Laser oscillator and laser processing apparatus including the same

Abstract

To provide a laser oscillator capable of suppressing output deterioration and beam quality deterioration of a high-output laser beam guided by an optical fiber.SOLUTION: The laser oscillator 90 includes a laser module 10 having a laser light source that emits a first laser beam LB1, optical fibers 80, and a condensing optical unit 40. The condensing optical unit 40 includes a condenser lens 42 and a birefringent device 43 disposed between the condenser lens 42 and the incident ends 80A of the optical fibers 80. The first laser beam LB1 transmitted through the birefringent device 43 is separated into a first sub-beam LB11 and a second sub-beam LB12, and each of the first sub-beam LB11 and the second sub-beam LB12 is incident on the core 81 of the optical fibre 80 as a laser beam LB.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a laser oscillator and a laser processing device including the same. [Background technology]

[0002] In recent years, laser processing technology has been widely put to practical use, in which a laser beam is used to process a workpiece. In this case, by using a semiconductor laser element (also called a direct diode laser (DDL)) as a laser light source provided in a laser oscillator, the laser light source can be made smaller and more efficient (see, for example, Patent Document 1). In addition, so-called remote processing, in which a laser beam is guided through an optical fiber to laser process a workpiece installed at a location remote from the laser oscillator, is widely used (see, for example, Patent Documents 2 and 3).

[0003] In recent years, there has been an increasing demand for laser processing of fine patterns in metal processing and the like, and laser processing techniques using, for example, ultraviolet laser beams have been used. Also, optical fibers for guiding ultraviolet laser beams have been developed (see, for example, Patent Documents 4 and 5). On the other hand, it is known that quartz parts deteriorate when irradiated with an ultraviolet laser beam for a long period of time (see, for example, Non-Patent Document 1). Optical fibers are usually made of quartz, and therefore, when a high-power ultraviolet laser beam is guided through them, there is a risk that their optical characteristics will deteriorate over time. Patent Documents 4 and 5 disclose configurations for preventing deterioration due to an ultraviolet laser beam. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 5981855 [Patent Document 2] Special Publication No. 2017-506769 [Patent Document 3] Patent No. 7394289 [Patent Document 4] Patent No. 3393120 [Patent Document 5] Patent No. 4210156 [Non-patent literature]

[0005] [Non-Patent Document 1] Takahashi, Hashiguchi, ''Durability of quartz for ArF excimer laser light and its effect on imaging performance'', Optics, Optical Society of Japan, March 2005, Vol. 34, No. 3, pp. 148-150 Summary of the Invention [Problem to be solved by the invention]

[0006] In recent years, there has been a demand for laser welding and the like on materials with low light absorption rate for infrared light, such as copper, etc. For this reason, laser processing techniques have been developed that use laser beams having visible wavelengths such as green and blue (hereinafter sometimes referred to as visible laser beams) instead of conventional infrared laser beams.

[0007] However, when a high-power visible laser beam is guided through an optical fiber for laser processing, the power density of the visible laser beam in the optical fiber is in the range of several tens of MW to 100 MW / cm. 2 When such a high-power-density laser beam is guided for a long period of time, the optical characteristics of the optical fiber may deteriorate, even for a visible laser beam. Such deterioration in the optical characteristics of the optical fiber may lead to a decrease in the output power and beam quality of the visible laser beam. Similar problems may also occur when the wavelength range of the laser beam is in the infrared region.

[0008] The present disclosure has been made in consideration of these points, and its purpose is to provide a laser oscillator and a laser processing device equipped with the same that can suppress a decrease in output and a decrease in beam quality of a high-power laser beam guided by an optical fiber. [Means for solving the problem]

[0009] In order to achieve the above object, the laser oscillator according to the present disclosure is characterized by comprising at least one laser light source or a plurality of laser light sources, a quartz optical fiber having a core and a cladding, a focusing optical system for inputting a first laser beam emitted from the laser light source into the optical fiber, and a birefringent element arranged between the focusing optical system and the input end of the optical fiber.

[0010] The laser processing device according to the present disclosure is characterized by including at least the laser oscillator and a laser head that receives the laser beam guided by the optical fiber and irradiates the laser beam toward a workpiece. [Effects of the Invention]

[0011] According to the present disclosure, it is possible to suppress a decrease in output power and a decrease in beam quality of a high-power laser beam guided through an optical fiber. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a schematic configuration diagram of a laser processing device according to a first embodiment. [Figure 2] FIG. 2 is a schematic diagram illustrating the configuration of a main part of a laser oscillator. [Figure 3] FIG. 2 is a schematic diagram illustrating the function of a birefringent element. [Figure 4] FIG. 10 is a diagram showing an example of the relationship between the thickness of a birefringent element and the beam separation width. [Figure 5] 1 is an intensity profile of a laser beam at the input end of an optical fiber. [Figure 6] FIG. 10 is a diagram showing the Y-direction distribution of the power density of the laser beam at the incident end of the optical fiber. [Figure 7] 10 is a comparative intensity profile of a laser beam at the input end of an optical fiber. [Figure 8] FIG. 10 is a diagram showing the Y-direction distribution of the power density of a laser beam at the incident end of an optical fiber for comparison. [Figure 9]FIG. 10 is a schematic diagram showing the change in the unidirectional distribution of the power density of the laser beam. [Figure 10] 10 is an intensity profile of a laser beam at the incident end of an optical fiber according to Modification 1. [Figure 11] 10 is a diagram showing the Y-direction distribution of the power density of a laser beam at the incident end of an optical fiber according to Modification 1. FIG. [Figure 12] FIG. 10 is a schematic configuration diagram of a main part of a laser oscillator according to Modification 2. [Figure 13] 10 is an intensity profile of a laser beam at the incident end of an optical fiber according to Modification 3. [Figure 14] 1 is a schematic half-sectional view of an optical fiber according to a second embodiment. [Figure 15A] FIG. 2 is a perspective view of the input side of an optical fiber. [Figure 15B] FIG. 2 is a perspective view of the incident side of the optical fiber when the holder is removed. [Figure 16] 10 is a flowchart showing the alignment adjustment procedure for the optical system according to the second embodiment. [Figure 17A] 10 is an intensity profile of a laser beam at the incident end of an optical fiber immediately after shipping, according to Modification 4. [Figure 17B] 10 is an intensity profile of a laser beam at the incident end of an optical fiber after long-term use according to Modification 4. [Figure 18] FIG. 10 is a schematic configuration diagram of a laser processing device according to a third embodiment. [Figure 19] FIG. 2 is a schematic diagram of the inside of a beam combining unit. [Figure 20] 10 shows the intensity profile of a laser beam at the input end of an optical fiber before and after the birefringent element is attached. [Figure 21] 10 is another laser beam intensity profile at the input end of an optical fiber before and after the birefringent element is attached. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Note that the following description of the preferred embodiments is merely exemplary in nature and is not intended to limit the present disclosure, its applications, or its uses. (Embodiment 1) [Configuration of laser processing equipment] FIG. 1 is a schematic diagram showing the configuration of a laser processing apparatus according to this embodiment. In the following description, the traveling direction of a first laser beam LB1 (described later) emitted from the optical path changing unit 20 toward the focusing optical unit 40 may be referred to as the Z direction. The Z direction is also the optical axis direction of the laser beam LB inside the fourth housing 41 of the focusing optical unit 40. The main direction of the first laser beam LB1 in the optical path changing unit 20 may be referred to as the Y direction. A direction perpendicular to the Z direction and the Y direction may be referred to as the X direction. The Z direction may be referred to as the first direction, the Y direction as the second direction, and the X direction as the third direction.

