JP2018022786A - Damage detection apparatus and method in laser oscillator for laser processing machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately determine a damage of a fiber laser oscillator and perform an appropriate replacement. In a processing machine for performing processing by irradiating a work with laser light from a fiber laser oscillator through a laser processing head, a feeding fiber on the fiber laser oscillator side and a process fiber on the laser processing head side are separated. An outer laser light detection unit for detecting an outer laser light existing outside the effective laser light sent to the laser processing head side is provided in the space inside the beam coupler, and the fiber laser laser oscillator is provided by the outer laser light detection unit. Detect damage in. [Selection diagram]

Description

  The present invention relates to a damage detection apparatus and method for detecting damage of a laser oscillator in a laser processing machine.

  In recent years, fiber laser oscillators have come to be used as laser oscillators because laser processing machines have high average power density and are suitable for thin plate high-speed processing.

  In general, when a workpiece is irradiated with laser light from the process fiber of a fiber laser oscillator, the return light of the laser light from the workpiece is generated, and the return light has damaged components such as the fiber laser oscillator. .

  Then, if the components such as the fiber laser oscillator are severely damaged, the fiber laser oscillator has been replaced in order to hinder the laser light irradiation.

  Therefore, a configuration has been proposed in which a beam coupler is provided that separates a process fiber that is most susceptible to the influence of reflected light from a workpiece and mechanical stress from a feeding fiber on the fiber laser oscillator side.

  Thus, even if the process fiber is damaged, only the process fiber needs to be replaced.

JP 2012-179627 A

  Conventionally, the return light of the laser beam from the workpiece is detected, and when the return light is a predetermined value or more, components such as a laser oscillator have been replaced.

  However, the damaged part of the fiber laser oscillator component was determined accurately and could not be replaced properly.

  The present invention has been made paying attention to the above-described circumstances, and the object of the present invention is to provide a damage detection apparatus and method capable of accurately determining a damaged portion of a fiber laser oscillator and performing an accurate replacement. Is to provide.

The present invention is for solving the above-mentioned problems, and a feature of the present invention is that in the processing machine that performs processing by irradiating a workpiece with a laser beam from a fiber laser oscillator through a laser processing head, the fiber laser A damage detection device for detecting damage in a laser oscillator,
A beam coupler that separates the feeding fiber on the fiber laser oscillator side and the process fiber on the laser processing head side;
An outer laser beam detector for detecting an outer laser beam existing outside the effective laser beam sent to the laser processing head side is provided in the space in the beam coupler.

  More preferably, the outer laser light detector is arranged to detect the outer laser light existing outside the effective laser light at a plurality of positions shifted in angle with respect to the optical axis of the effective laser light. It consists of a plurality of photodiodes.

  More preferably, the outer laser light detection unit is composed of three photodiodes arranged in a fan shape with an angle shifted with respect to the optical axis of the effective laser light.

  More preferably, the beam coupler collimates a laser beam incident from the feeding fiber, a bend mirror that receives and reflects an effective laser beam collimated by the collimation lens, and the bend A condensing lens that inputs incident light reflected by a mirror to the process fiber, and the photodiode is provided in the vicinity of the outside of the collimation lens.

  More preferably, the beam coupler collimates a laser beam incident from the feeding fiber, a bend mirror that receives and reflects an effective laser beam collimated by the collimation lens, and the bend A condenser lens that inputs incident light reflected by a mirror to the process fiber, and the photodiode detects the outer laser light transmitted through the collimation lens.

  More preferably, the photodiode is provided between the collimation lens and the bend mirror in the space in the beam coupler 7.

  More preferably, the beam coupler collimates a laser beam incident from the feeding fiber, a bend mirror that receives and reflects an effective laser beam collimated by the collimation lens, and the bend A condenser lens that inputs incident light reflected by a mirror into the process fiber, and the photodiode detects the outer laser light reflected by the collimation lens.

Another feature of the present invention is a damage detection method for detecting damage in the fiber laser laser oscillator in a processing machine that performs processing by irradiating a workpiece with a laser beam from a fiber laser oscillator via a laser processing head. ,
Detects the outer laser beam that exists outside the effective laser beam sent to the laser processing head side in the space inside the beam coupler that separates the feeding fiber on the fiber laser oscillator side and the process fiber on the laser processing head side. It is to be.

  More preferably, the outer laser beam existing outside the effective laser beam sent to the laser processing head side in the space in the beam coupler is at a plurality of positions shifted in angle with respect to the optical axis of the effective laser beam. It is to be detected.

