JP2019155446A - Laser beam machining device and laser beam oscillation control method - Google Patents

Abstract

To provide a laser beam machining device capable of evaluating quality of emitted laser beams.SOLUTION: A laser beam machining device 100 includes: a plurality of laser modules 11; a beam coupling coupler 12 coupling the plurality of laser beams and emitting the beams as a coupled laser beam LB; an optical unit 20 condensing the coupled laser beam LB and guiding the beam to a transmission fiber 40; a laser beam emission head 30 mounted on the transmission fiber 40; and a control part 50 controlling operation of the laser modules 11 and the optical unit 20. The optical unit 20 includes: a partial reflection mirror 22 transmitting a part of the coupled laser beam LB, on the other hand, reflecting a remaining part toward a beam camera 24 generating image signals; and a shutter 23. The control part 50 is further provided with a calculation part 52 determining quality of the coupled laser beam LB on the basis of the image signals.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a laser processing apparatus and a laser oscillation control method.

  In recent years, development of a laser processing apparatus using a DDL oscillator has been accelerated with an increase in output of a direct diode laser (hereinafter referred to as DDL) oscillator. The DDL oscillator can obtain a high output exceeding several kW by combining laser beams emitted from a plurality of laser modules. The laser beam emitted from the beam combiner is guided to a processing head installed at an arbitrary point via a transmission fiber. At this time, the laser beam emitted from the beam combiner is collected by the condenser lens up to a spot diameter that can be accommodated in the core of the transmission fiber and then incident on the transmission fiber (for example, see Patent Document 1).

International Publication No. 2016/152404

  By the way, the DDL oscillator accompanies the temperature rise of each laser module and the optical system during laser oscillation. Due to this temperature rise, a wavelength shift of the laser beam emitted from the laser module, a change in the emission angle, a change in the polarization state, or the like may occur. Further, each optical element in the optical system can change its optical characteristics such as a condensing characteristic due to a temperature rise. Further, as the output of the DDL oscillator becomes higher, the number of laser modules increases, and accordingly, the number of optical elements to be used increases. Therefore, the influence of the individual temperature rise on the optical output characteristics of the DDL oscillator is increased.

  For this reason, normally, in a DDL oscillator, the internal temperature is stable, in other words, the laser oscillation is performed for a predetermined time or more, and the optical system is thermally saturated or close to it. The angle is adjusted. This stabilizes the quality of the emitted laser beam.

  Conventionally, however, it has been difficult to detect whether the optical system is thermally saturated. For example, even when measuring the temperature in the DDL oscillator, it is necessary to correlate the temperature with the thermal saturation of the optical system. In addition, since such correlation changes depending on the specifications of the DDL oscillator, individual differences, and the like, it is necessary to make an individual determination based on experience, resulting in a reduction in work efficiency. In particular, when laser oscillation is started from a state where laser oscillation of the DDL oscillator is stopped for a long time, it is possible to simply determine whether the beam quality required for the desired processing is obtained only by the temperature in the DDL oscillator. was difficult.

  On the other hand, if the quality of the laser beam is unstable, the spot size and spot position at the incident portion of the transmission fiber will also change. As a result, leakage light to the cladding of the transmission fiber increases, which may lead to loss of laser beam output and possibly damage to the transmission fiber. In particular, when a plurality of laser beams are combined and emitted, the combined laser beam (hereinafter simply referred to as a combined laser beam) is in a state of being more spatially spread than a single laser beam. There was a possibility that the above problem would become more remarkable.

  The present invention has been made in view of the above points, and an object thereof is to provide a laser processing apparatus capable of evaluating the quality of an emitted laser beam by monitoring the shape of the laser beam.

  In order to achieve the above object, a laser processing apparatus according to the present invention combines a plurality of laser modules each emitting a laser beam and a plurality of laser beams emitted from the plurality of laser modules to emit a combined laser beam. A beam combiner, an optical unit for condensing the combined laser beam emitted from the beam combiner so as to have a predetermined beam diameter and guiding it to the transmission fiber, and a laser attached to the output end of the transmission fiber A laser processing apparatus comprising at least a beam emitting head and a control unit that controls operations of the plurality of laser modules and the optical unit, wherein the optical unit transmits a part of the combined laser beam. A partial reflection mirror that reflects the remainder in a direction different from the traveling direction of the combined laser beam, and the partial reflection A beam monitor that receives the remainder of the combined laser beam reflected by the mirror and generates an image signal, and is movable between a predetermined position on the optical path of the combined laser beam and a predetermined position outside the optical path. The control unit further includes a beam quality determination unit that determines the quality of the combined laser beam based on the image signal generated by the beam monitor.