[0014] In this specification, "orthogonal," "parallel," or "same" means that the two objects are orthogonal, parallel, or the same, taking into account the assembly tolerances and processing tolerances of the laser processing apparatus 200 and its components, and does not mean that the objects being compared are orthogonal, parallel, or the same in the strict sense.

[0015] The laser processing device 200 includes a fifth housing 50, a laser oscillator 90, and a laser head 100. Except for a control unit 60, a power supply 70, and a part of an optical fiber 80, the laser oscillator 90 is housed inside the fifth housing 50.

[0016] The laser oscillator 90 includes one laser module 10 , an optical path changing unit 20 , a focusing optical unit 40 , a control unit 60 , a power supply 70 , and an optical fiber 80 .

[0017] The laser module 10 has a laser light source (not shown) inside the first housing 11. The laser light source in this embodiment is composed of a plurality of laser diodes or one or a plurality of laser diode bars. In other words, the laser light source has a plurality of emitters that emit laser beams. The laser beams emitted from the plurality of emitters are combined within the laser module 10 and emitted from the laser module 10 as a linearly polarized first laser beam LB1 (see FIG. 2).

[0018] The optical path changing unit 20 changes the optical path of the first laser beam LB1 in the Z direction and makes it incident on the focusing optical unit 40 (see FIG. 2). The configuration of the optical path changing unit 20 will be described later.

[0019] The focusing optical unit 40 focuses the first laser beam LB1 emitted from the optical path changing unit 20 toward the incident end 80A of the optical fiber 80 (see FIG. 2). The focusing optical unit 40 also splits the first laser beam LB1 into two beams and makes them incident on the core 81 of the optical fiber 80. The configuration of the focusing optical unit 40 will be described later.

[0020] The optical fiber 80 has at least a core 81 and a clad 82 (see FIG. 2). Both the core 81 and the clad 82 are made of quartz, and their optical properties are adjusted so that the refractive index of the core 81 is higher than that of the clad 82. The core 81 is provided at the axial center of the optical fiber 80, and functions as an optical waveguide that guides the laser beam LB incident from the focusing optical unit 40 to the laser head 100. The clad 82 is provided so as to surround the outer periphery of the core 81, and functions as an optical confinement layer that confines the laser beam LB inside the core 81. The outer periphery of the clad 82 is covered with an exterior material 87 (see FIG. 14) that mechanically protects the core 81 and the clad 82.

[0021] The control unit 60 has one or more CPUs (Central Processing Units) and storage units (neither of which are shown), and controls the laser oscillation of the laser oscillator 90. Specifically, the control unit 60 controls the laser oscillation of the laser module 10 by supplying control signals such as output voltage and on-time to the power supply 70. For example, the control unit 60 controls the laser oscillation output and on-time of the laser module 10. The control unit 60 also controls the power supplied from the power supply 70 to the laser light source included in the laser module 10 so that the output of the laser beam LB reaches a predetermined target value.

[0022] As described above, the power supply 70 supplies power for laser oscillation to the laser module 10. The power supply 70 may also supply power to a moving part of the laser processing apparatus 200, such as the robot described above. Note that power may be supplied to the moving part of the laser processing apparatus 200 from a separate power supply (not shown).

[0023] The laser head 100 irradiates the laser beam LB guided by the optical fiber 80 toward the outside. For example, in the laser processing apparatus 200 shown in Fig. 1, the laser beam LB is emitted toward a workpiece W, which is an object to be processed and placed at a predetermined position. In this manner, the workpiece W is laser processed.

[0024] [Laser oscillator configuration] Fig. 2 is a schematic diagram of the main part of a laser oscillator, and Fig. 3 is a schematic diagram for explaining the function of a birefringent element.

[0025] 2, the light exit port 21A provided in the second housing 21 of the optical path changing unit 20 communicates with the light entrance port 41A provided in the fourth housing 41 of the light collecting optical unit 40. In addition, the optical fiber 80 is connected to a first receptacle 45 provided in the light exit port 41B. An entrance end 80A of the optical fiber 80 is connected to a transmitting surface of the laser beam LB of a quartz block 83 held in the first receptacle 45 by fusion or the like.

[0026] The optical path changing unit 20 has a rise-up mirror and a reflecting mirror 22 (not shown) inside the second housing 21. Note that other components may also be arranged inside the second housing 21. The first laser beam LB1 emitted from the laser module 10 is reflected by the rise-up mirror and its traveling direction is changed to the Y direction. Furthermore, the first laser beam LB1 is reflected by the reflecting mirror 22 arranged near the light exit port 21A and its traveling direction is changed to the Z direction.

[0027] The focusing optical unit 40 has a focusing lens 42, a birefringent element 43, and a quarter-wave plate (phase difference canceling element) 44 inside a fourth housing 41. Note that other components may also be arranged inside the second housing 21. A set of optical components including the focusing lens 42 may be referred to as a focusing optical system. The first laser beam LB1 incident from the light entrance port 41A is focused by the focusing lens 42 and then enters the birefringent element 43.

[0028] 2 and 3, the birefringent element 43 is a plate-shaped optical component made of quartz. The material of the birefringent element 43 is not particularly limited to this, and may be, for example, lithium niobate (LiNbO), and is preferably a uniaxial birefringent crystal.

[0029] An anti-reflection coating AR is applied to each of the transmitting surfaces of the first laser beam LB1 in the birefringent element 43, that is, the incident surface of the first laser beam LB1 and the output surface of the laser beam LB, which will be described later. By applying the anti-reflection coating AR, unwanted reflection of the first laser beam LB1 and the laser beam LB in the birefringent element 43 can be prevented, and the output loss of the laser beam LB until it enters the optical fiber 80 can be reduced.