  According to the present invention, damage of a fiber laser oscillator can be accurately determined and replaced accurately.

It is a schematic block diagram of embodiment of the laser processing apparatus which implemented this invention. It is a schematic block diagram inside the beam coupler 7 shown in FIG. It is a graph which shows intensity distribution of laser beam LB1 from feeding fiber 5. FIG. It is a graph which shows intensity distribution of laser beam LB1 from feeding fiber 5. FIG. It is a graph which shows intensity distribution of the outer side laser beam LB1b from the feeding fiber 5. FIG. FIG. 5 is a schematic internal configuration diagram of a second embodiment of the beam coupler 7 shown in FIG. 1. It is a schematic block diagram inside a beam coupler 7 in the modification of embodiment shown in FIG. It is a graph which shows intensity distribution of the outer side laser beam LB2b from the collimation lens 7a. It is explanatory drawing which shows the change of a light ray when the boundary of an optical fiber core and a clad changes shape by damage etc.

  FIG. 1 is a schematic configuration diagram of an embodiment of a laser processing apparatus embodying the present invention.

  As shown in FIG. 1, the laser processing apparatus 1 has a fiber laser oscillator 3 that irradiates a laser beam, and the laser beam output from the fiber laser oscillator 3 propagates through a feeding fiber 5 and is a beam coupler. 7 is reached.

  The laser light that has passed through the beam coupler 7 propagates through the process fiber 9, and the laser light emitted from the emission end is incident on the laser processing head 11 and is irradiated onto the workpiece W from the laser processing head 11.

  The beam coupler 7 separates the feeding fiber 5 and the process fiber 9 from each other. That is, the laser processing apparatus 1 includes a beam coupler 7 that separates the feeding fiber 5 on the fiber laser laser oscillator 3 side and the process fiber 9 on the laser processing head 11 side.

  Even if the process fiber 9 that is most susceptible to the influence of reflected light from the workpiece W and mechanical stress is damaged due to the separation of the feeding fiber 5 and the process fiber 9, only the process fiber 9 is replaced. As a result, frequent replacement of the fiber laser oscillator 3 is avoided.

  Here, the fiber laser oscillator 3 is a high-density fiber-coupled LD light source, a plurality of laser diodes 3a, a pump combiner 3b that couples seed light from the plurality of laser diodes 3a, and light from the pump combiner 3b. (Pumping fiber) The first fiber Bragg grating 3c guided to 3d, the doped fiber 3d for exciting the bee having the wavelength used for processing with the light from the first fiber Bragg grating 3c, and the light from the doped fiber 3d And a second fiber Bragg grating 3e to be taken out.

  Fiber Bragg Grating (FBG) is an element in which a diffraction grating is written in an optical fiber by utilizing, for example, Ge ion contained in the core of an optical fiber to cause a change in refractive index by ultraviolet irradiation. Therefore, the doped fiber (pumping fiber) 3d is doped with, for example, ytterbium (Yb) to generate pumping light having a wavelength band of approximately 1060-1080 nm. .

  As shown in FIG. 1, the laser processing apparatus 1 has a control unit 15 that receives detection signals from photodiodes 13a, 13b, and 13c (FIG. 2) provided in a beam coupler 7 described later. The control unit 15 that has received the detection signal issues a warning when the divergence angle of the fiber light beam exceeds a predetermined value, or controls the fiber laser oscillator 3 to stop the irradiation of the laser beam on the workpiece. To do.

  FIG. 2 is an internal configuration diagram of the first embodiment of the beam coupler 7 shown in FIG. The beam coupler 7 has a function of monitoring the divergence angle of the laser beam therein.

  As shown in FIG. 2, in the beam coupler 7, the laser beam LB1 emitted from the feeding fiber 5 is collimated by the collimation lens 7a to become an effective laser beam LB2, and is a reflecting surface with respect to the incident effective laser beam LB2. Is reflected by a bend mirror 7b provided with an inclination of approximately 45 degrees, is incident on the condenser lens 7c as incident light LB3, and is input to the process fiber 9.

  The beam coupler 7 detects weak light (outer laser light LB1b) existing outside the effective laser light LB1a sent to the laser processing head 11 side in the laser light LB1 emitted from the feeding fiber 5. For this purpose, an outer laser beam detector 13 made of a photodiode is provided.

  In this embodiment, three outer laser light detectors 13 are arranged in a fan shape in the vicinity of the outer side of the collimation lens 7a in the space in the beam coupler 7 with an angle shifted with respect to the optical axis X of the effective laser light LB1a. It comprises at least three photodiodes 13a, 13b and 13c.

