An optical system for outputting a circular symmetric light spot with a single mirror

Abstract

The application discloses an optical system for outputting a circularly-symmetrical light spot by a single mirror. The optical system comprises, in sequence along an optical path, a light source and a shaping and focusing unit. The shaping and focusing unit adopts a homogenized three-dimensional circularly-symmetrical light spot reflection single mirror, shapes an incident Gaussian light beam, changes a light spot distribution mode, and focuses the light spot on a preset position of a working surface to form a target three-dimensional circularly-symmetrical light spot. The phase of the reflection surface is determined by the following method: based on a preset collimation focal length, a preset focusing focal length, an incident light ray of the incident Gaussian light beam and an exit light ray corresponding to the target three-dimensional circularly-symmetrical light spot, a curved surface equation of a basic ellipsoidal mirror surface is determined, then according to an energy distribution corresponding to the target three-dimensional circularly-symmetrical light spot, a mirror surface shaping region and corresponding divergence angles are determined, and different mirror surface shaping regions are superposed with corresponding transverse offset phases and longitudinal offset phases. The output of the circularly-symmetrical light spot with high uniformity, adjustable intensity and size is realized, and the requirement of different scenes in actual processing is met.

Description

Technical Field

[0001] This invention belongs to the field of laser processing, and more specifically, relates to an optical system that outputs a circularly symmetrical light spot from a single mirror. Background Technology

[0002] Conventional Gaussian focused laser beams, with their high energy at the center and low energy at the edges, are prone to causing defects such as overheating, porosity, and spatter at the center, as well as insufficient melting and incomplete processing at the edges during laser processing. For example, in laser glass thin-film technology, the energy in the center region of a Gaussian laser processing is much higher than the ablation threshold, which can damage the substrate material. Conversely, the energy at the falling edge of a Gaussian distribution is lower than the ablation threshold, which can generate thermal effects and damage the thin film structure. An intensity-adjustable circularly symmetric laser beam can significantly improve this energy matching with the ablation threshold. By using this ablation threshold, excess energy above the threshold and excess energy in the falling edge can be reduced, avoiding potential damage to the substrate and adjacent areas below the laser scribing line, thus greatly improving processing efficiency. The rectangular footprint generated by a flat-top laser can produce straight walls with very little overlap, thereby increasing the processing speed of laser micromachining.

[0003] Currently, there are various methods for generating intensity-tunable circularly symmetric laser spots in the field of laser processing. However, some methods are not suitable for high-power laser processing scenarios, such as spatial light modulators. At present, intensity-tunable circularly symmetric laser spot solutions suitable for high-power processing scenarios can be divided into two categories: one is based on flat-top fiber lasers with special fiber structures, which can directly output a ring-shaped laser spot; the other is based on external optical path shaping using optical elements, which obtains an intensity-tunable circularly symmetric laser spot by shaping the Gaussian beam output from a general laser.

[0004] Coherent has introduced flat-top laser products that can achieve high-uniformity flat-top laser output. However, these lasers all have the following drawbacks: First, they are expensive; the price of fiber lasers that can output intensity-tunable circularly symmetrical beams is much higher than that of ordinary fiber lasers. Second, their application scenarios are limited; the flat-top beam shaping method based on the special structure of optical fibers is only applicable to fiber lasers, but there are still many scenarios in laser processing where it is not suitable to use fiber lasers as processing light sources. Third, the beam size is limited; it can only output a preset intensity-tunable circularly symmetrical beam size and cannot adjust other types of intensity-tunable circularly symmetrical beam modes, such as concave beams.

[0005] In external optical path shaping based on beam-shaping elements, various beam-shaping elements are used, which can be roughly divided into two categories: The first category is transmissive beam-shaping elements, such as microlenses, beam-shaping DOEs, and many other transmissive optical beam-shaping elements with beam-shaping functions, such as Edmund's AdlOpticaπShaper flat-top beam shaper. However, current transmissive optical beam-shaping elements have the following drawbacks: a low damage threshold, therefore, in ultra-high power laser processing, the stability and lifespan of transmissive optical elements are insufficient; many transmissive optical beam-shaping elements have complex mirror shapes, making them difficult and costly to manufacture. The second category is reflective beam-shaping elements, such as aspherical mirrors. Compared with transmissive optical beam-shaping elements, reflective beam-shaping elements have a higher damage threshold because the main material can be metal and a built-in water-cooling channel can be incorporated, and the manufacturing technology is also more mature. However, the current disadvantages of intensity-adjustable circular symmetric spot shaping optical path based on reflective shaping elements are: the mirror shaping effect is singular, the processing precision requirements for complex functional mirrors are high, and the processing difficulty is great.

