Manufacturing method for products including laser processing heads, laser processing equipment, and metal joints.

Abstract

The laser processing head (17) includes a beam shaping optical system (14) into which laser light (13) is incident, a collimating optical system (15) into which laser light (13) that has passed through the beam shaping optical system (14) is incident, and a focusing optical system (16) into which laser light (13) that has passed through the collimating optical system (15) is incident. The beam shaping optical system (14) has an optical property in which, when a ray parallel to the central axis, which is the optical axis of the laser light (13), is incident at a position in the peripheral region, which is the region in which the distance from the central axis in a plane perpendicular to the central axis of the beam shaping optical system (14) exceeds a predetermined boundary value, the distance between the intersection point of the ray and the central axis and the beam shaping optical system (14) increases monotonically and nonlinearly as the ray height increases.

Description

[Technical Field]

[0001] This disclosure relates to a laser processing head for performing laser processing using laser light, a laser processing apparatus, and a method for manufacturing a product including a metal joint. [Background technology]

[0002] In recent years, near-infrared lasers, such as fiber lasers, YAG (Yttrium Aluminum Garnet) lasers, and direct diode lasers, have seen advancements in focusing and power output, leading to the development of laser processing heads and laser processing equipment that utilize near-infrared lasers as light sources.

[0003] Patent Document 1 discloses a material processing method that utilizes a laser with a variable beam shape. This material processing method adjusts the beam profile by dynamically changing the position of optical elements having planar and flat upper conical surfaces within the optical path of the laser beam, thereby varying the beam quality. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Special Publication No. 2019-523137 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] According to the material processing technology disclosed in Patent Document 1, processing may become unstable due to the beam profile. For example, if a truncated cone-shaped lens is placed in the optical path as an optical element for adjusting the beam profile, and the lens is moved along the optical axis, the beam gap, which is the area where the beam is absent between the circular beam in the central region of the beam profile and the ring-shaped beam in the peripheral region of the beam profile, may become larger. This beam gap becomes an unheated area of ​​the workpiece, which may lead to unstable laser processing.

[0006] As described above, the material processing technology disclosed in Patent Document 1 has a problem that laser processing becomes unstable due to the beam intensity distribution caused by the action of the variable beam optical system.

[0007] This disclosure has been made in view of the above, and an object thereof is to obtain a laser processing head that can contribute to realizing stable laser processing.

Means for Solving the Problems

[0008] In order to solve the above-described problems and achieve the object, the laser processing head according to the present disclosure includes a beam shaping optical system into which laser light is incident, a collimating optical system into which the laser light that has passed through the beam shaping optical system is incident, and a condensing optical system into which the laser light that has passed through the collimating optical system is incident. The beam shaping optical system has an optical characteristic in which, when a light beam parallel to the central axis, which is the optical axis of the laser light, is incident at a position where the distance from the central axis in a plane perpendicular to the central axis of the beam shaping optical system is the ray height in a peripheral region that is a region exceeding a predetermined boundary value, the distance between the intersection of the light beam and the central axis and the beam shaping optical system increases monotonically and non-linearly as the ray height increases.

Effects of the Invention

[0009] The laser processing head according to the present disclosure has an effect that it can contribute to realizing stable laser processing.

Brief Description of the Drawings

[0010] [Figure 1] A diagram schematically showing the configuration of a laser processing apparatus according to Embodiment 1 [Figure 2] A diagram schematically showing a flat center conical lens which is a first example of a beam shaping optical system in a laser processing apparatus according to Embodiment 1 [Figure 3]First figure showing an example of a two-dimensional intensity map of laser light at the focal point of a laser processing head when a flat center conical lens is used as the beam shaping optical system in the laser processing apparatus according to Embodiment 1 [Figure 4] Second figure showing an example of a two-dimensional intensity map of laser light at the focal point of a laser processing head when a flat center conical lens is used as the beam shaping optical system in the laser processing apparatus according to Embodiment 1 [Figure 5] Figure schematically showing a flat center horn-shaped lens which is a second example of the beam shaping optical system in the laser processing apparatus according to Embodiment 1 [Figure 6] First figure showing an example of a two-dimensional intensity map of laser light at the focal point of a laser processing head when a flat center horn-shaped lens is used as the beam shaping optical system in the laser processing apparatus according to Embodiment 1 [Figure 7] Second figure showing an example of a two-dimensional intensity map of laser light at the focal point of a laser processing head when a flat center horn-shaped lens is used as the beam shaping optical system in the laser processing apparatus according to Embodiment 1 [Figure 8] First figure showing an example of the beam shaping optical system in the laser processing apparatus according to Embodiment 2 [Figure 9] Second figure showing an example of the beam shaping optical system in the laser processing apparatus according to Embodiment 2 [Figure 10] Third figure showing an example of the beam shaping optical system in the laser processing apparatus according to Embodiment 2 [Figure 11] Fourth figure showing an example of the beam shaping optical system in the laser processing apparatus according to Embodiment 2 [Figure 12] Fifth figure showing an example of the beam shaping optical system in the laser processing apparatus according to Embodiment 2 [Figure 13] First figure for explaining the focal position in Embodiment 2 [Figure 14] Second figure for explaining the focal position in Embodiment 2 [Figure 15]Figure 1 shows a two-dimensional intensity map of the laser beam at the focal point of the laser processing head, assuming that the peripheral region of the flat-center horn-shaped lens in the laser processing apparatus according to Embodiment 2 has a shape represented by the sag amount expressed by equation (1). [Figure 16] Figure 2 shows a two-dimensional intensity map of the laser beam at the focal point of the laser processing head, assuming that the peripheral region of the flat-center horn-shaped lens in the laser processing apparatus according to Embodiment 2 has a shape represented by the sag amount expressed by equation (1). [Figure 17] Figure 3 shows a two-dimensional intensity map of the laser beam at the focal point of the laser processing head, assuming that the peripheral region of the flat-center horn-shaped lens in the laser processing apparatus according to Embodiment 2 has a shape represented by the sag amount expressed by equation (1). [Figure 18] This figure shows an example of a beam shaping optical system in a laser processing apparatus according to Embodiment 3. [Figure 19] Figure 1 shows an example of a two-dimensional intensity map of the laser beam at the focal point of the laser processing head when using a flat-center horn-shaped lens according to Embodiment 3. [Figure 20] Figure 2 shows an example of a two-dimensional intensity map of the laser beam at the focal point of the laser processing head when using a flat-center horn-shaped lens according to Embodiment 3. [Figure 21] This diagram schematically shows a flat-center horn-shaped lens according to Embodiment 3, in which the differential value of the central region at the boundary is equal to the differential value of the peripheral region. [Figure 22] A schematic diagram showing a flat-center horn-shaped lens according to Embodiment 3. [Modes for carrying out the invention]

