Self-adaptive light beam regulation and control system for laser precision machining

Abstract

The invention provides a self-adaptive light beam regulation and control system for laser precision machining. The self-adaptive light beam regulation and control system comprises a light source unit, a micro-mirror device, a two-stage zooming system and a control unit. The micro-mirror array is introduced into the field of laser precision welding, light beam regulation and shaping of incident light are achieved, self-adaptive light spots which are arbitrary in shape and size, uniform in light intensity distribution and adjustable in output power are output on the surface of a workpiece in combination with a two-stage zooming system, and the machining precision in the fields of laser tin soldering and the like is remarkably improved; meanwhile, the two-stage zooming system can flexibly regulate and control the illumination distribution of the light beams on the micro-reflector array and the spot size of the light beams on the surface of the workpiece, the light energy utilization rate is effectively improved, and the power density consistency of the surface of the workpiece is guaranteed through combined regulation and control of the two-stage zooming system so that the better welding effect can be achieved.

Description

Technical Field

[0001] The present disclosure relates to the field of laser processing technology, and in particular to an adaptive beam control system for laser precision processing. Background Art

[0002] Currently, electronic manufacturing technology is rapidly advancing, with integrated circuits and related technologies gradually moving toward higher density. Lasers have been widely used in microelectronics processing to overcome the limitations of traditional processing methods. With the large-scale introduction of miniLED products, an increasing number of miniLED repair issues have also emerged. Lasers are a crucial tool in this process, used to remove defective chips and solder new ones. Conventional laser beams typically have a circular spot and a Gaussian energy distribution. LED chips are generally rectangular. Using traditional lasers to repair / solder LED chips means that the laser energy is directly exposed to the PCB along the short sides of the LED, causing burns. Furthermore, for laser precision soldering in consumer electronics, automotive electronics, and other fields, PCB pads often come in a variety of shapes and sizes, including square, circular, and even polygonal. To avoid burns on the PCB, beam control is often required.

[0003] The principle of laser soldering is to use a laser as a heating light source. Focusing the laser on the welding area converts the laser radiation energy into heat energy, melting the tin and completing the welding. However, existing laser soldering technology still has some limitations. The laser's morphology size is usually limited to a rectangular or circular adjustable spot, and its uniformity is also limited, which cannot well meet the requirements of the various shapes and sizes of solder pads used in laser precision machining.

[0004] In view of the above situation, it is necessary to propose a new adaptive beam control system for laser precision processing to meet the needs of more precise laser soldering and other processing technologies. Summary of the Invention

[0005] The purpose of the embodiments of the present disclosure is to provide an adaptive beam control system for laser precision machining to solve the problems existing in the prior art.

[0006] The embodiment of the present disclosure adopts the following technical solutions: an adaptive beam control system for laser precision machining, comprising: a light source unit, comprising a laser light source and a homogenizing fiber, wherein the laser light source is used to output laser light, and the homogenizing fiber is used to perform square homogenization on the laser light to form rectangular homogenized incident light; a micro-mirror device, comprising a plurality of micro-mirrors arranged in an array, for adjusting the shape of the incident light by adjusting the switching state of the micro-mirrors, to form a working light spot that matches the shape of the workpiece to be machined; a dual-stage zoom system, comprising a front-stage zoom homogenizing unit and a rear-stage zoom projection unit, wherein the front-stage zoom homogenizing unit is placed between the light source unit and the micro-mirror device, for projecting the micro-mirrors onto the incident light. The illumination area of ​​the mirror device is adjusted so that the illumination area is the minimum circumscribed rectangle of the micro-mirror set in the on state, and the post-stage zoom projection unit is placed between the micro-mirror device and the workpiece, and is used to adjust the size of the working light spot to form an output light spot, so that the size of the working light spot matches the size of the workpiece; a control unit is communicated with the laser light source, the micro-mirror device and the two-stage zoom system, and is used to adjust the laser power output by the laser light source, and adjust the switching state of the micro-mirrors of the micro-mirror device according to the shape and size of the workpiece, and linkage adjustment of the equivalent focal length of the front-stage zoom homogenization unit and the equivalent focal length of the post-stage zoom projection unit.

