JP2020060725A - Laser oscillator and laser processing apparatus using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve both suppression of output loss of laser light emitted from a transmission fiber and maintenance of beam quality. A laser oscillator 100 reduces a plurality of laser modules 120, which are laser light sources that emit laser light LB, and the laser light LB by a predetermined magnification, and condenses them toward an incident end 200a of a transmission fiber 200. It is provided with at least a condensing optical unit 140. The condensing optical unit 140 has a condensing lens 142 which is a variable focal length lens configured to transmit an incident laser beam LB to form an image at a predetermined focal point and to change the focal length. .. [Selection diagram] Fig. 2

Description

  The present invention relates to a laser oscillator and a laser processing device using the same.

  2. Description of the Related Art Conventionally, there is known a laser processing device that laser-processes a work at a remote place by using a transmission fiber. In such a laser processing apparatus, a laser oscillator is provided inside, and the laser light emitted from the laser oscillator propagates in the core of the transmission fiber and reaches the workpiece from the laser light emission head connected to the transmission fiber. It is irradiated toward. Further, when the laser light is incident on the transmission fiber, the beam diameter of the laser light is reduced to a spot diameter that can be accommodated in the core of the transmission fiber by a condenser lens provided in the laser oscillator.

  On the other hand, in such a laser processing device, when the spot diameter of the laser light becomes large at the incident end of the transmission fiber where the laser light is incident and the laser light of a predetermined light amount or more leaks from the core, the laser light is finally output. The output of the generated laser light may be reduced, or in extreme cases, the transmission fiber may be burnt or the like. Therefore, it is necessary to surely make the laser light emitted from the laser oscillator enter the core of the transmission fiber.

  Therefore, in Patent Document 1, a transparent flat plate is disposed between the condenser lens and the transmission fiber, and the tilt angle of the transparent flat plate is changed to adjust the focus position of the laser light at the incident end of the transmission fiber. A configuration is disclosed.

  Further, in Patent Document 2, a plurality of laser diode modules and a grating for combining the laser beams emitted from the respective laser diode modules into a spectral beam are provided, and the measurement result by a temperature sensor attached to the laser diode module is shown. Based on this, a configuration is disclosed in which the incident angle of the laser beam incident on the grating is changed to reduce the output loss when the laser beam combined with the spectrum beam is incident on the transmission fiber.

Japanese Patent Laid-Open No. 05-060935 JP, 2016-181643, A

  By the way, in a laser beam used for laser processing, a beam quality represented by a beam parameter product (hereinafter referred to as BPP) is important together with its optical output. For example, as BPP increases, the divergence angle of laser light increases.

  However, if the laser light is excessively narrowed down in order to fit the laser light in the core, the divergence angle of the laser light emitted from the emission end of the transmission fiber becomes large, and laser light with a high optical density is generated. In some cases, the required laser cutting or the like could not be performed properly.

  Further, with the conventional configurations disclosed in Patent Documents 1 and 2, although the focus position of the laser light at the incident end of the transmission fiber can be adjusted, for example, the divergence angle cannot be adjusted.

  The present invention has been made in view of the above points, and an object thereof is to suppress an output loss of a laser beam emitted from a transmission fiber, and to use a laser oscillator and a laser beam having good beam quality. It is to provide a laser processing apparatus.

  In order to achieve the above object, a laser device according to the present invention is a laser light source that emits a laser beam, and a condensing optical system that condenses the laser beam at a predetermined magnification and condenses it toward an incident end of a transmission fiber. A laser oscillator including at least a unit, wherein the condensing optical unit has an optical component configured to form an incident laser beam at a predetermined focus and change a focal length. It is characterized by being

  With this configuration, it is possible to suppress the output loss of the laser light emitted from the emission end of the transmission fiber. In addition, the beam quality of the laser light can be improved.

  Further, a laser processing apparatus according to the present invention is attached to the above laser oscillator, a transmission fiber that is connected to the laser oscillator and transmits the laser light emitted from the laser oscillator, and an emission end of the transmission fiber. And a laser beam emitting head.

  With this configuration, it is possible to suppress the output loss of the laser light emitted from the laser light emitting head through the transmission fiber, maintain the beam quality, and maintain good processing quality in processing the work.

  According to the laser oscillator of the present invention, it is possible to suppress the output loss of the laser light emitted from the transmission fiber and improve the beam quality.

  Further, according to the laser processing apparatus of the present invention, good processing quality can be maintained in processing a work.

