Laser processing head and laser processing device including the same

Abstract

To provide a laser processing head which can condense laser beams having different wavelengths at the same condensed position with a simple configuration.SOLUTION: A laser processing head 50 includes a housing 51 to which an optical fiber 40 is connected, and a collimation lens 52 and a focus lens 53 in the inside of the housing 51. The optical fiber 40 has a first core 41 and a second core 43. A first laser beam LB1 (wavelength λ1) is guided to the first core 41, and a second laser beam LB2 (wavelength λ2<λ1) is guided to the second core 43. The first laser beam LB1 permeates through central parts 52A and 53A of the collimation lens 52 and the focus lens 53, and the second laser beam LB2 permeates through outer peripheral parts 52B and 53B. The central part 52A has a radius of curvature different from that of the outer peripheral part 52B, and the central part 53A has a radius of curvature different from that of the outer peripheral part 53B.SELECTED DRAWING: Figure 5

Description

[Technical field]

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

[0002] In recent years, in laser processing such as welding and cutting of copper materials, a so-called hybrid laser processing method has been put into practical use, which combines visible laser light, which has a high light absorption rate in copper, such as blue laser light or green laser light, with infrared laser light.

[0003] Conventionally, a laser processing device for performing hybrid laser processing has been proposed in which laser light of different wavelengths is guided to a laser processing head using different fibers, and then combined inside the laser processing head and irradiated onto a workpiece (see, for example, Patent Document 1).

[0004] Separately from this, a configuration has also been proposed in which laser beams of different wavelengths are guided to a laser processing head using a multicore fiber (see, for example, Patent Documents 2 and 3). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2022-088352 A [Patent Document 2] Patent Publication No. 2021-086840 [Patent Document 3] International Publication No. 2021 / 145358 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the conventional laser processing devices disclosed in Patent Documents 1 to 3 have the following problems. First, when two laser beams with different wavelengths are irradiated from a laser processing head toward a workpiece to be processed, a deviation occurs in the focusing position of each laser beam due to the influence of chromatic aberration of a lens arranged inside the laser processing head. In practice, in order to correct such a deviation, it is necessary to provide a mechanism for adjusting the focusing position of one of the laser beams inside or outside the laser processing head.

[0007] However, providing such an adjustment mechanism may increase the size of the laser processing head, complicate the laser processing head or the laser processing device, and increase costs due to the provision of the focusing position adjustment mechanism.

[0008] Next, in the conventional configurations disclosed in Patent Documents 1 and 2, it is necessary to provide an optical fiber separately for guiding laser beams of different wavelengths to the laser processing head. For example, in the configuration disclosed in Patent Document 1, a total of two optical fibers are required to guide two laser beams of different wavelengths to the laser processing head.

[0009] However, because these optical fibers guide high-power laser light, they deteriorate over time and must be replaced periodically. In other words, the initial cost and running cost required for maintenance increase according to the number of optical fibers that guide the laser light. In addition, when connecting multiple optical fibers to a laser processing head, a connection mechanism must be provided for each optical fiber, which may increase the size of the laser processing head.

[0010] The present disclosure has been made in consideration of these points, and its purpose is to provide a laser processing head and a laser processing apparatus equipped with the same that are capable of focusing laser light of different wavelengths at the same focusing position with a simple configuration. [Means for solving the problem]

[0011] In order to achieve the above object, a laser processing head according to the present disclosure is a laser processing head including a housing and a plurality of optical components arranged inside the housing, the housing has a fiber connection port and a light exit port, an optical fiber is connected to the fiber connection port, the optical fiber has at least a first core provided at an axial center and a second core provided radially outward of the first core and coaxially with the first core, a first laser light having a first wavelength is guided to the first core, a second laser light having a second wavelength shorter than the first wavelength is guided to the second core, at least one of the first laser light and the second laser light is emitted from the light exit port toward a workpiece, the plurality of optical components include at least a collimation lens and a focus lens, The collimation lens collimates the first laser light or the second laser light, or both, guided into the inside of the housing by the optical fiber, and the focus lens focuses the first laser light and the second laser light collimated by the collimation lens so that they are focused at the same focusing position on the machining surface of the workpiece or in the vicinity of the machining surface, the collimation lens and the focus lens are each aspheric lenses, the first laser light passes through a central portion of each of the collimation lens and the focus lens, and the second laser light passes through an outer periphery of each of the collimation lens and the focus lens, and the radius of curvature of the central portion of each of the collimation lens and the focus lens is different from the radius of curvature of the outer periphery.

[0012] The laser processing apparatus according to the present disclosure is characterized by comprising at least the laser processing head, a first laser oscillator that generates the first laser light, a second laser oscillator that generates the second laser light, an optical coupler that receives at least one of the first laser light and the second laser light and causes the first laser light to be incident on the first core and the second laser light to be incident on the second core, and an optical fiber that is connected to the optical coupler and the laser processing head and guides at least one of the first laser light and the second laser light from the optical coupler to the laser processing head. Effect of the Invention

[0013] According to the present disclosure, it is possible to focus laser beams of different wavelengths at the same focusing position with a simple configuration, and it is also possible to prevent the laser processing head from becoming large. [Brief description of the drawings]

[0014] [Figure 1] 1 is a schematic configuration diagram of a laser processing device according to an embodiment. [Diagram 2] FIG. 2 is a schematic diagram of an optical fiber as viewed from an input end. [Diagram 3] FIG. 2 is a schematic diagram of a main part of an optical coupler. [Figure 4] FIG. 2 is a schematic diagram of a laser processing head. [Diagram 5] FIG. 5 is an enlarged view of the portion surrounded by the dashed line in FIG. 4. [Figure 6] FIG. 1 is a diagram showing the wavelength dependence of light absorptance in various metals. [Figure 7] 4 is a schematic diagram showing the power density distribution of a first laser beam and a second laser beam in the vicinity of an output end of an optical fiber. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] 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 illustrative in nature and is not intended to limit the present disclosure, its application, or its uses.

