Dual-mode laser heating spot homogenization regulation method and system thereof

Abstract

This invention relates to the field of laser beam shaping and heating technology, specifically to a dual-mode laser heating spot homogenization control method and system. The invention achieves automatic selection between point heating and surface heating optical paths through an optical path switching mechanism, and controls a displacement actuator to drive a collimation module to move along the optical axis using a preset mapping relationship, changing the divergence angle and projection aperture of the incident beam, thus achieving rapid spot size transformation without changing external mirrors. The laser beam sequentially passes through a total internal reflection integrating mirror and a freeform surface homogenizing mirror for two-stage homogenization and decoherence processing, generating a rectangular uniform spot. A detection module acquires the spot heat flux distribution data, iteratively calculates the displacement compensation amount using an optimized algorithm model, and performs micron-level compensation by the displacement actuator, locking the spot uniformity above a preset threshold in real time. A conformal microchannel liquid cooling circuit is provided on the back of the total internal reflection integrating mirror for forced cooling to maintain surface shape accuracy.

Description

Technical Field

[0001] This invention relates to the field of laser beam shaping and heating technology, and more specifically, to a method and system for controlling the uniformity of a dual-mode laser heating spot. Background Technology

[0002] In applications such as high-power laser material processing, ground thermal radiation simulation and evaluation of hot-end components of aero-engines, and performance testing of thermal barrier coatings, it is typically necessary to project a rectangular laser spot with a highly uniform energy distribution onto the target area. Simultaneously, to simulate the thermal load characteristics under different operating conditions, it is often necessary to flexibly switch between two heating modes: one is a point heating mode, where laser energy is concentrated in a small rectangular area to form an extremely high power density per unit area, simulating localized extreme thermal shock; the other is a surface heating mode, where laser energy is dispersed over a larger rectangular area to form a relatively mild but uniformly distributed heat flux density, simulating large-area steady-state thermal radiation. Furthermore, the requirements for the laser spot size vary at different experimental stages, and the system must have the ability to rapidly change the spot size.

[0003] In existing technologies, to achieve the switching between point heating and surface heating modes, two independent laser processing systems are typically required, or a single machine can be used where operators manually replace focusing lenses, field lenses, or homogenizing lenses. This not only significantly increases equipment costs and floor space, but also requires stopping the machine and opening the sealed optical path cavity each time an optical component is replaced, making the operation cumbersome and time-consuming. More importantly, replacing lenses disrupts the original optical alignment of the system, necessitating recalibration of beam quality and realignment of the optical path, introducing human error and batch-to-batch inconsistencies. Furthermore, this open-cavity component replacement operation is difficult to meet the requirements of experimental conditions that require maintaining high cleanliness or specific atmospheres.

[0004] On the other hand, traditional methods for adjusting the spot size also rely on replacing field lenses with different focal lengths or changing the axial spacing between multiple lenses. Either way, it requires preparing spare lenses of various specifications and repeatedly disassembling and reassembling them, or adjusting other parameters with limited mechanism travel that may affect subsequent optical paths. These problems fundamentally limit the applicability of laser heating systems in multi-task, fast-paced experimental processes.

[0005] In addition to the aforementioned operational defects, existing technologies also suffer from a physical problem affecting the long-term operational stability of the system. High-power homogenizing elements such as total internal reflection integrating mirrors are typically made of highly reflective metal substrates. However, when subjected to continuous irradiation by lasers of several kilowatts or even higher power, their surfaces still absorb a very small portion of the laser energy (the absorption rate is usually on the order of a few thousandths). Due to the extremely high total laser power, the absolute value of this absorbed heat is considerable. Without effective active thermal management, the substrate temperature will continue to rise, and the changes in surface shape accuracy caused by thermal expansion and contraction will disrupt the sub-micron geometric accuracy of the microcylindrical array, ultimately leading to irreversible degradation of the uniformity of the output beam over time. Conventional solutions to this problem in existing technologies include attaching a water-cooling plate to the back of the mirror or using air cooling. However, these solutions have an inherent defect of mismatch between the cooling path and the mirror surface shape, which can easily lead to uneven heat transfer and asymmetric thermal deformation across the mirror surface, potentially exacerbating the deterioration of uniformity. More importantly, the existing system lacks the ability to perform online quantitative detection of the energy distribution of the light spot and real-time closed-loop compensation based on the detection results, and cannot actively combat the aforementioned thermally induced uniformity degradation.

[0006] In summary, there is an urgent need for a method and system that can automatically switch between point heating and surface heating modes within a single set of equipment, quickly adjust the spot size without changing parts, and perform online detection and closed-loop feedback control of the spot uniformity, in order to overcome the above-mentioned shortcomings of the existing technology. Summary of the Invention

[0007] The technical problem this invention aims to solve is to address the issues in existing technologies where switching heating modes and changing spot size requires stopping the machine to open the cavity and replace external lenses, leading to cumbersome operation, damage to the optical path seal, and poor batch-to-batch consistency. It also addresses the shortcomings of total internal reflection integrating mirrors, where thermal deformation under high-power, long-term irradiation causes spot uniformity degradation and the lack of online closed-loop compensation methods. This invention provides a dual-mode laser heating spot uniformity control method and system. Its purpose is to achieve automatic switching between point heating and surface heating modes within a single optical system, to complete rapid spot size changes without replacing any external optical lenses, and to achieve real-time closed-loop control of spot uniformity based on online heat flow distribution detection and iterative calculation using optimization algorithms, thereby continuously locking the spot uniformity above a preset threshold.

[0008] To achieve the above objectives, the technical solution of the invention is achieved through the following measures:

[0009] A method for controlling the uniformity of a dual-mode laser heating spot includes the following steps:

[0010] S10. Receive a switching instruction carrying a target heating mode, wherein the target heating mode is a point heating mode or a surface heating mode.

[0011] S20. According to the switching command, control the optical path switching mechanism to switch the heating optical path corresponding to the target heating mode into the working optical axis; wherein, the point heating mode corresponds to the point heating optical path, and the surface heating mode corresponds to the surface heating optical path.

[0012] S30. In response to the switching command and / or the received user input, a spot-changing command carrying the target spot size is generated, and according to the spot-changing command and the preset mapping relationship, the displacement actuator is controlled to drive the collimation module in the corresponding heating optical path to move along the optical axis to the target displacement amount, so as to change the laser beam parameters incident on the total internal reflection integrating mirror of the corresponding mode; wherein, the collimation module includes a point heating collimation module and a surface heating collimation module, which correspond to the point heating optical path and the surface heating optical path, respectively;

[0013] S40. The laser beam is sequentially passed through the total internal reflection integrating mirror and the freeform surface homogenizing mirror for homogenization and decoherence processing, generating a homogenized spot with the target spot size in the target area; wherein, in point heating mode, the total internal reflection integrating mirror is a point-heated total internal reflection integrating mirror group, which consists of two one-dimensional microcylindrical array mirrors arranged orthogonally to each other; in surface heating mode, the total internal reflection integrating mirror is a surface-heated total internal reflection integrating mirror, which is a single two-dimensional microcylindrical array mirror; S50. The spot heat flow distribution data of the target area is obtained through the detection module;

[0014] S60. Input the heat flow distribution data of the light spot into the optimization algorithm model, and iteratively calculate the displacement compensation amount of the collimation module;

[0015] S70. Control the displacement actuator to finely adjust the axial position of the collimation module along the optical axis according to the displacement compensation amount, so as to compensate the uniformity of the light spot to above a preset threshold.

