Self-adjusting water-jet-guided laser light path focusing device and water-jet-guided laser light path method implemented by self-adjusting water-jet-guided laser light path focusing device

Abstract

The invention discloses a self-adjusting water-guided laser light path focusing device and a self-adjusting water-guided laser light path method implemented by the same, and aims to solve the technical problem of water and light coupling in water-guided laser due to the fact that the intensity and phase of a light beam at different positions are not accurately controlled at present. According to the self-adjusting water-guided laser light path focusing device, a second lens is arranged between a first lens and a third lens, the first lens and the second lens are conical lenses, the third lens is a focusing lens, a first curved surface is arranged close to an incident light source, a second curved surface and a third curved surface are oppositely arranged, and a fourth curved surface and a fifth curved surface are oppositely arranged; according to the self-adjusting water-guided laser light path method, optical simulation is carried out in ZEMAX, and the incident light diameter and the apodization factor of the system are correspondingly set according to requirements; and establishing a corresponding lens group initial model according to the initial parameters, determining the surface types of the first lens, the second lens and the third lens as standard surfaces, and configuring the curvature radiuses, the center thicknesses, the outer diameters and the refractive indexes of the first lens, the second lens and the third lens respectively.

Description

Technical Field

[0001] The present invention specifically relates to a self-adjusting water-guided laser optical path focusing device and a water-guided laser optical path method implemented thereby, belonging to the technical field of laser processing. Background Art

[0002] The core mechanism of water-guided laser technology is based on the total reflection characteristics of laser at the water-air interface. When a laser beam is incident on a water jet at a specific angle, the refractive index of water causes the laser to undergo total reflection and be confined to the interior of the water beam for transmission, similar to the principle of optical fiber light guiding. This design uses a high-pressure micro water beam as a "liquid optical fiber" to efficiently transfer laser energy to the processing area. At the same time, the water flow has both cooling and scouring effects during the processing, removing molten substances and reducing the heat-affected zone, achieving a processing effect with high precision and low heat damage. Compared with traditional lasers, the water-guided laser processing technology has the advantages of not requiring real-time focusing, no molten slag, small heat-affected zone, no microcracks, large depth-to-diameter ratio, and the ability to process thick plates.

[0003] However, in water-guided laser, due to the small diameter of the water beam fiber, such as the diameter of a hair, to achieve successful water-light coupling, it is necessary to ensure that the laser focusing spot is smaller than the diameter of the water beam fiber. Due to the diffraction theory of light, when a light beam passes through a lens with a finite size, diffraction occurs, which limits the further reduction of the spot size. The commonly used lens groups currently have various aberrations, such as spherical aberration, coma aberration, astigmatism, etc. These aberrations cause the light rays not to converge accurately at a single point after passing through the lens, resulting in the distortion of the spot shape and the increase of the spot size, making it difficult to couple the focusing spot with the water beam fiber. The focusing characteristics of the traditional lens group for a laser beam change significantly over a long distance. During coupling, it is highly sensitive to the distance and angle between the laser beam and the water beam, and it is difficult to find a suitable position for the laser beam to stably enter the water beam and propagate in it. The adjustment of the coupling system is difficult, and it is hard to achieve stable coupling. In the field of water-guided laser processing technology, a water-guided laser spot with a long depth of focus can maintain a relatively stable focusing state within a large depth range, enabling the laser energy to effectively act on a deeper position inside the material, thereby improving the processing accuracy and depth. Generally speaking, the depth of focus is inversely proportional to the spot size. To achieve a long depth of focus often leads to an increase in the spot size; while pursuing a small spot, the depth of focus becomes shallower. This is because in an optical system, the focusing characteristics are jointly determined by parameters such as the focal length and numerical aperture of the lens. To simultaneously meet the requirements of a small spot and a long depth of focus, fine optimization and balance of these parameters are needed, which is very challenging in actual design and manufacturing. Secondly, the optical focusing system used in traditional water-guided laser is fixed and cannot be adjusted to adapt to the coupling and transmission of different water beam diameters. The traditional focused light beam is often a Gaussian beam, and the phenomenon of intensity concentration easily causes damage to the laser crystal and optical components, and local thermal effects are likely to occur during focusing and coupling transmission. In contrast, by evenly distributing the intensity throughout the entire spot size, a flat-top beam can significantly increase the damage threshold of high-power lasers. Therefore, it is necessary to break through the optical technology of traditional focusing lenses, solve the technical problems of water-light coupling in water-guided laser, and improve the adjustability and stability of the system.