[0016] (Embodiment) [Laser processing equipment configuration] Fig. 1 is a schematic diagram of a laser processing device according to this embodiment. Fig. 2 is a schematic diagram of an optical fiber viewed from the incident end. The laser processing device 100 includes a first laser oscillator 10, a second laser oscillator 20, an optical coupler 30, an optical fiber 40, a laser processing head 50, a manipulator 60, a control unit 70, and a stage 90. For ease of explanation, the shape of the laser processing head 50 is simplified in Fig. 1.

[0017] In the following description, the traveling direction of the laser light irradiated from the laser processing head 50 to the workpiece 80 may be referred to as the Z direction. In addition, in Fig. 1, the direction from the optical coupler 30 toward the laser processing head 50 may be referred to as the X direction, and the direction perpendicular to the X direction and the Z direction may be referred to as the Y direction.

[0018] In this specification, "same," "orthogonal," or "parallel" means the same, or orthogonal, or parallel, including the manufacturing tolerance of each part in the laser processing apparatus 100 and the allowable tolerance of the positional relationship of each part, and does not mean that the two objects being compared are the same, or orthogonal, or parallel in the strict sense.

[0019] Furthermore, when laser processing the workpiece 80, the first laser beam LB1 and the second laser beam LB2 are irradiated along a processing line (not shown) on the processing surface 80A of the workpiece 80.

[0020] The first laser oscillator 10 emits a first laser light LB1. In this embodiment, the wavelength λ1 of the first laser light LB1 is 975 nm. The wavelength λ1 of the first laser light LB1 is not particularly limited to this. The first laser light LB1 may be a laser light in the near-infrared or infrared wavelength region. The wavelength λ1 may be appropriately selected within the range of 800 nm or more and 1200 nm or less.

[0021] The second laser oscillator 20 emits the second laser light LB2. In this embodiment, the wavelength λ2 of the second laser light LB2 is 450 nm. The wavelength λ2 of the second laser light LB2 is not particularly limited to this. The second laser light LB2 may be a laser light in the near ultraviolet or visible light wavelength region. The wavelength λ2 may be appropriately selected within the range of 380 nm or more and 660 nm or less.

[0022] The first laser oscillator 10 and the second laser oscillator 20 each have a laser light source and a power source (not shown). Based on a control signal from the control unit 70, the respective power sources are driven to operate the laser light sources and generate the first laser light LB1 and the second laser light LB2, respectively. The laser light source may be composed of one or more semiconductor laser elements, or may be a solid-state laser or a fiber laser. Note that the semiconductor laser element is preferably a laser diode bar having a plurality of emitters that each emits laser light.

[0023] The optical coupler 30 is connected to the optical fiber 40, receives the first laser light LB1 emitted from the first laser oscillator 10, and makes the first laser light LB1 incident on a first core 41 (see FIGS. 2 and 3) of the optical fiber 40. The optical coupler 30 also receives the second laser light LB2 emitted from the second laser oscillator 20, and makes the second laser light LB2 incident on a second core 43 (see FIGS. 2 and 3) of the optical fiber 40. The configuration of the optical coupler 30 will be described in detail later.

[0024] As shown in FIG. 2, the optical fiber 40 has at least a first core 41 and a second core 43, each of which is an optical waveguide, and a first clad 42 and a second clad 44, and the outer surface of the second clad 44 is covered with a light-shielding coating (not shown).

[0025] When viewed from the incident end 40A of the optical fiber 40 (see FIG. 3), the first core 41 is circular and disposed at the axis of the optical fiber 40. The first clad 42 is in contact with the outer peripheral surface of the first core 41 and disposed coaxially with the first core 41, and is ring-shaped when viewed from the incident end 40A. The second core 43 is in contact with the outer peripheral surface of the first clad 42 and disposed coaxially with the first core 41, and is ring-shaped when viewed from the incident end 40A. The second clad 44 is in contact with the outer peripheral surface of the second core 43 and disposed coaxially with the first core 41, and is ring-shaped when viewed from the incident end 40A.

[0026] The first core 41, the second core 43, the first cladding 42, and the second cladding 44 are all made of quartz. However, the refractive index of the first cladding 42 is set to be lower than the refractive indexes of the first core 41 and the second core 43. In addition, the refractive index of the second cladding 44 is set to be lower than the refractive index of the second core 43.

[0027] In addition, the optical characteristics of the first core 41 are preferably adjusted so that the transmission loss of the first laser light LB1 is minimized or extremely small, and the optical characteristics of the second core 43 are preferably adjusted so that the transmission loss of the second laser light LB2 is minimized or extremely small. From another perspective, the optical characteristics of the first core 41 are preferably adjusted so that the transmission loss of the second laser light LB2 is smaller than the transmission loss of the first laser light LB1. The optical characteristics of the second core 43 are preferably adjusted so that the transmission loss of the first laser light LB1 is smaller than the transmission loss of the second laser light LB2. The adjustment of these optical characteristics is performed, for example, by appropriately setting the amount of impurity introduced into the first core 41, the second core 43, the first cladding 42, and the second cladding 44. In addition, the adjustment is performed by appropriately setting the refractive index difference between the first core 41 and the first cladding 42 and the refractive index difference between the second core 43 and the first cladding 42 and the second cladding 44.