[0006] In summary, one approach to achieving extremely high-power flat-top beam shaping is to simplify the optical path as much as possible based on reflective shaping elements, thereby satisfying diverse shaping modes while reducing manufacturing complexity and improving stability and applicability. Summary of the Invention

[0007] In view of the shortcomings of related technologies, the purpose of this invention is to provide an optical system that outputs a circularly symmetrical light spot from a single mirror, aiming to solve the problem of how to simplify the optical path as much as possible, meet the diverse shaping modes while reducing the processing complexity, and improving stability and applicability.

[0008] To achieve the above objectives, the present invention provides an optical system for outputting a circularly symmetrical light spot using a single mirror, comprising: a light source and a shaping and focusing unit arranged sequentially along the optical path;

[0009] The light source is used to generate a Gaussian beam;

[0010] The shaping and focusing unit employs a homogenized three-dimensional circularly symmetrical beam reflector to shape the incident Gaussian beam, change the beam distribution pattern, and focus it at a preset position on the working surface to form a target three-dimensional circularly symmetrical beam with adjustable size; different beam portions of the three-dimensional circularly symmetrical beam are located on the same / different planes.

[0011] The phase of the reflecting surface of the shaping and focusing unit is determined in the following way: the surface equation of the basic ellipsoidal mirror is determined based on the collimating focal length, focusing focal length, incident ray of the Gaussian beam, and outgoing ray corresponding to the target three-dimensional circularly symmetrical spot reflecting mirror. Then, the mirror shaping area and the corresponding divergence angle are determined according to the energy distribution corresponding to the target three-dimensional circularly symmetrical spot. The corresponding lateral offset phase and longitudinal offset phase are superimposed on different mirror shaping areas.

[0012] Optionally, the shaping and focusing unit is used to change the distribution of the target three-dimensional circularly symmetrical spot by adjusting the lateral offset phase. The target three-dimensional circularly symmetrical spot includes: a flat-top spot, a concave ring spot, and a convex ring spot.

[0013] Optionally, the shaping and focusing unit is used to change the focal plane position of different spot portions in the target three-dimensional circularly symmetrical spot by adjusting the longitudinal offset phase.

[0014] Optionally, the three-dimensional circularly symmetrical light spot reflecting mirror is a rotating ellipsoidal mirror; the rotating ellipsoidal mirror includes a focal point in the incident direction and a focal point in the exit direction, denoted as the front focal point and the rear focal point, respectively; the focal plane corresponding to the front focal point is denoted as the front focal plane, and the light source is located on the front focal plane; the focal plane corresponding to the rear focal point is denoted as the rear focal plane, and the working surface is the rear focal plane; the distance from the front focal point to the center point of the reflecting surface is denoted as the collimating focal length; the distance from the center point of the rear focal plane to the center point of the reflecting surface is denoted as the focusing focal length;

[0015] Based on the principle of equal optical path in light propagation, an ellipsoidal phase and a gradient phase are introduced on the reflecting surface. The ellipsoidal phase is used to focus the incident light rays at a preset position on the working surface after reflection, and the gradient phase is used to shape the incident Gaussian beam, change the spot distribution mode, and obtain a target three-dimensional circularly symmetrical spot with uniform intensity distribution.

[0016] The energy of the input beam at point r on the reflecting mirror surface corresponds to a ring of radius R on the working surface. The correspondence between the ring of radius R on the target's three-dimensional circularly symmetric spot and the ring of radius r on the incident Gaussian beam is as follows:

[0017]

[0018] Where F1 is the preset collimation focal length; F2 is the preset focusing focal length; I s (r, θ) represents the polar coordinate distribution of the incident circular beam intensity, which, for a Gaussian beam, satisfies a two-dimensional Gaussian distribution; I t (r,θ) represents the polar coordinate distribution of the light intensity of the target flat-top circular light spot.

[0019] Optionally, the mirror-shaping area of ​​the reflecting surface is determined by the following method: the incident light is divided into cones, and the mirror is divided into different shaping areas according to the energy distribution of the target three-dimensional circular symmetrical light spot. The divergence angle range of each area is determined by the energy ratio between the different shaping areas.

[0020] Optionally, the boundaries of different regions of the reflective surface of the shaping and focusing unit are homogenized to make the mirror surface smooth and without grooves; the mirror surface of the shaping and focusing unit is homogenized in the following way: radial lines are drawn from the center of the mirror surface along the radius, and the phase difference value is subtracted from the processing points located in different shaping regions on the same line.

[0021] Optionally, the light source is a laser.

[0022] Optionally, the reflective surface of the shaping and focusing unit is a non-rotationally symmetric freeform surface.

