Light path structure of three-dimensional dynamic focusing scanning system

Abstract

The invention provides a light path structure of a three-dimensional dynamic focusing scanning system for ultra-long-distance and ultra-large-range laser. By adjusting the distance between the first lens and the second lens along the optical axis and the deflection angle of the reflector, focusing scanning of the laser in the space of 1.5 m * 1.5 m * 0.4 m can be achieved, the maximum focal length of the system can exceed 2300 mm, the RMS radius of a focusing light spot is smaller than 27 micrometers, and good roundness is achieved. Through the combined design of various lenses, the divergence angle of light passing through each lens is reduced, and the stability of the system is greatly improved. The actual machining, assembling and control tolerance of each lens is fully considered, the RMS radius of a focusing light spot in a scanning space is smaller than 50 microns, the light spot consistency is good, laser focusing scanning in an ultra-long-distance and ultra-large-space range is achieved, and the method has high guiding significance in dynamic focusing scanning optical system design and optical element selection.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical system design, and particularly relates to an optical path structure of a three-dimensional dynamic focusing scanning system, which can be applied to laser three-dimensional advanced manufacturing fields such as laser etching and laser cleaning. Background Art

[0002] Lasers have advantages such as good monochromaticity, directionality, strong coherence, and high power density, and are suitable for advanced manufacturing scenarios that require high precision and high energy density. Laser scanning technology is a technology that controls the focusing of lasers at different positions in space to achieve industrial applications. It has the characteristics of high precision and high speed and is widely used in fields such as laser etching and laser cleaning. Dynamic focusing technology is currently the best solution for realizing three-dimensional large-format laser scanning. It perfectly combines the characteristics of high speed, large range, and multiple planes, greatly improving the efficiency and flexibility of laser scanning.

[0003] Currently, the optical path structures of three-dimensional dynamic focusing scanning systems are mainly divided into two types. The first is a combined structure of a dynamic focusing lens group and a two-axis galvanometer. The defocus error at different positions in three-dimensional space is compensated by moving the dynamic focusing lens, and the galvanometer controls the deflection angle of the laser in space. The second is the combination of a dynamic focusing module, a two-axis galvanometer module, and an F-Theta field lens. The F-Theta field lens is used to achieve two-dimensional scanning within the same height focusing plane, and the dynamic focusing module is used to control the focusing plane position of the field lens in the Z direction. The first optical path structure is relatively simple. However, during control, the inclination angle of the scanning laser beam and the adjustment of the focusing position affect each other, introducing large aberrations, and the system stability is insufficient. The processing, assembly, and control errors have a greater impact on the focusing effect of the system. The second structure enhances the system stability through the F-Theta field lens and is easier to control. However, the system optical path structure is relatively complex, and to achieve a large scanning range, it is necessary to expand the lens size of the F-Theta field lens to achieve the flat field effect, resulting in greater processing difficulty and higher processing costs.

[0004] In addition, the scanning ranges of current dynamic focusing systems are all limited, and the focal lengths of the optical paths are short, making it impossible to achieve dynamic focusing of laser scanning within a large space range. The patent document with the publication number CN114609778A reports a dynamic focusing scanning optical path structure used in conjunction with an infrared laser, and its maximum working range can only reach 160mm×160mm×20mm. The patent document with the publication number CN113319425A reports a multi-axis laser scanning optical system, and its scanning area diameter is only 50mm. Therefore, the existing technology cannot meet the processing requirements for three-dimensional large curved surfaces in laser advanced manufacturing fields such as laser etching and laser cleaning.

