Ring beam shaping element and laser processing machine

Abstract

A ring beam shaping element (31s) comprises a first surface that is one of an incidence surface and an emission surface of a laser beam and is a flat surface, and a second surface that is the other of the incidence surface and the emission surface. On the second surface, an uneven pattern is formed, including a plurality of radial protrusions (311) and recesses (312) formed at a plurality of regular angular positions in the circumferential direction, the protrusions (311) and recesses (312) extending radially outward from the center (310) of the second surface. The distance between the first surface and the surface of the protrusions (311) formed on the second surface is 2 mm or less. The protrusions (311) have a uniform height from the center (310) to the outermost position in the radial direction, and the recesses (312) have a uniform depth from the center (310) to the outermost position in the radial direction. The number of the protrusions (311) or the recesses (312) is 6-31 inclusive.

Description

Ring beam shaping element and laser processing machine

[0001] The present disclosure relates to a ring beam shaping element and a laser processing machine.

[0002] Patent Document 1 describes a ring beam shaping element in which a plurality of inclined surfaces are arranged in the circumferential direction on one surface of a plate-like optical element, the inclination direction of which changes alternately with respect to the other surface, which is a flat plate surface.

[0003] International Publication No. 2016 / 120327

[0004] The ring beam shaping element described in Patent Document 1 has a complex shape and is therefore difficult to fabricate. There is a need for a ring beam shaping element that has a simple shape, is easy to fabricate, and is capable of shaping a laser beam into a ring shape, as well as a laser processing machine equipped with such a ring beam shaping element that can process workpieces with high quality.

[0005] A first aspect of one or more embodiments provides a ring beam shaping element comprising: a first surface which is one of an incident surface and an exit surface of a laser beam and is a flat surface; and a second surface which is the other of the incident surface and the exit surface, wherein an unevenness pattern is formed on the second surface, the unevenness pattern being made up of a plurality of convex portions and concave portions which radiate from the center of the second surface toward the radially outward direction at a plurality of angular positions which are evenly spaced circumferentially; the distance between the first surface and the surface of the convex portions formed on the second surface is within 2 mm; the convex portions have a uniform height from the center to the outermost position in the radial direction; and the concave portions have a uniform depth from the center to the outermost position in the radial direction; and the number of the convex portions or the concave portions in the unevenness pattern is between 6 and 31.

[0006] A second aspect of one or more embodiments provides a laser processing machine comprising: a laser oscillator that emits a laser beam; an optical fiber that transmits the laser beam emitted from the laser oscillator; and a processing head into which a diverging laser beam having a Gaussian beam profile emitted from the emission end of the optical fiber is incident, wherein the processing head has a collimating lens that converts the diverging laser beam into collimated light; a focusing lens that focuses the collimated laser beam emitted from the collimating lens and irradiates a workpiece with the focused laser beam; and a ring beam shaping element that is disposed between the emission end of the optical fiber and the collimating lens and converts the Gaussian beam profile into a ring beam profile.

[0007] In the above laser processing machine, the ring beam shaping element has a first surface which is a flat surface and is one of an incident surface on which the diverging laser beam is incident and an exit surface from which the laser beam converted into the ring-shaped beam profile exits, and a second surface which is the other of the incident surface and the exit surface, and on the second surface, an unevenness pattern is formed which is made up of a plurality of convex portions and concave portions radially extending from the center of the second surface toward the outside in the radial direction at a plurality of angular positions which are evenly spaced circumferentially, the distance between the first surface and the surface of the convex portions formed on the second surface is within 2 mm, the convex portions have a uniform height from the center to the outermost position in the radial direction, and the concave portions have a uniform depth from the center to the outermost position in the radial direction, and the number of the convex portions or concave portions in the unevenness pattern is between 6 and 31.

[0008] The ring beam shaping element according to one or more embodiments is difficult to fabricate, but has a simple shape and is easy to fabricate, and is capable of shaping a laser beam into a ring shape.The laser processing machine according to one or more embodiments is equipped with the ring beam shaping element and can process a workpiece with high quality.

