A reflective homogenizing mirror and homogenizing system for generating a flat-top rectangular light spot

Abstract

The invention discloses a reflective homogenizer mirror and a homogenizing system for generating a flat-top rectangular light spot, and belongs to the field of laser processing. The reflective homogenizer mirror comprises a mirror body and a reflective mirror surface, wherein the reflective mirror surface comprises two left and right rotating curved surface groups, and the distance f between the rotating curved surface group and the working surface is w , the vertical distance h between the rotation surface group and their respective rotation axes l and h r , the distance d between the left and right rotation axes and the central axis of the two rotation surface groups l and d r When the relationship #imgabs0# and #imgabs1# is satisfied, a quasi-uniform spot can be obtained in a quasi-uniform direction, where D l is the left half width of the incident light on the reflector, D r The right half width of the incident light on the reflective mirror surface. The edge of the light spot in the quasi-uniform direction drops steeply, which can greatly reduce the virtual light effect caused by Gaussian distribution, effectively improve the utilization rate of the edge energy of the Gaussian beam, and has a wider application range. The device of the present invention can be processed by a high-precision rotary lathe, and does not require an expensive high-precision free-form surface processing machine tool, which can reduce the processing cost.

Description

Technical Field

[0001] The present invention relates to the field of laser processing, and more specifically, to a reflective homogenizing mirror and a homogenizing system for generating a flat-top rectangular light spot. Background Art

[0002] Uniform flat-top rectangular spot is widely used in the field of laser processing. Uniform flat-top rectangular spot can achieve very precise processing effect in laser processing. For example, laser surface modification systems such as laser phase change quenching and laser cladding require a relatively uniform flat-top rectangular spot.

[0003] In the prior art, there are many methods to achieve laser beam shaping and homogenization, such as microlens array, diffractive optical element method, reflective array integrator, etc. Microlens array has high cost and has requirements on the wavelength of the light source. Moreover, since it is a transmissive optical element, it cannot be used for high-power laser processing. Diffractive optical elements can shape laser Gaussian beams into a light spot with relatively uniform energy, but diffractive optical elements need to use single-mode laser light sources and accurately know the amplitude and phase distribution of the light source. Diffractive optical elements have poor anti-disturbance characteristics and poor flexibility. In addition, as a transmissive optical element, the laser power it can withstand is limited.

[0004] At present, the homogenizing lenses in practical application are mainly reflective integrators, which are processed with copper substrates and can be designed with water cooling on the back. They can be used for high-power laser applications. Traditional reflective integrators can only achieve uniform energy distribution in one direction, and Gaussian energy distribution in another direction. The uniformity in the direction of Gaussian energy distribution is greatly affected by the light source and collimation conditions. The Gaussian edge part does not reach the processing threshold of the material, forming a virtual light, which greatly reduces the effective utilization rate of the laser. The American II-VI company has launched a reflective array integrator that can solve the homogenization problem in two directions. However, this mirror surface is a free-form mirror surface, which requires a five-axis high-precision machining machine to achieve. The equipment is very expensive, and when processing free-form surfaces, only slow knives can be used. The surface roughness of the processed surface is much worse than that of the surface processed by a high-precision rotary lathe. Therefore, it is very valuable to process a reflective homogenizing mirror with a rectangular distribution on a high-precision rotary lathe. Summary of the invention

[0005] In view of the above defects or improvement needs of the prior art, the present invention provides a reflective homogenizer and a homogenizing system for generating a quasi-flat-top rectangular light spot, which can obtain a quasi-flat-top rectangular light spot composed of two light spots, and the quasi-flat-top rectangular light spot has uniform energy distribution in a uniform direction, and the energy in a quasi-uniform direction is quasi-uniformly distributed.

[0006] A reflective homogenizer for generating a flat-top rectangular light spot, comprising: a mirror body and a reflective mirror surface, wherein the reflective mirror surface comprises two left and right rotating curved surface groups, and the distance f between the rotating curved surface group and the working surface is w , the vertical distance h between the rotation surface group and their respective rotation axes l and h r , the distance d between the left and right rotation axes and the central axis of the two rotation surface groups l and d r Satisfaction relationship: and When D l is the left half width of the incident light, D r is the right half width of the incident light.