[0023] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following beneficial effects:

[0024] 1. This invention provides an optical system for outputting a circularly symmetrical light spot using a single mirror. The shaping and focusing unit employs a homogenized three-dimensional circularly symmetrical light spot reflecting single mirror. Based on the collimating focal length, focusing focal length, and light spot distribution pattern of the target light field of the three-dimensional circularly symmetrical light spot reflecting single mirror, a mapping relationship between the energy distribution of the incident light field and the target light field is established. Combining the principle of equal optical path length and the principle of energy conservation, the surface equation of the reflecting surface of the homogenized three-dimensional circularly symmetrical light spot reflecting single mirror corresponding to the target three-dimensional circularly symmetrical light spot with adjustable intensity is constructed. This invention can simultaneously perform beam collimation, shaping, and focusing functions with a single mirror, obtaining an intensity-adjustable circularly symmetrical light spot from a laser source without the need for other optical components. It can achieve the output of a highly uniform and intensity-adjustable circularly symmetrical light spot with fewer optical components and a simplified optical path structure. The size of the circularly symmetrical light spot is arbitrarily adjustable, and different light spot parts are located on the same / different planes, adapting to the needs of different scenarios in actual processing.

[0025] 2. This invention provides an optical system for outputting a circularly symmetrical light spot using a single mirror. The shaping and focusing unit employs a homogenized three-dimensional circularly symmetrical light spot reflecting mirror. Homogenization of the reflecting mirror surface solves the continuity problem of the entire mirror surface when multiple curved surfaces are combined, reducing the difficulty of processing complex surface shapes. Furthermore, this invention offers a variety of light spot shaping modes, not limited to highly uniform and intensity-adjustable circularly symmetrical light spots, but including more complex programmable intensity distribution circularly symmetrical light spots, such as concave annular light spots and convex annular light spots; and the energy proportions of each part of the concave annular light spot and the convex annular light spot are adjustable.

[0026] 3. This invention provides an optical system for outputting a circularly symmetrical light spot using a single mirror. The optical system is constructed with fewer optical components, making it easier to adjust, more stable, and with a higher damage threshold. The fewer optical components required to output a circularly symmetrical light spot of different sizes and intensities reduces the accumulation of processing or assembly errors of each component, enabling the light spot shaping system in this invention to achieve a more stable and accurate output. At the same time, it also reduces the optical path volume, has a more streamlined optical path structure, and has stronger anti-interference capabilities.

[0027] 4. This invention provides an optical system that outputs a circularly symmetrical light spot from a single mirror. The proposed method for designing the mirror phase can design and control the transmission characteristics and defocused light field distribution of the shaped beam, which is beneficial for meeting different application requirements. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the structure of an optical system that outputs a flat-top light spot using a single mirror, according to an embodiment of the present invention.

[0029] Figure 2 This is a schematic diagram showing the change in the position of the light spot when the longitudinal offset phase of the shaping and focusing unit provided in the embodiment of the present invention changes;

[0030] Figure 3 This is a schematic diagram of the shaping and focusing unit provided in an embodiment of the present invention;

[0031] Figure 4 This is a side view of the reflecting mirror surface of the shaping and focusing unit provided in an embodiment of the present invention;

[0032] Figure 5 This is a front view of the reflecting mirror surface of the shaping and focusing unit provided in an embodiment of the present invention;

[0033] Figure 6 This is a schematic diagram of the structure of an optical system for outputting a flat-top light spot using a single mirror, provided in Embodiments 1 and 3 of the present invention;

[0034] Figure 7 This is a schematic diagram of the target spot energy distribution of an optical system with a single-mirror output flat-top spot provided in Embodiment 1 of the present invention;

[0035] Figure 8 This is a schematic diagram of the structure of an optical system for outputting a flat-top light spot using a single mirror, provided in Embodiments 2 and 4 of the present invention;

[0036] Figure 9 This is a schematic diagram of the target spot energy distribution of an optical system with a single-mirror output flat-top spot provided in Embodiment 2 of the present invention;

[0037] Figure 10This is a schematic diagram of the target spot energy distribution of an optical system with a single-mirror output flat-top spot provided in Embodiment 3 of the present invention;

[0038] Figure 11 This is a schematic diagram of the target spot energy distribution of an optical system that outputs a flat-top light spot using a single mirror, provided in Embodiment 4 of the present invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0040] The following description, in conjunction with a preferred embodiment, illustrates the content involved in the above embodiments.

[0041] like Figure 1 As shown, an optical system for outputting a flat-top light spot with a single mirror includes: a light source 1 and a shaping and focusing unit 2, which are placed sequentially along the optical path.