[0016] In the above technical solution of the present invention, the point heating mode and the surface heating mode correspond to different thermal load simulation requirements. In the point heating mode, the system highly concentrates laser energy into a small rectangular area, forming an extremely high power density per unit area within this area, used to simulate the local extreme thermal shock and other conditions experienced by the leading edge of an aero-engine turbine blade. In the surface heating mode, the system disperses laser energy into a larger rectangular area, forming a relatively low but uniformly distributed heat flux density within this area, used to simulate the steady-state large-area thermal radiation of the combustion chamber wall. These two modes are provided by two independently designed optical hardware paths (i.e., the point heating optical path and the surface heating optical path) within the system, and automatic selection between the two is achieved through the controlled action of the optical path switching mechanism in step S20. Preferably, the optical path switching mechanism is a six-axis servo adjustment frame, which has the ability to move along six degrees of freedom in space. The final light output ends of the point heating optical path module and the surface heating optical path module it carries can be precisely moved to a calibration position that coincides with the working optical axis of the system under the drive of the servo motor group, thereby completing the automatic switching of the optical path. The working optical axis is a spatial reference straight line that starts from the laser source, passes through the collimation module, the total reflection integrating mirror, the freeform surface homogenizing mirror, and finally reaches the target area. All optical components of the system are precisely arranged around this working optical axis.

[0017] The preset mapping relationship described in step S30 is the key technical support for achieving "spot size adjustment without replacement" in this method. It is established through prior optical simulation and integrated prototype calibration, and stored in the control module in the form of lookup tables. The physical basis of this mapping relationship lies in the fact that the final homogenization and superposition effect of the beam and the size of the synthesized spot strongly depend on the wavefront curvature radius and projection aperture of the incident beam received by the total internal reflection integrator. When the collimation module undergoes linear displacement along the optical axis, the divergence angle or convergence of the outgoing beam and the beam coverage diameter projected onto the surface of the total internal reflection integrator will change sensitively, thereby altering the beam state received by each sub-aperture on the microcylindrical array and the far-field superposition effect, ultimately manifesting as a controllable change in the spot size on the target plane. Based on this physical mechanism, this scheme transforms the "discrete replacement" spot size adjustment operation of changing field lenses in traditional technology into a "continuous linear motion" spot size adjustment operation precisely controlled by the displacement, without requiring the replacement of any external lenses, thus maintaining the complete closure of the optical path.

[0018] In step S40, the laser beam passes sequentially through a total internal reflection integrating mirror and a freeform surface homogenizing mirror, forming a two-stage cascaded homogenizing optical link. The first-stage total internal reflection integrating mirror undertakes the primary task of energy distribution reshaping. Its working surface is machined with a periodic array of hundreds of micron-sized cylindrical units using ultra-precision diamond turning. When the laser beam is incident on this array, each microcylindrical unit intercepts a local sub-aperture of the incident beam and expands and reflects it outward, causing the outgoing beams from adjacent sub-apertures to overlap and superimpose in the far field. According to the integration principle of statistical optics, the incoherent or weakly coherent superposition of a large number of sub-beams can smooth the original Gaussian or near-Gaussian intensity distribution into an approximately rectangular flat-top distribution. However, this method based on periodic sub-aperture segmentation and superposition inevitably introduces a physical defect: due to the high coherence of the laser, there is a regular optical path difference between adjacent sub-beams, resulting in alternating bright and dark interference fringes on the target plane, destroying the uniformity of microscopic optical intensity. To address this defect, this scheme introduces a freeform surface homogenizing mirror in the second stage. This lens is a transmissive optical element, with at least one surface fabricated with a non-rotationally symmetric array of free-form micro-relief structures generated using a specific algorithm. Each micro-relief unit applies minute, random angular deflection and optical path modulation to a tiny region of the passing beam, equivalent to introducing tens of thousands of random phase perturbations into the incident wavefront. These random perturbations cause the originally highly coherent sub-beams to lose their regular phase-locked relationship, statistically achieving decoherence processing, thereby eliminating interference fringes and further smoothing local energy fluctuations.

[0019] In point heating mode, to meet the operational requirements under extremely high power density conditions and reduce the concentration of heat load on a single optical element, a point-heated total internal reflection integrating mirror assembly is adopted. This consists of two independent one-dimensional microcylindrical array mirrors orthogonally arranged, responsible for beam splitting and homogenization in the horizontal and vertical directions, respectively. In surface heating mode, the power density is reduced to the megawatt-per-square-meter level, and the in-plane gradient of heat load is significantly reduced. At this time, to shorten the optical path, simplify the structure, and eliminate assembly orthogonality errors, a surface-heated total internal reflection integrating mirror is adopted, namely a single two-dimensional microcylindrical array mirror. Its orthogonal microcylindrical array is directly formed on the same copper substrate in the same ultra-precision machining process, ensuring near-perfect geometric orthogonality between the two-dimensional arrays from a manufacturing perspective.

[0020] In step S50, acquiring the spot heat flux distribution data of the target area through the detection module is fundamental to achieving closed-loop control. This detection module integrates a high-speed cooled infrared thermal imager and a high-dynamic beam analysis camera, employing a multi-sensor fusion strategy. The infrared thermal imager acquires the two-dimensional temperature field of the standard absorbing target surface, and combines this with known thermophysical parameters of the target material to obtain the absolute heat flux density value. The high-dynamic beam analysis camera simultaneously acquires the relative light intensity distribution with high spatial resolution. Through a pixel-level data fusion algorithm, these two sensors generate a two-dimensional spot heat flux distribution data matrix that possesses both absolute dimensions and high spatial resolution, providing accurate, reliable, and physically meaningful feedback signals for subsequent optimization of the algorithm model.

[0021] In step S60, the heat flux distribution data of the light spot is input into the optimization algorithm model for iterative calculation. The preferred optimization algorithm model is a genetic algorithm model, which uses the axial displacement micro-compensation of the collimation module as the variable to be optimized, and the degree to which the light spot uniformity calculated from the two-dimensional heat flux distribution data deviates from a preset threshold as the evaluation criterion for individual adaptability. Due to factors such as residual aberrations of the optical system and thermal lensing effects, the displacement of the collimation module and the final light spot uniformity typically exhibit a complex response relationship with multiple local extrema. Traditional gradient-based search algorithms are prone to getting trapped in local optima in such solution spaces, failing to guarantee optimization results. However, the genetic algorithm model used in this scheme, as a heuristic global random search algorithm, can effectively escape the local optimum trap by leveraging its parallel search and probabilistic mutation mechanism, robustly searching in the complex solution space for the optimal displacement compensation amount that restores the light spot uniformity to above the preset threshold.

[0022] Step S70 physically implements the displacement compensation, controlling the displacement actuator to drive the collimation module to complete axial micro-motion from the nanometer to the micrometer level. Steps S50 to S70 constitute a complete "detection-calculation-compensation" closed-loop circuit, which can run continuously online, counteract the gradual drift of the system state, and lock the uniformity of the light spot at a high quality level in real time.

[0023] As a further limitation on step S40 in the above method under point heating mode, when the target heating mode is point heating mode, the laser beam is collimated using a point heating collimation module composed of an off-axis parabolic mirror and an achromatic lens group. The off-axis parabolic mirror efficiently collimates the diverging beam emitted from the optical fiber without central obstruction, while the achromatic lens group is used to finely compensate for residual chromatic aberration and wavefront distortion that may be introduced due to wavelength drift or processing errors. The collimated laser beam passes sequentially through two one-dimensional microcylindrical array mirrors in the point heating total internal reflection integrating mirror group, where beam splitting and homogenization are performed in the horizontal and vertical directions, respectively, forming an initial rectangular flat-top distribution beam. Subsequently, this initial rectangular flat-top distribution beam continues to pass through the first freeform surface homogenizing lens for secondary homogenization and decoherence processing, generating a rectangular uniform spot in the target area.