[0004] The laser beam emitted by a conventional laser follows a Gaussian distribution law in terms of its spatial intensity distribution, and is also known as a Gaussian beam. However, in many practical application scenarios of laser technology, such as laser drilling, grooving, laser material processing, optical information processing and storage recording, and clinical applications of lasers in the medical field, etc., it is expected that the laser light intensity can be evenly distributed. This is because the intensity of a Gaussian beam tends to be overly concentrated in the central region of the beam. Especially in high-power solid-state lasers and amplifiers, this intensity concentration phenomenon is likely to cause damage to laser crystals and optical components. In contrast, by evenly dispersing the intensity within the entire spot size, a flat-top beam can significantly increase the damage threshold of high-power lasers. Therefore, the uniformity of the laser beam not only concerns the overall performance of the laser, but also greatly affects the application effect and level of laser technology. To convert these non-uniformly distributed beams into uniformly distributed ones, it is necessary to precisely control the intensity and phase of the beam at different positions, which poses high requirements for the design and adjustment of the lens group. To achieve beam homogenization, multiple lenses are usually combined, and their arrangement and spacing are precisely designed to achieve multiple refractions and modulations of the beam, thereby achieving the purpose of homogenization. However, each lens in the lens group needs to have precise optical parameters, including focal length, refractive index, radius of curvature, etc. Minor parameter deviations may cause changes in the refraction and propagation path of light, thereby affecting the homogenization effect. For example, a minor error in the focal length may cause the focusing position of the beam to be inaccurate, resulting in uneven light intensity distribution. To sum up, it is difficult to balance the accuracy of the focusing position and the uniformity of the light intensity distribution, and there is currently no corresponding self-adjusting device and standardized solution method. Summary of the Invention

[0005] Based on the above difficult problems, the present invention provides a self-adjusting water-guided laser optical path focusing device and a water-guided laser optical path method implemented thereby.

[0006] A self-adjusting water-guided laser optical path focusing device includes a first lens, a second lens, and a third lens. The first lens, the second lens, and the third lens are arranged vertically in parallel, with the second lens disposed between the first lens and the third lens. The first lens and the second lens are both conical lenses, and the third lens is a focusing lens. The two side surfaces of the first lens are respectively a first curved surface and a second curved surface, the two side surfaces of the second lens are respectively a third curved surface and a fourth curved surface, and the two side surfaces of the third lens are respectively a fifth curved surface and a sixth curved surface. The first curved surface of the first lens is arranged close to the incident light source, the second curved surface and the third curved surface are arranged opposite to each other, and the fourth curved surface and the fifth curved surface are arranged opposite to each other.

[0007] As a preferred solution: the first-order term of the first curved surface is 0.176, the first-order term of the fourth curved surface is -0.176, and the radius of curvature of the fifth curved surface (3-1) is 319.4 mm.

[0008] As a preferred solution: the central thicknesses of the first lens, the second lens, and the third lens are 12.48 mm, 12.48 mm, and 14 mm in sequence.

[0009] As a preferred solution: the refractive indices of the first lens and the second lens are both 1.46, the refractive index of the third lens is 1.52, and the distance between the fourth surface and the fifth surface on the optical axis ranges from 10 to 30 mm.

[0010] As a preferred solution: the outer diameters of the first lens, the second lens, and the third lens are all 25.4 mm.

[0011] As a preferred solution: both the first lens and the second lens are plano-convex axicon lenses.

[0012] An automatic self-adjusting water-guided laser optical path method is realized by using the above-mentioned automatic self-adjusting water-guided laser optical path focusing device. The automatic self-adjusting water-guided laser optical path method is as follows:

[0013] Step 1: Conduct optical simulation in ZEMAX, and correspondingly set the incident light diameter and apodization factor of the system as required; set the laser wavelength to the wavelength corresponding to infrared light, green light, or ultraviolet light, establish the initial model of the corresponding lens group according to the initial parameters, determine the surface types of the first lens, the second lens, and the third lens as standard surfaces, and respectively configure the curvature radius, central thickness, outer diameter, and refractive index of the first lens, the second lens, and the third lens.

