JP7194883B2 - FAILURE DETECTION DEVICE, LASER PROCESSING SYSTEM AND FAILURE DETECTION METHOD - Google Patents

Description

TECHNICAL FIELD The present disclosure relates to an optical fiber failure detection device, laser processing system, and failure detection method, and more particularly to an optical fiber failure detection device, laser processing system, and failure detection method that transmits high-power processing laser light.

A high-power processing laser beam from a direct diode laser (DDL) light source, etc. is transmitted to the processing head via an optical fiber, and by condensing and irradiating it, the workpiece (work) can be welded, fused, and perforated. Such laser processing systems are widely used. In such an optical fiber, if the optical fiber is broken while transmitting the processing laser beam, the output energy of the processing laser beam is large, so there is a risk of damaging the coating resin of the optical fiber and other peripheral devices. Therefore, a laser processing system that utilizes high-power processing laser light is generally provided with a device for detecting disconnection of the optical fiber that transmits the laser light.

Many devices have been proposed so far for detecting disconnection of an optical fiber that transmits high-power laser light. As a disconnection detection device according to the prior art, for example, a closed circuit is configured using a coated wire arranged along an optical fiber that transmits a laser beam, and the closed circuit is disconnected (opened) due to heat generated when the optical fiber is disconnected. Alternatively, it has been proposed to detect disconnection of an optical fiber by electrically detecting a short circuit.

Still another disconnection detection device has a tube for circulating gas placed along the optical fiber instead of the coated wire, monitors the flow rate of the circulating gas, and detects disconnection of the optical fiber when the flow rate of the circulating gas changes. It has also been proposed to determine

Another disconnection detection device is a laser processing system in which a laser beam (processing laser beam) for processing a workpiece is transmitted through an optical fiber. A pair of photodetectors monitor the output intensity), and based on the difference in the light intensity of the processing laser beam measured by each photodetector or the change in the relative value, the breakage of the optical fiber or the energy loss due to the optical fiber is detected. Detectors are also used.

More specifically, the optical fiber break detection device described in Patent Document 1 includes an optical fiber that transmits a high-energy processing laser beam for processing a workpiece, and an optical fiber near the incident end and the exit end of the optical fiber. is provided with a pair of light receivers and a detection unit that compares the outputs of these light receivers and detects breakage of the optical fiber.

Further, the optical fiber device for laser transmission described in Patent Document 2 similarly includes an optical fiber for transmitting power laser light for processing a workpiece, and a visible light selection device disposed near the output end of the optical fiber. and a light receiving detector arranged near the incident end of the optical fiber for receiving the power laser light and the visible light selected by the visible light selective reflecting means. This visible light is generated by burning the coating material of the optical fiber due to disconnection of the optical fiber or the like. The optical fiber device for laser transmission detects an abnormality such as disconnection of the optical fiber by comparing the light intensity of the power laser beam and the visible light.

JP-A-10-038751 JP-A-07-266067

However, in a disconnection detection device using a coated wire or gas circulation tube, even if the optical fiber is not disconnected, the closed circuit of the coated wire separate from the optical fiber is disconnected or short-circuited, or the circulating gas is discharged. When the flow rate changes, it may be erroneously detected as disconnection of the optical fiber. For example, in a disconnection detection device using a coated wire, when a pair of coated wires forming a closed circuit are peeled off due to friction with an optical fiber, the pair of core wires of the coated wire come into contact (short circuit), and the disconnection detection function operates. Sometimes.

Further, the techniques described in Patent Document 1 and Patent Document 2 both use a high-output laser for processing a workpiece to detect disconnection. Specifically, a processing laser beam incident on and emitted from an optical fiber (Patent Document 1), or a power laser beam incident on an optical fiber and visible light emitted from the optical fiber (Patent Document 2) are compared. , to detect breaks in optical fibers. However, the output intensity of the laser beam (processing laser beam) for processing the material to be processed fluctuates due to the operating state or usage time of the laser light source device, and the transmittance of the optical fiber changes substantially. It's easy to do. Therefore, it is difficult to detect the transmission loss or the like of the optical fiber by using the optical fiber itself that transmits the processing laser light, and there is a risk of erroneous detection or the like.

