Laser beam shaping system

Abstract

The invention relates to a laser beam shaping system. The laser beam shaping system comprises a laser light source used for generating an initial light beam; the aspherical lens group is arranged on a propagation path of the laser beam and comprises a first lens, a second lens, a third lens and a fourth lens which are sequentially arranged from the object space to the image space along the incident direction of the light source; wherein the first lens and the second lens are plano-concave aspheric lenses and both have negative focal lengths; the third lens is a biconcave aspheric lens and has a negative focal length; the fourth lens is a biconvex aspheric lens and has a positive focal length; the initial light beam is collimated by the lens group to form a target flat-topped light beam, and meanwhile, the aperture of the light beam realizes beam expansion of a preset multiplying power.

Description

Technical Field

[0001] This application relates to the field of beam modulation technology, and in particular to a laser beam shaping system. Background Technology

[0002] Lasers, with their excellent monochromaticity, directionality, and high brightness, are widely used in various manufacturing and non-destructive testing technologies. However, the intensity distribution of a laser beam approximates a Gaussian distribution, meaning there is a significant difference in intensity between the beam center and the edges. This can lead to excessive energy concentration in certain areas of the beam, potentially compromising manufacturing precision or material properties. Therefore, shaping devices are often needed to fully distribute the laser beam energy, transforming it from a Gaussian distribution into a uniformly distributed, flat-top beam.

[0003] There are two main methods to achieve flat-top beam output in laser applications: one is to use diffractive optical elements (DOEs), and the other is to use aspherical mirror assemblies for shaping. The diffractive optical element method has a limited working distance and cannot guarantee collimation of the flat-top beam within a certain working distance, and it is also quite sensitive to the working wavelength. While aspherical shaping mirror assemblies can achieve collimated flat-top beam output over a longer working distance, their working distance is limited to no more than 50mm. If this range is exceeded, the energy distribution will be distorted, failing to meet the required processing specifications. Summary of the Invention

[0004] Therefore, it is necessary to provide a laser beam shaping system that can at least achieve the output of expanded flat-top light within a working distance of 50mm-2000mm, addressing the problems mentioned above in the background technology.

[0005] In a first aspect, this application provides a laser beam shaping system, comprising:

[0006] A laser light source is used to generate the initial beam;

[0007] An aspherical lens group, positioned along the propagation path of the laser beam, comprises: a first lens, a second lens, a third lens, and a fourth lens arranged sequentially from the object side to the image side along the incident direction of the light source; wherein,

[0008] The first and second lenses are plano-concave aspherical lenses, both with negative focal lengths;

[0009] The third lens is a biconcave aspherical lens with a negative focal length;

[0010] The fourth lens is a biconvex aspherical lens with a positive focal length;

[0011] The initial beam is collimated by the lens group to form the target flat-top beam, while the beam aperture is expanded by a preset magnification.

[0012] In some embodiments, the front surfaces of the first lens and the second lens are both planar, and the rear surfaces are both aspherical.

[0013] The front surfaces of the third and fourth lenses are both spherical, while the rear surfaces are both aspherical.

[0014] The front surface is used to characterize the surface closest to the beam input; the rear surface is used to characterize the surface closest to the beam output.

[0015] In some embodiments, the aspherical equation used for the aspherical lens group is:

[0016]

[0017] Where z is the sag of the optical axis, c is the reciprocal of the radius of curvature, k is the conic coefficient, and r is the radial coordinate of the coordinate axis, satisfying the following in the xy coordinate system: ; , , , , , , , These are coefficients of higher-order terms, and are dimensionless.

[0018] The aspherical conic coefficient k in the aspherical lens group is 0.

[0019] In some embodiments, the aspherical radius of curvature of the second lens is greater than that of the first lens;

[0020] The radius of curvature of the spherical surface of the third lens is less than zero;

[0021] The radius of curvature of the spherical surface of the fourth lens is greater than zero.

[0022] In some embodiments, the center thickness of the first lens ranges from 2.5mm to 3.5mm;

[0023] The center thickness of the second lens ranges from 3.5mm to 4.5mm.

[0024] The center thickness of the third lens ranges from 2.5mm to 3.5mm.

[0025] The center thickness of the fourth lens ranges from 6.5mm to 7.5mm.

[0026] In some embodiments, the first air gap between the first lens and the second lens is D1, the second air gap between the second lens and the third lens is D2, and the third air gap between the third lens and the fourth lens is D3.

