Laser oscillator and laser processing apparatus including the same

Abstract

To provide a laser oscillator capable of obtaining a desired beam profile by continuously changing the beam profile of a laser beam emitted from an optical fiber.SOLUTION: The laser oscillator 90 includes a laser module 10, a condenser lens 42, an optical fiber 80, a polarization adjustment mechanism 30, and a birefringent plate 43. The laser module 10 emits a linearly polarized laser beam LB. The condenser lens 42 condenses the laser beam LB on the optical fiber 80. The optical fiber 80 has a center core 81 and a ring core 83. The polarization adjustment mechanism 30 has a half-wave plate 31 and changes the polarization direction of the laser beam LB. The birefringent plate 43 branches the laser beam LB into the first laser beam LB1 and the second laser beam LB2, and changes the ratio of the light amounts of the first laser beam LA and the second laser beam LA.SELECTED DRAWING: Figure 2A

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, which uses laser light to process a workpiece, has been widely put to practical use. In addition, so-called remote processing, in which laser light is guided through an optical fiber to laser process a workpiece located at a distance from the laser oscillator, is widely known.

[0003] In laser processing, particularly in welding and cutting metals, high-power laser light is used. In this case, not only is the laser light focused toward the processing point on the workpiece, but the spatial distribution of the laser light intensity, in other words, the beam profile of the laser light, can be adjusted to a shape suitable for processing, thereby reducing spatter generated during welding. In addition, cutting speed can be improved during cutting (see, for example, Patent Document 1).

[0004] Furthermore, according to the configuration disclosed in Patent Document 1, when guiding laser light to each of the center core and the ring core in a multicore fiber, one or two laser light sources are used, and the incident position and incident angle of the laser light into the optical fiber are adjusted by optical elements. In this way, it is possible to continuously change the beam profile without replacing parts inside the laser oscillator, etc.

[0005] Furthermore, methods for changing the beam profile on the laser oscillator side are also disclosed in Patent Documents 2 to 4. Patent Document 2 proposes a method of arranging a pair of a spherical lens and an aspherical lens inside a laser head to obtain a desired beam profile on the surface of a workpiece. Patent Document 3 discloses a configuration in a multi-core fiber in which the refractive index of the cladding arranged between the center core and the ring core is made higher than the refractive index of the cladding arranged outside the ring core. In this configuration, the beam profile can be changed by adjusting the incident position of the laser light into the optical fiber. Furthermore, Patent Document 4 discloses a configuration in which, when laser light emitted from multiple laser modules is combined and guided into a multi-core fiber, the beam profile of the laser light emitted from the optical fiber is changed by adjusting the angle between the laser light and an optical component arranged in the optical path. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] US Patent Application Publication No. 2015 / 293306 [Patent Document 2] Patent No. 5602300 [Patent Document 3] Patent No. 6796142 [Patent Document 4] Patent Publication No. 2021-144175 Summary of the Invention [Problem to be solved by the invention]

[0007] In the conventional configuration disclosed in Patent Document 1, laser light is emitted from each of two laser light sources, and an optical switch is used to determine the laser light and its position to be incident on the optical fiber. However, with this configuration, it is not possible to continuously change the beam profile.

[0008] Furthermore, the manufacturing cost of the laser oscillator increases, including the cost of adjusting the optical system. Patent Document 1 also discloses a configuration in which a wedge-shaped optical component is inserted into the optical path of a single laser beam, and the laser beam is split and guided into a multi-core fiber. However, with this configuration, it is difficult to control the amount of laser beam blocked by the optical component, and the light intensity ratio of the laser beams incident on the optical fiber after splitting is unstable, which may prevent a desired beam profile from being obtained. In particular, depending on the configuration of the laser light source, the position and size of the laser beam emitted from the laser light source may fluctuate over time. In such a case, the light intensity ratio of the laser beams incident on the optical fiber after splitting is unstable, which may prevent a desired beam profile from being obtained.

[0009] Furthermore, the configuration disclosed in Patent Document 2 does not allow for continuous change of the beam profile of the laser light, and the number of parts in the laser head increases, making the laser head larger and increasing costs.

[0010] In the configuration disclosed in Patent Document 3, when changing the beam profile of the laser light, the laser light may be incident on the cladding arranged between the center core and the ring core. However, in this case, the emission angle of the laser light emitted from the optical fiber increases. In other words, the numerical aperture (NA) of the optical fiber increases. The increase in the numerical aperture reduces the beam quality of the laser light emitted from the optical fiber.

[0011] 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 continuously change the beam profile of laser light emitted from an optical fiber to obtain a desired beam profile. [Means for solving the problem]

[0012] In order to achieve the above object, the laser oscillator according to the present disclosure is a laser oscillator comprising at least a laser light source that emits laser light having linear polarization, a focusing lens that focuses the laser light, and an optical fiber having two cores and into which the laser light focused by the focusing lens is incident, and further comprising: a polarization adjustment mechanism that is arranged between the laser light source and the focusing lens and is configured to be able to change the polarization direction of the laser light, and has a first optical element; and a second optical element that is arranged between the focusing lens and the optical fiber and is configured to be able to split the laser light into a first laser light and a second laser light that travel along different optical paths, and is characterized in that the second optical element changes the ratio of the light amounts of the first laser light and the second laser light depending on the polarization direction of the laser light that has passed through the first optical element.

[0013] The laser processing device according to the present disclosure is characterized in that it comprises at least the laser oscillator and a laser head attached to the output end of the optical fiber, and the laser light guided by the optical fiber is irradiated from the laser head toward a workpiece. [Effects of the Invention]

[0014] According to the present disclosure, the beam profile of laser light emitted from an optical fiber can be continuously changed to obtain a desired beam profile. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic configuration diagram of a laser processing device according to an embodiment. [Figure 2A] 1 is a schematic configuration diagram of a main part of a laser oscillator according to an embodiment. [Figure 2B] FIG. 2 is a cross-sectional schematic view of a light-collecting optical unit. [Figure 3] FIG. 2 is a schematic diagram showing how laser light is branched inside a laser oscillator. [Figure 4A] FIG. 2 is a schematic diagram of a polarization adjustment mechanism. [Figure 4B] FIG. 10 is a schematic diagram showing how a half-wave plate rotates. [Figure 5] 10 is a schematic diagram showing the polarization state of laser light transmitted through a half-wave plate when the half-wave plate is rotated. FIG. [Figure 6] 4 is a schematic diagram showing a change in the ratio of the light amounts of a first laser beam and a second laser beam depending on the polarization state of the laser beams incident on a birefringent plate. FIG. [Figure 7] 4 is a diagram showing an example of the incident positions of a first laser beam and a second laser beam on an incident end face of an optical fiber. FIG. [Figure 8] FIG. 10 is a schematic diagram showing the branching state of laser light when a Rochon prism is used. [Figure 9] 10 is a schematic diagram showing the travel of a first laser beam and a second laser beam emitted from a laser head when a birefringent plate is used. FIG. [Figure 10] 10 is a schematic diagram showing the travel of a first laser beam and a second laser beam emitted from a laser head when a Rochon prism is used. FIG. [Figure 11] FIG. 10 is a schematic diagram of a polarization adjustment mechanism according to Modification 1. [Figure 12] FIG. 1 is a perspective view of a half-wave plate. [Figure 13] FIG. 10 is a schematic diagram showing how the polarization adjustment mechanism slides. [Figure 14] FIG. 10 is a side view of a half-wave plate according to Modification 2. [Figure 15] FIG. 11 is a cross-sectional view showing a main part of a laser oscillator according to a third modification. [Figure 16] 10 is a schematic cross-sectional view of a main part of another laser oscillator according to Modification 3. FIG. [Figure 17] 10 is a schematic cross-sectional view of a main part of still another laser oscillator according to Modification 3. FIG. [Figure 18] FIG. 11 is a cross-sectional view showing a main part of a laser oscillator according to a fourth modification. [Figure 19] FIG. 11 is a schematic configuration diagram of a laser processing device according to a fifth modified example. [Figure 20] FIG. 11 is a schematic configuration diagram of a main part of a laser oscillator according to Modification 5. DETAILED DESCRIPTION OF THE INVENTION

[0016] 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.

