A three-piece bessel beam shaping system with a diffraction ring

Abstract

The application discloses a three-piece Bessel beam shaping system with a diffraction ring, and belongs to the technical field of laser processing, comprising: a beam shaping mirror, a first collimating mirror and a focusing mirror; the incident surface and the exit surface of the beam shaping mirror are annular planes and annular aspheric surfaces respectively, and are used for shaping a collimated Gaussian beam into a point annular beam with energy gradually decreasing from inside to outside; the incident surface and the exit surface of the first collimating mirror are annular aspheric surfaces and annular planes respectively, and are used for collimating the point annular beam; the incident surface of the focusing mirror is a combination of an axicon surface and a spherical surface, and the exit surface is a plane; the focusing mirror is used for focusing the collimated point annular beam into a Bessel beam with a diffraction ring. The application can significantly improve the focal depth of the Bessel beam in laser processing, and can also effectively remove processing materials such as ink. In addition, the focal depth of the Bessel beam in the application is adjustable, and the adjustment mode is more, the flexibility is higher, and is suitable for different laser processing scenes.

Description

Technical Field

[0001] This invention belongs to the field of laser processing technology, and more specifically, relates to a three-piece Bessel beam shaping system with diffraction rings. Background Technology

[0002] Traditional glass and sapphire cutting methods are mechanical, which suffers from low scribing quality and precision, often resulting in microcracks and breakage. After mechanical cutting, numerous time-consuming post-processing steps are required to achieve the desired dimensional tolerances of the final component. Traditional laser cutting of glass utilizes an ablation mechanism, leading to problems such as slag formation on the cut surface, wide kerf, excessively large heat-affected zone, microcracks, residual stress, and recast layers, all of which are difficult to control completely. Bessel beams, due to their non-diffraction characteristics and uniform, narrow light field distribution, maintain stable light intensity over long distances, enabling high-precision, high-efficiency processing and reducing the heat-affected zone. By using Bessel beams in deep cutting processes, the aforementioned drawbacks can be avoided. Therefore, researching a Bessel beam shaping system is of significant importance.

[0003] Existing Bessel beam shaping systems typically use an axon cone to directly shape a Gaussian beam into a Bessel beam. This results in strong vibrations at the center of the beam, a short usable depth of focus, and limited depth of focus, making it difficult to achieve deep cutting. The thickness of the glass being cut is often only from 0.1 to 10 mm. Furthermore, current cutting systems have concentrated beam energy, enabling only cutting and failing to selectively remove PVD, ink, or other processing materials during the process, requiring secondary processing. Summary of the Invention

[0004] In view of the above-mentioned defects or improvement needs of the prior art, the present invention provides a three-piece Bessel beam shaping system with diffraction rings to solve the technical problems of the limited depth of the laser focus and the inability to selectively remove the processed material in a single processing step.

[0005] To achieve the above objectives, the present invention provides a three-piece Bessel beam shaping system with a diffraction ring, comprising: a beam shaping mirror, a first collimating mirror, and a focusing mirror arranged sequentially along the optical path direction;

[0006] The incident and exit surfaces of the beam shaping mirror are an annular plane and an annular aspherical surface, respectively, which are used to shape the collimated Gaussian beam into a point annular beam with energy decreasing from the inside to the outside.

[0007] The first collimating mirror has an incident surface and an exit surface that are an annular aspherical surface and an annular plane, respectively, and is used to collimate the point annular beam.

[0008] The incident surface of the focusing lens is one of the combined surface and the plane, and the exit surface is the other of the combined surface and the plane; the focusing lens is used to focus the collimated point ring beam into a Bessel beam with diffraction rings.

[0009] The combined surface is an aspherical surface, consisting of an axial cone and a sphere, starting from the side closest to the focusing lens. The cross-sectional radius of the sphere perpendicular to the optical path is within the range of [0, r1], and the cross-sectional radius of the axial cone perpendicular to the optical path is within the range of (r1, r2). r1 is a value smaller than the inner diameter of the point ring beam, and r2 is a preset radius.