[0030] Quartz crystal, which is a uniaxial crystal, has optical anisotropy. Therefore, as shown in FIG. 3, the first laser beam LB1 incident on the birefringent element 43 is separated into an ordinary ray and an extraordinary ray. The ordinary ray and the extraordinary ray emitted from the birefringent element 43 travel parallel to each other in the Z direction while maintaining the beam separation width d. In this embodiment, the ordinary ray is divided into the first sub-beam LB 11The extraordinary ray is called the second sub-beam LB 12 Also, the first sub-beam LB 11 and the second sub-beam LB 12 These are collectively referred to as the laser beam LB. In this embodiment, the first sub-beam LB 11 and the second sub-beam LB 12 The birefringent element 43 is arranged so that the first sub-beam LB and the second sub-beam LB are separated in the Y direction. 11 and the second sub-beam LB 12 The direction of separation of the second sub-beam LB from the first sub-beam LB is determined by rotating the birefringent element 43 in a virtual plane including the X and Y directions. 12 is s-polarized, the first sub-beam LB 11 is p-polarized light, but is not limited to this.

[0031] The thickness of the birefringent element 43 is t, and the first sub-beam LB 11 The refractive index of the birefringent element 43 with respect to n о , second sub-beam LB 12 The refractive index of the birefringent element 43 with respect to n e Then, the beam separation width d is expressed by the relationship shown in equation (1).

[0032] d=t×(n о 2 -n e 2 ) / (n о 2 +n e 2 ) ···(1) FIG. 4 is a diagram showing an example of the relationship between the thickness of a birefringent element and the beam separation width. In this case, the wavelength of the first laser beam LB1 is 405 nm. As is clear from FIG. 4, if the beam separation width d is desired to be 30 μm, the thickness t of the birefringent element 43 needs to be approximately 5 mm. Note that if the wavelength of the first laser beam LB1 changes, the relationship shown in FIG. 4, i.e., the rate of change of the beam separation width d with respect to the thickness t, also changes. Furthermore, if the material of the birefringent element 43 is changed, the rate of change of the beam separation width d with respect to the thickness t also changes. For example, if the material of the birefringent element 43 is lithium niobate, the rate of change of the beam separation width d with respect to the thickness t will be greater than in the example shown in FIG. 4.

[0033] The first sub-beam LB emitted from the birefringent element 43 11 and the second sub-beam LB 12 and have the same linear polarization as the first laser beam LB1. 11 and the second sub-beam LB 12 When the first sub-beam LB and the second sub-beam LB pass through the quarter-wave plate 44, they are converted from linearly polarized light to circularly polarized light. 11 and second sub-beam LB 12 In each of these, the phase difference of the vibration vector of the electric field is cancelled.

[0034] FIG. 5 shows the intensity profile of the laser beam at the incident end of the optical fiber. FIG. 6 shows the Y-direction distribution of the power density of the laser beam at the incident end of the optical fiber. FIG. 7 shows the intensity profile of the laser beam at the incident end of the optical fiber for comparison. FIG. 8 shows the Y-direction distribution of the power density of the laser beam at the incident end of the optical fiber for comparison. Note that the power density of the laser beam LB shown in FIGS. 6 and 8 is a relative value after normalization. Furthermore, all of the profiles shown in FIGS. 4 to 8 are profiles on an imaginary plane LP. The imaginary plane LP is an imaginary plane that includes the incident end 80A of the optical fiber 80 and intersects with the traveling direction of the first laser beam LB1, in this case the Z direction.

[0035] In the laser oscillator 90 of this embodiment, as shown in FIG. 5, a first sub-beam LB 11 and the second sub-beam LB 12 The first sub-beam LB passes through the imaginary plane LP so as to be completely separated in the Y direction and to fit into the core 81 of the optical fiber 80. Therefore, as shown in FIG. 6, the power density of the laser beam LB has two peaks separated in the Y direction. The power densities of the two peaks are each 1.2 or less. In addition, the first sub-beam LB 11 and the second sub-beam LB 12 and , respectively, are rectangular or elliptical intensity profiles on the imaginary plane LP, with the X direction as the major axis and the Y direction as the minor axis. In the examples shown in Figures 5 and 6, the thickness t of the birefringent element 43 is 6 mm, and the beam separation width d is about 40 µm.

[0036] Now, consider the case where the birefringent element 43 and the quarter-wave plate 44 are removed from the focusing optical unit 40. In this case, as shown in FIG. 7, the first laser beam LB1 transmitted through the focusing lens 42 passes directly through the imaginary plane LP. Therefore, as shown in FIG. 8, the power density of the laser beam LB, in this case the first laser beam LB1, has one peak, and the power density is about 2.0. Furthermore, the first laser beam LB1 has a rectangular or elliptical intensity profile on the imaginary plane LP, with the X direction as the major axis and the Y axis as the minor axis.

[0037] That is, as shown in this embodiment, a birefringent element 43 is disposed between the condenser lens 42 and the incident end 80A of the optical fiber 80, and the first laser beam LB1 is converted into a first sub-beam LB 11 and the second sub-beam LB 12 By separating the first laser beam LB1 into the first sub-beam LB2, the power density of the laser beam LB at the incident end 80A of the optical fiber 80 can be reduced to about half of that in the case shown in FIG. 11 and the second sub-beam LB 12 When the beam is split into two, the first sub-beam LB 11 and second sub-beam LB 12The aforementioned beam separation width d, in other words, the thickness t of the birefringent element 43, is set so that both of the beams fit within the core 81 of the optical fiber 80. At the same time, the distance between the condenser lens 42 and the incident end 80A of the optical fiber 80 and the distance between the condenser lens 42 and the birefringent element 43 are also set.

[0038] [Effects, etc.] As described above, the laser oscillator 90 of this embodiment includes at least a laser module 10 having a laser light source and emitting a first laser beam LB1, a quartz optical fiber 80 having a core 81 and a cladding 82, and a focusing optical unit 40.

[0039] The focusing optical unit 40 has at least a focusing lens (focusing optical system) 42 for directing the first laser beam LB1 into the optical fiber 80, and a birefringent element 43 arranged between the focusing lens 42 and the incident end 80A of the optical fiber 80.

[0040] The first laser beam LB1 transmitted through the birefringent element 43 is converted into a first sub-beam LB 11 and the second sub-beam LB 12 The first sub-beam LB 11 and second sub-beam LB 12 are incident on a core 81 of an optical fiber 80 as a laser beam LB.

[0041] As disclosed in Patent Document 3, when a laser beam is focused onto the entrance end of an optical fiber using a focusing lens, the power density of the laser beam at the entrance end has a distribution that peaks at the center. Since damage or deterioration of optical components through which the laser beam passes depends on the power density of the laser beam, it is thought that damage or deterioration is more likely to occur near the axis of core 81 of optical fiber 80 through which the central portion of the laser beam passes.

[0042] On the other hand, according to this embodiment, the first laser beam LB1 emitted from the laser module 10 is divided into the first sub-beam LB 11 and the second sub-beam LB 12and the first sub-beam LB1 are incident on the core 81 of the optical fiber 80. In this way, the laser beam LB can be guided to the optical fiber 80 without reducing the amount of light and with the power density at the incident end 80A of the optical fiber 80 reduced to about half of that of the first laser beam LB1. In particular, as shown in FIGS. 6 and 8, the first sub-beam LB 11 and the second sub-beam LB 12 The power density at the center of each of the first and second laser beams LB1 and LB2 is about half that of the first laser beam LB1. This makes it possible to suppress degradation of the optical characteristics of the optical fiber 80, and to suppress degradation of the output and beam quality of the laser beam LB emitted from the optical fiber 80, even when the output of the first laser beam LB1 reaches about 1 kW to several kW.

