Multi-path laser beam-combining linear light spot homogenizing system and working method thereof

Abstract

The invention particularly relates to a multi-path laser beam combination linear light spot homogenization system and a working method thereof. The linear light spot homogenizing system comprises a micro-spherical scale array reflector, an aspheric reflector, a plano-convex cylindrical focusing mirror and a laser light source arranged at the periphery of the aspheric reflector; the micro-spherical scale array reflector is arranged on the rear side of the aspheric reflector by taking the laser incidence direction as the positive direction; the whole front surface of the micro-spherical scale array reflector is a concave spherical surface with the curvature radius of R; and square micro-concave spherical reflectors with the curvature radius of r and the length * width of d * d are uniformly and tightly distributed on the front surface of the micro-spherical scale array reflector. According to the system, the common-path design of the multi-path high-energy laser beam combining-homogenizing-focusing module is realized, and the problems that the linear light spot energy uniformity is greatly influenced by spherical aberration and the single-beam laser homogenizing light spot energy is small are solved. The optical path system is simple and easy to integrate, and can be applied to various industrial scenes such as laser surface treatment.

Description

[0001] Technical Field

[0002] The present invention relates to a line spot homogenization system for multi-channel laser beam combination and its working method, belonging to the technical field of measurement of the coefficient of thermal expansion of materials. Background Art

[0003] As a core means in the field of advanced manufacturing, laser surface treatment and processing technology has been widely applied in processes such as metal additive manufacturing, surface hardening, cladding, welding, and precision cutting. Among them, due to the characteristics of high energy density distribution, line spots show significant advantages in high-efficiency large-area processing. However, in the prior art, there are still many technical bottlenecks in realizing large-energy, highly uniform, and length-adjustable line spots, and it is urgent to break through the limitations of traditional solutions through innovative designs.

[0004] The current mainstream line spot generation technologies are mainly based on beam shaping elements, including cylindrical lens groups, diffractive optical elements (DOEs), and microlens arrays, etc. The cylindrical lens group can convert a Gaussian beam into a linear spot through one-dimensional beam expansion and focusing, but it cannot output a homogenized spot and is difficult to meet the requirements of uniform surface processing. Although diffractive optical elements can design complex light field distributions through coding algorithms, they are easily affected by thermal distortion in high-power laser scenarios, which will lead to a decrease in diffraction efficiency and damage to the elements. The microlens array combined with integral homogenization technology can improve the uniformity, but the energy loss introduced by the multi-stage optical system is relatively high, and the adjustment of the spot length depends on the mechanical displacement mechanism, which is difficult to meet the requirements of high-speed dynamic processing. Moreover, the lens-type optical path transmission system will introduce spherical aberration during beam shaping, resulting in deterioration of the spot homogenization quality.

[0005] To achieve large-energy output and meet the requirements of multi-scene and high-efficiency laser surface treatment, the method of combining multiple light sources is usually used to achieve high-energy laser output. Currently, the methods of combining multiple laser sources for output mostly adopt polarization beam combination, wavelength beam combination, or spatial beam combination schemes. Among them, polarization beam combination depends on the polarization characteristics of the laser, has strict requirements for the laser wavelength and polarization purity, and the number of combined beams is limited (usually ≤ 4). Wavelength beam combination requires multiple sets of lasers with different wavelengths to be matched, and the system is complex and costly. Spatial beam combination realizes energy superposition through non-coaxial arrangement, but the interference effect in the beam overlap area will cause light intensity fluctuations and significant deterioration of uniformity. In addition, the existing beam combination schemes generally lack a design that coordinates with the homogenization module, and it is difficult to achieve both high energy transfer efficiency and high spot quality. Therefore, how to spatially combine and output 6 or more high-energy laser beams, while realizing high-quality homogenization and focusing functions, so as to significantly improve the adaptability of the laser surface treatment process, is still a key problem that needs to be solved urgently. Summary of the Invention

[0006] Aiming at the deficiencies of the prior art, the present invention provides a line spot homogenization system for multi-channel laser beam combination.

[0007] The present invention also provides a working method of the above-mentioned line spot homogenization system.

[0008] Summary of the invention: The present invention proposes a line spot homogenization system for multi-channel laser beam combination, realizing the common optical path design of the multi-channel high-energy laser beam combination-homogenization-focusing module, and solving the problems that the energy uniformity of the line spot is greatly affected by spherical aberration and the energy of the homogenized spot of a single laser beam is small. The optical path system is simple and easy to be integrated, and can be applied to various industrial scenarios such as laser surface treatment.