[0042] The light source 1 is used to generate a Gaussian beam 4;

[0043] The shaping and focusing unit 2 uses a homogenized three-dimensional circularly symmetrical spot reflecting mirror to shape the incident Gaussian beam 4, change the spot distribution pattern, and focus it at a preset position on the working surface 3 to form a target three-dimensional circularly symmetrical spot with adjustable size; different spot portions of the three-dimensional circularly symmetrical spot are located on the same / different planes.

[0044] The phase of the reflecting surface of the shaping and focusing unit 2 is determined in the following way: the surface equation of the basic ellipsoidal mirror is determined based on the collimating focal length, focusing focal length, incident ray of the Gaussian beam, and outgoing ray corresponding to the target three-dimensional circularly symmetrical spot reflecting mirror. Then, the mirror shaping area and the corresponding divergence angle are determined according to the energy distribution corresponding to the target three-dimensional circularly symmetrical spot. The corresponding lateral offset phase and longitudinal offset phase are superimposed on different mirror shaping areas.

[0045] This invention provides an optical system for outputting a flat-top light spot using a single mirror. This system is a simple, single-mirror, intensity-adjustable, circularly symmetrical light spot optical system. The core of this system is a homogenized three-dimensional circularly symmetrical light spot reflecting mirror used as the shaping and focusing unit. This mirror collimates, shapes, and focuses the input Gaussian beam, and its surface shape is calculated based on given parameters. This embodiment provides an optical system that, while achieving an adjustable-intensity output three-dimensional circularly symmetrical light spot, realizes collimation, shaping, and focusing functions through a single mirror, reducing the number of optical components. The discontinuities in the curved surface of the homogenized three-dimensional circularly symmetrical light spot reflecting mirror are homogenized, resulting in a smooth, groove-free surface that reduces manufacturing difficulty and allows it to withstand high-power lasers. The intensity of the target light spot can be adjusted to achieve an adjustable distribution of energy in the circularly symmetrical light spot. Without affecting the focal plane light field distribution, the defocused light field can be controlled, enabling multiple uses for the same beam and optimizing processing effects, thus solving practical processing problems.

[0046] With the shape of the reflecting surface completely determined, the optical system has a definite incident direction and an exit direction; a three-dimensional circularly symmetrical reflective single mirror includes a focal point in the incident direction and a focal point in the exit direction, denoted as the front focal point and the rear focal point, respectively; the focal plane corresponding to the front focal point is denoted as the front focal plane, and the light source is located on the front focal plane; the focal plane corresponding to the rear focal point is denoted as the rear focal plane, and the working surface is the rear focal plane; the distance from the front focal point to the center point of the reflecting surface is denoted as the collimating focal length; the distance from the center point of the rear focal plane to the center point of the reflecting surface is denoted as the focusing focal length.

[0047] Since the shaping and focusing unit 2 shapes and focuses the Gaussian beam to form a target three-dimensional circularly symmetrical spot, the phase of the three-dimensional circularly symmetrical spot reflecting mirror exhibits a non-uniform gradient, i.e., the shape of the reflecting surface is different, depending on the shape and energy distribution of the target three-dimensional circularly symmetrical spot. The reflecting surface of the intensity-adjustable three-dimensional circularly symmetrical spot reflecting mirror is a calculated curved surface, which can be determined by solving a solution using a preset collimating focal length, a preset focusing focal length, and a preset spot energy distribution of the target light field on the focal plane as conditions. Its shape is a non-rotationally symmetric free-form surface. Adjusting the lateral phase shift of the reflecting surface of the shaping and focusing unit 2 changes the distribution of the circularly symmetrical spot obtained after shaping. The circularly symmetrical spots include: flat-top spots, concave-ring spots, and convex-ring spots.

[0048] like Figure 1 As shown, the shaping and focusing unit 2 shapes and focuses the Gaussian beam 4 emitted by the light source 1 to obtain a target intensity adjustable circular symmetrical spot of a defined size on the back focal plane. The incident light ray that makes up the Gaussian beam 4 is the Gaussian beam emitted by the light source 1 located at the front focal point. For example, the light source 1 is a laser.

[0049] The phase of the reflecting surface of the shaping and focusing unit 2 is determined in the following way: based on the collimating focal length, focusing focal length, incident ray of the incident Gaussian beam and the preset spot intensity distribution of the preset target light field, and based on the point-to-point ray mapping relationship of light propagation, a non-uniform gradient phase is set on the reflecting mirror surface. According to the principle of energy conservation, the incident rays at different positions on the mirror surface correspond to the positions of the target light spot with the same energy, and the surface equation of the reflecting surface shape corresponding to the target three-dimensional circularly symmetric light spot with adjustable intensity is constructed; wherein, the spot distribution mode of the target light field corresponds to the desired three-dimensional circularly symmetric light spot with adjustable intensity.