In addition, the processing laser light (Patent Document 1) and the visible light generated by burning the coating material (Patent Document 2) generally have a wide wavelength band. density), it is likely to interfere with the Rayleigh scattered light (scattered light generated by the light scattering phenomenon caused by particles smaller than the wavelength of light) generated within the optical fiber, and the processing laser light or visible light is unstable. , may also lead to erroneous detection and the like.

A first aspect of the present disclosure relates to an optical fiber failure detection device, which includes a processing laser light source that emits processing laser light, a detection laser light source that emits detection laser light, and a detection laser light. A spectroscope for splitting into first and second partial beams, a first receiver for measuring the intensity of the first partial beam of the detection laser beam, and a second portion of the detection laser beam from the input end to the output end. The optical fiber transmitting the light and the processing laser light, and the second partial light transmitted by the optical fiber and emitted from the output end of the optical fiber are partially reflected toward the output end of the optical fiber, and partially reflected toward the output end of the optical fiber. a second light receiver for measuring the intensity of the transmitted light of the second partial light transmitted by the reflecting/transmitting part; a reflecting/transmitting part that reflects the light toward the output end of the optical fiber ; a third light receiver for measuring the intensity of the reflected light of the second partial light transmitted by the optical fiber and emitted from the incident end of the optical fiber; and the first partial light measured by the first light receiver. The relative ratio of the intensity of the second partial light measured at the second receiver to the transmitted light , and the first partial light measured at the first receiver and the third light receiver measured a determination unit that determines whether or not there is a problem with the optical fiber based on the relative ratio of the intensity of the second partial light to the reflected light.

The failure detection device according to the present disclosure can detect disconnection of an optical fiber with higher reliability by using stable detection laser light transmitted through an optical fiber instead of processing laser light.

FIG. 1 is a block diagram showing a schematic configuration of a failure detection device according to Embodiment 1. FIG. FIG. 2 is a block diagram showing a schematic configuration of a failure detection device according to Embodiment 2. As shown in FIG. FIG. 3 is a block diagram showing a schematic configuration of a failure detection device according to Embodiment 3. As shown in FIG.

First, a schematic configuration of the present disclosure will be described. A failure detection device according to each aspect of the present disclosure includes a processing laser light source that emits processing laser light, a detection laser light source that emits detection laser light, and a spectrometer that divides the detection laser light into first and second partial lights. a first light receiver for measuring the intensity of the first partial light of the detection laser light; and an optical fiber for transmitting the second partial light of the detection laser light and the processing laser light.

A fault detection device according to a first aspect includes a second light receiver that measures the intensity of the second partial light transmitted by the optical fiber, and the first and second light receivers measured by the first and second light receivers. a determination unit that determines whether or not there is a problem with the optical fiber based on the relative ratio of the intensities of the two partial lights. The detection laser beam has a shorter peak wavelength and a smaller half width (the width of the wavelength that is half the peak value of the peak wavelength, and indicates the degree of spread in the wavelength direction) compared to the processing laser beam. (narrower wavelength band) and smaller output intensity. Also, the detection laser light (and thus the second partial light) is more stable with less loss of light intensity during transmission through the optical fiber than the processing laser light. The wavelength dependence of the transmission loss of an optical fiber mainly differs depending on the material of the optical fiber. Also, the peak wavelength of the detection laser light mainly differs depending on the light source of the detection laser light. By appropriately selecting the light source of the detection laser light, it is possible to obtain the detection laser light with less light intensity loss in the optical fiber than the processing laser light. Since the determination unit according to the first aspect uses stable detection laser light, it is configured to detect defects such as disconnection of the optical fiber with high reliability.