[0007] In some embodiments, it also includes: a workpiece detection unit, used to obtain the shape and size of the workpiece, and transmit the shape and size of the workpiece to the control unit; a light spot detection unit, used to collect the image of the output light spot through a beam splitter placed between the post-stage zoom projection unit and the workpiece, and transmit the collection result to the control unit.

[0008] In some embodiments, the control unit is specifically used to: generate a bitmap of the target light spot according to the shape and size of the workpiece; determine the size of the target light spot, the micro-mirrors that need to be turned on in the micro-mirror device, and the size of the illumination area according to the bitmap; and adjust the equivalent focal length of the front-stage zoom homogenization unit and the equivalent focal length of the rear-stage zoom projection unit in a linked manner according to the size of the target light spot and the size of the illumination area.

[0009] In some embodiments, the control unit is further used to: determine the size error and / or uniformity error between the output light spot and the target light spot based on the image of the output light spot; when the size of the output light spot is larger than the size of the target light spot, reduce the zoom factor of the post-stage zoom projection unit and increase the zoom factor of the pre-stage zoom equalization unit; when the size of the output light spot is smaller than the size of the target light spot, increase the zoom factor of the post-stage zoom projection unit and reduce the zoom factor of the pre-stage zoom equalization unit; when the uniformity error is greater than a preset threshold, simultaneously drive the compensation mirror group of the pre-stage zoom equalization unit and the compensation mirror group of the post-stage zoom projection unit to compensate for the uniformity error.

[0010] In some embodiments, the control unit is specifically configured to: perform linkage adjustment on the equivalent focal length of the front-stage zoom homogenization unit and the equivalent focal length of the rear-stage zoom projection unit according to a pre-calibrated zoom parameter coupling equation, wherein the focal parameter coupling equation is:

[0011]

[0012] Wherein, γ is the zoom ratio adjustment value of the rear zoom projection unit, f1 is the equivalent focal length of the front zoom homogenization unit, f2 is the equivalent focal length of the rear zoom projection unit, η is the zoom ratio of the size of the illumination area compared to the reference size of the micro-mirror device, K s Nonlinear correction coefficient determined by the workpiece shape.

[0013] In some embodiments, the system further includes: an infrared camera for monitoring the temperature distribution field on the surface of the workpiece in real time and transmitting the temperature distribution field to the control unit; the control unit is further configured to: determine the temperature abnormality area on the surface of the workpiece according to the temperature distribution field; determine the abnormal micro-mirror corresponding to the temperature abnormality area according to the mapping relationship between the workpiece surface and the micro-mirror array; determine the temperature difference between the real-time temperature of the temperature abnormality area in the temperature distribution field and the target temperature; when the temperature difference is greater than 0, switch the abnormal micro-mirror to an on-state with an adjustable duty cycle, and adjust the on-state duty cycle reduction amount ΔD of the abnormal micro-mirror based on the following formula:

[0014] ΔD=K p e (ΔT / τ) ×100%; (2)

[0015] Among them, K p is the proportional adjustment coefficient, ΔT is the temperature difference, and τ is the temperature sensitivity constant;

[0016] When the temperature difference is less than 0, all micro-mirrors in the illumination area are controlled to switch to an on-state with adjustable duty cycle, and the on-state duty cycle of the abnormal micro-mirror is controlled to be lower than the on-state duty cycles of other micro-mirrors.

[0017] In some embodiments, the control unit is further configured to increase the laser power output by the laser light source when the temperature difference is less than 0.

[0018] In some embodiments, the front-stage zoom homogenization unit is a cylindrical lens group, and the rear-stage zoom projection unit is a lens group.

[0019] In some embodiments, the homogenized optical fiber is a square core multimode homogenized optical fiber.

[0020] In some embodiments, the light source unit further includes: a fiber combiner arranged between the output fiber pigtail of the laser light source and the homogenizing fiber; the adaptive beam control system further includes: an energy recovery system, the energy recovery system includes: a coupling lens and a transmission fiber, the coupling lens is used to couple the light reflected by the micro-mirror in the off state in the illumination area of ​​the micro-mirror device into the transmission fiber, and the output end of the transmission fiber is connected to the input end of the fiber combiner.