[0028] The laser processing head 50 receives the first laser light LB1 and the second laser light LB2 guided by the optical fiber 40, and further irradiates the first laser light LB1 and the second laser light LB2 toward the workpiece 80. The structure of the laser processing head 50 will be described in detail later.

[0029] The manipulator 60 has an arm 61. The laser processing head 50 is attached to the tip of the arm 61. The arm 61 is divided into a plurality of sections, and a joint shaft 62 is provided at each connecting portion of each section.

[0030] Based on a control signal from the control unit 70, the manipulator 60 moves the laser processing head 50 along the processing line described above, and changes the position of the laser processing head 50 with respect to the workpiece 80. In accordance with this operation, the irradiation positions of the first laser beam LB1 and the second laser beam LB2 on the processing surface 80A of the workpiece 80 move along the processing line, and laser processing is performed.

[0031] As described above, the control unit 70 controls the operation of each of the first laser oscillator 10 and the second laser oscillator 20. Specifically, the control unit 70 controls the timing and emission time of the start and stop of emission of the first laser light LB1, as well as the power of the first laser light LB1. The control unit 70 also controls the timing and emission time of the start and stop of emission of the second laser light LB2, as well as the power of the second laser light LB2.

[0032] Moreover, the control unit 70 is connected to the manipulator 60 and the optical coupler 30, and controls the operation of the manipulator 60 and the operation of an actuator 33 (see FIG. 3) which will be described later.

[0033] The above-mentioned functions of the control unit 70 are realized by executing a predetermined machining program on the hardware of the control unit 70. The hardware is composed of one or more central processing units (CPUs) and memories. The memories are, for example, semiconductor memories such as random access memories (RAMs) and solid state drives (SSDs). The memories may also be read only memories (ROMs) or RAMs built into the CPUs.

[0034] 1 shows an example in which the control unit 70 controls the operations of the first laser oscillator 10, the second laser oscillator 20, the manipulator 60, and the optical coupler 30. However, a control unit 70 may be provided separately for each device. In that case, a host control unit may be provided that operates the multiple control units 70 in cooperation with each other based on a predetermined processing program.

[0035] The position of the workpiece 80 relative to the laser processing device 100 is determined by placing the workpiece 80 on the stage 90. After the positioning of the workpiece 80 is completed, the workpiece 80 is laser processed in accordance with a predetermined processing program. In this case, whether the laser processing is performed using only the first laser light LB1, or only the second laser light LB2, or both the first laser light LB1 and the second laser light LB2 is appropriately changed depending on the material of the workpiece 80 and the processing mode.

[0036] In this embodiment, the stage 90 is fixed and stationary at one location, but the stage 90 may be configured to be movable along an XY plane including the X and Y directions by providing a stage movement mechanism (not shown) on the stage 90. In this case, the position of the manipulator 60, in other words, the position of the laser processing head 50, may be fixed.

[0037] [Optical coupler configuration] 3 is a schematic diagram of the main parts of an optical coupler 30. The optical coupler 30 has a housing 31 and a plurality of components arranged in a predetermined positional relationship inside the housing 31. The plurality of components include a reflecting mirror 32, an actuator 33, a dichroic mirror 34, and a first focus lens 35.

[0038] The housing 31 has a first light inlet 31A (see FIG. 1), a second light inlet 31B (see FIG. 1), and a light outlet 31C. As shown in FIG. 1, a first laser light LB1 is incident from the first laser oscillator 10 into the inside of the housing 31 through the first light inlet 31A. Also, a second laser light LB2 is incident from the second laser oscillator 20 into the inside of the housing 31 through the second light inlet 31B.

[0039] An optical fiber 40 is connected to the light exit port 31C. A quartz block 36 for adjusting the refractive index is welded to an incident end 40A of the optical fiber 40, and the first laser light LB1 and the second laser light LB2 are transmitted through the quartz block 36 and are incident on the incident end 40A of the optical fiber 40.

[0040] Although not shown, the first light inlet 31A is sealed with a member such as quartz glass that is transparent to the first laser light LB1. Similarly, the second light inlet 31B is sealed with a member such as quartz glass that is transparent to the second laser light LB2. The arrangement of the first light inlet 31A and the second light inlet 31B may be different from the example shown in Fig. 1. In that case, a component that changes the optical path of the first laser light LB1 and the second laser light LB2 is provided inside the housing 31.

[0041] The reflecting mirror 32 reflects the second laser light LB2 incident inside the housing 31 toward the incident end 40A of the optical fiber 40. The actuator 33 is attached to the reflecting mirror 32, and adjusts the angle of the reflecting mirror 32 with respect to the optical axis of the second laser light LB2 based on a control signal from the control unit 70. When the second laser light LB2 reflected by the reflecting mirror 32 is not incident on the second core 43 at the incident end 40A, the actuator 33 is operated to adjust the angle of the reflecting mirror 32 so that the second laser light LB2 is incident on the second core 43. The actuator 33 is, for example, a piezo motor, but is not particularly limited thereto.

