A two-piece Bessel beam shaping system with diffraction rings

Abstract

The present invention discloses a two-piece Bessel beam shaping system with diffraction rings, which belongs to the field of laser processing technology and includes: a beam shaping mirror and a focusing mirror arranged in sequence along the direction of the optical path; the incident surface and the exit surface of the beam shaping mirror are both aspherical surfaces, which are used to shape the collimated Gaussian beam into a flat-top beam that exits in parallel; the incident surface and the exit surface of the focusing mirror are respectively an aspherical surface and a plane surface, which are used to focus the flat-top beam into a Bessel beam with diffraction rings. The present invention has a simple structure and only uses a two-piece structure including a beam shaping mirror and a focusing mirror to effectively remove processing materials such as ink during a single laser processing process. In addition, the focal depth of the Bessel beam in the present invention is adjustable, which is highly flexible and suitable for different laser processing scenarios.

Description

Technical Field

[0001] The present invention belongs to the technical field of laser processing, and more specifically, relates to a two-piece Bessel beam shaping system with a diffraction ring. Background Art

[0002] The traditional method for cutting glass and sapphire is a mechanical method, which has the disadvantages of low scribing quality and low precision, and generally produces microcracks and chipping. After mechanical cutting, many additional time-consuming post-processing steps are required to achieve the required tolerance of the final component's external dimensions. Traditional laser cutting of glass is an ablation mechanism, which has problems such as slag formation on the incision surface, wide kerf, excessive heat-affected zone, microcracks, residual stress, recast layer and other defects that are difficult to fully control. Due to its non-diffraction characteristics and uniform and narrow light field distribution, Bessel beams can maintain stable light intensity during long-distance transmission, which can achieve high-precision and high-efficiency processing and reduce the heat-affected zone. By using Bessel beams for deep cutting processes, the disadvantages mentioned above can be avoided. Therefore, it is of great significance to study a Bessel beam shaping system.

[0003] Existing Bessel beam shaping systems usually use an axicon to directly shape a Gaussian beam into a Bessel beam. The beam energy is concentrated and can only achieve cutting functions. During the processing, it is unable to selectively remove processing materials such as PVD and ink, requiring secondary processing. Summary of the Invention

[0004] In response to the above defects or improvement needs of the prior art, the present invention provides a two-piece Bessel beam shaping system with diffraction rings to solve the technical problem that the prior art cannot selectively remove the processing material in one processing process.

[0005] In order to achieve the above object, the present invention provides a two-piece Bessel beam shaping system with a diffraction ring, comprising: a beam shaping mirror and a focusing mirror arranged in sequence along the optical path;

[0006] The incident and exit surfaces of the beam shaping mirror are both aspherical, and are used to shape the collimated Gaussian beam into a parallel flat-top beam.

[0007] The incident surface and the exit surface of the focusing mirror are aspherical and flat respectively, and are used to focus the flat top beam into a Bessel beam with diffraction rings.

[0008] Further preferably, the surface parameters of the incident surface and the exit surface of the beam shaping mirror are determined by the following method:

[0009] Determine the coordinates of the incident light beam on the incident surface of the beam shaping mirror according to the collimated Gaussian beam parameters;

[0010] Substitute the energy distribution parameters of the flat-top beam spot generated by the flat-top beam on the exit surface of the beam shaping mirror into the energy conservation equation to solve for the coordinates of the flat-top beam on the exit surface of the beam shaping mirror. The energy conservation equation represents the energy conservation relationship between the incident beam on the incident surface of the beam shaping mirror and the flat-top beam emitted from the exit surface of the beam shaping mirror.

[0011] According to the coordinates of the incident light beam on the incident surface of the beam shaping mirror and the coordinates of the flat-top beam on the exit surface of the beam shaping mirror, the surface parameters of the incident surface and the exit surface of the beam shaping mirror are solved.

[0012] Further preferably, the energy distribution parameters of the flat-top spot include: the radius and light intensity distribution of the flat-top spot.