[0011] The following describes in detail, with reference to the drawings, a method for manufacturing a product including a laser processing head, a laser processing apparatus, and a metal joint according to an embodiment. The following embodiments are illustrative of the present disclosure and do not limit the present disclosure. In this disclosure, the shape of lenses, etc., may be modified from what is described in the specification or drawings to the extent that the effects of the present disclosure can be achieved. For example, shapes or structures that occur when processing tolerances or errors that are obvious to those skilled in the art, such as rounding or tapering to achieve a desired shape, are not excluded from the scope of this disclosure.

[0012] Embodiment 1. Figure 1 is a schematic diagram showing the configuration of a laser processing apparatus 1 according to Embodiment 1. The laser processing apparatus 1 has a laser oscillator 11, a transmission fiber 12, and a laser processing head 17, and is used for laser processing of a workpiece 18. Examples of laser processing include cutting, welding, additive manufacturing, or heat treatment.

[0013] The laser oscillator 11 may be a device that emits laser light having a wavelength in the near-infrared region, such as a fiber laser, YAG laser, or direct diode laser, or it may be a device that emits laser light having a wavelength in the visible region. The YAG laser may be a disk laser using a disk-shaped medium. The laser oscillator 11 may be a green laser that emits a second harmonic, such as a YAG laser or disk laser. The laser output of the laser oscillator 11 is typically 1 kW or more, preferably 4 kW or more, and more preferably 10 kW or more.

[0014] The transmission fiber 12 transmits the laser light 13 output from the laser oscillator 11. The transmission fiber 12 is, for example, an optical fiber that transmits kilowatt-class laser light 13. At the output end of the transmission fiber 12, the beam shape of the laser light 13 is, for example, a top-hat beam 10. Figure 1 shows the word "Intensity" indicating the intensity of the top-hat beam 10. The core diameter φ0 of the transmission fiber 12 is, for example, 50 μm, 100 μm, 150 μm, 200 μm, or 300 μm. In Figure 1, the laser light 13 is emitted from the transmission fiber 12 in the direction of the z axis, and the optical axis of the laser light 13 is the z axis. Figure 1 also shows the r direction, which is perpendicular to the z axis.

[0015] The laser processing head 17 includes a beam shaping optical system 14, a collimating optical system 15, a focusing optical system 16, and a movable mechanism 19.

[0016] The beam shaping optical system 14 is an optical system into which the laser beam 13 is incident, and it shapes the laser beam 13, which is a top-hat beam 10, at the exit end of the transmission fiber 12. The laser beam 13 is shaped by the beam shaping optical system 14 and irradiated onto the surface of the workpiece 18. The beam shaping optical system 14 is positioned in the optical path of the divergent laser beam 13 between the transmission fiber 12 and the collimating optical system 15. The beam shaping optical system 14 may also be positioned in the optical path of the focused laser beam 13 between the focusing optical system 16 and the workpiece 18.

[0017] The collimating optical system 15 is an optical system into which the laser light 13 that has passed through the beam shaping optical system 14 is incident, and it collimates the laser light 13 that has been emitted from the transmission fiber 12 and diverged. In other words, the collimating optical system 15 parallelizes the laser light 13 that has been emitted from the transmission fiber 12 and diverged. The collimating optical system 15 uses, for example, a plano-convex lens, a biconvex lens, or a convex meniscus lens with a focal length f c It is a convex lens having [a certain characteristic]. The collimating optical system 15 may be a combination lens of a convex lens and a concave lens, or it may be an aspherical lens, for the purpose of reducing spherical aberration.