[0027] The third air gap D3 satisfies 4D1 < D3 > 5D1; or

[0028] The third air gap D3 satisfies 4D2 < D3 > 5D2.

[0029] In some embodiments, the first lens, the second lens, and the third lens have the same refractive index and Abbe number;

[0030] The refractive index and Abbe number of the fourth lens are greater than those of the first lens.

[0031] In some embodiments, the first lens, the second lens, and the third lens are made of calcium fluoride.

[0032] The fourth lens is made of fused silica.

[0033] In some embodiments, the working distance of the aspherical lens group is 50mm-2000mm.

[0034] In some embodiments, the laser source is used to generate an initial beam of multiple wavelengths;

[0035] The laser beam shaping system also includes:

[0036] An adjustment base is used to adjust the air gap between the lenses in the aspherical lens group according to the wavelength of the initial beam.

[0037] In the laser beam shaping system described in the above embodiment, addressing the issues of insufficient working distance and excessive size of existing beam-expanding flat-top beam shaping mirrors, a combination of positive and negative non-optical focal lengths of four aspherical lenses (first lens, second lens, third lens, and fourth lens) is used to simultaneously achieve beam expansion and output of expanded flat-top beams within a working distance of 50mm-2000mm. The miniaturized design can meet the needs of small-space working environments while effectively optimizing beam energy distribution, solving the problem of localized energy concentration in traditional solutions, and meeting the requirements of high-precision manufacturing scenarios for energy uniformity and long working distances.

[0038] In addition, the combination of calcium fluoride and fused silica is chosen to ensure that the aspherical lens group can withstand high-power lasers and has a certain achromatic aberration capability, and is compatible with different wavelength lasers when used with the adjustment base. Attached Figure Description

[0039] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained from these drawings without creative effort.

[0040] Figure 1 This is a schematic diagram of the structure of the laser beam shaping system in this embodiment of the invention;

[0041] Figure 2 This is a schematic diagram of the optical path according to an embodiment of the present invention;

[0042] Figure 3 This is an initial beam energy distribution diagram of the incident beam according to an embodiment of the present invention;

[0043] Figure 4 This is a one-dimensional energy distribution diagram of the target flat-top beam output by the aspherical lens group in an embodiment of the present invention at a working distance of 50mm;

[0044] Figure 5 This is a one-dimensional energy distribution diagram of the target flat-top beam output by the aspherical lens group in an embodiment of the present invention at a working distance of 500mm;

[0045] Figure 6 This is a one-dimensional energy distribution diagram of the target flat-top beam output by the aspherical lens group in an embodiment of the present invention at a working distance of 1200mm;

[0046] Figure 7 This is a one-dimensional energy distribution diagram of the target flat-top beam output by the aspherical lens group in an embodiment of the present invention at a working distance of 2000mm.

[0047] Explanation of reference numerals in the attached figures:

[0048] 1. Laser source; 2. Aspherical lens group; 21. First lens; 22. Second lens; 23. Third lens; 24. Fourth lens; 301. First surface; 302. Second surface; 303. Third surface; 304. Fourth surface; 305. Fifth surface; 306. Sixth surface; 307. Seventh surface; 308. Eighth surface. Detailed Implementation

[0049] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0050] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0051] When using the terms “including,” “having,” and “comprising” as described herein, another component may be added unless explicitly qualifying terms such as “only,” “consisting of,” etc. are used. Unless otherwise stated, singular terms may include plural forms and should not be construed as having a quantity of one.

[0052] It should be understood that although the terms “first,” “second,” etc., may be used herein to describe various elements, these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, without departing from the scope of this application, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element.

[0053] In this application, unless otherwise expressly specified and limited, the terms "connected" and "linked" should be interpreted broadly. For example, they can refer to a direct connection or an indirect connection through an intermediate medium, or they can refer to the internal connection of two elements or the interaction between two elements. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0054] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not intended to limit it. Furthermore, it should be noted that, for ease of description, the accompanying drawings show only the parts relevant to the present invention, and not all of the structures.

[0055] Please refer to Figure 1 , Figure 1 This application provides a laser beam shaping system in one embodiment. The laser beam shaping system provided in this embodiment includes a laser source 1 and an aspherical lens group 2.

[0056] Laser source 1, located at the front focal point of aspherical lens group 2, is used to generate the initial beam. Specifically, the laser source can be a vertical cavity surface emitting laser (VCSEL), etc.