[0013] Further preferably, the above energy conservation equation is:

[0014]

[0015] Wherein, the beam cross section of the incident light beam on the incident surface of the beam shaping mirror is denoted as beam cross section A; the light spot on the beam cross section A is a circular light spot, the center of which is denoted as point O; r is the distance between any coordinate point P on the beam cross section A and point O; I in (r') is the light intensity at the radius r' on the beam cross section A; r'∈[0,r]; r max is the maximum distance between all coordinate points on the beam cross section A and point O; r”∈[0,r max ]; the beam cross section of the flat-top beam on the exit surface of the beam shaping mirror is denoted as beam cross section B; the light spot on beam cross section B is the flat-top light spot, and its center point is denoted as point O'; R is the distance between the coordinate point corresponding to coordinate point P on beam cross section B and point O'; I out (R') is the light intensity at the point with radius R' on the beam cross section B; R'∈[0,R1]; R1 is the radius of the flat-top spot; R"∈[0,R1].

[0016] Further preferably, the materials of the beam shaping mirror, the first collimating mirror and the focusing mirror are all fused quartz glass.

[0017] Further preferably, the Bessel beam shaping system further comprises a collimating lens arranged before the beam shaping lens, for collimating the Gaussian beam.

[0018] Further preferably, the Bessel beam shaping system further comprises a laser arranged before the collimating mirror for generating a Gaussian beam.

[0019] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0020] 1. This invention provides a two-piece Bessel beam shaping system with diffraction rings. A beam shaping lens shapes a Gaussian beam into a flat-top spot before a focusing lens, which then focuses it into a Bessel beam with diffraction rings. The energy carried by the diffraction rings is sufficient to ablate and remove protective processing materials around the kerf during the cutting process, eliminating the need for secondary processing and effectively removing processing materials such as ink in a single laser process. Furthermore, this invention utilizes only a two-piece structure consisting of a beam shaping lens and a focusing lens, resulting in a simple structure.

[0021] 2. The two-piece Bessel beam shaping system with diffraction rings provided by the present invention has a beam shaping function separated from focusing. Bessel beams with different focal depths can be achieved by replacing the focusing lens. It has high flexibility and is suitable for different laser processing scenarios.

[0022] 3. The two-piece Bessel beam shaping system with diffraction rings provided by the present invention has an aspheric incident surface and an aspheric exit surface of the beam shaping mirror, and an aspheric incident surface and a flat surface of the focusing mirror. The aspheric surface is simple to process and has low cost, and can be processed into a high-finish surface. The lens has high transmittance, low absorption loss and diffraction loss, and can withstand higher laser power. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 A schematic structural diagram of a two-piece Bessel beam shaping system with diffraction rings provided by the present invention;

[0024] Figure 2 A schematic diagram of a light spot of a Bessel beam with diffraction rings formed on a focal plane according to an embodiment of the present invention;

[0025] Figure 3 A schematic diagram of the focal depth provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0026] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is 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 for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0027] In order to achieve the above object, the present invention provides a two-piece Bessel beam shaping system with diffraction rings, such as Figure 1 As shown, it includes: a beam shaping mirror 1 and a focusing mirror 2 arranged in sequence along the light path direction;

[0028] The incident and exit surfaces of the beam shaping mirror are both aspherical surfaces (which may be annular even-order aspherical surfaces or annular odd-order aspherical surfaces, which are not limited here), and are used to shape the collimated Gaussian beam into a parallel flat-top beam;

[0029] The incident surface and the exit surface of the focusing mirror are respectively an aspheric surface (which can be an annular even-order aspheric surface or an annular odd-order aspheric surface, which is not limited here) and a plane, which are used to focus the flat-top beam into a Bessel beam with a diffraction ring.

[0030] The Gaussian beam is shaped into a flat-top spot in front of the focusing lens through a beam shaping lens, and then focused into a Bessel beam with diffraction rings by the focusing lens. In the field of laser processing, it can effectively increase the cutting depth of the material and can also effectively remove processing materials such as ink.

[0031] In an optional embodiment, the surface parameters of the incident surface and the exit surface of the beam shaping mirror are determined by the following method:

[0032] Determine the coordinates of the incident light beam on the incident surface of the beam shaping mirror according to the collimated Gaussian beam parameters;

[0033] Substitute the energy distribution parameters of the flat-top spot generated by the flat-top beam on the exit surface of the beam shaping mirror into the energy conservation equation to solve for the coordinates of the flat-top beam on the exit surface of the beam shaping mirror. The energy conservation equation represents the energy conservation relationship between the incident beam on the incident surface of the beam shaping mirror and the flat-top beam emitted from the exit surface of the beam shaping mirror. It should be noted that the energy distribution parameters of the flat-top spot are predetermined by the user based on their needs.

