LD area array beam shaping and homogenizing system based on micro-lens array and use method of LD area array beam shaping and homogenizing system

Abstract

The invention relates to an LD area array beam shaping and homogenizing system based on a microlens array and a use method thereof. The system comprises an LD area array light source, a fast axis pre-correction unit, a two-dimensional shaping and homogenizing unit, a relay lens group and an output coupling unit which are sequentially arranged along a light path, the fast axis pre-correction unit is a single-row micro-cylindrical lens array composed of a plurality of micro-cylindrical lenses; the two-dimensional shaping and homogenizing unit comprises a first microlens array and a second microlens array which are sequentially arranged along the optical axis, and the first microlens array and the second microlens array are both positive spherical microlens arrays arranged in an N * N matrix. According to the LD area array light beam shaping and homogenizing system, light beam segmentation and superposition are achieved, eventually homogenization of output light spots is achieved, and the light spot uniformity reaches 90% or above.

Description

Technical Field

[0001] This invention relates to the field of laser technology, specifically to a LD beam shaping and homogenization system based on a microlens array and its application method. Background Technology

[0002] LD arrays are increasingly widely used in industrial and scientific research fields due to their advantages such as small size, high electro-optical conversion efficiency, and high power density. However, the waveguide structure of the active region of an LD array causes its output beam to exhibit significant astigmatic characteristics. Specifically, the bar array bars have a large divergence angle along the fast axis, reaching 40°~60°, while the divergence angle along the slow axis is smaller, only 8°~12°. This difference in divergence angles results in an asymmetrical Gaussian-like beam distribution of output energy in the horizontal and vertical directions. This beam quality defect severely limits its application in scenarios with stringent requirements for beam quality, such as high-precision machining and uniform illumination.

[0003] Existing LD beam processing schemes have several shortcomings: First, the scheme that uses two independent microlens arrays to align the fast and slow axes separately requires high-precision assembly and adjustment, is complex to operate, and is prone to introducing interface losses, resulting in a collimation efficiency of less than 80%; Second, although a single aspherical microlens array can achieve two-dimensional collimation, the aspherical surface is difficult to process and costly, making it difficult to meet the needs of mass production; Third, traditional compound eye lens homogenization systems are sensitive to relative position errors between lenses, especially the roll angle error of the second array, which will significantly reduce the homogenization effect, and cannot simultaneously solve the dual problems of astigmatism correction and energy homogenization.

[0004] Therefore, there is an urgent need for an LD array beam shaping and homogenization system that combines strong astigmatism correction capability, stable homogenization effect, convenient processing and assembly, and controllable cost, in order to break through the existing technical bottlenecks. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a LD area array beam shaping and homogenization system based on a microlens array and its usage method. Through the collaborative design of multi-level microlens arrays, it achieves integrated functions of astigmatism correction and beam spot homogenization, while reducing the difficulty of processing and assembly.

[0006] Terminology Explanation: LD array: It is a semiconductor laser device composed of multiple laser diodes integrated in a two-dimensional array, where each laser diode is an independent light-emitting unit.

[0007] The technical solution of the present invention is as follows: This invention provides an LD array beam shaping and homogenization system based on a microlens array, comprising an LD array light source, a fast-axis pre-correction unit, a two-dimensional shaping and homogenization unit, a relay lens group, and an output coupling unit arranged sequentially along the optical path; The fast-axis pre-correction unit is a single-row micropillar lens array composed of several micropillar lenses, wherein the generatrix direction of the micropillar lenses is parallel to the fast axis of the LD array light source, and the difference between the center distance of adjacent micropillar lenses and the fast-axis distance of the LD array light source light-emitting unit is ≤±2μm; the focal length of the micropillar lens is f1; the fast-axis pre-correction unit of the present invention is used to compress the divergence angle of the fast axis direction of the bar to match the slow axis direction. The two-dimensional shaping and homogenizing unit includes a first microlens array and a second microlens array arranged sequentially along the optical axis. Both the first microlens array and the second microlens array are positive spherical microlens arrays arranged in an N×N matrix. The focal length of the first microlens array is f2, and the focal length of the second microlens array is f3. The distance between the first microlens array and the second microlens array is a=f2+f3, forming a variant 4f optical system structure.

[0008] According to a preferred embodiment of the present invention, the relay lens group includes a convex mirror and a concave mirror arranged sequentially along the optical axis, wherein the focal length of the convex mirror is f4, the focal length of the concave mirror is f5, and the distance between the convex mirror and the concave mirror is d=|f5|-f4; the relay lens group of the present invention is used to collimate and amplify the homogenized beam and adjust the output spot size.

[0009] According to a preferred embodiment of the present invention, the deviation between the optical axis of each microlens in the first microlens array and the central optical axis of the corresponding light-emitting unit of the LD array light source is ≤ ±1 μm, and the second microlens array is fixed by a six-degree-of-freedom adjustment frame to control the roll angle error to ≤ 0.1°, so as to ensure the stability of the homogenization effect.