[0009] FIG. 1 is a diagram showing a laser processing machine according to a first embodiment. FIG. 2 is a perspective view showing a ring beam shaping element according to the first embodiment. FIG. 3 is a characteristic diagram showing the relationship between the number of convex or concave portions in the ring beam shaping element according to the first embodiment and the beam parameter product. FIG. 4 is a diagram showing simulation results of beam profiles when the number of convex or concave portions in the ring beam shaping element according to the first embodiment is set to 2 to 12. FIG. 5 is a diagram showing a laser processing machine according to a second embodiment. FIG. 6 is a plan view showing a ring beam shaping element according to the second embodiment. FIG. 7 is a diagram showing a first example of a ring beam obtained with the ring beam shaping element according to the second embodiment. FIG. 8 is a diagram showing a second example of a ring beam obtained with the ring beam shaping element according to the second embodiment. FIG. 9 is a diagram showing a laser processing machine according to a third embodiment. FIG. 10A is a diagram showing a beam profile when the convex portions of two ring beam shaping elements exactly face each other in the laser processing machine according to the third embodiment. FIG. 10B is a diagram showing a beam profile when the convex portions of two ring beam shaping elements face each other with a circumferential offset of half. Fig. 10C is a diagram showing a beam profile when the convex portions and concave portions of two ring beam shaping elements are exactly opposite to each other in the laser processing machine according to the third embodiment. Fig. 11 is a diagram showing a laser processing machine according to the fourth embodiment.

[0010] Hereinafter, the ring beam shaping element and the laser processing machine according to each embodiment will be described with reference to the accompanying drawings.

[0011] <First Embodiment> Fig. 1 shows a laser processing machine 100 according to a first embodiment. The laser processing machine 100 may be a laser cutting machine that cuts a metal sheet W, which is a workpiece to be processed, or may be a laser welder that welds the metal sheet W. In the former case, the metal sheet W is, for example, one piece, and in the latter case, the metal sheet W is, for example, two pieces. The laser processing machine 100 includes an NC device 10, a laser oscillator 20, and a processing head 30. The laser oscillator 20 and the processing head 30 are connected by an optical fiber 25 that transmits a laser beam emitted from the laser oscillator 20.

[0012] The NC device 10 controls the laser oscillator 20. Typically, the laser oscillator 20 is a fiber laser oscillator. However, the laser oscillator 20 is not limited to a fiber laser oscillator. The laser processing machine 100 may be provided with a movement mechanism (not shown) that moves the processing head 30. In this case, the NC device 10 controls the movement mechanism to move the processing head 30.

[0013] The processing head 30 has a ring beam shaping element 31s, a collimator lens 32, and a focusing lens 33 according to the first embodiment. The optical fiber 25 emits a diverging laser beam from its exit end. The diverging laser beam is incident on the ring beam shaping element 31s. The laser beam incident on the ring beam shaping element 31s has a Gaussian beam profile. The beam profile is a characteristic that indicates the intensity distribution of the laser beam. As will be described later, the ring beam shaping element 31s shapes the incident laser beam into a ring shape and converts the beam profile into a ring shape.

[0014] The collimating lens 32 converts the laser beam emitted from the ring beam shaping element 31s into collimated light. The focusing lens 33 focuses the collimated laser beam and irradiates the metal plate W with the focused laser beam.

[0015] 1, the ring beam shaping element 31s is disposed between the exit end of the optical fiber 25 and the collimator lens 32. By disposing the ring beam shaping element 31s between the exit end of the optical fiber 25 and the collimator lens 32, the ring beam shaping element 31s can be made smaller, and therefore, the ring beam shaping element 31s can be made inexpensive.

[0016] The configuration of the ring beam shaping element 31s will be described in detail using Figure 2. The ring beam shaping element 31s can be configured from a circular glass plate, such as a synthetic quartz plate with a predetermined thickness and a diameter of approximately 20 mm, that is highly transparent. In Figure 1, a flat surface that is one of the entrance and exit surfaces of the laser beam in the ring beam shaping element 31s is referred to as a first surface, and the other of the entrance and exit surfaces is referred to as a second surface. In Figure 1, the entrance surface of the laser beam is referred to as the first flat surface, and the exit surface is referred to as the second flat surface; however, the exit surface may be referred to as the first flat surface, and the entrance surface may be referred to as the second flat surface.

[0017] As shown in FIG. 2 , a concave-convex pattern is formed on the second surface of the ring beam shaping element 31s, with a plurality of convex portions 311 and concave portions 312 arranged in the circumferential direction. The convex portions 311 and concave portions 312 are formed at a plurality of angular positions that are evenly spaced around the circumference of the second surface. The convex portions 311 and concave portions 312 are formed radially outward from the center 310. Each convex portion 311 and each concave portion 312 is formed in a range from the center 310 to the outer end in the radial direction at each angular position. When viewed from above, each concave portion 312 and each convex portion 311 has a fan-like planar shape.