[0017] (Embodiment) [Configuration of laser processing equipment] 1 is a schematic diagram of a laser processing apparatus according to an embodiment. In the following description, the traveling direction of laser light LB, which is emitted from the beam shaper 20 and will be described later, 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 light LB inside the third housing 41 of the focusing optical unit 40. The main traveling direction of the laser light LB in the beam shaper 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. In addition, a virtual cutting plane perpendicular to the Z direction, as viewed from the Z direction, is referred to as a cross-sectional view.

[0018] 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.

[0019] The laser processing apparatus 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.

[0020] The laser oscillator 90 includes one laser module 10 , a beam shaper 20 , a focusing optical unit 40 , a control unit 60 , a power supply 70 , and an optical fiber 80 .

[0021] The laser module 10 has multiple laser light sources (not shown) inside the first housing 11. The laser light source in this embodiment is composed of multiple laser diodes or one or multiple laser diode bars. In other words, the laser light source has multiple emitters (not shown) that emit laser light. In this embodiment, the laser light emitted from each of the multiple emitters is wavelength-combined within the laser module 10 and emitted from the laser module 10 as a single laser light LB (see FIG. 2A). However, the method of combining the laser light is not limited to wavelength combining, and other methods may be used. In addition, the laser light LB is linearly polarized.

[0022] The beam shaper 20 appropriately shapes the laser light LB so that it fits inside the effective focusing diameter of the focusing lens 42 (see FIGS. 2A and 2B) of the focusing optical unit 40. The beam shaper 20 also changes the optical path of the laser light LB and makes it incident on the focusing optical unit 40. The configuration of the beam shaper 20 will be described later.

[0023] The focusing optical unit 40 focuses the laser light LB emitted from the beam shaper 20 toward the incident end 80A of the optical fiber 80 (see FIGS. 2A and 2B). The focusing optical unit 40 also splits the laser light LB and makes it incident on at least one of the center core 81 and the ring core 83 of the optical fiber 80. The configuration of the focusing optical unit 40 will be described later.

[0024] The optical fiber 80 guides the laser light LB incident from the focusing optical unit 40, specifically at least one of the first laser light LB1 and the second laser light LB2 (see FIG. 3), to the laser head 100. The configuration of the optical fiber 80 will be described later.

[0025] 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 light LB reaches a predetermined target value. The control unit 60 also controls the operation of a rotation mechanism 32 (see FIG. 2A), which will be described later.

[0026] 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).

[0027] The laser head 100 converts the laser light LB guided by the optical fiber 80 into processing laser light LB P For example, in the laser processing apparatus 200 shown in FIG. 1, processing laser light LB is directed toward a workpiece W, which is an object to be processed, placed at a predetermined position. P In this way, the workpiece W is laser processed.

[0028] [Configuration of the main parts of the laser oscillator] Fig. 2A is a schematic diagram of the main parts of a laser oscillator according to an embodiment. Fig. 2B is a cross-sectional schematic diagram of a focusing optical unit. For ease of explanation, in Fig. 2B and the following drawings, only the optical axes of the laser beam LB and the first and second laser beams LB1 and LB2 described below are shown.

[0029] As shown in FIG. 2A, laser light LB enters the inside of the beam shaper 20 from a light exit port 11A provided in a first housing 11 of the laser module .

[0030] The beam shaper 20 has a plurality of optical components inside a second housing 21. The second housing 21 has a light entrance 21A and a light exit 21B. The light entrance 21A is connected to the light exit 11A of the laser module 10, and the light exit 21B is connected to the light entrance 41A provided in the third housing 41 of the focusing optical unit 40.

[0031] The laser light LB incident from the light entrance port 21A is reflected by the first folding mirror 22, and the traveling direction is changed from the Z direction to the Y direction. The laser light LB then enters the beam shaping unit .

[0032] The beam shaping unit 23 has, for example, a collimating lens (not shown) and collimates the incident laser light LB. By doing so, it is possible to suppress the spread of the laser light LB so that the diameter is equal to or smaller than the effective entrance diameter of the focusing lens 42 of the focusing optical unit 40. Note that the beam shaping unit 23 may also have other optical components. Furthermore, the beam shaping unit 23 may be configured with optical components other than a collimating lens (see FIG. 20).

[0033] Polarizing beam splitter (third optical element) 24 transmits only the p-polarized component of the incident laser light LB and reflects the other s-polarized component. The reflected light component enters damper 25 and is converted into heat by damper 25.

[0034] The laser light LB transmitted through the polarizing beam splitter 24 is incident on a half-wave plate (first optical element) 31 of the polarization adjustment mechanism 30. The configuration and function of the polarization adjustment mechanism 30 will be described later.

[0035] The laser light LB transmitted through the half-wave plate 31 is reflected by the second folding mirror 26, and its traveling direction is changed from the Y direction to the Z direction. The laser light LB then enters the focusing optical unit 40.

[0036] 2A and 2B, the condensing optical unit 40 has a third housing 41, a condensing lens 42, and a birefringent plate (second optical element) 43. The condensing lens 42 is held by a first holder 41C and is housed inside the third housing 41 in a positioned state. The birefringent plate 43 is held by a second holder 41D and is housed inside the third housing 41 in a positioned state. The birefringent plate 43 is disposed between the condensing lens 42 and the incident end 80A of the optical fiber 80 along the Z direction. Note that components other than the condensing lens 42 and the birefringent plate 43 may be housed inside the third housing 41.

[0037] An incident end 80A of an optical fiber 80 is connected to the light exit port 41B of the third housing 41. As shown in FIG. 2B, the optical fiber 80 has a center core 81, a first ring clad 82, a ring core 83, and a second ring clad 84.

[0038] The center core 81 is provided at the axis of the optical fiber 80 and is circular in cross section, with a first ring clad 82 that is ring-shaped in cross section provided to cover the outer peripheral surface of the center core 81. A ring core 83 that is ring-shaped in cross section is provided to cover the outer peripheral surface of the first ring clad 82, and a second ring clad 84 that is ring-shaped in cross section is provided to cover the outer peripheral surface of the ring core 83 (see FIG. 7). In other words, the center core 81, the first ring clad 82, the ring core 83, and the second ring clad 84 are coaxial and arranged concentrically with respect to the axis.

[0039] The center core 81, the first ring clad 82, the ring core 83, and the second ring clad 84 are all made of quartz. However, the optical properties are adjusted so that the refractive index of the center core 81 and the ring core 83, which are optical waveguides, is higher than the refractive index of the first ring clad 82 and the second ring clad 84, which are optical confinement layers, respectively. The outer circumferential surface of the second ring clad 84 is covered with an exterior material (not shown). The exterior material mechanically protects the optical fiber 80.