[0057] The aspherical lens group 2, positioned along the propagation path of the laser beam, includes: a first lens 21, a second lens 22, a third lens 23, and a fourth lens 24 arranged sequentially from the object side to the image side along the incident direction of the light source; wherein, the first lens 21 and the second lens 22 are plano-concave aspherical lenses, the third lens 23 is a biconcave aspherical lens, and the fourth lens 24 is a biconvex aspherical lens. The overall optical path focal length distribution presents a four-segment design of negative, negative, negative, and positive.

[0058] The optical focal length characterizes the refractive power of an optical system for an incident parallel beam of light. When the refractive index of the medium in object space and image space is 1, the optical focal length is the reciprocal of the lens focal length or the focal length of a lens group.

[0059] The first lens 21 with a negative focal length diverges the initial incident beam and simultaneously adjusts the energy distribution to reduce the energy density in the central region. The second lens 22 with a negative focal length further optimizes the energy distribution based on the first lens 21, giving the beam initial flat-top light characteristics. The third lens 23 with a negative focal length expands the beam with its larger negative focal length, giving the outgoing beam a larger divergence angle while finely adjusting the uniformity of the flat-top beam. Finally, the fourth lens 24 with a positive focal length collimates the beam, optimizes the flat-top light distribution characteristics, and works with the first three aspherical lenses to output a target flat-top beam with a long working distance.

[0060] From the perspective of aberration correction logic, the first three negative focal length aspherical lenses mainly serve to diverge the beam and initially correct spherical aberration, while the fourth positive focal length lens 24 is responsible for converging the beam, compensating for the aberrations of the front lens group, and optimizing the wavefront. Ultimately, the initial beam is collimated by the lens group to form the target flat-top beam, and the beam aperture achieves a beam expansion ratio of 9 times.

[0061] In the above embodiment, the first three negative focal length aspherical lenses are mainly responsible for diverging the beam and initially correcting spherical and coma aberrations, while the fourth positive focal length lens 24 is responsible for converging the beam, compensating for aberrations of the previous lens group, and optimizing the wavefront. After the initial beam is collimated by the lens group, it forms the target flat-top beam, while the beam aperture is expanded by a preset magnification.

[0062] Aspherical lens shaping systems have advantages such as simple structure, high shaping efficiency, high damage threshold, and ease of implementation. Since one surface of each lens in a dual-lens aspherical lens system is a plane, the dual-lens aspherical lens can be simplified into a single lens. The front and back surfaces of this single lens are both aspherical, which can replace the two lenses in the dual-lens system to achieve beam homogenization and collimation.

[0063] For ease of understanding, in the embodiments mentioned in this application, the surfaces of each lens are defined along the incident light direction. The front surface of the first lens 21 near the beam input is denoted as the first surface 301, and the rear surface near the beam output is denoted as the second surface 302. The front surface of the second lens 22 is denoted as the third surface 303, and the rear surface is denoted as the fourth surface 304. The front surface of the third lens 23 is denoted as the fifth surface 305, and the rear surface is denoted as the sixth surface 306. The front surface of the fourth lens 24 is denoted as the seventh surface 307, and the rear surface is denoted as the eighth surface 308.

[0064] Specifically, such as Figure 1As shown, the first lens 21 and the second lens 22 are both plano-concave aspherical lenses, wherein the first surface 301 and the third surface 303 near the beam incident side are both planar, and the second surface 302 and the fourth surface 304 facing the beam exit side are both designed aspherical; the third lens 23 is a biconcave aspherical lens, which adopts a combination structure of spherical and aspherical surfaces, wherein the fifth surface 305 on the incident side is spherical, and the sixth surface 306 on the exit side is aspherical; the fourth lens 24 is a biconvex aspherical lens, which also adopts a combination design of spherical and aspherical surfaces, wherein the seventh surface 307 on the incident side is spherical, and the eighth surface 308 on the exit side is aspherical.

[0065] In some embodiments, the aspherical equations used for the second surface 302, the fourth surface 304, the sixth surface 306, and the eighth surface 308 are as follows:

[0066]

[0067] Where z is the sag of the optical axis, c is the reciprocal of the radius of curvature, k is the conic coefficient, and r is the radial coordinate of the coordinate axis, satisfying the following in the xy coordinate system: ; , , , , , , , These are the coefficients of higher-order terms, dimensionless. In this aspherical equation, lower-order terms... , , Used to correct low-order aberrations (such as defocus); in mid-to-high-order terms... , , , Used to correct primary and advanced spherical aberrations, thereby improving the outgoing wavefront. Used for fine-tuning of precision systems to eliminate monochromatic aberration.