A fault detection device according to a second aspect includes a reflector that reflects a second partial light transmitted through an optical fiber toward the optical fiber, and a second portion that is reflected by the reflector and transmitted through the optical fiber. on the basis of a third receiver measuring the intensity of the reflected light of the light and the relative ratio of the reflected light intensities of the first partial light and the second partial light measured at the first and third receivers , and a determination unit that determines whether or not there is a problem with the optical fiber. Since the determination unit according to the second aspect uses stable detection laser light, it is configured to detect defects such as disconnection of optical fibers with high reliability. In addition, the electrical wiring distance for transmitting the signal indicating the difference in light intensity can be shortened from the third photodetector to the failure determination unit, and the configuration of the failure detection device can be simplified. .

A failure detection device according to a third aspect includes a reflection-transmission unit that partially reflects the second partial light transmitted by the optical fiber toward the optical fiber and partially transmits the second partial light, and a reflection-transmission unit that partially transmits the second partial light. A second photodetector for measuring the intensity of the transmitted light of the second partial light that has been transmitted; and the first, second, and third optical receivers, based on the relative ratios of the transmitted and reflected light intensities of the first partial light and the second partial light measured at the optical fiber and a determination unit that determines whether or not there is a problem. The determination unit according to the third aspect is a combination of the first and second aspects, and uses a stable detection laser beam, so that failures such as disconnection of optical fibers can be detected with high reliability. is configured as

Next, an embodiment of an optical fiber failure detection device according to the present disclosure will be described below with reference to the accompanying drawings. In the description of each embodiment, directional terms (e.g., “left” and “right”) are used as appropriate for ease of understanding, but these terms are for description purposes only and are not used in the present specification. It is not intended to limit disclosure. In each drawing, a solid line indicates an electrical connection of each component of the optical fiber failure detection device, and a straight arrow indicates a traveling direction of each laser beam from each component (light source, etc.). In addition, the straight arrows in each drawing indicate that the optical axes of the laser beams are shifted in order to clarify the laser beams. It is a thing.

[Embodiment 1]
A first embodiment of a failure detection device 1 according to the present disclosure will be described with reference to FIG. FIG. 1 is a block diagram showing a schematic configuration of a failure detection device 1 according to the present disclosure. As shown in FIG. 1, the failure detection apparatus 1 according to Embodiment 1 generally includes a processing laser light source 10, a detection laser light source 20, a half mirror 22 (spectroscope), and an optical fiber 30 (process fiber or transmission light source). ), first and second photodetectors 24 and 26 (light receivers), and a defect determination section 50 (simply referred to as a determination section). The laser processing system according to the present disclosure includes a system control section 60 electrically connected to the processing laser light source 10 and the defect determination section 50 of the failure detection device 1 . The laser processing system has a first containment chamber 16 and a second containment chamber 18 remote from the first containment chamber 16 . The first housing chamber 16 houses the processing laser light source 10 , the detection laser light source 20 , the half mirrors 12 and 22 , the first photodetector 24 , the condenser lens 36 , and the failure determination section 50 . A second housing chamber 18 houses a second photodetector 26 , a collimation lens 38 and a beam splitter 40 . The optical fiber 30 physically and optically connects the first storage chamber 16 and the second storage chamber 18 . The first containment chamber 16 is, for example, a space defined by a housing of the device or a room of the building. The same applies to the second storage chamber 18 .

The processing laser light source 10 emits an arbitrary high _- power processing laser beam LP for processing a workpiece (workpiece, not shown). Processing is, for example, welding, fusing and drilling. The processing laser light source ¹⁰ is, for example, a direct diode laser ( _DDL ) light source. The processing laser beam _LP is reflected by a half mirror 12 arranged at an angle of 45 degrees with respect to the optical axis of the processing laser beam _LP , and directed (guided) to an optical fiber 30 . The half mirror 12 substantially totally reflects light in the above wavelength band of the processing laser light _LP , and substantially totally transmits light with a shorter wavelength such as the detection laser light _LD described later. preferable.