[0010] More preferably, the parameters of the beam shaping mirror exit surface are determined in the following manner:

[0011] Based on the collimated Gaussian beam parameters, determine the coordinates of the incident beam on the exit surface of the beam shaping mirror.

[0012] Based on the required Bessel beam parameters, determine the energy distribution parameters of the point ring beam produced by the point ring beam on the incident surface of the first collimating mirror.

[0013] Substitute the energy distribution parameters of the point ring beam into the energy conservation equation to solve for the coordinates of the point ring beam on the incident surface of the first collimating mirror; where the energy conservation equation represents the energy conservation relationship between the incident beam at the exit surface of the beam shaping mirror and the point ring beam incident on the incident surface of the first collimating mirror.

[0014] Based on the coordinates of the incident beam on the exit surface of the beam shaper and the coordinates of the point ring beam on the incident surface of the first collimator, the surface shape parameters of the exit surface of the beam shaper are solved.

[0015] Based on the predetermined proportion of the energy of the diffraction rings in the Bessel beam to the total energy of the Bessel beam, the inner diameter of the exit surface of the beam shaping mirror is determined.

[0016] More preferably, the energy distribution parameters of the aforementioned point-ring light spot include: the inner diameter and outer diameter of the point-ring light spot, and the light intensity distribution of the point-ring light spot; the light intensity distribution of the point-ring light spot includes: the light intensity at the center point of the point-ring light spot and the light intensity at different radii.

[0017] More preferably, the above energy conservation equation is:

[0018]

[0019] Here, the beam section of the incident beam on the exit surface of the beam shaping mirror is denoted as beam section A; the light spot on beam section A is a circular light spot, and its center point is denoted as point O. rLet P be the distance between any coordinate point P and point O on the beam cross section A; The radius of the beam cross section A is The light intensity at that location; ; This represents the maximum distance between all coordinate points on beam section A and point O; The beam section of the point ring beam on the incident surface of the first collimating mirror is called beam section B; the spot on beam section B is called the point ring spot, and its center point is called O'. R The distance between point O' on beam section B, corresponding to point P; The radius of the beam cross section B is The light intensity at that location; ; R 1 and R 2 represents the inner and outer diameters of the dotted ring-shaped light spot, respectively; .

[0020] More preferably, the inclination angle of the axial cone surface of the axial cone mirror... satisfy:

[0021]

[0022] in, The refractive index of the cone mirror material is denoted by . R 1 represents the inner diameter of the point ring beam on the incident surface of the first collimating mirror. This is the distance between the exit surface of the focusing lens and the focal point.

[0023] More preferably, the focal length of the sphere is:

[0024]

[0025] Where z is the preset focal depth.

[0026] More preferably, the beam shaping mirror, the first collimating mirror, and the focusing mirror are all made of fused silica glass.

[0027] More preferably, the Bessel beam shaping system further includes a second collimating mirror disposed in front of the beam shaping mirror for collimating the Gaussian beam.

[0028] More preferably, the aforementioned Bessel beam shaping system further includes a laser disposed in front of the second collimating mirror for generating a Gaussian beam.

[0029] In summary, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0030] 1. This invention provides a three-piece Bessel beam shaping system with diffraction rings, comprising a beam shaping mirror, a first collimating mirror, and a focusing mirror. The beam shaping mirror shapes a collimated Gaussian beam into a point-ring beam with energy decreasing sequentially from the inside out. After collimation, the focusing mirror focuses the beam into a Bessel beam with diffraction rings. This point-ring beam has a wider tilted ring energy distribution, significantly improving the uniformity of the Bessel beam during laser processing and avoiding the problem of strong vibrations in the central light intensity. This increases the depth of focus of the Bessel beam during laser processing, solving the technical problem of limited focal depth in existing laser technologies. Simultaneously, because the generated Bessel beam has diffraction rings, the energy carried by the diffraction rings is sufficient to ablate and remove the protective processing material around the kerf during the cutting process, eliminating the need for secondary processing. Therefore, it can also effectively remove processing materials such as ink during laser processing, solving the technical problem that existing technologies cannot selectively remove processing materials in a single processing step.

