Device for changing the numerical aperture, laser device and laser beam machine

Abstract

A device for changing the numerical aperture to realign spatial distributions or spatial positions of several laser beams (LA, LB) incident from a laser oscillator, and to condense the several realigned laser beams (LA, LB) for entry of the beams into a transmission fiber, wherein the device for changing the numerical aperture comprises: a light-shielding component (326-1, 326-2) provided in an extension of the optical axis of the transmission fiber, wherein the light-shielding component (326-1, 326-2) blocks a reflected laser beam, wherein the reflected laser beam is a laser beam traveling from the transmission fiber to the laser oscillator.

Description

Area

[0001] The present disclosure relates to a numerical aperture changing apparatus, a laser apparatus, and a laser beam machine that change a numerical aperture of a transmission fiber. State of the art

[0002] A laser beam machine generally includes a laser oscillator, a condenser lens (or condenser), a transmission fiber, and a processing head. The condenser lens condenses (collects) a laser beam emitted by the laser oscillator. The transmission fiber transmits the laser beam condensed by the condenser lens. The processing head guides the laser beam from the transmission fiber to a desired location on a workpiece. Among such laser beam machines, a well-known laser beam machine is one in which multiple laser beams enter a single transmission fiber for the purpose of achieving higher output.

[0003] Document 1 discloses a beam parameter adjustment system that changes the spatial distribution of multiple beams with a polarization state and a collective spatial distribution from a beam source, and converges the beams with the changed spatial distribution onto an end face of a transmission fiber. In the technology described in Document 1, the respective polarization state of the multiple beams is changed. As a result, the spatial distribution of the beams entering the transmission fiber is changed to adjust the parameter product of an output beam from the transmission fiber. Citation listPatent literature

[0004] Publication 1: Japanese translation of the published international (PCT) application No. 2017-506769 Brief description of the inventionProblem to be solved by the invention

[0005] In a case where the technology described in Reference 1 is applied to a laser beam machine including a transmission fiber with the same incident axis as an incident laser beam axis on one side of the beam-emitting source, a laser beam reflected from a workpiece unfortunately returns to a laser oscillator serving as the beam-emitting source because the reflected laser beam is distributed centrally on the incident axis of the transmission fiber. This poses a problem of damage to the laser oscillator by the reflected laser beam.

[0006] The present disclosure has been made in view of the above, and it is an object of the present disclosure to obtain a numerical aperture changing device capable of preventing a laser oscillator from being damaged by a reflected laser beam returning in a central distribution around an incident axis of a transmission fiber. Means of solving the problem

[0007] To solve the problem and achieve the object, the present disclosure provides a numerical aperture changing device, namely, for realigning the spatial distributions or spatial arrangements of a plurality of laser beams incident from a laser oscillator, and for condensing the plurality of realigned laser beams to enter a transmission fiber, the numerical aperture changing device including: a light-shielding member provided in an extension of the optical axis of the transmission fiber, the light-shielding member blocking a reflected laser beam, the reflected laser beam being a laser beam traveling from the transmission fiber to the laser oscillator. Effects of the invention

[0008] The numerical aperture changing device according to the present disclosure has the effect of preventing a laser oscillator from being damaged by a reflected laser beam returning in a central distribution around an incident axis of the transmission fiber. Short description of the drawings Fig. 1 is a diagram schematically showing an exemplary configuration of a laser beam machine according to a first embodiment. Fig. 2 is a diagram schematically showing an exemplary configuration of a numerical aperture changing apparatus according to a first embodiment. Fig. 3 is a side view of a beam pitch changer schematically showing an exemplary configuration of the beam pitch changer in the numerical aperture changing apparatus according to the first embodiment. Fig. 4 is a diagram schematically showing an exemplary method of changing the numerical aperture in the numerical aperture changing apparatus according to the first embodiment. Fig. 5 is a diagram showing an example of changes in the state of arrangement of laser beams in an XY plane of Fig. 4 shows. Fig. 6 is a diagram showing an exemplary hardware configuration of a control device of the laser beam machine according to the first embodiment. Description of the embodiments

[0009] Hereinafter, a numerical aperture changing apparatus, a laser apparatus, and a laser beam machine according to an embodiment of the present disclosure will be described in more detail with reference to the drawings. First embodiment.

[0010] Fig. 1 is a diagram schematically showing an exemplary configuration of a laser beam machine according to a first embodiment. A laser beam machine 1 is a machine tool that machines a machining target or workpiece 61 by irradiating it with a laser beam L, which is a laser beam.

[0011] The laser beam machine 1 includes a laser device 10, a transmission fiber 40, a processing head 50, a processing table 60, and a control unit 70. The laser device 10 outputs a laser beam L. The transmission fiber 40 transmits the laser beam L. The processing head 50 irradiates the workpiece 61 with the laser beam L from the transmission fiber 40. The processing table supports the workpiece 61. The control unit 70 controls the entire laser beam machine 1.

[0012] The laser device 10 includes a laser oscillator 20 and a numerical aperture (NA) changing device 30. The laser oscillator 20 is a light source. The numerical aperture changing device 30 changes the numerical aperture upon entering the transmission fiber 40.

[0013] The laser oscillator 20 is a light source that emits laser beams LA and LB, such as a solid-state laser, a gas laser, or a semiconductor laser. The laser oscillator 20 emits the plurality of laser beams LA and LB. A single laser oscillator 20 can emit the plurality of laser beams LA and LB. Alternatively, a plurality of the laser oscillators 20 can each emit a corresponding one of the laser beams LA and LB. The laser oscillator 20 is arranged such that the positions of the plurality of laser beams LA and LB are symmetrical with respect to an extension of an optical axis of the transmission fiber 40. The laser oscillator 20 causes the plurality of laser beams LA and LB to enter the numerical aperture changing device 30. The numerical aperture changing device 30 connects the laser oscillator 20 and the transmission fiber 40. The numerical aperture changing device 30 realigns or redetermines the spatial distributions or spatial positions of the plurality of laser beams LA and LB arriving from the laser oscillator 20, and condenses the thus realigned plurality of LA and LB beams for entry into an input end of the transmission fiber 40. A laser beam obtained by condensing the plurality of laser beams LA and LB and propagated through the transmission fiber 40 is referred to as the laser beam L. Numerical apertures represent a measure of an acceptance angle and an exit angle for the transmission fiber 40. The numerical aperture changing device 30 may also be referred to as a device that changes the numerical entrance aperture and exit aperture of the transmission fiber 40.