[0034] According to the coordinates of the incident light beam on the incident surface of the beam shaping mirror and the coordinates of the flat-top beam on the exit surface of the beam shaping mirror, the surface parameters of the incident surface and the exit surface of the beam shaping mirror can be solved based on the geometric relationship of the optical path.

[0035] It should be noted that the energy mapping relationship between the incident light beam on the incident surface of the beam shaping mirror and the flat-top beam emitted from the exit surface of the beam shaping mirror is rotationally symmetric. In an optional embodiment, a same-direction mapping mode is used to represent the energy mapping relationship between the incident light beam on the incident surface of the beam shaping mirror and the flat-top beam emitted from the exit surface of the beam shaping mirror, that is, the upper part of the incident light beam on the incident surface of the beam shaping mirror corresponds to the upper part of the flat-top spot, and the lower part of the incident light beam on the incident surface of the beam shaping mirror corresponds to the lower part of the flat-top spot. Specifically, the range of the incident light beam is [0, r max ] corresponds to the range of the flat-top spot [0, R1]; at this time, the above energy conservation relationship is:

[0036]

[0037] Wherein, the beam cross section of the incident light beam on the incident surface of the beam shaping mirror is denoted as beam cross section A; the light spot on the beam cross section A is a circular light spot, the center of which is denoted as point O; r is the distance between any coordinate point P on the beam cross section A and point O; I in (r') is the light intensity at the radius r' on the beam cross section A; r'∈[0,r]; r max is the maximum distance between all coordinate points on the beam cross section A and point O; r”∈[0,r max ]; the beam cross section of the flat-top beam on the exit surface of the beam shaping mirror is denoted as beam cross section B; the light spot on beam cross section B is the flat-top light spot, and its center point is denoted as point O'; R is the distance between the coordinate point corresponding to coordinate point P on beam cross section B and point O'; I out (R') is the light intensity at the point with radius R' on the beam cross section B; R'∈[0,R1]; R1 is the radius of the flat-top spot; R"∈[0,R1].

[0038] The above energy conservation equation gives the corresponding relationship R(r) between the coordinates of a point with radius r on beam cross section A and the coordinates of a point with radius R on beam cross section B. Since the coordinates of the incident beam at the beam shaping mirror entrance surface are known, the coordinates of points at different radii on beam cross section A are also known. In other words, the coordinates of any coordinate point P on beam cross section A are known. Therefore, based on the corresponding relationship R(r), the corresponding R can be solved, thereby determining the coordinates of the coordinate point P' on beam cross section B corresponding to coordinate point P, and thus the coordinates of the flattened beam on the beam shaping mirror exit surface.

[0039] It should be noted that the above energy conservation equation is only an example of an expression. It can also be constructed using mapping modes such as reverse mapping and cross mapping, and the energy conservation equation can also be adjusted accordingly. When reverse mapping is used, the upper part of the incident beam corresponds to the upper part of the flat-top spot, and the lower part of the incident beam corresponds to the lower part of the flat-top spot. Unlike the isotropic mapping, the upper edge of the incident beam corresponds to the upper inner diameter of the flat-top spot, and the center of the incident beam corresponds to the upper outer diameter of the flat-top spot. Specifically, the range of the incident beam [0, r amx ] corresponds to the range of the flat top spot [0, R1]. When cross mapping is used, the upper part of the incident beam corresponds to the upper part of the flat top spot, and the lower part of the incident beam corresponds to the lower part of the flat top spot. Specifically, the range of the incident beam [0, r max ] corresponds to the range of the flat-top spot [-R1,0].

[0040] The schematic diagram of the Bessel beam spot with diffraction rings formed on the focal plane is as follows Figure 2 shown.

[0041] It should be noted that the materials of the beam shaping and focusing lenses can be fused silica glass, N-BK7, N-SF11, etc. In one optional embodiment, the materials of the beam shaping and focusing lenses are both fused silica glass; the beam wavelength used by the Bessel beam shaping system is 1064 nm, and the refractive index of fused silica glass at 1064 nm is 1.4496 at room temperature.