  According to this configuration, the beam quality of the combined laser beam emitted from a laser oscillator including a plurality of laser modules can be constantly monitored, and laser processing can be performed stably.

  A laser oscillation control method according to the present invention is a laser oscillation control method in the laser processing apparatus described above, comprising: a laser oscillation start step for starting laser oscillation of the plurality of laser modules; and a remaining portion of the combined laser beam. A beam observation step of obtaining an image signal by observing with the beam monitor; and a beam quality determination step of determining the quality of the combined laser beam based on image information obtained from the image signal. To do.

  According to this method, laser processing can be stably performed by performing laser oscillation control based on the determination result in the beam quality determination step.

  According to the laser processing apparatus and the laser oscillation control method according to the present invention, laser processing can be performed stably.

It is a schematic diagram which shows the structure of the laser processing apparatus which concerns on embodiment of this invention. It is the cross-sectional schematic diagram which looked at the internal structure of the beam combiner and the optical unit from one direction. It is the cross-sectional schematic diagram which looked at the internal structure of the beam combiner and the optical unit from another direction. It is a flowchart which shows a laser oscillation control procedure. It is a figure which shows the time change of the beam quality of the laser oscillator from a laser oscillation start. It is an example which shows the relationship between the spot shape of a laser beam, and its quality determination result. It is another example which shows the relationship between the spot shape of a laser beam, and its quality determination result.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or its application.

(Embodiment)
[Configuration of laser processing equipment]
FIG. 1 shows a schematic diagram of a configuration of a laser processing apparatus according to the present embodiment. FIG. 2 is a schematic cross-sectional view of the internal configuration of the beam combiner and the optical unit viewed from one direction, and FIG. 3 is a schematic cross-sectional view of the internal configuration viewed from another direction. Note that FIG. 2 shows only a portion where a laser beam LB1 travels among a plurality of laser beams described later. In the following description, the traveling direction of the laser beam incident on the beam combiner from the laser oscillator in FIG. 2 is the X direction, the direction in which the laser beam LB1 reflected by the mirror M1 is directed to the mirror M2 is the Z direction, and the X direction. The direction perpendicular to the Z direction may be referred to as the Y direction.

  The laser processing apparatus 100 includes a laser oscillator 10, a laser beam emitting head 30, a transmission fiber 40, a control unit 50, and a power source 60. The end of the laser oscillator 10 and the transmission fiber 40 where the laser beam is incident (hereinafter simply referred to as the incident end; the end where the laser beam of the transmission fiber 40 is emitted is hereinafter simply referred to as the emission end). Housed in the housing 70.

  The laser oscillator 10 includes a plurality of laser modules 11, a beam combiner 12, and an optical unit 20. The laser module 11 includes a plurality of laser diodes or laser arrays that emit laser beams having different wavelengths, and the laser beam synthesized in the laser module 11 is emitted from each laser module 11. The laser beams emitted from the plurality of laser modules 11 are combined into one combined laser beam by the beam combiner 12. The combined laser beam is condensed by a condenser lens 21 disposed in the optical unit 20, and the beam diameter is reduced by a predetermined magnification and is incident on the transmission fiber 40. With the laser oscillator 10 having such a configuration, a high-power laser processing apparatus 100 having a laser beam output exceeding several kW can be obtained. Further, the laser oscillator 10 is supplied with electric power from a power source 60 described later to perform laser oscillation, and a coupled laser beam is emitted from the emission end of the transmission fiber 40.