[0005] At present, the design of optical systems has been closely integrated with computer technology. With the continuous update and optimization of optical design software such as Zemax and CodeV, optical design has become more efficient and convenient, enabling the design of increasingly complex optical structures. The design of dynamic focusing scanning systems should develop in the direction of high precision, large scanning and processing ranges, easy processing and manufacturing, and easy control. Summary of the Invention

[0006] In view of the above problems in the prior art, the present invention combines the advantages of the current two dynamic focusing scanning system structures. The aim is to provide an optical path structure for a three-dimensional dynamic focusing scanning system for ultra-long distance and ultra-large range lasers. Its characteristics lie in the combined design of multiple lenses, which reduces the divergence angle of light passing through each lens and the system aberration, and greatly improves the stability of the system. The system can achieve the focusing and scanning of lasers in a space of 1.5m×1.5m×0.4m. The maximum focal length of the system can exceed 2300mm, the RMS radius of the focused spot is less than 27μm, and it has good roundness. Moreover, full consideration is given to the actual processing, assembly, and control tolerances of each lens, and the quality of the focused spot during scanning at different spatial positions of the simulated system is considered. The RMS radius of the focused spot is less than 50μm, and it has strong consistency.

[0007] According to one aspect of the present application, there is provided an optical path structure for a three-dimensional dynamic focusing scanning system, which is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens, and a mirror arranged in sequence along the optical axis;

[0008] The laser beam passes through the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens, and the mirror in sequence and then focuses on focal planes at different heights.

[0009] The first lens is a dynamic focusing lens that can move along the optical axis and is used to control the focusing diameter of the laser beam and the Z coordinate of the laser focus in a three-dimensional rectangular coordinate system. Dynamic focusing can be achieved by adjusting the distance between the first lens and the second lens along the optical axis. The distance between the first lens and the second lens varies within the range of 24.321mm to 98.631mm, and the positions of the remaining lenses are fixed.

[0010] The first lens is a meniscus positive lens, the second lens is a biconcave negative lens, the third, fourth, and fifth lenses are the same, all being meniscus negative lenses, and the sixth and seventh lenses are the same, all being meniscus positive lenses.

[0011] The front surface curvature radius of the first lens is 290 mm, and the rear surface curvature radius is 1312.2 mm; the central thickness of the first lens is 10 mm, and the distance between the first lens and the second lens is dynamically adjustable within the range of 24.321 mm to 98.631 mm.

[0012] The front surface curvature radius of the second lens is -501.2 mm, and the rear surface curvature radius is 325 mm;

[0013] The central thickness of the second lens is 10 mm, and the distance between the second lens and the third lens is 10 mm.

[0014] The third, fourth, and fifth lenses have the same structure, with a front surface curvature radius of -228.08 mm and a rear surface curvature radius of -228.08 mm; the central thickness of the third, fourth, and fifth lenses is 10 mm, and the distances between the third, fourth, fifth, and sixth lenses are all 10 mm.

[0015] The sixth and seventh lenses have the same structure, with a front surface curvature radius of 501.2 mm and a rear surface curvature radius of 1560 mm; the central thickness of the sixth and seventh lenses is 10 mm, and the distance between the sixth and seventh lenses is 10 mm.

[0016] The distance between the seventh lens and the mirror is 130 mm.

[0017] The mirror is a two-axis planar mirror for controlling the propagation direction of the laser in space. It can be deflected simultaneously around the X-axis and Y-axis in three-dimensional space to control the X and Y coordinates of the laser focus in the three-dimensional rectangular coordinate system. The maximum single-axis mechanical deflection angle is 45° ± 16.8°, and the distance from the Z-axis direction of the focusing plane is 1650 mm to 2050 mm.

[0018] The central thickness of the mirror is 20 mm.

[0019] All lens materials are fused silica glass with a refractive index of 1.4585.

[0020] The laser beam is a Gaussian beam with a wavelength of 1064 nm, a apodization factor of 1.5, and an entrance pupil diameter of 70 mm.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] In the prior art and related products, the dynamic focusing scanning range is limited. In the optical path of the present invention, by adjusting the distance between the first lens and the second lens along the optical axis and the deflection angle of the mirror, it is possible to achieve the focusing scanning of the laser within a space of 1.5 m × 1.5 m × 0.4 m, and the maximum system focal length can exceed 2300 mm.