[0031] 2. The three-piece Bessel beam shaping system with diffraction rings provided by this invention separates beam shaping from focusing. By changing the focusing mirror with different axial cone tilt angles, Bessel beams with different focal depths can be achieved. Furthermore, the width of the point ring spot corresponding to the point ring beam can be adjusted by using beam shapers with different structures and relative sizes and a first collimating mirror, thereby adjusting the focal depth of the Bessel beam. The focal depth of the Bessel beam generated by this invention is adjustable, with multiple adjustment methods, offering high flexibility and suitability for various laser processing scenarios.

[0032] 3. The three-piece Bessel beam shaping system with diffraction rings provided by the present invention has an annular plane and an annular aspherical surface as the incident and exit surfaces of the beam shaping mirror, respectively, and an annular aspherical surface and an annular plane as the incident and exit surfaces of the first collimating mirror, respectively. The aspherical surface is simple to process, has low cost, and can be processed into a high-gloss surface. The lens has high transmittance, low absorption loss and diffraction loss, and can withstand higher laser power. Attached Figure Description

[0033] Figure 1 A schematic diagram of the structure of a three-piece Bessel beam shaping system with diffraction rings provided by the present invention;

[0034] Figure 2 A schematic diagram of a Bessel beam with diffraction rings formed at the focal plane, provided in an embodiment of the present invention;

[0035] Figure 3 A schematic diagram of the focal depth length provided for an embodiment of the present invention. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0037] To achieve the above objectives, the present invention provides a three-piece Bessel beam shaping system with diffraction rings, such as... Figure 1 As shown, it includes: a beam shaping mirror 1, a first collimating mirror 2, and a focusing mirror 3 arranged sequentially along the optical path direction;

[0038] The incident and exit surfaces of the beam shaping mirror are an annular plane and an annular aspherical surface (which can be an even-order annular aspherical surface or an odd-order annular aspherical surface, and is not limited here). It is used to shape the collimated Gaussian beam into a point annular beam with energy decreasing from the inside to the outside, forming the desired point annular spot in front of the first collimating mirror.

[0039] The incident and exit surfaces of the first collimating lens are an annular aspherical surface (which can be an even-order annular aspherical surface or an odd-order annular aspherical surface, and this is not limited here) and an annular plane, respectively, which are used to collimate the point annular beam.

[0040] The focusing lens has one of the combined surface and the plane as its incident surface, and the other of the combined surface and the plane as its exit surface; the focusing lens is used to focus the collimated point ring beam into a Bessel beam with diffraction rings.

[0041] The combined surface is aspherical, consisting of an axial cone and a sphere, starting from the side closest to the focusing lens. The cone portion focuses the ring beam within the point ring beam into a Bessel beam, while the spherical portion focuses the point beam within the point ring beam into a diffraction ring of the Bessel beam. The cross-sectional radius of the sphere perpendicular to the optical path direction is within the range [0, r1], and the cross-sectional radius of the axial cone perpendicular to the optical path direction is within the range (r1, r2). r1 is a value smaller than the inner diameter of the point ring beam; r2 is a preset radius.

[0042] A Gaussian beam is shaped into a dotted ring spot in front of a first collimating mirror by a beam shaping mirror. After collimation, it is focused by a focusing mirror into a Bessel beam with diffraction rings. In the field of laser processing, this can effectively improve the cutting depth of materials and also effectively remove processed materials such as ink.

[0043] In one alternative implementation, the parameters of the beam-shaping mirror exit surface are determined in the following manner:

[0044] Based on the collimated Gaussian beam parameters, determine the coordinates of the incident beam on the exit surface of the beam shaping mirror.

[0045] Based on the required Bessel beam parameters, determine the energy distribution parameters of the point ring spot produced by the point ring beam on the incident surface of the first collimating mirror; wherein, the energy distribution parameters of the point ring spot include: the inner diameter and outer diameter of the point ring spot, and the light intensity distribution of the point ring spot; the light intensity distribution of the point ring spot includes: the light intensity at the center point of the point ring spot and the light intensity at different radii.