[0043] As disclosed in Patent Document 2, a method has been proposed in which a polarizing beam splitter including a half-wave plate and a birefringent plate is placed before the focusing optical system, and the linearly polarized laser beam incident on the polarizing beam splitter is spatially separated and made to enter spatially different positions at the entrance end of the optical fiber.

[0044] Furthermore, if a polarizing beam splitter is not used, the laser beam cannot be sufficiently split unless it is split to a spatially different position in the focusing optical system, and the beam separation width by the focusing optical system must be increased to several mm.

[0045] However, if the birefringent plate is made of quartz, the thickness t of the birefringent plate calculated from equation (1) is expected to exceed 100 mm in order to achieve this separation width.

[0046] Therefore, in both of the above cases, the optical components for splitting the laser beam and inputting it into the optical fiber become large. However, in order to transmit a high-power density laser beam, it is necessary to use optical components made of high-quality quartz. Since such optical components are expensive, increasing the size of the quartz optical components significantly increases the cost of the laser oscillator 90.

[0047] On the other hand, according to the present embodiment, a birefringent element 43 that spatially separates the first laser beam LB1 is disposed between the condenser lens 42 and the incident end 80A of the optical fiber 80. In this manner, the first laser beam LB1 collected by the condenser lens 42 is separated by the birefringent element 43, which makes it possible to prevent the condenser lens 42 and the birefringent element 43 from becoming large. This makes it possible to prevent an increase in the costs of the condenser lens 42 and the birefringent element 43, and ultimately the laser oscillator 90.

[0048] Furthermore, as disclosed in Patent Documents 4 and 5, by improving the material and structure of the optical fiber, it is possible to suppress damage and deterioration of the optical fiber, for example, when guiding an ultraviolet laser beam. However, in this case, there is a risk that the cost of the optical fiber will increase and that the wavelength range of the laser beam that can be guided will be restricted.

[0049] According to this embodiment, by reducing the power density of the laser beam LB at the incident end 80A of the optical fiber 80, it is possible to guide a high-power density laser beam LB into the optical fiber 80 without imposing any particular restrictions on the material or structure of the optical fiber 80. This makes it possible to prevent an increase in the costs of the optical fiber 80 and, in turn, the laser oscillator 90. In addition, there is no need to impose any restrictions on the wavelength range of the first laser beam LB1.

[0050] The beam separation direction of the first laser beam LB1 is preferably the traveling direction of the first laser beam LB1, in this case, the minor axis direction of the first laser beam LB1 on an imaginary plane LP that intersects with the Z direction. By doing so, the intensity profile of the laser beam LB on the imaginary plane LP, and ultimately at the incident end 80A of the optical fiber 80, can be made closer to a square or a circle. This makes it possible to make the power distribution of the laser beam LB at the incident end 80A of the optical fiber 80 closer to a flatter one, thereby suppressing deterioration in the optical properties of the optical fiber 80 due to damage or deterioration, and suppressing deterioration in the output and beam quality of the laser beam LB emitted from the optical fiber 80.

[0051] A quarter-wave plate (phase difference canceling element) 44 may be further provided between the birefringent element 43 and the incident end 80A of the optical fiber 80.

[0052] As described above, by providing the quarter-wave plate 44, the first sub-beams LB 11 and the second sub-beam LB 12 When the laser beam LB used for processing is linearly polarized, the absorption and reflection characteristics of the laser beam LB vary depending on the polarization direction depending on the material of the workpiece W. For example, in laser cutting, the cutting width may vary depending on the cutting direction, or the cutting surface may be inclined. By providing a quarter-wave plate 44, the first sub-beam LB 11 and the second sub-beam LB 12 By converting the light into circularly polarized light, the influence of the processing direction can be reduced in laser processing. Note that if the influence of the polarization direction is small or absent when laser processing the workpiece W, the installation of the quarter-wave plate 44 can be omitted.

[0053] The birefringent element 43 is made of a uniaxial birefringent crystal material such as quartz or lithium niobate. An antireflection coating AR is applied to the transmitting surface of the birefringent element 43 through which the first laser beam LB1 passes. The application of the antireflection coating AR prevents unwanted reflection of the first laser beam LB1 and the laser beam LB from the birefringent element 43, thereby reducing the output loss of the laser beam LB before it enters the optical fiber 80. By using lithium niobate as the material for the birefringent element 43, the thickness t of the birefringent element 43 can be made thinner than when quartz is used. This shortens the distance from the focusing lens 42 to the incident end 80A of the optical fiber 80, allowing the focusing optical unit 40 to be made more compact.

[0054] The wavelength range of the first laser beam LB1 is preferably a predetermined range from ultraviolet to visible. By making the wavelength range of the first laser beam LB1 shorter, the processing width in laser processing can be narrowed, allowing for fine processing. Furthermore, as described above, materials such as copper, which have low light absorption in the infrared range, can be efficiently laser processed. When a semiconductor laser element such as a laser diode bar is used as the laser light source, the predetermined range is, for example, 380 nm or more and 560 nm or less. When a solid-state laser using a second harmonic generation element or a fourth harmonic generation element is used as the laser light source, the predetermined range is, for example, 240 nm or more and 570 nm or less. The wavelength range of the first laser beam LB1 may be in the infrared range.

[0055] The diameter of the core 81 of the optical fiber 80, i.e., the core diameter, is preferably 400 μm or less. This makes it possible to use commercially available optical fibers 80. When a laser beam LB having a beam diameter suitable for laser processing is emitted from the optical fiber 80, it is more preferable that the core diameter be in the range of approximately 50 μm or more and 100 μm or less.

[0056] The laser processing device 200 according to this embodiment includes at least a laser oscillator 90 and a laser head 100 that receives a laser beam LB guided by an optical fiber 80 and irradiates the workpiece W with the laser beam LB.

[0057] By configuring the laser processing apparatus 200 in this manner, when a laser beam LB of several kW class is emitted from the optical fiber 80, it is possible to suppress deterioration in the optical characteristics of the optical fiber 80, and to suppress deterioration in the output and beam quality of the laser beam LB. This makes it possible to perform stable laser processing using a high-output laser beam LB. It is also possible to suppress deterioration in laser processing quality.

[0058] <Variation 1> Fig. 9 is a schematic diagram showing a case where the unidirectional distribution of the power density of a laser beam is changed. Fig. 10 is an intensity profile of a laser beam at the incident end of an optical fiber according to Modification 1. Fig. 11 is a diagram showing the Y-direction distribution of the power density of a laser beam at the incident end of an optical fiber according to Modification 1. For ease of explanation, in Figs. 9 to 11 and the following drawings, parts similar to those in Embodiment 1 are designated by the same reference numerals, and detailed explanations thereof will be omitted.