[0021] The beneficial effects of the embodiments of the present disclosure are: introducing the micro-mirror array into the field of laser precision welding to realize beam control and shaping of the incident light, and combining with the two-stage zoom system to realize the output of an adaptive light spot with arbitrary shape and size, uniform light intensity distribution, and adjustable output power on the workpiece surface, which significantly improves the processing accuracy in fields such as laser soldering; at the same time, the two-stage zoom system can flexibly control the illumination distribution of the light beam in the micro-mirror array and the spot size on the workpiece surface, effectively improving the utilization rate of light energy, and using the joint control of the two-stage zoom system to ensure the consistency of power density on the workpiece surface, so as to achieve better welding effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate one or more embodiments of this specification or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 This is a system structure diagram of the adaptive beam control system in an embodiment of the present disclosure;

[0024] Figure 2 Schematic diagram of the optical system of the adaptive beam control system in an embodiment of the present disclosure;

[0025] Figure 3 A schematic diagram of a target light spot and a micro-mirror device window control in an embodiment of the present disclosure;

[0026] Figure 4 Schematic diagram of another target light spot and micro-mirror device window control in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solutions in one or more embodiments of this specification, the technical solutions in one or more embodiments of this specification will be clearly and completely described below in conjunction with the drawings in one or more embodiments of this specification. Obviously, the described embodiments are only part of the embodiments of this specification, not all of the embodiments. Based on one or more embodiments of this specification, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of this document.

[0028] Currently, electronic manufacturing technology is rapidly advancing, with integrated circuits and related technologies gradually moving toward high density. Lasers have become widely used in microelectronics processing to overcome the limitations of traditional processing methods. With the large-scale introduction of miniLED products, an increasing number of miniLED rework issues have also emerged. The most important tool in this process is the laser, which is used to remove defective chips and solder new ones. Conventional laser beams typically have a circular spot shape and a Gaussian energy distribution. LED chips are generally rectangular. Using traditional lasers to repair / solder LED chips means that the laser energy is directly exposed to the PCB along the short sides of the LED, causing burns. Furthermore, for precision laser soldering of consumer electronic circuits, PCB pads often come in a variety of shapes and sizes, including square, circular, and even polygonal. To avoid burns on the PCB, beam control is often required.

[0029] The principle of laser soldering is to use a laser as a heating light source. Focusing the laser on the welding area converts the laser radiation energy into heat energy, melting the tin and completing the welding. However, existing laser soldering technology still has some limitations. The laser's morphology size is usually limited to a rectangular or circular adjustable spot, and its uniformity is also limited, which cannot well meet the requirements of the various shapes and sizes of solder pads used in laser precision machining.

[0030] In order to solve the above problems, the present disclosure provides an adaptive beam control system for laser precision machining. Figure 1The system structure diagram of the adaptive beam control system is shown, which mainly includes: a light source unit, a micromirror device (the micromirror device in this embodiment is a digital micromirror device, i.e., Digital Micromirror Device, DMD, and the optional model is a digital micromirror device from Texas Instruments (TI), model DLP650LNIR, with a micromirror size of 10.8μm and a deflection angle of ±12°), a two-stage zoom system and a control unit, wherein the light source unit mainly includes a laser light source and a homogenizing fiber, the laser light source is used to output laser, and the homogenizing fiber is used to perform square homogenization on the laser to form a rectangular homogenized incident light; the micromirror device includes a plurality of micromirrors arranged in an array, which are used to adjust the shape of the incident light by adjusting the switching state of the micromirrors to form a working light spot that matches the shape of the workpiece to be processed; the two-stage zoom system includes a front-stage zoom homogenization unit and a rear-stage zoom projection unit, the front-stage zoom homogenization unit and the rear-stage zoom projection unit. The unit is placed between the light source unit and the micro-mirror device, and is used to adjust the illumination area of ​​the micro-mirror device projecting the incident light so that the illumination area is the minimum circumscribed rectangle of the micro-mirror set in the on state. The post-stage zoom projection unit is placed between the micro-mirror device and the workpiece, and is used to adjust the size of the working light spot to form an output light spot so that the size of the working light spot matches the size of the workpiece; the control unit is communicated with the laser light source, the micro-mirror device and the two-stage zoom system, and is used to adjust the laser power output by the laser light source, and adjust the on-off state of the micro-mirrors of the micro-mirror device according to the shape and size of the workpiece, and to perform linkage adjustment on the equivalent focal length of the front-stage zoom homogenization unit and the equivalent focal length of the post-stage zoom projection unit.