[0040] As shown in FIG. 2B, the laser light LB incident on the birefringent plate 43 is split into a first laser light LB1 and a second laser light LB2. The first laser light LB1 and the second laser light LB2 emitted from the birefringent plate 43 travel parallel to each other in the Z direction. The material of the birefringent plate 43 and its plate thickness t in the Z direction, which is the traveling direction of the laser light LB, are set so that the first laser light LB1 is incident on the center core 81 and the second laser light LB2 is incident on the ring core 83. In addition, a quartz block 85 is fused to the incident end surface 80A1 of the optical fiber 80. The quartz block 85 is provided to reduce the reflectivity at the incident end 80A of the optical fiber 80 and to reduce the risk of burnout due to contaminants.

[0041] Hereinafter, a method for splitting the laser light LB and changing the ratio of the light amounts of the first laser light LB1 and the second laser light LB2 will be described.

[0042] [Branching of laser light in a laser oscillator and light intensity control after branching] 3 is a schematic diagram showing how laser light is split inside the laser oscillator, in which the quartz block 85 is not shown.

[0043] The birefringent plate 43 is a plate-shaped optical element made of quartz crystal. The material of the birefringent plate 43 is not particularly limited to this, and may be, for example, lithium niobate (LiNbO3), which is preferably a uniaxial birefringent crystal.

[0044] Quartz, a uniaxial crystal, has optical anisotropy. Therefore, as shown in FIGS. 2B and 3, the laser beam LB incident on the birefringent plate 43 is split into an ordinary ray and an extraordinary ray. The ordinary ray and extraordinary ray emitted from the birefringent plate 43 travel parallel to each other in the Z direction while maintaining a beam separation width d. The ordinary ray is the first laser beam LB1 shown in FIGS. 2A and 3, and the extraordinary ray is the second laser beam LB2. In this embodiment, the direction of the optical axis of the birefringent plate 43 is set so that the first laser beam LB1 and the second laser beam LB2 are separated in the Y direction. However, considering that the shape of the optical fiber 80 is axially symmetric, beam separation may occur in any direction on a virtual plane (XY plane) that includes the X and Y directions. In a birefringent material, the optical axis refers to a crystal axis in a direction in which birefringence does not occur. When the direction along the optical axis coincides with the polarization direction of the laser light LB, the laser light LB passes through the birefringent material without being split.

[0045] The thickness of the birefringent plate 43 is t, and the refractive index of the birefringent plate 43 with respect to the first laser beam LB1, that is, the refractive index of the ordinary ray, is n о The refractive index of the birefringent plate 43 with respect to the second laser beam LB2, that is, the refractive index of the extraordinary ray, is n e Then, the beam separation width d is expressed by the relationship shown in equation (1).

[0046] d=t×(n о 2 -n e 2 ) / (n о 2 +n e 2 ) ···(1) As is clear from equation (1), when it is desired to change the beam separation width d, the plate thickness t of the birefringent plate 43 is changed. Note that the rate of change of the beam separation width d with respect to the plate thickness t changes depending on the wavelength of the laser light LB. Furthermore, when the material of the birefringent plate 43 is changed, the rate of change of the beam separation width d with respect to the plate thickness t also changes. For example, when the material of the birefringent plate 43 is lithium niobate, the rate of change of the beam separation width d with respect to the plate thickness t is greater than when the birefringent plate 43 is made of quartz.

[0047] Although not shown, it is preferable that an anti-reflection coating be applied to each of the transmission surfaces of the birefringent plate 43 for the laser light LB, i.e., the entrance surface for the laser light LB and the exit surfaces for the first laser light LB1 and the second laser light LB2. By applying an anti-reflection coating, unwanted reflection of the laser light LB and the first laser light LB1 and the second laser light LB2 at the birefringent plate 43 can be prevented, and output loss of the first laser light LB1 and the second laser light LB2 before they enter the optical fiber 80 can be reduced.

[0048] Furthermore, as will be described in detail later, the proportion of the laser light LB split into the first laser light LB1 and the second laser light LB2 after passing through the birefringent plate 43 is determined by the relationship between the optical axis of the half-wave plate 31 and the polarization direction of the laser light LB. For this reason, in the laser oscillator 90 of this embodiment, a polarization adjustment mechanism 30 is disposed in the optical path of the laser light LB before it enters the condenser lens 42, and by changing the polarization direction of the laser light LB, the proportion of the laser light LB split into the first laser light LB1 and the second laser light LB2 is changed. This will be described in further detail below.

[0049] Fig. 4A is a schematic diagram of a polarization adjustment mechanism. Fig. 4B is a schematic diagram showing the rotation of a half-wave plate. Fig. 5 is a schematic diagram showing the polarization state of laser light transmitted through a half-wave plate when the half-wave plate is rotated. Fig. 6 is a schematic diagram showing the change in the ratio of the light intensity of the first laser light and the second laser light depending on the polarization state of the laser light incident on the birefringent plate.

[0050] As shown in Fig. 4A, the polarization adjustment mechanism 30 is composed of a half-wave plate (first optical element) 31 and a rotation mechanism 32 that holds the half-wave plate 31. The half-wave plate 31 is made of a birefringent material such as quartz. The rotation mechanism 32 is connected to a driving unit such as a motor (not shown), and rotates the half-wave plate 31 around the optical axis of the incident laser light LB, in this case, around an axis parallel to the Y direction, in response to a control signal from the control unit 60, as shown in Fig. 4B.

[0051] As described above, the laser light LB is linearly polarized light. As shown in the left diagram of Figure 5, if the polarization direction of the laser light LB incident on the half-wave plate 31 is the same as the direction along the optical axis of the half-wave plate 31, the polarization direction of the laser light LB is maintained even after passing through the half-wave plate 31. The position of the half-wave plate 31 in this case is called the initial position.

[0052] When the half-wave plate 31 is rotated by an angle θ1 from its initial position, the angular difference between the optical axis of the half-wave plate 31 and the polarization direction of the laser light LB also becomes θ1, as shown in the center diagram of Fig. 5. In this case, the polarization direction of the laser light LB that has passed through the half-wave plate 31 changes to a direction rotated by 2θ1 around the optical axis of the laser light LB from the polarization direction at the initial position.

[0053] The half-wave plate 31 is further rotated by an angle θ1. In other words, when the half-wave plate 31 is rotated by an angle 2θ1 from the initial position, the angular difference between the optical axis of the half-wave plate 31 and the polarization direction of the laser light LB becomes 2θ1, as shown in the right diagram of Figure 5. In this case, the polarization direction of the laser light LB that has passed through the half-wave plate 31 changes to a direction rotated by 4θ1 around the optical axis of the laser light LB from the polarization direction in the initial position.

[0054] If θ1 is set to 22.5°, for example, as shown in the center diagram of Fig. 5, the polarization direction 1 of the laser light LB that has passed through the half-wave plate 31 changes to a direction rotated 45° around the optical axis of the laser light LB from the polarization direction at the initial position. As shown in the right diagram of Fig. 5, the polarization direction 2 of the laser light LB that has passed through the half-wave plate 31 changes to a direction rotated 90° around the optical axis of the laser light LB from the polarization direction at the initial position.