[0007] Furthermore, the rotation surface group is composed of multiple sub-surfaces, each of which is generated by a straight line segment and / or a quadratic curve segment around a rotation axis, and the multiple straight line segments and / or quadratic curve segments of the multiple sub-surfaces are connected end to end in sequence to form a rotation mother line of the rotation surface group; the sub-surfaces divide parallel incident light into multiple parts, and use their reflection characteristics to reflect the multiple light beams into a uniform direction within a spot length and superimpose them, thereby obtaining a uniform light spot in the uniform direction.

[0008] Furthermore, the reflecting mirror surface includes two left-right symmetrical rotation surface groups, the rotation generatrix corresponding to the rotation surface groups is left-right symmetrical and the corresponding rotation axis is in the same plane as the focal plane, which can generate a flat-top rectangular light spot with uniform energy distribution in a uniform direction and a saddle-shaped energy distribution in a quasi-uniform direction.

[0009] Furthermore, the type of the sub-curved surface can be flexibly changed according to the required light spot distribution pattern.

[0010] Furthermore, the mirror body is a cylinder or an elliptical cylinder.

[0011] Furthermore, the reflective homogenizing mirror is made of a highly reflective metal material and is processed using a high-precision rotary lathe.

[0012] Furthermore, the reflective mirror surface is coated with a high-reflective film.

[0013] A reflective homogenization system for generating a flat-top rectangular light spot comprises a laser beam emitting device, a collimating parabolic mirror and the reflective homogenization mirror described above; the laser beam emitting device is used to output a laser beam, the collimating parabolic mirror is used to collimate the laser beam, and the reflective homogenization mirror is used to receive the output light of the collimating parabolic mirror and homogenize the beam into a flat-top rectangular light spot.

[0014] Furthermore, the collimating parabolic mirror is a reflective component or a transmissive component.

[0015] Furthermore, the light beam collimated by the collimating parabolic mirror is incident on the reflective homogenizing mirror in a direction parallel to the mirror body.

[0016] In summary, compared with the prior art, the technical solution conceived by the present invention can achieve the following beneficial effects:

[0017] 1. Divide the reflective mirror surface into two rotating surface groups to obtain a flat-top rectangular light spot composed of two light spots. The energy of the light spot is uniformly distributed in the uniform direction, and the energy is quasi-uniformly distributed in the quasi-uniform direction. The edge of the light spot in the quasi-uniform direction drops steeply, which can greatly reduce the virtual light effect caused by Gaussian distribution, effectively improve the utilization rate of the edge energy of the Gaussian beam, and has a wider range of applications.

[0018] 2. The reflective mirror surface is preferably divided into two symmetrical rotating surface groups. The energy distribution of the flat-top rectangular spot obtained by adjusting the relevant parameters is uniform in the uniform direction, and the energy is distributed in a saddle shape in the quasi-uniform direction, so that a more uniform temperature field distribution can be obtained.

[0019] 3. The reflective homogenizing mirror of the present invention is preferably processed by a high-precision rotary lathe, which does not require an expensive high-precision free-form surface processing machine tool, thereby reducing processing costs and facilitating processing.

[0020] 4. The reflective mirror surface of the reflective homogenizing mirror of the present invention is preferably coated with a high-reflective film to improve the smoothness and reflectivity of the reflective mirror surface.

[0021] 5. The reflective mirror surface of the reflective homogenizer of the present invention preferably adopts reflective shaping, and a water cooling structure is added to the mirror body, which can be used for processing applications of kilowatt and ten-thousand-watt high-power lasers, greatly expanding the application field.

[0022] 6. The left-right positional relationship of the two rotation axes of the reflective homogenizer of the present invention is the same as that of the rotation surface group. The angle between the two rotation surface groups is greater than 180°, which is convenient for processing a single rotation surface group without damaging adjacent rotation surface groups.

[0023] In general, through the above technical scheme conceived by the present invention, the required flat-top rectangular light spot can be flexibly designed, the processing cost is low, the installation steps are simple, the operation is convenient, and large-scale production can be achieved; it has a good match with the traditional ordinary integrator mirror, which is convenient for replacement and updating in the original system. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic structural diagram of a reflective homogenizing mirror provided in the first embodiment of the present invention.

[0025] Figure 2It is a principle diagram of a reflective homogenizing mirror provided in the first embodiment of the present invention.

[0026] Figure 3 It is a principle side view of the reflective homogenizing mirror provided in the first embodiment of the present invention.

