Anti-return high-power fiber laser device and method

Abstract

The invention provides an anti-return high-power fiber laser device, and the device is characterized in that a workpiece state detection module detects the state of a machining region of a workpiece; the regulation and control module sets machining parameters based on the state detected by the workpiece state detection module; the laser module generates auxiliary laser and main laser according to the machining parameters and adjusts the output power of the auxiliary laser and the output power of the main laser, the auxiliary laser is used for preheating and / or surface melting of a machining area, and the main laser is used for deep machining of the machining area; when the workpiece state inspection module detects that the processing area is not melted, the regulation and control module reduces the output power of the main laser; and when the workpiece state inspection module detects that the machining area is melted, the regulation and control module increases the output power of the main laser. Through deep integration of the overall structure and functions, efficient laser output and reduction of loss of returned light to the laser are both considered.

Description

Technical Field

[0001] The present invention relates to the field of high-power lasers, and more specifically, to an anti-reflection high-power fiber laser device and method. Background Art

[0002] Infrared laser (wavelength 1050-1080nm) is one of the wavelengths widely used in the field of laser metal processing due to its high metal absorption rate. Lasers of this wavelength can penetrate metals more deeply and are suitable for deep processing and high-efficiency processing. However, at room temperature, most metal materials exist in solid form, and their reflectivity to infrared lasers is higher than that of blue light (420-470nm) or green light (532nm). For example, from Figure 6b It can be seen that the reflectivity of many metals to 1064nm infrared laser is significantly higher than that of blue light or green light. Figure 6a As shown, the absorption rate of blue light by many metals is significantly higher than that of infrared lasers.

[0003] When the surface of a high reflectivity material (gold, silver, copper, aluminum, etc.) is heated to melt and becomes liquid, its absorption rate of infrared laser will increase significantly, such as Figure 7 As shown (taking metal copper (Cu) as an example). Figure 7 The following is the absorption rate curve of copper to infrared laser (wavelength 1030-1080nm) at different temperatures. At room temperature, copper has a low absorption rate to infrared laser, but as the temperature rises and approaches the melting point (1084.62℃, about 1357.77K), the absorption rate will increase significantly, and it is easier to absorb infrared laser energy.

[0004] Therefore, in order to process high-reflectivity metal materials more efficiently, the workpiece surface is usually preheated with blue light (420-470 nanometers) before using infrared lasers. Blue light has a shorter wavelength and higher photon energy, and its absorption rate is higher in solid metal materials at room temperature, so it can quickly heat the material surface to melt and form a molten pool. The formation of the molten pool reduces the surface reflectivity and increases the absorption efficiency of the infrared laser, and then the infrared laser is used to deeply process the molten pool. This processing flow combines the high efficiency of blue light preheating and the deep processing capability of infrared lasers, thereby achieving high-quality processing of high-reflectivity metal materials.

[0005] However, in the existing technology, the power of infrared laser and blue laser is usually fixed and cannot be dynamically adjusted according to the real-time status of the processing area (such as the reflectivity of the return light and the temperature change of the workpiece). This deficiency is particularly obvious during the processing, especially during the transformation of the workpiece from solid to liquid, the reasonable allocation of the two laser powers and the dynamic adjustment of the output time are particularly important.

[0006] Due to the lack of a dynamic adjustment mechanism, the laser utilization rate in the prior art is low, and the power of infrared lasers and blue lasers cannot be flexibly allocated according to processing requirements, resulting in unnecessary energy waste. During the processing, the reflected light in the high reflectivity area may be reflected back to the laser and enter the laser source system, thereby damaging the laser and reducing its life and reliability. The lack of optimization of the two laser power distributions before and after melting makes it impossible to achieve a balance between efficiency and quality in the processing process. To this end, the present invention proposes a technical solution that can adjust the appropriate laser power in the current state in real time according to the reflectivity of the reflected light and temperature feedback in the processing area, thereby improving the laser utilization rate and reducing equipment loss.

[0007] Comparative analysis of existing technologies:

[0008] Patent application number 202110860411.8: It mainly uses a blue laser to preheat the area around the focus of the pump laser processing, with the aim of reducing the temperature difference between the focus area and the surrounding area to avoid splashing during processing. However, this technology fails to dynamically adjust the power of the auxiliary laser and the pump laser based on the real-time status of the processing area (such as the reflectivity and temperature of the returned light).

[0009] Patent application number 202310187916.1: The spot energy of the fiber-blue light semiconductor composite laser is offset to achieve intelligent matching of different energies of the composite laser on dissimilar materials, and intelligently adjust the energy distribution ratio by real-time monitoring of the weld morphology and temperature feedback. By improving the intelligent distribution of laser energy on both sides of the parent material, the thickness of the intermetallic compound reaction layer is effectively reduced, the connection strength is improved, and high-quality welding of dissimilar materials is achieved. Although this technology achieves the adjustment of the energy distribution of the composite laser for different materials, it fails to adjust the energy distribution between the fiber laser and the blue light semiconductor laser in the composite laser, and does not propose a processing method for a single workpiece material.

[0010] Patent application number 202410478258.6: does not involve the technical content of real-time adjustment of laser energy distribution based on the reflected light reflectivity and temperature feedback of the processing area.

[0011] In addition, current existing technologies usually only support assembly line processing of workpieces of the same material. If the processing material or processing requirements need to be switched, the laser parameters must be manually adjusted. Existing technologies are still unable to automatically identify the workpiece material and automatically set the optimal power configuration of infrared laser and blue laser according to the material characteristics, thus affecting processing efficiency and flexibility.

[0012] The present invention proposes a technical solution for real-time adjustment of the power distribution of infrared laser and blue laser based on the reflected light reflectivity and temperature feedback of the processing area. This solution not only solves the problem of laser energy waste and equipment loss, but also can automatically identify the workpiece material, dynamically optimize the laser parameter configuration, and significantly improve the processing efficiency and quality. Summary of the invention

[0013] The present invention provides an anti-return high-power fiber laser device and method, which can take into account both efficient laser utilization and reduced loss of laser core components caused by return light.

[0014] In a first aspect, the present invention provides an anti-return high-power fiber laser device, which includes a control module, a laser module, and a workpiece status inspection module;

[0015] The workpiece status inspection module detects the status of the processing area of ​​the workpiece;

[0016] The control module sets the processing parameters based on the state detected by the workpiece state inspection module;

[0017] The laser module generates an auxiliary laser and a main laser according to the processing parameters and adjusts the output power of the auxiliary laser and the main laser, wherein the auxiliary laser is used for preheating and / or surface melting of the processing area, and the main laser is used for deep processing of the processing area;

[0018] When the workpiece state inspection module detects that the processing area is not melted, the control module lowers the output power of the main laser;

[0019] When the workpiece state inspection module detects that the processing area is melted, the control module increases the output power of the main laser.

[0020] In a second aspect, the present invention provides a method for anti-reflection of a high-power fiber laser, comprising:

[0021] Detect the status of the processing area of ​​the workpiece;

[0022] Setting processing parameters based on the state of the processing area;

[0023] The laser generates an auxiliary laser and a main laser according to the processing parameters and adjusts the output power of the auxiliary laser and the main laser, wherein the auxiliary laser is used for preheating and / or surface melting of the processing area, and the main laser is used for deep processing of the processing area;

[0024] When the processing area is not melted, lowering the output power of the main laser;

[0025] When melting occurs in the processing area, the output power of the main laser is increased.

[0026] The beneficial technical effects of the present invention are:

[0027] 1. Spatially coupled semiconductor chips reduce the size of the pump source;

[0028] 2. The accuracy of automatically identifying the type of workpiece material and judging the state of the processing area is improved based on the reflectivity of the returned light in the processing area of ​​the workpiece.

[0029] 3. Real-time control of laser output based on the state of the processing area improves the efficient use of lasers, ensures the stability of the processing process and results, and reduces the damage of returned light to the laser.