[0031] Figure 2 FIG1 shows a schematic diagram of the optical system of the adaptive beam control system of this embodiment. It should be noted that: Figure 2 The control unit is not displayed. Figure 2 In the optical system shown, the laser light source in the actual implementation of the system can be a high-speed response fiber-coupled output semiconductor laser 1, whose wavelength is ~976nm and the power is dynamically adjustable between 10W and 200W. Its output pigtail 2 is connected to a square-core multimode homogenizing fiber 4 as a homogenizing fiber, whose core diameter is 400×400μm / NA0.22, which is used to improve the uniformity of the light spot homogenization.

[0032] After being homogenized by the square core optical fiber, the laser is transmitted to the front-stage zoom homogenization unit 5, which has two functions: one is to relay the uniform light spot on the end face of the optical fiber to the window of the micro-mirror device 7 and maintain its uniformity; the other is to change the size of the light spot projected onto the window surface of the micro-mirror device 7 in real time by focusing; and then the micro-mirror device 7 controls the switching state of the micro-mirrors at different positions by loading a bitmap of corresponding shape to output a working light spot of a specific morphology and transmit it to the rear-stage zoom projection unit 9. The rear-stage zoom projection unit 9 also plays two roles at the same time: one is to laser process the surface of the workpiece projected by the working light spot modulated by the micro-mirror device 7, and the other is to achieve free scaling of the light spot size by adjusting its zoom ratio. At the same time, the front-stage zoom homogenization unit 5 and the rear-stage zoom projection unit 9 can also simultaneously improve the utilization rate of light energy by the micro-mirror device 7.

[0033] Specifically, the front-stage zoom homogenization unit 5 of this embodiment is a cylindrical mirror group, and the rear-stage zoom projection unit 9 is a lens group. Both can be driven by an electric translation stage to achieve the control of the equivalent focal length, such as Figure 2 As shown, the electric focusing module 6 is used to realize the focal length adjustment of the front-stage zoom equalizing unit 5, and the electric focusing module 10 is used to realize the focal length adjustment of the rear-stage zoom projection unit 9. Both are communicated with the control unit and perform linkage adjustment of the front-stage zoom equalizing unit 5 and the rear-stage zoom projection unit 9 according to the instructions of the control unit.

[0034] like Figure 2 As shown, the system generally includes a workpiece detection unit and a spot monitoring unit. The workpiece detection unit is mainly used to obtain the shape and size of the workpiece and transmit the shape and size of the workpiece to the control unit. Figure 2As shown, the workpiece detection unit mainly includes a workpiece detection camera 16, a reflector 15, and a dichroic mirror 8, which are used to capture images of the workpiece 13 to obtain its shape and size. In addition, it can also include a light source 14 for illuminating the workpiece 13 to improve its detection effect. In the actual processing process, the workpiece detection unit first works to locate and detect the workpiece morphology and provide real-time feedback to the control unit; the control unit performs digital image processing to generate a matching target light spot bitmap and loads it onto the DMD controller to control the switching state of the micro-reflector at the corresponding position and the size of the illumination area. Finally, based on the above calculation results, the laser source is driven to emit light at the rated power, and the size of the illumination area of ​​the front-stage zoom homogenization unit 5 in the DMD window and the zoom factor of the rear-stage zoom projection unit 9 are dynamically adjusted to finally output an output light spot that matches the workpiece morphology. In actual implementation, the control unit can generate a bitmap according to the size of the micro-mirror device. For example, if the array of the micro-mirror device is composed of 1280*800 micro-mirrors, the corresponding bitmap can also be an image of 1280*800 pixels, and the intensity information is reflected in the bitmap. 1 in the binary bitmap is used to represent the on state of the micro-mirror, and 0 represents the off state of the micro-mirror. Combined with the pixel values ​​at different positions in the bitmap, the state of the micro-mirror mapped to the corresponding position in the micro-mirror array is obtained, and it is input to the DMD controller to realize the on-off state control of the corresponding micro-mirror. The calculation of the illumination area is determined based on the set of micro-mirrors that are actually in the on state, so that it just covers the area of ​​the micro-mirrors in the on state, ensuring that the light spot irradiating the off state area is minimized.