[0024] Correspondingly, when the target heating mode is surface heating mode, after the laser beam is collimated using the surface heating collimation module, the collimated beam undergoes two-dimensional homogenization through the surface heating total internal reflection integrator. Since the two-dimensional microcylindrical array of the surface heating total internal reflection integrator is directly fabricated on the same substrate, the two-dimensional homogenization process does not need to be completed in steps and can be achieved in one step. The homogenized beam then continues to pass through the second freeform surface homogenizing lens for secondary homogenization, generating a rectangular uniform spot in the target region.

[0025] As an important supplement to the above method, this method also includes a parallel step of thermal management for the total internal reflection integrating mirror: forced convection heat transfer is achieved by driving the cooling medium through a conformal microchannel liquid cooling circuit set on the back of the total internal reflection integrating mirror. "Conformal" means that the microchannel of the liquid cooling circuit is designed according to the surface profile of the mirror, ensuring that the microchannel and the reflective working surface are approximately equidistant, thereby achieving consistency in thermal resistance and uniform cooling throughout the mirror. "Microchannel" refers to a fluid channel with a hydraulic diameter on the sub-millimeter to millimeter scale, where forced convection can achieve extremely high heat transfer efficiency. Through this active thermal management method, the temperature rise of the total internal reflection integrating mirror substrate can be controlled within the preset design target, maintaining its sub-micrometer surface accuracy without significant degradation, thus ensuring the stability of the beam uniformity under high-power continuous light output. This thermal management step, together with the closed-loop displacement compensation in step S70, constitutes a dual parallel guarantee mechanism of "temperature control to maintain the inherent accuracy of the substrate" and "compensation to correct acquired residual deviations."

[0026] The specific content of the preset mapping relationship mentioned in step S30 includes: in point heating mode, establishing a first correspondence between multiple sets of typical spot sizes and the first displacement range of the point heating collimation module; in area heating mode, establishing a second correspondence between multiple sets of typical spot sizes and the second displacement range of the area heating collimation module. This mapping relationship is pre-stored in the non-volatile memory of the control module in the form of a data table, etc. When the spot size change command is sent, the control module only needs to look up the corresponding relationship table according to the current working mode to quickly obtain the target displacement. Based on this mapping relationship, the collimation module is driven to move within the corresponding displacement range by the displacement actuator, so that the spot size can be quickly switched without changing any external lenses. The entire spot size change action can be completed automatically within a few seconds to tens of seconds, which greatly improves the system's response speed and flexibility in dealing with multi-tasking processes.

[0027] Corresponding to the above methods, the present invention also protects a dual-mode laser heating spot uniformity control system for implementing any of the above methods. The system includes: a point-heating optical path module, comprising a first laser source, a first optical fiber, a point-heating collimation module, a point-heating total internal reflection integrating mirror group, and a first freeform surface homogenizing mirror, wherein the point-heating total internal reflection integrating mirror group is composed of two orthogonally arranged mirrors with a one-dimensional microcylindrical array on their surfaces; a surface-heating optical path module, comprising a second laser source, a second optical fiber, a surface-heating collimation module, a surface-heating total internal reflection integrating mirror, and a second freeform surface homogenizing mirror, wherein the surface-heating total internal reflection integrating mirror is a single mirror with a two-dimensional microcylindrical array on its surface; an optical path switching mechanism, used to respond to a switching command to switch either the point-heating optical path module or the surface-heating optical path module into the working optical axis; a displacement actuator, drivenly connected to the point-heating collimation module and / or the surface-heating collimation module, used to drive the corresponding collimation module to move along the optical axis; a detection module, used to acquire spot heat flow distribution data of the target area; and a control module, communicatively connected to the optical path switching mechanism, the displacement actuator, and the detection module, respectively. The control module is configured to: receive a switching command and a spot-changing command generated based on the switching command and / or user input; control the optical path switching mechanism to operate according to the switching command; control the displacement actuator to drive the corresponding collimation module to move to the target displacement amount according to the spot-changing command and the stored mapping relationship between the spot size and the collimation module displacement; receive the spot heat flux distribution data and run an optimization algorithm model to calculate the displacement compensation amount; and control the displacement actuator to fine-tune the axial position of the collimation module according to the displacement compensation amount.

[0028] In the above system, the point heating collimation module in the point heating optical path module specifically includes an off-axis parabolic mirror and an achromatic lens group. This combination allows the diverging laser beam from the first optical fiber to first be incident on the off-axis parabolic mirror, which performs primary collimation in an off-axis, unobstructed manner; the achromatic lens group then performs fine compensation for residual wavefront errors. The two one-dimensional microcylindrical array mirrors in the point heating total internal reflection integrating mirror group are designated as horizontal and vertical homogenizing mirrors, respectively, to homogenize the laser beam and jointly shape the initial rectangular flat-top distribution.

[0029] The surface-heated total internal reflection integrating mirror in the surface-heated optical path module is a single two-dimensional microcylindrical array mirror, which is directly fabricated on the same metal substrate. This integrated structure ensures the orthogonality accuracy and array continuity between the two-dimensional microcylindrical arrays from a manufacturing perspective, avoids the assembly orthogonality errors inherent in discrete designs, and ensures the compactness and high rigidity of the surface-heated optical path.

[0030] The system further includes a liquid cooling device. This device comprises a conformal microchannel liquid cooling circuit disposed on the back of the point-heated total internal reflection integrator mirror assembly and the surface-heated total internal reflection integrator mirror assembly, and a circulating cooling unit fluidly connected to the microchannel liquid cooling circuit. During system operation, the circulating cooling unit continuously drives a temperature-controlled cooling medium (such as deionized water) through the conformal microchannel liquid cooling circuit on the back of each total internal reflection integrator mirror. By forcibly convecting and transferring the heat absorbed by the mirror body, the system forcibly cools the corresponding total internal reflection integrator mirror, effectively controlling its operating temperature rise within the design limits.

[0031] In the above system, the displacement actuator preferably includes a high-rigidity linear displacement stage driven by a linear motor and an absolute position encoder. The high-rigidity linear displacement stage provides nanometer- to micrometer-level displacement resolution, high repeatability, and load-bearing rigidity, while the absolute position encoder provides direct position closed-loop feedback, ensuring that both the target displacement established by the mapping relationship and the micro-compensation output by the closed-loop algorithm can be accurately executed. The optical path switching mechanism is preferably a six-axis servo adjustment frame, whose multi-axis collaborative positioning capability and position memory function provide the execution basis for achieving rapid, automatic, and high-precision switching between the two optical path modules.