The detection laser light source 20 emits a detection laser beam _LD for detecting defects such as disconnection of the optical fiber 30 . The detection laser light source 20 emits detection laser light having a peak wavelength shorter than that of the processing laser light LP, a narrower wavelength band (600 nm±5 nm), and an output intensity of several hundred _milliW (~1 W). It may be a neon (He—Ne) laser light source or a semiconductor laser light source. As shown in the figure, the detection laser beam _LD is a surface S1 of _another half mirror 22 (spectroscope) arranged at an angle of 45 degrees with respect to the optical axis. It reflects and the rest is transmitted. That is, the detection laser beam LD is split by the surface _S1 of the half mirror 22 into a _first partial beam _LD1 and a second partial beam _LD2 . The transmitted second partial light _LD2 enters the optical fiber 30 _coaxially with the processing laser light LP, and the reflected first partial light _LD1 enters the first photodetector 24 .

The first photodetector 24 receives the first partial light _LD1 of the detection laser light LD and _measures the light intensity of the first partial light _LD1 . Further, the first photodetector 24 supplies a signal P1 indicating the measured light intensity of the _first partial light _LD1 to the failure determination section 50 .

A condenser lens 36 is arranged between the half mirror 12 and the optical fiber 30 . The condensing lens 36 converges the second partial light _LD2 of the detection laser light _LD and the processing laser light _LP onto the incident end 32 of the optical fiber 30 . The second partial light _LD2 of the detection laser light LD and the processing laser light _{LP emitted} from the output end 34 of the optical fiber 30 are converted into parallel light by a collimation lens 38, and are then directed along the optical axis of the optical fiber 30. It is incident on the beam splitter 40 arranged at an angle of 45 degrees with respect to the beam.

The beam splitter 40 substantially totally reflects the light in the wavelength band equivalent to the second _{partial light LD2 of} the detection laser light LD toward the second photodetector 26, so that the light in the same wavelength band as the processing laser light _LP is reflected. substantially all of the light in the wavelength band of . That is, the second partial light _LD2 of the detection laser light _LD is incident on the second photodetector 26, and the processing laser light _LP is applied to the workpiece. Although not shown, another condenser lens may be arranged between the beam splitter 40 and the second photodetector 26 to collect the second partial light _LD2 .

The second photodetector 26 receives the second partial light _LD2 of the detection laser light _LD , measures the light intensity of the _second partial light _LD2 , and outputs a signal P2 indicating the light intensity. It is supplied to the defect determination unit 50 . The defect determination unit 50 compares the signals P ₁ and P ₂ indicating the light intensity supplied from the first and second photodetectors 24 and 26 to determine whether or not the optical fiber 30 has a defect such as disconnection. judge. For example, when the intensity ratio (r ₁ =P ₂ /P ₁ ) of the signals P ₁ and P ₂ is smaller than the threshold value Th ₁ (r ₁ <Th ₁ ), the defect determination unit 50 determines that the optical fiber 30 has a defect. You may When the optical fiber 30 is broken, typically, the second partial light _LD2 of the processing laser beam LP and the detection laser beam _LD is not emitted from the emission end 34 of the optical fiber 30, and the signal _P The intensity of ₂ is almost zero and the intensity _ratio r1 is also zero. At this time, the defect determination unit 50 can determine that the optical fiber 30 has been disconnected. It should be noted that the defect determination unit 50 may determine the defect based on the intensity difference between the signals P ₁ and P ₂ instead of the intensity ratio between the signals P ₁ and P ₂ . Further, the defect determination unit 50 may determine a defect based on changes in the intensity ratio or intensity difference between the signals P ₁ and P ₂ . In short, the defect determination unit 50 determines whether or not there is a defect or a sign of a defect in the optical fiber 30 based on the relative ratio of the intensities of the first and second partial lights L _D1 and L _D2 , or Defects or signs of defects are determined based on changes in relative ratios or differences in intensities of the first and second partial lights L _D1 and L _D2 .