  The beam combiner 12 includes a plurality of mirrors including mirrors M1 and M2 and optical parts (not shown), and laser beams emitted from the plurality of laser modules 11 are respectively incident on the light incident part LI1 and other light incident parts ( (Not shown) respectively. Each mirror and the optical component are arranged inside the beam combiner 12 so that the laser beams emitted from the plurality of laser modules 11 are combined and emitted from the laser beam emitting unit LO as a combined laser beam LB. Yes.

  The optical unit 20 includes a condenser lens 21, a partial reflection mirror 22, a shutter 23, a beam camera (hereinafter sometimes referred to as a beam monitor) 24, and a beam damper 25. The condensing lens 21 condenses the combined laser beam LB at the incident end of the transmission fiber 40 so that the beam diameter is smaller than the core diameter of the core 41 described later. The optical unit 20 has a connector (not shown), and an incident end of the transmission fiber 40 is connected to the connector. The partial reflection mirror 22 transmits a part of the combined laser beam LB collected by the condensing lens 21 and reflects the remaining part toward the beam camera 24 located in a direction different from the traveling direction of the combined laser beam LB. It is configured as follows. In the present embodiment, 99.99% of the combined laser beam LB is transmitted through the partial reflection mirror 22, and 0.01% is reflected toward the imaging surface (not shown) of the beam camera 24. The optical characteristics of the reflection mirror 22 are set. However, the present invention is not particularly limited to this, and the reflectance of the partial reflection mirror 22 can be appropriately changed depending on the output of the combined laser beam LB, the durability of the beam camera 24, and the like. However, if the reflectance is too large, the intensity of the laser beam incident on the beam camera 24 becomes too strong, and the imaging surface (not shown) of the beam camera 24 may be burned. With this in mind, it is necessary to set the reflectance of the partial reflection mirror 22.

  Further, the shutter 23 is driven by an actuator (not shown) based on a drive signal from the control unit 50 to be described later, and is arranged on the optical path of the combined laser beam LB or movable so as to be retracted from the optical path. It is configured. The shutter 23 may be moved linearly in a direction intersecting the optical path of the combined laser beam LB, or may be rotated relative to the optical path of the combined laser beam LB. In the former case, the shutter 23 moves at a predetermined angle with respect to the optical path of the combined laser beam LB, and deflects the combined laser beam LB toward the beam damper 25 when the shutter 23 is on the optical path. . In the latter case, the shutter 23 is configured to rotate so as to pass the combined laser beam LB or deflect the combined laser beam LB toward the beam damper 25. The shutter 23 is preferably provided with a material that totally reflects the coupled laser beam LB on the incident surface when the coupled laser beam LB is incident. The entire shutter 23 may be made of the material.

  The beam camera 24 receives the remaining part of the combined laser beam LB reflected by the partial reflection mirror 22 by an imaging surface (not shown) and generates an image signal. As will be described later, this image signal includes image information which is information regarding the remaining beam shape of the coupled laser beam LB and the coupling state between the coupled laser beam LB and the incident end of the transmission fiber 40 (FIGS. 6A and 6B). reference). The image signal may be input to a display unit (not shown) connected to the control unit 50, and the beam shape and the coupling state with the transmission fiber 40 may be displayed on the display unit.

  When the shutter 23 is disposed on the optical path of the combined laser beam LB, the beam damper 25 receives the combined laser beam LB deflected by the shutter 23 and converts it into heat for consumption.

  The transmission fiber 40 is optically coupled to the condenser lens 21 of the laser oscillator 10, and transmits the coupled laser beam received from the laser oscillator 10 via the condenser lens 21 to the laser beam emitting head 30. Further, the transmission fiber 40 is provided with a core 41 having a substantially circular cross section at the axial center, and a clad 42 provided in contact with the outer peripheral surface of the core 41 and coaxially with the core 41. The refractive index of the clad 42 is the refractive index of the core 41. It is comprised so that it may become lower than a rate. Although not shown, the surface of the clad 432 is covered with a coating.

  The laser beam emission head 30 irradiates the combined laser beam LB transmitted by the transmission fiber 40 toward the outside. For example, in the laser processing apparatus 100 shown in FIG. 1, the combined laser beam LB is emitted toward a workpiece (not shown) that is a processing target disposed at a predetermined position.