[0014] The acceptance angle of the transmission fiber 40 has a maximum value. The maximum value indicates a maximum acceptance angle at which a laser beam can pass through the transmission fiber 40 in total internal reflection. Furthermore, the input numerical aperture has a minimum value in addition to a value corresponding to the above-described maximum acceptance angle. The minimum value is determined by the quality of a laser beam output from the laser oscillator 20 and the structure of the numerical aperture changing device 30, as will be described below. The numerical aperture changing device 30 changes the input numerical aperture such that the input numerical aperture lies between the minimum value and the maximum value of the input numerical aperture. The input numerical aperture is adjusted by realigning or redetermining the spatial distributions or spatial positions of the plurality of laser beams LA and LB.An example of realigning the multiple laser beams LA and LB is changing the beam spacing between the multiple laser beams LA and LB. Note that . Fig. 1 schematically shows the device 30 for changing the numerical aperture. In Fig. 1, the broken arrows shown between the laser oscillator 20 and the input end of the transmission fiber 40 indicate how the laser beams LA and LB pass through the numerical aperture changing device 30.

[0015] The input end of the transmission fiber 40 is connected to the laser device 10, specifically the numerical aperture changing device 30. An output end of the transmission fiber 40 is connected to the processing head 50. The laser beam L transmitted through the transmission fiber 40 enters the processing head 50. The transmission fiber 40, which is an optical waveguide that transmits the laser beam L, includes a core and a cladding. The cladding covers a periphery of the core with a material having a lower refractive index than the refractive index of the core. Such a structure of the transmission fiber 40 allows the laser beam L to travel in total internal reflection, with an input numerical aperture equal to or smaller than the maximum value of the input numerical aperture of the transmission fiber 40.

[0016] The processing head 50 is connected to the laser device 10 via the transmission fiber 40 and irradiates the workpiece 61 with the laser beam L transmitted through the transmission fiber 40. The processing head 50 includes a transmission optical system 51 that guides the laser beam L to an emission port of the processing head 50. Thus, the processing head 50 directs the laser beam L to a predetermined location on the workpiece 61. Although not shown, the transmission optical system 51 includes a condensing optical system that condenses the laser beam L from the transmission fiber 40. The laser beam L emitted by the processing head 50 impinges on the workpiece 61. Fig. 1, a broken arrow between the exit end of the transmission fiber 40 and the workpiece 61 indicates how the laser beam L emitted from the exit end of the transmission fiber 40 reaches the workpiece 61.

[0017] The machining table 60 is a table on which the workpiece 61 is placed. The machining table 60 preferably has a fixing mechanism that fixes the workpiece 61 so that it does not move during machining.

[0018] The laser beam machine 1 moves the laser beam L and the workpiece 61 relative to each other by moving the processing table 60 with respect to the processing head 50. Note that the laser beam machine 1 can move the laser beam L and the workpiece 61 relative to each other without moving the processing table 60. The laser beam machine 1 can fix the position of the processing table 60 and control the irradiation position of the laser beam L on the workpiece 61.

[0019] The control unit 70 transmits a control signal to each of the laser oscillator 20, the numerical aperture changing device 30, the processing head 50, and the processing table 60, and controls their operation. The laser oscillator 20 outputs the laser beams LA and LB according to the control signal. The numerical aperture changing device 30 operates according to the control signal for changing the input numerical aperture of the transmission fiber 40 for the laser beam L. The processing head 50 operates according to the control signal. The processing table 60 operates according to the control signal. In this way, the control device 70 controls each of the laser oscillator 20, the numerical aperture changing device 30, the machining head 50, and the machining table 60. Note that a processor unit of the control device 70 that controls the operation of the numerical aperture changing device 30 is a control device that causes the numerical aperture changing device 30 to operate.Thus, the processor unit can be considered as part of the device 30 for changing the numerical aperture.

[0020] The control device 70, which controls the numerical aperture changing device 30 for changing the input numerical aperture of the transmission fiber 40, adjusts the output numerical aperture at the output end of the transmission fiber 40. That is, the numerical aperture changing device 30 and the control device 70 control the input numerical aperture of the transmission fiber 40, thereby controlling the output numerical aperture of the transmission fiber 40.

[0021] Next, the numerical aperture changing device 30 will be described in more detail. Fig. 2 is a diagram schematically showing an exemplary configuration of a numerical aperture changing apparatus according to the first embodiment. Fig. Figure 2 shows not only the device 30 for changing the numerical aperture, but also the laser oscillator 20 and the transmission fiber 40. Furthermore, Fig. 2 illustrates a case where the numerical aperture changing device 30 changes the input numerical aperture of the transmission fiber 40 by changing a distance between the two laser beams LA and LB, that is, the laser beam LA from a laser oscillator 20A and the laser beam LB from a laser oscillator 20B. Suppose a Z-axis direction is defined as a direction in which the laser beams LA and LB travel in the laser oscillators 20A and 20B, and two axes perpendicular to the Z-axis are defined as an X-axis and a Y-axis. In this case, the laser oscillators 20A and 20B are arranged side by side along a Y-axis direction. In addition, the laser oscillators 20A and 20B are arranged such that the laser oscillators 20A and 20B are symmetrical with respect to an extension, which is an extended optical axis of the transmission fiber 40.

[0022] The numerical aperture changing device 30 includes a beam pitch changer 31 and a condensing optical system 33. The beam pitch changer 31 changes a beam pitch between the multiple laser beams LA and LB. The condensing optical system 33 concentrates the laser beams LA and LB with the changed beam pitch into the entrance end of the transmission fiber 40.

[0023] In a case where the beam characteristics of the plurality of laser beams LA and LB are aligned in an XY plane, the beam pitch changer 31 includes two or more beam pitch changing units 32-1 and 32-2. In the example of Fig. 2, the beam pitch changer 31 includes two beam pitch changing units 32-1 and 32-2. The beam pitch changing unit 32-1 changes a beam pitch in a first direction perpendicular to the Z-axis. The beam pitch changing unit 32-2 changes a beam pitch in a second direction different from the first direction. The beam pitch changer 31 changes a beam pitch ΔP1-1 between the laser beams LA and LB emitted from the laser oscillators 20A and 20B, respectively, to a beam pitch ΔP2-2. In this case, the first direction corresponds to an X-axis direction, and the second direction corresponds to the Y-axis direction. Furthermore, changing the distance between the laser beams LA and LB corresponds to changing the positions of the laser beams LA and LB in the XY plane. In other words, the beam pitch changer 31 is a device that changes the arrangement of the plurality of laser beams LA and LB in the XY plane.