[0009] The technical solution of the present invention is as follows:

[0010] A line spot homogenization system for multi-channel laser beam combination includes a micro-spherical scale array mirror, an aspherical mirror, a plano-convex cylindrical focusing mirror and a laser light source arranged outside the aspherical mirror; taking the laser incident direction as the positive direction, the micro-spherical scale array mirror is arranged at the rear side of the aspherical mirror;

[0011] The front surface of the micro-spherical scale array mirror is an overall concave spherical surface with a radius of curvature of R; on the front surface of the micro-spherical scale array mirror, square micro-concave spherical mirrors with a radius of curvature of r and a length×width of d×d are evenly and closely distributed, and the square micro-concave spherical mirrors form micro-spherical reflecting scales; where R>r, d<2r; a square hole of N×N is arranged at the vertex position of the concave spherical surface of the front surface of the micro-spherical scale array mirror, and the four sides of the square through hole are parallel to the four sides of the square micro-concave spherical surface in pairs; the rear surface of the micro-spherical scale array mirror is a plane; the square through hole allows the light reflected by the aspherical mirror to pass through;

[0012] The aspherical mirror is a plano-concave aspherical mirror, its optical axis coincides with the normal direction at the vertex of the concave spherical surface of the micro-spherical scale array mirror, and its concave surface direction is opposite to the concave surface direction of the front surface of the micro-spherical scale array mirror; the concave surface radius of curvature of the aspherical mirror is Q; the aspherical mirror is used to shape the micro-focused beam into multiple micro-parallel beams and make each micro-parallel beam converge at the same position on the homogenization plane.

[0013] The plano-convex cylindrical focusing mirror is arranged between the micro-spherical scale array mirror and the aspherical mirror, and its optical axis coincides with the normal direction at the vertex of the concave spherical surface of the micro-spherical scale array mirror; the plano-convex cylindrical focusing mirror shapes the homogenized spot into a line shape;

[0014] Preferably, the overall size of the plano-convex cylindrical focusing mirror is smaller than the clear aperture of the aspherical mirror; N is smaller than the clear aperture of the aspherical mirror.

[0015] Preferably, the laser light source generates collimated beams, and their transmission directions are parallel to each other.

[0016] Further preferably, the cross-sectional arrangement of the collimated light spots generated by the laser light source is disordered or ordered; the ordered arrangement is circular or square.

[0017] Preferably, the reflecting surfaces of the micro-spherical scale array mirror and the aspherical mirror are coated with a reflective film, and the plano-convex cylindrical focusing lens is coated with an anti-reflection film on both sides; the rear surface of the micro-spherical scale array mirror is flat, and a flat glass coated with an anti-reflection film on both sides is provided as a protection window on the rear surface.

[0018] Preferably, the set distance between the vertex of the reflecting surface of the aspherical mirror and the vertex of the front surface of the micro-spherical scale array mirror is L, and L is:

[0019]

[0020] The uniform linear light spot is located outside the rear surface of the micro-spherical scale array mirror. The distance between the vertex of the front surface and the rear surface of the micro-spherical scale array mirror is n, and the set distance between the plane where the homogenized linear light spot is located and the vertex of the reflecting surface of the aspherical mirror is D, and D is:

[0021]

[0022] The focal length of the plano-convex cylindrical focusing lens is F, and the distance between its convex surface and the vertex of the reflecting surface of the aspherical mirror is M, and M is:

[0023] M = D - F

[0024] The length Y of the uniform linear light spot is:

[0025]

[0026] The change of the uniform linear light spot can be realized by changing the curvature radius of the reflecting surface of the aspherical mirror and the curvature radius of the micro-concave sphere. The change in the width direction of the uniform linear light spot is realized by changing the position of the plano-convex cylindrical focusing lens on the optical axis.

[0027] Further preferably, the focal length F of the plano-convex cylindrical focusing lens < D.

[0028] A working method of the above-mentioned linear light spot homogenization system. First, multiple mutually parallel collimated laser light sources are incident on the front surface of the micro-spherical scale array mirror, and the incident direction is the normal direction at the concave spherical vertex of the micro-spherical scale array mirror; the micro-spherical reflecting scales split the collimated light source into multiple micro-focused light beams;

[0029] Since the whole of the micro-spherical reflecting scales is spherical, each micro-focused light beam enters the aspherical mirror through the spherical reflection of the square micro-concave spherical mirror; after receiving each micro-focused light beam, the aspherical mirror shapes the micro-focused light beam into multiple micro-parallel light beams, and the diameters of each micro-parallel light beam are equal;

[0030] After being reflected by the aspherical mirror, each bundle of slightly parallel light beams enters the plano-convex cylindrical focusing mirror and is focused in the width direction, while maintaining the original path in the length direction; after passing through the square hole, the light beams are finally distributed at the same position on the combined focal plane of the micro-spherical scale array mirror and the aspherical mirror, forming a uniform linear light spot after multi-path beam combination. When two lenses / mirrors with focal lengths are on the same optical axis, they will jointly focus the incident light, and the focal plane of this focus is the combined focal plane.