It is a schematic diagram which shows the structure of the laser processing apparatus which concerns on one Embodiment of this invention. It is a schematic diagram which shows the internal structure of a condensing optical unit. It is a flowchart which shows the inspection and adjustment procedure of a laser oscillator. It is a schematic diagram which shows the optical coupling state of a laser beam and a transmission fiber. It is a figure which shows the relationship between the laser beam output loss in the incident end of a transmission fiber, and the beam parameter product of the laser beam radiate | emitted from the emission end of a transmission fiber. It is a schematic diagram which shows the internal structure of the condensing optical unit which concerns on a modification.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The description of the preferred embodiments below is merely exemplary in nature and is not intended to limit the present invention, its application, or its application.

(Embodiment)
[Configuration of laser processing equipment]
FIG. 1 shows a schematic diagram of the configuration of a laser processing apparatus according to this embodiment. In the following description, the traveling direction of the laser beam LB toward the condensing optical unit 140 is the Z direction, the arrangement direction of the plurality of laser modules 120 is the Y direction, and the direction orthogonal to the Z direction and the Y direction is the X direction. May be called.

  The laser processing apparatus 1000 includes a laser oscillator 100, a transmission fiber 200, a laser light emitting head 300, a control unit 400, a power supply 500, and a display unit 600. The end of the transmission fiber 200 from which the laser light LB is incident from the laser oscillator 100 (hereinafter, simply referred to as the incident end 200a (see FIG. 2). The end of the transmission fiber 200 from which the laser light LB is emitted is hereinafter referred to as The emitting end 200b (see FIG. 2)) is housed in the housing 110.

  The laser oscillator 100 includes a plurality of laser modules 120 functioning as a laser light source, a beam combiner 130, and a condensing optical unit 140. The laser module 120 is composed of a plurality of laser diodes or laser diode arrays that emit laser beams of different wavelengths, and the laser light whose wavelengths have been combined in the laser module 120 are emitted from each laser module 120.

  The beam combiner 130 combines the laser light emitted from each of the plurality of laser modules 120 into one laser light (hereinafter referred to as laser light LB) and emits the combined laser light to the condensing optical unit 140. Specifically, the optical axes of the respective laser lights are brought close to or coincide with each other, and they are coupled so that their optical axes are parallel to each other.

  The condensing optical unit 140 is a casing 141 and an optical component arranged inside the casing 141, which is an optical component configured to form an image of the incident laser light at a predetermined focus and change the focal length. And a lens 142 (see FIG. 2). The structure and function of each part of the condensing optical unit 140 will be described later.

  With the laser oscillator 100 having such a configuration, it is possible to obtain the high-power laser processing apparatus 1000 in which the output of the laser light LB exceeds several kW. Further, the laser oscillator 100 is supplied with power from a power supply 500 described later to perform laser oscillation, and the laser light LB is emitted from the emission end 200b of the transmission fiber 200. In the present embodiment, four laser modules 120 are mounted on the laser oscillator 100, but the number of laser modules 120 is not limited to this. The number of laser modules 120 mounted can be appropriately changed according to the output specifications required for the laser processing apparatus 1000 and the output specifications of the individual laser modules 120.

  The transmission fiber 200 is optically coupled to the condensing lens 142 (see FIG. 2) of the condensing optical unit 140, and the laser light LB received from the laser oscillator 100 via the condensing lens 142 is directed to the laser light emitting head 300. To transmit. Further, the transmission fiber 200 has a core 201 for transmitting the laser light LB to the axis and a clad 202 coaxially provided with the core 201 on the outer peripheral side of the core 201 (see FIG. 2). . The core 201 and the clad 202 are each made of quartz, but the clad 202 has a refractive index lower than that of the core 201. The clad 202 has a function of confining the laser light LB in the core 201. have. The outer peripheral surface of the clad 202 is covered with a film (not shown) for protecting the transmission fiber 200 from mechanical damage.

  The laser light emitting head 300 emits the laser light LB transmitted by the transmission fiber 200 toward the outside. Further, the laser light emitting head 300 has optical components (not shown) such as a collimator lens, a condenser lens, and protective glass inside. For example, in the laser processing apparatus 1000 shown in FIG. 1, the laser beam LB is emitted toward the workpiece W, which is a processing target object arranged at a predetermined position. By doing so, the work W is laser-processed.