[0055] By rotating the half-wave plate 31 in this manner, the polarization direction of the laser light LB that has passed through the half-wave plate 31 changes continuously from the polarization direction at the initial position. Meanwhile, the birefringent plate 43 also has an optical axis. Therefore, the ratio at which the laser light LB that has passed through the birefringent plate 43 is split into the first laser light LB1 and the second laser light LB2 is determined by the relationship between the polarization direction of the laser light LB that enters the birefringent plate 43 and the direction along the optical axis of the birefringent plate 43.

[0056] 6(a), when the polarization direction of the laser light LB incident on the birefringent plate 43 coincides with the direction along the optical axis of the birefringent plate 43, birefringence does not occur. Therefore, the laser light LB passes through the birefringent plate 43 as is and enters the center core 81. Furthermore, the beam profile of the laser light LB at the incident end face 80A1 of the optical fiber 80 has a single-peaked Gaussian shape centered on the position of the center core 81. This shape is also reflected in the beam profile of the laser light LB emitted from the optical fiber 80.

[0057] 6(b) and 6(c), when the laser light LB is incident on the birefringent plate 43 with its polarization direction rotated with respect to the direction along the optical axis of the birefringent plate 43, birefringence occurs, and the laser light LB is split into a first laser light LB1 and a second laser light LB2. As a result, the first laser light LB1 is incident on the center core 81, and the second laser light LB2 is incident on the ring core 83.

[0058] Therefore, the beam profile of the laser light LB includes the beam profile of the first laser light LB1 centered at the position of the center core 81 and the beam profile of the second laser light LB2 generated at the position of the ring core 83 radially outward of the beam profile of the first laser light LB1. When viewed along the X or Y direction, the beam profile of the second laser light LB2 has a bimodal shape having two peaks. Note that in reality, the beam profile of the second laser light LB2 expands in a ring shape radially outward from the beam profile of the first laser light LB1. This shape is also reflected in the beam profile of the laser light LB emitted from the optical fiber 80.

[0059] Furthermore, the ratio of the light intensity of the first laser light LB1 to the light intensity of the second laser light LB2 changes depending on the degree of birefringence of the laser light LB by the birefringent plate 43, or, from another perspective, the angular difference between the polarization direction of the laser light LB and the optical axis of the birefringent plate 43. Specifically, the ratio of the light intensity of the second laser light LB2 to the light intensity of the first laser light LB1 increases as the angular difference between the polarization direction of the laser light LB and the optical axis of the birefringent plate 43 increases.

[0060] Therefore, when the angular difference is small, the peak of the beam profile of the first laser beam LB1 is higher than the peak of the beam profile of the second laser beam LB2, as shown in FIG. 6(b). On the other hand, when the angular difference is large, the peak of the beam profile of the second laser beam LB2 is higher than the peak of the beam profile of the first laser beam LB1, as shown in FIG. 6(c). When the angular difference becomes 90°, the entire laser beam LB is refracted by the birefringent plate 43 and emitted as an extraordinary ray, i.e., the second laser beam LB2. In this case, when the entire laser beam LB is incident on the ring core 83 and viewed along the X or Y direction, the beam profile of the laser beam LB is bimodal, having two peaks. As described above, in reality, the beam profile of the laser beam LB spreads in a ring shape.

[0061] Furthermore, if the beam separation width d is not set appropriately, a part of the second laser light LB2 may be incident on the first ring clad 82 or the second ring clad 84. When this happens, not only does an output loss of the laser light LB emitted from the optical fiber 80 occur, but the NA (divergence angle) of the laser light emitted from the optical fiber 80 also increases. As a result, the laser light LB emitted from the optical fiber 80, and ultimately the processing laser light LB P This may result in a deterioration of the beam quality.

[0062] In view of this, the beam separation width d needs to be set in accordance with the dimensions of each part of the optical fiber 80. Hereinafter, this will be explained with reference to FIG.

[0063] FIG. 7 is a diagram showing an example of the incident positions of the first laser light and the second laser light on the incident end face of the optical fiber.

[0064] The example shown in Fig. 7 corresponds to, for example, Fig. 6(b). In this example, the first laser light LB1 is incident on the incident end face 80A1 of the optical fiber 80 so that the center of the incident spot of the first laser light LB1 coincides with the center of the center core 81, i.e., the axis of the optical fiber 80. Furthermore, the second laser light LB2 is incident on the incident end face 80A1 so that the center of the incident spot of the second laser light LB2 coincides with the center of the ring core 83 in the radial direction.

[0065] The diameter of the incident spot of the first laser beam LB1 and the second laser beam LB2, i.e., the spot diameter, is defined as A0, and the diameters of the center core 81, the first ring clad 82, the ring core 83, and the second ring clad 84 are defined as D1 to D4, respectively. In this case, it is sufficient that the distance between the center of the incident spot of the first laser beam LB1 and the center of the incident spot of the second laser beam LB2 is equal to the beam separation width d. Therefore, the beam separation width d satisfies the relationship shown in formula (2).

[0066] d=D2 / 2+(1 / 2)×((D3-D2) / 2)=(D2+D3) / 4 ···(2) On the other hand, the incident spot of the first laser beam LB1 only needs to be located inside the center core 81 so as not to extend beyond the center core 81. Similarly, the incident spot of the second laser beam LB2 only needs to be located inside the ring core 83 so as not to extend beyond the ring core 83. In view of this, as is clear from FIG. 7, the beam separation width d only needs to satisfy the relationship shown in formula (3).

[0067] (D2-D1) / 2+A0≦d≦(D1+D3) / 2-A0...(3) [Effects, etc.] As described above, the laser oscillator 90 according to this embodiment includes at least the laser module 10, the condenser lens 42, and the optical fiber 80.

[0068] The laser module 10 has one or more laser light sources and emits linearly polarized laser light LB. The condenser lens 42 condenses the incident laser light LB toward the optical fiber 80. The optical fiber 80 has a center core 81 and a ring core 83, and the laser light LB condensed by the condenser lens 42 is incident on the optical fiber 80.

[0069] The laser oscillator 90 further includes a polarization adjustment mechanism 30 and a birefringent plate (second optical element) 43. The polarization adjustment mechanism 30 has a half-wave plate (first optical element) 31, and is disposed between the laser module 10 and the condenser lens 42, and is configured to be able to change the polarization direction of the laser light LB.

[0070] The birefringent plate 43 is disposed between the condenser lens 42 and the optical fiber 80, and is configured to be able to split the laser light LB into a first laser light LB1 and a second laser light LB2 traveling along different optical paths. The birefringent plate 43 also changes the ratio of the light amounts of the first laser light LB1 and the second laser light LB2 according to the polarization direction of the laser light LB that has passed through the half-wave plate 31 of the polarization adjustment mechanism 30.

[0071] By configuring the laser oscillator 90 in this manner, the beam profile of the laser light LB emitted from the laser module 10 can be continuously changed with a simple configuration.

[0072] Furthermore, when a laser diode bar or a laser diode is used as the laser light source, the position and size of the laser light LB tend to fluctuate over time due to heat generation during operation and the like.

[0073] On the other hand, according to this embodiment, the entire amount of the laser light LB that has passed through the condenser lens 42 is incident on the birefringent plate 43. As a result, even if the time fluctuation of the laser light LB is large, the beam profile of the laser light LB can be changed continuously without being affected by the time fluctuation.