[0050] Specifically, the mapping relationship between the incident light field and the target light field energy distribution is determined by dividing the incident light field into multiple parts according to the energy ratio requirement of the target intensity adjustable circular symmetrical light spot, and mapping the energy of each part to the corresponding position on the back focal plane. Figure 1 In the middle, the narrow light ring 5 on the reflective surface of the shaping and focusing unit 2 corresponds to the narrow light ring 6 on the back focal plane 7 (working surface).

[0051] The energy mapping relationship between the incident light field and the target light field is determined based on conditions such as the energy distribution of the incident light field and the energy distribution of the target light field. Its meaning is as follows: The incident light field is divided into multiple narrow circular rings, such as… Figure 1 The middle ring 5 divides the target light field into multiple narrow rings, such as Figure 1 The energy of each part of the incident light field is mapped to a certain part of the target light field. That is, the light rays in that part of the incident light field will reach the corresponding part of the target light field after passing through the optical path. This energy correspondence is the energy mapping relationship between the incident light field and the target light field. The specific manifestation of the above mapping relationship in the shape of the reflecting surface is as follows: the reflecting surface is based on an ellipsoidal concave surface. The light emitted from the point source is focused into a small spot. Then, a corresponding gradient phase is added at various points on the concave surface, so that each part of the emitted light from the source is deflected to the target radius of the back focal plane while maintaining energy correspondence. The light beam incident on the reflecting surface can therefore be regarded as being divided into multiple parts. The light beams incident on different positions on the mirror surface are respectively shaped into a part corresponding to the intensity-adjustable circularly symmetrical light spot. All parts together constitute the intensity-adjustable target three-dimensional circularly symmetrical light spot.

[0052] It should be noted that customizing the reflective surface shape and replacing different mirror shapes with three-dimensional circularly symmetrical spot reflective single mirrors can achieve the following adjustment effects: adjustable collimation focal length and focusing focal length; adjustable spot distribution pattern on the back focal plane within the range of the target three-dimensional circularly symmetrical spot with adjustable intensity; and adjustable spot size and relative energy density of the target three-dimensional circularly symmetrical spot. Specifically, adjusting the lateral phase shift changes the light intensity distribution of the target three-dimensional circularly symmetrical spot, and adjusting the longitudinal phase shift changes the focal plane position of different spot portions within the target three-dimensional circularly symmetrical spot.

[0053] Furthermore, such as Figure 2 As shown, the focal plane where the spot was located before the longitudinal offset phase was adjusted is called the old target, and the focal plane where the spot was located after the adjustment is called the new target.

[0054] And Δθ=θ1-θ2;

[0055] Where l is the distance from a point on the mirror to the center, F2 is the focusing distance, d is the longitudinal offset distance, θ1 is the angle between a point on the mirror and the new target and the axis, θ2 is the angle between a point on the mirror and the old target and the axis, and Δθ is the difference between the two angles.

[0056] From the reflection relationship, we can know Finally, the longitudinal offset phase f(l) at point l can be obtained.

[0057] Furthermore, the reflecting surface mirror segmentation method of the shaping and focusing unit 2: by segmenting the point light source with a divergence angle of θ0, the energy proportion of different parts is determined. For example... Figure 3 As shown, a cone with a divergence angle of θ0 emitted from a point light source will form a light gray region S0 on the reflecting mirror surface, and a cone with a divergence angle of θ1 emitted from a point light source will form a dark gray region S1 and its boundary L on the reflecting mirror surface. S0-S1 also becomes a light gray region that is approximately circular. Superimposing more shaping phases on the mirror surface will result in a higher energy ratio and a corresponding circular region.

[0058] like Figure 3 As shown in the figure, the dark gray area is the illumination area S1 of the light source with an energy percentage of dot_part. The dark gray and light gray areas together constitute the total illumination area S0 of the point light source. The radius of the light source divergence angle on the reflecting surface is F1*tanθ0, which is the size of the light gray area S0; the radius of the boundary divergence angle on the reflecting surface is F1*tanθ1, which is the size of the dark gray area S1.

[0059] Given the total divergence angle θ0 and the energy percentage (dot_part) of the dark gray region S1, according to the formula:

[0060]

[0061] Therefore, the boundary divergence angle θ1 to be determined is:

[0062]

[0063] For different energy regions, the phase is calculated based on the surface equation; the phase is the same for the same energy region.