[0024] The condensing optical system 33 condenses the laser beams LA and LB with the beam pitch changed by the beam pitch changer 31, and causes the laser beams LA and LB to enter the transmission fiber 40. The condensing optical system 33 includes one or more lenses. In the example of Fig. 2 is a single lens, but may include two or more lenses. Note that in the case of an optical system 33 including two or more lenses, the input numerical aperture NA_in of the transmission fiber 40 may also be changed by the condensing optical system 33.

[0025] As in Fig. As shown in Figure 2, the transmission fiber 40 includes a core 41 and a cladding 42. The cladding 42 covers the periphery of the core 41 and is made of a material with a lower refractive index than the refractive index of the core. The laser beam L concentrated at the input end of the transmission fiber 40 follows the paths indicated by dashed lines by total internal reflection and is emitted at the output end with a numerical output aperture NA_out determined in conjunction with the numerical input aperture NA_in.

[0026] Fig. 3 is a side view of the beam pitch changer, schematically showing an exemplary configuration of the beam pitch changer in the numerical aperture changing device according to the first embodiment. As described above, the beam pitch changer 31 includes the beam pitch changing unit 32-1 and the beam pitch changing unit 32-2.

[0027] The beam pitch changing unit 32-1 includes a beam realignment unit 321-1 and a light shielding member 326-1. The beam realignment unit 321-1 includes a combination of two flat transmission plates 322-1 and 323-1 that transmit the laser beams LA and LB, respectively. The two transmission plates 322-1 and 323-1 of the beam realignment unit 321-1 are rectangular plate-like flat substrates of the same size. The two transmission plates 322-1 and 323-1 are arranged at a predetermined interval in the Y-axis direction. A rotation shaft (not shown) is arranged at the center of the transmission plate 322-1 in a ZX plane, and a rotation mechanism (not shown) is arranged on the rotation shaft. As a result, the transmission plate 322-1 rotates around the rotation shaft (not shown).A rotation shaft 325-1 is arranged at the center of the transmission plate 323-1 on a ZX plane, and a rotation mechanism (not shown) is arranged on the rotation shaft 325-1. As a result, the transmission plate 323-1 rotates around the rotation shaft 325-1. The two transmission plates 322-1 and 323-1 are arranged such that the transmission plates 322-1 and 323-1 are inclined by the same angle θ1 in opposite directions with respect to a straight line A1. The straight line A1 passes through the rotation shaft 325-1 and is parallel to the X-axis. Assuming that a clockwise rotation direction from the straight line A1 is defined as a positive direction and a counterclockwise rotation direction is defined as a negative direction, the transmission plates 322-1 and 323-1 are in the example of . Fig. 3 such that the transmission plate 322-1 is tilted at an angle of θ1, and the transmission plate 323-1 is tilted at an angle of -θ1. The two transmission plates 322-1 and 323-1 are arranged symmetrically with respect to the optical axis of the transmission fiber 40. The rotation mechanisms rotate the respective one of the two transmission plates 322-1 and 323-1 according to an instruction from the control unit 70.

[0028] The light-shielding member 326-1 is a member arranged on the extension of the optical axis of the transmission fiber 40 and blocks a reflected laser beam traveling from the transmission fiber 40 to the laser oscillators 20A and 20B. That is, the light-shielding member 326-1 is arranged to prevent a laser beam reflected from the workpiece 61 from returning to the laser oscillator 20. In the example of Fig. 3, the light shielding member 326-1 is arranged between the two transmission plates 322-1 and 323-1, and has a shape extending in the X-axis direction.

[0029] The beam pitch changing unit 32-2 includes a beam realignment unit 321-2 and a light shielding member 326-2. The beam realignment unit 321-2 includes a combination of two flat transmission plates 322-2 and 323-2 that transmit the laser beams LA and LB, respectively. The two transmission plates 322-2 and 323-2 of the beam realignment unit 321-2 are rectangular plate-like flat substrates of the same size. The two transmission plates 322-2 and 323-2 are arranged at a predetermined distance in the X-axis direction. A rotation shaft 324-2 is arranged at the center of the transmission plate 322-2 in a YZ plane, and a rotation mechanism (not shown) is arranged on the rotation shaft 324-2. As a result, the transmission plate 322-2 rotates around the rotation shaft 324-2.A rotating shaft 325-2 is arranged at the center of the transmission plate 323-2 in the YZ plane, and a rotating mechanism (not shown) is arranged on the rotating shaft 325-2. As a result, the transmission plate 323-2 rotates around the rotating shaft 325-2. The two transmission plates 322-2 and 323-2 are arranged such that the transmission plates 322-2 and 323-2 are inclined by the same angle in opposite directions with respect to a straight line passing through the rotating shafts 324-2 and 325-2 parallel to the Y-axis. The two transmission plates 322-2 and 323-2 are arranged symmetrically with respect to the optical axis of the transmission fiber 40. The rotating mechanisms rotate the respective one of the two transmission plates 322-2 and 323-2 according to an instruction from the control unit 70.

[0030] The light-shielding member 326-2 is a member disposed on the extension of the optical axis of the transmission fiber 40 and blocks a reflected laser beam traveling from the transmission fiber 40 to the laser oscillators 20A and 20B. That is, the light-shielding member 326-2 is arranged to prevent a laser beam reflected from the workpiece 61 from returning to the laser oscillator 20. In one example, the light-shielding member 326-2 may be disposed between the two transmission plates 322-2 and 323-2 and may have a shape extending in the Y-axis direction.

[0031] The transmission plates 322-1, 322-2, 323-1, and 323-2 are preferably made of an optically isotropic material that is transparent to wavelengths of the laser beams 20A and 20B oscillated by the laser oscillator 20. In the case where the laser oscillators 20A and 20B are fiber lasers that oscillate the laser beams LA and LB with wavelengths around 1070 nm, an example of the transmission plates 322-1, 322-2, 323-1, and 323-2 is a glass substrate, such as synthetic quartz.

