Water jet guided high power laser beam shaping method, system and application device

Abstract

The application provides a water jet guided high-power laser beam shaping method, system and application device, which comprises a laser, a beam expander and a focusing unit arranged in sequence, a beam shaping unit arranged between the beam expander and the focusing unit, and the beam shaping unit shapes the laser energy from Gaussian distribution into flat-top light distribution with uniform energy and long focal depth. The multi-focus light path energy focused after the beam shaping unit is uniform, the energy density of a single focus is reduced, optical breakdown is not caused in the coupling and transmission process of the water beam fiber due to the high energy density, and the total energy of the water beam coupled laser can be improved. The water jet guided high-power laser beam shaping method, system and application device can apply high-power density laser to water guided laser processing technology, improve the uniformity degree of the radial and / or axial light beam, effectively ensure the coupling efficiency and system robustness, and improve the processing quality and processing efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water-guided laser processing, and particularly relates to a water jet guided high-power laser beam shaping method, system and application device. BACKGROUND

[0002] Water-guided laser processing is an advanced processing technology for processing materials by guiding a laser beam with a micro water jet beam. The principle is to generate a micron water beam fiber by using a coupling cavity, the laser is coupled with the water beam, and the laser is constrained in the water beam fiber by total reflection at the interface between water and air. The water beam fiber guides the laser to act on the workpiece surface to achieve processing. The high-energy laser beam can ablate the material, and the water jet can flush the workpiece surface to remove slag and cool the workpiece. Water-guided laser processing has the advantages of high speed, high precision and small thermal stress.

[0003] The shortest pulse width of the laser used in the existing water-guided laser processing is in nanosecond level. However, as the market requires higher and higher processing precision and processing efficiency, there is a demand for improving the efficiency and quality of water-guided laser processing. High-power lasers such as Q sub-nanosecond high-power density laser, Q narrow pulse width laser, mopa narrow pulse width laser and picosecond laser (wavelength 1064nm, 532nm, 355nm and 266nm, pulse width 300ps-20ns, power density up to 10 8 -10 12 W / cm 2 ) have the advantages of high power density, short light pulse width and large breakdown threshold. High power density can improve the processing rate; short pulse width means short interaction time of each pulse with the workpiece, which has small thermal influence on the surrounding area and can improve the processing precision; large breakdown threshold is less likely to cause optical breakdown, which can reduce nonlinear effects and improve processing quality. If high-power density laser can be coupled into the water beam fiber to remove materials mainly by gasification or plasma, it can achieve good processing quality and ensure high processing efficiency, which is conducive to promoting the application of water-guided laser processing technology in the field of high-precision processing.

[0004] The existing water-guided laser processing system usually includes a collimating and expanding system, a focusing lens, a coupling unit and a nozzle. The energy distribution of the laser beam is in Gaussian distribution during transmission. The laser beam in Gaussian distribution has low uniformity on the cross section of the water beam fiber, which easily leads to low workpiece processing quality and non-parallel kerf. After the laser beam is focused by the focusing lens, there is only one focal point. The single focal point laser beam is coupled with the water beam through the coupling cavity and the nozzle, and the energy concentration density is high, which easily causes optical breakdown and produces nonlinear effects, resulting in a large loss of laser energy. High-power laser has large energy, and once optical breakdown occurs, strong nonlinear effects will be produced, which seriously affects the processing quality. Therefore, the existing water-guided laser processing system cannot be applied to high-power laser, and high-power laser cannot achieve good processing effect by using the existing optical focusing system.

[0005] Based on the above shortcomings, if high-power laser can be applied to water guide laser processing system, and the problems of low beam homogenization degree and high single focus energy density can be overcome, the coupling adjustment efficiency, coupling beam energy homogenization and water guide system robustness can be effectively improved, and the processing quality, processing efficiency and processing precision of water guide laser technology are improved, and the promotion and industrialization application of water guide laser processing technology in high-precision and high-efficiency processing field are promoted. SUMMARY

[0006] The beam shaping method, system and application device of water jet guide high-power laser provided by the application can apply high-power density laser to water guide laser processing technology, optimize the energy distribution of the beam, improve the homogenization degree of the beam in the radial and axial directions, and effectively ensure the processing quality, processing efficiency and processing precision.