[0035] The light spot detection unit 12 is used to capture the image of the output light spot through the beam splitter 11 placed between the post-stage zoom projection unit 9 and the workpiece 13, and transmit the captured result to the control unit. During the actual processing process, approximately 0.5% of the laser energy is transmitted to the light spot monitoring unit via the beam splitter 11 for analysis and monitoring, and then fed back to the control unit. After receiving the output light spot image output by the light spot detection unit 12, the control unit determines the error between the output light spot and the target light spot based on the image, such as shape error, size error, uniformity error, etc., and adjusts the micro-mirror device 7 or the dual-stage zoom system according to the specific error. Specifically, for shape error, when the output light spot has a shape missing in a certain area, the control unit adjusts the micro-mirror in the corresponding area from the off state to the on state output, and simultaneously adjusts the front-stage zoom homogenization unit 5 to match the illumination area; when the output light spot has a shape that exceeds the target light spot boundary in a certain area, the micro-mirror in the corresponding area is adjusted from the on state to the off state, and simultaneously adjusts the front-stage zoom homogenization unit 5 to match the illumination area. For size errors, when the output spot size is larger than the target spot size, the zoom factor of the subsequent zoom projection unit 9 is reduced, and the zoom factor of the preceding zoom and equalization unit 5 is increased. When the output spot size is smaller than the target spot size, the zoom factor of the subsequent zoom projection unit 9 is increased, and the zoom factor of the preceding zoom and equalization unit 5 is reduced. For uniformity errors, when the control unit determines that the uniformity error of the output spot is greater than a preset threshold, the compensation lens group of the preceding zoom and equalization unit 5 and the compensation lens group of the subsequent zoom projection unit 9 are simultaneously driven to adjust the uniformity of the spot and compensate for the uniformity error.

[0036] In this embodiment, when the control unit implements the dual-stage zoom system adjustment, it adjusts the equivalent focal length of the front-stage zoom homogenization unit 5 and the equivalent focal length of the rear-stage zoom projection unit 9 in a linked manner according to a pre-calibrated zoom parameter coupling equation. The focal parameter coupling equation is:

[0037]

[0038] Wherein, γ is the zoom ratio adjustment of the subsequent zoom projection unit, which can be specifically defined as the zoom ratio of the subsequent zoom projection unit to project the DMD micromirror array onto the workpiece surface, f1 is the equivalent focal length of the preceding zoom homogenization unit, f2 is the equivalent focal length of the subsequent zoom projection unit, η is the zoom ratio of the size of the illumination area compared to the reference size of the micromirror device, and K s The nonlinear correction coefficient is determined by the shape of the workpiece. The coefficient is pre-calibrated for different workpiece shapes and stored in the control unit for calling.

[0039] In actual implementation, the square core homogenizing fiber homogenizes and shapes the light output from the 976nm fiber coupling into a square flat-top light spot, which is evenly distributed on the end face of the square core fiber. The front-stage zoom homogenizing unit 5 is a focus-adjustable relay optical system. While achieving uniform illumination of the light spot to the micro-mirror device window, it also makes the light spot illuminated on the window variable in the horizontal and vertical dimensions to improve the utilization rate of light energy. Figure 3 As shown, when the target workpiece is a ring-shaped workpiece 101, the control unit generates a bitmap and loads it into the DMD system, controls the micromirror deflection angle so that the micromirrors in the dark ring area 103 are on and the micromirrors in the light area 102 are off, and controls the front-stage zoom homogenization unit 5 to illuminate the rectangular area 104 to avoid light energy covering the entire DMD window surface and causing light energy waste. Similarly, Figure 4 As shown, for the special-shaped L-shaped workpiece 201, the open state shape of the micro-mirror loaded on the DMD is shown as 203, and the light spot 204 irradiated on the DMD window is changed by the control unit, which greatly improves the utilization rate of light energy.