_In addition, when dirt or the like adheres to the incident end 32 or the exit end 34 of the optical fiber 30, the intensity _ratio r1 of the signals P1 and P2 does not become zero, but the defect determination unit ₅₀ determines that the signals _P1 and P ₂ intensity ratio r ₁ and an appropriate threshold value Th ₁ , the processing laser beam _LP is applied to dirt or the like, and the incident end 32 or the exit end 34 of the optical fiber 30 is excessively heated. It can be appropriately determined as a state. Unlike the background art described above, the failure detection device 1 according to the present disclosure does not detect disconnection of a coated wire separate from the optical fiber 30, but detects laser light transmitted to the optical fiber 30 itself. do. In addition, the processing laser has a wide wavelength band, and the output intensity tends to be unstable due to the operating state or usage time of the processing laser light source. The failure detection device 1 uses detection laser light _LD instead of such a processing laser. Therefore, defects such as disconnection of the optical fiber 30 can be detected or determined with higher reliability.

Also, the ratio of the light intensity of the signal _{P 1} indicating the light intensity of the detection laser light LD incident on the optical fiber 30 and the signal _{P 2} indicating the light intensity of the stable detection laser light LD emitted from the optical fiber , differences, or changes in relative values, defects such as disconnection of the optical fiber 30 can be detected with high reliability.

When the defect determination unit 50 determines that the optical fiber 30 is disconnected or has a defect, the system control unit 60 controls the processing laser light source 10 to immediately stop emitting the high _- power processing laser light LP. By doing so, it is possible to prevent damage to peripheral devices and the like due to the processing laser light LP _leaked from the optical fiber 30 .

[Embodiment 2]
A second embodiment of the failure detection device 2 according to the present disclosure will be described with reference to FIG. FIG. 2 is a block diagram showing a schematic configuration of the failure detection device 2 according to the present disclosure. The failure detection device 2 according to the second embodiment roughly includes a third photodetector 28 that detects the second partial light _LD2 reciprocating through the optical fiber 30 instead of the second photodetector 26. Except for this point, the configuration is the same as that of the first embodiment, so the description of overlapping points will be omitted. A third photodetector 28 is housed in the first housing chamber 16 .

As in the first embodiment, the failure detection device 2 according to the second embodiment generally includes a processing laser light source 10, a detection laser light source 20, a half mirror 22 (spectroscope), an optical fiber 30, and a first It includes a photodetector 24 (photodetector) and a failure determination section 50 (determination section). These configurations and functions are the same as those of the first embodiment.

The failure detection device 2 according to the second embodiment includes a diffraction grating plate 42 (also referred to as a grating or a reflector) arranged perpendicular to the optical axis of the optical fiber 30, shown on the right side of the collimation lens 38 shown in FIG. ). The diffraction grating plate 42 shown in FIG. 2 substantially completely transmits light in a wavelength band equivalent to that of the processing laser light _LP , and transmits light in a wavelength band equivalent to the second _{partial light LD2 of} the detection laser light LD. The light is substantially totally reflected toward the output end 34 of the optical fiber 30 . 2, the diffraction grating plate 42 transmits a certain portion of the second _{partial light LD2 of} the detection laser light LD and emits the rest through the optical fiber 30. It may be reflective towards the edge 34 . At this time, the relative intensity ratio between the light transmitted through the diffraction grating plate 42 of the second partial light _LD2 and the reflected light reflected by the diffraction grating plate 42 is constant.

Further, the second partial light _LD2 of the detection laser light LD emitted from the incident end 32 of the optical fiber 30 is partly reflected by the surface _S2 of the _half mirror 22 (spectroscope) facing upper right in the figure. and the remainder is transmitted. However, in FIG. 2, the straight arrow indicating the transmitted light that is transmitted through the half mirror 22 in the second partial light _LD2 is omitted. That is, the second partial light L _D2 of the detection laser light L _D travels back and forth through the optical fiber 30, and part of the light (the third partial light L _D3 ) is reflected by the surface S ₂ of the half mirror 22. , impinge on the third photodetector 28 .