[0023] Through the combined design of multiple lenses, the present invention significantly improves the stability of the system, reduces the aberration in the scanning space, the RMS radius of the focused spot is less than 27 μm, and it has good roundness. Moreover, fully considering the actual processing, assembly and control tolerances of each lens, the RMS radius of the focused spot in the scanning space is less than 50 μm, the spot consistency is good, and it can meet the application requirements for three-dimensional large-scale curved surface processing in fields such as laser etching and laser cleaning.

[0024] The dynamic focusing lens in the present invention can simultaneously adjust the size of the laser focused spot and the specific position of the laser focus in the Z direction. In occasions with higher processing accuracy requirements, an expander with a large magnification can be selected to expand the diameter of the laser beam, obtaining a smaller focused spot diameter and a higher laser energy density. In occasions with larger aspect ratio requirements, a laser beam with a small diameter can be used to achieve the processing ability with a large aspect ratio. Therefore, this system can simultaneously meet the multiple requirements of large-format high-precision processing and small-format large-aspect ratio processing.

[0025] In the present invention, a two-axis planar mirror is used instead of the traditional scanning galvanometer to reduce the manufacturing cost of the system.

[0026] All lens materials in the present invention are common fused silica glass, which is easy to process and manufacture. Brief Description of the Drawings

[0027] Figure 1 It is a physical simulation diagram of the overall optical path of the laser dynamic focusing scanning system of the present invention.

[0028] Figure 2 It is a schematic diagram of the overall optical path structure of the laser dynamic focusing scanning system of the present invention.

[0029] Figure 3 It is an enlarged view of the lens structure of the laser dynamic focusing scanning system of the present invention.

[0030] Figure 4 It is a spot diagram (light density 200) of the laser dynamic focusing scanning system of the present invention. Among them, the differences in the parameters of a to j are as follows:

[0031]

[0032]

[0033] Figure 5 It is an energy-entering diffraction circle diagram of the laser dynamic focusing scanning system of the present invention. Among them, the differences in the parameters of a to j are as follows:

[0034]

[0035] Figure 6Processing, assembly and control tolerance settings for the laser dynamic focusing scanning system of the present invention.

[0036] Among them, 1 is the first lens; 2 is the second lens; 3 is the third lens; 4 is the fourth lens: 5 is the fifth lens; 6 is the sixth lens; 7 is the seventh lens. Specific embodiments

[0037] The following describes the present application in detail with reference to embodiments, but the present application is not limited to these embodiments.

[0038] Embodiment 1

[0039] First, the overall optical path structure of the dynamic focusing scanning system in the present invention is introduced. As Figure 1 , Figure 2 and Figure 3 shown, the optical path structure of the ultra-long distance and ultra-large range laser dynamic focusing scanning system described in the present invention includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4, a fifth lens 5, a sixth lens 6, a seventh lens 7 and a reflector arranged in sequence along the optical axis. Among them, the first lens is a dynamic focusing lens and can move along the optical axis, and the positions of the remaining lenses are fixed.

[0040] The laser beam passes through the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, and the seventh lens in sequence, and then is reflected by the reflector and finally focused on focal planes at different heights.

[0041] By adjusting the distance between the first lens and the second lens along the optical axis, dynamic focusing of the laser in space can be achieved. The distance range between the first lens and the second lens is 24.321 mm to 98.631 mm. By adjusting the deflection angles of the reflector around the X-axis and Y-axis in three-dimensional space, the propagation direction of the laser in space can be controlled, and the X and Y coordinates of the laser focus can be controlled. The maximum uniaxial mechanical deflection angle of the reflector is 45° ± 16.8°, and the central distance from the Z-axis direction of the focusing plane is 1650 mm to 2050 mm.

[0042] All relevant parameters of the optical path components can be referred to Table 1.

[0043] Table 1 Optical path component parameters

[0044]

[0045] Explanation of the relevant specifications in Table 1:

[0046] The described first lens is a meniscus positive lens, with the front surface curvature radius of 290 mm, the rear surface curvature radius of 1312.2 mm, the central thickness of 10 mm, and the distance between the first lens and the second lens is dynamically adjustable within the range of 24.321 mm to 98.631 mm.