[0040] To further improve light energy efficiency and ensure that more micro-mirrors are in the on state, this embodiment uses a post-stage zoom projection unit to scale the spot size, maximizing the use of beam energy. Simultaneously, the front- and back-stage linkage adjustment can further maintain power consistency on the workpiece surface (i.e., achieving constant temperature heating). The implementation principle is as follows:

[0041] When the laser source has a constant power of P total When the front-stage homogenization system receives all the energy, an area of ​​A is formed on the DMD surface. ill The illumination spot, the light power density on the DMD surface is as follows:

[0042]

[0043] In the modulation stage of DMD, only the on-state micromirror area reflects effective light, and the effective area is set as A used , then the effective reflected power at this time is:

[0044]

[0045] The rear projection system will be A used If the area is magnified β times to the workpiece surface, the spot area on the workpiece surface is:

[0046] A work =A used ×β; (5)

[0047] At this time, the optical power density on the workpiece surface can be calculated as:

[0048]

[0049] Therefore, when the laser power is constant, the optical power density projected on the workpiece surface is related to the front stage illumination area and the rear stage magnification. When the rear stage magnification increases, it means that the optical power density projected on the workpiece surface decreases. By reducing the front stage illumination area A ill To directly increase the optical power density on the workpiece surface, compensate for the spot expansion effect caused by the increase of β, and maintain the consistency of power density.

[0050] like Figure 2 As shown, in some embodiments, the system also includes a temperature measuring unit, which in this embodiment is mainly an infrared camera, used to monitor the temperature distribution field on the surface of the workpiece in real time and transmit it to the control unit. By monitoring the temperature, firstly, the output power of the laser light source can be controlled in real time through temperature feedback to achieve constant temperature soldering on the workpiece surface. Secondly, since the light spot output on the workpiece surface cannot be completely uniform, there must be a certain area where the energy distribution is too high, which will cause the temperature of a certain area on the workpiece surface to be too high. The control unit determines the temperature abnormality area on the workpiece surface by analyzing the temperature distribution field, and drives the DMD array to continuously flip the switch state of the abnormal micro-mirror corresponding to the temperature abnormal area according to the mapping relationship between the workpiece surface and the DMD array (i.e., repeatedly switch between the off state and the on state), so as to control the light energy of the area in real time by controlling the on-state duty cycle of the micro-mirror flip to achieve the purpose of regulating the heating temperature. For the micro-mirror area where the temperature is maintained in the target temperature range and no temperature abnormality occurs, the current micro-mirror state can be maintained.

[0051] During the actual temperature control process, the control unit first calculates the temperature difference ΔT between the real-time temperature of the abnormal temperature area and the target temperature, and then controls the micro-mirror array in different ways according to the specific value of the temperature difference ΔT. Specifically, when the temperature difference ΔT is greater than 0, it means that the temperature of the abnormal temperature area is overheated and the energy needs to be reduced. At this time, the duty cycle of the abnormal micro-mirror can be adjusted based on the following formula:

[0052] ΔD=K p e (ΔT / τ) ×100%; (2)

[0053] Where ΔT is the temperature difference, K p is the proportional adjustment coefficient, which is used to control the basic adjustment range, K p The larger the value of , the more aggressive the duty cycle adjustment is under the same ΔT (to avoid oscillation). The specific value is set according to the actual situation. τ is the temperature sensitive constant. The smaller τ is, the more aggressive the duty cycle adjustment is. (ΔT / τ)It rises sharply with the increase of ΔT to achieve a strong nonlinear response. The above-mentioned proportional adjustment coefficient and temperature sensitive constant are related to the workpiece material to be processed, and the specific values ​​are determined by pre-calibration; when the temperature difference is less than 0, it means that the temperature in the temperature abnormality area is too low. At this time, all micro-mirrors in the illumination area can be controlled to switch to an on-state with adjustable duty cycle, and the on-state duty cycle of the abnormal micro-mirror is controlled to be lower than the on-state duty cycle of other micro-mirrors. At the same time, the cumulative light power in the output spot area under the same processing time will decrease, so the control unit can synchronously increase the laser power output by the laser light source to compensate.