[0059] If the power density distribution of the laser beam LB has two peaks as shown in Fig. 6, for example, when laser welding is performed, the shape of the weld bead may have two peaks, which may be undesirable from a processing standpoint. However, in the power density distribution of the laser beam LB shown in Fig. 8, the peak intensity is too strong, which may cause damage or deterioration of the optical fiber 80 described above.

[0060] In order to reduce the peak of the power density of the laser beam LB while maintaining the light intensity of the laser beam LB incident on the core 81 of the optical fiber 80, it is preferable to control the divergence of the laser beam LB so that the beam diameter of the laser beam LB is approximately the same as the core diameter of the core 81. That is, it is preferable to change the intensity profile of the laser beam LB from a power density distribution with a single-peak Gaussian distribution as shown on the left side of FIG. 9 to a power density distribution with a gentle peak, so-called top-hat shape, as shown on the right side of FIG. 9. Note that when changing the intensity profile of the laser beam LB, the area S1 corresponding to the light intensity of the laser beam LB with a Gaussian distribution and the area S2 corresponding to the light intensity of the laser beam LB with a top-hat shape are made equal. Note that the area S1 is the integral value of the Gaussian power density distribution shown on the left side of FIG. 9, and the area S2 (= S1) is the integral value of the top-hat power density distribution shown on the right side of FIG. 9.

[0061] Such a change in the intensity profile of the laser beam LB is achieved by reducing the beam separation width d and 11 and the second sub-beam LB 12This is achieved by increasing the degree of overlap with the beam separation width d. When the beam separation width d is actually reduced, the power density of the laser beam LB is about 1.5 as shown in Fig. 11, and an intensity profile can be obtained having a peak that is about 3 / 4 of the peak of the power density of the laser beam LB shown in Fig. 8.

[0062] According to this modified example, the peak power density of the laser beam LB can be reduced while maintaining the light amount of the laser beam LB incident on the core 81 of the optical fiber 80, thereby suppressing deterioration of the optical properties of the optical fiber 80 due to damage or alteration of the optical fiber 80, and suppressing reduction in the output and beam quality of the laser beam LB.

[0063] <Variation 2> FIG. 12 is a schematic configuration diagram of a main part of a laser oscillator according to the second modification.

[0064] 12 differs from the laser oscillator 90 of the first embodiment shown in Fig. 2 in that a quarter-wave plate (phase difference eliminating element) 23 is provided inside the second housing 21 of the optical path changing unit 20. The laser oscillator 90 also differs from the laser oscillator 90 of the first embodiment shown in Fig. 2 in that the quarter-wave plate 44 in the focusing optical unit 40 is omitted.

[0065] If there is a slight phase difference in the vibration vector of the electric field of the linearly polarized first laser beam LB1, the first sub-beams LB1 are separated by the birefringent element 43 and each have a different polarization state. 11 and the second sub-beam LB 12 There may be a difference in the amount of light.

[0066] According to this modification, the first laser beam LB1 is converted from linearly polarized light to circularly polarized light before it enters the condenser lens 42. In this way, the first laser beam LB1 incident on the birefringent element 43 becomes circularly polarized light, and the first sub-beam LB 11 and the second sub-beam LB 12This allows the power density distribution of the laser beam LB to approach spatial symmetry, thereby suppressing degradation of the beam quality of the laser beam LB.

[0067] 12, the quarter-wave plate 23 is provided in the optical path changing unit 20, but the present invention is not limited to this. For example, the quarter-wave plate 44 may be provided inside the fourth housing 41 of the focusing optical unit 40, on the upstream side of the focusing lens 42. In other words, it is sufficient that the quarter-wave plate is disposed in the optical path of the first laser beam LB1 until it enters the focusing lens 42.

[0068] <Variation 3> FIG. 13 shows the intensity profile of the laser beam at the incident end of the optical fiber according to the third modification.

[0069] Although not shown, the laser oscillator 90 in this modification differs from the laser oscillator 90 in the modification 2 shown in FIG. 12 in that the quarter-wave plate 23 is omitted.

[0070] In this modification, as shown in FIG. 13, the beam split direction of the first laser beam LB1 is set to the first sub-beam LB 11 and second sub-beam LB 12 In this case, the long axis directions of the first laser beam LB1 and the second laser beam LB2 are inclined by 45° from the X direction. In addition, considering that the polarization direction of the first laser beam LB1 is the X direction, the beam separation direction of the first laser beam LB1 is inclined by 45° from the X direction, which is the polarization direction of the first laser beam LB1.

[0071] According to this modification, the first sub-beam LB included in the laser beam LB 11 and second sub-beam LB 12 Therefore, at the incident end 80A of the optical fiber 80, the first sub-beam LB 11 and second sub-beam LB 12The peaks of the power densities of the first sub-beam LB are shifted in both the X and Y directions. 11 and the second sub-beam LB 12 To separate the two, as described above, the birefringent element 43 is rotated 45° from its original position within an imaginary plane including the X and Y directions.

[0072] This makes it possible to make the power density distribution of the laser beam LB smooth at the incident end 80A of the optical fiber 80. Therefore, even if a phase difference occurs in the vibration vector of the electric field of the first laser beam LB1, which is linearly polarized light, it is possible to suppress degradation of the beam quality of the laser beam LB.

[0073] If the polarization state of the laser beam LB affects the accuracy of laser processing, a quarter-wave plate 44 may be provided between the birefringent element 43 and the incident end 80A of the optical fiber 80 as shown in FIG. 2 to polarize the first sub-beam LB. 11 and second sub-beam LB 12 may be converted into circularly polarized light.

[0074] (Embodiment 2) Fig. 14 is a schematic half-sectional view of the optical fiber according to embodiment 2. Fig. 15A is a perspective view of the incident side of the optical fiber, and Fig. 15B is a perspective view of the incident side of the optical fiber when the holder is removed.

[0075] 14 and 15A and 15B differs from the optical fiber 80 shown in Fig. 2 in that an optical component fixing mechanism 84, a rotation mechanism 85, and a holder 86 in which a birefringent element 43 is fitted are attached to the incident side. The optical component fixing mechanism 84 and the holder 86 are connected via the rotation mechanism 85, and the optical component fixing mechanism 84, the rotation mechanism 85, and the holder 86 are an integrated mechanical component that is attached integrally to the optical fiber 80.

[0076] 14, the optical component fixing mechanism 84 is a cylindrical member, and is attached to the outer casing 87 of the optical fiber 80 via a screw mechanism 84A. A quartz block 83 is housed inside the optical component fixing mechanism 84. As described above, the incident end 80A of the optical fiber 80 is connected to the transmitting surface of the quartz block 83 through which the laser beam LB passes by fusion splicing or the like.