[0007] To achieve the above technical purposes and effects, the application solves the above problems through the following technical solutions:

[0008] The beam shaping system of water jet guide high-power laser comprises a laser, a beam expander group and a focusing unit arranged in sequence, a beam shaping unit is arranged between the beam expander group and the focusing unit, and the beam shaping unit shapes the laser energy from Gaussian distribution into flat-top light distribution with uniform energy and long focal depth.

[0009] In the above scheme, the laser beam enters the beam shaping unit through the beam expander group, and the beam shaping unit and the focusing unit adjust the laser beam to shape the laser energy from Gaussian distribution into flat-top light distribution with better radial uniformity or axial uniformity and longer focal depth. The energy intensity of the shaped beam is more uniform in the radial and / or axial directions, which can be more effectively and stably coupled into the water beam fiber.

[0010] The energy of the shaped beam is more uniform in the radial and / or axial directions, which can reduce the peak value of single-point energy, reduce the occurrence of optical breakdown, and improve the tolerance of the device to high-power density laser. The high-power density laser has high energy and short pulse width, which can effectively improve the processing rate, reduce the thermal influence on the surrounding area, and improve the processing precision.

[0011] Further, the beam shaping unit adopts a Galilean aspheric lens group, a laser diffraction beam splitter or a πshaper / pishaper beam shaping mirror group.

[0012] Further, the Galilean aspheric lens group comprises a Galilean aspheric plano-concave mirror and a Galilean aspheric plano-convex mirror arranged in front and back.

[0013] Further, the pishaper / pishaper beam shaping mirror group comprises two optical components arranged in front and back, the first optical component introduces spherical aberration required for energy redistribution, and the second optical component compensates for aberration.

[0014] Further, the focusing unit adopts a long-focus lens, a spherical lens, a logarithmic axicon, a multi-curvature surface combined refractive lens, a refractive-diffractive lens, or a refractive / diffractive lens group. The radius of curvature of the front and back surfaces of the long-focus lens is obtained by a nonlinear curve fitting method with the phase distribution function of the logarithmic axicon as the objective function.

[0015] Further, a meniscus lens group is arranged between the beam expander lens group and the beam shaping unit, and the meniscus lens group comprises a negative focal power meniscus convex lens and a positive focal power meniscus concave lens arranged in front and back.

[0016] Further, the beam expander lens group comprises a beam expander and a collimator arranged in sequence.

[0017] Further, the laser adopts a Q-switched sub-nanosecond high-power density laser, a Q-switched narrow pulse width laser, a mopa narrow pulse width laser, a picosecond or femtosecond laser generator, and the output power density reaches 10 8 -10 12 W / cm 2 order of magnitude.

[0018] The water jet guided high-power laser beam shaping method adopts the water jet guided high-power laser beam shaping system, and comprises the following steps:

[0019] 1) The laser is expanded and collimated by the beam expander lens group, and then enters the beam shaping unit to convert the laser from a divergent Gaussian laser beam to a collimated flat-top laser beam, and the laser energy is shaped from a Gaussian distribution to a uniform flat-top distribution;

[0020] 2) The collimated flat-top laser beam enters the focusing unit to focus to form a multi-focal point light path with high uniformity in radial and / or axial directions and long focal depth;

[0021] 3) The multi-focal point light path output is coupled with the water jet fiber to ablate the workpiece surface, and the water jet flushes the workpiece surface to carry away slag and cool the workpiece.

[0022] The processing device using the water jet guided high-power laser beam shaping system comprises a laser, a beam expander lens group, a beam shaping unit, a focusing unit, and a laser coupling device arranged in sequence; the beam shaping unit shapes the laser energy from a Gaussian distribution to a flat-top distribution with high uniformity and long focal depth; and the laser coupling device is configured to input high-pressure water flow by a high-pressure liquid supply system.

[0023] The output end of the laser coupling device is provided with a workbench unit, which comprises a support platform and a water tank installed on the support platform and used for placing a workpiece; the water inlet end of the high-pressure liquid supply system is connected to the water tank, and the water outlet end is connected to the laser coupling device to provide stable stepless pressure-adjusted high-pressure water flow.

[0024] The advantages and effects of the present application are:

[0025] 1. The water jet guided high-power laser beam shaping method and system, which adopts Q-switched sub-nanosecond high-power density laser, Q-switched narrow pulse width laser, mopa narrow pulse width laser or picosecond laser, etc. High-power density laser has the advantages of high power density, short optical pulse width and large breakdown threshold. The application of high-power density laser in water guided laser processing, combined with the advantages of water guided laser processing, can effectively improve the processing efficiency and processing precision.