[0014] Step 2: After establishing the initial model of the lens group, correspondingly determine the degrees of freedom of the system, set the curvature radius of the third lens and the distance from the sixth surface of the third lens to the image plane as variables, and correspondingly adjust the distances between the first lens, the second lens, and the third lens to be 5 - 150 mm; when in the aspheric optimization adjustment process, set the surface types of the first lens and the second lens as aspheric surfaces, and set the aspheric coefficient k and each high-order coefficient as variables.

[0015] Step 3: Based on the optical shaping system composed of two axicon lenses, use the ray tracing method, select the REAY operand in the optimization operands of the ZEMAX software to optimize the exit position of any exit ray, form the corresponding beam shaping macro program according to the requirements of beam shaping, and use the beam shaping macro program to correspondingly obtain the aspheric surface type parameters of the lens group.

[0016] Step 4: According to the "least squares method" theory, after debugging and optimizing the first lens, the second lens, and the third lens multiple times, obtain the focused beam with a small spot, long focal depth, and uniformity corresponding to the requirements. When the focused spot is less than 20 um and the focal depth within 25 um is 500 um, it indicates that the uniformity of the focused spot is in a high-quality state.

[0017] As a preferred solution: The distance between the fourth surface of the second lens and the fifth surface of the third lens on the optical axis is d4. By controlling and adjusting the size of d4, the adjustment process of the focal length of the self-adjusting water-guided laser optical path focusing device is completed until the focal length of the self-adjusting water-guided laser optical path focusing device is adjusted to the corresponding requirements.

[0018] As a preferred solution: The adjustment range of d4 is 5 - 30 mm, and the value range of the focal length of the self-adjusting water-guided laser optical path focusing device is 702.59 - 706.89 mm.

[0019] As a preferred solution: The cone angle range of the first lens and the second lens is 0.5° - 30°.

[0020] Compared with the prior art, the present invention provides a self-adjusting water-guided laser optical path focusing device and a water-guided laser optical path method implemented thereby, having the following beneficial effects:

[0021] First: The self-adjusting water-guided laser optical path focusing device in the present invention forms a lens group with a simple structure and reasonable layout through the first lens, the second lens and the third lens. By adjusting the positional relationship of the first lens, the second lens and the third lens, a beam form meeting the corresponding requirements can be obtained. The formed beam focusing position is accurate and the light intensity distribution is uniform. This device can take into account both the accuracy of the focusing position and the uniformity of the light intensity distribution, enabling the Gaussian beam to have the characteristics of small spot focusing and uniformization at the same time, reducing the water-beam coupling difficulty in water-guided laser, and improving the laser power, processing efficiency and accuracy of the processing system.

[0022] Second: The self-adjusting water-guided laser optical path focusing method in the present invention can form a standardized quantization process. This method can achieve high-quality laser focusing, obtain small focusing spots and uniform spots, and to a certain extent achieve a long depth of focus, improving the water-beam coupling tolerance and the stability of the corresponding equipment; this method can also be adaptively adjusted to complete the adjustment of the precise focusing spot to adapt to water-guided lasers with different nozzle diameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 is a schematic structural diagram of the optical system in the embodiment of the present invention;

[0024] Figure 2 is a schematic diagram of the focal point distance from the focal point column of the self-adjusting water-guided laser optical path focusing device in the present invention;

[0025] Figure 3 is a schematic diagram of the focal point distance from the focal point column of a traditional single focusing mirror;

[0026] Figure 4 is a schematic diagram of the geometric image analysis of the self-adjusting water-guided laser optical path focusing device in the present invention;

[0027] Figure 5 Schematic diagram for geometric image analysis of a traditional single focusing lens;

[0028] Figure 6 Schematic diagram of the diffraction spot of the focused spot formed by the self - adjusting water - guiding laser light path focusing device in the present invention;

[0029] Figure 7 Schematic diagram of the diffraction spot of the focused spot of a traditional single focusing lens;

[0030] Figure 8 Schematic side view structure diagram of the first lens;

[0031] Figure 9 Schematic side view structure diagram of the second lens;