[0074] Furthermore, according to this embodiment, the birefringent plate 43 is used as the second optical element that splits the laser light LB into the first laser light LB1 and the second laser light LB2 traveling along different optical paths. In this way, the first laser light LB1 and the second laser light LB2 emitted from the birefringent plate 43 travel parallel to each other and enter the optical fiber 80. In other words, the first laser light LB1 and the second laser light LB2 can be made to have the same angle of incidence on the optical fiber 80. This makes it possible to make the numerical apertures of the first laser light LB1 and the second laser light LB2 emitted from the center core 81 and the ring core 83, respectively, the same. As a result, the processing laser light LB P In addition, the laser head 100 is provided with a processing laser beam LB. P There is no need to provide optical components for improving the beam quality, and the laser head 100 can be made smaller.

[0075] The polarization adjustment mechanism 30 is configured to be able to rotate the half-wave plate 31 around the optical axis of the incident laser light LB. The polarization direction of the laser light LB that has passed through the half-wave plate 31 is continuously changed according to the rotation angle of the half-wave plate 31 relative to its initial position. The birefringent plate 43 continuously changes the ratio of the light amounts of the first laser light LB1 and the second laser light LB2 according to the polarization direction of the laser light LB that has passed through the half-wave plate 31.

[0076] By providing the laser oscillator 90 with the polarization adjustment mechanism 30 described above, the polarization direction of the laser light LB incident on the birefringent plate 43 can be easily and continuously changed.

[0077] The condenser lens 42 and the birefringent plate 43 are preferably housed in the same housing, in this case, inside the third housing 41. In this way, it is possible to ensure that the entire amount of laser light LB is incident on the birefringent plate 43.

[0078] The optical fiber 80 has at least a center core 81 provided at the axis, a ring core 83 that is ring-shaped in cross section and provided at a distance from the center core 81 in the radial direction, and a first ring clad 82 that is ring-shaped in cross section and provided between the center core 81 and the ring core 83. The first laser light LB1 is incident on the center core 81, and the second laser light LB2 is incident on the ring core 83.

[0079] By defining the configuration of the optical fiber 80 and the incident positions of the first laser light LB1 and the second laser light LB2 in this manner, the beam profile of the laser light LB emitted from the optical fiber 80 can be easily and continuously changed.

[0080] Let d be the beam separation width between the first laser beam LB1 and the second laser beam LB2 emitted from the birefringent plate 43. When D1 is the diameter of the center core 81, D2 is the diameter of the first ring clad 82, and D3 is the diameter of the ring core 83, it is preferable that the relationship shown in formula (3) be satisfied.

[0081] (D2-D1) / 2+A0≦d≦(D1+D3) / 2-A0...(3) A0 is the spot diameter of each of the first laser beam LB1 and the second laser beam LB2 on the incident end face 80A1 of the optical fiber 80.

[0082] It is preferable to further include a polarizing beam splitter (third optical element) 24 that is disposed between the laser module 10 and the half-wave plate 31 and transmits only a predetermined polarized component, in this case the p-polarized component, contained in the laser light LB.

[0083] Typically, the polarization ratio of laser light emitted from a laser diode is less than 100%, remaining at around 90% to 97%. When light of different polarization components is incident on the half-wave plate 31, the polarization ratio of the laser light LB transmitted through the half-wave plate 31 does not become 100%, and the first laser light LB1 and the second laser light LB2 transmitted through the birefringent plate 43 may not be split at the desired ratio.

[0084] By placing the polarizing beam splitter 24 between the laser module 10 and the half-wave plate 31, the polarization ratio of the laser light LB transmitted through the half-wave plate 31 can be made 100%, and the first laser light LB1 and the second laser light LB2 transmitted through the birefringent plate 43 are split in the desired ratio.

[0085] The laser processing device 200 according to this embodiment includes at least a laser oscillator 90 and a laser head 100 attached to the emission end 80B of the optical fiber 80. The laser beam LB guided by the optical fiber 80 is emitted from the laser head 100 as processing laser beam LB. P and is irradiated towards the workpiece W.

[0086] By configuring the laser processing device 200 in this way, the laser light LB, and in turn the processing laser light LB P Therefore, the beam profile of the processing laser light LB having a beam profile according to the desired processing mode can be continuously changed. P The workpiece W can be irradiated with the laser beam, thereby laser processing the workpiece W. This makes it possible to use a single laser processing device 200 to appropriately perform laser processing on workpieces W of various shapes and materials.

[0087] The laser processing apparatus 200 preferably further includes a beam shaper 20 and a focusing optical unit 40. The beam shaper 20 has a second housing 21, and receives the laser light LB from the laser module 10. The focusing optical unit 40 has a third housing 41, and causes the laser light LB emitted from the beam shaper 20 to enter an optical fiber 80. The polarization adjustment mechanism 30 is housed inside the second housing 21. The focusing lens 42 is housed inside the third housing 41.

[0088] By doing so, the position of each optical element is reliably fixed, and the processing laser light LB having a beam profile according to the desired processing mode is emitted. P can be obtained.

[0089] In this embodiment, an example has been shown in which the birefringent plate 43 is used as the second optical element that splits the laser beam LB into the first laser beam LB1 and the second laser beam LB2. However, the present invention is not limited to this, and a polarizing prism such as a Rochon prism or a Wollaston prism may also be used as the second optical element.

[0090] Fig. 8 is a schematic diagram showing the splitting state of laser light when a Rochon prism is used. In the example shown in Fig. 8, the polarization direction of laser light LB is rotated 45° from the initial position described above. As shown in Fig. 8, even when a Rochon prism 44 is used, laser light LB can be split into first laser light LB1 and second laser light LB2. The polarization direction of second laser light LB2 is rotated 90° from the polarization direction of first laser light LB1.

[0091] In this case, as shown in FIG. 8 , the first laser beam LB1, which is an ordinary ray, travels along the traveling direction of the laser beam LB. On the other hand, the second laser beam LB2, which is an extraordinary ray, travels toward the optical fiber 80 at an angle θa (>0) with the traveling direction of the first laser beam LB1. As a result, a difference in numerical aperture occurs between the first laser beam LB1 and the second laser beam LB2 emitted from the optical fiber 80. Furthermore, the Wollaston prism can increase the beam separation width d compared to when the birefringent plate 43 is used. Therefore, even when an optical fiber 80 with a long diameter is used, the first laser beam LB1 can be incident on the center core 81 and the second laser beam LB2 can be incident on the ring core 83. Furthermore, when the Rochon prism 44 is used, the beam separation width d can be increased in the same way, but the angle of incidence of the first laser beam LB1 and the second laser beam LB2 onto the optical fiber 80 becomes larger, increasing the numerical aperture.

[0092] Fig. 9 is a schematic diagram showing the travel of the first laser beam and the second laser beam emitted from the laser head when a birefringent plate is used, and Fig. 10 is a schematic diagram showing the travel of the first laser beam and the second laser beam emitted from the laser head when a Rochon prism is used.

[0093] 9 and 10, the laser head 100 has a collimating lens 120 and a condenser lens 130 inside a fourth housing 110. An output end 80B of an optical fiber 80 is connected to a light input port 110A of the fourth housing 110. The light output port 110B of the fourth housing 110 is covered with a protective glass 140. Note that other components may be provided inside the fourth housing 110.