[0027] Figure 4 It is a principle oblique view of the reflective homogenizing mirror provided in the first embodiment of the present invention.

[0028] Figure 5 It is a principle diagram of the reflective homogenizing mirror provided by the present invention in the uniform direction.

[0029] Figure 6 It is a schematic diagram of a reflective homogenization system provided in the first embodiment of the present invention.

[0030] Figure 7 It is a simulation diagram of a quasi-flat-top rectangular light spot generated by the first embodiment of the present invention and a schematic diagram of energy distribution simulation in a uniform direction and a quasi-uniform direction.

[0031] Figure 8 It is a schematic diagram of a reflective homogenizing mirror provided in the second embodiment of the present invention.

[0032] Fig. 9 It is a principle side view of a reflective homogenizing mirror provided in the second embodiment of the present invention.

[0033] Fig.10 It is a simulation diagram of a quasi-flat-top rectangular light spot generated by the second embodiment of the present invention and a schematic diagram of the simulation of energy distribution in a uniform direction and a quasi-uniform direction.

[0034] Fig.11 It is a simulation diagram of a quasi-flat-top rectangular light spot generated by the third embodiment of the present invention and a schematic diagram of energy distribution simulation in a uniform direction and a quasi-uniform direction.

[0035] Fig.12 4 is a schematic diagram of a reflective homogenizing mirror according to a fourth embodiment of the present invention.

[0036] In all the drawings, the same figure marks are used to represent the same elements or structures, where: 1-laser beam emitting device 2-reflective homogenizing mirror 3-reflective collimating parabolic mirror 4-working surface 6-focal plane 21-mirror body 22-reflecting mirror surface 23-rotating surface group 24-rotation axis a-left light spot b-right light spot c-central axis of the two rotating surface groups l-spot length in the uniform direction. DETAILED DESCRIPTION

[0037] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0038] First, the uniform direction and quasi-uniform direction of the light spot of the present invention are described: the direction parallel to the incident light is the uniform direction of the generated light spot; the direction perpendicular to the incident light is the quasi-uniform direction of the generated light spot.

[0039] The present invention provides a reflective homogenizing mirror for generating a quasi-flat-top rectangular light spot, which generates a quasi-flat-top rectangular light spot formed by combining two light spots, and its energy distribution is as follows: the energy distribution is uniform in a uniform direction, and the energy distribution in the quasi-uniform direction is a quasi-flat-top rectangular light spot that is approximately rectangular, such as convex on the outside and concave in the middle or concave on the outside and convex in the middle. This energy distribution is called a quasi-uniform distribution, and the edge of the light spot of this quasi-uniform distribution drops steeply.

[0040] Figure 1-Figure 4 , a reflective homogenizer for generating a flat-top rectangular spot provided by the first embodiment of the present invention. The reflective homogenizer includes: a mirror body 21 and a reflective mirror surface 22. The mirror body 21 is a cylinder, and the reflective mirror surface 22 is a concave mirror. It includes two rotation surface groups 23, and the rotation generatrix, rotation radius, and maximum width of the two rotation surface groups are different. The two rotation surface groups 23 are composed of 12 sub-surfaces; each sub-surface is generated by a parabola segment around a rotation axis 24, and the generatrix of all sub-surfaces constituting each rotation surface group 23 is connected in end-to-end order to form the rotation generatrix of the rotation surface group 23. Figure 5 , the incident light beam is incident on each sub-surface in the uniform direction, and the light beam incident on each sub-surface is reflected to the uniform direction within the light spot length l by using the reflection characteristics of the sub-surface, so that the energy of the generated light spot in this direction is uniform. The more sub-surfaces there are, the more uniform the light spot in this direction is, wherein the light spot length l in the uniform direction is the required light spot length initially defined; in the quasi-uniform direction, when the distance f between the rotating surface group 23 and the working surface 4 is w , the vertical distance h between the center point of the rotation surface group 23 and the respective rotation axis 24 l and h r , the distance d between the left and right rotation axes and the central axis c of the two rotation surface groups l and d r Satisfaction relationship: and When the above-mentioned quasi-uniform spot can be obtained in the quasi-uniform direction, D l is the left half width of the incident light, D ris the right half width of the incident light. That is, when the incident light is incident on the left rotating surface group, the left rotating surface group reflects the light beam to the working surface 4, and will not exceed the right side of the right spot b; when the incident light is incident on the right rotating surface group, the right rotating surface group reflects the light beam to the working surface 4, and will not exceed the left side of the left spot a. The length of the light spot obtained in the quasi-uniform direction