[0018] The convex portions 311 have a uniform height from the center 310 to the ends in the radial direction, and the concave portions 312 have a uniform depth from the center 310 to the ends in the radial direction. In Fig. 2, the height of the convex portions 311 and the depth of the concave portions 312 are exaggerated to make it easier to understand the concave-convex pattern.

[0019] The first and second surfaces of the ring beam shaping element 31s may preferably be coated with an anti-reflection coating. Most of the laser beam incident on the ring beam shaping element 31s passes through the ring beam shaping element 31s and enters the collimator lens 32. However, a portion of the laser beam is absorbed by the ring beam shaping element 31s, causing a predetermined temperature distribution in the ring beam shaping element 31s. When a temperature distribution occurs in the ring beam shaping element 31s, a refractive index distribution occurs due to the thermal lens effect, which increases the spot diameter at which the laser beam is focused, potentially reducing processing quality.

[0020] If the thickness of the ring beam shaping element 31s is 2 mm or less, the thermal lens effect is small and the processing quality is hardly deteriorated. Therefore, it is preferable that the thickness of the ring beam shaping element 31s is 2 mm or less. Since the thickness of the ring beam shaping element 31s is 2 mm or less, the distance between the surfaces of the convex portions 311 formed on the first and second surfaces is 2 mm or less.

[0021] The ring beam shaping element 31s can be fabricated by using photolithography technology used in semiconductor processes. The ring beam shaping element 31s having a concave-convex pattern can be fabricated by applying a photoresist to a circular glass plate, exposing and developing a pattern corresponding to the concave-convex pattern to form a pattern in the resist, and then transferring the pattern to the glass plate by dry etching.

[0022] The ring beam shaping element 31s can be produced inexpensively using photolithography technology. Moreover, the concave-convex pattern, which is made up of convex portions 311 and concave portions 312 having uniform heights and depths from the center 310 to the radial ends, is simpler than the concave-convex pattern of the ring beam shaping element described in Patent Document 1, and therefore can be produced easily and inexpensively.

[0023] The relationship between the pitch d of the convex portions 311 and concave portions 312, the diffraction angle θ of the laser beam, and the wavelength λ is expressed by equation (1). The constant m is 1 for first-order diffraction. Increasing the number of convex portions 311 and concave portions 312 reduces the pitch d, which increases the diffraction angle θ and changes the beam diameter of the ring beam. The smaller the pitch d, the larger the beam diameter of the ring beam, and the larger the pitch d, the smaller the beam diameter of the ring beam. d sin θ = mλ ... (1)

[0024] The height of the convex portion 311 and the design depth h of the concave portion 312 can be calculated using the refractive index n of the glass material and the wavelength λ according to the formula (2): h=λ / 2(n−1) (2)

[0025] The beam parameter products (hereinafter, BPP) vary depending on the number of convex portions 311 and concave portions 312. BPP is an index of beam quality. FIG. 3 shows the relationship between the number of convex portions 311 or concave portions 312 (hereinafter, "number of convex portions and concave portions") and BPP. As shown in FIG. 3, increasing the number of convex portions and concave portions increases BPP, resulting in a deterioration of beam quality. Here, an example is shown in which the core diameter of the optical fiber 25 is 100 μm, the focal length of the collimator lens 32 is 140 mm, the focal length of the focusing lens 33 is 190 mm, and the ring beam shaping element 31s is positioned 55 mm from the exit end of the optical fiber 25. If the number of convex portions and concave portions is x and the BPP is y, the relationship between the number of convex portions and BPP shown in FIG. 3 is y = 0.6917x + 3.3667.

[0026] If the metal sheet W is a thick plate with a thickness of 6 mm to 30 mm, in order to cut the metal sheet W with good processing quality, it is preferable to set the BPP to 25 or less. As shown in Figure 3, in order to set the BPP to 25 or less, the number of concave-convex portions should be 31. Therefore, it is preferable to set the upper limit of the number of concave-convex portions in the concave-convex pattern formed on the ring beam shaping element 31s to 31.

[0027] On the other hand, if the metal sheet W is a thin plate with a thickness of less than 6 mm, it is best to make the BPP as small as possible in order to cut the metal sheet W with good processing quality. Figure 4 shows the results of a beam profile simulation when the height of the convex portions 311 and the depth h of the concave portions 312 are 1.2 μm and the number of convex portions is 2 to 12. As can be seen from Figure 4, if the number of convex portions is reduced too much to reduce the BPP, the laser beam will have an irregular shape that deviates from a ring beam. If the laser beam has an irregular shape, the processing quality will deteriorate and the processing quality will vary depending on the processing direction, resulting in processing direction dependency of the processing quality.

