In addition to the inspection laser, the processing laser that is incident on the light receiving end of the second optical fiber 51 is measured and the information is combined to more reliably detect a failure. Hereinafter, portions different from the above embodiment will be described in detail, and components having the same functions as those in the above embodiment will be simplified by using the same reference numerals.

The light detector 5 comprises a second optical fiber 51 having a light receiving end 52 exposed in the laser processing head 4 and a light detecting end 53 to which the second optical fiber 51 is connected via an optical connector 54. . The light detection end 53 is connected to the second optical fiber 51.
The laser light transmitted in the step is optically branched, and the processing laser light and the inspection laser light are respectively measured. Inside the light detection end 53, a focusing lens 63, a dichroic mirror 64, band-pass filters 65 and 67, an optical sensor 66,
68, a signal processing device 69 is housed. The dichroic mirror 64 has been subjected to a surface treatment that transmits the inspection laser light and reflects the processing laser light. The band-pass filter 65 provided at a position where the light passes through the dichroic mirror 64 is coated with a coating for transmitting the inspection laser light.
The band-pass filter 67 on which the light reflected by the laser beam enters is provided with a coating for transmitting the processing laser light.

The laser light emitted from the second optical fiber 51 is changed to parallel light by the focusing lens 63 and enters the dichroic mirror 64. From the laser beam that has passed through the dichroic mirror 64 and travels straight, only the inspection laser beam component is extracted by the band-pass filter 65 and is incident on the optical sensor 66 to measure the light intensity. On the other hand, dichroic mirror 6
From the laser light reflected by 4, only the processing laser light component is extracted by the band-pass filter 67 and measured by the optical sensor 68. The measurement outputs of the optical sensors 66 and 68 are output from the signal processor 6.
9 and each is compared with a threshold value to determine whether there is an abnormality in the optical fiber or the laser processing head.
When there is a fear that an abnormality has occurred, an alarm is issued by a lamp or sound, and the laser oscillator is directly stopped as necessary to prevent an accident.

First optical fiber 3 for carrying a processing laser
1 is abnormal, the light receiving end 5 of the second optical fiber 51
Since the inspection laser received in step 2 becomes weaker, and when the coating of the optical fiber cable 3 burns and emits flame, the measurement output of the optical sensor 68 becomes unstable. The abnormality can be detected as described in the first embodiment or the second embodiment. While there is no problem while the processing laser reflected by the workpiece returns to the core portion of the first optical fiber 31 by reversely tracing the optical path at the time of irradiation, the surrounding coating is overheated when the processing laser is removed from the core. It is dangerous because it burns. The optical fiber integrity inspection device of the present embodiment can more directly detect such danger.

[0035]

As described above, by applying the optical fiber soundness inspection apparatus of the present invention, an optical fiber can be inspected before a high-power laser is introduced into the optical fiber. Can also check the condition of the optical fiber,
In addition, it is possible to provide a laser processing apparatus having a laser processing head that is simpler and more operable than the conventional technique.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram showing a laser processing apparatus using a first embodiment of an optical fiber soundness inspection apparatus of the present invention.

FIG. 2 is an electric circuit block diagram of the photodetector in the first embodiment.

FIG. 3 is a sectional view of a laser processing head portion used in a second embodiment of the optical fiber soundness inspection apparatus of the present invention.

FIG. 4 is a diagram illustrating an optical path of a test laser beam in a second embodiment.

FIG. 5 is a configuration diagram illustrating a photodetector used in a third embodiment of the optical fiber soundness inspection apparatus of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 first laser oscillator 11 reflecting mirror 13 focusing lens 2 second laser oscillator 3 optical fiber cable 31 first optical fiber 4 laser processing head 41, 42 convex lens system 44 gas nozzle 45 processing nozzle 48 protective glass 5 photodetector 51 second light Fiber 52 Light receiving end 53 Light detecting end 54 Optical connector 55 Filter 56 Optical sensor 57 Amplifier 58 Comparator 59 External setting signal 60 Alarm lamp 61 Output circuit 62 Drive signal 63 Focusing lens 64 Dichroic mirror 65, 67 Bandpass filter 66, 68 Light Sensor 69 signal processing device

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G086 CC05 CC06 CC07 2H038 AA01 AA58 5F072 AA01 AA07 JJ05 KK05 KK30 MM09

Claims (5)

[Claims] 1. A processing laser oscillator for generating a processing laser light, an optical fiber for carrying the processing laser light, and a laser for converging the processing laser light emitted from the optical fiber to irradiate the object. A laser processing apparatus having a processing head, comprising: an inspection laser oscillator that generates an inspection laser light having a wavelength different from the processing laser light; and a photodetector that detects the inspection laser light. Is introduced into the optical fiber and the inspection laser light returning from the laser processing head is measured by the photodetector at a position adjacent to the laser light emitting end of the optical fiber, and the abnormality of the optical fiber is measured. Optical fiber integrity inspection device to detect. 2. The optical detector includes a second optical fiber and a light detection sensor, and the light is reflected by the second optical fiber having a light receiving end disposed adjacent to a laser light emitting end of the optical fiber. 2. The optical fiber soundness inspection apparatus according to claim 1, wherein the inspection laser light is guided to the light detection sensor. 3. The optical fiber soundness inspection apparatus according to claim 1, wherein the optical element of the laser processing head has a surface coated with a coating reflecting the inspection laser light. 4. The laser processing head according to claim 1, wherein the optical system of the laser processing head includes a protective glass coated with a coating reflecting the inspection laser light at a position closest to the workpiece. An optical fiber soundness inspection device according to item 1. 5. The optical fiber integrity inspection apparatus according to claim 1, wherein said processing laser oscillator is an iodine laser generator.