[0077] The rotation mechanism 85 is operated from the outside to rotate the holder 86 around the axis of the optical fiber 80, in other words, around the optical axis of the laser beam LB. Furthermore, with the optical fiber 80 attached to the first receptacle 45, the rotation mechanism 85 can be operated from the outside.

[0078] The holder 86 is attached to the rotation mechanism 85 so as to rotate integrally. The birefringent element 43 is fitted into the holder 86. The holder 86 is configured to be able to hold the birefringent element 43 even when the thickness of the birefringent element 43 is changed. By operating the rotation mechanism 85, the birefringent element 43 fitted into the holder 86 rotates around the optical axis of the laser beam LB. In other words, by operating the rotation mechanism 85, the crystal axis direction of the birefringent element 43 relative to the polarization direction of the first laser beam LB1 is rotated, and the first sub-beam LB 11 and the second sub-beam LB 12 The direction of separation from the optical fiber 80 can be changed and adjusted. The holder 86 is detachable from the rotation mechanism 85. That is, with the birefringent element 43 fitted in, the holder 86 can be easily removed from and attached to the optical fiber 80.

[0079] 15B, the birefringent element 43 has a flat portion 43A cut out from the outer circumferential surface. By providing the flat portion 43A, it is possible to easily check how much the birefringent element 43 has been rotated from the initial position.

[0080] The procedure for adjusting the alignment of the optical system in the laser oscillator 90, including the adjustment of the separation direction, will be described below.

[0081] FIG. 16 is a flowchart showing the alignment adjustment procedure for the optical system according to the second embodiment.

[0082] As shown in FIG. 16, first, alignment adjustment is performed on the optical system of the laser oscillator 90, excluding the condenser lens 42 (step S1). To perform step S1, quartz glass of the same thickness as the birefringent element 43 is fitted into the holder 86 instead of the birefringent element 43. In this state, the laser module 10 is operated to emit the first laser beam LB1. Instead of the laser head 100, an optical output monitor (not shown) is placed on the output side of the optical fiber 80 to measure the intensity profile of the laser beam LB. The positions of each component of the optical system are adjusted so that the peak of the power density of the laser beam LB is positioned at a preset initial position. When performing alignment adjustment, the output of the first laser beam LB1 is set to a value smaller than that during actual processing to ensure the safety of the operator and reduce damage to the optical output monitor.

[0083] After step S1 is performed, the laser module 10 is stopped, and the optical fiber 80 is removed from the first receptacle 45 (step S2). Next, the holder 86 is removed from the rotation mechanism 85, and a holder 86 with a birefringent element 43 fitted therein is attached instead (step S3). In this state, the holder 86 is rotated to adjust the beam split direction of the first laser beam LB1 (step S4). The beam split direction is confirmed, for example, by observing the position of the flat portion 43A described above.

[0084] After step S4 is performed, the optical fiber 80 is reattached to the first receptacle 45 (step S5), and the alignment of the condenser lens 42 is adjusted (step S6). This adjustment is performed by emitting the first laser beam LB1 and observing the intensity profile of the laser beam LB projected on an optical output monitor arranged on the output side of the optical fiber 80.

[0085] The alignment adjustment performed in step S6 is performed to cancel the difference in thickness between the dummy quartz glass fitted in the holder 86 in step S1 and the birefringent element 43. In other words, the position of the condenser lens 42 relative to the incident end 80A of the optical fiber 80 can be adjusted in the Z direction, which is the propagation direction of the first laser beam LB1, depending on the thickness of the birefringent element 43 along the propagation direction of the first laser beam LB1. If the laser beam LB projected on the optical output monitor is wider than a predetermined range, the condenser lens 42 is moved in the Z direction to adjust the laser beam LB to fall within the predetermined range.

[0086] According to this embodiment, the birefringent element 43 is fitted into a holder 86 connected to a rotation mechanism 85 and attached integrally to the optical fiber 80, which makes it easy to adjust the rotation of the birefringent element 43 and easily adjust the beam separation direction of the first laser beam LB1.

[0087] Furthermore, according to this embodiment, alignment adjustment of the optical system is performed without the birefringent element 43 being disposed, so that the optical components inside the laser oscillator 90 can be adjusted in the same procedure as in a normal method in which the birefringent element 43 is not provided. Furthermore, since the holder 86 in which the birefringent element 43 is fitted can be easily attached and detached from the optical fiber 80, alignment adjustment of the optical system can be easily performed without the birefringent element 43 being disposed. Furthermore, according to this embodiment, selection of the thickness t of the birefringent element 43 and adjustment of the rotation direction can be easily performed.

[0088] Although the inner surface of the holder 86 can be female-threaded to fix it to the optical component fixing mechanism 84, this makes it difficult to precisely adjust the rotation of the birefringent element 43. Therefore, as shown in this embodiment, it is preferable to provide a rotation mechanism 85 that can be operated externally and connect the optical component fixing mechanism 84 and the holder 86 via the rotation mechanism 85. This allows the holder 86 to be easily attached to and detached from the optical fiber 80, and allows precise rotation adjustment of the birefringent element 43. Furthermore, since the holder 86 in which the birefringent element 43 is fitted can be easily attached to and detached from the optical fiber 80, if a malfunction occurs in the laser oscillator 90, the location of the malfunction can be easily identified. In other words, it can be easily determined whether the malfunction occurs in the optical path of the first laser beam LB1 from the laser module 10 to the focusing optical unit 40 or between the birefringent element 43 and the optical fiber 80.

[0089] Furthermore, in this embodiment, a process of removing the optical fiber 80 (step S2 in FIG. 16) is provided to adjust the alignment of the optical system, but it is also possible to operate the rotation mechanism 85 to rotate the birefringent element 43 held by the holder 86 while the positions of the focusing lens 42, the birefringent element 43, and the optical fiber 80 are fixed, thereby adjusting the incident position of the laser beam LB relative to the core 81.

[0090] <Variation 4> Fig. 17A shows the intensity profile of a laser beam at the input end of an optical fiber immediately after shipping according to Variation 4. Fig. 17B shows the intensity profile of a laser beam at the input end of an optical fiber after long-term use according to Variation 4.

[0091] By using the optical fiber 80 shown in the second embodiment, adjustment of the laser beam LB can be easily performed immediately after shipment of the laser oscillator 90 or the laser processing apparatus 200 and after long-term use, as will be described below.

[0092] First, let us assume that when the laser oscillator 90 is shipped without the birefringent element 43 attached to the optical fiber 80, the intensity profile of the laser beam LB at the incident end 80A of the optical fiber 80 has a Gaussian distribution with a large peak in power density, as shown on the left side of Fig. 17A. In this case, the holder 86 is removed, the birefringent element 43 is fitted, and the holder 86 is attached to the optical fiber 80 again. As described above, the first laser beam LB1 is split into the first sub-beam LB 11 and the second sub-beam LB 12 and the peak value of the power density of the laser beam LB at the incident end 80A of the optical fiber 80 is lower than that shown on the left side of Fig. 9. This makes it possible to suppress deterioration of the optical characteristics of the optical fiber 80 due to damage or deterioration of the optical fiber 80, and to suppress deterioration of the output power and beam quality of the laser beam LB.