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

[0033] The optical path switching mechanism enables automatic selection between point heating and surface heating optical paths, and achieves rapid spot size changes without replacing external lenses through a continuous spot size adjustment method with varying divergence angle. This solves the operational pain point of traditional solutions requiring shutdown and cavity opening for component replacement. An online thermal flux closed-loop compensation mechanism uses a detection module to acquire spot thermal flux distribution data, optimizes the algorithm model to iteratively solve for displacement compensation, and drives the displacement actuator to perform fine adjustments. This improves spot uniformity from open-loop setting to closed-loop real-time locking, overcoming the uniformity degradation caused by thermal deformation of the total internal reflection integrating mirror. These mechanisms, combined with conformal microchannel liquid cooling active thermal management and a two-stage homogenization optical architecture, ensure high uniformity and stability of the output spot under long-term full-power operation. Attached Figure Description

[0034] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0035] Figure 1 This is a schematic flowchart of an embodiment of the dual-mode laser heating spot uniformity control method of the present invention;

[0036] Figure 2 This is a structural block diagram of an embodiment of the dual-mode laser heating spot uniformity control system of the present invention;

[0037] Figure 3 for Figure 2 A schematic diagram of the optical layout of the point heating optical path module in the system shown.

[0038] Figure 4 for Figure 2 The diagram shows the optical layout of the top heating optical path module in the system. Detailed Implementation

[0039] Specific embodiments of the invention will now be described in detail. Although the invention is described in conjunction with these specific embodiments, it should be understood that it is not intended to limit the invention to these specific embodiments. Rather, these embodiments are intended to cover alternative, modified, or equivalent embodiments that may be included within the spirit and scope of the invention as defined by the claims. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the invention. The invention may be practiced without some or all of these specific details.

[0040] When used in conjunction with the terms "comprising," "method comprising," or similar language in this specification and appended claims, the singular forms "a," "some," and "the" include plural references unless the context clearly indicates otherwise. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0041] See Figures 1 to 4 This embodiment provides a dual-mode laser heating spot uniformity control system and its working method, which will be described in detail below.

[0042] For system composition, please refer to [link / reference]. Figure 2 This system consists of six major functional modules: point heating optical path module, surface heating optical path module, optical path switching mechanism, displacement execution mechanism, detection module, and control module.

[0043] The point heating optical path module is a hardware assembly used to implement the optical path in point heating mode. See also Figure 3In this embodiment, the module includes a first laser source, a first optical fiber, a point-heated collimation module, a point-heated total internal reflection integrating mirror group, and a first freeform surface homogenizing lens. The first laser source is a domestically produced high-power fiber laser, with an output center wavelength of 1064nm in the near-infrared band, and its output power can be continuously or incrementally adjusted from hundreds of watts to thousands of watts according to task requirements. The first optical fiber is responsible for flexibly transmitting the laser beam output from the first laser source to the point-heated collimation module. It is preferably a small-core multimode fiber, with a core diameter of, for example, 200μm, to ensure that the fiber's output end has high brightness and a relatively small initial divergence angle. The point-heated collimation module is a key upstream component of this module, and its function is to collimate the divergent laser beam emitted from the output end of the first optical fiber. This point-heated collimation module consists of an off-axis parabolic copper reflector and a set of achromatic lenses connected in series. An off-axis parabolic mirror is positioned off-axis from the optical axis by a certain amount, achieving unobstructed collimation of the incident diverging beam within its effective working aperture. Simultaneously, the high thermal conductivity and high reflectivity of the copper substrate and its metal coating withstand the initial bombardment of the still-uniform high-energy-density original light spot at the fiber optic exit end. The achromatic lens group, composed of multiple cemented or closely spaced optical glass lenses with different refractive indices and dispersion characteristics, provides fine compensation for wavefront residual errors in the output beam of the off-axis parabolic mirror. A point-heated total internal reflection integrating mirror group, positioned in the optical path after the point-heated collimation module, consists of two independently fabricated one-dimensional microcylindrical array mirrors arranged in mutually orthogonal spatial orientations. The first one-dimensional microcylindrical array mirror has its microcylindrical generatrices arranged horizontally, which serves to vertically segment, expand, and homogenize the light beam. After being reflected by this mirror, the beam's direction of travel is deflected by approximately 90 degrees before entering the second one-dimensional microcylindrical array mirror, whose microcylindrical generatrices are arranged vertically, thus horizontally segmenting, expanding, and homogenizing the beam. Each mirror's substrate is made of a high thermal conductivity copper alloy, and the reflective working surface is formed using ultra-precision diamond turning technology to create an array of hundreds of alternating concave / convex microcylindrical units. The first freeform homogenizing lens, located at the end of the optical path after the point-heated total internal reflection integrating mirror assembly, is a transmissive optical plate. At least one surface of this plate has a non-rotationally symmetric random microprism array micro-relief structure generated and fabricated using a specialized algorithm. The spatial frequency and unit depth of this micro-relief structure are optimized for the parameters of the point-heated optical path.

[0044] The surface-heated optical path module is a hardware assembly used to implement the optical path in the surface-heated mode. See also Figure 4The module includes a second laser source, a second optical fiber, a surface-heated collimation module, a surface-heated total internal reflection integrating mirror, and a second freeform homogenizing mirror. The core diameter of the second optical fiber is larger than that of the first optical fiber, preferably 800 μm, to meet the transmission requirements of a larger beam coverage area and relatively mild power density in the surface-heated mode. The surface-heated collimation module can use an off-axis parabolic mirror or a set of achromatic collimating lenses to collimate the diverging beam emitted from the second optical fiber. The surface-heated total internal reflection integrating mirror is located after the surface-heated collimation module and is a single two-dimensional microcylindrical array mirror. Its core feature is that the microcylindrical array arranged along two orthogonal directions on the reflecting surface is directly formed on the same copper substrate in the same ultra-precision diamond turning process, ensuring near-perfect orthogonality and gapless transition between the two-dimensional arrays without subsequent mechanical assembly or alignment. The second freeform homogenizing mirror is also a transmission element with a random microprism array structure on its surface, but this structure is differentially optimized according to the specific parameters of the surface-heated optical path (such as beam aperture and transmission optical path).

[0045] In this embodiment, the optical path switching mechanism employs a six-axis servo adjustment frame. This frame has a fixed support frame or transition plate for the point-heating optical path module and the surface-heating optical path module. Each of its motion axes is driven by an independent servo motor and integrates an absolute grating ruler or other similar absolute position encoder. Under external control commands, the six-axis servo adjustment frame can precisely move the final light-emitting end of a specified optical path module to a position completely aligned with the system's preset working optical axis.

[0046] In this embodiment, the displacement actuator includes a high-rigidity linear displacement stage driven by a linear motor and an absolute position encoder. The high-rigidity linear displacement stage can be designed as a single-axis precision motion platform supported by crossed roller guides and driven by a three-phase brushless linear motor, possessing nanometer-level motion resolution and micrometer-level repeatability. The displacement actuator is connected to both a point-heated collimation module and a surface-heated collimation module via mechanical interfaces, enabling it to drive the collimation module currently engaged with the working optical axis to perform precise linear motion along its own optical axis.

[0047] The detection module is positioned at the target plane of the system and can be controlled to move into or out of the optical path. This module integrates two imaging devices: a high-speed cooled infrared thermal imager and a high dynamic range beam analyzer. The infrared thermal imager performs two-dimensional imaging of the surface temperature field of a standard high-temperature resistant ceramic absorbing target placed in the target area; the high dynamic range beam analyzer, through its built-in precision optical attenuation and beam-shortening system, directly and synchronously acquires two-dimensional intensity distribution images of the laser spot projected onto the target surface. Both image data are transmitted to the control module in real time via a data bus.

[0048] The control module is an industrial control computer or embedded controller. It contains all the software programs and data files required to implement each step of this method, and establishes bidirectional communication connections with the optical path switching mechanism, displacement actuator, and detection module via industrial Ethernet, fieldbus, etc. The control module's non-volatile memory stores a preset mapping lookup table, light spot uniformity evaluation formula code, and optimization algorithm model code (preferably a genetic algorithm model in this embodiment).