[0031] Preferably, the number of laser beams that the linear light spot homogenization system for multi-path laser beam combination can accept is 1 to 30. The number of laser light sources is jointly determined by the target surface sizes of the micro-spherical scale array mirror and the aspherical mirror and the beam diameter of the laser light source, meeting the conditions that the laser light sources do not overlap with each other, the light sources are outside the aspherical mirror, and can be incident on the front surface of the micro-spherical scale array mirror, and the parameters of the laser light sources can be different from each other.

[0032] The beneficial effects of the present invention are as follows:

[0033] (1) The linear light spot homogenization system for multi-path laser beam combination according to the present invention can combine multiple collimated laser beams; after combining multiple collimated laser beams, a homogenized linear light spot is formed;

[0034] (2) The linear light spot homogenization system for multi-path laser beam combination according to the present invention performs beam shaping through the micro-spherical scale array mirror and the aspherical mirror, which can avoid the introduction of spherical aberration by the lens-type shaping system and improve the uniformity of the light spot energy;

[0035] (3) The linear light spot homogenization system for multi-path laser beam combination according to the present invention has a simple optical path and strong stability, and is suitable for integrated production and industrial applications. Description of the Drawings

[0036] Figure 1 It is a schematic diagram of the overall structure of the linear light spot homogenization system for multi-path laser beam combination according to the present invention;

[0037] In the figure: 1 - micro-spherical scale array mirror, 2 - aspherical mirror, 3 - plano-convex cylindrical focusing mirror.

[0038] Figure 2a It is a cross-sectional distribution diagram of a symmetric square light spot;

[0039] Figure 2b It is a cross-sectional distribution diagram of a symmetric circular light spot;

[0040] Figure 3 It is a schematic diagram of the dimensions of the linear light spot homogenization system for multi-path laser beam combination according to the present invention;

[0041] Figure 4aGray scale map of the homogenized spot energy distribution of the line spot homogenization system in Example 7;

[0042] Figure 4b Cross-sectional view of the homogenized spot energy distribution of the line spot homogenization system in Example 7. Detailed implementation manners

[0043] The following will describe in detail some implementation manners of the present invention with reference to the accompanying drawings.

[0044] Example 1

[0045] As Figure 1 shown.

[0046] A line spot homogenization system for multi-channel laser beam combination includes a micro-spherical scale array mirror (1), an aspherical mirror (2), a plano-convex cylindrical focusing lens (3), and a laser light source disposed around the aspherical mirror (2); taking the laser incident direction as the positive direction, the micro-spherical scale array mirror (1) is disposed behind the aspherical mirror (2);

[0047] The front surface of the micro-spherical scale array mirror (1) is an overall concave spherical surface with a radius of curvature of R; on the front surface of the micro-spherical scale array mirror (1), square micro-concave spherical mirrors with a radius of curvature of r and a length × width of d×d are uniformly and closely distributed, and the square micro-concave spherical mirrors form micro-spherical reflecting scales; where R>r, d<2r; a square hole of N×N is provided at the vertex position of the concave spherical surface on the front surface of the micro-spherical scale array mirror (1), and the four sides of the square through hole are pairwise parallel to the four sides of the square micro-concave spherical surface; the rear surface of the micro-spherical scale array mirror (1) is a plane;

[0048] The aspherical mirror (2) is a plano-concave aspherical mirror, its optical axis coincides with the normal direction at the vertex of the concave spherical surface of the micro-spherical scale array mirror (1), and its concave surface direction is opposite to the concave surface direction of the front surface of the micro-spherical scale array mirror (1); the concave surface radius of curvature of the aspherical mirror (2) is Q;

[0049] The plano-convex cylindrical focusing lens (3) is disposed between the micro-spherical scale array mirror (1) and the aspherical mirror (2), and its optical axis coincides with the normal direction at the vertex of the concave spherical surface of the micro-spherical scale array mirror (1); the plano-convex cylindrical focusing lens (3) shapes the homogenized spot into a linear shape;

[0050] In this example, the wavelength of the laser light source is 1064 nm and the spot diameter is 5 mm. The laser light source generates collimated beams, and their transmission directions are parallel to each other. The cross-sectional arrangement of the collimated spots generated by the laser light source is an unordered arrangement or an ordered arrangement; in this example, it is a circular arrangement, as Figure 2b shown.