[0042] The dichroic mirror 34 is an optical component configured to transmit light in the visible wavelength range including the wavelength λ2 of the second laser light LB2, while reflecting light in the near-infrared and infrared wavelength range including the wavelength λ1 of the first laser light LB1. Specifically, dielectric films having different refractive indices are formed on the surface of the dichroic mirror 34, and the type, film thickness, and number of layers are adjusted to obtain the above-mentioned optical characteristics.

[0043] The dichroic mirror 34 is disposed on the optical path of the second laser light LB2 reflected by the reflecting mirror 32 and on the optical path of the first laser light LB1 incident on the inside of the housing 31. The second laser light LB2 transmitted through the dichroic mirror 34 and the first laser light LB1 reflected by the dichroic mirror 34 travel toward the first focus lens 35 with their optical axes approaching each other.

[0044] The first focus lens 35 focuses the incident first laser light LB1 and second laser light LB2, respectively, and makes them incident on the incident end 40A of the optical fiber 40. As described above, at the incident end 40A, the first laser light LB1 is focused by the first focus lens 35 so as to be incident on the first core 41, and the second laser light LB2 is focused on the second core 43.

[0045] The first laser light LB1 is guided by the first core 41 and the second laser light LB2 is guided by the second core 43, respectively, and enters the laser processing head 50.

[0046] The optical fiber 40 is attached to the housing 31 so as to be movable in each of the X direction, Y direction, and Z direction to such an extent that the optical fiber 40 does not fall out of the light exit port 31C. When the first laser light LB1 is not incident on the first core 41 at the incident end 40A, the position of the optical fiber 40 is adjusted so that the first laser light LB1 is incident on the first core 41.

[0047] [Laser processing head configuration] Fig. 4 is a schematic diagram of a laser processing head, and Fig. 5 is an enlarged view of a portion surrounded by a dashed line in Fig. 4.

[0048] In Fig. 4, for the sake of convenience, the shapes of the components constituting the laser processing head 50 are shown in a simplified manner. Also, the cross-sectional structure of the optical fiber 40 is not shown. Components other than those shown in Fig. 4 may be disposed inside the housing 51 or attached to the outside of the housing 51.

[0049] 4, the laser processing head 50 has a housing 51 and a plurality of optical components arranged therein. The housing 51 has a fiber connection port 51A to which the emission end 40B of the optical fiber 40 is attached, and a light emission port 51B from which the first laser light LB1 and the second laser light LB2 are emitted.

[0050] Inside the housing 51, a collimation lens 52, a second focus lens 53, and a protective glass 54 are arranged in a predetermined positional relationship with each other in that order from the closest to the fiber connection port 51A. Note that optical components other than these may be arranged inside the housing 51. Note that in the following description, the second focus lens 53 may be simply referred to as the focus lens 53.

[0051] The collimation lens 52 receives and collimates the first laser light LB1 and the second laser light LB2 that enter the inside of the housing 51. The focus lens 53 receives the first laser light LB1 and the second laser light LB2 that have been collimated by the collimation lens 52, and focuses the light so as to form a focus on the processing surface 80A of the workpiece 80 or in the vicinity of the processing surface 80A. In other words, the focusing positions of the first laser light LB1 and the second laser light LB2 that have passed through the focus lens 53 are the processing surface 80A or in the vicinity of the processing surface 80A.

[0052] The protective glass 54 prevents sputters and fumes generated on the workpiece 80 irradiated with the first laser light LB1 and the second laser light LB2 from entering the inside of the housing 51. This prevents sputters and fumes from adhering to the optical components arranged inside the housing 51, deteriorating the optical properties of the optical components, and ultimately prevents a decrease in the power and beam quality of each of the first laser light LB1 and the second laser light LB2 irradiated to the workpiece 80.

[0053] Here, the shapes of the collimation lens 52 and the focus lens 53 through which the first laser beam LB1 and the second laser beam LB2 pass, respectively, will be further described.

[0054] 5, the collimation lens 52 is a lens having a convex emission surface (hereinafter referred to as a light emission surface) for the first laser light LB1 and the second laser light LB2, and the focus lens 53 is a lens having a convex incidence surface (hereinafter referred to as a light incidence surface) for the first laser light LB1 and the second laser light LB2.

[0055] However, in the collimation lens 52, the radius of curvature of the light exit surface is not uniform, and the lens is a so-called aspherical lens. Similarly, in the focus lens 53, the radius of curvature of the light entrance surface is not uniform, and the lens is a so-called aspherical lens.

[0056] Specifically, when the radius of curvature of the light exit surface at the central portion 52A of the collimation lens 52 is R1A and the radius of curvature of the light exit surface at the outer circumferential portion 52B is R1B, the relationship shown in formula (1) holds.

[0057] R1A ≠ R1B (1) Furthermore, when the radius of curvature of the light incident surface at the center portion 53A of the focus lens 53 is R2A and the radius of curvature of the light incident surface at the outer circumferential portion 53B is R2B, the relationship shown in formula (2) holds.

[0058] R2A ≠ R2B (2) In addition, when viewed in the optical axis direction of the first laser light LB1 and the second laser light LB2 directed from the collimation lens 52 to the focus lens 53, that is, in the Z direction in the example shown in Fig. 5, the outer circumferential portion 52B of the collimation lens 52 is disposed so as to surround the central portion 52A on the inside. Also, the outer circumferential portion 53B of the focus lens 53 is disposed so as to surround the central portion 53A on the inside. However, the outer circumferential portion 52B is continuous with the central portion 52A, and the outer circumferential portion 53B is continuous with the central portion 53A.