[0064] Furthermore, the mirror design of the reflecting surface of the shaping and focusing unit 2, such as... Figure 4In the schematic diagram of the mirror shown, the curve equation of the focusing mirror can be uniquely determined based on the distance F1 from the light source to the mirror, the distance F2 from the target three-dimensional circular symmetrical spot to the mirror, and the angle α between the incident ray and the outgoing ray. That is, the focusing mirror can be designed according to the application requirements.

[0065] According to the following formula:

[0066]

[0067]

[0068]

[0069]

[0070] Where F1 is the collimation distance, F2 is the focusing distance, α is the angle between the incident and outgoing rays, h1 is the distance from the center of the mirror to the line connecting the light source and the target, l1 is the distance from the light source to the horizontal line at the center of the mirror, l2 is the distance from the target to the horizontal line at the center of the mirror, and b 2 Here are the parameters of the ellipsoid equation, and β is the angle between the central tangent of the mirror and the line connecting the light source and the target.

[0071] The final equation of the ellipsoid can be obtained as follows:

[0072]

[0073] By changing the angle α between the incident and outgoing rays, the fundamental equation of the ellipsoid also changes.

[0074] Furthermore, the reflective surface of the shaping and focusing unit 2 is homogenized. Figure 5 In the schematic diagram of the mirror surface shown, when different phases are superimposed on the dark gray region S1 and the light gray region S0-S1, a height difference L at the boundary between the different regions will occur. This height difference varies unevenly with the angle, resulting in scratches in the center of the final processed mirror surface. This defect is exacerbated when there are many partitions in the mirror surface, severely affecting the shaping effect of the reflector and reducing its power threshold. A method for optimizing the boundary height difference of the reflector surface is proposed, such as... Figure 5 As shown, 1000 radial lines are drawn from the center of the mirror along the radius. Figure 5 The diagram illustrates one of the regions, R1. R1 intersects the boundary L at point D2. Point D1 of region S1 lies on R1, and point D3 of region S0-S1 lies on R1. The equation for region S1 is H1, and the equation for region S0-S1 is H2. The height of the two region boundaries on the radiation line R1 is...

[0075] Δ(R1) = H2(D2) - H1(D2)

[0076] Therefore, the height of points within region S1 remains unchanged, still H1(D1), and the height of points within the S0-S1 region minus the boundary height difference, i.e., H2(D3) - Δ(R1), achieves mirror homogenization on R1. This operation is performed on all 1000 radiation lines, ultimately achieving homogenization of the entire mirror surface. Even when the mirror surface has more than two sections, homogenization can still be performed using this method without affecting the mirror's optical performance.

[0077] This invention provides an optical system for outputting a circularly symmetrical light spot using a single mirror. The shaping and focusing unit employs a homogenized three-dimensional circularly symmetrical light spot reflecting mirror. Based on a preset front focal length, a preset back focal length, and the light spot distribution pattern of the target light field, a mapping relationship between the energy distribution of the incident light field and the target light field is established. Combining the principles of equal optical path and energy conservation, a surface equation for the reflective surface shape of the three-dimensional circularly symmetrical light spot reflecting mirror corresponding to the target intensity adjustable circularly symmetrical light spot is constructed. The Gaussian beam emitted from the light source is shaped, collimated, and focused to generate the target three-dimensional circularly symmetrical light spot on the working surface. Furthermore, by adjusting the phase of the reflective surface of the three-dimensional circularly symmetrical light spot reflecting mirror, the shape and energy distribution of the generated target three-dimensional circularly symmetrical light spot are adjusted accordingly. This system solves the technical problem of how to simplify the optical path as much as possible, meet the diverse shaping modes while reducing processing complexity, and improving stability and applicability. With fewer optical components and a simplified optical path structure, it achieves the output of a highly uniform and intensity-adjustable target three-dimensional circularly symmetrical light spot. The size of the target three-dimensional circularly symmetrical light spot is arbitrarily adjustable, adapting to the needs of different scenarios in actual processing.

[0078] In one specific embodiment, referred to as Embodiment 1, a single-mirror optical system with an adjustable circularly symmetrical light spot output intensity is provided. The optical system is as follows: Figure 1 As shown, the uncollimated Gaussian beam 4 output from the laser as light source 1 is incident on the shaping and focusing unit 2, where it is collimated, shaped, and focused into a flat-top beam output. The resulting light field distribution on the back focal plane 3 is flat-topped. The mirror shape of the intensity-adjustable three-dimensional circularly symmetric spot reflector is calculated from the collimating focal length F1, the focusing focal length F2, the radius R of the intensity-adjustable circularly symmetric spot on the back focal plane, and the energy mapping relationship between the incident and emitted light fields.