[0032] The light-shielding members 326-1 and 326-2 are provided for the plurality of beam pitch changing units 32-1 and 32-2, respectively, and are arranged on sides closer to the transmission fiber 40 with respect to the beam pitch changing units 32-1 and 32-2, respectively. The light-shielding members 326-1 and 326-2 only need to perform some light-shielding for reflecting or absorbing the laser beam. A material for use as the light-shielding members 326-1 and 326-2 depends on the wavelength of the laser beam L to be emitted from the laser oscillator 20. An example of the light-shielding members 326-1 and 326-2 in the case of performing light-shielding by reflection is surface-treated copper. An example of the light-shielding components 326-1 and 326-2 in the case of performing light-shielding by absorption is aluminum that has been subjected to anodization (alumite treatment).Furthermore, the light-shielding components 326-1 and 326-2 can each have a cooling mechanism. The cooling mechanisms include tubes and refrigerant supply units. The tubes are provided in the light-shielding components 326-1 and 326-2 or in contact with the light-shielding components 326-1 and 326-2. Each refrigerant supply unit allows a refrigerant to flow through the tube. An example of the refrigerant is water. The flow of water from the refrigerant supply units through the tubes will prevent an increase in the temperature in the light-shielding components 326-1 and 326-2.

[0033] The light-shielding member 326-1 is arranged between the transmission plates 322-1 and 323-1, and the light-shielding member 326-2 is arranged between the transmission plates 322-2 and 323-2. For this reason, the size and / or arrangement of the light-shielding members 326-1 and 326-2 is determined such that the output loss due to the blocking of the plurality of laser beams LA and LB at the light-shielding members 326-1 and 326-2 becomes 10% or less when the spatial distributions or spatial arrangements of the plurality of laser beams LA and LB are brought closest to each other in the numerical aperture changing device 30. Thus, the Fig. 3 is an example of the shape of the light-shielding members 326-1 and 326-2, and the light-shielding members 326-1 and 326-2 may have other shapes.

[0034] The laser beams LA and LB each have a curved beam intensity. That is, the laser beams LA and LB provide a Gaussian distribution, with the beam intensity being high in the center and decreasing towards the edges. In this case, the Gaussian beam diameter is defined as the beam width of a beam with a beam intensity that decreases from a peak by 1 / e 2is reduced. When this Gaussian beam diameter is used, the laser beams LA and LB have regions approximately 10% outside the Gaussian beam diameter. Considering that the Gaussian beam diameter regions of the laser beams LA and LB pass through the transmission plates, it is desirable that the output loss caused by the blocking at the light-shielding members 326-1 and 326-2 be limited to 10% or less as described above. In addition, optical components of the laser beam machine 1 are generally optically constructed with a Gaussian beam diameter in many cases. In view of this, it is desirable to design the optical components such that the output loss caused by the blocking at the light-shielding members 326-1 and 326-2 is limited to 10% or less.

[0035] A method for adjusting the beam spacing in the numerical aperture changing device 30 will be described below. Fig. 4 is a diagram schematically showing an exemplary method of changing a numerical aperture in the numerical aperture changing apparatus according to the first embodiment. Fig. Fig. 4 shows only the beam pitch changing units 32-1 and 32-2 of the device 30 for changing the numerical aperture of Fig. 2. In addition, Fig. 4 shows, for convenience, side views of the beam pitch changing units 32-1 and 32-2, viewed from a Y-axis direction, and side views of the beam pitch changing units 32-1 and 32-2, viewed from an X-axis direction. That is, Fig. 4 shows simultaneously plan views of the beam pitch changing units 32-1 and 32-2 onto the ZX plane and plan views of the beam pitch changing units 32-1 and 32-2 onto the YZ plane.

[0036] In the beam spacing changer 31 of the device 30 for changing the numerical aperture of Fig. 4, the beam pitch changing unit 32-1 is arranged on a side closer to the laser oscillator 30, and the beam pitch changing unit 32-2 is arranged on a side closer to the transmission fiber 40. The beam pitch changing unit 32-1 changes a beam pitch in the X-axis direction without changing a beam pitch in the Y-axis direction. The beam pitch changing unit 32-2 changes a beam pitch in the Y-axis direction without changing a beam pitch in the X-axis direction. Note that the method is exemplified in Fig. 4, and the beam pitch changing unit 32-1 and the beam pitch changing unit 32-2 can change beam pitches in any mutually different directions.

[0037] In the example of Fig. 4, the transmission plates 322-1 and 323-1 of the beam pitch changing unit 32-1 are rotated by angles of θ1 and -θ1, respectively, with respect to the straight line A1. Furthermore, the transmission plates 322-2 and 323-2 of the beam pitch changing unit 32-2 are rotated by angles of θ2 and -θ2, respectively, with respect to a straight line A2. The straight line A2 is a straight line passing through the rotation shafts 324-2 and 325-2 parallel to the X-axis. The angles θ1 and θ2 are set to any desired angles such that the incident numerical aperture NA_in of the transmission fiber 40 has a predetermined value.

[0038] Assume that the laser oscillators 20A and 20B are arranged symmetrically with respect to the optical axis of the transmission fiber 40 with a pitch in the Y-axis direction. The laser oscillators 20A and 20B output the laser beams LA and LB, respectively. A beam pitch between the laser beams LA and LB in the X-axis direction is referred to as ΔP1-1x, and a beam pitch between them in the Y-axis direction is referred to as ΔP1-1y.

[0039] Fig. 5 is a diagram showing an example of changes in the state of arrangement of laser beams in an XY plane of Fig. 4 shows. Fig. Fig. 5 shows arrangement states in a plane perpendicular to the direction in which the laser beams LA and LB travel, at the positions R1, R2 and R3 in optical paths of the laser beams LA and LB in Fig. 4. Before entering the beam pitch changing unit 32-1, the laser beams LA and LB are arranged at a pitch in the Y-axis direction, as shown in the arrangement state C1 at location R1. Furthermore, the laser beams LA and LB have a beam shape that is narrower in the X-axis direction than in the Y-axis direction, that is, an elliptical beam shape with a larger diameter in the Y-axis direction than in the X-axis direction. Then, the laser beams LA and LB enter the beam pitch changing unit 32-1 in the arrangement state C1.