  The control unit 400 controls the laser oscillation of the laser oscillator 100. Specifically, the laser oscillation control of each laser module 120 is performed by supplying a control signal such as an output voltage and an ON time to a power source 500 connected to the laser oscillator 100. It is also possible to individually control laser oscillation for each laser module 120. For example, the laser oscillation output, the ON time, and the like may be different for each laser module 120. Further, the control unit 400 controls a driving mechanism (not shown) attached to the condensing optical unit 140 so that the focal length of the condensing lens 142 described later has a desired value. Further, the control unit 400 has a storage unit 410 formed of a storage device such as a memory, and the storage unit 410 stores laser processing conditions, operation programs for processing, and the like. Further, as will be described later, the storage unit 410 stores the allowable range of the output loss of the laser light LB and the allowable range of the BPP which is the beam parameter product representing the beam quality of the laser light LB output from the transmission fiber 200. ing. The controller 400 may also control the operation of a manipulator (not shown) to which the laser light emitting head 300 is attached. The laser oscillator 100 may be configured by the plurality of laser modules 120, the beam combiner 130, the condensing optical unit 140, and the controller 400.

  As described above, the power supply 500 supplies power for performing laser oscillation to the laser oscillator 100, specifically, each of the plurality of laser modules 120. The electric power supplied to each laser module 120 may be different according to a command from the control unit 400. Further, the power source 500 may supply power to a movable part of the laser processing apparatus 1000, for example, the above manipulator, or another power source (not shown) for the movable part of the laser processing apparatus 1000. ) May supply electric power.

  The display unit 600 is configured to display the abnormal portion of the laser oscillator 100 determined by the control unit 400. Data other than the above may be displayed on the display unit 600. For example, the output of the laser beam LB may be displayed. It is also possible to display the processing parameter and the actual measurement value at the time of laser processing at the same time. The display unit 600 usually includes a display device such as a cathode ray tube or a liquid crystal display.

[Internal structure of condensing optical unit]
FIG. 2 shows a schematic diagram of the internal configuration of the condensing optical unit. For convenience of description, the laser light emitting head 300 connected to the emitting end 200b of the transmission fiber 200 is not shown.

  The condensing optical unit 140 has a housing 141 and a condensing lens 142 arranged in the housing 141. The condenser lens 142 condenses the laser light LB that has entered the housing 141, and the condensed laser light LB has a beam diameter reduced by a predetermined magnification. The condensed laser light LB is incident on the incident end 200a of the transmission fiber 200, propagates in the core 201, and is emitted to the outside from the emitting end 200b. A connector (not shown) made of quartz may be provided in contact with the incident end 200a. By providing the connector, irregular reflection of the laser light LB at the incident end 200a can be prevented. Note that other optical components such as a collimator lens and a partial reflection mirror that directs a part of the laser light LB in different directions may be provided inside the condensing optical unit 140. However, for convenience of description, illustration and detailed description of these optical components are omitted.

  The condenser lens 142 forms an image of the incident laser light LB at a predetermined focus, in this case, the vicinity of the incident end 200a. Further, the condenser lens 142 is a so-called variable focal length lens configured so that the focal length can be continuously changed, and a known configuration can be applied. For example, air or a liquid having a predetermined refractive index is enclosed in an elastically deformable transparent member, and the pressure applied to the air or the liquid is changed to deform the transparent member, that is, the fluid pressure that changes the curvature of the curved surface of the lens. It may be a drive type lens, or a so-called electrically driven type lens in which a lens body having the same structure or elastically deformable is deformed by a piezoelectric actuator, an electrostatic induction type actuator or the like to change its curvature. Further, it may be a lens utilizing the electro-optical effect. A drive mechanism for changing the curvature of the condenser lens 142 is not shown.

  As shown in FIG. 2 (a), the incident angle 2θa1 at which the laser beam LB condensed by the condenser lens 142 is incident on the incident end 200a of the transmission fiber 200 is larger than a predetermined value, and at the incident end 200a. When the spot diameter 2r of the laser light LB is smaller than the diameter D of the core 201 (hereinafter referred to as the core diameter D), or as shown in FIG. 7B, the spot diameter 2r of the laser light LB at the incident end 200a. Is larger than the core diameter D of the core 201, various problems occur as described later.

  In such a case, as shown in FIG. 6C, the focal length of the condenser lens 142 is changed and the laser light LB is incident on the incident end 200a of the transmission fiber 200 at the incident angle 2θa and the incident end 200a. The spot diameter 2r of the laser beam LB at is adjusted to a desired value.

[Laser oscillator inspection and adjustment procedure]
FIG. 3 shows the procedure for checking and adjusting the laser oscillator. First, the output of the laser light LB incident on the condensing optical unit 140 is measured (step S1). This measurement can be performed by various methods. For example, in the condensing optical unit 140, a partial reflection mirror (not shown) is provided between an entrance through which the laser light LB enters the condensing optical unit 140 and the condensing lens 142, and is reflected by the partial reflection mirror. A part of the generated laser light LB may be received by a laser light output monitor (not shown), and the output of the laser light LB may be evaluated based on the received light signal. Further, each of the laser modules 120 may be provided with a laser light output monitor (not shown), and the output of the laser light LB may be evaluated based on the light reception signals of these laser light output monitors. Alternatively, the output of the laser light LB may be directly measured before attaching the transmission fiber 200 to the condensing optical unit 140.