[0018] The focusing optical system 16 is an optical system into which the laser light 13 that has passed through the collimating optical system 15 is incident, and it focuses the laser light 13 that has been collimated after passing through the collimating optical system 15. Similar to the collimating optical system 15, the focusing optical system 16 has, for example, a focal length f f These include plano-convex lenses, biconvex lenses, convex meniscus lenses, lens arrays, or aspherical lenses. The laser light 13 that has passed through the focusing optical system 16 is irradiated onto the workpiece 18, and laser processing is performed on the workpiece 18. As described above, examples of laser processing include cutting, welding, additive manufacturing, or heat treatment.

[0019] The workpiece 18 is made of a metal material such as mild steel, copper, aluminum, stainless steel, or galvanized steel. The laser processing apparatus 1 can be applied to laser welding of the workpiece 18, for example, and can perform fillet welding or overlap welding by butting the workpiece 18 against a weld joint. When the laser beam 13 is irradiated onto the workpiece 18, the metal constituting the workpiece 18 may melt and a molten pool may be formed. The workpiece 18 may be a metal part such as a metal plate. If a first part and a second part are prepared as the workpiece 18, the laser processing apparatus 1 can irradiate the first part and the second part with laser beam 13 and weld them together to manufacture a third part.

[0020] Figure 1 shows an example where the beam shaping optical system 14 is positioned around the z-axis, which is the optical axis of the laser beam 13, and the central axis of the beam shaping optical system 14 coincides with the z-axis. Hereafter, examples where the central axis of the beam shaping optical system 14 coincides with the z-axis (optical axis) will be shown, but the central axis of the beam shaping optical system 14 and the z-axis may be offset and not coincide. By shaping the beam of the laser beam 13 from the shape of the top-hat beam 10, the laser processing apparatus 1 can, for example, suppress the scattering of spatter from the workpiece 18 when performing laser welding, thereby achieving stable laser welding.

[0021] The movable mechanism 19 is a mechanism that allows the position of the beam shaping optical system 14 in the direction of the z-axis, which is the optical axis of the laser beam 13. The movable mechanism 19 can position the beam shaping optical system 14 at an appropriate position on the z-axis. That is, the movable mechanism 19 has the function of moving the beam shaping optical system 14 in a direction parallel to the optical axis of the laser beam 13. Figure 1 shows the strings (N) and (F). The string (N) indicates that the beam shaping optical system 14 is relatively close to the transmission fiber 12. The string (F) indicates that the beam shaping optical system 14 is relatively far from the transmission fiber 12 and relatively close to the collimating optical system 15. The movable mechanism 19 is, for example, a movable stage that moves in a direction parallel to the z-axis. To control the movement of the movable stage with high precision, for example, a servo motor or a stepping motor may be mounted on the laser processing head 17.

[0022] The movable mechanism 19 may have a rotating helicoid structure, a linear helicoid structure, or a cam structure, etc., that can move the beam shaping optical system 14 in a direction parallel to the z-axis. Figure 1 shows an example of positioning the beam shaping optical system 14 at an appropriate position on the z-axis using the movable mechanism 19. However, the beam shaping optical system 14 may be positioned at an appropriate position on the z-axis without using the movable mechanism 19. In this case, the movable mechanism 19 can be omitted, and the laser processing head 17 can be miniaturized.

[0023] Figure 2 is a schematic diagram showing a flat-centered cone lens 121, which is a first example of the beam shaping optical system 14 in the laser processing apparatus 1 according to Embodiment 1. The flat-centered cone lens 121 is a lens in which the shape of the central region of a cone lens is flat. A cone lens is also called an axicon lens. The flat-centered cone lens 121 is an optical element formed using multiple materials such as SiO2, ZnSe, or Ge, and each material has its own unique refractive index. In Figure 2, the r direction indicates the radial direction, which is the direction of distance from the central axis of the lens. As described above, the r direction is perpendicular to the z axis. The flat-centered cone lens 121 is flat in the central region where r = 0 ≤ r ≤ r0, and conical in the peripheral region where r = r > r0. r0 is a boundary value that specifies the boundary between the central region and the peripheral region. At the boundary value r0, the curvature C of the central region and the curvature C of the peripheral region are discontinuous. In other words, at the boundary value r0, the focal position z of the central region f And the focal position z in the peripheral region f The two points become discontinuous.

[0024] Figure 2 shows a flat-centered cone lens 121 in which the central region is flat and the peripheral region is conical at the incident surface into which the laser beam 13 is incident. However, instead of the flat-centered cone lens 121, a flat-centered cone lens in which the central region is flat and the peripheral region is conical at the exit surface from which the laser beam 13 is emitted may be used. Hereafter, for the sake of simplicity, an example in which the incident surface has both a central region and a peripheral region will be described, but the central region and peripheral region may also be present at the exit surface. The central region and peripheral region may also be present at both the exit surface and the incident surface. The flat-centered cone lens achieves beam shaping of the laser beam 13 on the surface of the workpiece 18 by the action of one or both of the shapes of the incident surface and the exit surface on the laser beam 13.