[0079] Based on the principle of equal optical path length in light propagation, an ellipsoidal phase and a non-uniform gradient phase are introduced on the reflecting mirror. The ellipsoidal phase enables the input beam emitted from the point source to be focused at a preset focal length after reflection. The non-uniform gradient phase enables the transformation of the Gaussian intensity distribution of the incident light from the target to a uniform intensity distribution, so that the energy of the input beam at point r on the mirror corresponds to a halo of radius R in the target plane spot. Furthermore, based on the principle of energy conservation, the mapping relationship of the light rays is solved, and the correspondence between the halo of radius R in the three-dimensional circularly symmetric spot of the target and the halo of radius r in the Gaussian beam is as follows:

[0080]

[0081] Where F1 is the preset front focal length; F2 is the preset back focal length, I s (r,θ) represents the initial circularly symmetric polar coordinate distribution of the beam intensity, which, for a Gaussian beam, satisfies a two-dimensional Gaussian distribution; I t (r,θ) represents the polar coordinate distribution of the light intensity of the target three-dimensional circularly symmetric spot. For a circularly symmetric spot with adjustable intensity, it is a normalization constant.

[0082] Based on the above equation, the surface equation z = f(r, w) corresponding to the reflecting surface of the homogenized three-dimensional circularly symmetric light spot single mirror can be solved.

[0083] Specifically, in one example, a single-mirror dot-ring optical system with an incident ray and an outgoing ray at a 120-degree angle is described in Example 1. Figure 6 As shown, in this embodiment, the front focal length of the rotating ellipsoidal mirror is 150mm, the back focal length is 300mm, the point spot energy accounts for 30%, the ring spot energy accounts for 70%, the ring radius is 0.4mm, and the spot energy distribution on the back focal plane is as follows. Figure 7 As shown.

[0084] Example 2 In another specific embodiment, referred to as Example 2, a single-mirror dot-ring optical system with an incident ray and an outgoing ray angle of 60 degrees is provided, such as Figure 8 As shown, in this embodiment, the front focal length of the rotating ellipsoidal mirror is 150mm, the back focal length is 300mm, the point spot energy accounts for 30%, the ring spot energy accounts for 70%, the ring radius is 0.4mm, and the spot energy distribution on the back focal plane is as follows. Figure 9 As shown.

[0085] Example 3: In another specific embodiment, referred to as Example 3, a single-mirror flat-top optical system with an incident ray and an outgoing ray angle of 120 degrees is provided. For example... Figure 6 As shown, the optical system is specifically a single-mirror flat-top optical system with an incident ray and an outgoing ray angle of 60 degrees. The overall structure is the same as in Example 1, except that the polar coordinate distribution of the target's three-dimensional circularly symmetrical light spot intensity is different. t (r,θ) is replaced by a preset target light intensity distribution, whose light intensity changes with the radius of the target light spot, and the shape of the mirror changes accordingly. The calculation method of the surface equation of the reflecting mirror in this embodiment is the same as that in Embodiment 1, and will not be repeated here.

[0086] Specifically, in this embodiment, the front focal length is 150mm, the rear focal length is 300mm, the radius of the annular convex spot is 10mm, and the light intensity distribution of the annular convex spot is uniform. The energy distribution of the spot on the rear focal plane is as follows. Figure 10 As shown.

[0087] Example 4: In another specific embodiment, referred to as Example 4, a single-mirror flat-top optical system with an incident ray and an outgoing ray angle of 60 degrees is provided. For example... Figure 8 As shown, the optical system is specifically a single-mirror annular concave optical system with an incident ray and an outgoing ray angle of 60 degrees. The overall structure is the same as in Example 2, except that the polar coordinate distribution of the target's three-dimensional circularly symmetrical light spot intensity is different. t (r,θ) is replaced by a preset target light intensity distribution, whose light intensity changes with the radius of the target light spot, and the shape of the mirror changes accordingly. The calculation method of the surface equation of the reflecting mirror in this embodiment is the same as that in Embodiment 2, and will not be repeated here.

[0088] Specifically, in this embodiment, the front focal length of the rotating ellipsoidal mirror is 150mm, the back focal length is 300mm, the radius of the concave spot is 10mm, and the intensity distribution of the concave spot satisfies I∝R. 2 The energy distribution of the light spot on the back focal plane is as follows Figure 11 As shown.