  That is, as shown in FIG. 2, the photodiode 13a is disposed at an angle α1 with respect to the optical axis X of the collimation lens 7a, and the photodiode 13b is disposed at an angle α2 with respect to the optical axis X. The photodiode 13c is disposed at an angle α3 with respect to the optical axis X, and α1 <α2 <α3. The angle α1 at which the photodiode 13a is disposed is larger than the angle with respect to the optical axis X of the outermost laser beam among the effective laser beams LB1a sent to the laser processing head 11 side.

  Note that the distances from the end of the feeding fiber 5 to the photodiodes 13a, 13b, and 13c are the same.

  Thus, each of the photodiodes 13a, 13b, and 13c detects the outer laser beam LB1b at a position shifted in angle with respect to the optical axis X of the collimation lens 7a. In this embodiment, three photodiodes 13a, 13b, and 13c are provided, but three or more photodiodes may be provided.

  By detecting the outer laser beam LB1b in the space in the beam coupler 7 by the photodiodes 13a, 13b, and 13c, the spread angle of the laser beam LB1 incident from the feeding fiber 5 can be detected and monitored. Damage to the fiber on the fiber laser oscillator 3 side can be determined based on the detected divergence angle.

  Hereinafter, damage determination of the fiber on the fiber laser oscillator 3 side by detection of the outer laser beam LB1b will be described.

  If even a slight damage (damage due to cracking or bending) occurs in the fiber (for example, feeding fiber 5) inside the fiber laser oscillator 3, the structure of the fiber changes, and the waveguide mode increases accordingly. However, the increase of the waveguide mode increases the divergence angle of the fiber light beam emitted from the fiber end. Here, when light is totally reflected and transmitted through the optical fiber, it resonates in the lateral direction and the reflection angle is limited, resulting in a discrete angle, and the light intensity distribution in the optical fiber has a specific shape. A collection of light rays traveling while maintaining such a light intensity distribution is called a waveguide mode. When the inside of the fiber is damaged, the light intensity distribution changes, and the divergence angle of the fiber light beam changes, so that the divergence angle can be observed.

  For example, as shown in FIG. 9, when the boundary between the core 21 and the clad 23 is deformed due to breakage or the like, the light beam having the divergence angle of θ1 changes to θ3, and of course θ2 is deformed in the opposite direction. However, since the boundary between the core and the clad is disturbed from a flat state, it is possible to detect that the fiber is broken by capturing the change in the shape of θ2 in the direction 25 shown in the figure below. Is.

  In FIG. 9, it is assumed that the shape is changed at the boundary between the clad 23 and the core 21 due to the stress generated in the optical fiber, and the light reflected on the changed portion has a spread angle increased by 2 × θ2. Therefore, it is considered that the intensity distribution spreads as a whole.

  In the following description, the feeding fiber 5 is described as a fiber that is damaged. However, other fibers inside the fiber laser oscillator 3 such as the doped fiber 3d may be damaged.

  If the fiber light beam is left in a state in which the divergence angle is large, the divergence angle of the fiber light beam is further increased and the fiber laser oscillator 3 is damaged.

  FIG. 3 is a graph showing the intensity distribution of the laser beam LB1 from the feeding fiber 5 without damage.

  As shown in FIG. 3, the intensity distribution of the laser beam LB1 from the feeding fiber 5 becomes the strongest peak P at the center position of the feeding fiber 5, and the intensity decreases toward both sides of the peak P.

  In FIG. 3, the range indicated by the dotted line indicates the intensity of the effective laser beam LB1a collimated by the collimation lens 7a, and the range indicated by the dotted line indicates the intensity of the outer laser beam LB1b existing outside the effective laser beam LB1a. Indicates. The intensity of the laser beam LB1 gradually decreases toward the outside of the peak P, and the decrease (inclination) in intensity is moderate outside the range indicated by the dotted line.

  In addition, the horizontal axis of FIG. 3 shows an angular position. The range of the dotted line is, for example, preferably 7.5 ° to 8.5 °, more preferably 7.5 ° to 9.5 °, and further preferably 7.5 ° to 10.5 °. The reason why the dotted line range is selected in this way is that a change from a minute change in the divergence angle to an apparent change in the divergence angle due to fiber breakage can be regarded as a transition of the aging or divergence state.