[0049] For methodology and process details, please refer to [link / reference]. Figure 1 The method for controlling the uniformity of the dual-mode laser heating spot based on the above system is performed according to the following steps.

[0050] The operator selects the target heating mode for the first stage of the experiment through the graphical user interface of the host computer, such as selecting "point heating mode". The host computer then generates a switching command carrying the target heating mode identifier and sends it to the control module via industrial Ethernet, completing step S10.

[0051] After parsing the switching command, the control module retrieves the pre-calibrated and stored spatial coordinate parameters corresponding to the "point heating mode" from memory and sends motion commands to each servo motor axis of the six-axis servo adjustment frame. The six-axis servo adjustment frame drives the point heating optical path module it carries to move smoothly, precisely moving its final light output end to the calibration position that coincides with the working optical axis of the system, completing the entry of the point heating optical path, i.e., step S20.

[0052] Next, the operator inputs the desired spot size, such as "9mm × 15mm," into the spot size input box on the software interface. The host computer encodes this user input as a spot size change command and sends it to the control module, completing the triggering of the first half of step S30. After receiving the spot size change command, the control module accesses the preset mapping relationship stored in the non-volatile memory. This mapping relationship is divided into two sub-tables. The first correspondence table, corresponding to the current point heating mode, records the numerical correspondence between multiple sets of typical spot sizes and the target displacement of the point heating collimation module within the first displacement range. The control module looks up the corresponding target displacement of "9mm × 15mm" in the table, converts it into a drive command, and sends it to the displacement actuator via the communication bus. The high-rigidity linear displacement stage in the displacement actuator, driven by a linear motor, moves the point heating collimation module precisely along its optical axis to the target displacement, completing step S30. The effect of the axial displacement of the collimation module is to change the divergence angle and spot coverage diameter of the laser beam projected onto the downstream point heating total internal reflection integrating mirror group. To achieve rapid switching of spot size, the maximum speed and acceleration of the linear motor in the displacement actuator are preset to ensure that the collimation module can complete the movement between any two points within its corresponding displacement range and stabilize in place within 30 seconds. At the same time, the mapping relationship is stored in the form of a lookup table, and the access and calculation time of the control module is controlled in the millisecond range. This ensures that the time bottleneck of the entire spot-changing process lies only in the mechanical movement itself.

[0053] In this embodiment, the preset mapping relationship is specifically represented as a parameterized inverse mapping function. The establishment of this mapping function is based on the Gaussian beam propagation theory analysis of the propagation characteristics of fiber-embedded lasers after passing through the collimation module, and the abstraction of parameter transfer relationships in the physical process of homogenization and superposition in the total internal reflection integrating mirror. This is achieved by using different target spot sizes... Polynomial fitting was performed on the calibration experimental data to obtain the mapping equation:

[0054]

[0055] In the formula, The target axial displacement of the collimation module, in millimeters; The target spot size, i.e. the width of the rectangular spot in a certain direction, is carried by the spot-changing command and input to the control module, and the unit is millimeters; , , , The fitting coefficients of the mapping polynomial were obtained through prior optical simulation and integrated prototype experiments, and are stored in the non-volatile memory of the control module. In point heating mode, the above equation is used to independently map and calculate the horizontal width and vertical height of the light spot, and the weighted average of the calculation results in the two directions is taken as the final target displacement. In area heating mode, the feature size corresponding to the equivalent area of ​​the light spot is used in the calculation. Based on this mapping equation, the system can convert any effective target light spot size input by the user into a precise target displacement, thereby driving the displacement actuator to perform positioning motion.

[0056] After completing the optical path switching and size setting, the system triggers the first laser source to emit light. The laser beam is transmitted through the first optical fiber to the point-heated collimation module, where it is collimated by an off-axis parabolic mirror and an achromatic lens group. The collimated beam first enters the first one-dimensional microcylindrical array mirror in the point-heated total internal reflection integrating mirror group, where it is split, broadened, and reflected in the vertical direction. The reflected beam is then folded ninety degrees and enters the second one-dimensional microcylindrical array mirror, where it is split, broadened, and reflected in the horizontal direction. The combined effect of the two mirrors is to generate an initial beam whose intensity envelope has been initially shaped into a rectangular flat-top distribution. This initial beam continues to propagate through the first freeform homogenizing lens. The random microprism array structure on the lens surface applies irregular micro-angle deflection and optical path modulation to each tiny region of the beam, eliminating interference fringe noise from the previous stage and further smoothing energy fluctuations. Finally, a rectangular spot with a size of 9mm × 15mm and high uniformity is projected onto the target area, completing step S40.

[0057] During continuous laser irradiation, the detection module periodically moves into the optical path, executing step S50. A high-speed infrared thermal imager acquires the target surface temperature field. Based on the known thermophysical parameters of the target material, the control module rapidly inverts the absolute value of the heat flux density at each pixel using an algorithm for solving the inverse heat conduction problem. A high dynamic range beam analysis camera simultaneously acquires high spatial resolution light intensity distribution images. The control module executes a fusion algorithm, using the high spatial resolution data from the beam analysis camera to constrain the inversion of the spatial contour, and uses the absolute heat flux values ​​obtained from the infrared thermal imager to perform radiometric calibration on the beam analysis camera data, generating a two-dimensional heat flux distribution data matrix of the light spot.

[0058] The data matrix is ​​then fed into the genetic algorithm model running in the control module, executing step S60. The algorithm model first calls the uniformity evaluation formula to calculate the uniformity value within the effective heating area of ​​the current light spot.

[0059] In this embodiment, the uniformity evaluation formula adopts a composite evaluation index that combines peak-to-valley deviation and root mean square deviation. First, from the two-dimensional heat flux distribution data matrix of the light spot... In the diagram, the effective heating area Ω of the light spot is defined by the standard that the normalized heat flux density value of all pixels within this area is not lower than the maximum heat flux density value. 1 / e². Within the effective heating area. Calculate the average heat flux density. Maximum heat flux density and minimum heat flux density Therefore, the formula for calculating the uniformity of the light spot is obtained:

[0060]

[0061] in, For effective heating area The root mean square deviation of the heat flux density of all pixels within the region is defined as:

[0062]

[0063] In the formula, The uniformity of the light spot is expressed as a percentage; the higher the value, the more uniform the energy distribution. The heat flux density value corresponding to the pixel with coordinates (x,y) in the two-dimensional heat flux distribution data matrix of the light spot is expressed in watts per square meter and is obtained by the detection module through multi-sensor fusion processing. This is the effective heating area of ​​the light spot; This represents the maximum heat flux density within the effective heating region Ω. For effective heating area Minimum heat flux density within; The arithmetic mean of the heat flux density within the effective heating region Ω; For effective heating area The root mean square deviation of internal heat flux density, in watts per square meter; For effective heating area The total number of pixels contained within; The weighting coefficients for the peak-to-valley deviation and root mean square deviation terms are preset parameters, ranging from 0 to 1. The value of this parameter determines the sensitivity of the uniformity evaluation to local extreme "hot spots" or "cold spots." This uniformity value is calculated... The control module can determine whether the current spot quality meets the process requirements of the preset threshold, and use this as the basis for evaluating the individual adaptability in the optimization algorithm model.