The third _{photodetector 28 receives the third partial light LD3 of} the detection laser light LD and measures its light intensity. Also, the third photodetector 28 supplies a signal P3 indicating the measured light intensity of the _third partial light _LD3 to the malfunction determination section 50 .

The defect determination unit 50 according to the second embodiment compares the signals P ₁ and P ₃ indicating the light intensity supplied from the first and third photodetectors 24 and 28, and determines whether the optical fiber 30 has a disconnection or the like. Determine whether or not there is a problem. For example, when the intensity ratio (r ₂ =P ₃ /P ₁ ) of the signals P ₁ and P ₃ is smaller than the threshold value Th ₂ (r ₂ <Th ₂ ), the defect determination unit 50 determines that the optical fiber 30 has a defect. You may When the optical fiber 30 is broken, typically the _third partial light L _D3 of the detection laser light L _D is not emitted from the incident end 32 of the optical fiber 30, and the intensity of the signal P3 is approximately is zero and the intensity ratio _r2 is also zero. At this time, the defect determination unit 50 can determine that the optical fiber 30 has been disconnected.

In addition, when dirt or the like adheres to the incident end 32 or the exit end 34 of the optical fiber ₃₀ , the intensity _{ratio r2} of the signals P1 and _P3 does not become zero. By comparing the intensity ratio r2 of _{No. 3} with an appropriate threshold value _Th2 , it is possible to determine whether the incident end 32 or the exit end 34 of the optical fiber 30 is excessively heated due to the processing laser beam _LP being irradiated onto dirt or the like. It can be appropriately determined as a state. As described above, the failure detection device 2 according to the present _disclosure uses the detection laser light LD, which is a stable detection laser light transmitted to the optical fiber 30 itself, to prevent defects such as disconnection of the optical fiber 30. It can be detected or determined with higher reliability.

_A signal _{P 1} indicating the light intensity of the detection laser light LD incident on the optical fiber 30, and the light intensity of the detection laser light LD transmitted back and forth between the incident end and the exit end of the optical fiber A defect such as disconnection of the optical fiber 30 can be detected with high reliability based on the ratio, difference, or change in relative value of the respective light intensities of the signal _P3 indicating .

In addition, in the second embodiment, unlike the first embodiment, both the first and third photodetectors 24 and 28 can be arranged adjacent to the malfunction determination section 50. FIG. Specifically, both the first and third photodetectors 24 and 28 are housed in the first housing chamber 16 . The defect determination unit 50 is also accommodated in the first accommodation chamber 16 . In other words, the third photodetector 28 according to the second embodiment can be arranged closer to the failure determining section 50 than the second photodetector 26 according to the first embodiment. Therefore, the electrical wiring distance for transmitting the signal P3 from the _third photodetector 28 to the fault determination section 50 can be shortened, and the configuration of the failure detection device 2 can be simplified.

When the defect determining unit 50 determines that the optical fiber 30 is disconnected or defective in this way, the system control unit 60 controls the processing laser light source to quickly stop emitting the high _- power processing laser light LP. By controlling 10, it is possible to prevent damage to peripheral devices and the like caused by the processing laser light LP _leaked from the optical fiber 30. FIG.

[Embodiment 3]
A third embodiment of the failure detection device 3 according to the present disclosure will be described with reference to FIG. FIG. 3 is a block diagram showing a schematic configuration of the fault detection device 3 according to the present disclosure. The failure detection device 3 according to the third embodiment is similar to the embodiment except that it includes the third photodetector 28 of the second embodiment in addition to the second photodetector 26 of the first embodiment. Since it has the same configuration as that of form 1, the description of overlapping points will be omitted.

The failure detection device 3 according to Embodiment 3, as in Embodiment 1, generally includes a processing laser light source 10, a detection laser light source 20, a half mirror 22 (spectroscope), an optical fiber 30, and a first It includes a photodetector 24 (photodetector) and a failure determination section 50 (determination section). These configurations and functions are the same as those of the first embodiment.