[0093] On the other hand, after the laser oscillator 90 has been used for a long time, for example, several thousand hours, the laser light source may deteriorate, and the characteristics of the first laser beam LB1 may change. For example, the half-width of the power density of the first laser beam LB1 may become wider than immediately after shipment, and the peak value of the power density may decrease accordingly.

[0094] In this case, as shown on the left side of FIG. 17B, the first sub-beam LB 11 and second sub-beam LB 12 Both of these may expand more than expected and protrude from the core 81 of the optical fiber 80. If the phenomenon shown on the left side of FIG. 17B is confirmed, remove the holder 86 from the optical fiber 80 and then remove the birefringent element 43. By doing so, the first laser beam LB1 is directly incident on the core 81 of the optical fiber 80, as shown on the right side of FIG. 17B. As described above, at this point, the spatial spread of the first laser beam LB1 is larger than immediately after shipment, and the peak value of the power density has also decreased. Therefore, even if the first laser beam LB1 is directly incident on the core 81 of the optical fiber 80, damage or deterioration of the optical fiber 80 is unlikely to occur, and a decrease in the output power and beam quality of the laser beam LB can be suppressed.

[0095] According to this modification, it is possible to suppress a decrease in the output power and beam quality of the laser beam LB by simply attaching and detaching the holder 86. Furthermore, it is possible to omit the time-consuming task of replacing the optical fiber 80, and also to reduce the increase in the cost required for replacement.

[0096] In this modification, the optical characteristics of the first laser beam LB1 change over time, and therefore the birefringent element 43 is attached to the optical fiber 80 or the birefringent element 43 is removed from the optical fiber 80. However, this is not particularly limited, and for example, after long-term use, a birefringent element 43 having a thickness different from the initial thickness may be attached to the optical fiber 80, or the holder 86 including the birefringent element 43 may be rotated. It is only necessary to adjust the intensity profile of the laser beam LB so that the laser beam LB is contained in the core 81 of the optical fiber 80 after long-term use of the laser oscillator 90.

[0097] (Embodiment 3) Fig. 18 is a schematic diagram of a laser processing apparatus according to embodiment 3. Fig. 19 is a schematic diagram of the inside of a beam combining unit. Fig. 20 shows intensity profiles of a laser beam at the incident end of an optical fiber before and after mounting a birefringent element. Fig. 21 shows intensity profiles of another laser beam at the incident end of an optical fiber before and after mounting a birefringent element.

[0098] The laser processing apparatus 200 shown in Figure 18 differs from the laser processing apparatus 200 of embodiment 1 shown in Figure 1 in that it is equipped with two laser modules 10 and that it has a beam combining unit 30 instead of the optical path changing unit 20.

[0099] The beam combining unit 30 shown in FIGS. 18 and 19 combines the second laser beams LB emitted from the two laser modules 10. A and the third laser beam LB B The first laser beam LB is spatially combined with the second laser beam LB so that their optical axes approach each other. A and the third laser beam LB BWe will further explain spatial composition of

[0100] As shown in FIG. 19, the second laser beam LB A and the third laser beam LB B The third laser beam LB enters through light entrance ports 31A and 31B provided in the third housing 31 of the beam combining unit 30, is reflected by the reflecting mirrors 32A and 32B, and travels in the Y direction. B is reflected by the reflecting mirror 33, its traveling direction is changed to the X direction, and it is incident on the space combining mirror 34. On the other hand, the second laser beam LB A The second laser beam LB reaches the space combining mirror 34 without changing its direction of travel. A The third laser beam LB passes near the upper surface of the space combining mirror 34 and heads toward the light exit port 31C. B is reflected by the spatial combining mirror 34, and its traveling direction is changed again to the Y direction. After passing through the spatial combining mirror 34, the second laser beam LB A and the third laser beam LB B When viewed along the Z direction, the optical axes of the second laser beam LB and the second laser beam LB travel so as to overlap each other. On the other hand, when viewed along the X direction or the Y direction, the second laser beam LB travels so as to overlap each other after passing through the spatial combining mirror 34. A and the third laser beam LB B and travel in the Y direction at an interval in the Z direction. A and the third laser beam LB B and are spatially combined so that their optical axes approach each other to generate a laser beam LB. The traveling direction of the laser beam LB is changed to the Z direction by a reflecting mirror (not shown), and the laser beam LB travels from the light exit port 31C into the inside of the fourth housing 41 of the light collecting optical unit 40. A second laser beam LB included in the laser beam LB A and the third laser beam LB B The two travel inside the fourth housing 41 in the Y direction at intervals.

[0101] If the birefringent element 43 is not provided in the focusing optical unit 40 or if the birefringent element 43 is not fitted in the holder 86 shown in the second embodiment, the laser beam LB is directly incident on the core 81 of the optical fiber 80, as shown on the left side of Figure 20. However, the laser beam LB is incident on the core 81 of the optical fiber 80 as the second laser beam LB. A and the third laser beam LB B The first laser beam LB A and the third laser beam LB B The intensity profile and power density distribution of each of the first laser beam LB1 and the second laser beam LB2 are similar to those of the first laser beam LB1 shown in embodiment 1. Therefore, the power density of the laser beam LB at the incident end 80A of the optical fiber 80 has two high-value peaks, which may cause damage or deterioration of the optical fiber 80 as described above.

[0102] Therefore, in this embodiment, the birefringent element 43 is provided in the condensing optical unit 40, or the birefringent element 43 is fitted in the holder 86 shown in the second embodiment, and the second laser beam LB A and the third laser beam LB B Furthermore, as shown in FIG. 20, the four generated sub-beams LB A1 , L.B. A2 , L.B. B1 , L.B. B2 The laser beam LB containing the second laser beam LB is incident on the core of the optical fiber 80. A and the third laser beam LB B The second laser beam LB is directed so that the beam splitting directions of the first and second laser beams are in the X direction. A and the third laser beam LB B and are separated from each other.

[0103] That is, in the laser oscillator 90 according to this embodiment, the laser beam LB is a second laser beam LB emitted from the laser module 10 having one laser light source. A and a third laser beam LB emitted from a laser module 10 having another laser light source. Band,

[0104] Second laser beam LB A and the third laser beam LB B The first laser beam LB is spatially combined with the second laser beam LB so that their optical axes approach each other and enter the condenser lens 42. A Two sub-beams LB A1 , L.B. A2 The third laser beam LB transmitted through the birefringent element 43 B Two sub-beams LB B1 , L.B. B2 is separated into

[0105] Second laser beam LB A and the third laser beam LB B The respective beam separation directions of the second laser beam LB A and the third laser beam LB B In other words, the second laser beam LB is directed in the X direction on the imaginary plane LP that intersects with the traveling direction of the second laser beam LB. A and the third laser beam LB B The respective beam separation directions of the second laser beam LB A and the third laser beam LB B The second laser beam LB is directed perpendicular to the Y direction of the stacked layers. A and the third laser beam LB B The first laser beam LB is separated from the second laser beam LB. A and the third laser beam LB B The beam splitting directions of the second laser beam LB A and the third laser beam LB B This is different from the first embodiment by rotating the laser beam around the direction of travel.