[0047] The second lens mentioned above is a biconcave negative lens with a front surface curvature radius of -501.2 mm, a rear surface curvature radius of 325 mm, a central thickness of 10 mm, and the distance between the second lens and the third lens is 10 mm.

[0048] The third, fourth, and fifth lenses mentioned above are the same, all being meniscus negative lenses with a front surface curvature radius of -228.08 mm, a rear surface curvature radius of -228.08 mm, a central thickness of 10 mm, and the distances between the third, fourth, fifth, and sixth lenses are all 10 mm.

[0049] The sixth and seventh lenses mentioned above are the same, all being meniscus positive lenses with a front surface curvature radius of 501.2 mm, a rear surface curvature radius of 1560 mm, a central thickness of 10 mm, the distance between the sixth and seventh lenses is 10 mm, and the distance between the seventh lens and the mirror is 130 mm.

[0050] The central thickness of the mirror is 20 mm.

[0051] All the lens materials mentioned above are fused silica glass with a refractive index of 1.4585.

[0052] The laser beam mentioned above is a Gaussian beam with a wavelength of 1064 nm, a apodization factor of 1.5, and an entrance pupil diameter of 70 mm.

[0053] By adjusting the position of the dynamic focusing lens and the deflection angle of the mirror in the optical design software, different working states of the system during laser scanning in space can be effectively simulated. Table 2 shows the corresponding deflection angle of the mirror, the position of the dynamic focusing lens, the processing range that the system can reach, as well as the optical path and focal length of the entire optical path when scanning at the outermost edge and the center of the focusing plane at different heights. The optical path is the distance that the light travels after passing through the last lens and before reaching the focusing position.

[0054] Table 2 Different working states of the system during three-dimensional space laser scanning

[0055]

[0056]

[0057] Explanations are given for the relevant content in Table 2:

[0058] When the central distance between the mirror and the focusing plane in the Z-axis direction is 2050 mm, and the mirror deflects by 45° ± 13.9°, when the distance between the dynamic focusing lens and the second lens is 24.321 mm, the focusing of the laser can be achieved, and the achievable processing range is 2161.898 mm, meeting the requirement of the longest distance processing range within the 1.5 m × 1.5 m processing range (within the processing range ), and the system focal length is 2324.52 mm. When the mirror deflects by 45° ± 0°, when the distance between the dynamic focusing lens and the second lens is 59.879 mm, the central focusing of the laser on this height focusing plane can be achieved, and the system focal length is 2180.7 mm.

[0059] When the distance between the mirror and the focusing plane in the Z-axis direction is 1950 mm, and the mirror deflects by 45° ± 14.5°, when the distance between the dynamic focusing lens and the second lens is 35.507 mm, the focusing of the laser can be achieved, and the achievable processing range is 2161.984 mm, meeting the requirement of the longest distance processing range within the 1.5 m × 1.5 m processing range The system focal length is 2277.27 mm. When the mirror deflects by 45° ± 0°, when the distance between the dynamic focusing lens and the second lens is 74.43 mm, the central focusing of the laser on this height focusing plane can be achieved, and the system focal length is 2126.85 mm.

[0060] When the distance between the mirror and the focusing plane in the Z-axis direction is 1850 mm, and the mirror deflects by 45° ± 15.1°, when the distance between the dynamic focusing lens and the second lens is 47.322 mm, the focusing of the laser can be achieved, and the achievable processing range is 2153.598 mm, meeting the requirement of the longest distance processing range within the 1.5 m × 1.5 m processing range (within the processing range ) The system focal length is 2229.41 mm. When the mirror deflects by 45° ± 0°, when the distance between the dynamic focusing lens and the second lens is 89.749 mm, the central focusing of the laser on this height focusing plane can be achieved, and the system focal length is 2072.96 mm.