  Next, the output of the laser light LB emitted from the transmission fiber 200 and the BPP are measured (step S2). This measurement may be performed with the laser light emitting head 300 removed from the transmission fiber 200, or with the laser light emitting head 300 attached to the transmission fiber 200. However, in the latter case, it is necessary to correct the measured value in consideration of the output loss in the laser light emitting head 300 and the change in the beam shape. The measurement results in steps S1 and S2 are stored in the storage unit 410 of the control unit 400. The correction of the measured value is performed by the control unit 400.

  The output of the laser beam LB is measured by a laser beam output monitor (not shown), and the BPP is obtained by measuring the emission angle 2θb of the laser beam LB using the same laser beam output monitor. This point will be described.

  In general, the BPP representing the beam quality of the laser light is a value of half the spot diameter 2r (hereinafter, referred to as a focusing radius r) and a value of half the divergence angle 2θ, as shown in Expression (1). It is represented by the product of the beam divergence angle and the divergence half-angle θ. For example, mm · mrad is used as the unit of BPP.

  BPP = r × θ (1)

  When transmitting and emitting the laser light LB using the transmission fiber 200, if the BPP of the laser light LB at the incident end 200a of the transmission fiber 200 is BPP1, then BPP1 is expressed by equation (2).

  BPP1 = r × θa (2)

  Here, θa is the half angle of the incident angle 2θa (hereinafter referred to as the incident half angle θa).

  The BPP1 as the BPP of the laser light LB at the incident end 200a of the transmission fiber 200 is maintained at a predetermined value if there is no loss on the optical path regardless of the type and arrangement of the optical system used for shaping the laser light. Is the value to be set. That is, since the BPP of the laser light LB is maintained at the incident end 200a of the transmission fiber 200 even though it passes through the condenser lens 142 and the like, the BPP1 is incident on the condenser optical unit 140 and transmitted through the condenser lens 142. It is equivalent to the BPP of the laser beam LB before being processed.

  On the other hand, when the laser light LB is transmitted through the transmission fiber 200, the emission end 200b of the transmission fiber 200 becomes a virtual focus. Therefore, assuming that the BPP of the laser light LB at the emitting end 200b is BPP2, BPP2 is expressed by equation (3).

  BPP2 = D / 2 × θb (3)

  Here, θb (hereinafter referred to as “emission half-angle θb”) is half the value of the emission angle 2θb, and when the angle is very small, for example, except when it is several degrees or less, the incident angle 2θa and the emission angle 2θb are equal to each other. Generally agrees. D is the core diameter of the transmission fiber 200.

  As is clear from the above, the BPP obtained in step S2 corresponds to the BPP2 represented by the equation (3). Since the core diameter D of the transmission fiber 200 is known in advance, BPP2, which is the BPP of the laser light LB at the emitting end 200b, can be derived by measuring the emitting angle 2θb.

  Next, based on the measurement results in steps S1 and S2, the output loss of the laser light LB in the transmission fiber 200 is obtained, and it is determined whether or not this value is equal to or less than a predetermined value (step S3). The output loss is derived by the control unit 400 based on the value stored in the storage unit 410. Further, the control unit 400 makes the determination in step S3 based on the allowable range of the output loss stored in the storage unit 410 in advance. The output loss is a value obtained by dividing the difference between the measurement result in step S1 and the measurement result in step S2 by the measurement result in step S1, but the difference value may be used as it is.

  If the determination result in step S3 is affirmative, the process proceeds to step S4, and whether the BPP (= BPP2) of the laser light LB emitted from the emission end 200b of the transmission fiber 200 measured in step S2 is equal to or less than a predetermined value. It is determined whether or not (step S4). Further, the control unit 400 makes the determination in step S4 based on the allowable range of the BPP stored in the storage unit 410 in advance.