[0042] In an optional embodiment, the Bessel beam shaping system further includes a collimating mirror disposed before the beam shaping mirror, for collimating the Gaussian beam.

[0043] Figure 3 A schematic diagram of the focal depth provided by an embodiment of the present invention shows that when the focal depth is within the range of [0.1 mm, 0.9 mm], the energy parity of the generated Bessel beam is high. This indicates that the present invention can achieve Bessel beams with varying focal depths, with adjustable focal depths and high flexibility.

[0044] In summary, the two-piece Bessel beam shaping system with diffraction rings provided by the present invention can shape the collimated Gaussian beam, and after passing through the focusing lens, generate a Bessel beam with diffraction rings on the working surface. It can effectively remove processing materials such as ink during a single laser processing process, and can also adjust the focal depth of the Bessel beam according to the actual thickness of the processing material; specifically, the focal depth of the Bessel beam can be adjusted by replacing different focusing lenses, which is suitable for multiple fields such as laser drilling and cutting.

[0045] It will be easily understood by those skilled in the art 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 in the scope of protection of the present invention.

Claims

1. A two-piece Bessel beam shaping system with diffraction rings, characterized in that: include: Beam shaping mirrors and focusing mirrors are arranged in sequence along the light path; The incident surface and the exit surface of the beam shaping mirror are both aspherical, and are used to shape the collimated Gaussian beam into a parallel flat-top beam; The incident surface and the exit surface of the focusing mirror are respectively an aspheric surface and a flat surface, and are used to focus the flat-top beam into a Bessel beam with diffraction rings.

2. The Bessel beam shaping system according to claim 1, wherein: The surface parameters of the beam shaping mirror entrance and exit surfaces are determined by the following method: Determine the coordinates of the incident light beam on the incident surface of the beam shaping mirror according to the collimated Gaussian beam parameters; Substituting the energy distribution parameters of the flattened light spot generated by the flattened light beam on the exit surface of the beam shaping mirror into the energy conservation equation, and solving for the coordinates of the flattened light beam on the exit surface of the beam shaping mirror; the energy conservation equation represents the energy conservation relationship between the incident light beam on the incident surface of the beam shaping mirror and the flattened light beam emitted from the exit surface of the beam shaping mirror; According to the coordinates of the incident light beam on the incident surface of the beam shaping mirror and the coordinates of the flat-top beam on the exit surface of the beam shaping mirror, the surface parameters of the incident surface and the exit surface of the beam shaping mirror are solved.

3. The Bessel beam shaping system according to claim 2, wherein: The energy distribution parameters of the flat-top light spot include: the radius and light intensity distribution of the flat-top light spot.

4. The Bessel beam shaping system according to claim 2, wherein: The energy conservation equation is: Wherein, the beam cross section of the incident light beam on the incident surface of the beam shaping mirror is denoted as beam cross section A; the light spot on the beam cross section A is a circular light spot, the center of which is denoted as point O; r is the distance between any coordinate point P on the beam cross section A and point O; I in (r') is the light intensity at the radius r' on the beam cross section A; r'∈[0,r]; r max is the maximum distance between all coordinate points on the beam cross section A and point O; r"∈[0,r max ]; the beam cross section of the flat-top beam on the exit surface of the beam shaping mirror is denoted as beam cross section B; the light spot on the beam cross section B is denoted as the flat-top light spot, and its center point is denoted as point O'; R is the distance between the coordinate point corresponding to the coordinate point P on the beam cross section B and point O'; I out (R') is the light intensity at the radius R' on the beam cross section B; R'∈[0,R1]; R1 is the radius of the flat-top spot; R"∈[0,R1].

5. The Bessel beam shaping system according to any one of claims 1 to 4, wherein: The beam shaping mirror and the focusing mirror are both made of fused quartz glass.

6. The Bessel beam shaping system according to any one of claims 1 to 4, characterized in that: It also includes a collimating mirror arranged before the beam shaping mirror, which is used to collimate the Gaussian beam.

7. The Bessel beam shaping system according to claim 6, wherein: The invention also includes a laser arranged before the collimating mirror, for generating a Gaussian beam.

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