[0051] Example 2

[0052] As Figure 2a shown

[0053] The line spot homogenization system for multi - path laser beam combination as described in Embodiment 1, the difference is that the cross - section of the collimated spot generated by the laser light source is arranged in a square shape.

[0054] Embodiment 3

[0055] The line spot homogenization system for multi - path laser beam combination as described in Embodiment 1, further, the overall size of the plano - convex cylindrical focusing mirror (3) is smaller than the clear aperture of the aspherical mirror (2); N is smaller than the clear aperture of the aspherical mirror (2).

[0056] Embodiment 4

[0057] The line spot homogenization system for multi - path laser beam combination as described in Embodiment 1, further, the reflecting surfaces of the micro - spherical scale - like array mirror (1) and the aspherical mirror (2) are coated with a reflective film, and both sides of the plano - convex cylindrical focusing mirror (3) are coated with an anti - reflection film; the rear surface of the micro - spherical scale - like array mirror (1) is a plane, and a flat glass coated with an anti - reflection film on both sides is provided as a protection window on the rear surface.

[0058] Embodiment 5

[0059] As Figure 3 shown

[0060] The line spot homogenization system for multi - path laser beam combination as described in Embodiment 1, further, the set distance between the vertex of the reflecting surface of the aspherical mirror (2) and the vertex of the front surface of the micro - spherical scale - like array mirror (1) is L, and L is:

[0061]

[0062] The uniform line spot is outside the rear surface of the micro - spherical scale - like array mirror (1), the distance between the vertex of the front surface and the rear surface of the micro - spherical scale - like array mirror (1) is n, and the set distance between the plane where the homogenized line spot is located and the vertex of the reflecting surface of the aspherical mirror (2) is D, and D is:

[0063]

[0064] The focal length of the plano - convex cylindrical focusing mirror (3) is F, and the distance between its convex surface and the vertex of the reflecting surface of the aspherical mirror (2) is M, and M is:

[0065] M = D - F

[0066] The length Y of the uniform line spot is:

[0067]

[0068] Embodiment 6

[0069] The line spot homogenization system for multi-beam laser beam combination as described in Embodiment 5. Further, the focal length F of the plano-convex cylindrical focusing lens (3) is less than D.

[0070] Embodiment 7

[0071] A working method of the line spot homogenization system as described in any one of Embodiments 1-6. First, multiple mutually parallel collimated laser light sources are incident on the front surface of the micro-spherical scale array mirror (1), and the incident direction is the normal direction at the concave spherical vertex of the micro-spherical scale array mirror (1); the micro-spherical reflecting scales split the collimated light source into multiple micro-focused light beams;

[0072] Since the whole of the micro-spherical reflecting scales is spherical, each micro-focused light beam enters the aspherical mirror (2) through the spherical reflection of the square micro-concave spherical mirror; after receiving each micro-focused light beam, the aspherical mirror (2) shapes the micro-focused light beam into multiple micro-parallel light beams, and the diameters of each micro-parallel light beam are equal;

[0073] After passing through the aspherical mirror (2), each micro-parallel light beam is focused in the width direction after entering the plano-convex cylindrical focusing lens (3), and its path remains unchanged in the length direction; after passing through the square hole, the light beams are finally distributed at the same position on the combined focal plane of the micro-spherical scale array mirror (1) and the aspherical mirror (2), forming a uniform line spot after multi-path beam combination.

[0074] As Figure 4a 、 Figure 4b shown, the line spot homogenization system for multi-beam laser beam combination in this embodiment shapes the light beam through the micro-spherical scale array mirror (1) and the aspherical mirror (2), which can avoid the spherical aberration introduced by the lens type shaping system and improve the uniformity of the spot energy; for the line spot homogenization system for multi-beam laser beam combination in this embodiment, the uniformity of the line spot energy is ≥ 95%.

[0075] Embodiment 8

[0076] The line spot homogenization system for multi-beam laser beam combination as described in Embodiment 7. Further, the line spot homogenization system for multi-beam laser beam combination can accept 25 laser beams.