The failure detection device 3 according to the third embodiment includes a diffraction grating plate 42 (also known as a grating or transmission/reflection section) arranged perpendicular to the optical axis of the optical fiber 30, shown on the right side of the collimation lens 38 shown in FIG. ). The diffraction grating plate 42 of FIG. 3 transmits a part of the second partial light L _D2 of the detection laser light L _D (transmitted light L _D2T ) at a constant ratio, and transmits the rest (reflected light L _D2R ) to the optical fiber. The light is reflected toward the output end 34 of 30 .

The transmitted light _LD2T that has passed through the diffraction grating plate 42 of FIG. 3 enters the second photodetector 26 via the beam splitter 40 as in the first embodiment. Further, the reflected light _LD2R reflected by the diffraction grating plate 42 of FIG. 3 is transmitted to the optical fiber 30 again, and is reflected by the surface S2 of the half mirror 22 (spectroscope) facing upper right in the drawing, as in the _second embodiment. It is reflected and strikes the third photodetector 28 .

The second photodetector 26 for receiving the detection laser light on the output end 34 side of the optical fiber 30 and the third photodetector 28 for receiving the detection laser light on the input end 32 of the optical fiber 30 are the same as those in the first embodiment. and 2, the transmitted light L _D2T and the reflected light L _D2R of the second partial light L _D2 of the detection laser light L _D are received, the light intensities thereof are measured, and signals P ₂ and P 2 indicating the light intensities are obtained. _P3 is supplied to the failure determination unit 50 .

The failure determination unit 50 according to the third embodiment compares the signals P ₁ , P ₂ , P ₃ indicating the light intensities supplied from the first, second and third photodetectors 24, 26, 28. , to determine whether or not the optical fiber 30 has a problem such as disconnection. For example, when the intensity ratios of the signals P ₁ , P ₂ and P ₃ (r ₁ =P ₂ /P ₁ and r ₂ =P ₃ /P ₁ ) are smaller than the thresholds Th ₁ and Th ₂ ( r ₁ <Th ₁ , r ₂ <Th ₂ ), it may be determined that the optical fiber 30 has a problem. When the optical fiber 30 is broken, typically the light intensity of the transmitted light _LD2T and the reflected light _LD2R of the second partial light _LD2 is almost zero, and the intensity ratio r ₁ and r ₂ is also is zero. At this time, the defect determination unit 50 can determine that the optical fiber 30 has been disconnected.

Further, when dirt or the like adheres to the incident end 32 or the exit end 34 of the optical fiber ₃₀ , the intensity _{ratio r1} , _r2 of the signals P1, P2, _P3 does not become zero, but the fault determination unit 50 , signals P ₁ , P ₂ , P ₃ , and the intensity ratios r ₁ , r ₂ of the signals P 1 , P 2 , _P 3 are compared with appropriate threshold values Th ₁ , Th ₂ . Excessive heat generation at the entrance end 32 or the exit end 34 of the laser can be appropriately determined as a defective state. As described above, the failure detection device 3 according to the present _disclosure uses the detection laser light LD, which is a stable detection laser light transmitted to the optical fiber 30 itself, to prevent defects such as disconnection of the optical fiber 30. It can be detected or determined with higher reliability.

Also, a signal _{P 1} indicating the light intensity of the detection laser light LD incident on the optical fiber 30, a signal _{P 2} indicating the light intensity of the stable detection laser light LD emitted from the optical fiber, and an input signal of the optical fiber of the optical fiber ₃₀ based on the ratio, difference, or change in relative value of the respective light intensities of the signal _P3 indicating the light intensity of the detection laser light LD transmitted back and forth between the end and the output end. Defects such as disconnection can be detected with high reliability.

Further, since the failure detection device 3 according to the third embodiment includes the third photodetector 28 of the second embodiment in addition to the second photodetector 26 of the first embodiment, Whether or not the fiber 30 is broken can be determined more reliably.