  The control unit 50 includes a plurality of functional blocks 51 to 54 inside. The signal processing unit 51 receives an image signal observed by the beam camera 24 and performs signal processing such as noise removal and amplification. Further, although the image signal is an analog signal, it may be converted into a digital signal. The calculation unit 52 receives the image signal processed by the signal processing unit 51 and sends a control signal to the laser control unit 53 and the optical component drive control unit 54 based on this signal. The calculation unit 52 sends a control signal to the laser control unit 53 and the optical component drive control unit 54 based on a machining program stored in a storage unit (not shown). In addition, the calculation unit 52 evaluates and determines the beam quality of the combined laser beam LB based on the image signal subjected to signal processing by the signal processing unit 51. That is, it functions as a beam quality determination unit. Based on this determination result, as will be described later, a control signal for driving the shutter 23 is sent to the optical component drive control unit 54, or a laser oscillation stop signal is sent to the laser control unit 53. These will be described in detail later.

  The laser control unit 53 controls the laser oscillation of the laser oscillator 10 based on the control signal received from the calculation unit 52. Specifically, the laser oscillation control and the oscillation stop control of each laser module 11 are performed by supplying control signals such as an output voltage and an ON time to the power source 60 connected to the laser oscillator 10. It is also possible to individually control the laser oscillation for each laser module 11. For example, the laser oscillation output, on-time, etc. may be varied for each laser module 11. The optical component drive control unit 54 controls the operation of optical components (not shown) arranged in the beam combiner 12 and the opening / closing of the shutter 23 arranged in the optical unit 20 based on the control signal received from the calculation unit 52. . The control unit 50 may be provided with functional blocks other than the above four. For example, a storage unit that stores a machining program or the like may be provided. The control unit 50 may control the operation of a manipulator (not shown) to which the laser beam emitting head 30 is attached. Each functional block in the control unit 50 is realized by executing a predetermined program on a general-purpose CPU or a dedicated LSI.

  The power source 60 supplies power for performing laser oscillation to the laser oscillator 10, specifically, each of the plurality of laser modules 11, based on a control signal from the laser control unit 53. The power supplied to each laser module 11 may be different. Alternatively, the power supply to the laser module 11 is stopped to stop the laser oscillation.

[Laser oscillation control procedure]
FIG. 4 shows a flowchart of the laser oscillation control procedure according to this embodiment, and FIG. 5 shows the time dependency of the beam quality of the laser oscillator. FIG. 6A shows an example of the relationship between the laser beam shape pattern and its pass / fail judgment result, and FIG. 6B shows another example of the relationship between the laser beam shape pattern and its pass / fail judgment result.

  First, the laser oscillation control procedure will be described. As shown in FIG. 4, in the laser processing apparatus 100, when construction is started based on the processing program, the laser oscillator 10 receives the control signal from the laser control unit 53 and starts laser oscillation (step S1: Laser oscillation start step). The remainder of the combined laser beam LB emitted from each laser module 11 and combined by the beam combiner 12 is incident on the beam camera 24 by the partial reflection mirror 22, and observation of the laser beam is started (step S2: beam observation step). ). In steps S1 and S2, the shutter 23 is closed, that is, the combined laser beam LB is deflected by the shutter 23 toward the beam damper 25, and the combined laser beam LB is incident on the transmission fiber 40. Absent.

  Next, based on the image signal observed by the beam camera 24, the calculation unit 52, which is a beam quality determination unit, evaluates the quality of the laser beam and determines its quality (step S3: beam quality determination step). Here, the beam quality determination criteria are determined based on the specifications of the laser oscillator 10, the required laser processing specifications in the laser processing apparatus 100, and the like. In the present embodiment, BPP represented by the product of the laser beam radius at the focal point and the half value of the divergence angle of the laser beam is used as an evaluation index for determining the quality of the combined laser beam LB.

  In step S3, if the determination is affirmative, that is, it is determined that the beam quality is good, the combined laser beam LB is incident on the incident end of the transmission fiber 40 with the shutter 23 opened, and the workpiece (FIG. Irradiation of the combined laser beam LB is started (not shown) (step S5: laser beam irradiation step), and predetermined laser processing is performed. When the construction is completed, the shutter 23 is closed and the laser oscillation of the laser oscillator 10, specifically, the laser oscillation of each laser module 11 is stopped (step S6: laser oscillation stop step).