[0025] Figure 3 is the first figure showing an example of a two-dimensional intensity map of the laser beam 13 at the focal point of the laser processing head 17 when a flat central cone lens 121 is used as the beam shaping optical system 14 in the laser processing apparatus 1 according to Embodiment 1. Figure 4 is the second figure showing an example of a two-dimensional intensity map of the laser beam 13 at the focal point of the laser processing head 17 when a flat central cone lens 121 is used as the beam shaping optical system 14 in the laser processing apparatus 1 according to Embodiment 1. The focal point is the beam profile.

[0026] Figure 3 shows the string (N). The string (N) indicates that the flat-centered cone lens 121 is relatively close to the transmission fiber 12. Figure 4 shows the string (F). The string (F) indicates that the flat-centered cone lens 121 is relatively far from the transmission fiber 12 and relatively close to the collimating optical system 15. In other words, Figure 3 shows an example of a two-dimensional intensity map when the flat-centered cone lens 121 is positioned relatively close to the transmission fiber 12. Figure 4 shows an example of a two-dimensional intensity map when the flat-centered cone lens 121 is positioned relatively close to the collimating optical system 15.

[0027] In both Figure 3 and Figure 4, the beam shape is formed from the shape of the top-hat beam 10, and the beam shape has a central beam 130 with relatively high light intensity at the center, and peripheral beams 131 with lower light intensity than the central beam 130 surrounding the central beam 130. When laser welding is performed, the peripheral beams 131 enable keyhole stabilization and spatter scattering suppression, contributing to stable laser welding.

[0028] The main difference between Figure 3 and Figure 4 is the size of the beam gap 132 formed between the central beam 130 and the peripheral beam 131. In Figure 4, the beam gap 132 is wider than in Figure 3. When the beam gap 132 is larger, the unheated area in the workpiece 18 that is not irradiated by the beam becomes larger. In the unheated area, a molten pool may not form, or it may be difficult to form one, which may result in problems such as instability in the penetration depth into the workpiece 18, or molten metal scattering and adhering to the workpiece 18. Thus, when the beam gap 132 changes, the unheated area in the workpiece 18 changes, which can make laser processing unstable and lead to processing defects.

[0029] Figure 5 schematically shows a flat-centered horn-shaped lens 151, which is a second example of the beam shaping optical system 14 in the laser processing apparatus 1 according to Embodiment 1. The flat-centered horn-shaped lens 151 is a lens in which the shape of the central region where r = 0 ≤ r ≤ r0 is flat, and the peripheral region where r = r > r0 is curved in a horn shape. The horn is a trumpet shape. Figure 5 shows the flat-centered horn-shaped lens 151 curved in the positive direction of the z axis, but the flat-centered horn-shaped lens 151 may also be curved in the negative direction of the z axis.

[0030] Figure 6 is the first figure showing an example of a two-dimensional intensity map of the laser beam 13 at the focal point of the laser processing head 17 when a flat-center horn-shaped lens 151 is used as the beam shaping optical system 14 in the laser processing apparatus 1 according to Embodiment 1. Figure 7 is the second figure showing an example of a two-dimensional intensity map of the laser beam 13 at the focal point of the laser processing head 17 when a flat-center horn-shaped lens 151 is used as the beam shaping optical system 14 in the laser processing apparatus 1 according to Embodiment 1.

[0031] Figure 6 shows the string (N). The string (N) indicates that the flat-center horn-shaped lens 151 is relatively close to the transmission fiber 12. Figure 7 shows the string (F). The string (F) indicates that the flat-center horn-shaped lens 151 is relatively far from the transmission fiber 12 and relatively close to the collimating optical system 15. In other words, Figure 6 shows an example of a two-dimensional intensity map when the flat-center horn-shaped lens 151 is positioned relatively close to the transmission fiber 12. Figure 7 shows an example of a two-dimensional intensity map when the flat-center horn-shaped lens 151 is positioned relatively close to the collimating optical system 15.

[0032] Similar to Figures 3 and 4, in both Figure 6 and Figure 7, the beam shape is formed from the shape of the top-hat beam 10. The beam shape has a central beam 130 with relatively high light intensity at its center, and peripheral beams 131 with lower light intensity than the central beam 130 surrounding it. Unlike Figures 3 and 4, the change in the beam gap 132 is small in Figures 6 and 7. Thus, by using a flat central horn-shaped lens 151 as the beam shaping optical system 14, the change in the beam gap 132 is small even when the position of the beam shaping optical system 14 changes, and the change in the unheated area of ​​the workpiece 18 can be reduced, thus enabling stable laser processing.