[0026] 2. The water jet guided high-power laser beam shaping method and system, which sets the beam shaping unit and the focusing unit to adjust the optical path, so that the laser energy is shaped from Gaussian distribution to a flat-top beam with more uniform radial and / or axial distribution and longer focal depth, which is coupled with the water beam fiber, and the energy is distributed in multiple focal points to reduce optical breakdown. This scheme optimizes and uniformizes the energy distribution of the laser on the cross section of the water beam fiber, improves the tolerance of the water guided laser system to high-power laser, and makes the high-power laser better applied to water guided laser processing technology. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 It is a schematic diagram of the beam shaping system of embodiment 1 of the present application.

[0028] Figure 2 It is a schematic diagram of the beam shaping system of embodiment 2 of the present application.

[0029] Figure 3 It is a schematic diagram of the beam shaping system of embodiment 3 of the present application.

[0030] Figure 4 (a) is a dot array diagram of focal point light path f1.

[0031] Figure 4 (b) is a dot array diagram of focal point light path f2.

[0032] Figure 5 It is a schematic diagram of the processing device principle of the water jet guided high-power laser beam shaping system.

[0033] Figure number identification: 1, laser, 2, beam expander group, 21, beam expander, 22, collimator, 3, focusing unit, 31, long focal depth lens, 32, spherical lens, 33, logarithmic axicon mirror, 34, multi-curvature surface combined refractive lens, 35, refractive-diffractive lens, 36, refractive / diffractive lens group;

[0034] 4, beam shaping unit, 41, Galileo aspheric lens group, 411, Galileo aspheric plano-convex mirror, 412, Galileo aspheric plano-concave mirror, 42, laser diffraction beam splitter, 43, π shaper / pishaper beam shaping mirror group; 5, meniscus lens group, 51, negative meniscus concave lens, 52, positive meniscus convex lens,

[0035] 6, laser coupling device, 61, nozzle; 7, high-pressure liquid supply system, 71, water tank, 72, high-pressure water suction pump, 73, one-way valve, 74, energy accumulator, 75, overflow valve, 76, high-precision filter; 8, workbench unit, 81, support platform, 82, water tank. DETAILED DESCRIPTION

[0036] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. The specific embodiments described herein are only used to explain the present application and not to limit the present application.

[0037] Embodiment 1

[0038] The water jet guided high-power laser beam shaping system, as shown in the accompanying drawings, includes laser 1, beam expander group 2, meniscus lens group 5 (which can be selected according to needs), beam shaping unit 4, and focusing unit 3 arranged in sequence. Figure 1

[0039] The laser 1 is selected from a Q-switched sub-nanosecond high-power density laser, a Q-switched narrow pulse width laser, a mopa narrow pulse width laser, or a picosecond laser, etc. The power density of the high-power density laser generator is up to 10 8 -10 12 W / cm 2 order of magnitude. The beam expander group 2 includes beam expander 21 and collimator 22 arranged in sequence. The beam expander 21 expands the beam waist radius and reduces the divergence angle. The collimator changes the divergent light after beam expansion into parallel plane wavefront light with the same diameter. The laser light passing through the beam expander group 2 enters the meniscus lens group 7 as parallel light.

[0040] The meniscus lens group 5 includes negative meniscus concave lens 51 and positive meniscus convex lens 52 arranged in sequence. The meniscus lens group 5 is used to focus the laser beam precisely into the beam shaping unit 4.

[0041] ​The light beam shaping unit 4 selects a Galileo aspheric lens group 41, which includes a Galileo aspheric plano-convex lens 411 and a Galileo aspheric plano-concave lens 412 arranged in sequence. The Galileo aspheric plano-convex lens 411 divides and homogenizes the collimated light beam, and the Galileo aspheric plano-concave lens 412 adjusts the phase to make the light parallel output to the focusing unit 3.

[0042] The focusing unit 3 can select one of a long focal depth lens 31, a spherical lens 32, a logarithmic axicon lens 33, a multi-curvature combined refractive lens 34, a refractive-diffractive lens 35, and a refractive / diffractive lens group 36. When the long focal depth lens 31 is selected, the lens center thickness t is specified as 12.5 mm, the lens front curvature radius s1 is specified as 351.7 mm, the lens rear curvature radius s2 is specified as -645.5 mm, and the focal length f is specified as 450 mm. The focusing unit 3 can focus the uniform light beam output by the Galileo aspheric lens group 51 into a light beam with more uniform radial and / or axial distribution and longer focal depth, which enters the laser coupling device 4 in the form of a focal point array and is coupled with the water beam fiber.