[0064] If the calculated current uniformity is lower than a preset threshold (e.g., 93%), the genetic algorithm model initiates the optimization process. This algorithm uses the axial displacement micro-compensation of the point-heated collimation module as the variable to be optimized, and randomly generates a set of candidate solutions within a solution space of ± tens of micrometers as the initial population. The algorithm calls its internal optical simulation engine to quickly predict the changes in the light spot distribution caused by each candidate compensation amount, and then substitutes these predictions into the uniformity evaluation formula to calculate the expected uniformity. Using the degree of closeness between the expected uniformity and the preset threshold as the individual's fitness evaluation value, and through simulating evolutionary operations such as natural selection, gene crossover, and random mutation, after several generations of iteration, the displacement compensation amount represented by the optimal individual in the population converges and is output; this is the optimal displacement compensation amount (e.g., +15 micrometers).

[0065] In this embodiment, the iterative convergence determination of the genetic algorithm model adopts a dual-criteria parallel strategy. Its convergence determination equation is as follows:

[0066]

[0067] Among them, the fitness value of the best individual in each generation Defined as:

[0068]

[0069] In the formula, This is a Boolean variable used for convergence determination; evolution terminates when the value is true. The current generation number is automatically recorded by the loop counter inside the genetic algorithm model. The maximum allowed number of evolution generations is preset and stored in the control module based on the maximum allowable time limit of the system's closed-loop control cycle; For the first The optimal fitness value of all individuals in the population, with a range of (0,1]. The closer the value is to 1, the more likely the candidate displacement compensation amount corresponding to that individual can make the spot uniformity closer to the preset threshold. The backtracking algebra interval for adaptive stability determination is a preset parameter; The minimum distinguishable threshold for adaptive improvement is set by the noise level of the reference uniformity measurement system, which is a preset parameter. The number of inspection cycles required to continuously meet the stability condition is a preset parameter. In the definition of the adaptive function, The total number of individuals in the population. The candidate displacement compensation amount represented by the gene encoding of the j-th individual in the population, in micrometers; The optical simulation engine inside the control module predicts the spot uniformity value that can be achieved after adopting this candidate displacement compensation amount, expressed as a percentage. The threshold value is expressed as a percentage. This dual-criteria convergence determination mechanism uses... It ensures a deterministic upper limit to the real-time response cycle of closed-loop control, and uses a second criterion based on adaptive stability to terminate the iteration in a timely manner when the algorithm has found a satisfactory solution, thus avoiding unnecessary consumption of computational resources.

[0070] The control module adds the +15 micrometer compensation amount to the current target displacement of the collimation module in real time, generates a corrected displacement command, and sends it to the displacement actuator. The high-stiffness linear displacement stage performs micro-level precision micro-motion compensation accordingly, completing step S70. The closed-loop control loop continues to run in a loop, performing real-time detection, iterative optimization, and micro-motion compensation to lock the uniformity above a preset threshold of 93%.

[0071] While all the aforementioned optical processes are underway, the corresponding thermal management steps are also running continuously in parallel. The circulating cooling unit of the liquid cooling system drives constant-temperature deionized water to heat the conformal microchannel liquid cooling circuits on the back of each mirror in the total internal reflection integrating mirror assembly at a preset pressure and flow rate. The deionized water creates forced convection within the microchannels, efficiently and uniformly carrying away the laser energy absorbed by the mirror body. This strictly controls the temperature rise of the mirror substrate to a low level (e.g., no more than 20 Kelvin), maintaining the mirror surface accuracy and ensuring the long-term stability of the light spot uniformity from the source.

[0072] In this embodiment, the thermal management design parameters of the conformal microchannel liquid cooling circuit are determined based on the following set of thermal management design equations:

[0073]

[0074]

[0075]

[0076]

[0077] Among them, Reynolds number And Prandtl The definitions are as follows:

[0078]

[0079]

[0080] In the formula, The Nusselt number represents the dimensionless intensity of convective heat transfer in the cooling medium within the microchannel, calculated using the empirical correlation of forced turbulent convection heat transfer in the tube of the above-mentioned Ditus-Belt form. The convective heat transfer coefficient of the inner wall of the microchannel is expressed in watts per square meter per Kelvin. The pressure loss of the cooling medium along the entire flow path of the microchannel is expressed in Pascals. The temperature rise of the substrate of the total internal reflection integrating mirror is expressed in Kelvin. This value is the core verification indicator for thermal management design. The friction factor is f = 64 / Re for laminar flow and f = 64 / Re for turbulent flow, which can be obtained from Re and microchannel wall roughness using the Blasius formula or Moody diagram. The hydraulic diameter of the microchannel is measured in meters, and is determined by the cross-sectional geometry of the microchannel. Calculation, where This refers to the cross-sectional area of ​​a single microchannel. For wet perimeter; The effective length of a single microchannel is determined by the conformal design path and is expressed in meters. The thermal conductivity of the cooling medium is expressed in watts per meter per Kelvin. The density of the cooling medium is expressed in kilograms per cubic meter. The dynamic viscosity of the cooling medium is expressed in Pascals per second. This refers to the specific heat capacity at constant pressure of the cooling medium, expressed in joules per kilogram per Kelvin. The average flow velocity of the cooling medium in the microchannel is expressed in meters per second and is obtained by dividing the volumetric flow rate set by the circulating cooling unit by the total cross-sectional area of ​​the microchannel. The total inner wall area of ​​the microchannels participating in effective heat exchange, expressed in square meters; The laser power absorbed by the total internal reflection integrator, measured in watts, is obtained by multiplying the total incident laser power onto the integrator by the absorptivity of the mirror at the laser's operating wavelength. This is within the allowable upper limit of the substrate temperature rise for a given total internal reflection integrator. and the maximum allowable output head of the circulating cooling unit Under the dual constraints, the optimal hydraulic diameter of the microchannel is determined in reverse by iteratively solving the thermal management design equations. Channel length and average flow rate of cooling medium The combination of these elements allows for the geometric design of the conformal microchannel liquid cooling circuit and the setting of the operating parameters of the circulating cooling unit.

[0081] When the test requires switching from point heating mode to surface heating mode, the operator selects "surface heating mode" via the host computer and inputs the new target spot size (e.g., 30mm × 50mm). The control module first controls the six-axis servo adjustment frame to engage the surface heating optical path module with the working optical axis, while the point heating optical path module moves out simultaneously. Then, the control module queries the second correspondence under the surface heating mode to obtain the target displacement corresponding to the surface heating collimation module, and controls the displacement actuator to drive the surface heating collimation module to move to that target displacement. After the second laser source emits light, the laser is collimated by the surface heating collimation module, homogenized in two dimensions by the integrated surface heating total internal reflection integrating mirror, and then homogenized a second time by the second freeform surface homogenizing lens, generating a large-area rectangular uniform spot of 30mm × 50mm in the target area. The detection module and closed-loop control logic take over synchronously, continuously maintaining the uniformity index online under the new spot size.

[0082] Based on the above embodiments, this preferred embodiment further optimizes some technical solutions to make them more in line with conventional engineering setup and debugging habits in the field.

[0083] The first and second correspondences in the preset mapping relationship do not entirely rely on discrete point-by-point measured calibration. Near commonly used typical spot sizes, the density of simulation calibration points is appropriately increased, and a piecewise cubic polynomial is used to continuously fit the relationship between the spot size and the target displacement, generating a smooth mapping curve. For atypical edge size requirements, a first-order linear extrapolation is preferentially used to provide the initial displacement value, which is then quickly corrected by a subsequent closed-loop compensation algorithm. This strategy of "piecewise polynomial fitting—linear extrapolation initial estimation—closed-loop refinement" effectively balances the calibration workload with adaptability across the entire size range.