[0040] Returning to Fig. 4, the two transmission plates 322-1 and 323-1 in the beam pitch changing unit 32-1 are arranged at a distance in the Y-axis direction, and a rotation shaft 324-1 and the rotation shaft 325-1 are parallel to the Y-axis. The transmission plate 322-1 is arranged to transmit the laser beam LA from the laser oscillator 20A, and the transmission plate 323-1 is arranged to transmit the laser beam LB from the laser oscillator 20B. Furthermore, the two transmission plates 322-1 and 323-1 in the beam pitch changing unit 32-1 are rotatable about the Y-axes. As described above, the transmission plate 322-1 and the transmission plate 323-1 are arranged such that the transmission plate 322-1 is inclined at an angle θ1 with respect to the straight line A1, and the transmission plate 323-1 is inclined at an angle -θ1 with respect to the straight line A1.It is possible to change a beam pitch in the X-axis direction by arranging the beam realignment unit 321-1 in this manner.

[0041] The laser beams LA and LB enter the beam pitch changing unit 321-1. The laser beam LA enters the transmission plate 322-1, and the laser beam LB enters the transmission plate 323-1. The laser beams LA and LB are refracted upon entering the transmission plates 322-1 and 323-1, respectively. The laser beams LA and LB appear to travel in straight lines when viewed from a direction in which no incident angle is provided, that is, when viewed in the YZ plane. Furthermore, the two transmission plates 322-1 and 323-1 are inclined by the same angle θ1 in opposite directions with respect to the straight line A1. As a result, the two laser beams LA and LB are refracted in directions away from each other in the ZX plane. At this time, the laser beams LA and LB are not refracted in the YZ plane.Although the laser beams LA and LB partially impinge on the light-shielding member 326-1, the laser beam LA passes at a rear side away from the light-shielding member 326-1 in the Y-axis direction in the ZX plane, and the laser beam LB passes at a front side away from the light-shielding member 326-1 in a direction opposite to the Y-axis direction in the ZX plane.

[0042] The laser beams LA and LB output from the beam pitch changing unit 32-1 are arranged in a state shown in Fig. 5 as arrangement state C2 at position R2. Dotted ellipses in arrangement state C2 indicate the positions of the laser beams LA and LB in arrangement state C1. As in Fig. As shown in Figure 5, the laser beam LA and the laser beam LB travel the same distance in opposite directions in the X-axis direction.

[0043] Returning to Fig. 4, a beam distance between the laser beams LA and LB output from the beam distance changing unit 32-1 in the X-axis direction is denoted by ΔP1-2x, and a beam distance between them in the Y-axis direction is denoted by ΔP1-2y. In the example of Fig. 4, the beam pitch ΔP1-2x between the laser beams LA and LB output from the beam pitch changing unit 32-1 in the X-axis direction is greater than the beam pitch ΔP1-1x between the laser beams LA and LB that have not yet entered the beam pitch changing unit 32-1. Meanwhile, the beam pitch ΔP1-2y between the laser beams LA and LB output from the beam realignment unit 32-1 in the Y-axis direction is equal to the beam pitch ΔP1-1y between the laser beams LA and LB that have not yet entered the beam realignment unit 32-1.

[0044] A beam pitch in the X-axis direction between the two laser beams LA and LB entering the beam pitch changing unit 32-2 is denoted by ΔP2-1x, and a beam pitch between them in the Y-axis direction is denoted by ΔP2-1y. Note that the beam pitch ΔP2-1x in the X-axis direction is equal to ΔP1-2x, and the beam pitch ΔP2-1y in the Y-axis direction is equal to ΔP1-2y.

[0045] Such two laser beams LA and LB enter the beam pitch changing unit 32-2. The laser beam LA enters the transmission plate 322-2, and the laser beam LB enters the transmission plate 323-2. The laser beams LA and LB are refracted when they enter the transmission plate 322-2 and the transmission plate 323-2, respectively. As in the beam pitch changing unit 32-1, the laser beams LA and LB appear to be refracted in the YZ plane, which is a direction in which the incident angles are provided. Furthermore, the laser beams LA and LB appear to travel in straight lines in the ZX plane, which is a direction in which no incident angle is provided. Furthermore, the two transmission plates 322-2 and 323-2 are inclined by the same angle θ2 with respect to the straight line A2 in opposite directions. As a result, the laser beams LA and LB are not refracted in the ZX plane.At this time, the two laser beams LA and LB are refracted in the YZ plane in a direction in which the two laser beams LA and LB approach each other. Although the laser beams LA and LB partially collide with the light-shielding member 326-2, the laser beam LA passes at a rear side away from the light-shielding member 326-2 in the X-axis direction in the YZ plane, and the laser beam LB passes at a front side away from the light-shielding member 326-2 in a direction opposite to the X-axis direction in the YZ plane. As a result, the two laser beams LA and LB are output from the beam pitch changing unit 32-2 such that a beam pitch in the X-axis direction between the two laser beams LA and LB is ΔP2-2x, and a beam pitch between them in the Y-axis direction is ΔP2-2y. In the example of . Fig. 4, the beam spacing ΔP2-2x is equal to the beam spacing ΔP2-1x in the X-axis direction between the two laser beams LA and LB that have not yet entered the beam spacing changing unit 32-2. The beam spacing ΔP2-2y is smaller than the beam spacing ΔP2-1y between the two laser beams LA and LB that have not yet entered the beam spacing changing unit 32-2.

[0046] The laser beams LA and LB output from the beam pitch changing unit 32-2 are in a Fig. 5 at position R3 in the arrangement state C3. Dotted ellipses in the arrangement state C3 indicate the positions of the laser beams LA and LB in the arrangement state C2. As in Fig. As shown in Figure 5, the laser beams LA and LB travel the same distance in opposite directions in the Y-axis direction, and lie on the X-axis.

[0047] As described above, the two elliptical laser beams LA and LB extending in the Y-axis direction and arranged at a distance in the Y-axis direction, as shown in the arrangement state C1, pass through the two beam spacing changing units 32-1 and 32-2, such that the laser beams LA and LB are arranged at a distance in the X-axis direction, as indicated in the arrangement state C3. That is, the laser beams LA and LB can be rearranged by the beam spacing changing units 32-1 and 32-2.

[0048] When the beam qualities of the laser beams LA and LB differ between the X-axis direction and the Y-axis direction, it is possible to rearrange the laser beams LA and LB as described above, thereby changing the beam diameter and divergence angle of the laser beam L into which the laser beams LA and LB have been combined.