  The photodiodes 13a, 13b, and 13c detect portions where the decrease (gradient) in the intensity outside the range indicated by the dotted line is gentle.

  In FIG. 3, the intensity of the outer laser beam LB1b detected by the photodiodes 13a, 13b, and 13c is indicated by white circles.

  FIG. 4 is a graph showing the intensity distribution 103 of the laser beam LB1 from the feeding fiber 5 having damage. In FIG. 4, as indicated by the solid line, the intensity distribution and the divergence angle are larger than the laser light from the fiber without damage.

  FIG. 5 is a graph showing the intensity distribution 103 of the outer laser beam LB1b from the damaged feeding fiber 5. FIG. As shown in FIG. 5, the intensity 103 of the outer laser light from the damaged fiber is higher than the intensity 101 of the outer laser light from the undamaged fiber, and the inclination is small.

  Therefore, if the intensity of the outer laser beam LB1b detected by the photodiodes 13a, 13b, and 13c is detected, the outer sides detected by the photodiodes 13a, 13b, and 13c in a state where the fiber is not damaged, as shown by white circles in FIG. The intensity distribution (solid line) of the outer laser beam LB1b detected by the photodiodes 13a, 13b, and 13c in the state where the divergence angle is larger than the intensity distribution (one-dot chain line) of the laser beam LB1b increases and the inclination increases. Will decrease.

  Detection signals detected by the photodiodes 13a, 13b, and 13c are sent to the control unit 15.

  Therefore, first, the control unit 15 detects and stores the intensity distribution 101 of the outer laser beam LB1b detected by the photodiodes 13a, 13b, and 13c when the fiber is not damaged. The newly detected intensity distribution 103 is compared. If the intensity distribution 103 increases in intensity and decreases in inclination as compared with the intensity distribution 101, it is determined that the fiber light beam divergence angle has increased.

  If the slope of the intensity distribution 103 decreases by a predetermined amount or more than the slope of the intensity distribution 101, it is determined that the fiber on the fiber laser oscillator 3 side is damaged.

  When the control unit 15 determines that the fiber on the fiber laser oscillator 3 side is damaged, the control unit 15 controls the fiber laser oscillator 3 so as to issue a warning to the display unit or stop the irradiation of the laser beam on the workpiece. To do.

  In the case of the present embodiment, it is determined that the fiber is damaged when the slope of the intensity distribution changes, for example, by 10%.

  Therefore, according to the first embodiment, it can be reliably determined that the fiber on the fiber laser oscillator 3 side is damaged.

  Then, after it is determined that the fiber on the fiber laser oscillator 3 side is damaged and the operation is stopped, the fiber laser oscillator 3 is exchanged.

  Next, a second embodiment of the present invention will be described.

  FIG. 6 is an internal schematic configuration diagram of the second embodiment of the beam coupler 7 shown in FIG.

  As shown in FIG. 6, in the second embodiment, the weak light existing outside the effective laser beam LB2a transmitted through the collimation lens 7a in the laser beam LB1 incident from the feeding fiber 5 in the beam coupler 7. An outer laser beam detector 17 made of a photodiode for detecting (outer laser beam LB2b) is provided.

  Other configurations in the beam coupler 7 are the same as those in the first embodiment. That is, the laser light LB1 incident from the feeding fiber 5 is collimated by the collimation lens 7a to become effective laser light LB2, and the reflection surface is provided with an inclination of approximately 45 degrees with respect to the incident effective laser light LB2. The light is reflected by the bend mirror 7b, is incident on the condenser lens 7c as incident light LB3, and is input to the process fiber 9.

  In this embodiment, three outer laser light detectors 17 are arranged at a shifted angle with respect to the optical axis X of the effective laser light LB2 between the collimation lens 7a and the bend mirror 7b in the space in the beam coupler 7. The photodiodes 17a, 17b and 17c are arranged in a fan shape.

  That is, as shown in FIG. 6, the photodiode 17a is disposed at an angle α6 with respect to the optical axis X of the effective laser beam LB2, and the photodiode 17b is disposed at an angle α5 with respect to the optical axis X. The photodiode 17c is arranged at an angle α4 with respect to the optical axis X, and α4 <α5 <α6. Note that the distances from the end face of the collimation lens 7a to the photodiodes 17a, 17b, and 17c are the same.

  As described above, each of the photodiodes 17a, 17b, and 17c detects the outer laser beam LB2b at a position shifted from the optical axis X of the effective laser beam LB2. In this embodiment, three photodiodes 17a, 17b, and 17c are provided, but three or more photodiodes may be provided.