[0061] When the distance between the mirror and the focusing plane in the Z-axis direction is 1750 mm, and the mirror deflects by 45° ± 15.8°, when the distance between the dynamic focusing lens and the second lens is 59.219 mm, the focusing of the laser can be achieved, and the achievable processing range is 2153.328 mm, meeting the requirement of the longest distance processing range within the 1.5 m × 1.5 m processing range (within the processing range ) The system focal length is 2183.2 mm. When the mirror deflects by 45° ± 0°, when the distance between the dynamic focusing lens and the second lens is 105.9 mm, the central focusing of the laser on this height focusing plane can be achieved, and the system focal length is 2019.02 mm.

[0062] When the distance between the mirror and the focal plane in the Z-axis direction is 1650 mm, and the mirror deflects by 45° ± 16.5°, the distance between the dynamic focusing mirror and the second lens is 71.181 mm, and the laser can be focused. The achievable processing range is 2159.544 mm, which meets the requirement of the longest distance processing range within the 1.5 m × 1.5 m processing range (within the processing range ). The system focal length is 2200.42 mm. When the mirror deflects by 45° ± 0°, the distance between the dynamic focusing mirror and the second lens is 122.952 mm, and the laser can be focused at the center of this height focal plane. The system focal length is 2019.02 mm.

[0063] Figure 4 Figure is the spot diagram (light density 200) of the laser dynamic focusing scanning system. It can be seen from the figure that in different states of the system, within the complete scanning space range, the RMS radius of the focused spot is less than 27 μm, and it has strong roundness.

[0064] Figure 5 Figure is the diffraction circle energy-entering diagram of the laser dynamic focusing scanning system. It can be seen from the figure that in different states of the system, within the complete scanning space range, more than 90% of the system energy can be enclosed within a radius of 50 μm from the centroid, and the system is close to the diffraction limit. Subsequently, corresponding antireflection coatings can be deposited on each surface of the lens, and a corresponding high-reflection coating can be deposited on the mirror surface to reduce the energy loss of the laser when passing through the lens.

[0065] Considering the tolerances in the lens processing, assembly, and control processes of the system, set the tolerances as shown in Figure 6 in the optical design software, and simulate the influence of the tolerances on the focused spot of the system within the complete scanning space through the Monte Carlo algorithm (Monte Carlo run number = 1000). All tolerances are set to be achievable by the existing optical system processing, assembly equipment, and control methods. Since the deflection angle of the mirror determines the propagation direction of the laser and has a great influence on the final focusing effect of the laser, when simulating in the optical design software, set the tolerances of the deflection angles of the mirror along the X-axis and Y-axis in the three-dimensional space to ±0.03°.

[0066] After fully considering the lens processing, assembly, and control tolerances, the RMS radius of the focused spot of the system within the complete scanning space is shown in Table 3. When laser scanning is performed at the outermost edge and the center of the focused plane at different heights, under different mirror deflection angles, the nominal value of the RMS radius of the focused spot, the optimal value of the RMS radius of the focused spot, the average value of the RMS radius of the focused spot, the RMS radius of the focused spot in 80% of the cases, the RMS radius of the focused spot in 50% of the cases, the RMS radius of the focused spot in 20% of the cases, and the RMS radius of the focused spot in 10% of the cases are all less than 50 μm, demonstrating that the system has strong stability and that the influence of processing, assembly, and control tolerances on the system is relatively small.

[0067] Table 3 RMS Radius of the Focused Spot of the System under Different Working Conditions (Considering Processing, Assembly, and Control Tolerances)

[0068]

[0069] The following are specific embodiments:

[0070] Example 1: Three-dimensional laser etching of a large-format titanium alloy plate by a dynamic focusing scanning optical system.

[0071] This dynamic focusing scanning optical system, in cooperation with a laser with an average power of 60 W, a wavelength of 1064 nm, and a pulse length of 10 ps, can achieve three-dimensional laser etching of a large-format titanium alloy plate. The scanning range and processing path of the optical system can be set according to the size of the workpiece to be processed.

[0072] Example 2: Three-dimensional laser cleaning of the paint layer on the surface of an aluminum alloy by a dynamic focusing scanning optical system.

[0073] This dynamic focusing scanning optical system, in cooperation with a fiber laser with a maximum power of 30 W and a wavelength of 1064 nm, can achieve three-dimensional laser cleaning of the paint layer on the surface of an aluminum alloy over a large area.