[0030] 4. The addition of the cladding light stripper effectively strips away excess pump light and return light, further improving the stability and processing efficiency of the laser. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0032] Figure 1 A schematic diagram of an anti-return high-power fiber laser device provided by the present invention;

[0033] Figure 2 A schematic diagram of a control module provided by the present invention;

[0034] Figure 3 A schematic diagram of a laser module provided by the present invention;

[0035] Figure 4 A schematic diagram of a cladding light stripper provided by the present invention;

[0036] Figure 5 A flow chart of an anti-return high-power fiber laser method provided by the present invention;

[0037] Figure 6a and 6b These are the curves of the absorptivity and reflectivity of different metal materials to light of different wavelengths at room temperature;

[0038] Figure 7 This is the absorption rate curve of copper to infrared laser (wavelength is 1050~1080nm) at different temperatures;

[0039] Figure 8 The absorption and emission curves of ytterbium-doped gain fiber for light of different wavelengths. DETAILED DESCRIPTION

[0040] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. SUMMARY OF THE INVENTION

[0042] The present invention provides an efficient laser processing system device, in which the control module and the workpiece status inspection module cooperate with each other, automatically identify the material type of the workpiece according to the reflectivity of the main laser return light and temperature feedback, and dynamically adjust the output power of the laser module, which not only improves the efficiency and quality of laser processing, but also reduces resource waste and prolongs the service life of the module. Through the deep integration of the overall structure and functions, it takes into account both efficient laser output and reducing the loss of the return light to the laser.

[0043] Exemplary Devices

[0044] like Figure 1 The high-power laser provided by the present invention shown includes a control module 1, a laser module 2, and a workpiece state inspection module 3.

[0045] The workpiece status inspection module 3 also includes a temperature detection module 3-1 and a return light detection module 3-2. The temperature detection module 3-1 is used to detect the temperature of the workpiece processing area, and the return light detection module 3-2 is used to detect the reflectivity of the main laser in the return light of the processing area. The two modules perform real-time detection throughout the process and continuously feed back the detection data to the control module 1.

[0046] like Figure 2 As shown, the control module 1 also includes:

[0047] Material database 1-1, used to store reflectivity data of common materials at different temperatures, especially reflectivity data near the melting point;

[0048] The material identification unit 1-2 is used to compare the workpiece surface temperature measured by the temperature detection module 3-1 and the reflectivity data measured by the return light detection module 3-2 with the material characteristics in the material database, and match the closest material type according to the characteristic curve of reflectivity changing with temperature;

[0049] Parameter adjustment unit 1-3, used to determine initial processing parameters based on workpiece material type and processing requirements (such as cutting or welding), and adjust processing parameters based on temperature and reflectivity of main laser return light and feed back to laser module 2;

[0050] The melting judgment unit 1-4 is used to judge whether the processing area of ​​the workpiece is melted.

[0051] In the present invention, the laser module 2 outputs a composite laser, which mainly includes an auxiliary laser and a main laser. The main laser is an infrared fiber laser output with a wavelength of 1050 to 1080 nm and an output beam diameter of 50 to 200 μm; the auxiliary laser is a blue laser output by a blue semiconductor laser with a wavelength of 420 to 470 nm and an output beam diameter of 300 to 500 μm. The auxiliary laser is used to heat the surface of the workpiece to provide uniform preheating; the main laser is used to deeply process the workpiece and perform fine deep melting and cutting. The laser head of the laser module 2 first outputs a high-power auxiliary laser to preheat the target area of ​​the workpiece, so that the temperature of the processing area gradually increases and enters the preheating stage. In this stage, in addition to the high-power auxiliary laser, the laser will also simultaneously output a lower-power main laser and the auxiliary laser to irradiate the processing area. In the preheating stage of this embodiment, the auxiliary laser accounts for 70%-90% of the total output power, and the main laser accounts for 10%-30% of the total output power.

[0052] The reason why the auxiliary laser power output is high and the main laser power is low during the preheating stage is that for most metal materials, the absorption rate of blue light is much greater than the absorption rate of infrared light at room temperature or below the melting point (see Figure 6a ), so in the preheating stage, it is necessary to increase the power of the auxiliary laser (blue light) to heat the metal surface quickly and then melt it. Before melting, the metal has a low absorption rate for infrared light and a high reflectivity (see Figure 6a and 6b ), therefore, reducing the power of the infrared laser during the preheating stage can effectively reduce the damage of the returning light to the laser and achieve a higher total laser output power.

[0053] In order to ensure accurate control of the temperature of the processing area, the temperature detection module 3-1 and the return light detection module 3-2 monitor the temperature of the processing area and the reflectivity of the main laser in the return light in real time, and feed the data back to the control module 1. The control module 1 evaluates the state of the processing area and adjusts the processing parameters of the laser based on the real-time data of temperature changes and return light reflectivity. The laser module 2 is controlled to output the corresponding laser based on the processing parameters. Through these dynamic adjustments, the control module 1 can effectively control the preheating rate, avoid excessive preheating time, and thus avoid reducing the processing efficiency.

[0054] Once the control module 1 determines based on the temperature and reflectivity that the surface of the processing area has melted and a molten pool has been formed, the surface melting stage is entered. At this stage, the control module 1 controls the laser module 2 to significantly increase the output power of the main laser to enhance the processing effect, while reducing the power output of the auxiliary laser. At this time, the main laser will perform deep and fine processing on the workpiece based on the molten pool, and the auxiliary laser is used to assist in maintaining the stability of the molten pool. In the surface melting stage of this embodiment, the main laser accounts for 70%-90% of the initial total output power, and the auxiliary laser accounts for 10%-30% of the initial total output power. Since the beam of the auxiliary laser is larger than that of the main laser, the larger surface molten pool helps to reduce the splashing effect caused by the in-depth processing of the main laser.

[0055] The temperature detection module 3-1 and the return light detection module 3-2 continuously monitor the temperature of the molten pool and the reflectivity of the return light of the main laser to ensure that the molten pool is in a stable state. The control module 1 adjusts the laser output in real time based on the feedback data to prevent the molten pool from overheating and causing gasification or the generation of impurity compounds, which will affect the quality of processing.

[0056] When the laser head of the laser module 2 irradiates the processing area of ​​the workpiece, part of the laser is reflected by the surface of the processing area and returns to the laser head along the original laser path. This part of the laser is the return light. Since the absorption rate of metal materials for infrared lasers will change greatly near the melting point (see Figure 7 ), so the reflectivity of the main laser can be calculated by detecting the return light of the main laser to determine whether the metal material is melted. The return light detection module 3-2 detects and calculates the reflectivity of the main laser in the return light, rather than calculating the reflectivity of the auxiliary laser in the return light.

[0057] The return light detection module 3-2 is integrated with the laser head of the laser module 2 and installed in one piece (i.e., the laser output position), so that no matter at what angle the laser head of the laser module 2 irradiates the processing area of ​​the workpiece, the return light detection module 3-2 can detect the reflectivity of the return light main laser. In addition, the return light detection module 3-2 can also be installed on the side of the laser path of the main laser and the auxiliary laser, using a spectrometer or a reflector to separate the main laser return light from the optical path, and guide the return light to the inside of the return light detection module 3-2. Compared with the two installation positions, the laser head directly integrated in the laser module 2 can directly utilize the existing laser system device. However, installation on the side of the optical path may require additional design of a complex optical path, which increases the cost and design difficulty.

[0058] The present invention installs a wavelength selective filter in the return light detection module 3-2 to filter out the auxiliary laser in the return light and only allow the main laser in the return light to pass. In addition, since the return light is consistent with the original composite laser path, an optical isolator is also used to separate the main laser return light and guide it to the return light detection module 3-2. The return light detection module 3-2 obtains the reflectivity of the main laser return light by calculating the ratio of the light intensity of the return light main laser to the light intensity of the main laser output by the laser module 2.

[0059] The reason why the present invention detects the reflectivity of the returned light instead of detecting other reflected path lasers is as follows: the returned light completely corresponds to the path of the laser incident on the workpiece processing area, and can directly reflect the optical properties (reflectivity) of the processing area. Once the surface of the processing area melts from a solid state to a liquid state, the reflectivity of the returned light will change significantly, which can quickly reflect this transformation process in real time. During the laser processing process, slag and smoke may be generated on the surface of the workpiece. These factors will scatter the laser and cause the reflection path of other lasers to become complicated. If relying on lasers of other reflected paths, the control module 1 may be disturbed, making it difficult to quickly and accurately judge the state change of the processing area. In addition, the detection based on the returned light can directly utilize the existing laser system device, and the returned light detection module 3-2 is directly integrated in the laser head of the laser module 2. Other reflected paths may require additional complex optical paths to capture reflected light from other directions, which increases the cost and design difficulty.