[0032] Figure 10 Schematic side view structure diagram of the third lens;

[0033] In the figure, 1 - the first lens; 1 - 1 - the first curved surface; 1 - 2 - the second curved surface; 2 - the second lens; 2 - 1 - the third curved surface; 2 - 2 - the fourth curved surface; 3 - the third lens; 3 - 1 - the fifth curved surface; 3 - 2 - the sixth curved surface. Specific embodiments

[0034] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0035] Specific embodiment 1: In combination with Figures 1 to 10 This embodiment is described. The self - adjusting water - guiding laser light path focusing device in this embodiment includes a first lens 1, a second lens 2, and a third lens 3. The first lens 1, the second lens 2, and the third lens 3 are arranged vertically and side by side. The second lens 2 is arranged between the first lens 1 and the third lens 3. The first lens 1 and the second lens 2 are both conical lenses, and the third lens 3 is a focusing lens. The two side surfaces of the first lens 1 are respectively the first curved surface 1 - 1 and the second curved surface 1 - 2. The two side surfaces of the second lens 2 are respectively the third curved surface 2 - 1 and the fourth curved surface 2 - 2. The two side surfaces of the third lens 3 are respectively the fifth curved surface 3 - 1 and the sixth curved surface 3 - 2. The first curved surface 1 - 1 of the first lens 1 is arranged close to the incident light source. The incident light source is an existing laser light source, and its working principle is the same as that of the existing laser light source. The second curved surface 1 - 2 and the third curved surface 2 - 1 are arranged opposite to each other. The fourth curved surface 2 - 2 and the fifth curved surface 3 - 1 are arranged opposite to each other.

[0036] In this embodiment, the tolerance ranges of the radius of curvature, central thickness, outer diameter, refractive index of each curved surface and each spacing are all 5%.

[0037] In the self - adjusting water - guiding laser optical path focusing device of the present invention, because it includes a collimating and beam - expanding mirror and a focusing mirror, it can also realize the process of the laser emitted by a common fiber laser after collimation / beam expansion, and complete the high - efficiency shaping and coupling adjustment process.

[0038] After the above - mentioned configuration of each lens of the beam - expanding system in the present invention, the device can focus the incident laser beam, re - match the phase of the beam through an axicon, and utilize spherical aberration to improve the focusing effect of the beam to a certain extent, effectively improving the uniformity of the beam, which is beneficial to improving the efficiency and accuracy of laser processing. The laser wavelength includes infrared light and is not limited to infrared light.

[0039] Specific Embodiment 2: This embodiment is a further limitation of Specific Embodiment 1. In this embodiment, the first - order term of the first curved surface 1 - 1 is 0.176, the first - order term of the fourth curved surface 2 - 2 is - 0.176, and the radius of curvature of the fifth curved surface 3 - 1 is 319.4 mm.

[0040] Specific Embodiment 3: This embodiment is a further limitation of Specific Embodiment 1 or 2. In this embodiment, the central thicknesses of the first lens 1, the second lens 2 and the third lens 3 are 12.48 mm, 12.48 mm and 14 mm in sequence.

[0041] Specific Embodiment 4: This embodiment is a further limitation of Specific Embodiment 1, 2 or 3. The refractive indices of the first lens 1 and the second lens 2 are both 1.46, the refractive index of the third lens 3 is 1.52, and the value range of the spacing between the fourth curved surface 2 - 2 and the fifth curved surface 3 - 1 on the optical axis is 10 - 30 mm.

[0042] Specific Embodiment 5: This embodiment is a further limitation of Specific Embodiment 1, 2, 3 or 4. The outer diameters of the first lens 1, the second lens 2 and the third lens 3 are all 25.4 mm.

[0043] Specific Embodiment 6: This embodiment is a further limitation of Specific Embodiment 1, 2, 3, 4 or 5. The first lens 1 and the second lens 2 are both plano - convex axicon lenses.