  On the other hand, if the output loss is larger than the predetermined value and the result of the determination in step S3 is negative, the spot diameter 2r of the laser light LB at the incident end 200a of the transmission fiber 200 is larger than the core diameter D of the core 201. Therefore, (i) the focal length of the condenser lens 142 is increased, and the distance from the incident end 200a of the transmission fiber 200 is increased so that the condenser lens 142 is separated from the incident end 200a. 2r is reduced, or (ii) the incident angle 2θa of the laser light LB is increased by the condenser lens 142 to shorten the focal length and reduce the spot diameter 2r (step S5). Returning to step S2, the output of the laser light LB and the BPP are measured again. It should be noted that a series of processes from step S3 to step S5 and step S2 and returning to step S3 is continuously performed until the determination result in step S3 becomes affirmative. However, if the output loss is larger than the predetermined value even after repeating several times and the determination result in step S3 remains negative, the process is interrupted and the transmission fiber 200 is removed from the condensing optical unit 140, The light collection optical unit 140 and the transmission fiber 200 may be inspected. At this time, the components in the condensing optical unit 140 and the transmission fiber 200 may be replaced as needed.

  If the BPP of the laser light LB emitted from the transmission fiber 200 is less than or equal to the predetermined value and the result of the determination in step S4 is affirmative, it can be determined that the focal length of the condenser lens 142 need not be changed. This completes the inspection and adjustment procedure. On the other hand, if the BPP of the laser light LB emitted from the transmission fiber 200 is larger than the predetermined value and the determination result in step S4 is negative, the beam quality of the laser light LB emitted from the transmission fiber 200 is degraded. Since it can be determined that the laser beam LB is present, the focal length of the condenser lens 142 is increased to reduce the incident angle 2θa of the laser light LB (step S6). By doing so, the emission angle 2θb of the laser beam LB can be reduced and BPP2 can be reduced. Returning to step S2, the output of the laser light LB and the BPP are measured again. It should be noted that a series of processing from step S4 to step S6 and step S2 and returning to step S4 is continuously performed until the determination result in step S4 becomes affirmative. However, if the BPP of the laser light LB emitted from the transmission fiber 200 is larger than a predetermined value even after several repetitions, and the determination result in step S4 remains negative, the process is interrupted and the light collection is performed. The transmission fiber 200 may be removed from the optical unit 140 and the condensing optical unit 140 and the transmission fiber 200 may be inspected. At this time, the components in the condensing optical unit 140 and the transmission fiber 200 may be replaced as needed.

  In steps S5 and S6, the focal length of the condensing lens 142, specifically, the curvature of the focusing lens 142 and the like is, as described above, based on the control signal from the control unit 400, via a drive mechanism (not shown). Be changed.

  The procedure shown in FIG. 3 is periodically performed according to the laser oscillation integrated time of the laser oscillator 100, the operation integrated time of the laser processing apparatus 1000, and the like. If the stability of the laser module 120 or the power source 500 has been confirmed in advance by experiments or the like, the measurement in step S1 may be performed less frequently than other steps. For example, the procedure shown in FIG. 3 may be performed at least once among several times. In that case, the measurement result may be stored in the storage unit 410, and the stored value may be used in other processing. Alternatively, the output setting value of the laser beam LB may be used as it is as the measurement value in step S1. In that case, in step S2, instead of the output loss, the output measurement value of the laser beam LB may be used as it is, and in step S3, it may be determined whether or not the measurement value is equal to or less than a predetermined value.

[Effects, etc.]
As described above, the laser oscillator 100 according to the present embodiment reduces a plurality of laser modules 120, which are laser light sources that emit the laser light LB, and the laser light LB at a predetermined magnification, and then enters the transmission fiber 200. At least the condensing optical unit 140 that condenses toward the end 200a is provided.

  The condensing optical unit 140 has a condensing lens 142 which is an optical component configured to form the incident laser light LB at a predetermined focus and change the focal length. Further, in this embodiment, the condenser lens 142 is a variable focal length lens.

  By configuring the laser oscillator 100 in this way, it is possible to suppress the output loss of the laser light LB at the incident end 200a of the transmission fiber 200. Further, the beam quality of the laser light LB emitted from the emission end 200b can be made good. This will be further described.

  As described above, the BPP1 as the BPP of the laser light LB at the incident end 200a of the transmission fiber 200 has no loss on the optical path regardless of the type or arrangement of the optical system used for shaping the laser light. It is maintained at a predetermined value. Therefore, for example, when the laser light LB is narrowed down so as to obtain a smaller spot diameter 2r, the divergence half-angle θb is increased. More specifically, if the laser light LB is simply narrowed down at the entrance end 200a of the transmission fiber 200, then the divergence half-angle θb becomes large at the exit end 200b. As described above, such a state is not preferable when high-density laser light is required for laser cutting or the like. In some cases, desired laser processing may not be performed.