  By detecting the outer laser beam LB2b in the space in the beam coupler 7 with the photodiodes 17a, 17b, and 17c, the spread angle of the laser beam LB1 incident from the feeding fiber 5 and the breakage of the collimation lens 7a are detected. Can be monitored.

  Hereinafter, the fiber damage determination on the fiber laser oscillator 3 side and the damage determination of the collimation lens 7a based on the detection of the outer laser beam LB2b will be described.

  If even a slight damage (due to cracking or bending) occurs in the fiber inside the fiber laser oscillator 3, the structure of the fiber changes, thereby changing the waveguide mode to increase. The divergence angle of the fiber light beam emitted from the fiber end is increased.

  If the fiber light beam is left in a state in which the divergence angle is large, the divergence angle of the fiber light beam is further increased and the fiber laser oscillator 3 is damaged.

  Further, if the collimation lens 7a is damaged, the fiber light is diffused due to the damage, the intensity of the laser light is increased, and the condensing lens is damaged.

  FIG. 8 is a graph showing the intensity distribution of the outer laser beam LB2b from the collimation lens 7a.

  As shown in FIG. 8, the intensity distribution 203 of the outer laser light LB2b from the damaged fiber has a larger intensity and a smaller inclination than the intensity distribution 201 of the outer laser light from the undamaged fiber. On the other hand, the intensity distribution 205 of the outer laser beam LB2b from the damaged collimation lens 7a has the same inclination and higher intensity than the intensity distribution 201 of the outer laser beam from the collimation lens 7a without damage.

  In FIG. 8, the intensity distribution of the outer laser light from the fiber having no damage is indicated by a one-dot chain line, the intensity distribution of the laser light from the fiber having damage is indicated by a solid line, and the intensity of the laser light from the collimation lens 7a having damage The distribution is indicated by a two-dot chain line.

  Therefore, if the intensity of the outer laser beam LB2b detected by the photodiodes 17a, 17b, and 17c is detected, as shown in FIG. 8, the outer laser beam detected by the photodiodes 17a, 17b, and 17c in a state where the fiber is not damaged. Compared to the intensity distribution 201 of LB2b, the intensity distribution 203 of the outer laser beam LB2b detected by the photodiodes 17a, 17b, and 17c in a state where the fiber is damaged increases in intensity and decreases in inclination.

  Further, as shown in FIG. 8, the photodiodes 17a, 17b in the state where the collimation lens 7a is damaged are compared with the intensity distribution 201 of the outer laser light LB2b detected by the photodiodes 17a, 17b, 17c in a state where the fiber is not damaged. , 17c, the intensity distribution 205 of the outer laser beam LB2b increases in intensity with the inclination unchanged.

  Detection signals detected by the photodiodes 17a, 17b, and 17c are sent to the control unit 15.

  Therefore, first, the control unit 15 detects and stores the intensity distribution 201 of the outer laser beam LB2b detected by the photodiodes 17a, 17b, and 17c when the fiber is not damaged. The newly detected intensity distribution 203 is compared. If the intensity distribution 203 increases in intensity and decreases in inclination compared to the intensity distribution 201, the fiber laser beam divergence angle exceeds a predetermined value and the fiber laser oscillator 3 Determine that the side fiber is damaged.

  Further, the control unit 15 compares the intensity distribution 201 of the outer laser beam LB2b detected by the photodiodes 17a, 17b, and 17c when the fiber is not damaged with the newly detected intensity distribution 205, and the intensity distribution 205 is If the intensity increases without changing the inclination as compared with the intensity distribution 201, it is determined that the collimation lens 7a is damaged.

  When the control unit 15 determines that the fiber on the fiber laser oscillator 3 side or the collimation lens 7a is damaged, the control unit 15 issues a warning or controls the fiber laser oscillator 3 to stop the irradiation of the laser beam on the workpiece. To do.

  When it is determined that the fiber on the fiber laser oscillator 3 side is damaged, the fiber laser oscillator 3 is replaced.

  When it is determined that the collimation lens 7a is damaged, the beam coupler 7 is exchanged.

  Therefore, according to the second embodiment, it is possible to reliably determine that the fiber on the fiber laser oscillator 3 side is damaged, and it is also possible to determine damage to the collimation lens 7a in the beam coupler 7.

  Next, a modification of the first embodiment shown in FIG. 2 will be described.

  FIG. 7 is a schematic configuration diagram of the inside of the beam coupler 7 in the modification of the first embodiment shown in FIG.