[0049] It is known that beam quality is represented by the product of beam diameter and divergence angle. Beam quality indicates that the smaller the value obtained above, the better the quality of the laser beams LA and LB.

[0050] The beam diameter of a single laser beam can be obtained as a Gaussian beam diameter as described above. A beam diameter determined from the energy distribution formed by the multiple laser beams LA and LB can be used as the beam diameter of the laser beam into which the laser beams LA and LB are combined. There are several definitions of beam diameter. Herein, a beam diameter is understood to be a diameter that provides a predetermined percentage of the energy of the laser beam. When a beam diameter is defined in this way, the beam diameter of the laser beam into which the laser beams LA and LB are combined varies depending on the arrangement of the multiple laser beams LA and LB. As a result, the beam quality changes.

[0051] A case where the multiple laser beams LA and LB in the arrangement state C1 of Fig. 5, that is, a case where the two laser beams LA and LB arranged in the Y-axis direction are combined, is compared with a case where the plural laser beams LA and LB are combined in the arrangement state C3, that is, a case where the two laser beams LA and LB arranged in the X-axis direction are combined. The two laser beams LA and LB having an elliptical shape, which are narrower in the X-axis direction than in the Y-axis direction, are arranged with a pitch in the Y-axis direction in the arrangement state C1, and with a pitch in the X-axis direction in the arrangement state C3. The beam diameters of the laser beams LA and LB in the Y-axis direction are larger than their beam diameters in the X-axis direction. It can therefore be assumed that their beam quality in the Y-axis direction is worse than their beam quality in the X-axis direction.Furthermore, in a case where a region of the beam containing a predetermined percentage of the total energy is considered to provide the beam diameter, the closer the distance between the laser beams LA and LB, the smaller the beam diameter. Considering these findings, the beam quality in the arrangement state C3, in which the laser beams LA and LB are aligned in the X-axis direction, is considered to be better than in the arrangement state C1, in which the laser beams LA and LB are arranged with a distance in the Y-axis direction. For this reason, the two laser beams LA and LB are arranged in . Fig. 4 is realigned by means of the two beam spacing changing units 32-1 and 32-2 such that the arrangement state is changed from the arrangement state C1 to the arrangement state C3.

[0052] Note that the beam pitch changing units 32-1 and 32-2 can change the beam pitches in different directions, and the inclination angles of the beam pitch changing units 32-1 and 32-2 can also be set to any desired angle. As described above, because the shapes of the laser beams LA and LB in the XY plane are unequal (directional) with respect to the X-axis and the Y-axis, the degrees of displacement of the beam positions in the X-axis direction and the Y-axis direction are adjusted based on the shapes so that the numerical aperture of the laser beam L, into which the plurality of laser beams LA and LB have been combined, is substantially the same in the X-axis direction and the Y-axis direction.The reason why the numerical aperture of the laser beam L should be substantially the same in the X-axis direction and the Y-axis direction is that the exit numerical aperture NA_out of the transmission fiber 40 depends on a larger entrance numerical aperture NA_in.

[0053] The relationship between the inclination angles of the transmission plates 322-1, 322-2, 323-1, and 323-3 and the beam pitches is obtained in advance through experimentation. In this way, the inclination angles of the transmission plates 322-1, 322-2, 323-1, and 323-3 can be determined such that a laser beam obtained by combining the two laser beams LA and LB output from the beam pitch changing unit 32-2 has the desired beam quality.

[0054] Based on the above findings regarding beam quality, it is possible to obtain the best beam quality by overlapping the plurality of laser beams LA and LB such that the laser beams LA and LB are aligned with each other. However, there is a case where a reflected laser beam, which is the laser beam L emitted from the machining head 50 and reflected from the workpiece 61, returns to the laser oscillator 20 with a distribution centered on the optical axis of the transmission fiber 40. Considering such a case, in the first embodiment, the light-shielding members 326-1 and 326-2 are arranged at positions corresponding to the optical axis of the transmission fiber 40 on the output sides of the beam pitch changing units 32-1 and 32-2, respectively, from which output sides the laser beams LA and LB exit.Because the light-shielding components 326-1 and 326-2 are arranged in this way, the multiple laser beams LA and LB cannot overlap in a suitable manner. That is, there is a limit to reducing the distance between the two laser beams LA and LB. In the presence of the light-shielding components 326-1 and 326-2, a beam pitch that minimizes the beam quality of the two laser beams LA and LB is obtained. When the two laser beams LA and LB enter the input end of the transmission fiber 40 via the condensing optical system 33 at a beam pitch that minimizes the beam quality, the acceptance angle of the transmission fiber 40 becomes a minimum value. That is, the input numerical aperture NA_in of the transmission fiber 40 is minimized.

[0055] Note that to minimize the beam quality of the two laser beams LA and LB, the multiple laser beams LA and LB must be arranged symmetrically with respect to the extension of the optical axis of the transmission fiber 40. This is because if the two laser beams LA and LB are not arranged symmetrically with respect to the extension of the optical axis of the transmission fiber 40, one of the two laser beams LA and LB will have a larger incidence angle than the other. Since the numerical output aperture NA_out of the transmission fiber 40 depends on a larger numerical input aperture NA_in, it is necessary to reduce the numerical input aperture NA_in of the transmission fiber 40 to reduce the numerical output aperture NA_out of the transmission fiber 40.To reduce the input numerical aperture NA_in of the transmission fiber 40, it is necessary for the laser beam to enter the transmission fiber 40 as far as possible from the extension of the optical axis of the transmission fiber 40. Then, the input numerical aperture NA_in of the transmission fiber 40 is minimized when the two laser beams LA and LB are arranged such that the output loss of the two laser beams LA and LB caused by the blockage at the light-shielding members 326-1 and 326-2 is 10% or less, and the two laser beams LA and LB are arranged with spatial distributions or spatial arrangements that are brought closest to each other and are symmetrical with respect to the extension of the optical axis of the transmission fiber 40.

[0056] As described above, not all of the laser beam L that enters the transmission fiber 40 is transmitted by total internal reflection. The laser beam L transmitted by the transmission fiber 40 through total internal reflection is limited to the laser beam L that enters the transmission fiber 40 at an angle equal to or smaller than the maximum acceptance angle of the transmission fiber 40. The laser beam L that enters the transmission fiber 40 at an angle greater than the maximum acceptance angle of the transmission fiber 40 is not transmitted by the transmission fiber 40 and becomes radiated light, resulting in losses. At the maximum acceptance angle of the transmission fiber 40, the input numerical aperture NA_in of the transmission fiber 40 is maximized.