[0068] For example, in this embodiment, the conic coefficient k is 0, and the coefficient of higher-order terms is... , , , , , , , The possible values ​​for are shown in Table 1:

[0069] Table 1

[0070]

[0071] In some embodiments, the aspherical lens group 2 of the laser beam shaping system exhibits a specific design in terms of structural parameters. Specifically, the aspherical radius of curvature of the fourth surface 304 is greater than that of the second surface 302, the spherical radius of curvature of the fifth surface 305 within the third lens 23 is negative, and the spherical radius of curvature of the seventh surface 307 within the fourth lens 24 is positive.

[0072] For example, the center thickness of the first lens 21 ranges from 2.5mm to 3.5mm, such as 2.5mm, 3mm, or 3.5mm.

[0073] For example, the center thickness of the second lens 22 ranges from 3.5mm to 4.5mm, such as 3.5mm, 4mm, or 4.5mm.

[0074] For example, the center thickness of the third lens 23 ranges from 2.5mm to 3.5mm, such as 2.5mm, 3mm, or 3.5mm.

[0075] For example, the center thickness of the fourth lens 24 ranges from 6.5mm to 7.5mm, such as 6.5mm, 6mm, 7mm, or 7.5mm.

[0076] In terms of material selection, the refractive index and Abbe number of the first lens 21 to the third lens 23 are consistent, while the refractive index and Abbe number of the fourth lens 24 are higher than the former three. Specifically, the first, second, and third lenses are made of calcium fluoride, and the fourth lens is made of fused silica. This ensures that the lens group can withstand the energy impact of high-power lasers and also has a certain achromatic capability, making the lens group insensitive to changes in the working wavelength. The specific structural parameters of the aspherical lens group 2 are shown in Table 2 (the sign of the radius of curvature indicates the direction of curvature of the surface; a positive value bends towards the object side, and a negative value bends towards the image side).

[0077] Table 2

[0078]

[0079] The laser beam shaping system provided in this application will be further described below with reference to specific optical performance verification.

[0080] When the initial beam has a wavelength of 1064nm, the first air gap D1 between the first lens 21 and the second lens 22, and the second air gap D2 between the second lens 22 and the third lens 23 are 4 to 5 times the third air gap D3 between the third lens 23 and the fourth lens 24. Specifically, the air gaps of each lens are shown in Table 3:

[0081] Table 3

[0082]

[0083] In the above embodiments, the overall size of the aspherical lens group 2 is no more than 100mm, which breaks through the limitations of small space application scenarios. It can be flexibly adapted to compact space working environments such as small laser processing equipment and portable optical instruments. While ensuring high shaping performance, it also takes into account the ease of installation and scene adaptability, providing an efficient and reliable optical solution for small space laser applications.

[0084] Please see Figures 2-7 , Figure 2 A schematic diagram of the optical path of the laser beam shaping system provided in the above embodiments is shown. Figure 3 This is the energy distribution diagram of the initial beam. Figures 4-7 The images show the energy distribution of the target flat-top beam shaped by the aspherical lens group at working distances of 50mm, 500mm, 1200mm, and 2000mm, respectively. Figure 3 As shown, the initial beam energy exhibits a Gaussian-like distribution, with energy concentrated in the central region and gradually decreasing towards the edge. The energy proportion is significant in the range of -1.2 mm to 1.2 mm at the Y position, while the energy at the edge approaches 0. Figures 4-7 In the middle, the target flat-top beam, after being shaped by the aspherical lens group, at a working distance of 50mm ( Figure 4 ), 500mm ( Figure 5 ), 1200mm ( Figure 6 At 2000mm (7), the energy distribution exhibits obvious flat-top characteristics. The energy distribution remains relatively uniform within the range of -10mm to 10mm at position X. The energy at the edge drops rapidly to near 0. The energy distribution in the flat-top area within a distance of 50mm-2000mm is consistent, thus avoiding the occurrence of manufacturing precision or material performance problems caused by concentrated light intensity in the central area.