On the other hand, if the determination in step S3 is negative, that is, it is determined that the beam quality is poor, the process proceeds to step S4, and in this state, that is, in a state where the shutter 23 is closed and laser oscillation is continued. It is determined whether or not to wait (standby determination step). The determination in step S4 is also performed by the calculation unit 52, which is a beam quality determination unit, based on the image signal observed by the beam camera 24. If the determination in step S4 is affirmative, the process returns to step S2, and the laser beam observation and the beam quality determination (step S3) are performed again. If the determination in step S4 is negative, the process proceeds to step S6, the shutter 23 is closed, and the laser oscillation of the laser oscillator 10 is stopped. Note that the standby time in the standby determination step is appropriately determined based on the specifications and output of the laser oscillator 10.
In steps S3 and S4, the coupled laser beam LB is not incident on the transmission fiber 40, and the coupled laser beam LB is incident on the transmission fiber 40 only after proceeding to step S5.

[Effects]
As described above, the laser processing apparatus according to the present embodiment combines a plurality of laser modules 11 each emitting a laser beam and a plurality of laser beams emitted from the plurality of laser modules 11 to emit a combined laser beam LB. A beam combiner 12, an optical unit 20 that focuses the combined laser beam LB so as to have a predetermined beam diameter and guides it to the transmission fiber 40, and a laser beam emission head attached to the emission end of the transmission fiber 40. 30 and a control unit 50 that controls the operations of the plurality of laser modules 11 and the optical unit 20.

  The optical unit 20 transmits a part of the combined laser beam LB while receiving the remaining part of the combined laser beam LB and a partial reflection mirror 21 that reflects the remaining part in a direction different from the traveling direction of the combined laser beam LB. A beam camera (beam monitor) 24 for generating a signal, and a shutter 23 provided so as to be movable between a predetermined position on the optical path of the combined laser beam LB and a predetermined position outside the optical path. .

  The control unit 50 further includes a calculation unit (beam quality determination unit) 52 that determines the quality of the combined laser beam LB based on the image signal generated by the beam camera 24. Further, the image signal includes image information which is information regarding the remaining beam shape of the combined laser beam LB and the coupling state between the combined laser beam LB and the incident end of the transmission fiber 40.

  The laser oscillation control method of the present embodiment is a laser oscillation control method in the laser processing apparatus 100 described above, and includes a laser oscillation start step for starting laser oscillation of the laser oscillator 10, in this case, a plurality of laser modules 11. A beam observation step of observing the remainder of the combined laser beam LB with the beam camera 24 to obtain an image signal, and a beam quality determination step of determining the quality of the combined laser beam LB based on image information obtained from the image signal And.

  By configuring the laser processing apparatus 100 in this way, and by configuring the laser oscillation control method in this way, the state of the combined laser beam LB emitted from the laser oscillator 10 can be monitored, and the beam quality can be controlled. It is possible to determine pass / fail, and laser processing can be performed stably. In addition, the accuracy of laser processing can be kept stable. Further, by monitoring the coupling state between the coupled laser beam LB and the transmission fiber 40, the amount of laser beam leaking to the cladding 42 of the transmission fiber 40 can be accurately grasped, and the laser output of the laser processing apparatus 100 can be measured. Loss and damage to the transmission fiber 40 can be reduced. Moreover, generation | occurrence | production of the processing defect in the laser processing apparatus 100 can be suppressed. Further, the abnormality of the laser oscillator 10 can be detected quickly, and it can be restored to a normal state, maintenance can be performed at an appropriate time, and the downtime of the laser processing apparatus 100 can be reduced.

  When the determination result by the calculation unit 52 is bad, the combined laser beam LB is blocked by the shutter 23.

  In particular, according to the laser processing apparatus 100 of the present embodiment, when laser oscillation is started from a state where the laser oscillation of the laser oscillator 10 has been stopped for a long period of time, it is determined whether the beam quality required for desired processing is obtained. Then, the coupling laser beam LB is incident on the transmission fiber 40, so that the transmission fiber 40 can be prevented from being damaged, and laser processing can be performed with a desired processing quality. This will be further described.