  In the first embodiment shown in FIG. 2, the outer laser beam LB1b existing outside the effective laser beam LB1a picked up by the collimation lens 7a is directly detected. However, in this modification, the reflection is performed by the collimation lens 7a. The outer laser beam LB1b thus detected is detected by the outer laser beam detector 19.

  Therefore, as shown in FIG. 7, the photodiodes 19a, 17b, and 17c of the outer laser light detection unit 19 are angled with respect to the optical axis X of the effective laser light LB1a in the reflection direction of the outer laser light LB1b by the collimation lens 7a. They are arranged in a fan shape, with three in a row.

  As described above, each of the photodiodes 19a, 19b, and 19c detects the outer laser beam LB1b reflected by the collimation lens 7a at a position shifted from the optical axis X of the effective laser beam LB1a. ing. In this embodiment, three photodiodes 19a, 19b, 19c are provided, but three or more photodiodes may be provided.

  By detecting the outer laser beam LB1b in the space in the beam coupler 7 by the photodiodes 19a, 19b, and 19c, the spread angle and intensity of the laser beam LB1 incident from the feeding fiber 5 can be detected and monitored. The damage of the fiber or lens on the fiber laser oscillator 3 side can be determined from the detected divergence angle and intensity.

  The present invention is not limited to the embodiments of the invention described above, and can be implemented in other modes by making appropriate modifications.

  For example, in the space in the beam coupler 7, the photodiodes 13a, 13b, 13c of the first embodiment and the photodiodes 17a, 17b, 17c of the second embodiment may be arranged together.

DESCRIPTION OF SYMBOLS 1 Laser processing apparatus 3 Fiber laser oscillator 5 Feeding fiber 7 Beam coupler 7a Collimation lens 9 Process fiber 11 Laser processing head 13, 17, 19 Outer laser beam detection part 15 Control part

Claims (9)

In a processing machine that performs processing by irradiating a workpiece with a laser beam from a fiber laser oscillator through a laser processing head, a damage detection device that detects damage in the fiber laser laser oscillator,
A beam coupler that separates the feeding fiber on the fiber laser oscillator side and the process fiber on the laser processing head side;
A damage detection apparatus comprising an outer laser light detection unit for detecting an outer laser beam existing outside an effective laser beam sent to the laser processing head side in a space in the beam coupler.   A plurality of photodiodes arranged so that the outer laser beam detector detects the outer laser beam existing outside the effective laser beam at a plurality of positions shifted from the optical axis of the effective laser beam. The damage detection device according to claim 1, comprising:   3. The damage detection apparatus according to claim 2, wherein the outer laser light detection unit is composed of three photodiodes arranged in a fan shape with an angle shifted with respect to the optical axis of the effective laser light.   The beam coupler is reflected by the collimation lens that collimates the laser light incident from the feeding fiber, the bend mirror that reflects the effective laser light collimated by the collimation lens, and the bend mirror. 4. The damage detection according to claim 2, further comprising: a condensing lens that inputs incident light to the process fiber, wherein the photodiode is provided near the outside of the collimation lens. apparatus.   The beam coupler is reflected by the collimation lens that collimates the laser light incident from the feeding fiber, the bend mirror that reflects the effective laser light collimated by the collimation lens, and the bend mirror. The condenser lens for inputting the incident light to the process fiber, and the photodiode detects the outer laser light transmitted through the collimation lens. The damage detection apparatus described.   The damage detection apparatus according to claim 5, wherein the photodiode is provided between the collimation lens and the bend mirror in a space in the beam coupler 7.   The beam coupler is reflected by the collimation lens that collimates the laser light incident from the feeding fiber, the bend mirror that reflects the effective laser light collimated by the collimation lens, and the bend mirror. The condenser lens for inputting the incident light to the process fiber, and the photodiode detects the outer laser light reflected from the collimation lens. The damage detection apparatus described. In a processing machine that performs processing by irradiating a workpiece with a laser beam from a fiber laser oscillator through a laser processing head, a damage detection method for detecting damage in the fiber laser laser oscillator,
Detects the outer laser beam that exists outside the effective laser beam sent to the laser processing head side in the space inside the beam coupler that separates the feeding fiber on the fiber laser oscillator side and the process fiber on the laser processing head side. A damage detection method characterized by:   Outside laser light existing outside the effective laser beam sent to the laser processing head side in the space in the beam coupler is detected at a plurality of positions shifted in angle with respect to the optical axis of the effective laser beam. The damage detection method according to claim 8.

Images