  Here, the optical coupling state between the laser light and the transmission fiber will be described in detail with reference to FIG. It is assumed that BPP1, which is the BPP of the laser light LB that has entered the condenser optical unit 140 and has not yet passed through the condenser lens 142, is 4.0, and the core diameter D of the transmission fiber 200 is 0.1 mm. The focal length of the condenser lens 142 is fixed, and the spot diameter (beam diameter) of the laser light LB entering the condenser lens 142 is assumed to be constant.

  As shown in FIG. 4A, when the spot diameter 2r of the laser light LB at the incident end 200a of the transmission fiber 200 becomes the core diameter D of the transmission fiber 200, there is no output loss at the incident end 200a and the laser The optical coupling state between the light LB and the transmission fiber 200 becomes ideal. In the present embodiment, the emission half angle θb of the laser light LB at the emission end 200b of the transmission fiber 200 in this case is 80 mrad. Therefore, as is clear from the equation (3), BPP2 which is BPP at the emission end 200b becomes 4.0 (= 0.1 / 2 × 80), and the condensing lens 142 which is the BPP of the original laser light is set. It has the same value as BPP1 of the laser light LB before being transmitted. That is, the beam quality of the laser light LB incident on the condensing optical unit 140 is maintained.

  On the other hand, as shown in FIG. 4B, the laser beam LB is adjusted so that the spot diameter 2r of the laser beam LB at the incident end 200a of the transmission fiber 200 becomes 0.08 mm smaller than the core diameter D of the transmission fiber 200. When the optical parameter of the condenser lens 142 for converging and condensing is selected, the spot diameter 2r of the laser light LB at the incident end 200a is sufficiently smaller than the core diameter D of the transmission fiber 200, so that the laser light LB If the arrangement of the condenser lens 142 is adjusted so that the center of the spot and the center of the core 201 overlap, the output loss of the laser light LB at the incident end 200a is eliminated. On the other hand, the emission half-angle θb1 of the laser beam LB at the emission end 200b of the transmission fiber 200 is widened to the opposite of 100 mrad. Therefore. BPP2 at the exit end 200b is 5.0 (= 0.1 / 2 × 100), and the beam quality is degraded at the exit end 200b.

  Further, as shown in FIG. 4C, the condenser lens 142 so that the spot diameter 2r of the laser light LB at the incident end 200a of the transmission fiber 200 is 0.12 mm larger than the core diameter D of the transmission fiber 200. When the optical parameter of is selected, the incident half angle θa2 of the laser beam LB at the incident end 200a is 66.7 mrad. Further, since the spot diameter 2r of the laser light LB at the incident end 200a is sufficiently larger than the core diameter D of the transmission fiber 200 and the incident angle 2θa2 and the outgoing angle 2θb2 are the same value, BPP2 is 3.3 (0 .1 / 2 × 66.7), and the beam quality of the laser light LB emitted from the transmission fiber 200 is improved. On the other hand, since the spot diameter 2r of the laser light LB becomes larger than the core diameter D at the incident end 200a of the transmission fiber 200, an output loss occurs at the incident end 200a. In particular, the output loss in this case depends on the energy density at the spot diameter of the laser light LB at the incident end 200a, but is 10% or more of the original output, so that the desired laser light output can be obtained. In addition, the risk of burnout of the transmission fiber 200 increases.

  On the other hand, according to the present embodiment, the condensing lens 142 is configured as a variable focal length lens, and the condensing lens 142 of the variable focal length lens is used to make the laser light LB enter the incident end 200a of the transmission fiber 200. By changing the focal length of the condenser lens 140 according to the emission state of the laser light LB, it is possible to suppress the output loss of the laser light LB emitted from the transmission fiber 200 and prevent the transmission fiber 200 from burning. Moreover, the beam quality represented by BPP can be maintained at a desired value.

  The laser oscillator 100 further includes a control unit 400 for adjusting the focal length of the condenser lens 142 to a predetermined value. In addition, the control unit 400 causes the output loss of the laser light LB transmitted to the transmission fiber 200 and the BPP (= BPP2) of the laser light LB emitted from the emission end 200b of the transmission fiber 200 to fall within predetermined ranges. It is configured to adjust the focal length of the condenser lens 142.

  FIG. 5 shows the relationship between the laser light output loss at the entrance end of the transmission fiber and the beam parameter product BPP2 of the laser light emitted from the exit end of the transmission fiber.

  As described above, as the spot diameter 2r of the laser light LB at the incident end 200a of the transmission fiber 200 is increased, the BPP2 becomes lower, that is, improved. On the other hand, when the core diameter D of the transmission fiber 200 is exceeded, an output loss starts to occur, so the output loss and the BPP2 have a relationship as shown in FIG. The data and the allowable range of the output loss of the laser beam LB and the allowable range of the BPP2 are stored in the storage unit 410.