  FIG. 5 shows the time change of the beam quality of the laser oscillator from the start of laser oscillation. In FIG. 5, the time point of 0 second corresponds to the laser oscillation start point. In addition, a considerable time has elapsed before the start of laser oscillation, and the temperature of the laser oscillator 10 is sufficiently lowered.

  As is clear from FIG. 5, BPP, which is an evaluation index of laser quality, starts to decrease from the start of laser oscillation and stabilizes over a time of 20 seconds or more. In addition, the stable bpp is about 30% less than the BPP immediately after the start of laser oscillation. As is clear from the definition, the beam quality is better when the value of Bpp is smaller. As described above, the output of the laser module 11 and the arrangement of various optical components in the laser oscillator 10 are adjusted in accordance with the steady operation state. In the steady operation state, the laser module 11 that emits a laser beam generates heat and the temperature rises. In addition, the temperature of various optical components also rises due to slight heat absorption when the laser beam is transmitted and internal temperature of the housing and the like.

  On the other hand, as shown in FIG. 5, the temperature of each part is not in a steady state immediately after the start of laser oscillation, and when the combined laser beam LB is irradiated onto the workpiece in such a state, the combined laser beam LB is predetermined. It is in a state where it has expanded more than the value of. In such a state, for example, there is a possibility that the cutting width becomes too wide to perform desired processing, or that the leak light to the cladding 42 of the transmission fiber 40 becomes too large and the transmission fiber 40 is damaged. It was.

  The laser processing apparatus 100 of the present embodiment accurately evaluates the beam quality of the combined laser beam LB based on the image signal generated by the beam camera 24. If the quality is poor, the combined laser beam LB is transmitted. Before being incident on the fiber 40, it is blocked by the shutter 23. As a result, the workpiece can be laser processed with the combined laser beam LB having the set beam shape. Further, light leaking to the cladding 42 of the transmission fiber 40 can be reduced, and damage to the transmission fiber 40 can be reduced.

  The control unit 50 includes a laser control unit 53 that controls the operation of the laser module 11, an optical component drive control unit 54 that controls the operation of the shutter 23, and a calculation unit 52. The calculation unit 52 is configured to send a control signal for determining opening / closing of the shutter 23 based on the quality determination result of the combined laser beam LB to the optical component drive control unit 54. In addition, the calculation unit 52 is configured to send a control signal for stopping the laser oscillation of the laser module 11 to the laser control unit 53 based on the quality determination result.

  By doing so, when the beam quality of the combined laser beam LB is good, the shutter 23 can be opened and the workpiece can be irradiated with the combined laser beam LB via the transmission fiber 40. Further, when the beam quality is poor, the laser oscillation of the laser module 11 can be stopped by closing the shutter 23. In addition, by configuring the shutter 23 so that the closed state is maintained until the quality determination result of the combined laser beam LB becomes good, a laser beam with a deteriorated beam quality is surely incident on the transmission fiber 40, Can be prevented from being irradiated.

  In addition, the laser oscillation control method of the present embodiment further includes a standby determination step for determining whether or not to maintain the shutter 23 in the closed state if the quality determination result of the combined laser beam LB is negative. If the determination result in the standby determination step is negative, the shutter 23 is kept closed and the laser oscillation of the laser oscillator 10 is stopped. In the standby determination step, it is determined whether or not the shutter 23 is to be kept closed based on the beam shape of the combined laser beam LB and / or the combined state of the combined laser beam LB and the transmission fiber 40.

  According to this method, when the beam quality of the combined laser beam LB is poor, it can be accurately determined whether it is temporary or constantly generated. Thus, unnecessary maintenance of the laser processing apparatus 100 can be eliminated and downtime can be reduced. This will be further described.