[0094] 9, when the laser beam LB is split into the first laser beam LB1 and the second laser beam LB2 using the birefringent plate 43, the numerical apertures of the first laser beam LB1 and the second laser beam LB2 are the same. P is the laser beam LB for processing on the surface of the workpiece W. P At this spot position, the desired beam profile generated at the exit position of the optical fiber 80 can be projected.

[0095] On the other hand, as shown in Fig. 10, when the laser beam LB is split into the first laser beam LB1 and the second laser beam LB2 using the Rochon prism 44, the numerical aperture of the second laser beam LB2 becomes larger than the numerical aperture of the first laser beam LB1. P The numerical aperture of the optical fiber 80 also increases. Furthermore, the profile of the beam generated at the exit position of the optical fiber 80 is not projected directly onto the surface of the workpiece W, but rather a beam profile is formed by mixing the beam components guided by the center core 81 and the ring core 83. In actual laser processing, this is taken into consideration, and for example, the collimator lens 120 and the condenser lens 130 are placed inside the fourth housing 110 after adjusting their respective optical characteristics. This allows a beam profile in which the beam components guided by the center core 81 and the ring core 83 are mixed together to be used for laser processing.

[0096] <Variation 1> Fig. 11 is a schematic diagram of a polarization adjustment mechanism according to Modification 1. Fig. 12 is a perspective view of a half-wave plate. Fig. 13 is a schematic diagram showing how the polarization adjustment mechanism slides. For ease of explanation, in Fig. 11 and the subsequent drawings, parts that are the same as those in the embodiment are given the same reference numerals, and detailed explanations will be omitted.

[0097] In the embodiment, an example has been shown in which the polarization adjustment mechanism 30 rotates the half-wave plate 31 around the optical axis of the incident laser light LB, thereby continuously changing the polarization direction of the laser light that has passed through the half-wave plate 31. However, the configuration of the polarization adjustment mechanism 30 is not particularly limited to this, and may be, for example, a configuration as shown in FIG.

[0098] 11 includes a slide mechanism 33 having first to third openings 33A to 33C, a half-wave plate 34, and a quarter-wave plate 35. The first to third openings 33A to 33C are arranged in this order at equal intervals (L1) in the longitudinal direction of the slide mechanism 33, in this case the X direction. The half-wave plate 34 is arranged in the third opening 33C, and the quarter-wave plate 35 is arranged in the second opening 33B. On the other hand, no optical element is arranged in the first opening 33A, and it is an empty space.

[0099] The half-wave plate 34 of this modified example is a so-called zero-order wave plate, formed by stacking a first quartz crystal plate 34A and a second quartz crystal plate 34B. As shown in Fig. 12, the first quartz crystal plate 34A and the second quartz crystal plate 34B are stacked so that their optical axes are perpendicular to each other. The thickness of the first quartz crystal plate 34A is different from the thickness of the second quartz crystal plate 34B. Although not shown, the quarter-wave plate 35 is also a zero-order wave plate formed by stacking two quartz crystal plates of different thicknesses.

[0100] The slide mechanism 33 is connected to a drive unit such as a motor (not shown). The drive unit translates the slide mechanism 33 in the X direction as shown in Fig. 13 in response to a control signal from the control unit 60. When the slide mechanism 33 is in the initial position, the laser light LB travels so as to pass through the first opening 33A. In other words, the polarization adjustment mechanism 30 does not polarize the polarization direction of the laser light LB.

[0101] When the sliding mechanism 33 is moved by a distance L1 in the X direction from the initial position, the laser light LB is incident on the quarter-wave plate 35 provided in the second opening 33B. After passing through the quarter-wave plate 35, the laser light LB is changed from linearly polarized light to circularly polarized light. When the sliding mechanism 33 is further moved by a distance L1 in the X direction, the laser light LB is incident on the half-wave plate 34 provided in the third opening 33C. After passing through the half-wave plate 34, the laser light LB is changed from circularly polarized light to linearly polarized light. However, the polarization direction of the laser light LB is rotated by 90° from the polarization direction of the laser light LB before passing through the half-wave plate 34.

[0102] According to this modification, the polarization direction of the laser light LB can be changed in stages by the polarization adjustment mechanism 30. This makes it possible to change in stages the ratio of the light amounts of the first laser light LB1 and the second laser light LB2 emitted from the birefringent plate 43. When the laser light LB passes through the first opening 33A, the laser light LB is not birefringent in the birefringent plate 43 and enters the center core 81 as is.

[0103] When the laser light LB passes through the quarter-wave plate 35 provided in the second opening 33B, the laser light LB is split into a first laser light LB1 and a second laser light LB2 by the birefringent plate 43. The first laser light LB1 is incident on the center core 81, and the second laser light LB2 is incident on the ring core 83. The birefringent plate 43 also splits the first laser light LB1 and the second laser light LB2 so that the light intensity ratio is approximately 1:1.

[0104] When the laser light LB passes through the half-wave plate 34 provided in the third opening 33C, the polarization direction of the laser light LB is rotated by 90° by the birefringent plate 43 and the laser light LB is incident on the ring core 83 as the second laser light LB2.

[0105] For example, when there are only a few types of shapes and materials of the workpieces W to be processed by the laser processing device 200, the polarization direction of the laser light LB can be changed stepwise as shown in this modified example. P The beam profile may be changed in stages.

[0106] <Variation 2> FIG. 14 is a side view of a half-wave plate according to the second modification.

[0107] The half-wave plate 36 shown in Fig. 14 is similar to the half-wave plate 34 of Modification 1 shown in Fig. 12 in that it is formed by stacking a third quartz crystal plate 36A and a fourth quartz crystal plate 36B. Also, like the half-wave plate 34 of Modification 1 shown in Fig. 12, the optical axis of the third quartz crystal plate 36A and the optical axis of the fourth quartz crystal plate 36B are perpendicular to each other.

[0108] 14 differs from the half-wave plate 34 of Variation 1 shown in Fig. 12 in that the thickness of the third quartz crystal plate 36A in the Y direction, i.e., the thickness along the propagation direction of the incident laser light LB, changes continuously along the Z direction. Also, the third quartz crystal plate 36A is configured to be slidable along the Z direction by a drive unit (not shown).

[0109] According to this modification, by sliding the third quartz plate 36A in the Z direction, the distance the laser light LB passes through the third quartz plate 36A can be changed from ta to tb (>ta). That is, the polarization direction of the laser light LB after passing through the half-wave plate 36 changes depending on the distance the laser light LB passes through the third quartz plate 36A. Furthermore, when the distance the laser light LB passes through the third quartz plate 36A is continuously changed, the polarization direction of the laser light LB after passing through the half-wave plate 36 changes accordingly.

[0110] Therefore, according to this modification, by sliding the third quartz crystal plate 36A in the Z direction, it is possible to continuously change the polarization direction of the laser light LB after passing through the half-wave plate 36. This allows the light intensity ratio between the first laser light LB1 and the second laser light LB2 emitted from the birefringent plate 43 to be continuously changed, thereby controlling the polarization direction of the processing laser light LB. P The beam profile can be continuously changed.

[0111] In this modification, the third quartz crystal plate 36A has a so-called wedge shape, but the fourth quartz crystal plate 36B may also have a wedge shape.

[0112] <Variation 3> Fig. 15 is a schematic cross-sectional view of a main part of a laser oscillator according to Modification 3. Fig. 16 is a schematic cross-sectional view of a main part of another laser oscillator according to Modification 3. Fig. 17 is a schematic cross-sectional view of a main part of yet another laser oscillator according to Modification 3.