[0060] The device of the present invention can automatically identify the material type of the workpiece to be processed (such as copper, iron, aluminum, ceramic, glass, etc.), so that the control module 1 can preliminarily set the initial processing parameters of the preheating stage and the surface melting stage according to the material type and specific processing requirements, and at the same time provide a basis for the dynamic parameter adjustment of each stage.

[0061] Material identification and initial parameter setting process:

[0062] The control module 1 integrates a material database, which stores the reflectivity characteristics of the return light of common workpiece materials under different temperatures, different wavelengths of lasers, and different incident angles, especially the reflectivity characteristics when close to the melting point. This database is a key tool for material identification, and by comparing the characteristic data, it can accurately match the material type.

[0063] After the workpiece is fixed and before preheating begins, the control module 1 controls the laser module 2 to output a single laser beam of appropriate wavelength (such as 1064nm laser) and irradiate the workpiece surface at a vertical angle (0° incidence). The return light detection module 3-2 measures the reflectivity data of the return light in real time and feeds the data back to the control module 1.

[0064] The laser module 2 then adjusts the laser incident angle (such as 15°, 30°), records the reflected light reflectivity under different incident angles, and forms a set of reflectivity characteristic parameters. These parameters are compared with the reflectivity characteristic curve in the material database to preliminarily identify the material type of the workpiece.

[0065] If multiple materials with similar reflectivity characteristics are found in the preliminary identification stage, the control module 1 will control the laser module 2 to switch the wavelength of the laser (such as switching to 532nm or 1550nm), repeat the above angle test process, and record the reflectivity characteristics under the new wavelength conditions to further narrow the range of candidate materials and ultimately determine the unique material type.

[0066] After the material type is determined, the control module 1 preliminarily sets the initial processing parameters of the preheating stage and the surface melting stage according to the identification results. The initial processing parameters of the preheating stage are transmitted to the laser module 2, and the composite laser is output to start preheating.

[0067] As the temperature of the processing area gradually increases, the reflected light detection module 3-2 will record the reflectivity changes under various temperature conditions in real time. The control module 1 combines these data and compares and analyzes the reflected light reflectivity data recorded under different laser wavelengths and incident angles before preheating to further verify the accuracy of the material identification results or correct possible identification deviations, and dynamically optimize and adjust the processing parameters accordingly.

[0068] When the temperature of the processing area approaches the melting point of the material, the surface begins to melt and the processing enters the surface melting stage. At this time, the reflectivity of the return light of the main laser changes significantly, and the control module 1 is most likely to further accurately identify the material type of the workpiece based on the reflectivity. If the material type of the workpiece has not changed, the control module 1 continues to use the initial processing parameters of the surface melting stage to guide the subsequent processing process. If the material type changes, the control module 1 will re-correct the processing parameters to ensure that the processing process is adapted to the characteristics of the new material.

[0069] In other optimized embodiments, a scattered laser analysis module is also provided to further detect the data of scattered light intensity and distribution characteristics caused by the laser on the surface of the processing area of ​​the workpiece, and feed it back to the control module 1. The control module 1 further determines the material type of the workpiece in combination with the aforementioned reflected light reflectivity data.

[0070] After the control module 1 accurately identifies the material type of the workpiece, it preliminarily sets the initial processing parameters of the preheating stage and the surface melting stage and the conditions for optimizing and adjusting the processing parameters according to specific processing requirements (such as deep processing, surface treatment, or complex shape processing, etc.).

[0071] The processing parameters of each stage set by the control module 1 include: at least one of the total output power of the main laser and the auxiliary laser, power ratio, laser scanning speed, pulse width, pulse frequency, peak power, incident angle, average power and duty cycle.

[0072] The conditions for optimizing and adjusting the processing parameters include: a first threshold indicating the minimum temperature change rate in the preheating stage, a maximum preheating time, a second threshold used to determine whether to enter the surface melting stage through the rate of change of the reflected light reflectivity, a reflected light reflectivity-temperature curve related to the workpiece material type, and a target temperature range for the processing area in the surface melting stage.

[0073] The control module 1 accesses historical processing data, which contains the optimal processing parameters for the same or similar materials under different processing requirements. The historical data also records common problems that occur during the processing (such as overheating, gasification or unstable molten pool), as well as the corresponding parameter adjustment strategies, providing a reference for dynamically optimizing and adjusting the processing parameters during the two stages. In addition, the control module 1 collects relevant information about the current processing environment, such as the initial temperature of the workpiece, the ambient temperature and humidity, the performance status of the laser module 2, etc., which have a direct impact on the energy transfer and thermal effect during the processing. After comprehensively considering the material type, processing requirements, historical data and environmental factors, the control module 1 uses an optimization algorithm to calculate the initial processing parameters of each stage to ensure the balance between efficiency and processing quality in each stage (preheating stage and surface melting stage). The control module 1 will generate the best initial processing parameters and transmit them to the laser module 2 as the initial processing parameters for the preheating stage and the surface melting stage.

[0074] By combining material type, processing requirements, historical processing data and real-time environmental factors, the control module 1 can not only set the initial processing parameters for each stage, ensuring that the processing is run in an efficient and stable manner when it starts, reducing debugging time and resource waste. At the same time, it can also provide judgment basis and corresponding adjustment strategies for the subsequent dynamic adjustment of processing parameters, thereby improving the stability of processing implementation. This comprehensive optimization strategy can significantly improve processing efficiency, ensure the stability of processing quality, and effectively reduce processing defects caused by improper parameter settings.

[0075] The laser module 2 first outputs the auxiliary laser and the main laser based on the initial processing parameters of the preheating stage to preheat the processing area of ​​the workpiece. During the preheating process, the control module 1 monitors the temperature change rate of the processing area in real time to determine whether it is lower than the first threshold value set. If the temperature change rate is lower than the threshold, it indicates that the auxiliary laser power may be too low, the laser scanning speed is too fast, or other reasons lead to insufficient temperature rise. At this time, the control module 1 increases the output power of the auxiliary laser, reduces the laser scanning speed, increases the laser duty cycle, or adjusts other processing parameters to increase the heating rate.

[0076] At the same time, the control module 1 also calculates the reflectivity change rate based on the real-time detection results of the reflected light reflectivity, and generates an actual temperature-returned light reflectivity curve. The control module 1 monitors whether the reflectivity change rate exceeds the preset second threshold, or determines the characteristics of the reflected light reflectivity-temperature curve, and identifies whether a significant change inflection point occurs. Usually, when the workpiece approaches the melting point of its material, the reflected light reflectivity will drop rapidly and tend to stabilize, forming a significant "inflection point". When the reflectivity curve changes from a slow decline to a rapid decline, and stabilizes near a certain value, it indicates that the processing area is close to the melting point, and the reflected light reflectivity changes significantly. If the change rate of the reflected light reflectivity exceeds the threshold and identifies the inflection point, the control module 1 determines that the processing area of ​​the workpiece has entered the surface melting stage, and the preheating stage ends.

[0077] In addition, the control module 1 also determines whether the preheating time exceeds the set maximum preheating time. If within the maximum preheating time, the control module 1 detects that the processing area enters the surface melting stage, the control module 1 compares the actual reflected light reflectivity-temperature curve with the reflected light reflectivity-temperature curve corresponding to the workpiece material type in the material database to verify whether the workpiece material type automatically judged before preheating is correct. If the material type is determined incorrectly, the control module 1 will re-search the material that matches the actual reflected light reflectivity-temperature curve in the material database, and update the processing parameters and target temperature range of the surface melting stage according to the new material type. At this time, the control module 1 discards the original parameter data and saves the updated parameter data, and sends the updated processing parameters to the laser module 2. If the material type is correct, the control module 1 directly sends the initial processing parameters of the surface melting stage set before preheating to the laser module 2.

[0078] When the preheating time exceeds the set maximum preheating time, but the control module 1 has not yet detected the surface melting stage, the control module 1 will discard the original initial processing parameters of the surface melting stage and take the following measures to accelerate the temperature rise: increase the output power of the auxiliary laser, reduce the laser scanning speed, or adjust other processing parameters to increase the rate of temperature rise in the processing area. Once the processing area is detected to enter the surface melting stage, the control module 1 will reconfirm the workpiece material type based on the actual generated return light reflectivity change rate-temperature curve, and update the processing parameters and target temperature range.