[0043] When the focusing unit 3 adopts the long focal depth lens 31, the spherical lens 32, or the logarithmic axicon lens 33, the focal point array f1 of the outgoing light beam is as shown in Figure 4 (a). When the focusing unit 3 adopts the multi-curvature combined refractive lens 34, the refractive-diffractive lens 35, or the refractive / diffractive lens group 36, the focal point array f2 of the outgoing light beam is as shown in Figure 4 (b).

[0044] The multi-focal light path after the focusing of the light beam shaping unit 4 is uniform in energy, and the coupling and transmission process with the water beam fiber will not cause optical breakdown due to excessively high energy density.

[0045] Embodiment 2

[0046] As shown in the accompanying Figure 2 The difference between this embodiment and embodiment 1 is that the light beam shaping unit 4 selects a laser diffraction beam splitter 42, and the focusing unit 3 selects a long focal depth lens 31, a spherical lens 32, a logarithmic axicon lens 33, a multi-curvature combined refractive lens 34, a refractive-diffractive lens 35, or a refractive / diffractive lens group 36. The laser diffraction beam splitter 52 can also divide a single laser beam into multiple beams, and the multiple laser beams output by the focusing unit 3 are focused into a multi-focal light path, which is output in the form of a focal point array and coupled with the water beam fiber.

[0047] Embodiment 3

[0048] As shown in the accompanying Figure 3As shown, the difference between the embodiment and embodiment 1 is that the beam shaping unit 4 selects a pi shaper / pishaper beam shaping lens group 43, and the focusing unit 3 selects a long-focus lens 31, a spherical lens 32, or a logarithmic-axicon lens 33, a multi-curvature surface combined refractive lens 34, a refractive / diffractive lens 35, or a refractive / diffractive lens group 36. The pi shaper / pishaper beam shaping lens group 43 adjusts a single laser beam into multiple beams, and the multiple laser beams are output to the focusing unit 3 to be focused into a multi-focal light path in the form of a focal point array, and then coupled with the water jet fiber.

[0049] The embodiment of the present application also provides a water jet guided high-power laser beam shaping method, which adopts the water jet guided high-power laser beam shaping system in any one of the above embodiments, and the specific steps are as follows:

[0050] 1) The laser is expanded and collimated by the beam expander 2, and then enters the beam shaping unit 5 to convert the laser from a divergent Gaussian laser beam into a collimated flat-top laser beam, and the laser energy is shaped from a Gaussian distribution into a uniform flat-top distribution;

[0051] 2) The collimated flat-top laser beam enters the focusing unit 3 to be focused into a multi-focal light path with high uniformity in the radial and / or axial directions and long focal depth;

[0052] 3) The multi-focal light path is output and coupled with the water jet fiber to perform ablation processing on the workpiece surface, the water jet flushes the workpiece surface to carry away the slag and cool the workpiece.

[0053] The embodiment of the present application also provides a processing device using the water jet guided high-power laser beam shaping system, which comprises the beam shaping system in any one of the above embodiments, as shown in the accompanying drawings. Figure 5 As shown, the focusing unit 3 outputs the laser to the laser coupling device 6, and the laser coupling device 6 is configured to input high-pressure water flow from the high-pressure liquid supply system 7. The output end of the laser coupling device 6 is provided with the workbench unit 8 to fix the workpiece 9.

[0054] The workbench unit 8 comprises a support platform 81 and a water tank 82, the support platform 81 is installed at the corresponding working position of the output end of the laser coupling device 6, and the water tank 82 is installed on the support platform 81 to recover waste water. The workpiece 9 is installed in the water tank 82 to receive processing. The water inlet end of the stable high-pressure liquid supply system 7 is connected to the water tank 82, and the water outlet end is connected to the coupling cavity of the laser coupling device 6 to provide stable stepless pressure water flow.