[0057] As described above, the rotation angles of the transmission plates 322-1, 322-2, 323-1, and 323-2 of the beam pitch changing units 32-1 and 32-2 of the numerical aperture changing device 30 are adjusted to enable the input numerical aperture NA_in of the transmission fiber 40 to be changed between the minimum value and the maximum value. That is, under the condition that the input numerical aperture should be between the minimum value and the maximum value, the rotation angles of the transmission plates 322-1, 322-2, 323-1, and 323-2 are adjusted to enable the beam quality, and specifically, the beam diameter or divergence angle of the laser beam L into which the multiple laser beams LA and LB have been combined, to be changed.

[0058] Here, limitations may be imposed on the operation of the beam spacing changing units 32-1 and 32-2 such that the numerical input aperture NA_in does not exceed the maximum value of the numerical input aperture of the transmission fiber 40.

[0059] In addition, as in Fig. 2, the output numerical aperture NA_out at the output end of the transmission fiber 40 is changed according to the input numerical aperture NA_in at the input end of the transmission fiber 40. That is, the output numerical aperture NA_out of the transmission fiber 40 can be changed in the same way as the input numerical aperture NA_in. As described above, the numerical aperture changing device 30 in the first embodiment can greatly change the input numerical aperture NA_in between the above-described minimum and maximum values. Thus, the variation range of the output numerical aperture NA_out can also be greatly changed according to the input numerical aperture NA_in.

[0060] Note that the above description was made of the numerical aperture changing device 30 having the two beam pitch changing units 32-1 and 32-2, but this is merely an example. In a case where the beam characteristics of the laser beams LA and LB emitted from the laser oscillators 20A and 20B differ between the X-axis direction and the Y-axis direction, the numerical aperture changing device 30 only needs to have two or more beam pitch changing units. However, if the beam characteristics of the laser beams LA and LB emitted from the laser oscillators 20A and 20B are not directional (directed) in the X-axis direction and the Y-axis direction, the numerical aperture changing device 30 may have a single beam pitch changing unit.In addition, although the rotation shafts 324-1 and 325-1 of the beam pitch changing unit 32-1 are perpendicular to the rotation shafts 324-2 and 325-2 of the beam pitch changing unit 32-2, this is also only an example. The rotational waves 324-1 and 325-1 of the beam pitch changing unit 32-1 and the rotational waves 324-2 and 325-2 of the beam pitch changing unit 32-2 may extend in any direction, provided that the rotational waves 324-1 and 325-1 and the rotational waves 324-2 and 325-2 are perpendicular to the optical axis of the transmission fiber 40 and the direction of the rotational waves 324-1 and 325-1 is different from the direction of the rotational waves 324-2 and 325-2.

[0061] Furthermore, the rotational positions of the beam realignment units 321-1 and 321-2, i.e., the inclinations of the transmission plates 322-1, 322-2, 323-1, and 323-2, can be controlled in any desired manner. Alternatively, preset angles can be stored such that the transmission plates 322-1, 322-2, 323-1, and 323-2 are rotated by the preset angles according to commands from the controller 70.

[0062] The numerical aperture changing device 30 of the first embodiment includes the plurality of beam pitch changing units 32-1 and 32-2. The beam pitch changing units 32-1 and 32-2 rearrange the plurality of laser beams LA and LB and change the input numerical aperture NA_in of the transmission fiber 40 when the plurality of rearranged laser beams LA and LB are condensed to enter the transmission fiber 40. The plurality of beam pitch changing units 32-1 and 32-2 include the light shielding members 326-1 and 326-2, respectively. The light shielding members 326-1 and 326-2 are provided on sides closer to the transmission fiber 40 with respect to the beam pitch changing units 32-1 and 32-2, respectively, and are provided in regions including the extension of the optical axis of the transmission fiber 40.As a result, a reflected laser beam, which is a laser beam reflected from the workpiece 61 and returning to the laser oscillator 20 with a distribution centered on the optical axis of the transmission fiber 40, can be blocked without being transmitted to the laser oscillator 20. That is, it is possible to both control the output numerical aperture NA_out of the transmission fiber 40 and prevent the failure of the laser oscillator 20 due to the reflected laser beam. Furthermore, even if the volume of the laser beam reflected from the workpiece 61 is large, it is possible to cause the laser oscillator 20 to operate without failure.

[0063] Furthermore, the beam pitch changing unit 32-1 includes the two transmission plates 322-1 and 323-1 and the rotation mechanisms. The transmission plates 322-1 and 323-1 are rotatable about the rotation shafts 324-1 and 325-1, respectively. The rotation mechanisms drive and rotate the transmission plates 322-1 and 323-1 about the rotation shafts 324-1 and 325-1, respectively, to achieve the desired inclinations. Furthermore, the beam pitch changing unit 32-2 includes the two transmission plates 322-2 and 323-2 and the rotation mechanisms. The transmission plates 322-2 and 323-2 are rotatable about the rotation shafts 324-2 and 325-2, respectively. The rotation mechanisms operate and rotate the transmission plates 322-2 and 323-2 about the rotation shafts 324-2 and 325-2, respectively, in such a way that the desired inclinations are achieved.Furthermore, the laser beam machine 1 includes the control unit 70, which controls the inclinations of the transmission plates 322-1, 322-2, 323-1, and 323-2 via the rotation mechanisms. The control unit 70 can adjust the beam pitches between the laser beams LA and LB by adjusting the inclinations of the two transmission plates 322-1 and 323-1 of the beam pitch changing unit 32-1 and the inclinations of the two transmission plates 322-2 and 323-2 of the beam pitch changing unit 32-2 to predetermined angles. That is, it is possible to control the input numerical aperture NA_in of the transmission fiber 40 between the minimum value and the maximum value. Furthermore, because the variable range of the input numerical aperture NA_in can be increased, the variable range of the output numerical aperture NA_out can also be increased.