[0046] Specifically, ;in, z is the distance between the exit surface of the focusing lens and the focal point, i.e., the working distance; z is the preset depth of focus. The inclination angle of the axial cone surface of the focusing lens; is the refractive index of the focusing lens material.

[0047] Substitute the energy distribution parameters of the point ring beam into the energy conservation equation to solve for the coordinates of the point ring beam on the incident surface of the first collimating mirror; where the energy conservation equation represents the energy conservation relationship between the incident beam at the exit surface of the beam shaping mirror and the point ring beam incident on the incident surface of the first collimating mirror.

[0048] Based on the coordinates of the incident beam on the exit surface of the beam shaping mirror and the coordinates of the point ring beam on the incident surface of the first collimating mirror, the surface shape parameters of the exit surface of the beam shaping mirror can be obtained based on the geometric relationship of the optical path.

[0049] Based on the predetermined proportion of the energy of the diffraction rings in the Bessel beam to the total energy of the Bessel beam, the inner diameter of the exit surface of the beam shaping mirror is determined.

[0050] It should be noted that the energy mapping relationship between the incident beam at the exit surface of the beam shaping mirror and the point-ring beam incident on the entrance surface of the first collimating mirror is rotationally symmetric. In an optional embodiment, a unidirectional mapping mode is used to represent the energy mapping relationship between the incident beam at the exit surface of the beam shaping mirror and the point-ring beam incident on the entrance surface of the first collimating mirror, that is, the upper part of the incident beam corresponds to the upper part of the point-ring beam, and the lower part of the incident beam corresponds to the lower part of the point-ring spot. Specifically, the range of the incident beam... The range of the corresponding point ring spot [ R 1, R 2]; At this point, the above energy conservation equation is:

[0051]

[0052] Here, the beam section of the incident beam on the exit surface of the beam shaping mirror is denoted as beam section A; the light spot on beam section A is a circular light spot, and its center point is denoted as point O. rLet P be the distance between any coordinate point P and point O on the beam cross section A; The radius of the beam cross section A is The light intensity at that location; ; This represents the maximum distance between all coordinate points on beam section A and point O; The beam section of the point ring beam on the incident surface of the first collimating mirror is called beam section B; the spot on beam section B is called the point ring spot, and its center point is called O'. R The distance between point P' on beam section B, corresponding to point P, and point O'; The radius of the beam cross section B is The light intensity at that location; ; R 1 and R 2 represents the inner and outer diameters of the dotted ring-shaped light spot, respectively; .

[0053] The above energy conservation equation gives the radius of the beam cross section A as... r The coordinates at point B are the same as the radius on beam section B. R Correspondence between coordinates at location R ( r Since the coordinates of the incident beam on the exit surface of the beam shaping mirror are known, the coordinates of different radii on the beam cross-section A are also known. That is, the coordinates of any point P on the beam cross-section A are known. Therefore, based on the correspondence... R ( r The corresponding solution can be obtained by solving this problem. R This allows us to determine the coordinates of point P' on beam section B, which corresponds to coordinate point P, and thus obtain the coordinates of the point ring beam on the incident surface of the first collimating mirror.

[0054] Based on a predetermined ratio of the energy of the diffraction rings in the Bessel beam to the total energy of the Bessel beam. The formula for determining the inner diameter of the annular aspherical surface of the beam shaper is as follows:

[0055]

[0056] in, The inner diameter of the annular aspherical surface of the beam shaping mirror; The radius of the beam cross section A is The light intensity at that location.