[0084] The high-rigidity linear displacement stage uses crossed roller guides or air-bearing guides, and a coreless three-phase permanent magnet synchronous linear motor is used to eliminate thrust fluctuations caused by cogging effect. The absolute position encoder uses a grating ruler with a resolution better than 50nm, and a dual-rail reading head arrangement is implemented to eliminate Abbe error. The position closed-loop control employs a PID control algorithm with velocity and acceleration feedforwards to ensure short arrival time and no overshoot.

[0085] The initial population of the genetic algorithm model is not generated completely randomly, but rather based on historical data accumulated over long-term system operation. An optimal compensation quantity knowledge base is established, indexed by operating condition tags such as spot size, laser power, and ambient temperature. During the initial optimization search after each spot change, the algorithm prioritizes extracting several historical optimal solutions that best match the current operating condition from the knowledge base and injects them as seed individuals into the initial population. The remaining individuals are still randomly generated to maintain population diversity. This significantly reduces the initial number of generations and accelerates convergence. In the design of the fitness function, in addition to the penalty term for spot uniformity deviation, a penalty term for the width of the spot edge transition zone is also introduced. If the transition width of the predicted spot edge corresponding to a candidate compensation quantity from the high-energy region to the zero-energy region exceeds a preset proportional threshold, a decreasing penalty is applied to the fitness value. This mechanism prevents the algorithm from sacrificing the sharpness of the spot edge to unilaterally improve the uniformity within the effective central heating area, ensuring the engineering practicality of the output spot.

[0086] The cross-sectional shape of the microchannels in the conformal microchannel liquid cooling circuit is locally optimized based on the simulation results of the mirror heat flux distribution. A channel cross-section with a larger depth-to-width ratio can be used in the central region of the mirror with higher power density to enhance heat transfer, while the channel density can be adjusted in the edge region. The circulating cooling unit has the ability to actively regulate the inlet temperature, setting its outlet water temperature slightly higher than the ambient dew point temperature to avoid the risk of condensation while maintaining a sufficient heat transfer temperature difference.

[0087] The infrared thermal imager and beam analyzer achieve synchronous acquisition via a precision beam splitter, ensuring accurate field-of-view registration at the pixel level. The fusion algorithm employs multi-scale image fusion technology based on wavelet transform, weightedly recombining the high-energy, low-frequency components of the infrared thermal imager data with the low-energy, high-frequency components of the beam analyzer data after multi-scale decomposition, further improving the overall performance of the fused data in terms of spatial resolution and temperature measurement accuracy.

[0088] In order to further expand the scope of protection of the present invention and make the granted patent rights more stable, various foreseeable extended implementation methods are provided below, none of which depart from the basic concept of the present invention.

[0089] It should be noted that the various extended implementation methods provided below are merely foreseeable alternatives based on the core concept of this invention, and their purpose is not to limit the scope of protection of the claims, but to illustrate that there are multiple feasible implementation paths for the technical solutions of this invention.

[0090] At the methodological level, the target heating mode is not limited to point heating and area heating modes, but can be further extended to line heating or ring heating modes. The line heating mode uses a combination of cylindrical lens arrays and unidirectional total internal reflection integrating mirrors to generate a slender rectangular light spot in the target area; the ring heating mode inserts ring beam generating elements such as conical lenses into the optical path. The system only needs to add the corresponding heating optical path module, and the optical path switching mechanism can select the slit into the working optical axis to achieve multi-mode expansion. The light spot shape is also not limited to rectangles; circular, elliptical, regular polygonal, or other irregularly shaped light spots can be generated. The arrangement of the corresponding total internal reflection integrating mirror's microcylindrical array can be adaptively adjusted from an orthogonal grid pattern to a radial, ring-shaped, or geometrically conformal mapping-generated curve array based on the target light spot shape.

[0091] The pre-defined mapping relationship is not limited to a lookup table. As an alternative implementation, a pre-trained neural network model can be used instead. This model takes multiple parameters, such as the target spot size, current ambient temperature, real-time laser output power, and fiber core diameter, as multi-dimensional input vectors and directly outputs the target displacement. Compared to lookup tables, neural network models have better nonlinear mapping capabilities and adaptability to changes in environmental parameters.

[0092] The optimization algorithm model in step S60 is not limited to a genetic algorithm model. It can be any one of the following: particle swarm optimization algorithm model, simulated annealing algorithm model, differential evolution algorithm model, ant colony optimization algorithm model, or a hybrid optimization strategy consisting of two or more of them. As long as the model can use the uniformity of the light spot or a composite index constructed based on uniformity as the evaluation function, iterative optimization search can be performed on the displacement compensation amount of the alignment module. The dimension of the variable to be optimized is not limited to a single axial displacement. It can be extended to three-dimensional translational displacement and one-dimensional or multi-dimensional angular tilt, constituting multi-degree-of-freedom pose compensation variables to cope with more complex optical path alignment deviations.

[0093] In the optical link of step S40, diffractive optical elements or reflective spatial light modulators can be inserted at appropriate positions between the total internal reflection integrating mirror and the freeform surface homogenizing lens to perform local energy fine-tuning and wavefront phase correction on the homogenized beam, further improving the customization and uniformity of the final beam spot. The freeform surface homogenizing lens itself can also adopt a replaceable modular design, allowing for the replacement of lens modules with different surface parameters to meet different beam spot size requirements. In this case, the coarse adjustment of the collimation module is responsible for achieving a wide range of size switching, while the lens replacement (if used) is responsible for matching the optimal homogenization parameters for a specific size.

[0094] At the system hardware level, the optical path switching mechanism is not limited to a six-axis servo adjustment frame; it can be a high-precision electric rotary turret, a linear guide switching slide, a swing-type reflector cutting-in / cut-out mechanism, or any other mechanical or electromechanical device capable of enabling selection of one of multiple optical paths. The displacement actuator can also employ a flexible hinged micro-displacement platform driven by piezoelectric ceramic actuators to achieve ultra-high precision compensation displacement at the sub-nanometer to nanometer level, suitable for precision applications with extremely stringent uniformity requirements.

[0095] The detection module can also be expanded to integrate a spectrometer or a Shaker-Hartmann wavefront sensor in the visible to near-infrared bands. The spectrometer is used to monitor minute drifts in the laser center wavelength, while the wavefront sensor is used to directly measure the wavefront aberration of the outgoing beam after passing through the collimation module and total reflection integrating mirror. This additional dimension of diagnostic information can serve as auxiliary input features for optimizing the algorithm model, further improving the predictive capability and convergence speed of closed-loop control.

[0096] The cooling medium in liquid cooling devices is not limited to deionized water. For applications with higher power density and greater heat load, liquid metals (such as gallium indium tin alloy) or nanofluids with added high thermal conductivity nanoparticles can be used as cooling media to achieve better heat transfer performance by utilizing their higher thermal conductivity and lower heat capacity. The temperature control accuracy and flow rate adjustment range of the circulating cooling unit are correspondingly improved according to the physical properties of the medium. Conformal microchannel liquid cooling circuits can also adopt a multi-layer manifold microchannel structure, which reduces the total pressure drop and improves the temperature uniformity of cooling within a large area of ​​the mirror surface by dividing the flow channel layers.

[0097] In addition to managing individual lasers, the control module also provides standardized hardware interfaces and control channels. These interfaces can detect and identify the number of laser expansion modules currently connected to the system (e.g., supporting expansion to a maximum of eight lasers) and establish logical groups for these lasers. Based on complex test task instructions issued by the host computer, the control module can formulate time-division multiplexing or power combination synchronous management strategies for each laser, realizing multi-point synchronous heating or multi-mode combined array irradiation to meet the needs of complex working conditions such as segmented and zoned heating of large components or multi-physics coupling testing.