[0085] To further enhance system adaptability, this laser beam shaping system may also include an adjustment base (not shown): the aspherical lens group is mounted in the adjustment base, which can precisely adjust the values ​​of D1, D2, and D3 for the initial beam of different wavelengths, ensuring that the optical coordination of each lens is optimal at the target wavelength, and avoiding increased aberrations and decreased beam quality caused by wavelength differences. The addition of the adjustment base allows the system to adapt to multi-wavelength laser applications without replacing the lens group, greatly improving the versatility and reusability of the equipment, and reducing the cost of using multi-band laser shaping.

[0086] In the above embodiments, the laser beam shaping system can effectively reduce aberrations and optimize the outgoing wavefront by rationally allocating the optical power of optical elements, the combination of positive and negative optical power, and aspherical design. Using an aspherical lens group including four aspherical lenses, the initial beam is diverged, expanded, collimated, and its energy distribution is adjusted, converting the Gaussian-distributed incident light into a uniform flat-top light, with stable performance within a 2000mm working distance.

[0087] In addition, the aspherical lens group uses a combination of calcium fluoride and fused silica materials, which has both high power handling capacity and achromatic performance, and is not sensitive to changes in operating wavelength.

[0088] Please note that the above embodiments are for illustrative purposes only and do not imply any limitation on the present invention.

[0089] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0090] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0091] The above embodiments merely illustrate several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A laser beam shaping system, characterized in that, include: A laser light source is used to generate the initial beam; An aspherical lens group, disposed along the propagation path of the laser beam, includes: a first lens, a second lens, a third lens, and a fourth lens arranged sequentially from the object side to the image side along the incident direction of the light source; wherein, The first lens and the second lens are plano-concave aspherical lenses, both with negative focal length; The third lens is a biconcave aspherical lens with a negative focal length; The fourth lens is a biconvex aspherical lens with a positive focal length; The initial beam is collimated by the lens group to form the target flat-top beam, while the beam aperture is expanded by a preset magnification.

2. The laser beam shaping system according to claim 1, characterized in that, The front surfaces of both the first lens and the second lens are planar, and the rear surfaces are aspherical. The front surfaces of the third lens and the fourth lens are both spherical, and the rear surfaces are both aspherical. The front surface is used to characterize the surface closest to the beam input; the rear surface is used to characterize the surface closest to the beam output.

3. The laser beam shaping system according to claim 2, characterized in that, The aspherical equation used in the aspherical lens group is: Where z is the sag of the optical axis, c is the reciprocal of the radius of curvature, k is the conic coefficient, and r is the radial coordinate of the coordinate axis, satisfying the following in the xy coordinate system: ; , , , , , , , These are coefficients of higher-order terms, and are dimensionless. The aspherical conic coefficient k in the aspherical lens group is 0.

4. The laser beam shaping system according to claim 3, characterized in that, The aspherical radius of curvature of the second lens is greater than that of the first lens; The radius of curvature of the spherical surface of the third lens is less than zero; The radius of curvature of the spherical surface of the fourth lens is greater than zero.

5. The laser beam shaping system according to claim 4, characterized in that, The center thickness of the first lens ranges from 2.5mm to 3.5mm. The center thickness of the second lens ranges from 3.5mm to 4.5mm. The center thickness of the third lens ranges from 2.5mm to 3.5mm. The center thickness of the fourth lens ranges from 6.5mm to 7.5mm.

6. The laser beam shaping system according to claim 4, characterized in that, The first air gap between the first lens and the second lens is D1, the second air gap between the second lens and the third lens is D2, and the third air gap between the third lens and the fourth lens is D3; The third air gap D3 satisfies 4D1 < D3 > 5D1; or The third air gap D3 satisfies 4D2 < D3 > 5D2.

7. The laser beam shaping system according to any one of claims 1-6, characterized in that, The first lens, the second lens, and the third lens have the same refractive index and Abbe number; The refractive index and Abbe number of the fourth lens are greater than those of the first lens.

8. The laser beam shaping system according to any one of claims 1-6, characterized in that, The first lens, the second lens, and the third lens are made of calcium fluoride. The fourth lens is made of fused silica.

9. The laser beam shaping system according to any one of claims 1-6, characterized in that, The working distance of the aspherical lens group is 50mm-2000mm.

10. The laser beam shaping system according to any one of claims 1-6, characterized in that, The laser source is used to generate initial beams of multiple wavelengths; The laser beam shaping system further includes: An adjustment base is provided, in which the aspherical lens group is installed. The adjustment base is used to adjust the air gap between each lens in the aspherical lens group according to the wavelength of the initial beam.

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