[0033] Embodiment 2. The configuration of the laser processing apparatus according to Embodiment 2 differs from the configuration of the laser processing apparatus 1 according to Embodiment 1 only in the specific example of the beam shaping optical system 14. In Embodiment 2, the differences from Embodiment 1 will be mainly described. FIG. 8 is a first diagram showing an example of the beam shaping optical system 14 in the laser processing apparatus according to Embodiment 2. In FIG. 8, the example of the beam shaping optical system 14 is a flat center convex lens 211. FIG. 9 is a second diagram showing an example of the beam shaping optical system 14 in the laser processing apparatus according to Embodiment 2. In FIG. 9, the example of the beam shaping optical system 14 is a flat center concave lens 212. FIG. 10 is a third diagram showing an example of the beam shaping optical system 14 in the laser processing apparatus according to Embodiment 2. In FIG. 10, the example of the beam shaping optical system 14 is a flat center conical lens 121. FIG. 11 is a fourth diagram showing an example of the beam shaping optical system 14 in the laser processing apparatus according to Embodiment 2. In FIG. 11, the example of the beam shaping optical system 14 is a flat center horn-shaped lens 213. FIG. 12 is a fifth diagram showing an example of the beam shaping optical system 14 in the laser processing apparatus according to Embodiment 2. In FIG. 12, the example of the beam shaping optical system 14 is a flat center horn-shaped lens 214.

[0034] In each of FIGS. 8 to 12, the shape of the beam shaping optical system 14 is shown in the upper part, the curvature C of the incident surface is shown in the middle part, and the focal position z of the beam shaping optical system 14 f is shown in the lower part. The focal position z f is defined as the position where the traveling direction of the light beam is bent by the beam shaping optical system 14 when a light beam parallel to the central axis traveling in the positive direction from the negative direction of the z-axis direction is incident on the beam shaping optical system 14 arranged at z = 0, and the light beam intersects the central axis. The central axis is the z-axis. Hereinafter, a light beam parallel to the central axis will be referred to as a parallel light beam 271.

[0035] FIG. 13 is a first diagram for explaining the focal position z in Embodiment 2 f FIG. 14 is a second diagram for explaining the focal position z in Embodiment 2 f Using FIGS. 13 and 14, the focal position z fLet's explain a simple example. As shown in Figure 13, when a thin lens 272 with a focal length f, which corresponds to a convex lens, is placed at z=0, parallel light rays 271 traveling from negative to positive in the z-axis direction intersect the central axis at the focal length f position. Therefore, the focal position z f is z f =f. As shown in Figure 14, when a thin lens 273 with a focal length of -f, which corresponds to a concave lens, is placed at the position z=0, the focal position z f is z f = -f.

[0036] When a thin lens, which is an ideal lens without aberrations, is used, as shown in the lower part of Figures 13 and 14, even if the ray height h274, which is the distance between the central axis (z-axis) and the parallel ray 271, changes, the focal position z f It remains constant and does not change. In an actual lens, the focal position z f Since it changes with the ray height h274, the focal position z also changes in the beam shaping optical system 14. f This value changes depending on the ray height h274. The details are explained below.

[0037] Figure 8 shows a flat-centered convex lens 211 as a beam shaping optical system 14. The flat-centered convex lens 211 is a lens in which the central region of a convex lens is flat. The curvature C of the flat-centered convex lens 211 is 0 in the central region where r is 0 ≤ r ≤ r0, and is a constant positive value in the peripheral region where r is r > r0. In the central region of the flat-centered convex lens 211, the focal position z f It does not exist. In the peripheral region, the flat central convex lens 211 has a positive focal position z f The focal position z increases as the distance between the parallel rays 271 and the central axis increases. f It decreases monotonically. The distance between the parallel ray 271 and the central axis is the ray height h.

[0038] Figure 9 shows a flat central concave lens 212 as a beam shaping optical system 14. The flat central concave lens 212 is a lens in which the central region of a concave lens is flat. The curvature C of the flat central concave lens 212 is 0 in the central region where r ≤ r ≤ r0, and is a constant negative value in the peripheral region where r > r0. In the central region of the flat central concave lens 212, the focal position z f It does not exist. In the peripheral region, the flat central concave lens 212 has a negative focal position z f The focal position z increases as the ray height h, which is the distance between the parallel rays 271 and the central axis, increases. f It increases monotonically.

[0039] Figure 10 shows a flat-centered cone lens 121 as a beam shaping optical system 14. In both the central region where r = 0 ≤ r ≤ r0 and the peripheral region where r = r > r0, the curvature C of the flat-centered cone lens 121 is 0. In the central region of the flat-centered cone lens 121, the focal position z f It does not exist. In the peripheral region, the flat central cone lens 121 has a positive focal position z f The focal position z increases as the ray height h, which is the distance between the parallel rays 271 and the central axis, increases. f It increases linearly. Linear means in a straight line.

[0040] Figure 11 shows a flat-center horn lens 213 as a beam shaping optical system 14. The flat-center horn lens 213 is a modified version of the flat-center horn lens 151. In the flat-center horn lens 213, the curvature increases monotonically in the peripheral region where r > r0. In the central region where r ≤ r ≤ r0, the curvature C of the flat-center horn lens 213 is 0. In the peripheral region, the curvature C of the flat-center horn lens 213 is negative. In the central region of the flat-center horn lens 213, the focal position z f It does not exist. In the peripheral region, the flat-center horn-shaped lens 213 has a positive focal position z f The focal position z increases as the ray height h, which is the distance between the parallel rays 271 and the central axis, increases. fIt increases monotonically and nonlinearly. Nonlinear means curvilinear.