[0106] By doing this, each sub-beam LB A1 , L.B. A2 , L.B. B1 , L.B. B2 The peaks of the power density at the input end 80A of the optical fiber 80 are the second laser beam LBA and the third laser beam LB B In other words, the peak power density of the laser beam LB at the incident end 80A of the optical fiber 80 can be reduced, which makes it possible to suppress deterioration in the optical characteristics of the optical fiber 80 due to damage or deterioration of the optical fiber 80, and thereby suppress deterioration in the output power and beam quality of the laser beam LB.

[0107] In addition, by appropriately setting the thickness of the birefringent element 43 and the optical components inside the beam combining unit 40, the second laser beam LB A and the third laser beam LB B The proximity of the optical axis to the sub-beam LB A1 , L.B. A2 , L.B. B1 , L.B. B2 As a result, the degree of separation of the sub-beams LB with respect to the core 81, which is circular when viewed along the Z direction, can be appropriately adjusted. A1 , L.B. A2 , L.B. B1 , L.B. B2 In other words, the power density distribution of the laser beam LB at the incident end 80A of the optical fiber 80 can be made to have a top hat shape with no peak.

[0108] The second laser beam LB incident on the condenser lens 42 A and the third laser beam LB B When the stacking direction is the X direction, as shown in FIG. 21, the second laser beam LB A and the third laser beam LB B The birefringent element 43 is rotated so that the direction of each of the beam separations is the Y direction.

[0109] In this embodiment, the beam combining unit 30 is used to generate the second laser beam LB A and the third laser beam LB B However, the present invention is not limited to this. For example, two laser modules 10 may be stacked, and the second laser beam LB emitted from each of the two laser modules may be spatially combined. Aand the third laser beam LB B Alternatively, in one laser module 10, two semiconductor laser elements may be stacked inside the first housing 11, and the second laser beam LB emitted from each may be spatially combined. A and the third laser beam LB B and may be spatially compounded. [Industrial Applicability]

[0110] The laser oscillator of the present disclosure is useful because it can suppress a decrease in output power and a decrease in beam quality of a high-power laser beam guided through an optical fiber. [Explanation of symbols]

[0111] 10 Laser Module 11 First cabinet 20 Optical path changing unit 21 Second cabinet 22 Reflective mirror 23 1 / 4 wave plate (phase difference canceller) 30 Beam combining unit 31 Third cabinet 31A light entrance 31B Light entrance 31C Light exit port 32A Raising mirror 32B Standing Mirror 33 Reflective mirror 34 Space Synthesis Mirror 40 Condenser optical unit 41 4th cabinet 41A Light entrance 41B Light exit port 42 Condenser lens (condensing optical system) 43 Birefringent element 44 1 / 4 wave plate (phase difference canceller) 45 First Receptacle 50 5th cabinet 60 Control Unit 70 Power supply 80 Optical Fiber 80A input end 81 cores 82 Clad 83 Quartz Block 84 Optical component fixing mechanism 84A screw mechanism 85 Rotation mechanism 86 Holder 87 Exterior body 90 Laser Oscillator 100 laser head 200 Laser processing equipment LB laser beam LB1 First laser beam LB 11 1st sub-beam LB 12 Second sub-beam LB A Second laser beam LB B Third laser beam LB A1 Sub Beam LB A1 Sub Beam LB B1 Sub Beam LB B2 Sub Beam LP Virtual Plane

Claims

1. one or more laser light sources; an optical fiber made of quartz having a core and a cladding; a focusing optical system for guiding the first laser beam emitted from the laser light source into the optical fiber; a birefringent element disposed between the focusing optical system and the incident end of the optical fiber.

2. 2. The laser oscillator according to claim 1, the first laser beam transmitted through the birefringent element is split into two sub-beams; a laser oscillator, wherein each of the two sub-beams is incident as a laser beam on the core of the optical fiber;

3. 3. The laser oscillator according to claim 2, a beam splitting direction of the first laser beam is a minor axis direction of the first laser beam on an imaginary plane intersecting with a traveling direction of the first laser beam;

4. 2. The laser oscillator according to claim 1, The laser oscillator further comprises a phase difference canceling element disposed between the birefringent element and the input end of the optical fiber.

5. 2. The laser oscillator according to claim 1, The laser oscillator further comprises a phase difference canceling element disposed in the optical path of the first laser beam before it enters the focusing optical system.

6. 2. The laser oscillator according to claim 1, The birefringent element is incorporated into a mechanical component, and the mechanical component is attached integrally with the optical fiber.

7. 2. The laser oscillator according to claim 1, The birefringent element is rotatable about an optical axis of the first laser beam incident on the birefringent element.

8. 2. The laser oscillator according to claim 1, a position of the focusing optical system relative to the incident end of the optical fiber that is adjustable in the propagation direction of the first laser beam depending on a thickness of the birefringent element along the propagation direction of the first laser beam;

9. 2. The laser oscillator according to claim 1, The birefringent element has a flat portion cut out from its outer periphery.

10. 2. The laser oscillator according to claim 1, a birefringent element made of a uniaxial birefringent crystal material, and an anti-reflection coating applied to a surface of the birefringent element through which the first laser beam passes;

11. 3. The laser oscillator according to claim 2, A laser oscillator, wherein the beam separation direction of the first laser beam is inclined at an angle of 45° from the polarization direction of the first laser beam.

12. 2. The laser oscillator according to claim 1, A laser oscillator, wherein the wavelength region of the first laser beam is a predetermined range from ultraviolet to visible.

13. 2. The laser oscillator according to claim 1, A laser oscillator, wherein the core has a diameter of 400 μm or less.

14. 2. The laser oscillator according to claim 1, the laser beams include a second laser beam emitted from one of the laser light sources and a third laser beam emitted from another of the laser light sources; the second laser beam and the third laser beam are spatially combined so that their optical axes approach each other and are incident on the focusing optical system; The second laser beam and the third laser beam transmitted through the birefringent element are each separated into two sub-beams, a laser oscillator, wherein the beam separation direction of each of the second laser beam and the third laser beam is a direction perpendicular to the direction in which the second laser beam and the third laser beam are stacked on top of each other in an imaginary plane intersecting the propagation direction of the second laser beam and the third laser beam.

15. A laser oscillator according to any one of claims 1 to 14; a laser head that receives the laser beam guided by the optical fiber and irradiates the laser beam toward a workpiece.

Images