[0044] Combined with Figures 1 to 10 As shown, the present invention includes a first lens L1, a second lens L2 and a third lens L3 coaxially arranged along the transmission direction of the incident light. The first lens L1 and the second lens L2 are both axicons, and the third lens L3 is a plano - convex positive lens. Among them, combined with Figure 1As shown in the figure, the first lens L1 includes a first curved surface S1 and a second curved surface S2 arranged along the transmission direction of the incident light. They are arranged from left to right in the schematic diagram direction, that is, the first curved surface S1 and the second curved surface S2 serve as the light incident surface and the light exit surface respectively. Similarly, the second lens L2 includes a third curved surface S3 and a fourth curved surface S4, and the third lens L3 includes a fifth curved surface S5 and a sixth curved surface S6. The incident light is transmitted along the direction from the first curved surface S1 to the sixth curved surface S6, and finally the energy distribution is changed after passing through the entire focusing system. In this system, the first curved surface S1 of the first lens L1 is an axicon surface, and the first-order term is 0.176. In addition, the central thickness d1 of the first lens L1, that is, the thickness of the first lens L1 on the optical axis, is 12.48 mm, and the outer diameter D1 is 25.4 mm. The refractive index of the first lens L1 is 1.46. The above parameters are not the only choices, and there is a tolerance range of 5%, that is, each parameter is allowed to vary within 5%.

[0045] In this embodiment, the third curved surface S3 of the second lens L2 is a plane, and the fourth curved surface S4 is an axicon surface, and its first-order term is -0.176. The refractive index of the second lens L2 is 1.46, and the central thickness d3 of the second lens L2 is 12.48 mm, and the outer diameter D2 is 25.4 mm. The tolerance range of each parameter of the second lens L2 is still 5%. Among them, the negative sign indicates that the center of curvature of the curved surface is located in the object space of the curved surface, and the positive sign indicates that the center of curvature of the curved surface is located in the image space of the curved surface. Similarly, the fifth curved surface S5 of the third lens L3 is a convex surface with a curvature of 319.4, the sixth curved surface S6 is a plane, the refractive index of the third lens L3 is 1.52, the central thickness d5 is 14 mm, and the outer diameter D3 is 25.4 mm. The tolerance range of each parameter of the third lens L3 is also 5%.

[0046] The present invention limits the distance between the first lens L1 and the second lens L2, and the distance between the second lens L2 and the third lens L3. Specifically, the tolerance is 5%. The distance d4 on the optical axis between the exit surface of the second lens L2, that is, the fourth curved surface S4, and the incident surface of the third lens L3, that is, the fifth curved surface S5, is 20 - 30 mm, and the tolerance is 5%.

[0047] Table 1 below shows the lens structure parameters of the infrared laser focusing system, specifically:

[0048] Table 1

[0049] Surface serial number Surface type Radius of curvature Thickness Refractive index of material Diameter First-order term S1 Asphere Infinity 12.48 1.46 25.4 S2 Plane Infinity 25.4 0.176 S3 Plane Infinity 12.48 1.46 25.4 S4 Asphere Infinity 25.4 -0.176 S5 Sphere 319.4 14 1.52 25.4 S6 Plane Infinity 25.4

[0050] According to the data in the above table, after configuring each lens as described above, the focusing system can focus the incident collimated / beam-expanded laser, reshape the original Gaussian beam into a flat top or a more uniform energy distribution, thereby expanding the application range of the focusing system. Moreover, the parallelism of the output beam has a small spot size, good focusing effect, and high coupling efficiency, which is more conducive to coupling high-power lasers in the water-jet guided laser processing system, improving the processing accuracy and the efficiency of laser processing.

[0051] Combined with Figures 1 to 7 As shown, according to the off-focus diagram, it can be seen that the focused spot of the system of the present invention changes slowly under off-focus, while the spot of a single focusing lens changes rapidly, indicating that the focused spot of the present invention has a relatively longer depth of focus. According to the geometric analysis diagram, it can be seen that the uniformity of the focused spot of the optical focusing system of the present invention is better than that of a traditional single focusing lens.

[0052] The parameters of the surface curvature radius, refractive index, central thickness, and outer diameter of the above-mentioned first, second, and third lenses can be selected from the specific parameters provided above. That is: the first-order term of the first surface S1 of the first lens L1 is 0.176, the central thickness d1 is 12.48 mm, and the outer diameter D1 is 25.4 mm. The refractive index of the first lens L1 is 1.52. The same applies to the second lens L2 and the third lens L3. The distance between the focusing lens and the shaping lens is 30 mm. This preferred solution has a better shaping and focusing effect, especially suitable for shaping 1064 nm infrared light.