[0113] In the embodiment, as shown in Fig. 2B, an example has been shown in which the birefringent plate 43 is housed inside the third housing 41 of the light-collecting optical unit 40. However, the position of the birefringent plate 43 is not particularly limited to this. For example, as shown in Figs. 15 to 17, the birefringent plate 43 may be housed inside an end cap 86 attached to the incident end 80A of an optical fiber 80.

[0114] As described above, the beam separation width d is determined by the material of the birefringent plate 43 and the wavelength of the laser light having the plate thickness t. Therefore, the birefringent plate 43 may be disposed closer to the incident end face 80A1 of the optical fiber 80 than in the case shown in FIG. 2B. Furthermore, when the birefringent plate 43 is attached to the end cap 86, the laser light LB, and in turn the processing laser light LB, can be transmitted without changing the configuration of the laser oscillator 90. P In addition, even if the optical fiber 80 is replaced with one having different specifications, the beam profile of the processing laser light LB can be easily changed. PThe beam profile can be changed. For example, when replacing the optical fiber 80 with one in which the diameter D2 of the first ring cladding 82 or the diameter D3 of the ring core 83 is increased, the beam separation width d must also be increased, as is clear from equation (4). In this case, as shown in FIG. 16, the beam separation width d can be easily increased by attaching a birefringent plate 43 with a thickness t1 (>t) to the end cap 86.

[0115] Furthermore, the end cap 86 is configured to be detachable from the optical fiber 80. Therefore, even if either the optical fiber 80 or the birefringent plate 43 is damaged, the end cap 86 can be removed from the optical fiber 80 and the damaged part can be easily replaced. In other words, the maintenance time for the laser oscillator 90 and the laser processing device 200 can be shortened.

[0116] 17, the quartz block 85 fused to the incident end surface 80A1 of the optical fiber 80 may be omitted. Since the optical path length of the first laser light LB1 and the second laser light LB2 from the birefringent plate 43 to the incident state into the optical fiber 80 can be shortened, the first laser light LB1 and the second laser light LB2 are reliably incident into the optical fiber 80 even if the quartz block 85 is omitted.

[0117] <Variation 4> FIG. 18 is a schematic cross-sectional view of a main part of a laser oscillator according to the fourth modification.

[0118] The laser oscillator 90 of this modification shown in FIG. 18 differs from the laser oscillator 90 of the third modification shown in FIGS.

[0119] 18, the birefringent plate 43 may be arranged, and in this case too, the laser light LB is split into a first laser light LB1 and a second laser light LB2 according to the polarization direction of the incident laser light LB, and these are incident on the center core 81 and the ring core 83. Therefore, according to the polarization direction of the laser light LB incident on the birefringent plate 43, the laser light LB, and further the processing laser light LB P The beam profile can be continuously changed.

[0120] In this modified example, the birefringent plate 43 is housed in an end cap 86 attached to the optical fiber 80. However, the birefringent plate 43 may be housed inside the third housing 41 of the light-collecting optical unit 40.

[0121] Furthermore, in this modified example, there is no air between the birefringent plate 43 and the incident end surface 80A1 of the optical fiber 80. Therefore, the first laser beam LB1 is incident on the center core 81 along the traveling direction of the laser beam LB, while the second laser beam LB2 is incident on the ring core 83 at a predetermined angle with respect to the traveling direction of the first laser beam LB1. In other words, similar to the case where the Rochon prism 44 is used, the numerical aperture of the second laser beam LB2 emitted from the optical fiber 80 is larger than the numerical aperture of the first laser beam LB1. Taking this into consideration, the optical components inside the laser head 100 need to be appropriately designed.

[0122] <Variation 5> Fig. 19 is a schematic configuration diagram of a laser processing device according to Modification 5. Fig. 20 is a schematic configuration diagram of a main part of a laser oscillator according to Modification 5. For ease of explanation, the first folding mirror 22 is not shown in Fig. 20.

[0123] The laser processing apparatus 200 of this modified example shown in FIG. 19 differs from the laser processing apparatus 200 of the embodiment shown in FIG. 1 in that two laser modules 10 are provided.

[0124] 20, laser light LB is incident from each of first light inlet 21A1 and second light inlet 21A2 provided in second housing 21. Laser light LB incident from first light inlet 21A1 travels in the Y direction. Laser light LB incident from second light inlet 21A2 travels in the Y direction, and is then reflected by reflecting mirror 27, and its traveling direction is changed to the Z direction.

[0125] The laser light LB incident from the first light entrance port 21A1 passes near the spatial combining mirror 28 and enters the polarizing beam splitter 24. The laser light LB reflected by the reflecting mirror 27 is reflected by the spatial combining mirror 28 and its traveling direction is changed again to the Y direction, after which it enters the polarizing beam splitter 24.

[0126] At the point of time when passing through the spatial combining mirror 28, the laser light LB incident from the first light entrance 21A1 and the laser light LB incident from the second light entrance 21A2 are spatially combined so that their optical axes approach each other. The two laser lights after spatial combination are combined into a combined laser light LB C The combined laser light LB C The two laser beams LB contained in the laser beam LB have the same polarization direction. C The polarization direction of the laser beam LB can be considered to be the same as the polarization direction of the laser beam LB.

[0127] Combined laser light LB C The first laser beam LB1 has its polarization direction changed by passing through the half-wave plate 31 of the polarization adjustment mechanism 30. After being collected by the collecting lens 42, the first laser beam LB1 is split into the first laser beam LB1 and the second laser beam LB2 by the birefringent plate 43. In this case, the first laser beam LB1 contains the ordinary rays of the two laser beams LB after passing through the birefringent plate 43. The second laser beam LB2 contains the extraordinary rays of the two laser beams LB after passing through the birefringent plate 43.

[0128] According to this modification, two laser beams LB are spatially combined to form a combined laser beam LB C By generating the laser beam LB for processing PIn addition, similar to the configuration shown in the embodiment, the combined laser light LB C , and thus the processing laser light LB P The beam profile can be continuously changed.

[0129] The two laser beams LB are polarization-combined to form a combined laser beam LB C It is difficult to apply the method of generating a laser beam LB having a polarization direction different from that of the first laser beam LB1 to this modified example. Polarization combining is a method of combining two laser beams LB having different polarization directions by using a polarization beam combiner or the like so that the optical axes of the two laser beams LB are aligned. For example, if the polarization directions of the two laser beams LB are orthogonal, the orthogonal polarization directions are maintained even after passing through the half-wave plate 31, and therefore, even if the half-wave plate 31 is rotated, the ratio of the light intensities of the first laser beam LB1 and the second laser beam LB2 emitted from the birefringent plate 43 does not change.

[0130] In this modification, the laser processing apparatus 200 is shown to include two laser modules 10, but the number of laser modules 10 is not particularly limited to this. Laser beams LB that are linearly polarized in the same direction are emitted from the multiple laser modules 10, and these beams are spatially combined to produce combined laser beams LB. C is generated.

[0131] (Other embodiments) New embodiments can also be created by appropriately combining the components shown in the embodiment and modifications 1 to 5. For example, the polarization adjustment mechanism 30 shown in modification 1 may be applied to the laser oscillator 90 shown in modifications 2 to 5. Furthermore, the half-wave plate 36 shown in modification 2 may be applied to the laser oscillator 90 shown in the embodiment and modifications 3 to 5. Furthermore, in modification 5, the birefringent plate 43 may be replaced with a Rochon prism 44 or a Wollaston prism shown in FIG. 8.