[0041] Figure 12 shows a flat-center horn lens 214 as a beam shaping optical system 14. The flat-center horn lens 214 is a modified version of the flat-center horn lens 151. In the flat-center horn lens 214, the curvature in the peripheral region where r > r0 decreases monotonically. In the central region where r ≤ r ≤ r0, the curvature C of the flat-center horn lens 214 is 0. In the peripheral region, the curvature C of the flat-center horn lens 214 is positive. In the central region of the flat-center horn lens 214, the focal position z f It does not exist. In the peripheral region, the flat-center horn-shaped lens 214 has a negative focal position z f The focal position z increases as the ray height h, which is the distance between the parallel rays 271 and the central axis, increases. f It decreases monotonically and non-linearly.

[0042] To summarize the above, for the flat-center horn-shaped lens 213 shown in Figure 11 and the flat-center horn-shaped lens 214 shown in Figure 12, the central region where r is 0 ≤ r ≤ r0 has a focal position z f It does not exist. In the peripheral region where r > r0, the flat-centered horn lenses 213 and 214 and the focal position z f z is the distance between f The absolute value of |z| f However, it increases monotonically and nonlinearly as the ray height h, which is the distance from the central axis, increases. Flat-center horn lenses 213 and 214 refer to flat-center horn lens 213 and flat-center horn lens 214, respectively.

[0043] Figures 8 through 12 show the central region of the beam shaping optical system 14 at the focal position z f This example shows that such a phenomenon does not occur, and in the central region, the curvature C=0, and the beam shaping optical system 14 has no refractive power. In other words, the beam shaping optical system 14 has no refractive power on the central axis.

[0044] By using the flat-center horn-shaped lenses 213 and 214, the change in the beam gap 132 can be minimized even when the position of the flat-center horn-shaped lenses 213 and 214 changes, similar to the examples shown in Figures 6 and 7. As a result, the change in the unheated portion of the workpiece 18 is reduced, enabling stable laser processing.

[0045] The peripheral regions of the flat-center horn-shaped lenses 213 and 214 may have a shape represented by a sag amount z(r) expressed by the following equation (1), which includes constants K0 and z0. z(r) = K0 log r + z0 ... (1)

[0046] In equation (1), log represents the natural logarithm, and Napier's number e, which is the base of the natural logarithm, is omitted. Figure 15 is the first figure showing a two-dimensional intensity map of the laser beam 13 at the focal point of the laser processing head 17, assuming that the peripheral regions of the flat central horn-shaped lenses 213,214 in the laser processing apparatus according to Embodiment 2 have a shape represented by the sag amount expressed in equation (1). Figure 16 is the second figure showing a two-dimensional intensity map of the laser beam 13 at the focal point of the laser processing head 17, assuming that the peripheral regions of the flat central horn-shaped lenses 213,214 in the laser processing apparatus according to Embodiment 2 have a shape represented by the sag amount expressed in equation (1). Figure 17 is the third figure showing a two-dimensional intensity map of the laser beam 13 at the focal point of the laser processing head 17, assuming that the peripheral regions of the flat central horn-shaped lenses 213,214 in the laser processing apparatus according to Embodiment 2 have a shape represented by the sag amount expressed in equation (1). The point of convergence is the focal point, and the 2D intensity map is the beam profile.

[0047] Figures 15 to 17 show examples of beam profiles when the z-axis position of the flat-center horn lenses 213 and 214 is changed sequentially, starting from the position closest to the transmission fiber 12. Figure 15 shows an example of the beam profile when the flat-center horn lenses 213 and 214 are positioned closest to the transmission fiber 12. Figure 16 shows an example of the beam profile when the flat-center horn lenses 213 and 214 are positioned next closest to the transmission fiber 12. Figure 17 shows an example of the beam profile when the flat-center horn lenses 213 and 214 are positioned furthest from the transmission fiber 12. In other words, Figure 17 shows an example of the beam profile when the flat-center horn lenses 213 and 214 are positioned closest to the collimating optical system 15.

[0048] As can be seen from Figures 15 to 17, the flat-center horn lenses 213 and 214 have the characteristic of not changing the beam gap 132 even when their position changes. When the position of the flat-center horn lenses 213 and 214 changes, the peripheral beam width 221, which is the width of the peripheral beam 131, can be changed, and the peripheral beam width 221 is increased as it approaches the collimating optical system 15. For example, if the peripheral beam width 221 is set to the peripheral beam width corresponding to the workpiece 18, stable laser processing can be achieved even if the workpiece 18 changes.

[0049] The shape of the peripheral region of the flat-center horn-shaped lenses 213 and 214 may be optimized so that the width and intensity of the peripheral beam 131 are optimal in accordance with processing conditions such as the workpiece 18, processing speed, and laser output of the laser oscillator 11. For example, if the shape of the peripheral region of the flat-center horn-shaped lenses 213 and 214 is represented by the sag amount z(r) of equation (1), the shape of the peripheral region may be optimized by setting the constants K0 and z0 to optimal values.

[0050] As described above, the beam shaping optical system 14 of the laser processing head 17 according to Embodiment 2 has an optical property in which, in the peripheral region where the distance from the central axis in a plane perpendicular to the central axis of the beam shaping optical system 14 exceeds a predetermined boundary value, when a ray parallel to the central axis, which is the optical axis of the laser beam 13, is incident at a position where the distance is the ray height h, the distance between the intersection point of the ray and the central axis and the beam shaping optical system 14 increases monotonically and nonlinearly as the ray height h increases. Since the beam shaping optical system 14 has this optical property, the laser processing head 17 according to Embodiment 2 can contribute to achieving stable laser processing.