[0010] According to a preferred embodiment of the present invention, the micropillar lenses of the single-row micropillar lens array are made of quartz glass and are prepared by photolithography-ion beam etching process, with a surface roughness Ra≤0.5nm.

[0011] According to a preferred embodiment of the present invention, the microlenses of both the first microlens array and the second microlens array are made of fused silica material and coated with an antireflective film, wherein the transmittance of the antireflective film is ≥99.5%.

[0012] According to a preferred embodiment of the present invention, the output coupling unit is a plano-convex lens, with the planar side of the plano-convex lens close to the relay lens group, for adjusting the divergence angle of the final output beam, thereby achieving continuous adjustment of the spot size.

[0013] The present invention also provides a method for using the above-mentioned LD array beam shaping and homogenization system.

[0014] A method for using a microlens array-based LD beam shaping and homogenization system includes the following steps: The astigmatic beam output from the LD array light source is first incident on the fast axis pre-correction unit, where the divergence angle in the fast axis direction is compressed to match that in the slow axis direction. The beam then enters the first microlens array and is split into multiple sub-beams. Each sub-beam is collimated by the first microlens and then incident on the second microlens array. The sub-beams are superimposed and homogenized at the focal plane after passing through the second microlens array. The homogenized beam is collimated and magnified by the relay lens group and finally output as a light spot through the output coupling unit.

[0015] The technical features and beneficial effects of this invention are as follows: 1. Astigmatism correction and homogenization integration: The fast axis pre-correction unit and the two-dimensional shaping and homogenization unit work together. The fast axis pre-correction unit first compresses the fast axis divergence angle to match the slow axis, and then the two microlens array forming a variant 4f optical system structure in the two-dimensional shaping and homogenization unit realizes beam splitting and superposition, and finally realizes the homogenization of the output light spot, with a light spot uniformity of over 90%. 2. High energy efficiency: The single-stage fast axis pre-correction and dual microlens array structure reduce the number of optical interfaces, making the system energy efficiency ≥90%, which is more than 10% higher than the traditional dual array separation scheme. 3. Convenient processing and assembly: The second microlens array achieves precise control of roll angle error through a six-degree-of-freedom adjustment frame, improving assembly efficiency by 40% and reducing batch processing costs by 30% compared to aspherical lens solutions; 4. Wide range of applications: By combining and adjusting the relay lens group and the output coupling unit, it can be adapted to LD arrays with power ranges from 100W to 10000W, so as to achieve continuous adjustment of the output spot size and divergence angle, and meet the application needs of multiple scenarios such as laser processing and annealing. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of the LD area array beam shaping and homogenization system based on microlens array of the present invention; Figure 2 This is a schematic diagram of the structure of the two-dimensional shaping and homogenizing unit of the present invention, wherein P LA Represents the microlens period; Figure 3 This is a schematic diagram of the relay lens group in this invention; In the figure: 1. LD area array light source, 2. Single row micropillar lens array, 3. First microlens array, 4. Second microlens array, 5. Relay lens group, 6. Output coupling unit, 7. Light spot; 51. Convex mirror; 52. Concave mirror. Detailed Implementation

[0017] The present invention will be further described below with reference to embodiments, but is not limited thereto. The described embodiments are some embodiments of the present invention. Based on these embodiments, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Furthermore, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other. Unless otherwise specified in the embodiments of the present invention, all techniques existing in the art can be used.

[0019] Example 1 like Figures 1-3 As shown, an LD array beam shaping and homogenization system based on a microlens array includes an LD array light source 1, a fast axis pre-correction unit, a two-dimensional shaping and homogenization unit, a relay lens group 5, and an output coupling unit 6 arranged sequentially.

[0020] The LD array light source 1 adopts a 10-bar structure, with a wavelength of 808nm, a fast-axis divergence angle of 50°, a slow-axis divergence angle of 12°, and an output power of 10000W.

[0021] The fast-axis pre-correction unit is a single-row micropillar lens array 2, wherein the generatrix direction of the micropillar lens is parallel to the fast axis of the LD array light source 1, the center-to-center distance between adjacent micropillar lenses is 1mm, which is equal to the fast-axis distance between the light-emitting units of the LD array light source 1, and the focal length of the micropillar lens is f1=600μm; the micropillar lens is made of quartz glass and is fabricated by photolithography-ion beam etching process, with a surface roughness Ra≤0.5nm.

[0022] The two-dimensional shaping and homogenizing unit consists of a first microlens array 3 and a second microlens array 4 arranged sequentially along the optical axis. Both are made of fused silica and coated with an 808nm antireflection film, achieving a transmittance of 99.6%. The first microlens array 3 consists of 10×10 matrix-arranged positive spherical microlenses with a focal length f2=2mm and a microlens period P. LA =1mm, optical diameter is 500μm; the second microlens array 4 is a 10×10 matrix arrangement of positive spherical microlenses, focal length f3=4mm, microlens period P LA =1mm; the spacing between the two arrays is a=f2+f3=6mm, the first microlens array 3 and the second microlens array 4 form a variant 4f optical system structure; the optical axis of each microlens in the first microlens array 3 deviates from the optical axis of the corresponding light-emitting unit of the LD surface array light source 1 by 1μm, and the second microlens array 4 is fixed by a six-degree-of-freedom adjustment frame, with the roll angle error controlled at 0.1° to ensure the stability of the homogenization effect.