[0059] 5, the first laser light LB1 guided to the first core 41 disposed at the axial center of the optical fiber 40 passes through the central portions 52A and 53A. On the other hand, the second core 43 disposed on the outer periphery side of the first core 41 with the first cladding 42 in between is ring-shaped in cross section. For this reason, the second laser light LB2 guided to the second core 43 passes through the outer periphery portions 52B and 53B which surround the central portions 52A and 53A on the inside, respectively.

[0060] As shown in formula (1), the radius of curvature R1B of the light exit surface at the outer circumferential portion 52B of the collimation lens 52 is different from the radius of curvature R1A of the light exit surface at the central portion 52A. Also, as shown in formula (2), the radius of curvature R2B of the light entrance surface at the outer circumferential portion 53B of the focus lens 53 is different from the radius of curvature R2A of the light entrance surface at the central portion 53A.

[0061] When the first laser light LB1 and the second laser light LB2 are simultaneously irradiated from the laser processing head 50 toward the workpiece 80, they are affected by chromatic aberration when they pass through the collimation lens 52 and the focus lens 53. If the collimation lens 52 and the focus lens 53 are spherical lenses, the chromatic aberration causes the focusing position of the first laser light LB1 and the focusing position of the second laser light LB2 to differ on the processing surface 80A of the workpiece 80 or in the vicinity of the processing surface 80A.

[0062] Therefore, as shown in this embodiment, the radius of curvature R1B at the outer circumferential portion 52B is made different from the radius of curvature R1A at the central portion 52A in the collimation lens 52. Furthermore, the radius of curvature R2B at the outer circumferential portion 53B is made different from the radius of curvature R2A at the central portion 53A in the focus lens 53.

[0063] By doing this, the difference in refractive index at each lens that depends on the wavelength difference between the first laser light LB1 and the second laser light LB2 can be canceled, and the first laser light LB1 and the second laser light LB2 can be focused at the same focusing position.

[0064] In addition, in a lens that does not perform chromatic aberration correction, the focusing position of light with a short wavelength, in this case the second laser light LB2, is closer to the focus lens 53 than the focusing position of the first laser light LB1. Also, since the second laser light LB2 passes through the outer periphery side of each lens than the first laser light LB1, the focusing position of the second laser light LB2 is even closer to the focus lens 53.

[0065] On the other hand, in the optical fiber 40 having the structure shown in FIG. 2, the numerical aperture of the second laser light LB2 guided by the second core 43, i.e., the maximum emission angle of the second laser light LB2 emitted from the optical fiber 40, is larger than the numerical aperture of the first laser light LB1 guided by the first core 41. Therefore, the optical path length from the emission end 40B of the optical fiber 40 to the focusing position is longer for the second laser light LB2 than for the first laser light LB1. This acts in the direction in which the focusing position of the second laser light LB2 approaches the processing surface 80A of the workpiece 80. In addition, the difference in the optical path length also depends on the size of each component inside the laser processing head 50.

[0066] The ratio between the radius of curvature R1B and the radius of curvature R1A, and the ratio between the radius of curvature R2B and the radius of curvature R2A are appropriately set in consideration of the above-mentioned various factors.

[0067] [About hybrid laser processing method] Fig. 6 is a diagram showing the wavelength dependence of light absorptance in various metals Fig. 7 is a schematic diagram showing the power density distribution of the first laser beam and the second laser beam in the vicinity of the output end of the optical fiber.

[0068] In general, when a metal is irradiated with light, the proportion of the light absorbed by the metal, i.e., the light absorptance, varies depending on the wavelength of the light. Furthermore, the wavelength dependency of the light absorptance varies greatly depending on the metal material.

[0069] For example, in iron and nickel, the optical absorptance increases as the wavelength becomes shorter, but the degree of change in optical absorptance with respect to wavelength is gradual, as shown in Fig. 6. Taking iron as an example, the optical absorptance at the wavelength λ1 (=975 nm) of the first laser light LB1 is 40%, and the optical absorptance at the wavelength λ2 (=450 nm) of the second laser light LB2 is about 45%.

[0070] On the other hand, in copper, the optical absorptance increases rapidly when the wavelength enters the visible light wavelength range. As shown in Fig. 6, the optical absorptance of the first laser light LB1 at the wavelength λ1 is less than 10%, while the optical absorptance of the second laser light LB2 at the wavelength λ2 increases to about 60%.

[0071] For this reason, when the workpiece 80 is a plate material made of copper, it is more advantageous to perform laser processing using the second laser light LB2. On the other hand, the power of the second laser light LB2, which is usually blue light, is lower than the power of the first laser light LB1, which is near-infrared light. This is due to the difference in performance between the laser light source that emits the second laser light LB2 and the laser light source that emits the first laser light LB1. When the laser light source that emits the second laser light LB2 is composed of a semiconductor laser element, this difference in performance becomes particularly large. If the number of laser light sources included in the second laser oscillator 20 is increased, this difference in performance can be reduced, but the second laser oscillator 20 will become larger and the input power will become larger.

[0072] Therefore, as shown in Patent Documents 1 to 3, a so-called hybrid laser processing method has been adopted in which a visible laser beam and an infrared laser beam are combined and irradiated onto the workpiece 80.