[0079] When entering the surface melting stage, the processing area melts from solid to liquid to form a molten pool. At this time, the control module 1 will determine in real time whether the molten pool temperature is within the latest set target temperature range. If the temperature exceeds the target range, the control module 1 will take the following measures to reduce the molten pool temperature: increase the laser scanning speed, reduce the laser duty cycle, or reduce the power of the main laser and / or auxiliary laser.

[0080] If the molten pool temperature is lower than the target range, the control module 1 will increase the main laser power, reduce the scanning speed, increase the duty cycle, or adjust other processing parameters to increase the molten pool temperature.

[0081] In addition, during the surface melting stage, the control module 1 will also continuously monitor the reflected light reflectivity to ensure that it is consistent with the stored reflected light reflectivity-temperature curve. If an abnormality is found, the control module 1 will readjust the processing parameters. If the abnormality still exists after the adjustment, the system will issue an alarm to prompt the operator to intervene manually, and the operator will manually confirm the problem and enter new processing parameters. The control module 1 will save the manually entered parameter data and abnormal data for AI learning for subsequent reference.

[0082] In summary, through the above, this embodiment can monitor the changes in temperature and return light reflectivity in the processing area throughout the entire process to automatically identify the material type of the workpiece and confirm the corresponding laser processing parameters, and during the processing process, correct the workpiece material judgment and continuously adjust the processing parameters according to the actual situation to ensure the efficiency and stability of the workpiece processing process.

[0083] In this embodiment, the laser module 2 includes a series of key components connected in sequence, such as Figure 3 As shown: semiconductor pump source 2-1, high reflection grating 2-2, ytterbium-doped gain fiber 2-3, low reflection grating 2-4, cladding light stripper 2-5 and transmission fiber 2-6. These components work together to ensure the generation, modulation, transmission and final output of laser.

[0084] The semiconductor pump source 2-1 is the core part of the laser module 2, and includes three semiconductor chips with different wavelengths, which are used to output auxiliary laser, pump light and indicator light respectively. The number of semiconductor chips with three wavelengths is at least one in the semiconductor pump source 2-1.

[0085] Blue light semiconductor chip with a wavelength of 420-470nm: used to output auxiliary laser.

[0086] 650nm wavelength red light semiconductor chip: outputs indicator light to facilitate positioning and alignment of the processing area.

[0087] Pump light semiconductor chip with a wavelength of 915nm or 976nm: used to output pump light that provides excitation energy for the ytterbium-doped gain fiber, through which the pump light is converted into the main laser.

[0088] The semiconductor pump source 2-1 has three positive and negative pins on the outside, which control the light output of the three wavelength semiconductor chips respectively. It changes the power of the laser output by the semiconductor chip of the corresponding wavelength by changing the voltage and current input to the positive and negative pins.

[0089] In another embodiment of the present invention, the output power of the corresponding laser (indicator light, auxiliary laser and pump light) can also be controlled by controlling the number of semiconductor chips of each wavelength.

[0090] Inside the semiconductor pump source 2-1, each semiconductor chip has a corresponding high reflectivity reflector to form a combination. Each semiconductor chip and reflector combination is arranged in a stepped manner, that is, arranged in layers in the direction of the light path, and each group of light paths moves up or down layer by layer. The laser emitted by each semiconductor chip guides the beam propagation direction to the focusing lens or reflector through its corresponding high reflectivity plane mirror, forming parallel light composed of multiple beams.

[0091] The reflectors corresponding to the 420-470nm blue light semiconductor chip and the 650nm red light semiconductor chip guide and reflect the auxiliary laser and the indicator light to the central area of ​​the parallel light. The reflectors corresponding to the 915nm or 976nm pump light semiconductor chip guide and reflect the pump light to the peripheral area of ​​the parallel light.

[0092] Finally, the parallel light composed of multiple light beams is focused and coupled into the output optical fiber of the semiconductor pump source through a focusing lens group or a reflector, wherein the input end of the output optical fiber of the semiconductor pump source is an end cap.

[0093] If the output fiber of the semiconductor pump source is a double-layer structure, having only a cladding and a core, the focusing lens couples the pump light, auxiliary laser and indicator light in the parallel light into its cladding. If the output fiber of the semiconductor pump source is a three-layer structure, having an outer cladding, an inner cladding and a core. Then the auxiliary laser and indicator light are coupled into the inner cladding of the output fiber through the focusing lens, and the pump light is also coupled into the inner cladding of the output fiber. The output fiber of the semiconductor pump source transmits the light beam to the gain fiber 2-3 through the inner cladding.

[0094] In this embodiment, the pump light and the auxiliary laser are integrated into the semiconductor pump source 2 - 1 by spatial coupling, which saves the beam combiner and greatly reduces the overall volume.

[0095] In another embodiment of the present invention, the laser module 2 has a plurality of semiconductor pump sources 2-1, and the laser light is aggregated and transmitted to the gain fiber 2-3 by means of fiber combiner coupling or spatial coupling. In the gain fiber 2-3, the pump light with a wavelength of 915nm or 976nm is absorbed by the gain medium in the fiber core and converted into a main laser (infrared laser) with a wavelength of 1050-1080nm and transmitted in the fiber core. The main laser light is transmitted to the low-reflection grating 2-4 and is partially reflected and transmitted.

[0096] The high-reflection grating 2-2 is used to reflect the main laser back to the ytterbium-doped gain fiber 2-3. In this way, the main laser is repeatedly reflected and amplified in the ytterbium-doped gain fiber 2-3. The high-reflection grating 2-2 uses a reflection range near 1050 to 1080 nm, and the reflectivity is >99%.

[0097] Figure 8 The absorption (solid line) and emission (dashed line) spectra of the ytterbium-doped gain fiber for different wavelengths are shown. The ytterbium-doped gain fiber 2-3 absorbs the pump light of 915nm or 976nm wavelength, excites the ytterbium-doped ions to a high energy state, and then emits the main laser of 1050-1080nm and propagates in the fiber core. Figure 8 The absorption cross section (solid line) of the Y-axis in the figure represents the absorption capacity of doped ytterbium ions for photons of specific wavelengths, with peak values ​​at 915nm and 976nm, indicating that the pump light absorption efficiency of these wavelengths is the highest; the emission cross section (dashed line) of the Y-axis represents the radiation capacity of doped ytterbium ions for specific wavelengths, which is mainly concentrated in 1030-1080nm, among which 1050-1080nm is the working band of the main laser output.

[0098] The low-reflection grating 2-4 is used to control the output of the main laser, allowing a small part of the main laser to leak, forming a stable laser output. The low-reflection grating 2-3 uses a reflection range near 1050-1080nm, and the reflectivity is between 3%-30%.

[0099] After passing through the low-reflection grating, the laser enters the cladding light stripper 2-5, which has a three-layer structure of a core, an inner cladding and an outer cladding, such as Figure 4 It is used to strip the return light in the cladding and the excess pump light that is not absorbed by the ytterbium-doped gain fiber, ensuring the stable operation of the laser module 2.

[0100] The main laser light converted by the absorbed pump light is transmitted in the core of the cladding light stripper 2-5, and the excess pump light, auxiliary laser light, indicator light, and return light that are not absorbed are transmitted in the inner cladding of the cladding light stripper 2-5. However, the outer cladding of the cladding light stripper 2-5 has a special surface structure design, which can guide the excess pump light and return light in the inner cladding to the outer cladding for effective stripping and remove them from the system. The auxiliary laser light and indicator light will not be stripped, and will enter the inner cladding of the transmission optical fiber along the inner cladding of the cladding light stripper 2-5, while the main laser light will enter the core of the transmission optical fiber 2-6 along the core of the cladding light stripper 2-5.

[0101] The transmission optical fiber 2-6 transmits the main laser, the auxiliary laser and the indicator light to the quartz end cap at the tail end for final output. The spot of the main laser in the laser output through the quartz end cap at the tail end is smaller than that of the auxiliary laser.

[0102] In this embodiment, the NA value of the output end of the transmission optical fiber 2-6 is greater than or equal to the NA value of the input end. This is because if the NA value of the input end is small, the incident angle of the laser coming out of the cladding light stripper 2-5 can be limited, ensuring that only the core laser enters the transmission optical fiber 2-6 for transmission, and other light removed by the outer cladding of the cladding light stripper 2-5 does not enter the transmission optical fiber 2-6. At the same time, it is prevented that the core laser entering the transmission optical fiber 2-6 is diffused due to excessive transmission angle, and the laser light energy is not lost. The large NA value of the output end of the transmission optical fiber 2-6 allows a larger angle light beam to be emitted from the transmission optical fiber 2-6, ensuring that the laser can smoothly come out from the end of the optical fiber.