[0023] The relay lens group 5 includes a convex mirror 51 and a concave mirror 52 arranged sequentially along the optical axis. The focal length of the convex mirror 51 is f4=50mm, the focal length of the concave mirror 52 is f5=-80mm, and the distance between the convex mirror 51 and the concave mirror 52 is d=|f5|-f4=30mm. Both are made of optical glass.

[0024] The output coupling unit 6 is a plano-convex lens. The planar side of the plano-convex lens is close to the relay lens group 5. The focal length of the plano-convex lens is f6=80mm, the optical diameter is 50mm, and the transmittance is ≥99.5%.

[0025] The method of using the above-mentioned LD beam shaping and homogenization system based on microlens array includes the following steps: The astigmatic beam output from the LD array light source 1 is first incident on the fast axis pre-correction unit, where the divergence angle in the fast axis direction is compressed to 12°, matching the slow axis direction. The beam then enters the first microlens array 3 and is divided into 100 sub-beams. Each sub-beam is collimated by the first microlens and then incident on the second microlens array 4. Since the distance between the two arrays satisfies the 4f condition, the sub-beams are superimposed and homogenized at the focal plane after passing through the second microlens array 4. The homogenized beam is collimated and magnified by the relay lens group 5 and finally output through the output coupling unit 6 to form a flat-top light spot 7 with a diameter of 20mm. The uniformity of the output light spot 7 is 95%.

Claims

1. A beam shaping and homogenization system for LD arrays based on microlens arrays, characterized in that, It includes an LD array light source, a fast axis pre-correction unit, a two-dimensional shaping and homogenizing unit, a relay lens group, and an output coupling unit arranged sequentially along the optical path; The fast-axis pre-correction unit is a single-row micropillar lens array composed of several micropillar lenses; the two-dimensional shaping and homogenization unit includes a first microlens array and a second microlens array arranged sequentially along the optical axis.

2. The LD beam shaping and homogenization system based on a microlens array according to claim 1, characterized in that, The generatrix of the micropillar lens is parallel to the fast axis of the LD array light source; the difference between the center distance of adjacent micropillar lenses and the fast axis distance of the LD array light source light-emitting unit is ≤ ±2μm.

3. The LD planar array beam shaping and homogenization system based on a microlens array according to claim 1, characterized in that, Both the first microlens array and the second microlens array are positive spherical microlens arrays arranged in an N×N matrix.

4. The LD planar array beam shaping and homogenization system based on a microlens array according to claim 1, characterized in that, The focal length of the first microlens array is f2, the focal length of the second microlens array is f3, and the distance between the first microlens array and the second microlens array is a = f2 + f3, forming a variant 4f optical system structure.

5. The LD planar array beam shaping and homogenization system based on a microlens array according to claim 1, characterized in that, The relay lens group includes a convex mirror and a concave mirror arranged sequentially along the optical axis. The focal length of the convex mirror is f4, the focal length of the concave mirror is f5, and the distance between the convex mirror and the concave mirror is d = |f5| - f4.

6. The LD planar array beam shaping and homogenization system based on a microlens array according to claim 1, characterized in that, The deviation between the optical axis of each microlens in the first microlens array and the central optical axis of the corresponding light-emitting unit of the LD array light source is ≤ ±1 μm. The second microlens array is fixed by a six-degree-of-freedom adjustment frame to control the roll angle error to ≤ 0.1°.

7. The LD beam shaping and homogenization system based on a microlens array according to claim 1, characterized in that, The micropillar lenses of the single-row micropillar lens array are made of quartz glass and are prepared by photolithography-ion beam etching process, with a surface roughness Ra≤0.5nm.

8. The LD beam shaping and homogenization system based on a microlens array according to claim 1, characterized in that, Both the microlenses in the first and second microlens arrays are made of fused silica and coated with an antireflective film, the transmittance of which is ≥99.5%.

9. The LD beam shaping and homogenization system based on a microlens array according to claim 1, characterized in that, The output coupling unit is a plano-convex lens, and the planar side of the plano-convex lens is close to the relay lens group.

10. A method of using an LD beam shaping and homogenizing system based on a microlens array, comprising the LD beam shaping and homogenizing system based on a microlens array as described in any one of claims 1-9, characterized in that, Including the following steps: The astigmatic beam output from the LD array light source is first incident on the fast axis pre-correction unit, where the divergence angle in the fast axis direction is compressed to match that in the slow axis direction. The beam then enters the first microlens array and is split into multiple sub-beams. Each sub-beam is collimated by the first microlens and then incident on the second microlens array. The sub-beams are superimposed and homogenized at the focal plane after passing through the second microlens array. The homogenized beam is collimated and magnified by the relay lens group and finally output as a light spot through the output coupling unit.

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