[0074] The optical path of the dynamic focusing scanning system introduced in the present invention can achieve focused scanning of the laser within a space of 1.5 m × 1.5 m × 0.4 m. The maximum focal length of the system can exceed 2300 mm. The RMS radius of the focused spot is less than 27 μm, and it has good roundness. Through the combined design of multiple lenses, the stability of the system is greatly improved. After fully considering the actual processing, assembly, and control tolerances of each lens, the RMS radius of the focused spot within the scanning space is less than 50 μm, the spot consistency is good, and better imaging quality is obtained, which can meet the application requirements in the fields of laser advanced manufacturing such as laser etching and laser cleaning.

[0075] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can make several modifications or substitutions, which should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims

1. The optical path structure of a three-dimensional dynamic focusing scanning system, characterized in that it is composed of a first lens, a second lens, a third lens, a fourth lens, a fifth lens, a sixth lens, a seventh lens and a reflector arranged in sequence along the optical axis; The laser beam passes through the first lens, the second lens, the third lens, the fourth lens, the fifth lens, the sixth lens, the seventh lens and the reflector in sequence and then focuses on focal planes at different heights; The first lens is a dynamic focusing lens that can move along the optical axis and is used to control the focusing diameter of the laser beam and the Z coordinate of the laser focus in a three-dimensional rectangular coordinate system. Dynamic focusing can be achieved by adjusting the distance between the first lens and the second lens along the optical axis. The distance between the first lens and the second lens varies within the range of 24.321 mm to 98.631 mm, and the positions of the remaining lenses are fixed.

2. The optical path structure of the three-dimensional dynamic focusing scanning system according to claim 1, characterized in that the first lens is a meniscus positive lens, the second lens is a biconcave negative lens, the third, fourth, and fifth lenses are the same and are all meniscus negative lenses, and the sixth and seventh lenses are the same and are all meniscus positive lenses.

3. The optical path structure of the three-dimensional dynamic focusing scanning system according to claim 1, characterized in that the front surface curvature radius of the first lens is 290 mm, and the rear surface curvature radius is 1312.2 mm; the central thickness of the first lens is 10 mm, and the distance between the first lens and the second lens is dynamically adjustable within the range of 24.321 mm to 98.631 mm.

4. The optical path structure of the three-dimensional dynamic focusing scanning system according to claim 1, characterized in that the front surface curvature radius of the second lens is -501.2 mm, and the rear surface curvature radius is 325 mm; the central thickness of the second lens is 10 mm, and the distance between the second lens and the third lens is 10 mm.

5. The optical path structure of the three-dimensional dynamic focusing scanning system according to claim 1, characterized in that the third, fourth, and fifth lenses have the same structure, the front surface curvature radius is -228.08 mm, and the rear surface curvature radius is -228.08 mm; the central thickness of the third, fourth, and fifth lenses is 10 mm, and the distances between the third, fourth, fifth, and sixth lenses are all 10 mm.

6. The optical path structure of the three-dimensional dynamic focusing scanning system according to claim 1, characterized in that the sixth and seventh lenses have the same structure, the front surface curvature radius is 501.2 mm, and the rear surface curvature radius is 1560 mm; the central thickness of the sixth and seventh lenses is 10 mm, and the distance between the sixth and seventh lenses is 10 mm.

7. The optical path structure of the three-dimensional dynamic focusing scanning system according to claim 1, characterized in that the distance between the seventh lens and the reflector is 130 mm.

8. The optical path structure of the three-dimensional dynamic focusing scanning system according to claim 1, characterized in that The mirror is a two-axis planar mirror for controlling the propagation direction of the laser in space. It can deflect simultaneously around the X-axis and Y-axis in three-dimensional space to control the X coordinate and Y coordinate of the laser focus in the three-dimensional rectangular coordinate system. The maximum single-axis mechanical deflection angle is 45° ± 16.8°, and the distance from the Z-axis direction of the focusing plane is 1650 mm to 2050 mm.

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