  FIG. 6A shows an example of the relationship between the spot shape of the laser beam and its quality determination result, and FIG. 6B shows another example of the relationship between the spot shape of the laser beam and its quality determination result. The spot shapes shown in FIGS. 6A and 6B are obtained by projecting the remaining portion of the combined laser beam LB observed by the beam camera 24 onto a flat surface (imaging surface), and the combined laser beam LB near the focal point of the condenser lens 21. It corresponds to the beam shape. Reference numerals 41 and 42 shown in FIGS. 6A and 6B are obtained by virtually projecting the core 41 and the clad 42 at the incident end of the transmission fiber 40 onto a plane (imaging surface). The positional relationship with 42 corresponds to the coupled state of the coupled laser beam LB and the transmission fiber 40. Such information, that is, the spot shape and the positional relationship between the spot and the core 41 and the clad 42 are included in the image information generated by the beam camera 24.

  6A shows a spot shape when the beam quality of the combined laser beam LB is good. The spot is equal to or smaller than the core diameter of the core 41 and is within the core 41. This indicates that the actual coupled laser beam LB is incident on the core 41 without leaking into the cladding 42 of the transmission fiber 40. Thus, if the beam quality of the combined laser beam LB is good, the combined laser beam LB is irradiated onto the workpiece via the transmission fiber 40 as shown in FIG.

  On the other hand, the spot shown in the middle of FIG. 6A has the center substantially coincident with the center of the core 41, but protrudes from the core 41 and covers the clad 42. The spot shown in the lower stage is shifted from the center of the core 41. In addition, the spot protrudes from the core 41 and hits the clad 42. In these cases, the beam quality is determined to be poor. However, the situation shown in the middle and lower parts of FIG. 6A may converge in the case shown in the upper part of FIG. 6A as the laser oscillation time elapses. In the case shown in the middle part of FIG. 6A, the temperature of each optical component is rising, the thermal lens effect is not stable, and the focus may be deviated. In the case shown in the middle part of FIG. 6A, the temperature of each optical component is rising, and the optical axis of the laser beam may be shifted.

  Therefore, as shown in this embodiment, a standby determination step is provided, and the temperature of each part in the laser oscillator 10 is stabilized by closing the shutter 23 while continuing laser oscillation for a predetermined time. Wait for the beam quality can be evaluated again. If the beam quality is improved as a result of the re-evaluation, it can be understood that the laser oscillator 10 was not in a stable state at the time of the previous evaluation, and the laser oscillation can be stopped and the occurrence of downtime can be prevented. Also, unnecessary maintenance is not required. As shown in FIG. 4, if the beam quality is determined to be defective after the standby determination step, the laser oscillation of the laser oscillator 10 is stopped while the shutter 23 is closed, and the cause of the defect is determined. Need to investigate.

  On the other hand, FIG. 6B shows a state where laser oscillation should be stopped. In the case shown in the upper part of FIG. 6B, the spot is separated into two, and one spot protrudes from the core 41 and covers the clad 42. In such a case, it is considered that an optical axis shift of a specific laser beam is caused by a displacement or damage of some optical fixtures in the beam combiner 12.

  Further, in the case shown in the middle stage of FIG. 6B, the amount of spot deviation with respect to the core 41 is larger than, for example, the case shown in the lower stage of FIG. 6A. In such a case, there is a possibility that an optical component in the beam combiner 12 is misplaced or the condenser lens 21 in the optical unit 20 is misplaced.

  In the case shown in the lower part of FIG. 6B, the spot protrudes from the core 41 and is applied to the clad 42, and the spot shape is deformed into an elliptical shape. In such a case, for example, the surface of the condenser lens 21 may be contaminated or the condenser lens 21 itself may be damaged.

In these cases, as shown in step S6 in FIG. 4, it is necessary to stop the laser oscillation and investigate the cause of the defect. in this way,
In the present embodiment, the laser oscillator 10 has four laser modules 11 having a maximum output of 1 kW arranged in parallel to output a 4 kW laser beam. However, the present invention is not limited to this.

  Further, the beam camera 24 in the present embodiment may be a light receiving element array.

  The laser processing apparatus of the present invention is useful as a laser processing apparatus that requires high processing accuracy because the beam quality of the emitted laser beam can be monitored and maintained satisfactorily.