  For example, assuming that the allowable range of BPP2 of the laser beam LB emitted from the transmission fiber 200 is 4 or less, more preferably 3 or less, and the allowable range of the output loss at the incident end 200a of the transmission fiber 200 is 1% or less, The control unit 400 changes the focal length of the condenser lens 142 as a variable focal length lens via a drive mechanism (not shown) so that the emission characteristics of the laser light LB are matched with the region surrounded by the diagonal line of 5. More specifically, this makes it possible to both suppress the output loss of the laser light LB and maintain the beam quality.

  The energy density at the spot diameter of the laser light LB differs in the degree to which the energy density of the laser light LB is concentrated on the center side of the spot diameter depending on the characteristics of the laser light. According to the characteristics of the energy density of the laser light, the incident laser light is imaged at a predetermined focal point, and the focal length of the condenser lens 142, which is an optical component configured to change the focal length, is changed. Then, it is preferable to appropriately adjust the size of the spot diameter 2r of the laser light LB with respect to the core diameter D at the incident end 200a of the transmission fiber 200.

  Thereby, while suppressing the output loss of the laser light LB at the incident end 200a, the BPP2 at the emitting end 200b of the transmission fiber 200 is made small, and the beam quality of the laser light LB emitted from the transmission fiber 200 is further improved. Can be done.

  Further, in the laser oscillator 100 incorporated in the laser processing apparatus 1000, the inside of the condensing optical unit 140 including the condensing lens 142 is reduced by operating the laser processing apparatus 1000 for a long time due to vibration or temperature change of the surrounding environment. There is a case where the optical system and the transmission fiber 200 are displaced from each other, and the optical coupling efficiency between the two becomes smaller than the initial value. The same phenomenon may occur when heat is generated in each part due to the laser beam LB for a long period of time.

  On the other hand, according to the present embodiment, the output of the laser light LB emitted from the transmission fiber 200 and the BPP are periodically measured, and the focal length of the condenser lens 142 can be changed based on these measured values. Therefore, it is possible to prevent the above optical coupling efficiency from being lowered, and to suppress the output loss of the laser light LB and maintain the beam quality at the same time.

  Further, when the above optical coupling efficiency decreases, in the conventional configuration, the transmission fiber 200 is removed from the condensing optical unit 140, and the positions of the condensing lens 142 and the like and the position of the incident end 200a of the transmission fiber 200 are readjusted. Although it was necessary, according to the present embodiment, by changing the focal length of the condenser lens 142, it is not necessary to remove the transmission fiber 200 or readjust the position of each part.

  The laser oscillator 100 further includes a beam combiner 130 that combines and emits the plurality of laser beams emitted from the plurality of laser modules 120, and the condensing optical unit 140 includes the laser emitted from the beam combiner 130. The light is reduced at a predetermined magnification and condensed.

  By configuring the laser oscillator 100 in this way, the output of the laser light LB can be made a high output of several kW or more.

  Further, the laser processing apparatus 1000 according to the present embodiment includes a laser oscillator 100, a transmission fiber 200 that is connected to the laser oscillator 100 and transmits the laser light LB emitted from the laser oscillator 100, and an emission end 200 b of the transmission fiber 200. And a laser beam emitting head 300 attached to the.

  By configuring the laser processing apparatus 1000 in this way, the work W can be processed using the laser light LB having a good beam quality in which output loss is suppressed, so that the processing quality can be kept good. In addition, when an increase in output loss of the laser light LB or a decrease in BPP is observed in a periodic inspection or the like, the focal length of the condenser lens 142 is changed according to the output loss of the laser light LB or the degree of change in BPP. Therefore, it is possible to maintain the characteristics of the laser beam LB by minimizing the replacement of parts. As a result, downtime of the laser processing apparatus 1000 can be reduced and an increase in operating cost can be suppressed.

<Modification>
FIG. 6 is a schematic diagram of the internal configuration of the condensing optical unit according to this modification. In this modified example, the same parts as those in the embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

  The configuration shown in FIG. 6 is different from the configuration shown in FIG. 2 in that a variable curvature mirror 143 is arranged in place of the condenser lens 142 in the condenser optical unit 140.

  The variable curvature mirror 143, which is an optical component configured to form an incident laser beam at a predetermined focus and change the focal length, can continuously change the curvature of the surface via a driving mechanism (not shown). Is configured. Further, the laser light LB incident on the variable curvature mirror 143 is reflected by the surface of the variable curvature mirror 143 and imaged at a predetermined focus. The principle of changing the curvature of the variable curvature mirror 143 is similar to that of the condenser lens 142, and the curvature is changed by, for example, fluid pressure driving or electric driving. As a result, the focal length of the variable curvature mirror 143 can be changed.