[0064] Furthermore, the plurality of laser beams LA and LB are arranged to be symmetrical with respect to the extension of the optical axis of the transmission fiber 40. That is, the laser oscillators 20A and 20B are arranged to be symmetrical with respect to the extension of the optical axis of the transmission fiber 40. Furthermore, the transmission plates 322-1 and 323-1 are arranged to be symmetrical with respect to the extension of the optical axis of the transmission fiber 40. Thus, the beam quality of the laser beam L including the plurality of laser beams LA and LB can be made symmetrical. Furthermore, even if the plurality of laser beams LA and LB have insufficient beam quality, the laser beams LA and LB can be realigned to improve the beam quality.

[0065] In one example, the control unit 70 described above is implemented by a processing circuit that functions as a circuit that causes a processor to execute software. The processing circuit that causes the software to be executed is, for example, a Fig. Control circuit shown in Figure 6. Fig. Figure 6 is a diagram showing an exemplary hardware configuration of the control device of the laser beam machine according to the first embodiment. A control circuit 100 includes an input unit 101, a processor 102, a memory 103, and an output unit 104.

[0066] The input unit 101 is an interface circuit that receives data from outside the control circuit 100 and provides the data to the processor 102. The output unit 104 is an interface circuit that transmits data from the processor 102 or the memory 103 to outside the control circuit 100. In a case that the processing circuit Fig. 6, the laser oscillator 20, the numerical aperture changing device 30, the machining head 50, and the machining table 60 are implemented by the processor 102, which reads and executes programs for controlling the laser oscillator 20, the numerical aperture changing device 30, the machining head 50, and the machining table 60. The programs are stored in the memory 103. The processor can output data such as a calculation result to the memory 103 to store the data in the memory 103, or can store the data such as a calculation result in an auxiliary storage device via the volatile memory of the memory 103.

[0067] The processor 102 is a CPU (central processing unit, also referred to as a processor device, arithmetic device, microprocessor, microcomputer, processor, or DSP (digital signal processor). Examples of the memory 103 include non-volatile or volatile semiconductor memories such as RAM (random access memory), ROM (read-only memory), flash memory, EPROM (erasable programmable read-only memory), and EEPROM (registered trademark) (electrically erasable programmable read-only memory), magnetic disk, flexible disk, optical disk, compact disk, mini disk, and DVD (digital versatile disc).

[0068] Fig.6 shows an exemplary hardware for use in a case where the control unit 70 is implemented as the processor 102 and the memory 103 is implemented as a general-purpose processor and a general-purpose memory, respectively. The control unit 70 may be implemented as a dedicated hardware circuit. A processing circuit as the dedicated hardware circuit is a single circuit, a parallel-programmed processor, an ASIC (application-specific integrated circuit), an FPGA (field-programmable gate array), or a combination thereof. The constituent elements described above may be implemented by a combination of the control circuit 100 and the dedicated hardware circuit.

[0069] The configurations implemented in the above embodiments show examples, and it is possible to combine the configurations with other known technology, and it is also possible to partially omit or modify the configurations without departing from the scope of the present disclosure. List of reference symbols 1 laser beam machine 10 Laser device 20, 20A, 20B laser oscillator 30 Device for changing the numerical aperture 31 Beam spacing changer 32-1, 32-2 Beam spacing change unit 33 condensing optical system 40 transmission fibers 41 core 42 Wrapping 50 machining heads 51 transmitting optical system 60 machining table 61 Workpiece 70 Control unit 100 control circuit 101 Input unit 102 processor 103 storage 104 Output unit 321-1, 321-2 Beam Realignment Unit 322-1, 322-2, 323-1, 323-2 transmission plate 324-1, 324-2, 325-1, 325-2 rotary shaft 326-1, 326-2 Light-shielding component A1, A2 straight line L, LA, LB laser beam QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] JP 2017-506769

[0004]

Claims

[1] A numerical aperture changing device for realigning spatial distributions or spatial positions of a plurality of laser beams incident from a laser oscillator, and for condensing the plurality of realigned laser beams for entry of the beams into a transmission fiber, the numerical aperture changing device comprising: a light-shielding member provided in an extension of the optical axis of the transmission fiber, the light-shielding member blocking a reflected laser beam, the reflected laser beam being a laser beam traveling from the transmission fiber to the laser oscillator. [2] The numerical aperture changing device according to claim 1, wherein the light shielding member has a size such that the output loss of the plurality of laser beams is 10% or less when the spatial distributions or spatial positions of the plurality of incident laser beams are brought closest to each other in the numerical aperture changing device. [3] The numerical aperture changing device according to claim 1 or 2, wherein the light shielding member is arranged such that the output loss of the plurality of laser beams is 10% or less when the spatial distributions or spatial positions of the plurality of incident laser beams are brought closest to each other in the numerical aperture changing device. [4] The numerical aperture changing device according to any one of claims 1 to 3, wherein the light shielding member is formed of a material that absorbs or reflects the reflected laser beam. [5] A numerical aperture changing device according to claim 4, wherein the light shielding member includes a cooling mechanism. [6] A numerical aperture changing device according to any one of claims 1 to 5, comprising: a plurality of beam pitch changing units for changing beam pitches between the plurality of incident laser beams, wherein the light shielding member is provided for each of the plurality of beam pitch changing units and is arranged on a side closer to the transmission fiber with respect to each of the beam pitch changing units. [7] A numerical aperture changing device according to claim 6, further comprising: a control device for controlling the operation of the plurality of beam spacing changing units, wherein each of the plurality of beam spacing change units includes: a beam realignment unit having a plurality of transmission plates arranged at predetermined intervals, the plurality of transmission plates transmitting the laser beams; and a rotation mechanism for rotating each of the transmission plates around a rotation shaft, and the control device controls the rotation mechanism such that the plurality of laser beams enter the plurality of transmission plates at predetermined angles. [8] The numerical aperture changing device according to claim 7, wherein the plurality of laser beams are incident on the numerical aperture changing device symmetrically with respect to the extension of the optical axis of the transmission fiber, and the plurality of transmission plates are arranged symmetrically with respect to the extension of the optical axis of the transmission fiber. [9] Laser device comprising: the numerical aperture changing device according to any one of claims 1 to 8; and the laser oscillator for causing the plurality of laser beams to enter the numerical aperture changing device. [10] Laser beam machine, comprising: the laser device according to claim 9; a transmission fiber for transmitting the plurality of laser beams from the laser device; and a processing head for irradiating a workpiece with the plurality of laser beams from the transmission fiber.

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