DESCRIPTION OF SYMBOLS 10 Laser oscillator 11 Laser module 12 Beam combiner 20 Optical unit 21 Condensing lens 22 Partial reflection mirror 23 Shutter 24 Beam camera (beam monitor)
30 Laser beam emitting head 40 Transmission fiber 41 Core 42 Clad 50 Control unit 51 Signal processing unit 52 Calculation unit (beam quality judgment unit)
53 Laser control unit 54 Optical component drive control unit 60 Power supply 100 Laser processing apparatus LB Coupled laser beam

Claims (12)

A plurality of laser modules that respectively emit laser beams, a beam combiner that combines a plurality of laser beams emitted from the plurality of laser modules and emits them as a combined laser beam, and a combined laser beam emitted from the beam combiner An optical unit for condensing the light so as to have a predetermined beam diameter and guiding it to the transmission fiber, a laser beam emission head attached to the emission end of the transmission fiber, the operations of the plurality of laser modules and the optical unit A laser processing apparatus comprising at least a control unit for controlling
The optical unit transmits a part of the combined laser beam, while reflecting the remaining part in a direction different from the traveling direction of the combined laser beam, and the combined laser beam reflected by the partial reflection mirror. A beam monitor that receives the remainder and generates an image signal; and a shutter that is movable between a predetermined position on the optical path of the combined laser beam and a predetermined position outside the optical path;
The laser processing apparatus, wherein the control unit further includes a beam quality determination unit that determines the quality of the combined laser beam based on the image signal generated by the beam monitor. In the laser processing apparatus of Claim 1,
When the determination result by the beam quality determination unit is poor, the combined laser beam is blocked by the shutter. In the laser processing apparatus according to claim 1 or 2,
The control unit includes at least a laser control unit that controls the operation of the laser module, an optical component drive control unit that controls the operation of the shutter, and the beam quality determination unit,
The beam quality determination unit sends a control signal for determining opening / closing of the shutter based on the quality determination result of the combined laser beam to the optical component drive control unit, and the laser based on the quality determination result A laser processing apparatus configured to send a control signal for stopping laser oscillation of the laser module to the control unit. The laser processing apparatus according to any one of claims 1 to 3,
The laser processing apparatus, wherein the shutter is configured to maintain a closed state until a quality determination result of the combined laser beam becomes good. 5. The laser processing apparatus according to claim 1, wherein the image signal includes information on a remaining beam shape of the coupled laser beam and a coupling state between the coupled laser beam and the transmission fiber. A laser processing apparatus characterized by the above. A laser oscillation control method in a laser processing apparatus according to any one of claims 1 to 5,
A laser oscillation start step for starting laser oscillation of the plurality of laser modules;
A beam observation step of obtaining an image signal by observing the remainder of the combined laser beam with the beam monitor;
A laser oscillation control method, comprising: a beam quality determination step of determining whether the combined laser beam is good or bad based on image information obtained from the image signal. In the laser oscillation control method according to claim 6,
If the determination result in the beam quality determination step is affirmative, the combined laser beam is irradiated from the laser beam emitting head through the transmission fiber with the shutter opened, and the determination result is negative. If there is, the laser oscillation control method characterized by maintaining the shutter in a closed state. In the laser oscillation control method according to claim 7,
If the determination result is negative, the laser oscillation control method is characterized in that the shutter is kept closed and the laser oscillation of the laser oscillator is stopped. In the laser oscillation control method according to any one of claims 6 to 8,
A laser oscillation control method, further comprising a standby determination step for determining whether or not to maintain the shutter in a closed state if the result of the quality determination of the combined laser beam is negative. The laser oscillation control method according to claim 9, wherein
If the determination result in the standby determination step is negative, the laser oscillation control method is characterized in that the shutter is kept closed and the laser oscillation of the laser oscillator is stopped. The laser oscillation control method according to claim 9 or 10,
The image information includes information on the remaining beam shape of the coupled laser beam and the coupled state of the coupled laser beam and the transmission fiber,
In the standby determination step, it is determined whether to maintain the shutter in the closed state based on the beam shape and / or the coupling state between the coupled laser beam and the transmission fiber. Method. The laser oscillation control method according to any one of claims 6 to 11,
The image information includes information on the remaining beam shape of the coupled laser beam and the coupled state of the coupled laser beam and the transmission fiber,
In the beam quality determination step, the quality of the combined laser beam is determined based on the beam shape and / or the combined state of the combined laser beam and the transmission fiber.