[0103] In this embodiment, the size of all optical fiber cores in the laser module 2 covers a range from 10 μm to 50 μm, and the size of the cladding covers a range from 125 μm to 1500 μm. In addition to the cladding light strippers 2-5, all optical fibers connecting components in the laser module 2 can be three layers or two layers. The main laser is transmitted in the optical fiber core, and the auxiliary laser and the indicator light are transmitted in the inner cladding.

[0104] In summary, the control module 1 of the present invention adjusts the output power of the laser module 2 in real time through the reflected light reflectivity and temperature parameters fed back by the workpiece status inspection module 3, so that the laser utilization rate in the processing process is significantly improved, and the waste of resources caused by excessive laser output is avoided, while also effectively reducing the generation of reflected light. The reflected light detection module 3-2 equipped in the system device can separate the reflected light and guide it to the inside of the reflected light detection module 3-2 to prevent it from flowing back to the laser module 2, and the cladding light stripper 2-5 in the laser module 2 further strips away the excess pump light and reflected light, thereby protecting the core components of the laser module 2 and improving its operating stability and life. The design of the overall laser device of the present invention not only improves the processing efficiency, but also significantly reduces the risk of loss of the laser module 2 due to the reflected light.

[0105] Exemplary Methods

[0106] Accordingly, an embodiment of the present invention also provides a method for preventing backscatter of a high-power fiber laser, such as Figure 5 shown, including:

[0107] S501: Detect the state of the processing area of ​​the workpiece.

[0108] S502: Setting processing parameters based on the state of the processing area.

[0109] S503: The laser generates an auxiliary laser and a main laser according to the processing parameters and adjusts the output power of the auxiliary laser and the main laser. The auxiliary laser is used to preheat and / or melt the surface of the processing area, and the main laser is used to perform deep processing on the processing area.

[0110] S504: When the processing area is not melted, lower the output power of the main laser.

[0111] S505: When melting occurs in the processing area, increase the output power of the main laser.

[0112] The status of the processing area includes:

[0113] The temperature of the processing area on the workpiece and / or the reflectivity of the main laser return light in the processing area.

[0114] Among them, before preheating the processing area, the workpiece is irradiated with lasers of different incident angles and / or different wavelengths; before preheating and just entering the surface melting stage, the reflectivity data of the main laser return light in the processing area is collected; by analyzing the reflectivity of the main laser return light or combining with the temperature detection module 3-1 to detect the temperature of the processing area on the workpiece, the specific material type of the workpiece is identified before preheating, and the identification result is corrected at the beginning of the surface melting stage.

[0115] The reflectivity data of common materials at different temperatures are stored in the material database, especially the reflectivity data near the melting point; the measured workpiece surface temperature and the reflectivity of the main laser return light are compared with the material properties in the material database, and the closest material type is matched according to the characteristic curve of the reflectivity changing with temperature.

[0116] Among them, according to the processing requirements and the material type of the workpiece identified before preheating, corresponding initial processing parameters are set for the preheating stage and the surface melting stage respectively, and the initial processing parameters of each stage include: total output power, laser scanning speed, power ratio of main laser to auxiliary laser, pulse width, pulse frequency, peak power, average power, and at least one of duty cycle.

[0117] Based on the temperature of the processing area and the reflectivity of the main laser return light, it is determined whether the processing area is currently in the preheating stage or the surface melting stage; at the beginning of the preheating stage, the laser outputs laser according to the initial processing parameters of the preheating stage to preheat the processing area of ​​the workpiece; at the beginning of the surface melting stage, the initial processing parameters of the surface melting stage are adjusted based on the workpiece material type correction result; in the process of each stage, the processing parameters are dynamically adjusted according to the real-time monitored processing area temperature and the reflectivity of the main laser return light, and fed back to the laser.

[0118] The conditions for adjusting the processing parameters are also determined based on the material type and processing requirements of the workpiece, and specifically include: a first threshold, a maximum preheating time, a second threshold, a return light reflectivity-temperature curve of the workpiece material, and a target temperature range of the processing area during the surface melting stage.

[0119] During the preheating stage, the auxiliary laser accounts for 70%-90% of the total output power; and the main laser accounts for 10%-30% of the total output power.

[0120] In the surface melting stage, the main laser accounts for 70%-90% of the total output power; the auxiliary laser accounts for 10%-30% of the total output power.

[0121] In the preheating stage, if the temperature change rate of the processing area is lower than the first threshold, or when the preheating time exceeds the initial preheating time and the surface melting stage has not been detected, the power of the auxiliary laser is increased or the scanning speed is reduced.

[0122] The judgment basis for the processing area entering the surface melting stage is: if the reflectivity change rate of the main laser return light exceeds the second threshold; or the actual change curve of the reflectivity and temperature of the main laser return light has a significant change inflection point.

[0123] The surface melting stage also includes the following steps: determining whether the temperature of the processing area exceeds the target temperature range; if it exceeds the target temperature range, simultaneously reducing the total power of the main laser and the auxiliary laser, increasing the scanning speed, and reducing the duty cycle of the pulse to avoid overheating and metal splashing; if it is lower than the target temperature range, increasing the power of the main laser, reducing the scanning speed, and increasing the duty cycle of the pulse.

[0124] The module for detecting the reflectivity of the return light of the main laser is installed on the side of the laser path of the main laser and the auxiliary laser, and the return light of the main laser is separated from the optical path by a beam splitter or a reflector; or the module for detecting the reflectivity of the return light of the main laser is installed at the output position of the main laser and the auxiliary laser, and the return light of the main laser is separated by an optical isolator; a wavelength selective filter is installed in the module for detecting the reflectivity of the return light of the main laser, and only the main laser in the return light is allowed to pass. The reflectivity is calculated by calculating the ratio of the main laser intensity to the main laser return light intensity.

[0125] The laser is provided with: a semiconductor pump source, a high-reflection grating, an ytterbium-doped gain fiber, a low-reflection grating, a cladding light stripper and a transmission fiber connected in sequence, wherein:

[0126] The semiconductor pump source outputs the auxiliary laser, pump light and indicator light;

[0127] The high-reflection grating reflects the main laser back to the ytterbium-doped gain fiber;

[0128] The ytterbium-doped gain optical fiber converts the pump light into a main laser and transmits the main laser in the core, and transmits the auxiliary laser and the indicator light in the inner cladding;

[0129] The low-reflection grating controls the output of the main laser;

[0130] The cladding light stripper strips the unabsorbed excess pump light and return light, and transmits the main laser, auxiliary laser and indicator light;

[0131] The transmission optical fiber transmits the main laser, auxiliary laser and indicator light to the quartz end cap at the rear end for final output.

[0132] The semiconductor pump source includes three wavelength semiconductor chips:

[0133] The auxiliary laser is output by a 420-470nm blue light semiconductor chip;

[0134] The 650nm red light semiconductor chip outputs the indicator light to facilitate positioning;

[0135] The 915nm or 976nm pump light semiconductor chip outputs the pump light;

[0136] The semiconductor pump source is externally controlled by three positive and negative pins to control the light output of the three wavelength semiconductor chips respectively; the light emitted by the three wavelength semiconductor chips is coupled into the output optical fiber of the semiconductor pump source through spatial light. The power of the laser output by the semiconductor chip in the laser is controlled by changing the voltage and current applied to the semiconductor pump source pins or changing the number of semiconductor chips outputting lasers.

[0137] The light emitted by the three wavelength semiconductor chips is coupled into the output optical fiber of the semiconductor pump source through spatial light, specifically including: the laser emitted by each semiconductor chip changes the propagation direction of the light beam through a high-reflectivity plane mirror to form parallel light composed of multiple light beams; each group of reflector combinations is arranged in a stepped manner, that is, arranged in layers in the direction of the light path, and each group of light paths moves up or down layer by layer; and each laser is focused and coupled into the output optical fiber of the semiconductor pump source through a focusing lens group or a reflector.