  Therefore, for example, as shown in FIG. 6, when the spot diameter 2r of the laser light LB is larger than the core diameter D of the core 201 at the incident end 200a of the transmission fiber 200 and the output loss is increased, the light is emitted. Based on the characteristic measurement result of the laser light LB emitted from the end 200b, the curvature of the variable curvature mirror 143 can be changed so that the spot diameter 2r of the laser light LB can be properly contained in the core 201. By doing so, it is possible to both suppress the output loss of the laser light LB and maintain the beam quality.

(Other embodiments)
Although the laser light source is configured using the four laser modules 120 in the above-described embodiment including the modification, the invention is not particularly limited to this. For example, one laser light source that emits laser light having a single wavelength may be used. In that case, the beam combiner 130 shown in FIG. 1 is omitted.

  Further, in order to change the optical coupling between the laser light LB incident on the condensing optical unit 140 and the transmission fiber 200, the incident laser light is imaged at a predetermined focus and the focal length can be changed. Although an example in which the condenser lens 142 which is a variable focal length lens and the variable curvature mirror 143 are used as the optical components described above is shown, the present invention is not particularly limited to this and other configurations may be adopted. For example, a plurality of condenser lenses having different focal lengths are arranged in the condenser optical unit 140, and an appropriate condenser lens is selected from these condenser lenses based on the characteristic measurement result of the laser light LB emitted from the emission end 200b. A lens may be selected and placed on the optical axis of the laser beam LB. With this configuration, the condensing optical unit 140 becomes large, but since the output loss and the beam quality of the laser light LB can be adjusted only by exchanging the condensing lens arranged at a predetermined position, the control is simplified. It In order to finely adjust the optical coupling efficiency, it is preferable to dispose, for example, three or more lenses.

  If it is difficult to properly adjust the optical coupling between the laser beam LB and the transmission fiber 200 only by adjusting the focal lengths of the condenser lens 142 and the variable curvature mirror 143, the condenser lens 142 and the variable curvature mirror 143 are used. A moving mechanism (not shown) that can move in the X direction, which is the optical axis direction of the laser light LB, may be provided. Alternatively, a moving mechanism (not shown) that can move the position of the incident end 200a of the transmission fiber 200 in the X direction may be provided.

  INDUSTRIAL APPLICABILITY The laser oscillator according to the present invention can suppress the output loss of the laser light emitted from the emission end of the transmission fiber and maintain the beam quality at a good value, and thus is useful in application to a laser processing apparatus.

100 laser oscillator 110 housing 120 laser module 130 beam combiner 140 condensing optical unit 142 condensing lens (variable focal length lens)
143 variable curvature mirror 200 transmission fiber 200a incident end 200b emitting end 300 laser light emitting head 400 control unit 500 power supply 600 display unit 1000 laser processing device LB laser light W work

Claims (6)

A laser oscillator comprising at least a laser light source for emitting laser light, and a condensing optical unit for condensing the laser light at a predetermined magnification to condense it toward an incident end of a transmission fiber,
The laser oscillator, wherein the condensing optical unit has an optical component configured to form an incident laser beam at a predetermined focus and change a focal length. The laser oscillator according to claim 1,
The laser oscillator, wherein the optical component is a variable focal length lens. The laser oscillator according to claim 1,
The laser oscillator, wherein the optical component is a variable curvature mirror. The laser oscillator according to any one of claims 1 to 3,
The laser light source is composed of a plurality of laser modules each emitting a laser beam,
Further comprising a beam combiner for combining and emitting a plurality of laser beams emitted from the plurality of laser modules,
The laser oscillator, wherein the condensing optical unit reduces the laser light emitted from the beam combiner at a predetermined magnification and condenses the laser light. The laser oscillator according to any one of claims 1 to 4,
Further comprising a control unit for adjusting the focal length of the optical component to a predetermined value,
The control unit adjusts the focal length of the optical component so that the output loss of the laser light transmitted to the transmission fiber and the beam parameter product of the laser light emitted from the emission end of the transmission fiber fall within predetermined ranges. A laser oscillator configured to be tuned. A laser oscillator according to any one of claims 1 to 5,
A transmission fiber connected to the laser oscillator and transmitting the laser light emitted from the laser oscillator,
A laser processing apparatus comprising at least a laser beam emitting head attached to an emitting end of the transmission fiber.

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