[0053] Furthermore, based on the above core or preferred solution, different effective focal length adjustments can be obtained by designing the distance d4 between the fourth surface S4 and the fifth surface S5 on the optical axis differently. The following provides several specific preferred solutions.

[0054] When the distance d4 between the fourth surface S4 and the fifth surface S5 on the optical axis is set to 30 mm, this parameter is a preferred parameter, and this distance also has a tolerance range of 5%. At this time, the effective focal length of the system is 702.59 mm.

[0055] When the distance d4 between the fourth surface S4 and the fifth surface S5 on the optical axis is set to 5 mm, this parameter is a preferred parameter, and this distance also has a tolerance range of 5%. At this time, the effective focal length of the system is 706.89 mm.

[0056] The laser shaping system provided by the present invention can achieve the shaping and focusing of Gaussian beams, can obtain small focused spots, significantly extend the depth of focus, reduce the difficulty of water-beam coupling; improve the uniformity of the focused beam, reduce the thermal effect, and improve the stability and flexibility of the water-jet guided laser processing system.

[0057] Specific Embodiment Seven: Combined with Figures 1 to 10To describe this embodiment, the self-adjusting water-guided laser optical path method in this embodiment is realized by using a self-adjusting water-guided laser optical path focusing device. The structure of the self-adjusting water-guided laser optical path focusing device includes a first lens 1, a second lens 2, and a third lens 3. The first lens 1, the second lens 2, and the third lens 3 are arranged vertically in parallel. The second lens 2 is arranged between the first lens 1 and the third lens 3. The first lens 1 and the second lens 2 are both plano-convex axicon lenses, and the third lens 3 is a focusing lens. The two side surfaces of the first lens 1 are respectively a first curved surface 1-1 and a second curved surface 1-2. The two side surfaces of the second lens 2 are respectively a third curved surface 2-1 and a fourth curved surface 2-2. The two side surfaces of the third lens 3 are respectively a fifth curved surface 3-1 and a sixth curved surface 3-2. The first curved surface 1-1 of the first lens 1 is arranged close to the incident light source. The second curved surface 1-2 and the third curved surface 2-1 are arranged opposite to each other. The fourth curved surface 2-2 and the fifth curved surface 3-1 are arranged opposite to each other.

[0058] Further, the first-order term of the first curved surface 1-1 is 0.176, the first-order term of the fourth curved surface 2-2 is -0.176, and the radius of curvature of the fifth curved surface 3-1 is 319.4 mm.

[0059] Further, the central thicknesses of the first lens 1, the second lens 2, and the third lens 3 are 12.48 mm, 12.48 mm, and 14 mm in sequence.

[0060] Further, the refractive indices of the first lens 1 and the second lens 2 are both 1.46, the refractive index of the third lens 3 is 1.52, and the distance between the fourth curved surface 2-2 and the fifth curved surface 3-1 on the optical axis ranges from 10 to 30 mm.

[0061] Further, the outer diameters of the first lens 1, the second lens 2, and the third lens 3 are all 25.4 mm.

[0062] The self-adjusting water-guided laser optical path method in this embodiment is as follows:

[0063] Step 1: Perform optical simulation in ZEMAX, and correspondingly set the incident light diameter and apodization factor of the system as required; set the laser wavelength to the wavelength corresponding to infrared light, green light, or ultraviolet light. Establish an initial model of the corresponding lens group according to the initial parameters. Determine the surface types of the first lens 1, the second lens 2, and the third lens 3 as standard surfaces, and respectively configure the radius of curvature, central thickness, outer diameter, and refractive index of the first lens 1, the second lens 2, and the third lens 3.

[0064] Step 2: After establishing the initial model of the lens group, determine the degrees of freedom of the system accordingly. Set the curvature radius of the third lens 3 and the distance from the sixth surface 3-2 of the third lens 3 to the image plane as variables, and adjust the distances between the first lens 1, the second lens 2, and the third lens 3 to be 5 - 150 mm correspondingly; when in the aspheric optimization adjustment process, set the surface profiles of the first lens 1 and the second lens 2 as aspheric surfaces, and set the aspheric coefficient k and each high-order coefficient as variables;

[0065] Step 3: Based on the optical shaping system composed of two pyramid lenses, use the ray tracing method to select the REAY operand in the optimization operands of ZEMAX software to optimize and obtain the exit position of any exit ray, form the corresponding beam shaping macro program according to the requirements of beam shaping, and use the beam shaping macro program to obtain the aspheric surface profile parameters of the lens group correspondingly.