[0138] The reflectors corresponding to the 420-470nm blue light semiconductor chip and the 650nm red light semiconductor chip reflect the auxiliary laser and the indicator light to the central area of ​​the parallel light; the reflectors corresponding to the 915nm or 976nm pump light semiconductor chip reflect the pump light to the peripheral area of ​​the parallel light.

[0139] The output optical fiber of the semiconductor pump source is a triple-cladding laser, including a core, an inner cladding and an outer cladding. The step of focusing and coupling each laser into the output optical fiber of the semiconductor pump source through a focusing lens group further includes: coupling the auxiliary laser and the indicator light into the inner cladding of the output optical fiber through a focusing lens; and coupling the pump light into the inner cladding of the output optical fiber through a focusing lens.

[0140] The input end of the optical fiber connected to the semiconductor pump source is an end cap.

[0141] The high and low reflection gratings adopt a reflection range near 1050-1080nm, the reflectivity of the high reflection grating is greater than 99%, and the reflectivity of the low reflection grating is between 3% and 30%.

[0142] The laser has a plurality of semiconductor pump sources, and the laser light is collectively transmitted to the high-reflection grating by means of optical fiber coupling or spatial coupling.

[0143] The output optical fiber of the semiconductor pump source comprises a cladding and a core, and each laser is focused and coupled into the cladding of the output optical fiber of the semiconductor pump source through a focusing lens group or a reflector.

[0144] The NA value of the output end of the transmission optical fiber is greater than or equal to the NA value of the input end.

[0145] According to the material type and processing requirements of the workpiece being processed, combined with the corresponding historical processing data, the optimal parameters are obtained through comprehensive optimization and used as the initial processing parameters for each stage.

[0146] The spot of the main laser in the laser output through the quartz end cap at the tail end is smaller than that of the auxiliary laser.

[0147] The sizes of all optical fiber cores in the laser range from 10 μm to 50 μm, and the sizes of all optical fiber claddings range from 125 μm to 1500 μm.