[0041] like Figure 6 During use, the laser beam emitted from the laser beam emitting device 1 is collimated by the reflective collimating parabola 3, and the reflected collimated laser beam is a parallel Gaussian beam. After collimation, the incident direction of the beam must be parallel to the direction of the mirror body 21, and then incident on the reflective homogenizing mirror 2; the sub-surface of the reflective homogenizing mirror 2 receives the outgoing light of the reflective collimating parabola 3 and reflects the beam to the working surface 4, and the side light path is roughly in the shape of two funnels, forming a flat-top rectangular light spot formed by superimposing two light spots on the working surface 4, and the generated light spot has uniform energy distribution in the uniform direction, and the energy in the quasi-uniform direction is quasi-uniformly distributed. Among them, the reflective collimating parabola 3 can also be a transmissive component.

[0042] Specifically, the reflective homogenizer 2 is a copper-based column with a radius of 15 mm, and is 400 mm away from the working surface 4. The maximum width of the left rotating surface group is 18 mm, and the maximum width of the right rotating surface group is 12 mm. The two rotating axes are 3.4 mm apart, and the rotation radius is 340 mm. The left and right rotating surface groups are divided into 12 sub-surfaces. The width of the spot is initially set to 4 mm. After reflection from the sub-surfaces, the spot size formed by the superposition of two quasi-flat-top rectangular spots obtained at the working surface 4 is 4 mm*4 mm, and the superposition length is 0.6 mm. The energy is manifested as uniform energy distribution in the uniform direction, and in the quasi-uniform direction, it is manifested as the superposition of two asymmetric semi-Gaussian homogenized spots, that is, the energy of the left spot is higher than that of the right spot, and the middle part is a quasi-flat-top rectangular spot that is concave inward. The generated quasi-flat-top rectangular spot simulation diagram and the energy distribution simulation schematic diagram in the uniform direction and the quasi-uniform direction are shown as follows. Figure 7 This type of spot can be used for laser surface modification such as laser phase change quenching and laser cladding.

[0043] like Figure 8 , Fig. 9As shown, the reflective homogenizer of the second embodiment of the present invention is different from the first embodiment in that the reflective homogenizer 2 is symmetrical between two left and right rotating surface groups, the rotating generatrixes corresponding to the two rotating surface groups 23 are symmetrical on the left and right, and the corresponding two rotating axes 24 are in the same focal plane 6. After reflection by the sub-surface, the spot size of the two quasi-flat-top rectangular spots superimposed on the working surface 4 is 4mm*4mm, and the superposition length is 0.6mm. The energy is manifested as uniform energy distribution in the uniform direction, and in the quasi-uniform direction, it is manifested as the superposition of two semi-Gaussian homogenized spots, that is, a quasi-flat-top rectangular spot that is slightly concave in the middle and slightly convex on both sides, similar to a saddle-shaped flat-top rectangular spot. The generated quasi-flat-top rectangular spot simulation diagram and the schematic diagram of energy distribution simulation in the uniform direction and the quasi-uniform direction are shown in FIG. Fig.10 As shown in the figure, the temperature field of the flat-top rectangular light spot generated in this way is more uniform. Compared with the traditional Gaussian distribution of the light spot, the temperature field distribution is still a Gaussian mode, and the temperature field of the uniform light spot is a distribution mode that is high in the middle and decreases rapidly to both sides. The temperature field of the light spot with a saddle-shaped energy distribution is more uniform.

[0044] like Fig.11 The reflective homogenizing mirror of the third embodiment of the present invention is different from that of the second embodiment in that the positional relationship between the two rotation axes is adjusted so that the two light spots overlap, thereby generating a light spot that is concave on both sides, convex in the middle and has steep edges.

[0045] like Fig.12 The reflective homogenizing mirror of the fourth embodiment of the present invention is different from the first three embodiments in that a transmission collimating mirror is used in the homogenizing system and the reflective mirror is placed at an angle, which can also generate the light spot described in the previous embodiments.