[0098] The detailed description of the above specific embodiments fully illustrates the feasibility, preferred implementation, and technical effects achieved by the technical solution of the present invention. Those skilled in the art can make several modifications and substitutions based on the above description without departing from the principles and spirit of the present invention, and these modifications and substitutions should also be considered within the scope of protection of the present invention.

[0099] The present invention and its embodiments have been described above. This description is not restrictive, and the accompanying drawings are only one embodiment of the present invention. The actual method is not limited to this. In conclusion, if those skilled in the art are inspired by this description and design similar methods and embodiments without departing from the spirit of the present invention, they should all fall within the protection scope of the present invention.

Claims

1. A method for controlling the uniformity of a dual-mode laser heating spot, characterized in that, Includes the following steps: S10. Receive a switching instruction carrying a target heating mode, wherein the target heating mode is a point heating mode or a surface heating mode. S20. According to the switching command, control the optical path switching mechanism to switch the heating optical path corresponding to the target heating mode into the working optical axis; wherein, the point heating mode corresponds to the point heating optical path, and the surface heating mode corresponds to the surface heating optical path. S30. In response to the switching command and / or the received user input, a spot-changing command carrying the target spot size is generated, and according to the spot-changing command and the preset mapping relationship, the displacement actuator is controlled to drive the collimation module in the corresponding heating optical path to move along the optical axis to the target displacement amount, so as to change the laser beam parameters incident on the total internal reflection integrating mirror of the corresponding mode; wherein, the collimation module includes a point heating collimation module and a surface heating collimation module, which correspond to the point heating optical path and the surface heating optical path, respectively; S40. The laser beam is sequentially passed through the total internal reflection integrating mirror and the freeform surface homogenizing mirror for homogenization and decoherence processing, generating a homogenized spot with the target spot size in the target area; wherein, in the point heating mode, the total internal reflection integrating mirror is a point-heated total internal reflection integrating mirror group, which consists of two one-dimensional microcylindrical array mirrors arranged orthogonally to each other; in the surface heating mode, the total internal reflection integrating mirror is a surface-heated total internal reflection integrating mirror, which is a single two-dimensional microcylindrical array mirror; S50. Obtain the spot heat flux distribution data of the target area through the detection module; S60. Input the heat flow distribution data of the light spot into the optimization algorithm model, and iteratively calculate the displacement compensation amount of the collimation module; S70. Control the displacement actuator to finely adjust the axial position of the collimation module along the optical axis according to the displacement compensation amount, so as to compensate the uniformity of the light spot to above a preset threshold.

2. The method according to claim 1, characterized in that, When the target heating mode is a point heating mode, step S40 specifically includes: The laser beam is collimated using a point-heated collimation module consisting of an off-axis parabolic mirror and an achromatic lens group; The collimated laser beam is sequentially passed through two one-dimensional microcylindrical array mirrors in the point-heated total internal reflection integrating mirror group to perform beam splitting and homogenization in the horizontal and vertical directions, respectively, forming an initial rectangular flat-top distribution beam. The initial rectangular flat-top distributed beam continues to pass through the first freeform surface homogenizing lens, and secondary homogenization and decoherence processing are performed to generate a rectangular uniform light spot in the target area.

3. The method according to claim 1, characterized in that, When the target heating mode is a surface heating mode, step S40 specifically includes: The laser beam is collimated using a surface heating collimation module; The collimated laser beam is homogenized in two dimensions by passing it through the surface-heated total internal reflection integrator. The two-dimensional micro-cylindrical array of the surface-heated total internal reflection integrator is directly fabricated on the same substrate. The homogenized beam is then passed through the second freeform surface homogenizing lens for a second homogenization process, generating a rectangular uniform light spot in the target area.

4. The method according to claim 2 or 3, characterized in that, It also includes the step of thermal management of the total internal reflection integrating mirror: Forced convection heat transfer is achieved by driving the cooling medium through a conformal microchannel liquid cooling circuit located on the back of the total reflection integrator, thereby controlling the temperature rise of the total reflection integrator, maintaining its surface shape accuracy, and thus maintaining the stability of the light spot uniformity.

5. The method according to claim 1, characterized in that, The preset mapping relationship includes: In point heating mode, a first correspondence between multiple typical spot sizes and the first displacement range of the point heating collimation module; In surface heating mode, a second correspondence exists between multiple typical spot sizes and the second displacement range of the surface heating collimation module; The collimation module is driven to move within a corresponding displacement range by the displacement actuator, thereby enabling rapid switching of the light spot size without replacing the external lens.

6. A dual-mode laser heating spot homogenization control system, used to implement the method according to any one of claims 1 to 5, characterized in that, include: The point heating optical path module includes a first laser source, a first optical fiber, a point heating collimation module, a point heating total internal reflection integrating mirror group, and a first freeform surface homogenizing mirror. The point heating total internal reflection integrating mirror group is composed of two mirrors with a one-dimensional microcylindrical array on their surfaces arranged orthogonally. The surface-heated optical path module includes a second laser source, a second optical fiber, a surface-heated collimation module, a surface-heated total internal reflection integrating mirror, and a second free-form surface homogenizing mirror. The surface-heated total internal reflection integrating mirror is a single-piece mirror with a two-dimensional micro-cylindrical array on its surface. The optical path switching mechanism is used to respond to a switching command and switch the point heating optical path module or the surface heating optical path module into the working optical axis; A displacement actuator is driven and connected to the point heating collimation module and / or the surface heating collimation module, and is used to drive the corresponding collimation module to move along the optical axis; The detection module is used to acquire the spot heat flux distribution data of the target area; The control module is communicatively connected to the optical path switching mechanism, the displacement actuator, and the detection module, respectively. The control module is configured to: receive a switching command and a spot-changing command generated based on the switching command and / or user input; control the optical path switching mechanism to operate according to the switching command; control the displacement actuator to drive the corresponding collimation module to move to the target displacement amount according to the spot-changing command and the stored mapping relationship between the spot size and the collimation module displacement; receive the spot heat flux distribution data and run an optimization algorithm model to calculate the displacement compensation amount; and control the displacement actuator to fine-tune the axial position of the collimation module according to the displacement compensation amount.

7. The system according to claim 6, characterized in that, The point heating collimation module in the point heating optical path module includes an off-axis parabolic reflector and an achromatic lens group; the two one-dimensional microcylindrical array reflectors in the point heating total internal reflection integrating mirror group are used to homogenize the laser beam in the horizontal and vertical directions, respectively.

8. The system according to claim 6, characterized in that, The surface-heated total internal reflection integrating mirror in the surface-heated optical path module is a single two-dimensional microcylindrical array mirror, which is directly processed on the same metal substrate.

9. The system according to claim 6, characterized in that, It also includes liquid cooling heat dissipation devices; The liquid cooling device includes a conformal microchannel liquid cooling circuit disposed on the back of the point-heated total internal reflection integrator and the surface-heated total internal reflection integrator, and a circulating cooling unit connected to the liquid cooling circuit, for forced cooling of the corresponding total internal reflection integrator to control its operating temperature rise.

10. The system according to claim 6, characterized in that, The displacement actuator includes a high-rigidity linear displacement stage driven by a linear motor and an absolute position encoder; the optical path switching mechanism is a six-axis servo adjustment frame.

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