[0028] In a beam profile when the number of irregularities is 5, the ring beam and the central beam located in the center of the ring beam are slightly connected, and the ring beam is not completely separated from the central beam. On the other hand, in a beam profile when the number of irregularities is 6, the ring beam is separated from the central beam. Therefore, the lower limit of the number of irregularities in the irregular pattern formed on the ring beam shaping element 31s should be 6. If the number of irregularities is more than 8, the ring beam will have a more preferable circular shape and will be completely separated from the central beam, so the lower limit of the number of irregularities may be 10.

[0029] As described above, the ring beam shaping element 31s includes a first surface, which is one of the laser beam entrance surface and exit surface and is a flat surface, and a second surface, which is the other of the entrance surface and exit surface. The second surface has a concave-convex pattern formed thereon, consisting of a plurality of convex portions 311 and concave portions 312, which radiate radially outward from the center of the second surface at a plurality of evenly spaced angular positions in the circumferential direction. The distance between the surfaces of the convex portions 311 formed on the first surface and the second surface is within 2 mm. The convex portions 311 have a uniform height from the center to the outermost position in the radial direction, and the concave portions 312 have a uniform depth from the center to the outermost position in the radial direction. The number of convex portions 311 or concave portions 312 is 6 or more (preferably 10 or more) and is within 31.

[0030] The ring beam shaping element 31s according to the first embodiment has a simple shape and is easy to fabricate, and can shape the laser beam into a ring shape. The laser processing machine 100 according to the first embodiment is equipped with the ring beam shaping element 31s according to the first embodiment, and can shape the Gaussian beam into a desirable circular ring beam separated from the central beam, thereby enabling high-quality processing of the metal sheet W.

[0031] Second Embodiment Figure 5 shows a laser processing machine 200 according to a second embodiment. In Figure 5, the same parts as in Figure 1 are given the same reference numerals, and their description will be omitted. The processing head 30 in the laser processing machine 200 is equipped with a ring beam shaping element 31w instead of the ring beam shaping element 31s. Figure 6 is a plan view of the ring beam shaping element 31w. The definitions of the first surface and the second surface of the ring beam shaping element 31w are the same as the definitions of the first surface and the second surface of the ring beam shaping element 31s.

[0032] 6, the ring beam shaping element 31w has an outer circumferential portion 31wo and an inner circumferential portion 31wi on the second surface. The inner circumferential portion 31wi is a region extending from the center 310 to a predetermined position in the radial direction, and the outer circumferential portion 31wo is a region radially outward of the inner circumferential portion 31wi.

[0033] As shown in FIG. 6 , an outer peripheral portion 31wo of the second surface of the ring beam shaping element 31w has an outer peripheral concave-convex pattern in which a plurality of convex portions 311 (first convex portions) and concave portions 312 (first concave portions) are arranged in the circumferential direction. In the example shown in FIG. 6 , the number of convex portions 311 or concave portions 312 formed in the circumferential direction is 24. The convex portions 311 are formed at angular positions every 15 degrees, and the concave portions 312 are formed at angular positions every 15 degrees between two adjacent convex portions 311. The number of convex portions 311 or concave portions 312 in the outer peripheral portion 31wo is 6 to 31, and preferably 10 to 31. When center lines passing through the circumferential centers of the convex portions 311 and concave portions 312 are extended toward the center 310, all center lines converge at the center 310.

[0034] An inner peripheral portion 31wi of the second surface of the ring beam shaping element 31w has an inner peripheral uneven pattern formed thereon, in which a plurality of convex portions 313 (second convex portions) and concave portions 314 (second concave portions) are arranged in the circumferential direction. In the example shown in FIG. 6 , the number of convex portions 313 or concave portions 314 formed in the circumferential direction is 16. The convex portions 313 are formed at angular positions every 22.5 degrees, and the concave portions 314 are formed at angular positions every 22.5 degrees between two adjacent convex portions 313. The number of convex portions 313 or concave portions 314 in the inner peripheral portion 31wi is 6 to 31, and preferably 10 to 31. The convex portions 313 and concave portions 314 are formed radially outward from the center 310 in the radial direction to the inner peripheral end of the outer peripheral portion 31wo.