[0148] Although the spirit and principle of the present invention have been described with reference to several specific embodiments, it should be understood that the present invention is not limited to the disclosed specific embodiments, and the division of various aspects does not mean that the features in these aspects cannot be combined to benefit, and such division is only for the convenience of expression. The present invention is intended to cover various modifications and equivalent arrangements included in the spirit and scope of the attached claims. The present invention provides: 1. An anti-return high-power fiber laser device, comprising a control module, a laser module, and a workpiece status inspection module; The workpiece status inspection module detects the status of the processing area of ​​the workpiece; The control module sets the processing parameters based on the state detected by the workpiece state inspection module; The laser module generates an auxiliary laser and a main laser according to the processing parameters and adjusts the output power of the auxiliary laser and the main laser, wherein the auxiliary laser is used for preheating and / or surface melting of the processing area, and the main laser is used for deep processing of the processing area; When the workpiece state inspection module detects that the processing area is not melted, the control module lowers the output power of the main laser; When the workpiece state inspection module detects that the processing area is melted, the control module increases the output power of the main laser. 2. According to the device described in item 1, the workpiece status inspection module 3 also includes: A temperature detection module, used to detect the temperature of the processing area on the workpiece throughout the entire process and feed back to the control module; and / or The return light detection module is used to detect the reflectivity of the main laser return light in the processing area throughout the entire process and feed it back to the control module. 3. The device according to item 2, wherein: The laser module irradiates the workpiece with lasers of different incident angles and / or wavelengths before preheating the processing area; The return light detection module collects the reflectivity data of the return light of the main laser in the processing area before preheating and just entering the surface melting stage, and feeds it back to the control module; The control module analyzes the reflectivity of the return light of the main laser or detects the temperature of the processing area on the workpiece in combination with the temperature detection module, thereby identifying the specific material type of the workpiece before preheating and correcting the identification result at the beginning of the surface melting stage. 4. The device according to item 2 or 3, wherein: The control module sets corresponding initial processing parameters for the preheating stage and the surface melting stage respectively according to the processing requirements and the material type of the workpiece identified before preheating, and the initial processing parameters of each stage include: at least one of the total output power, laser scanning speed, power ratio of the main laser and the auxiliary laser, pulse width, pulse frequency, peak power, average power, and duty cycle; The control module determines whether the processing area is currently in the preheating stage or the surface melting stage based on the feedback data of the temperature detection module and / or the return light detection module; At the beginning of the preheating stage, the laser module outputs laser according to the initial processing parameters of the preheating stage to preheat the processing area of ​​the workpiece; At the beginning of the surface melting stage, the control module adjusts the initial processing parameters of the surface melting stage based on the workpiece material type correction result and feeds back to the laser module; In the process of each stage, the control module dynamically adjusts the processing parameters according to the real-time monitored temperature of the processing area and the reflectivity of the return light of the main laser, and feeds back to the laser module. 5. The device according to item 4, wherein: The control module also determines the conditions for adjusting the processing parameters based on the material type and processing requirements of the workpiece, which specifically include: a first threshold, a maximum preheating time, a second threshold, a return light reflectivity-temperature curve of the workpiece material, and a target temperature range of the processing area during the surface melting stage. 6. The device according to item 4, wherein during the preheating stage, The auxiliary laser accounts for 70%-90% of the total output power; The main laser accounts for 10%-30% of the total output power. 7. The device according to item 4, wherein during the surface melting stage, The main laser accounts for 70%-90% of the total output power; The auxiliary laser accounts for 10%-30% of the total output power. 8. The device according to item 5, wherein: During the preheating stage, if the temperature change rate of the processing area is lower than the first threshold, or when the preheating time exceeds the initial preheating time and the surface melting stage has not yet been detected, the control module increases the power of the auxiliary laser or reduces the scanning speed, and feeds back to the laser module. 9. The device according to item 5, wherein: The basis for judging whether the processing area enters the surface melting stage is: If the reflectivity change rate of the main laser return light exceeds the second threshold; or The actual change curve of the reflectivity of the main laser return light and temperature shows a significant turning point. 10. According to the device described in item 5, during the surface melting stage, the control module is also used to: Determining whether the temperature of the processing area exceeds the target temperature range; If the target temperature range is exceeded, the total power of the main laser and the auxiliary laser is reduced, the scanning speed is increased, and the duty cycle of the pulse is reduced to avoid overheating and metal splashing; If the temperature is lower than the target temperature range, the power of the main laser is increased, the scanning speed is reduced, and the duty cycle of the pulse is increased. 11. The device according to item 2, wherein: The return light detection module is installed on the side of the laser path of the main laser and the auxiliary laser, and uses a beam splitter or a reflector to separate the return light of the main laser from the optical path, and guides the return light to the return light detection module; or The return light detection module is installed at the laser output position of the laser module, and uses an optical isolator to separate the main laser return light and guide it to the return light detection module; A wavelength selective filter is installed in the return light detection module to allow only the main laser in the return light to pass through. 12. The device according to item 11, wherein: The return light detection module calculates the reflectivity by calculating the ratio of the main laser intensity to the main laser return light intensity. 13. The device according to item 1, wherein the laser module further comprises: a semiconductor pump source, a high-reflection grating, an ytterbium-doped gain fiber, a low-reflection grating, a cladding light stripper, and a transmission fiber connected in sequence, wherein: The semiconductor pump source is used to output the auxiliary laser, pump light and indicator light; The high-reflection grating is used to reflect the main laser back to the ytterbium-doped gain optical fiber; The ytterbium-doped gain optical fiber is used to convert the pump light into a main laser and transmit the main laser in the core, and transmit the auxiliary laser and the indicator light in the inner cladding; The low-reflection grating is used to control the output of the main laser; The cladding light stripper is used to strip the unabsorbed excess pump light and return light, and transmit the main laser, auxiliary laser and indicator light; The transmission optical fiber is used to transmit the main laser, auxiliary laser and indicator light to the quartz end cap at the tail end for final output. 14. The device according to item 13, wherein the semiconductor pump source comprises three wavelength semiconductor chips: 420-470nm blue light semiconductor chip: used to output the auxiliary laser; 650nm red light semiconductor chip: used to output the indicator light for easy positioning; 915nm or 976nm pump light semiconductor chip: used to output the pump light; The semiconductor pump source is externally controlled to respectively control the light emission of the semiconductor chip of three wavelengths through three positive and negative pins; The lights emitted by the three wavelength semiconductor chips are coupled into the output optical fiber of the semiconductor pump source through spatial light. 15. The device according to item 14, wherein: By changing the voltage and current applied to the semiconductor pump source pin or changing the number of semiconductor chips that output lasers, the power of the laser output by the semiconductor chips in the laser module can be controlled. 16. According to the device described in item 14, the light emitted by the three wavelength semiconductor chips is coupled into the output optical fiber of the semiconductor pump source through spatial light as follows: The laser emitted by each semiconductor chip changes the propagation direction of the beam through a high-reflectivity plane mirror to form parallel light composed of multiple beams; Each set of reflectors is arranged in a stepped manner, that is, arranged in layers in the direction of the light path, and each set of light paths moves up or down layer by layer; Each laser is focused and coupled into the output optical fiber of the semiconductor pump source through a focusing lens group or a reflecting mirror. 17. The device according to item 16, wherein: The reflectors corresponding to the 420-470nm blue light semiconductor chip and the 650nm red light semiconductor chip reflect the auxiliary laser and the indicator light to the central area of ​​the parallel light; The reflector corresponding to the 915nm or 976nm pump light semiconductor chip reflects the pump light to the peripheral area of ​​the parallel light. 18. The device according to item 17, wherein the output optical fiber of the semiconductor pump source is a triple-cladding laser, including a core, an inner cladding and an outer cladding, and the method of focusing and coupling each laser into the output optical fiber of the semiconductor pump source through a focusing lens group further comprises: The auxiliary laser and the indicator light are coupled into the inner cladding of the output optical fiber through a focusing lens; The pump light is coupled into the inner cladding of the output optical fiber through a focusing lens. 19. According to the device described in item 18, the input end of the optical fiber connected to the semiconductor pump source is an end cap. 20. According to the device described in item 13, the high and low reflection gratings adopt a reflection range near 1050-1080nm, the reflectivity of the high reflection grating is >99%, and the reflectivity of the low reflection grating is between 3% and 30%. 21. According to the device described in item 13, the laser module has multiple semiconductor pump sources, and the laser is transmitted to the high-reflection grating through fiber coupling or spatial coupling. 22. According to the device described in item 17, the output optical fiber of the semiconductor pump source includes a cladding and a core, and each laser is focused and coupled into the cladding of the output optical fiber of the semiconductor pump source through a focusing lens group or a reflector. 23. According to the device described in item 13, the NA value of the output end of the transmission optical fiber is greater than or equal to the NA value of the input end. 24. According to the device described in item 4, the control module comprehensively optimizes and obtains the best parameters based on the material type and processing requirements of the workpiece and the corresponding historical processing data, which are used as the initial processing parameters for each stage. 25. According to the device of item 4, the control module further includes: Material database, used to store reflectivity data of common materials at different temperatures, especially reflectivity data near the melting point; A material identification unit, used to compare the workpiece surface temperature measured by the temperature detection module and the reflectivity data measured by the return light detection module with the material characteristics in the material database, and match the closest material type according to the characteristic curve of reflectivity changing with temperature; A parameter adjustment unit, used to adjust the processing parameters based on the temperature and the reflectivity of the return light of the main laser and feed back to the laser module; The melting judgment unit is used to judge whether the processing area of ​​the workpiece is melted. 26. The device according to item 1, 3, wherein: The spot of the main laser in the laser output through the quartz end cap at the tail end is smaller than that of the auxiliary laser. 27. The device according to item 13, wherein: The size range of all optical fiber cores in the laser module is from 10 μm to 50 μm; The sizes of all optical fiber claddings in the laser module cover the range from 125 μm to 1500 μm. 28. A method for anti-return of a high-power fiber laser, comprising: Detect the status of the processing area of ​​the workpiece; Setting processing parameters based on the state of the processing area; The laser generates an auxiliary laser and a main laser according to the processing parameters and adjusts the output power of the auxiliary laser and the main laser, wherein the auxiliary laser is used for preheating and / or surface melting of the processing area, and the main laser is used for deep processing of the processing area; When the processing area is not melted, lowering the output power of the main laser; When melting occurs in the processing area, the output power of the main laser is increased. 29. The method according to item 28, wherein the state of the processing area comprises: The temperature of the processing area on the workpiece and / or the reflectivity of the main laser return light in the processing area. 30. The method according to item 29, wherein: Irradiating the workpiece with lasers at different incident angles and / or wavelengths before preheating the processing area; Before preheating and just entering the surface melting stage, collect the reflectivity data of the main laser return light in the processing area; By analyzing the reflectivity of the main laser return light or combining with the temperature detection module to detect the temperature of the processing area on the workpiece, the specific material type of the workpiece can be identified before preheating, and the identification result can be corrected at the beginning of the surface melting stage. 31. The method according to item 29 or 30, wherein: According to the processing requirements and the material type of the workpiece identified before preheating, corresponding initial processing parameters are set for the preheating stage and the surface melting stage respectively, and the initial processing parameters of each stage include: at least one of the total output power, laser scanning speed, power ratio of the main laser and the auxiliary laser, pulse width, pulse frequency, peak power, average power, and duty cycle; Based on the temperature of the processing area and the reflectivity of the main laser return light, it is determined whether the processing area is currently in the preheating stage or the surface melting stage; At the beginning of the preheating stage, the laser outputs laser according to the initial processing parameters of the preheating stage to preheat the processing area of ​​the workpiece; At the beginning of the surface melting stage, adjusting the initial processing parameters of the surface melting stage based on the workpiece material type correction result; During the process of each stage, the processing parameters are dynamically adjusted according to the real-time monitored temperature of the processing area and the reflectivity of the return light of the main laser, and are fed back to the laser. 32. The method according to item 31, wherein: The conditions for adjusting the processing parameters are also determined based on the material type and processing requirements of the workpiece, and specifically include: a first threshold, a maximum preheating time, a second threshold, a return light reflectivity-temperature curve of the workpiece material, and a target temperature range of the processing area during the surface melting stage. 33. The method according to item 31, wherein during the preheating stage, The auxiliary laser accounts for 70%-90% of the total output power; The main laser accounts for 10%-30% of the total output power. 34. The method according to item 31, wherein during the surface melting stage, The main laser accounts for 70%-90% of the total output power; The auxiliary laser accounts for 10%-30% of the total output power. 35. The method according to item 32, wherein: In the preheating stage, if the temperature change rate of the processing area is lower than the first threshold, or when the preheating time exceeds the initial preheating time and the surface melting stage has not been detected, the power of the auxiliary laser is increased or the scanning speed is reduced. 36. The method according to item 32, wherein: The basis for judging whether the processing area enters the surface melting stage is: If the reflectivity change rate of the main laser return light exceeds the second threshold; or The actual change curve of the reflectivity of the main laser return light and temperature shows a significant turning point. 37. The method according to item 32, wherein the surface melting stage further comprises the following steps: Determining whether the temperature of the processing area exceeds the target temperature range; If the target temperature range is exceeded, the total power of the main laser and the auxiliary laser is reduced, the scanning speed is increased, and the duty cycle of the pulse is reduced to avoid overheating and metal splashing; If the temperature is lower than the target temperature range, the power of the main laser is increased, the scanning speed is reduced, and the duty cycle of the pulse is increased. 38. The method according to item 29, wherein: Installing a module for detecting the reflectivity of the return light of the main laser on the side of the laser path of the main laser and the auxiliary laser, and separating the return light of the main laser from the optical path using a beam splitter or a reflector; or A module for detecting the reflectivity of the return light of the main laser is installed at the output position of the main laser and the auxiliary laser, and an optical isolator is used to separate the return light of the main laser; A wavelength selective filter is installed in the module that detects the reflectivity of the main laser return light, allowing only the main laser in the return light to pass through. 39. The method according to item 38, wherein: The reflectivity is calculated by calculating the ratio of the main laser intensity to the main laser return light intensity. 40. The method according to item 28, wherein the laser is provided with: a semiconductor pump source, a high reflection grating, an ytterbium-doped gain fiber, a low reflection grating, a cladding light stripper and a transmission fiber connected in sequence, wherein: The semiconductor pump source outputs the auxiliary laser, pump light and indicator light; The high-reflection grating reflects the main laser back to the ytterbium-doped gain fiber; The ytterbium-doped gain optical fiber converts the pump light into a main laser and transmits the main laser in the core, and transmits the auxiliary laser and the indicator light in the inner cladding; The low-reflection grating controls the output of the main laser; The cladding light stripper strips the unabsorbed excess pump light and return light, and transmits the main laser, auxiliary laser and indicator light; The transmission optical fiber transmits the main laser, auxiliary laser and indicator light to the quartz end cap at the rear end for final output. 41. According to the method of item 40, the semiconductor pump source includes three wavelength semiconductor chips: The auxiliary laser is output by a 420-470nm blue light semiconductor chip; The 650nm red light semiconductor chip outputs the indicator light to facilitate positioning; The 915nm or 976nm pump light semiconductor chip outputs the pump light; The semiconductor pump source is externally controlled to respectively control the light emission of the semiconductor chip of three wavelengths through three positive and negative pins; The lights emitted by the three wavelength semiconductor chips are coupled into the output optical fiber of the semiconductor pump source through spatial light. 42. The method according to item 41, wherein the power of the laser output by the semiconductor chip in the laser is controlled by changing the voltage and current applied to the pin of the semiconductor pump source or changing the number of semiconductor chips that output the laser. 43. According to the method described in item 41, the light emitted by the three wavelength semiconductor chips is coupled into the output optical fiber of the semiconductor pump source through spatial light, which specifically includes: The laser emitted by each semiconductor chip changes the propagation direction of the beam through a high-reflectivity plane mirror to form parallel light composed of multiple beams; Each set of reflectors is arranged in a stepped manner, that is, arranged in layers in the direction of the light path, and each set of light paths moves up or down layer by layer; Each laser is focused and coupled into the output optical fiber of the semiconductor pump source through a focusing lens group or a reflecting mirror. 44. The method according to item 43, wherein: The reflectors corresponding to the 420-470nm blue light semiconductor chip and the 650nm red light semiconductor chip reflect the auxiliary laser and the indicator light to the central area of ​​the parallel light; The reflector corresponding to the 915nm or 976nm pump light semiconductor chip reflects the pump light to the peripheral area of ​​the parallel light. 45. According to the method described in item 44, the output optical fiber of the semiconductor pump source is a triple-cladding laser, including a core, an inner cladding and an outer cladding, and the focusing lens group is used to focus and couple each laser into the output optical fiber of the semiconductor pump source, and further comprises: The auxiliary laser and the indicator light are coupled into the inner cladding of the output optical fiber through a focusing lens; The pump light is coupled into the inner cladding of the output optical fiber through a focusing lens. 46. ​​According to the method described in item 45, the input end of the optical fiber connected to the semiconductor pump source is an end cap. 47. According to the method described in item 40, the high and low reflection gratings adopt a reflection range near 1050-1080nm, the reflectivity of the high reflection grating is >99%, and the reflectivity of the low reflection grating is between 3% and 30%. 48. According to the method described in item 40, the laser has multiple semiconductor pump sources, and the laser light is transmitted to the high-reflection grating by fiber coupling or spatial coupling. 49. According to the method described in item 44, the output optical fiber of the semiconductor pump source includes a cladding and a core, and each laser is focused and coupled into the cladding of the output optical fiber of the semiconductor pump source through a focusing lens group or a reflector. 50. According to the method described in item 40, the NA value of the output end of the transmission optical fiber is greater than or equal to the NA value of the input end. 51. The method according to item 31, wherein the optimal parameters are obtained through comprehensive optimization based on the material type and processing requirements of the workpiece being processed and combined with the corresponding historical processing data, and are used as the initial processing parameters for each stage. 52. The method according to item 31, further comprising the steps of: Store the reflectivity data of common materials at different temperatures in the material database, especially the reflectivity data near the melting point; The measured workpiece surface temperature and the reflectivity of the main laser return light are compared with the material properties in the material database, and the closest material type is matched based on the characteristic curve of reflectivity changing with temperature. 53. The method according to item 40, wherein: The spot of the main laser in the laser output through the quartz end cap at the tail end is smaller than that of the auxiliary laser. 54. The method according to item 40, wherein: The size range of all optical fiber cores in the laser is from 10 μm to 50 μm; The sizes of all fiber claddings in the laser cover the range from 125 μm to 1500 μm.