[0073] Using the laser processing apparatus 100 of this embodiment, the first laser light LB1 and the second laser light LB2 are simultaneously irradiated onto the workpiece 80, which is a copper plate material. In this case, the second laser light LB2 is irradiated coaxially with the first laser light LB1 on the processing surface 80A of the workpiece 80. Also, as shown in FIG. 7, the power distribution of the first laser light LB1 emitted from the emission end 40B of the optical fiber 40 has a single-peaked peak. Also, the second laser light LB2 has a peak lower than the first laser light LB1 outside the first laser light LB1 so as to surround the peak of the first laser light LB1 on the inside. This is because the second core 43 is arranged coaxially with the first core 41 and is provided in a ring shape.

[0074] Therefore, the second laser light LB2 is focused at the same focusing position as the first laser light LB1 along the traveling direction from the laser processing head 50 toward the workpiece 80. On the other hand, on the processing surface 80A of the workpiece 80, the irradiation spot diameter D2 (see FIG. 4) of the second laser light LB2 is larger than the irradiation spot diameter D1 (see FIG. 4) of the first laser light LB1. For example, when the irradiation spot diameter D1 is about 50 μm, the irradiation spot diameter D2 is about 200 μm to 300 μm.

[0075] In this manner, the workpiece 80 made of copper is heated by the second laser light LB2 having a high light absorptance. When the workpiece 80 is heated to near its melting point by irradiation with the second laser light LB2, the light absorptance of the first laser light LB1 in the workpiece 80 increases significantly, so that the workpiece 80 is laser-machined smoothly in a short time by the high-power first laser light LB1.

[0076] Depending on the material and thickness of the workpiece 80 and the processing mode, the laser processing may be performed using only the first laser beam LB1, or the laser processing may be performed using only the second laser beam LB2.

[0077] [Effects, etc.] As described above, the laser processing head 50 according to this embodiment includes a housing 51 and a plurality of optical components disposed inside the housing 51. The housing 51 has a fiber connection port 51A and a light emission port 51B, and the optical fiber 40 is connected to the fiber connection port 51A.

[0078] The optical fiber 40 has at least a first core 41 provided at the axis, and a second core 43 provided radially outside the first core 41 and coaxially with the first core 41. A first laser light LB1 having a first wavelength (wavelength λ1) is guided to the first core 41, and a second laser light LB2 having a second wavelength (wavelength λ2) shorter than the first wavelength is guided to the second core 43.

[0079] At least one of the first laser beam LB1 and the second laser beam LB2 is emitted toward the workpiece 80 from the light emission port 51B.

[0080] The multiple optical components include at least a collimation lens 52 and a focus lens (second focus lens) 53. The collimation lens 52 collimates the first laser light LB1 or the second laser light LB2, or both, guided into the inside of the housing 51 by the optical fiber 40. The focus lens 53 focuses the first laser light LB1 and the second laser light LB2 collimated by the collimation lens 52 to the same focusing position on the processing surface 80A of the workpiece 80 or in the vicinity of the processing surface 80A.

[0081] The collimation lens 52 and the focus lens 53 are each an aspheric lens. The first laser light LB1 passes through central portions 52A and 53A of the collimation lens 52 and the focus lens 53, respectively, and the second laser light LB2 passes through peripheral portions 52B and 53B of the collimation lens 52 and the focus lens 53, respectively.

[0082] In the collimation lens 52, a radius of curvature R1A of the central portion 52A is different from a radius of curvature R1B of the outer peripheral portion 52B. In the focus lens 53, a radius of curvature R2A of the central portion 53A is different from a radius of curvature R2B of the outer peripheral portion 53B.

[0083] By configuring the laser processing head 50 in this manner, the first laser light LB1 and the second laser light LB2, which are guided by the optical fiber 40, which is a multicore fiber, and have different wavelengths, can be focused to the same focusing position without providing a focusing position adjustment mechanism, etc. Also, when a focusing position adjustment mechanism is provided, labor is required to adjust the focusing position of one laser light in accordance with the other laser light, but according to this embodiment, such labor is not required.

[0084] Furthermore, according to this embodiment, there is no need to provide optical fibers for guiding laser light of different wavelengths, which makes it possible to prevent the laser processing head 50 from becoming large.

[0085] In addition, optical fibers deteriorate over long periods of use and must be replaced periodically. Although this depends on the power of the laser light used in the laser processing and the laser processing time, it is usually necessary to replace the optical fiber every one to two years.

[0086] According to this embodiment, the first laser light LB1 and the second laser light LB2, which have different wavelengths, are guided to the laser processing head 50 by a single optical fiber 40. This makes it possible to reduce the initial cost of installing the optical fiber and the running cost of replacing the optical fiber, compared to conventional laser processing heads that connect two optical fibers.

[0087] It is preferable that the first laser light LB1 is in the near-infrared or infrared wavelength range, and the second laser light LB2 is in the visible wavelength range. In this way, a laser light in a wavelength range that can obtain high power can be used as the first laser light LB1 that passes through the central parts 52A and 53A of the collimation lens 52 and the focus lens 53, respectively. As a wavelength range that is often actually used in laser processing, it is preferable that the wavelength λ1 of the first laser light LB1 is 800 nm or more and 1200 nm or less.

[0088] Moreover, the second laser light LB2 is irradiated around the first laser light LB1 on the machining surface 80A of the workpiece 80. As described above, when laser machining the workpiece 80 made of a material such as copper that has low light absorption rate for near-infrared or infrared light, the wavelength λ2 of the second laser light LB2 is preferably in the wavelength range of visible light or near-ultraviolet light that has high light absorption rate for the material. In other words, the wavelength λ2 of the second laser light LB2 is preferably 380 nm or more and 660 nm or less.