[0051] The curvature C in the peripheral region of the incident or exit surface of the laser beam 13 of the beam shaping optical system 14 may increase monotonically or decrease monotonically as the distance from the central axis in a plane perpendicular to the central axis of the beam shaping optical system 14 increases.

[0052] For example, the beam shaping optical system 14 is made of a material with a refractive index different from that of the surrounding atmosphere in which the beam shaping optical system 14 is installed. The effect on the laser light 13 caused by the shape of the incident surface of the beam shaping optical system 14, the effect on the laser light 13 caused by the shape of the exit surface of the beam shaping optical system 14, and the effect on the laser light 13 caused by the shapes of the incident surface and the exit surface may differ between the central region and the peripheral region of the beam shaping optical system 14. As a result of the difference in the effect on the laser light 13 caused by the central region of the beam shaping optical system 14 and the effect on the laser light 13 caused by the peripheral region, the beam shaping optical system 14 can shape the laser light 13, and the laser processing head 17 according to Embodiment 2 can contribute to achieving stable laser processing.

[0053] Embodiment 3. The configuration of the laser processing apparatus according to Embodiment 3 differs from the configuration of the laser processing apparatus 1 according to Embodiment 1 only in the specific example of the beam shaping optical system 14. Embodiment 3 mainly describes the differences from Embodiments 1 and 2. Figure 18 is a diagram showing an example of the beam shaping optical system 14 in the laser processing apparatus according to Embodiment 3. Figure 18 shows a flat-center horn-shaped lens 311 as the beam shaping optical system 14. The flat-center horn-shaped lens 311 is a modified example of the flat-center horn-shaped lens 151. In the flat-center horn-shaped lens 311, the central region where r is 0 ≤ r ≤ r0 and the peripheral region where r is r > r0 are smoothly connected by a curved surface. By using the flat-center horn-shaped lens 311, laser processing becomes easier, and unexpected refraction or diffraction caused by a decrease in processing accuracy can be suppressed.

[0054] Figure 19 is the first figure showing an example of a two-dimensional intensity map of the laser beam 13 at the focal point of the laser processing head 17 when using the flat-center horn-shaped lens 311 according to Embodiment 3. Figure 20 is the second figure showing an example of a two-dimensional intensity map of the laser beam 13 at the focal point of the laser processing head 17 when using the flat-center horn-shaped lens 311 according to Embodiment 3. The focal point is the focal point, and the two-dimensional intensity map is the beam profile.

[0055] Figure 19 shows the string (N). The string (N) indicates that the flat-center horn-shaped lens 311 is relatively close to the transmission fiber 12. Figure 20 shows the string (F). The string (F) indicates that the flat-center horn-shaped lens 311 is relatively far from the transmission fiber 12 and relatively close to the collimating optical system 15. In other words, Figure 19 shows an example of a two-dimensional intensity map when the flat-center horn-shaped lens 311 is positioned relatively close to the transmission fiber 12. Figure 20 shows an example of a two-dimensional intensity map when the flat-center horn-shaped lens 311 is positioned relatively close to the collimating optical system 15.

[0056] In Embodiment 3, as shown in Figures 19 and 20, the beam shape is formed from the shape of the top-hat beam 10, resulting in a beam shape that has a central beam 130 with relatively high light intensity at its center, and peripheral beams 131 with lower light intensity than the central beam 130 surrounding the central beam 130. Unlike Figures 3, 4, 6, and 7, the two-dimensional intensity map shown in Figures 19 and 20 has an intermediate beam 321 that fills the space between the central beam 130 and the peripheral beams 131. By using a flat central horn-shaped lens 311 as the beam shaping optical system 14, the intermediate beam 321 reduces the unheated area, which is the non-irradiated part of the beam in the workpiece 18, thereby enabling stable laser processing.

[0057] As described above, in the flat-center horn-shaped lens 311, the central region and the peripheral region are smoothly connected by a curved surface. The first method for smoothly connecting the central region and the peripheral region by a curved surface is to apply an R-chamfer of a desired radius R at the boundary r=r0 between the central region and the peripheral region. The second method for smoothly connecting the central region and the peripheral region by a curved surface is to make the two values ​​dz / dr, obtained by differentiating the equation representing the sag amount of the central region and the equation representing the sag amount of the peripheral region, equal at the boundary r=r0 between the central region and the peripheral region. In other words, the second method is to make the tangent line continuous at the boundary r=r0. The method for smoothly connecting the central region and the peripheral region by a curved surface is not limited to the methods described above.