Claims

1. An anti-return high-power fiber laser device, comprising a control module, a laser module, and a workpiece status inspection module; The workpiece status inspection module detects the status of the processing area of ​​the workpiece; The control module sets the processing parameters based on the state detected by the workpiece state inspection module; The laser module generates an auxiliary laser and a main laser according to the processing parameters and adjusts the output power of the auxiliary laser and the main laser, wherein the auxiliary laser is used for preheating and / or surface melting of the processing area, and the main laser is used for deep processing of the processing area; When the workpiece state inspection module detects that the processing area is not melted, the control module lowers the output power of the main laser; When the workpiece state inspection module detects that the processing area is melted, the control module increases the output power of the main laser.

2. The device according to claim 1, wherein the workpiece status inspection module 3 further comprises: A temperature detection module is used to detect the temperature of the processing area on the workpiece throughout the process and feed it back to the control module; and / or The return light detection module is used to detect the reflectivity of the main laser return light in the processing area throughout the entire process and feed it back to the control module.

3. The device according to claim 2, wherein: The laser module irradiates the workpiece with lasers of different incident angles and / or wavelengths before preheating the processing area; The return light detection module collects the reflectivity data of the return light of the main laser in the processing area before preheating and just entering the surface melting stage, and feeds it back to the control module; The control module analyzes the reflectivity of the return light of the main laser or detects the temperature of the processing area on the workpiece in combination with the temperature detection module, thereby identifying the specific material type of the workpiece before preheating and correcting the identification result at the beginning of the surface melting stage.

4. The device according to claim 2 or 3, wherein: The control module sets corresponding initial processing parameters for the preheating stage and the surface melting stage respectively according to the processing requirements and the material type of the workpiece identified before preheating, and the initial processing parameters of each stage include: at least one of the total output power, laser scanning speed, power ratio of the main laser and the auxiliary laser, pulse width, pulse frequency, peak power, average power, and duty cycle; The control module determines whether the processing area is currently in the preheating stage or the surface melting stage based on the feedback data of the temperature detection module and / or the return light detection module; At the beginning of the preheating stage, the laser module outputs laser according to the initial processing parameters of the preheating stage to preheat the processing area of ​​the workpiece; At the beginning of the surface melting stage, the control module adjusts the initial processing parameters of the surface melting stage based on the workpiece material type correction result and feeds back to the laser module; In the process of each stage, the control module dynamically adjusts the processing parameters according to the real-time monitored temperature of the processing area and the reflectivity of the return light of the main laser, and feeds back to the laser module.

5. The device according to claim 4, wherein: The control module also determines the conditions for adjusting the processing parameters based on the material type and processing requirements of the workpiece, which specifically include: a first threshold, a maximum preheating time, a second threshold, a return light reflectivity-temperature curve of the workpiece material, and a target temperature range of the processing area during the surface melting stage.

6. The device according to claim 4, wherein during the preheating stage, The auxiliary laser accounts for 70%-90% of the total output power; The main laser accounts for 10%-30% of the total output power.

7. The device according to claim 4, wherein during the surface melting stage, The main laser accounts for 70%-90% of the total output power; The auxiliary laser accounts for 10%-30% of the total output power.

8. The device according to claim 5, wherein: During the preheating stage, if the temperature change rate of the processing area is lower than the first threshold, or when the preheating time exceeds the initial preheating time and the surface melting stage has not yet been detected, the control module increases the power of the auxiliary laser or reduces the scanning speed, and feeds back to the laser module.

9. The device according to claim 5, wherein: The basis for judging whether the processing area enters the surface melting stage is: If the reflectivity change rate of the main laser return light exceeds the second threshold; or The actual change curve of the reflectivity of the main laser return light and temperature shows a significant turning point.

10. A method for preventing backscatter of a high-power fiber laser, comprising: Detect the status of the processing area of ​​the workpiece; Setting processing parameters based on the state of the processing area; The laser generates an auxiliary laser and a main laser according to the processing parameters and adjusts the output power of the auxiliary laser and the main laser, wherein the auxiliary laser is used for preheating and / or surface melting of the processing area, and the main laser is used for deep processing of the processing area; When the processing area is not melted, lowering the output power of the main laser; When melting occurs in the processing area, the output power of the main laser is increased.

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