Claims

1. A multi-channel laser beam combining line spot homogenization system, characterized in that: The invention comprises a microspherical scale armor array reflector, an aspherical reflector, a plano-convex cylindrical focusing mirror and a laser light source arranged at the periphery of the aspherical reflector; with the laser incident direction as the positive direction, the microspherical scale armor array reflector is arranged at the rear side of the aspherical reflector; the front surface of the microspherical scale armor array reflector is a concave spherical surface with a curvature radius of R as a whole; square micro-concave spherical reflectors with a curvature radius of r and a length×width of d×d are uniformly and closely distributed on the front surface of the microspherical scale armor array reflector, and the square micro-concave spherical reflectors form microspherical reflection scale armor; wherein R>r, d<2r; the vertex position of the concave spherical surface on the front surface of the microspherical scale armor array reflector is provided with The square hole is N×N, and the four sides of the square through hole are parallel to the four sides of the square micro-concave sphere in pairs; the rear surface of the micro-spherical scale armor array reflector is a plane; the aspheric reflector is a plano-concave aspheric reflector, and its optical axis coincides with the normal direction at the vertex of the concave sphere of the micro-spherical scale armor array reflector, and its concave direction is opposite to the concave direction of the front surface of the micro-spherical scale armor array reflector; the concave curvature radius of the aspheric reflector is Q; the plano-convex cylindrical focusing mirror is arranged between the micro-spherical scale armor array reflector and the aspheric reflector, and its optical axis coincides with the normal direction at the vertex of the concave sphere of the micro-spherical scale armor array reflector; the plano-convex cylindrical focusing mirror shapes the homogenized light spot into a linear shape.

2. The multi-path laser beam combining linear spot homogenization system as described in Example 1 is characterized in that: The overall size of the plano-convex cylindrical focusing mirror is smaller than the clear aperture of the aspheric reflector; N is smaller than the clear aperture of the aspheric reflector.

3. The multi-path laser beam combining linear spot homogenization system as described in Example 1 is characterized in that: The laser light sources generate collimated light beams, the transmission directions of which are parallel to each other.

4. The linear spot homogenization system for multi-channel laser beam combining as described in Example 3 is characterized in that: The cross-sectional arrangement of the collimated light spot generated by the laser light source is disordered arrangement or ordered arrangement; the ordered arrangement is circular arrangement or square arrangement.

5. The linear spot homogenization system for multi-channel laser beam combining as described in Example 1 is characterized in that: The reflective surfaces of the microspherical scale-armor array reflector and the aspherical reflector are coated with reflective films, and the plano-convex cylindrical focusing mirror is coated with anti-reflection films on both sides; the rear surface of the microspherical scale-armor array reflector is a plane, and a flat glass with double-sided anti-reflection films is arranged on the rear surface as a protective window.

6. The linear spot homogenization system for multi-channel laser beam combining as described in Example 1 is characterized in that: The setting distance between the vertex of the reflecting surface of the aspherical reflector and the vertex of the front surface of the micro-spherical scale array reflector is L, where L is: The uniform line spot is located outside the rear surface of the microspherical scale array reflector. The distance between the front surface vertex and the rear surface of the microspherical scale array reflector is n. The setting distance between the plane where the uniform line spot is located and the vertex of the reflective surface of the aspherical reflector is D, and D is: The focal length of the plano-convex cylindrical focusing mirror is F, and the distance between its convex surface and the vertex of the reflecting surface of the aspheric reflecting mirror is M, where M is: M=DF The length Y of the uniform line spot is:

7. The multi-path laser beam combining linear spot homogenization system as described in Example 6 is characterized in that: The focal length of the plano-convex cylindrical focusing mirror is F<D.

8. A working method of the line spot homogenization system as described in any one of embodiments 1-7, characterized in that: A plurality of mutually parallel collimated laser light sources first enter the front surface of a microspherical scale armor array reflector, and the incident direction is the normal direction of the vertex of the concave spherical surface of the microspherical scale armor array reflector; the microspherical reflective scale armor splits the collimated light source into a plurality of micro-focused light beams; since the microspherical reflective scale armor is a spherical surface as a whole, each micro-focused light beam enters an aspherical reflector through spherical reflection of a square micro-concave spherical reflector; after receiving each micro-focused light beam, the aspherical reflector shapes the micro-focused light beam into a plurality of micro-parallel light beams, and each micro-parallel light beam has the same diameter; after each micro-parallel light beam is reflected by the aspherical reflector into a plano-convex cylindrical focusing mirror, focusing in the width direction is achieved, and the original path is maintained in the length direction; after passing through the square hole, the light beam is finally distributed at the same position of the combined focal plane of the microspherical scale armor array reflector and the aspherical reflector, forming a uniform line light spot after the multi-light path is combined.

9. The working method of the line spot homogenization system as described in Example 8 is characterized by: The multi-path laser beam combining linear spot homogenization system can accept 1 to 30 laser beams.

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