[0089] In addition, it is preferable that the optical characteristics of the optical fiber 40 connected to the laser processing head 50 are adjusted so that the first core 41 has a minimum or extremely small transmission loss of the first laser light LB1, and the second core 43 has a minimum or extremely small transmission loss of the second laser light LB2.

[0090] When laser beams of different wavelengths are guided to one core of the optical fiber 40, if the optical characteristics of the core are specified so that the transmission loss for one wavelength of light is minimal or extremely small, the transmission loss for the other wavelength of light becomes large. This tendency becomes particularly noticeable when the cable length of the optical fiber 40 becomes long. When high-power laser beams are required, such as in laser processing, large transmission loss may lead to heat generation or damage to the optical fiber 40.

[0091] On the other hand, according to the present embodiment, the first laser light LB1 and the second laser light LB2 are guided to the first core 41 and the second core 43, respectively, of the optical fiber 40. By appropriately setting the optical characteristics of the first core 41 and the second core 43, it is possible to reduce the loss of each of the first laser light LB1 and the second laser light LB2 transmitted to the optical fiber 40, and it is possible to perform laser processing of the workpiece 80 with the desired power.

[0092] The laser processing apparatus 100 according to this embodiment includes at least a laser processing head 50, a first laser oscillator 10, a second laser oscillator 20, an optical coupler 30, and an optical fiber 40.

[0093] The first laser oscillator 10 generates a first laser light LB1, and the second laser oscillator 20 generates a second laser light LB2.

[0094] The optical coupler 30 receives the first laser light LB1 and the second laser light LB2, and causes the first laser light LB1 to enter the first core 41 and the second laser light LB2 to enter the second core 43. When only the first laser light LB1 is generated, the optical coupler 30 causes the first laser light LB1 to enter the first core 41. When only the second laser light LB2 is generated, the optical coupler 30 causes the second laser light LB2 to enter the second core 43.

[0095] The optical fiber 40 is connected to the optical coupler 30 and the laser processing head 50 , and guides at least one of the first laser light LB1 and the second laser light LB2 from the optical coupler 30 to the laser processing head 50 .

[0096] By configuring the laser processing apparatus 100 in this manner, when laser processing the workpiece 80 using a first laser light LB1 and a second laser light LB2 having different wavelengths, the first laser light LB1 and the second laser light LB2 can be focused to the same focusing position without providing a focusing position adjustment mechanism or the like.

[0097] When the first laser beam LB1 and the second laser beam LB2 are simultaneously irradiated onto the workpiece 80, the second laser beam LB2 is irradiated coaxially with the first laser beam LB1 on the processing surface 80A of the workpiece 80. Furthermore, the irradiation spot diameter D2 of the second laser beam LB2 is larger than the irradiation spot diameter D1 of the first laser beam LB1.

[0098] In this way, when laser processing the workpiece 80 made of a material with low light absorptivity for the first laser beam LB1, the workpiece 80 can be heated to near its melting point by being absorbed by the second laser beam LB2. In addition, since the light absorptivity for the first laser beam LB1 increases rapidly in the heated portion, the workpiece 80 can be processed smoothly in a short time using the high-power first laser beam LB1.

[0099] Moreover, by making the irradiation spot diameter D2 larger than the irradiation spot diameter D1, the first laser light LB1 can be irradiated only to the portion heated by the second laser light LB2. This makes it possible to prevent the high-power first laser light LB1 from being directly irradiated to the workpiece 80 whose temperature has not risen sufficiently. If the high-power first laser light LB1 is irradiated to the workpiece 80 whose temperature has not risen sufficiently, the molten portion of the workpiece 80 may bump due to a sudden rise in temperature, causing spattering. According to this embodiment, the occurrence of such spattering can be suppressed.

[0100] The laser processing apparatus 100 further includes a control unit 70 that controls the operation of at least the optical coupler 30 .

[0101] The optical coupler 30 has at least a reflecting mirror 32, an actuator 33, and a dichroic mirror 34. The reflecting mirror 32 reflects the incident second laser light LB2 toward an incident end 40A of the optical fiber 40.

[0102] The actuator 33 is attached to the reflecting mirror 32 and adjusts the angle of the reflecting mirror 32 based on a control signal from the control unit 70 so that the second laser light LB2 is incident on the second core 43.

[0103] The dichroic mirror 34 is disposed on the optical path of the second laser light LB2 traveling from the reflecting mirror 32 toward the optical fiber 40, and on the optical path of the first laser light LB1. The dichroic mirror 34 is configured to transmit the incident second laser light LB2 and to reflect the incident first laser light LB1.

[0104] The first laser light LB1 reflected by the dichroic mirror 34 is incident on the first core 41 at the incident end 40A of the optical fiber 40. The second laser light LB2 transmitted through the dichroic mirror 34 is incident on the second core 43 at the incident end 40A of the optical fiber 40.

[0105] By configuring the optical coupler 30 in this manner, it is possible to make the first laser light LB1 enter the first core 41 and the second laser light LB2 enter the second core 43 reliably with a simple configuration.