[0132] Furthermore, in the embodiment and modifications 1 to 5, an example has been shown in which a wave plate is used as the first optical element for changing the polarization direction of the laser light LB, but this is not particularly limited thereto. For example, a liquid crystal element may be used as the first optical element. The polarization direction of the laser light LB can be changed by changing the voltage applied to the liquid crystal element. However, if the output of the laser light LB is too high, the liquid crystal element may be damaged. Therefore, the type of the first optical element must be determined taking into consideration the resistance to the laser light LB and the output of the laser light LB.

[0133] Furthermore, it is preferable that an anti-reflection coating be applied to the transmission surface of the laser light LB in any optical element through which the laser light LB passes, not just the birefringent plate 43. By applying an anti-reflection coating, unwanted reflection of the laser light LB, the first laser light LB1, and the second laser light LB2 can be prevented, and the output loss of the first laser light LB1 and the second laser light LB2 until they enter the optical fiber 80 can be reduced. [Industrial Applicability]

[0134] The laser oscillator of the present disclosure is useful when applied to a laser processing device, since it can continuously change the beam profile of laser light emitted from an optical fiber to obtain a desired beam profile. [Explanation of symbols]

[0135] 10 Laser Module 11 First cabinet 11A light exit 20 Beam Shaper 21 Second cabinet 21A light entrance 21A1 1st light entrance 21A2 2nd light entrance 21B Light exit port 22 First folding mirror 23 Beam forming section 24 Polarizing beam splitter (third optical element) 25 Damper 26 Second folding mirror 27 Reflective mirror 28 Space Synthesis Mirror 30 Polarization adjustment mechanism 31 Half-wave plate 32 Rotation mechanism 33 Slide mechanism 33A 1st opening 33B 2nd opening 33C 3rd opening 34 Half-wave plate (first optical element) 34A 1st crystal plate 34B 2nd crystal plate 35 1 / 4 wave plate (first optical element) 36 Half-wave plate (first optical element) 36A 3rd crystal plate 36B 4th crystal plate 40 Condenser optical unit 41 Third cabinet 41A Light entrance 41B Light exit port 42 Condenser lens 43 Birefringent plate (second optical element) 44 Rochon prism (second optical element) 50 5th cabinet 60 Control Unit 70 Power supply 80 Optical Fiber 80A input end 80A1 Incidence end face 80B Output end 81 Center Core 82 First Ring Clad 83 Ring Core 84 Second Ring Clad 85 Quartz Block 86 End Cap 90 Laser Oscillator 100 laser head 110 4th cabinet 110A light entrance 110B Light exit port 120 Collimating Lens 130 Condenser Lens 140 Protective Glass 200 Laser processing equipment LB laser light LB1 first laser beam LB2 second laser beam LB C Combined laser light LB P Laser beam for processing

Claims

1. A laser oscillator comprising at least a laser light source that emits linearly polarized laser light, a condenser lens that condenses the laser light, and an optical fiber having two cores and into which the laser light condensed by the condenser lens is incident, a polarization adjustment mechanism that is disposed between the laser light source and the condenser lens, that is configured to be able to change the polarization direction of the laser light, and that has a first optical element; a second optical element disposed between the condenser lens and the optical fiber and configured to be able to split the laser light into a first laser light and a second laser light traveling along different optical paths, a second optical element configured to change the ratio of the amount of light between the first laser light and the second laser light depending on the polarization direction of the laser light transmitted through the first optical element;

2. 2. The laser oscillator according to claim 1, the polarization adjustment mechanism is configured to be able to rotate the first optical element around an optical axis of the incident laser light, the polarization direction of the laser light transmitted through the first optical element is continuously changed according to a rotation angle of the first optical element with respect to an initial position, a second optical element configured to continuously change the ratio of the amount of light between the first laser light and the second laser light depending on the polarization direction of the laser light transmitted through the first optical element;

3. 2. The laser oscillator according to claim 1, the polarization adjustment mechanism is configured to be able to change the polarization direction of the laser light emitted from the second optical element in a stepwise manner, a second optical element configured to gradually change the ratio of the amount of light between the first laser light and the second laser light depending on the polarization direction of the laser light transmitted through the first optical element;

4. 2. The laser oscillator according to claim 1, a third optical element disposed between the laser light source and the first optical element, the third optical element transmitting only a predetermined polarization component contained in the laser light;

5. 2. The laser oscillator according to claim 1, A laser oscillator, wherein the condenser lens and the second optical element are housed inside the same housing.

6. 2. The laser oscillator according to claim 1, 2. A laser oscillator according to claim 1, wherein the second optical element is accommodated in a container attached to the input end of the optical fiber.

7. 2. The laser oscillator according to claim 1, The laser oscillator is characterized in that the second optical element is fused to the incident end face of the optical fiber.

8. 2. The laser oscillator according to claim 1, 10. A laser oscillator, wherein the first optical element is a half-wave plate.

9. 2. The laser oscillator according to claim 1, 10. A laser oscillator, wherein the first optical element is a liquid crystal element.

10. 9. The laser oscillator according to claim 8, 1. A laser oscillator, wherein the half-wave plate is formed by overlapping two transparent plates having different thicknesses.

11. 11. The laser oscillator according to claim 10, 10. A laser oscillator, wherein the polarization adjustment mechanism is capable of changing the polarization direction of the laser light continuously or stepwise.

12. 2. The laser oscillator according to claim 1, 2. A laser oscillator, wherein the second optical element is a birefringent plate.

13. 2. The laser oscillator according to claim 1, 10. A laser oscillator, wherein the second optical element is a Wollaston prism or a Rochon prism.

14. 2. The laser oscillator according to claim 1, the optical fiber has at least a center core provided at an axis, a ring core that is ring-shaped in cross section and provided at a distance from the center core in the radial direction, and a first ring clad that is ring-shaped in cross section and provided between the center core and the ring core, the first laser light is incident on the center core, A laser oscillator, wherein the second laser light is incident on the ring core.

15. 15. The laser oscillator according to claim 14, When a beam separation width between the first laser light and the second laser light emitted from the second optical element is d, a diameter of the center core is D1, a diameter of the first ring clad is D2, and the diameter of the ring core is D3, the relationship shown in formula (3) is satisfied, .......................................... ０ ≦) ≦ ( ０ ・・・()) A ０ is a spot diameter of the first laser beam and the second laser beam on the incident end face of the optical fiber.

16. A laser oscillator according to any one of claims 1 to 15; a laser head attached to the output end of the optical fiber, The laser processing device is characterized in that the laser light guided by the optical fiber is irradiated from the laser head toward a workpiece.

17. 17. The laser processing apparatus according to claim 16, a beam shaper having a second housing and into which the laser light is incident from the laser light source; a focusing optical unit having a third housing and causing the laser light emitted from the beam shaper to enter the optical fiber, The laser processing device is characterized in that the condenser lens is housed inside the third housing.

18. 18. The laser processing apparatus according to claim 17, a plurality of the laser light sources; the beam shaper spatially combines the laser beams emitted from the plurality of laser light sources so that their optical axes approach each other to generate a combined laser beam; the combined laser light is linearly polarized; The laser processing apparatus is characterized in that the combined laser light incident on the focusing optical unit is transmitted through the second optical element and then incident on the optical fiber.

Images