[0066] Step 4: According to the "least squares method" theory, after debugging and optimizing the first lens 1, the second lens 2, and the third lens 3 multiple times, obtain a focused beam with a small spot, a long focal depth, and uniformity corresponding to the requirements. When the focused spot is less than 20 um and the focal depth within 25 um is 500 um, it indicates that the uniformity of the focused spot is in a high-quality state.

[0067] Among them, the distance between the fourth surface 2-2 of the second lens 2 and the fifth surface 3-1 of the third lens 3 on the optical axis is d4. By controlling and adjusting the size of d4, the adjustment process of the focal length of the self-adjusting water-guided laser optical path focusing device is completed correspondingly until the focal length of the self-adjusting water-guided laser optical path focusing device is adjusted to the corresponding requirements.

[0068] Furthermore, the adjustment range of d4 is 5 - 30 mm, and the focal length value range of the self-adjusting water-guided laser optical path focusing device is 702.59 - 706.89 mm.

[0069] Furthermore, the cone angle range of the first lens 1 and the second lens 2 is 0.5° - 30°

[0070] When the method in the present invention is specifically used, one usage process is as follows:

[0071] Step 1: Conduct relevant optical simulations in ZEMAX, and set the incident light diameter and apodization factor of the system. The laser wavelength can be set to 1064 nm (infrared), 532 nm (green light), 355 nm (ultraviolet light). Establish a reasonable initial model of the lens group according to the initial parameters, select the standard surface for the surface profile of each lens, and set the curvature radius, central thickness, outer diameter, and refractive index of each lens. In the embodiment of the present invention, the incident light diameter adopted is 10 mm, the apodization factor is 1, and the laser is set to 1064 nm infrared laser.

[0072] Step 2: After the initial model is established, determine the system degrees of freedom. Set the radius of curvature of the focusing lens and the distance from the rear surface of the lens to the image plane as variables, and control the distance between each lens to be 5 - 150 mm. When performing aspheric optimization design, set the surface profile of the pyramid prism as an aspheric surface. On this basis, set the aspheric coefficient k and each high-order coefficient as variables. The cone angle range of the axicon prism is 0.5° to 30°.

[0073] Step 3: When designing the optical shaping system based on two pyramid lenses, use the ray tracing method. Select the "REAY" operand in the optimization operands of the ZEMAX software to optimize the exit position of any exit ray. Write a corresponding beam shaping macro program according to the requirements of beam shaping. When optimizing, call this program to obtain the aspheric surface profile parameters of the lens group.

[0074] Step 4: According to the "least squares method" theory, after debugging and optimizing the lens group multiple times, a focused beam with a small spot, long focal depth, and uniformity is obtained. In the embodiment of the present invention, the focused spot obtained is less than 20 um, the focal depth within 25 um can reach 500 um, and the uniformity of the overall spot is better. The structures and connection relationships not mentioned in this embodiment are the same as those in the first, second, third, fourth, fifth, or sixth specific embodiments.

Claims

1. An adjustable water-guided laser optical path focusing device, characterized in that: It includes a first lens (1), a second lens (2) and a third lens (3). The first lens (1), the second lens (2) and the third lens (3) are arranged vertically and side by side. The second lens (2) is arranged between the first lens (1) and the third lens (3). The first lens (1) and the second lens (2) are both conical lenses, and the third lens (3) is a focusing lens. The two side surfaces of the first lens (1) are a first curved surface (1-1) and a second curved surface (1-2) respectively. The two side surfaces of the second lens (2) are a third curved surface (2-1) and a fourth curved surface (2-2) respectively. The two side surfaces of the third lens (3) are a fifth curved surface (3-1) and a sixth curved surface (3-2) respectively. The first curved surface (1-1) of the first lens (1) is arranged close to the incident light source. The second curved surface (1-2) and the third curved surface (2-1) are arranged oppositely. The fourth curved surface (2-2) and the fifth curved surface (3-1) are arranged oppositely.