[0057] It should be noted that the above energy conservation equation is only an example expression. It can also be constructed using reverse mapping, cross mapping, and other mapping methods, and the energy conservation equation will be adjusted accordingly. When using reverse mapping, the upper part of the incident beam corresponds to the upper part of the point ring spot, and the lower part of the incident beam corresponds to the lower part of the point ring spot. Unlike in-direction mapping, the upper edge of the incident beam corresponds to the upper inner diameter of the point ring spot, and the center of the incident beam corresponds to the upper outer diameter of the point ring spot. Specifically, the range of the incident beam... The range of the corresponding point ring spot [ R 1, R 2). When cross-mapping is used, the upper part of the incident beam corresponds to the upper part of the point ring spot, and the lower part of the incident beam corresponds to the lower part of the point ring spot. Specifically, the range of the incident beam... The range of the corresponding point ring spot [- R 2, - R 1).

[0058] It should be noted that the inclination angle of the axial cone surface of the axial cone mirror... satisfy:

[0059]

[0060] in, The refractive index of the cone mirror material is denoted by . R 1 represents the inner diameter of the point ring beam on the incident surface of the first collimating mirror. This is the distance between the exit surface of the focusing lens and the focal point, i.e., the working distance.

[0061] The focal length of the spherical surface of the axial cone is:

[0062]

[0063] Where z is the preset focal depth.

[0064] A schematic diagram of the Bessel beam with diffraction rings formed at the focal plane is shown below. Figure 2 As shown.

[0065] It should be noted that the beam shaping mirror, the first collimating mirror, and the focusing mirror can be made of fused silica glass, N-BK7, N-SF11, etc. In one optional embodiment, the beam shaping mirror, the first collimating mirror, and the focusing mirror are all made of fused silica glass; the beam wavelength used in the Bessel beam shaping system is 1064 nm, and at room temperature, the refractive index of fused silica glass at 1064 nm is 1.4496.

[0066] In one alternative implementation, the Bessel beam shaping system further includes a second collimating mirror disposed in front of the beam shaping mirror for collimating the Gaussian beam.

[0067] In one alternative implementation, the Bessel beam shaping system further includes a laser positioned before the second collimating mirror for generating a Gaussian beam.

[0068] Figure 3 The diagram illustrates the focal depth length provided in this embodiment of the invention. As can be seen from the diagram, when the focal depth length in this invention is within the range of [0mm, 20mm], the generated Bessel beam exhibits high energy uniformity, and the thickness of the workpiece being cut can reach 20mm. This demonstrates that the present invention can achieve Bessel beams with different focal depths, the focal depth length is adjustable, the range is wide, and it offers high flexibility.

[0069] In summary, the three-piece Bessel beam shaping system with diffraction rings provided by this invention can shape a collimated Gaussian beam, and after passing through an axial cone, generate a long-depth-of-focus Bessel beam with diffraction rings on the working surface. Furthermore, the depth of focus of the Bessel beam can be adjusted according to the thickness of the actual material being processed. Specifically, this is achieved by adjusting the width of the dotted ring spot and the tilt angle of the axial cone of the focusing lens. This invention adjusts the focal depth of the Bessel beam; the width of the dotted ring spot can be adjusted by replacing beam shaping mirrors and the first collimating mirror with different structures and relative sizes. Furthermore, since the generated Bessel beam has diffraction rings, it can effectively remove processing materials such as ink in laser processing. This invention realizes a three-piece Bessel beam shaping system with diffraction rings, which can effectively solve the problems of shallow and uneven laser processing depth and ineffective material removal, and is applicable to multiple fields such as laser drilling and cutting.

[0070] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A three-piece Bessel beam shaping system with a diffraction ring, characterized in that, The application relates to a Gauss-to-Bessel beam shaping device. The Gauss-to-Bessel beam shaping device comprises a light beam shaping mirror, a first collimating mirror and a focusing mirror arranged in sequence along the light path direction. The incident surface and the exit surface of the light beam shaping mirror are respectively an annular plane and an annular aspheric surface, and the light beam shaping mirror is used for shaping a collimated Gaussian light beam into a point annular light beam with energy gradually decreasing from inside to outside. The incident surface and the exit surface of the first collimating mirror are respectively an annular aspheric surface and an annular plane, and the first collimating mirror is used for collimating the point annular light beam. The incident surface of the focusing mirror is one of a combined surface and a plane, and the exit surface is the other one of the combined surface and the plane; the focusing mirror is used for focusing the collimated point annular light beam into a Bessel light beam with a diffraction ring. The combined surface is an aspheric surface, which comprises an axicon surface and a spherical surface arranged in sequence from the side close to the plane of the focusing mirror; the cross-sectional radius of the spherical surface perpendicular to the light path direction is in the range of [0, r1], and the cross-sectional radius of the axicon surface perpendicular to the light path direction is in the range of (r1, r2]; r1 is a value smaller than the inner diameter of the point annular light beam; and r2 is a preset radius.