When the defect determination unit 50 determines that the optical fiber 30 is disconnected or the like in this way, the system control unit 60 controls the processing laser light source 10 to immediately stop emitting the high _- output processing laser beam LP, and It is possible to prevent the peripheral devices from being damaged by the light _LP .

INDUSTRIAL APPLICABILITY The present disclosure can be used for a failure detection device and failure detection method for an optical fiber that transmits high-power processing laser light.

1, 2, 3 Optical fiber failure detection device 10 Processing laser light source 12 Half mirror S ₁ , S ₂ Half mirror surface 20 Detection laser light source 22 Half mirror 24 First photodetector 26 Second photodetector 28 Second 3 Photodetector 30 Optical fiber 32 Incident end 34 Output end 36 Condensing lens 38 Collimation lens 40 Beam splitter 42 Diffraction grating plate 50 Defect judging section (judging section)
60 System control unit _LP Processing laser beam LD Detection laser beam _LD1 First partial beam _LD2 Second partial beam _LD3 Third partial beam _{LD2R Reflected} beam of second partial beam _LD2T Second beam Transmitted light of partial light

Claims (7)

a processing laser light source that emits processing laser light;
a detection laser light source that emits detection laser light;
a spectroscope for splitting the detection laser beam into first and second partial beams;
a first light receiver for measuring the intensity of the first partial light of the detection laser light;
an optical fiber that transmits the second partial light of the detection laser light and the processing laser light from an input end to an output end ;
a reflecting/transmitting part that partially reflects the second partial light that has been transmitted through the optical fiber and emitted from the output end of the optical fiber toward the output end of the optical fiber and partially transmits the second partial light; ,
a second light receiver for measuring the intensity of the transmitted light of the second partial light transmitted through the reflection transmission part;
A third measuring the intensity of the reflected light of the second partial light reflected by the reflecting/transmitting part toward the output end of the optical fiber, transmitted by the optical fiber, and output from the input end of the optical fiber a receiver of
relative ratio of intensities of the first partial light measured by the first light receiver and the transmitted light of the second partial light measured by the second light receiver; The optical fiber is defective based on the relative ratio of the intensity of the first partial light measured at the receiver and the reflected light of the second partial light measured at the third receiver. and a determination unit for determining whether or not. The second partial light of the detection laser light has a smaller loss of light intensity during transmission through the optical fiber than the processing laser light.
The failure detection device according to claim 1. The detection laser light has a shorter peak wavelength, a smaller half width, and a lower output intensity than the processing laser light.
3. The failure detection device according to claim 1 or 2 . The failure detection device according to any one of claims 1 to 3 ;
A laser processing system comprising: a control unit that controls the failure detection device and the processing laser light source. emitting a detection laser beam;
a step of emitting a processing laser beam;
splitting the detection laser beam into first and second partial beams;
measuring the intensity of the first partial light of the detection laser light;
a step of transmitting the second partial light of the detection laser light and the processing laser light through an optical fiber from an input end to an output end of the optical fiber ;
a step of partially reflecting the second partial light transmitted by the optical fiber and emitted from the output end of the optical fiber toward the output end of the optical fiber and partially transmitting the second partial light;
measuring the transmitted light intensity of the partially transmitted second partial light;
measuring the intensity of the reflected light of the second partial light that is partially reflected toward the output end of the optical fiber and transmitted by the optical fiber and output from the input end of the optical fiber ;
the measured relative ratio of the intensities of the first partial light and the transmitted light of the second partial light , and the measured intensity of the first partial light and the reflected light of the second partial light ; and determining whether or not the optical fiber has a defect based on the relative ratio of the intensities. 6. The failure detection method according to claim 5 , wherein said second partial light of said detection laser light has a smaller loss of light intensity while being transmitted through said optical fiber than said processing laser light. . The detection laser light has a shorter peak wavelength, a smaller half width, and a lower output intensity than the processing laser light.
The failure detection method according to claim 5 or 6 .

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