[0046] It should be noted that the shape of the reflective surface of the reflective homogenizer 2 is different, and the shape of the flat-top rectangular light spot is also different; the type of the above-mentioned reflective homogenizer 2 can be flexibly replaced according to the required light spot distribution mode. The reflective homogenizer provided by the present invention is made of highly reflective metal material and processed by a high-precision rotary lathe; the reflective mirror surface is preferably plated with a high-reflective film, which can improve the smoothness and reflectivity of the reflective mirror surface; the mirror body can also be an elliptical cylinder and placed at an angle; the mirror body can be added with a water cooling structure to cool the reflective homogenizer mirror. The use of a reflective mirror surface can be conveniently used for the processing of kilowatts and ten-thousand-watt high-power lasers, greatly expanding the application field.

[0047] In addition, the sub-surface in this embodiment can be replaced by a rotation generatrix composed of straight line segments or straight line segments and quadratic curve segments generated around the rotation axis.

[0048] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A reflective homogenizer for generating a flat-top rectangular light spot, comprising: A mirror body (21) and a reflective mirror surface (22), wherein the reflective mirror surface (22) comprises two left and right rotating curved surface groups (23), and the distance f between the rotating curved surface group (23) and the working surface (4) is w , the vertical distance h between the center point of the rotation surface group (23) and the respective rotation axis (24) l and h r , the distance d between the left and right rotation axes (24) and the central axis c of the two rotation surface groups (23) l and d r Satisfaction relationship: and When , a quasi-uniform spot with a steeply decreasing edge can be obtained in the quasi-uniform direction, where D l is the left half width of the incident light, D r is the right half width of the incident light.

2. The reflective homogenizer for generating a flat-top rectangular spot according to claim 1, characterized in that: The rotational surface group (23) is composed of a plurality of sub-surfaces, each of which is generated by a straight line segment and / or a quadratic curve segment around a rotation axis (24), and the plurality of straight line segments and / or quadratic curve segments of the plurality of sub-surfaces are connected end to end in sequence to form a rotation generatrix of the rotational surface group (23); the sub-surfaces divide parallel incident light into a plurality of portions, and utilize their reflection characteristics to reflect the plurality of light beams into a uniform direction within a light spot length l for superposition, thereby obtaining a uniform light spot in the uniform direction.

3. The reflective homogenizer for generating a flat-top rectangular spot according to claim 2, characterized in that: The reflective mirror surface (22) comprises two left-right symmetrical rotational curved surface groups (23), the rotational generatrix corresponding to the rotational curved surface groups (23) being left-right symmetrical and the corresponding rotational axis (24) being in the same plane as the focal plane (6), and can generate a flat-top rectangular light spot with uniform energy distribution in a uniform direction, a saddle-shaped energy distribution in a quasi-uniform direction and a steeply descending edge.

4. The reflective homogenizer for generating a flat-top rectangular spot according to claim 3, characterized in that: The type of the sub-surface can be flexibly changed according to the required spot distribution pattern.

5. The reflective homogenizer for generating a flat-top rectangular spot according to claim 1, characterized in that: The mirror body (21) is a cylinder or an elliptical cylinder.

6. A reflective homogenizer for generating a flat-top rectangular spot according to any one of claims 1 to 5, characterized in that: The reflective homogenizing mirror is made of a highly reflective metal material and is processed using a high-precision rotary lathe.

7. The reflective homogenizer for generating a flat-top rectangular spot according to claim 6, characterized in that: The reflective mirror surface (22) is coated with a high-reflective film.

8. A reflective homogenization system for generating a quasi-flat-top rectangular light spot, comprising a laser beam emitting device, a collimating parabolic mirror and a reflective homogenization mirror as claimed in any one of claims 1 to 7; the laser beam emitting device is used to output a laser beam, the collimating parabolic mirror is used to collimate the laser beam, and the reflective homogenization mirror is used to receive the output light of the collimating parabolic mirror and homogenize the beam into a quasi-flat-top rectangular light spot.

9. A reflective homogenization system for generating a flat-top rectangular light spot according to claim 8, characterized in that: The collimating parabolic mirror is a reflective component or a transmissive component.

10. A reflective homogenization system for generating a flat-top rectangular light spot according to claim 9, characterized in that: The light beam collimated by the collimating parabolic mirror is incident on the reflective homogenizing mirror in a direction parallel to the mirror body (21).

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