[0055] The high-pressure liquid supply system 7 comprises a main liquid supply circuit composed of a water tank 71, a high-pressure water suction pump 72, a one-way valve 73, and an accumulator 74 connected in sequence, and the outlet pipeline of the main liquid supply circuit is connected to the laser coupling device 6 to output stable high-pressure water flow, and the inlet pipeline is connected to the water tank 82 to return the cooling water; an overflow valve 75 is arranged between the outlet of the high-pressure water suction pump 73 and the water tank 71 to form a pressure regulating circuit, so that the main liquid supply circuit remains stable and is prevented from being overloaded. The outlet pipeline and the inlet pipeline are both provided with high-precision filters 66 to filter the fluid.

[0056] The machining device is applied, and specifically includes the following steps:

[0057] 1) : The workpiece 9 is clamped in the corresponding working position at the output end of the laser coupling device 6;

[0058] 2) : The high-pressure liquid supply system 7 is started to deliver high-pressure water to the laser coupling device 6, and the laser coupling device 6 converts the high-pressure water into a stable water beam output;

[0059] 3) : After the water beam is stabilized, the laser 1 is turned on to output high-power density laser;

[0060] 4) : After the laser beam is collimated by the beam expander group 2 and focused by the meniscus lens group 5, the parallel light enters the beam shaping unit 4;

[0061] 5) : The laser beam is shaped by the beam shaping unit 4, and the laser energy is shaped from Gaussian distribution to flat-top beam with uniform energy distribution, and the shaped beam enters the focusing unit 3;

[0062] 6) : The laser beam is focused by the focusing unit 3 to form a beam with uniform radial and / or axial distribution and long focal depth, and the beam enters the laser coupling device 6 and is coupled into the water beam optical fiber;

[0063] 7) : The uniformized beam is guided and transmitted by the water beam optical fiber to the surface of the workpiece 9 for ablation machining.

Claims

1. A water jet guided high power laser beam shaping system, comprising a laser (1), a beam expander lens group (2) and a focusing unit (3) arranged in sequence, characterized in that: a beam shaping unit (4) is arranged between the beam expander lens group (2) and the focusing unit (3), the beam shaping unit (4) shapes the laser energy from Gaussian distribution to flat-top distribution with uniform energy and long focal depth; the beam shaping unit (4) adopts a laser diffraction beam splitter (42) or a πshaper / pishaper beam shaping lens group (43); the πshaper / pishaper beam shaping lens group (43) comprises two optical assemblies arranged in front and back, the first optical assembly introduces spherical aberration required for energy redistribution, and the second optical assembly compensates for aberration; the focusing unit (3) adopts a long focal depth lens (31); a meniscus lens group (5) is arranged between the beam expander lens group (2) and the beam shaping unit (4), the meniscus lens group (5) comprises a negative focal power meniscus convex lens (51) and a positive focal power meniscus concave lens (52) arranged in front and back; the system comprises the following devices: the focusing unit (3) outputs laser to a laser coupling device (6), the laser coupling device (6) is configured with a high-pressure liquid supply system (7) to input high-pressure water flow, and an output end of the laser coupling device (6) is provided with a workbench unit (8) to fix a workpiece (9); the workbench unit (8) comprises a support platform (81) and a water tank (82) installed on the support platform (81) to place the workpiece (9); a water inlet end of the high-pressure liquid supply system (7) is connected to the water tank (82), and a water outlet end is connected to the laser coupling device (6) to provide stable stepless pressure-adjustable high-pressure water flow; the system comprises the following steps: 1) laser is expanded and collimated by the beam expander lens group (2), and then enters the beam shaping unit (4) to convert the laser from divergent Gaussian laser beam to collimated flat-top laser beam, and the laser energy is shaped from Gaussian distribution to uniform flat-top distribution; 2) the collimated flat-top laser beam enters the focusing unit (3) to focus to form a multi-focal point light path with high uniformity in radial and / or axial direction and long focal depth; 3) the multi-focal point light path output is coupled with a water beam fiber to ablate the workpiece surface, and the water beam flushes the workpiece surface to carry away slag and cool the workpiece; the beam expander lens group (2) comprises a beam expander lens (21) and a collimating lens (22) arranged in sequence. ​ The laser (1) adopts Q-switched sub-nanosecond high-power density laser, Q-switched narrow pulse width laser, mopa narrow pulse width laser or picosecond laser generator, and the output power density reaches 10 8 -10 12 W / cm 2 order of magnitude; ​ ​ ​ ​ ​ ​ ​ ​ 2. The water jet guided high power laser beam shaping system according to claim 1, characterized in that: ​

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