[0035] The number of convex portions 313 or concave portions 314 in the inner peripheral portion 31wi may be more or less than the number of convex portions 311 or concave portions 312 in the outer peripheral portion 31wo. When the number of convex portions 313 or concave portions 314 is less than the number of convex portions 311 or concave portions 312 and the difference in numbers is relatively large, a double ring beam as shown in Fig. 7 can be obtained from the laser beam. When the difference in numbers between the two is small, the double ring beams overlap in the radial direction, resulting in a thick ring beam as shown in Fig. 8.

[0036] <Third Embodiment> Figure 9 shows a laser processing machine 300 according to a third embodiment. In Figure 9, the same parts as in Figure 1 are given the same reference numerals, and their description will be omitted. The processing head 30 in the laser processing machine 300 is equipped with ring beam shaping elements 31s1 and 31s2 instead of the ring beam shaping element 31s. The ring beam shaping elements 31s1 and 31s2 have the same shape as the ring beam shaping element 31s shown in Figure 2. In other words, the laser processing machine 300 is equipped with two ring beam shaping elements 31s.

[0037] The ring beam shaping elements 31s1 and 31s2 are arranged in the processing head 30 so that the second surfaces on which the convex portions 311 and concave portions 312 are formed face each other. In the ring beam shaping element 31s2, the incident surface of the laser beam is the second surface, and the exit surface is the flat first surface. The ring beam shaping elements 31s1 and 31s2 are preferably as close to each other as possible within the range in which the ring beam shaping element 31s2 can rotate. Through verification by the present inventors, it has been confirmed that the interval between the ring beam shaping elements 31s1 and 31s2 is preferably 1.5 mm or less.

[0038] The laser processing machine 300 includes a rotation drive unit 40 that drives, for example, the ring beam shaping element 31s2 of the ring beam shaping elements 31s1 and 31s2, to rotate it in a plane perpendicular to the optical axis of the laser beam emitted from the emission end of the optical fiber 25. The ring beam shaping element 31s1 has a fixed rotation direction and a fixed position in the optical axis direction, while the ring beam shaping element 31s2 has a fixed position in the optical axis direction. The ring beam shaping element 31s1 may be rotatable, and the rotation drive unit 40 may drive the ring beam shaping element 31s1 to rotate.

[0039] The rotary drive unit 40 may be configured with a hollow motor, the ring beam shaping element 31s2 may be fixed to the hollow motor, and the ring beam shaping element 31s2 may be rotated by the hollow motor. In this case, the hollow motor functioning as the rotary drive unit 40 is disposed on the optical axis.

[0040] When the convex portion 311 of the ring beam shaping element 31s1 and the convex portion 311 of the ring beam shaping element 31s2 exactly face each other, both the diffraction by the ring beam shaping element 31s1 and the diffraction by the ring beam shaping element 31s2 act to shape the incident laser beam into a ring beam. Therefore, the ring beam shown in Fig. 10A is obtained. In this case, if the sum of the design depth h of the convex portion 311 of the ring beam shaping element 31s1 and the design depth h of the convex portion 311 of the ring beam shaping element 31s2 is the same as the design depth h of the ring beam shaping element 31s, a ring beam substantially the same as that obtained when one ring beam shaping element 31s is used.

[0041] When the convex portion 311 of the ring beam shaping element 31s1 and the concave portion 312 of the ring beam shaping element 31s2 are exactly opposite to each other, the diffraction by the ring beam shaping element 31s1 and the diffraction by the ring beam shaping element 31s2 cancel each other out, thereby obtaining only the central beam as shown in FIG.

[0042] When the convex portion 311 of the ring beam shaping element 31s1 and the convex portion 311 of the ring beam shaping element 31s2 are opposed to each other with a circumferential offset of half a degree, a ring beam having a state intermediate between that of FIGS. 10A and 10C is obtained, as shown in FIG. 10B.

[0043] According to the laser processing machine 300, various beam profiles can be selected by changing the angle of the ring beam shaping element 31s2 relative to the ring beam shaping element 31s1. When the thickness of the metal sheet W is thin, the laser processing machine 300 may cut the metal sheet W with the Gaussian laser beam shown in Fig. 10C, and when the thickness of the metal sheet W is thick, the laser processing machine 300 may cut the metal sheet W with the ring laser beam shown in Fig. 10A or 10B.