[0058] Figure 21 schematically shows a flat-center horn-shaped lens 331 according to Embodiment 3, in which the differential value of the central region and the differential value of the peripheral region are equal at the boundary r=r0. The flat-center horn-shaped lens 331 is an example of the flat-center horn-shaped lens 311. For the flat-center horn-shaped lens 331, in the central region, the differential value dz / dr increases as r increases, and at the boundary r=r0, the differential value dz / dr of the central region and the differential value dz / dr of the peripheral region coincide, while in the peripheral region, the differential value dz / dr decreases as r increases. In this way, by making the differential value dz / dr of the central region and the differential value dz / dr of the peripheral region coincide at the boundary r=r0, the central region and the peripheral region may be smoothly connected.

[0059] Figure 22 is a schematic diagram showing a flat-centered horn-shaped lens 332 according to Embodiment 3. The flat-centered horn-shaped lens 332 is a modified example of the flat-centered horn-shaped lens 151, obtained by curving the peripheral region of the flat-centered horn-shaped lens 151 in the negative direction of the z-axis. In the flat-centered horn-shaped lens 332, the central region and the peripheral region are smoothly connected by a curved surface. By using the flat-centered horn-shaped lens 332, laser processing becomes easier, and unexpected refraction or diffraction caused by a decrease in processing accuracy can be suppressed.

[0060] In the flat-center horn-shaped lens 332 shown in Figure 22, a chamfer of a desired radius R may be applied at the boundary r=r0 between the central region and the peripheral region, or the derivatives dz / dr of the equation representing the sag amount of the central region and the equation representing the sag amount of the peripheral region may be made equal at the boundary r=r0.

[0061] As described above, in the beam shaping optical system 14 according to Embodiment 3, the boundary between the central region and the peripheral region of the incident or exit surface of the laser beam 13 is smoothly connected by a curved surface.

[0062] By irradiating a workpiece 18 composed of a first part and a second part with laser light 13 emitted from a laser processing head 17 of any of Embodiments 1 to 3, the first part and the second part can be welded together to manufacture a product including a metal joint. In other words, by irradiating a workpiece 18 composed of a workpiece 18 composed of a first part and a second part with laser light 13 emitted from a laser processing head 17 of any of Embodiments 1 to 3, the first part and the second part can be welded together to manufacture a product including a metal joint.

[0063] The configurations shown in the above embodiments are examples only, and it is possible to combine them with other known technologies, combine different embodiments, and omit or modify parts of the configuration without departing from the gist of the invention. [Explanation of Symbols]

[0064] 1 Laser processing device, 10 Top hat beam, 11 Laser oscillator, 12 Transmission fiber, 13 Laser light, 14 Beam shaping optics, 15 Collimating optics, 16 Focusing optics, 17 Laser processing head, 18 Workpiece, 19 Movable mechanism, 121 Flat central cone lens, 130 Central beam, 131 Peripheral beam, 132 Beam gap, 151, 213, 214, 311, 331, 332 Flat central horn lens, 211 Flat central convex lens, 212 Flat central concave lens, 221 Peripheral beam width, 271 Parallel rays, 272, 273 Thin-walled lenses, 274 Ray height, 321 Mid-beam.

Claims

1. A beam shaping optical system into which laser light is incident, A collimating optical system into which the laser light that has passed through the beam shaping optical system is incident, The system comprises a focusing optical system into which the laser light that has passed through the collimating optical system is incident, The beam shaping optical system has an optical property in which, when a ray parallel to the central axis, which is the optical axis of the laser beam, is incident on a peripheral region where the distance from the central axis in a plane perpendicular to the central axis of the beam shaping optical system exceeds a predetermined boundary value, the distance between the intersection point of the ray and the central axis and the beam shaping optical system increases monotonically and nonlinearly as the ray height increases. A laser processing head characterized by the following features.

2. The beam shaping optical system does not have refractive power on the central axis. The laser processing head according to feature 1.

3. The beam shaping optical system is formed of a material with a refractive index different from that of the surrounding atmosphere in which the beam shaping optical system is installed. The effect on the laser light caused by the shape of the incident surface of the beam shaping optical system, the effect on the laser light caused by the shape of the exit surface of the beam shaping optical system, and any of the effects on the laser light caused by the shape of the incident surface and the shape of the exit surface differ between the central region, which is the region in which the distance from the central axis in the plane perpendicular to the central axis of the beam shaping optical system is less than or equal to the boundary value, and the peripheral region. A laser processing head according to claim 1 or 2, characterized by the above.

4. The curvature of the incident surface or the exit surface of the beam shaping optical system in the peripheral region increases monotonically as the distance from the central axis in the plane perpendicular to the central axis of the beam shaping optical system increases, or decreases monotonically. The laser processing head according to feature 3.

5. The shape of the central region is flat. The laser processing head according to feature 3.

6. The boundary between the central region and the peripheral region of the incident surface or the exit surface of the beam shaping optical system is smoothly connected by a curved surface. The laser processing head according to feature 3.

7. The system further comprises a movable mechanism for moving the beam shaping optical system in a direction parallel to the optical axis of the laser beam. A laser processing head according to claim 1 or 2, characterized by the above.

8. A laser oscillator that emits the aforementioned laser light, The laser processing head according to claim 1 or 2 and A laser processing apparatus characterized by being equipped with the following features.

9. A step of welding and joining a first part and a second part by irradiating them with the laser light emitted from the laser processing head described in claim 1 or 2. A method for manufacturing a product including a metal joint, characterized by including the following.

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