2. The self-adjusting water-guided laser optical path focusing device according to claim 1, wherein: The first-order term of the first curved surface (1-1) is 0.176, the first-order term of the fourth curved surface (2-2) is -0.176, and the radius of curvature of the fifth curved surface (3-1) is 319.4 mm.

3. The self-adjusting water-guided laser optical path focusing device according to claim 2, characterized in that: The central thicknesses of the first lens (1), the second lens (2) and the third lens (3) are 12.48 mm, 12.48 mm and 14 mm in sequence.

4. The self-adjusting water-guided laser optical path focusing device according to claim 3, wherein: The refractive indices of the first lens (1) and the second lens (2) are both 1.46, the refractive index of the third lens (3) is 1.52, and the distance between the fourth curved surface (2-2) and the fifth curved surface (3-1) on the optical axis ranges from 10 to 30 mm.

5. The self-adjusting water-guided laser light path focusing device according to claim 4, wherein: The outer diameters of the first lens (1), the second lens (2) and the third lens (3) are all 25.4 mm.

6. The self-adjusting water-guided laser optical path focusing device according to claim 1, 2, 3, 4 or 5, characterized in that: Both the first lens (1) and the second lens (2) are plano-convex axicon lenses.

7. A method for self-adjusting a water-guided laser optical path, which is implemented by using the self-adjusting water-guided laser optical path focusing device described in claims 1, 2, 3, 4, 5 or 6, characterized in that: The self-adjusting water-guided laser light path method is as follows: Step 1: Conduct optical simulation in ZEMAX, and correspondingly set the incident light diameter and apodization factor of the system as required; set the laser wavelength to the wavelength corresponding to infrared light, green light or ultraviolet light. Establish an initial model of the corresponding lens group according to the initial parameters. Determine the surface types of the first lens (1), the second lens (2) and the third lens (3) as standard surfaces, and respectively configure the radius of curvature, central thickness, outer diameter and refractive index of the first lens (1), the second lens (2) and the third lens (3). Step 2: After establishing the initial model of the lens group, correspondingly determine the degrees of freedom of the system. Set the radius of curvature of the third lens (3) and the distance from the sixth curved surface (3-2) of the third lens (3) to the image plane as variables, and correspondingly adjust the distances between the first lens (1), the second lens (2) and the third lens (3) to be 5 - 150 mm; when in the aspheric optimization adjustment process, set the surface types of the first lens (1) and the second lens (2) as aspheric surfaces, and set the aspheric coefficient k and each high-order coefficient as variables. Step 3: Based on the optical shaping system composed of two pyramid lenses, using the ray tracing method, select the REAY operand in the optimization operands of the ZEMAX software to optimize the exit position of any exit ray, form a corresponding beam shaping macro program according to the requirements of beam shaping, and use the beam shaping macro program to correspondingly obtain the aspheric surface type parameters of the lens group. Step 4: According to the "least squares method" theory, after debugging and optimizing the first lens (1), the second lens (2) and the third lens (3) multiple times, a focused beam with a small spot, a long focal depth and uniformity meeting the corresponding requirements is obtained. When the focused spot is less than 20um and the focal depth within 25um is 500um, it indicates that the uniformity of the focused spot is in a high-quality state.

8. The self-adjusting water-guided laser light path method according to claim 7, characterized in that: The distance between the fourth surface (2-2) of the second lens (2) and the fifth surface (3-1) of the third lens (3) on the optical axis is d4. By controlling and adjusting the size of d4, the adjustment process of the focal length of the self-adjusting water-guided laser optical path focusing device is completed correspondingly until the focal length of the self-adjusting water-guided laser optical path focusing device is adjusted to the corresponding requirements.

9. The self-adjusting water-guided laser light path method according to claim 8, wherein: The adjustment range of d4 is 5 - 30mm, and the focal length value range of the self-adjusting water-guided laser optical path focusing device is 702.59 - 706.89mm.

10. The self-adjusting water-guided laser optical path method according to claim 7, 8 or 9, characterized in that: The cone angle range of the first lens (1) and the second lens (2) is 0.5° - 30°.

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