[0044] <Fourth Embodiment> Figure 11 shows a laser processing machine 400 according to a fourth embodiment. In Figure 11, the same parts as in Figure 9 are given the same reference numerals, and their description will be omitted. The processing head 30 in the laser processing machine 400 is equipped with ring beam shaping elements 31w1 and 31w2 instead of the ring beam shaping elements 31s1 and 31s2 equipped in the processing head 30 in the laser processing machine 300. The ring beam shaping elements 31w1 and 31w2 have the same shape as the ring beam shaping element 31w shown in Figure 6. In other words, the laser processing machine 400 is equipped with two ring beam shaping elements 31w.

[0045] The ring beam shaping elements 31w1 and 31w2 are arranged in the processing head 30 so that the second surfaces on which the convex portions 311 and 313 and the concave portions 312 and 314 are formed face each other. In the laser processing machine 400 as well, the ring beam shaping elements 31w1 and 31w2 are preferably spaced apart by 1.5 mm or less.

[0046] The rotation drive unit 40 drives the ring beam shaping elements 31w1 and 31w2, for example, the ring beam shaping element 31w2, to rotate. The ring beam shaping element 31w1 has a fixed rotation direction and a fixed position in the optical axis direction, while the ring beam shaping element 31w2 has a fixed position in the optical axis direction. The ring beam shaping element 31w1 may be rotatable, and the rotation drive unit 40 may drive the ring beam shaping element 31w1 to rotate. The configuration in which the rotation drive unit 40 rotates the ring beam shaping element 31w1 may be the same as that shown in FIG. 9.

[0047] According to the laser processing machine 400, various beam profiles can be selected by changing the angle of the ring beam shaping element 31w2 relative to the ring beam shaping element 31w1.

[0048] The present invention is not limited to one or more of the above-described embodiments, and various modifications can be made without departing from the spirit and scope of the present invention.

[0049] This application claims priority based on Japanese Patent Application No. 2024-115510, filed with the Japan Patent Office on July 19, 2024, the entire disclosure of which is incorporated herein by reference.

Claims

1. A ring beam shaping element comprising: a first surface which is one of the entrance surface and exit surface of a laser beam and is a flat surface; and a second surface which is the other of the entrance surface and the exit surface; wherein a concave-convex pattern consisting of a plurality of convex portions and concave portions radially outward from the center of the second surface is formed on the second surface at a plurality of angular positions that are evenly spaced circumferentially; the distance between the first surface and the surface of the convex portions formed on the second surface is 2 mm or less; the convex portions have a uniform height from the center to the outermost position in the radial direction, and the concave portions have a uniform depth from the center to the outermost position in the radial direction; and the number of convex portions or concave portions in the concave-convex pattern is 6 to 31.

2. The ring beam shaping element according to claim 1, wherein the number of said convex portions or said concave portions of said concave-convex pattern is 10 or more and 31 or less.

3. A laser oscillator that emits a laser beam; an optical fiber that transmits the laser beam emitted from the laser oscillator; and a processing head into which a diverging laser beam having a Gaussian beam profile emitted from the emission end of the optical fiber is incident, wherein the processing head has: a collimating lens that converts the diverging laser beam into collimated light; a focusing lens that focuses the collimated laser beam emitted from the collimating lens and irradiates a workpiece with the focused laser beam; and a ring beam shaping element that is disposed between the emission end of the optical fiber and the collimating lens and converts the Gaussian beam profile into a ring beam profile, wherein the ring beam shaping element has: a first surface that is a flat surface and is one of an entrance surface onto which the diverging laser beam is incident and an exit surface from which the laser beam converted into the ring beam profile exits; and a second surface that is the other of the entrance surface and the exit surface. A laser processing machine in which an uneven pattern consisting of a plurality of convex portions and concave portions radially extending from the center of the second surface outward in the radial direction is formed on the second surface at a plurality of angular positions that are evenly spaced circumferentially, the distance between the first surface and the surfaces of the convex portions formed on the second surface is 2 mm or less, the convex portions have a uniform height from the center to the outermost position in the radial direction, and the concave portions have a uniform depth from the center to the outermost position in the radial direction, and the number of the convex portions or concave portions in the uneven pattern is 6 or more and 31 or less.

4. The laser processing machine according to claim 3, wherein the processing head has two of the ring beam shaping elements arranged closely together with the second surfaces facing each other, and the laser processing machine further comprises a rotation drive unit that drives one of the two ring beam shaping elements to rotate in a plane perpendicular to the optical axis.

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