[0106] (Other embodiments) The configuration of the optical coupler 30 is not particularly limited to that shown in Fig. 3. For example, as shown in Patent Document 3, an axicon lens may be used to make the first laser light LB1 incident on the first core 41 and the second laser light LB2 incident on the second core 43. Alternatively, a prism may be used to make the first laser light LB1 incident on the first core 41 and the second laser light LB2 incident on the second core 43. Alternatively, a diffraction grating may be used to make the first laser light LB1 incident on the first core 41 and the second laser light LB2 incident on the second core 43.

[0107] Moreover, it is preferable that the laser light sources constituting each of the first laser oscillator 10 and the second laser oscillator 20 are one or more semiconductor laser elements, in particular, laser diode bars each having a plurality of emitters that emit laser light. By configuring the laser light sources in this way, it is possible to miniaturize each of the first laser oscillator 10 and the second laser oscillator 20. Furthermore, since the semiconductor laser element has a high power-to-light conversion efficiency of about 40%, it is possible to generate high-power first laser light LB1 and second laser light LB2 with a small input power. [Industrial Applicability]

[0108] The laser processing head of the present disclosure has a simple configuration and is capable of focusing laser light of different wavelengths at the same focusing position, and is industrially useful. [Explanation of symbols]

[0109] 10 First laser oscillator 20 Second laser oscillator 30 Optical coupler 31 Case 31A 1st light entrance 31B 2nd light entrance 31C Light exit port 32 Reflective Mirror 33 Actuator 34 Dichroic Mirror 35 First focus lens 36 Quartz Block 40 Optical Fiber 40A input end 40B Output end 41 First Core 42 First Clad 43 Second Core 44 2nd Clad 50 Laser processing head 51 Case 51A Fiber connection port 51B Light exit port 52 Collimation Lens 52A Central part 52B Outer periphery 53 Second focus lens (focus lens) 53A Central part 53B Outer periphery 54 Protective Glass 60 Manipulator 61 Arm 62 Joint Axis 70 Control section 80 Work 80A machined surface 90 Stages 100 Laser processing equipment LB1 First laser beam LB2 Second laser beam λ1: Wavelength of the first laser light (first wavelength) λ2: Wavelength of the second laser light (second wavelength)

Claims

1. A laser processing head including a housing and a plurality of optical components disposed inside the housing, the housing has a fiber connection port and a light exit port, An optical fiber is connected to the fiber connection port, The optical fiber has at least a first core provided at an axis and a second core provided radially outward of the first core and coaxially with the first core; A first laser light having a first wavelength is guided to the first core, A second laser light having a second wavelength shorter than the first wavelength is guided to the second core, At least one of the first laser light and the second laser light is emitted from the light emission port toward a workpiece, The optical components include at least a collimation lens and a focus lens, the collimation lens collimates the first laser light or the second laser light, or both of the first laser light and the second laser light, which are guided into the housing by the optical fiber; The focus lens focuses the first laser light and the second laser light collimated by the collimation lens so that they are focused at the same focusing position on the processing surface of the workpiece or in the vicinity of the processing surface, the collimation lens and the focus lens are each an aspheric lens; the first laser light passes through a central portion of each of the collimation lens and the focus lens; the second laser light passes through outer peripheries of the collimation lens and the focus lens, A laser processing head, characterized in that the radius of curvature of the central portion of each of the collimation lens and the focus lens is different from the radius of curvature of the outer periphery.

2. 2. The laser processing head according to claim 1, The first wavelength is equal to or greater than 800 nm and equal to or less than 1200 nm, A laser processing head, wherein the second wavelength is 380 nm or more and 660 nm or less.

3. 2. The laser processing head according to claim 1, The optical fiber connected to the laser processing head is the first core is configured so that a transmission loss of the second laser light is minimized or extremely small, the second core is configured so that a transmission loss of the first laser light is minimized or extremely small, A laser processing head characterized in that each optical characteristic is adjusted.

4. A laser processing head according to any one of claims 1 to 3, a first laser oscillator that generates the first laser light; a second laser oscillator that generates the second laser light; an optical coupler that receives at least one of the first laser light and the second laser light and causes the first laser light to enter the first core and the second laser light to enter the second core; a first laser beam and a second laser beam, the first laser beam being guided from the first laser beam to the second laser beam; and an optical fiber connected to the optical coupler and the laser processing head, the optical fiber guiding at least one of the first laser beam and the second laser beam from the optical coupler to the laser processing head.

5. 5. The laser processing apparatus according to claim 4, When the first laser light and the second laser light are simultaneously irradiated onto the workpiece, A laser processing apparatus characterized in that the second laser light is irradiated coaxially with the first laser light on the processing surface of the workpiece, and the irradiation spot diameter of the second laser light is larger than the irradiation spot diameter of the first laser light.

6. 5. The laser processing apparatus according to claim 4, A control unit for controlling at least the operation of the optical coupler is further provided. the optical coupler includes at least a reflecting mirror, an actuator, and a dichroic mirror; the reflecting mirror reflects the incident second laser light toward an incident end of the optical fiber, the actuator is attached to the reflecting mirror, and adjusts an angle of the reflecting mirror based on a control signal from the control unit so that the second laser light is incident on the second core; the dichroic mirror is disposed on an optical path of the second laser light traveling from the reflecting mirror to the optical fiber and on an optical path of the first laser light, and is configured to transmit the second laser light incident thereon and to reflect the first laser light incident thereon; the first laser light reflected by the dichroic mirror is incident on the first core at the incident end, The laser processing apparatus, characterized in that the second laser light transmitted through the dichroic mirror is incident on the second core at the incident end.

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