2. The Bessel beam shaping system of claim 1, wherein, The parameters of the exit surface of the light beam shaping mirror are determined by the following method: According to the parameters of the collimated Gaussian light beam, the coordinates of the incident light beam on the exit surface of the light beam shaping mirror are determined. According to the required Bessel light beam parameters, the energy distribution parameters of the point annular light spot generated on the incident surface of the first collimating mirror are determined. The energy distribution parameters of the point annular light spot are substituted into an energy conservation relationship formula to solve the coordinates of the point annular light beam on the incident surface of the first collimating mirror; the energy conservation relationship formula represents the energy conservation relationship between the incident light beam on the exit surface of the light beam shaping mirror and the point annular light beam incident on the incident surface of the first collimating mirror. According to the coordinates of the incident light beam on the exit surface of the light beam shaping mirror and the coordinates of the point annular light beam on the incident surface of the first collimating mirror, the surface type parameters of the exit surface of the light beam shaping mirror are solved. According to the preset proportion of the energy of the diffraction ring in the total energy of the Bessel light beam, the inner diameter of the exit surface of the light beam shaping mirror is solved.

3. The Bessel beam shaping system of claim 2, wherein, The energy distribution parameters of the point annular light spot include the inner diameter and the outer diameter of the point annular light spot and the light intensity distribution of the point annular light spot; the light intensity distribution of the point annular light spot includes the light intensity at the center point of the point annular light spot and the light intensity at different radii.

4. The Bessel beam shaping system of claim 2, wherein, The energy conservation relationship formula is: Wherein, the light beam section of the incident light beam on the exit surface of the beam shaping mirror is a light beam section A; the light spot on the light beam section A is a circular light spot, and the center point is point O; r is the distance between any coordinate point P on the light beam section A and point O; is the light intensity at the point with a radius of on the light beam section A; ; is the maximum value of the distance between all coordinate points on the light beam section A and point O; ; the light beam section of the point annular light beam on the incident surface of the first collimating mirror is a light beam section B; the light spot on the light beam section B is the point annular light spot, and the center point is O'; R is the distance between the coordinate point corresponding to the coordinate point P on the light beam section B and point O'; is the light intensity at the point with a radius of on the light beam section B; ; R 1 and R 2 are the inner diameter and the outer diameter of the point annular light spot respectively; .

5. The Bessel beam shaping system according to any one of claims 1-4, wherein, The axial conical surface has an inclination angle Satisfies: wherein, n is the refractive index of the axicon material; R 1 is the inner diameter of the point-ring spot of the point-ring beam on the entrance surface of the first collimator; is the distance between the exit surface of the focusing mirror and the focal point.

6. The Bessel beam shaping system according to any one of claims 1-4, wherein, The focal length of the spherical surface is: wherein, is the distance between the exit surface of the focusing mirror to the focal point; z is the preset focal depth.

7. The Bessel beam shaping system according to any one of claims 1-4, wherein, The materials of the light beam shaping mirror, the first collimating mirror and the focusing mirror are fused quartz glass.

8. The Bessel beam shaping system according to any one of claims 1-4, wherein, The Gauss-to-Bessel beam shaping device further comprises a second collimating mirror arranged in front of the light beam shaping mirror and used for collimating the Gaussian light beam.

9. The Bessel beam shaping system of claim 8, wherein, The Gauss-to-Bessel beam shaping device further comprises a laser arranged in front of the second collimating mirror and used for generating the Gaussian light beam.

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