[0089] In Example 3, the flat-top spot has a more uniform light intensity distribution, which will not lead to partial overexposure and partial underexposure, making it suitable for micro-nano processing in fields such as solar panels. In Example 4, the concave-ring spot has a temperature field distribution that is closer to the flat-top distribution because the intensity at the center of the spot is lower than that at the periphery, making it suitable for preheating of highly reflective materials and composite laser processing. In Examples 1 and 2, the high-energy-density Gaussian spot at the center can act deep into the material, increasing the laser's depth of action. Appropriately introducing a ring spot can preheat the processed material and stabilize the molten pool, reducing welding defects, making it suitable for high-power laser thick plate welding applications.

[0090] Those skilled in the art will readily understand that the above description is merely 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 within the scope of protection of the present invention.

Claims

1. An optical system that outputs a circularly symmetrical light spot using a single mirror, characterized in that, include: The light source and the shaping and focusing unit are placed sequentially along the optical path; The light source is used to generate a Gaussian beam; The shaping and focusing unit employs a homogenized three-dimensional circularly symmetrical beam reflector to shape the incident Gaussian beam, change the beam distribution pattern, and focus it at a preset position on the working surface to form a target three-dimensional circularly symmetrical beam with adjustable size; different beam portions of the three-dimensional circularly symmetrical beam are located on the same / different planes. The phase of the reflecting surface of the shaping and focusing unit is determined in the following way: the surface equation of the basic ellipsoidal mirror is determined based on the collimating focal length, focusing focal length, incident ray of the Gaussian beam, and outgoing ray corresponding to the target three-dimensional circularly symmetrical spot reflecting mirror; then the mirror shaping area and the corresponding divergence angle are determined according to the energy distribution corresponding to the target three-dimensional circularly symmetrical spot; and the corresponding lateral offset phase and longitudinal offset phase are superimposed on different mirror shaping areas. The three-dimensional circularly symmetrical light spot reflecting mirror is a rotating ellipsoidal mirror. The rotating ellipsoidal mirror includes a focal point in the incident direction and a focal point in the exit direction, denoted as the front focal point and the rear focal point, respectively. The focal plane corresponding to the front focal point is denoted as the front focal plane, and the light source is located on the front focal plane. The focal plane corresponding to the rear focal point is denoted as the rear focal plane, and the working surface is the rear focal plane. The distance from the front focal point to the center point of the reflecting surface is denoted as the collimating focal length. The distance from the center point of the rear focal plane to the center point of the reflecting surface is denoted as the focusing focal length. Based on the principle of equal optical path in light propagation, an ellipsoidal phase and a gradient phase are introduced on the reflecting surface. The ellipsoidal phase is used to focus the incident light rays at a preset position on the working surface after reflection. The gradient phase is used to shape the incident Gaussian beam, change the spot distribution pattern, and obtain a target three-dimensional circularly symmetrical spot with uniform intensity distribution. The ellipsoidal phase is the focusing phase, and the gradient phase is the defocusing phase, including a lateral offset phase and a longitudinal offset phase. The energy of the input beam at point r on the reflecting mirror surface corresponds to a ring of radius R on the working surface. The correspondence between the ring of radius R on the target's three-dimensional circularly symmetric spot and the ring of radius r on the incident Gaussian beam is as follows: in, The polar coordinate distribution of the incident circular beam intensity is given. For a Gaussian beam, it satisfies a two-dimensional Gaussian distribution. The polar coordinate distribution of the light intensity of the target flat-topped circular light spot.

2. The optical system as described in claim 1, characterized in that, The shaping and focusing unit is used to change the light intensity distribution of the target three-dimensional circularly symmetrical light spot by adjusting the lateral offset phase. The target three-dimensional circularly symmetrical light spot includes: a flat-top light spot, a concave ring light spot, and a convex ring light spot.

3. The optical system as described in claim 1, characterized in that, The shaping and focusing unit is used to change the focal plane position of different spot portions in the target three-dimensional circularly symmetrical spot by adjusting the longitudinal offset phase.

4. The optical system as claimed in claim 1, characterized in that, The mirror-shaping area of ​​the reflective surface is determined by the following method: the incident light is divided into cones, and the mirror is divided into different shaping areas according to the energy distribution of the target three-dimensional circular symmetrical light spot. The divergence angle range of each area is determined by the energy ratio between the different shaping areas.

5. The optical system as claimed in claim 1, characterized in that, The boundaries of different regions of the reflective surface of the shaping and focusing unit are homogenized to make the mirror surface smooth and without grooves. The mirror surface of the shaping and focusing unit is homogenized in the following way: radial lines are drawn from the center of the mirror surface along the radius, and the phase difference value is subtracted from the processing points located in different shaping regions on the same line.

6. The optical system as claimed in claim 1, characterized in that, The light source is a laser.

7. The optical system as claimed in claim 1, characterized in that, The reflective surface of the shaping and focusing unit is a non-rotationally symmetric freeform surface.

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