[0054] In some embodiments, even if the utilization rate of light energy is improved by the front-stage zoom homogenization unit, there are still some micro-mirrors in the off state in the illumination area of ​​the DMD window. At this time, the light beam irradiated on the off-state surface will be reflected and deviate from the light path and cannot enter the subsequent optical system, resulting in some light energy being wasted and unusable. Therefore, the system of this embodiment also includes an energy recovery system, specifically including a coupling lens 18 and a transmission optical fiber 19. At the same time, a fiber combiner 3 is also provided between the transmission pigtail 2 and the homogenized light 4. The light 17 reflected by the micro-mirrors in the off state in the illumination area is coupled to the transmission optical fiber and then returned to the homogenized optical fiber through the light combiner 3, thereby realizing energy recovery.

[0055] This embodiment introduces a micro-mirror array into the field of laser precision welding to realize beam control and shaping of the incident light, and combines it with a two-stage zoom system to realize an adaptive light spot with arbitrary shape and size, uniform light intensity distribution, and adjustable output power on the workpiece surface, significantly improving the processing accuracy in fields such as laser soldering; at the same time, the two-stage zoom system can flexibly control the illumination distribution of the light beam in the micro-mirror array and the spot size on the workpiece surface, effectively improving the utilization rate of light energy, and utilizing the joint control of the two-stage zoom system to ensure the consistency of power density on the workpiece surface, so as to achieve better welding effects.

[0056] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present disclosure, rather than to limit them. Although the present disclosure has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present disclosure.

Claims

1. An adaptive beam control system for laser precision machining, characterized in that: include: A light source unit, comprising a laser light source and a homogenizing optical fiber, wherein the laser light source is used to output laser light, and the homogenizing optical fiber is used to perform square homogenization processing on the laser light to form rectangular homogenized incident light; A micro-mirror device, comprising a plurality of micro-mirrors arranged in an array, for adjusting the shape of the incident light by adjusting the on / off state of the micro-mirrors to form a working light spot that matches the shape of the workpiece to be processed; A dual-stage zoom system, comprising a front-stage zoom homogenization unit and a rear-stage zoom projection unit, wherein the front-stage zoom homogenization unit is disposed between the light source unit and the micro-mirror device and is configured to adjust the illumination area of ​​the micro-mirror device onto which the incident light is projected, so that the illumination area is the minimum circumscribed rectangle of the micro-mirror set in an on state; and the rear-stage zoom projection unit is disposed between the micro-mirror device and the workpiece and is configured to adjust the size of the working light spot to form an output light spot, so that the size of the working light spot matches the size of the workpiece. A control unit is communicatively connected with the laser light source, the micro-mirror device and the dual-stage zoom system, and is used to adjust the laser power output by the laser light source, adjust the switching state of the micro-mirrors of the micro-mirror device according to the shape and size of the workpiece, and perform linkage adjustment on the equivalent focal length of the front-stage zoom homogenizing unit and the equivalent focal length of the rear-stage zoom projection unit.

2. The adaptive beam control system according to claim 1, wherein: Also includes: a workpiece detection unit, configured to obtain the shape and size of the workpiece and transmit the shape and size of the workpiece to the control unit; A light spot detection unit is used to collect the image of the output light spot through a beam splitter placed between the post-stage zoom projection unit and the workpiece, and transmit the collected result to the control unit.

3. The adaptive beam control system according to claim 2, wherein: The control unit is specifically used for: generating a bitmap of a target light spot according to the shape and size of the workpiece; Determining the size of the target light spot, the micro-mirrors that need to be turned on in the micro-mirror device, and the size of the illumination area according to the bitmap; According to the size of the target light spot and the size of the illumination area, the equivalent focal length of the front-stage zoom homogenization unit and the equivalent focal length of the rear-stage zoom projection unit are linked and adjusted.

4. The adaptive beam control system according to claim 3, wherein: The control unit is further configured to: determining a size error and / or uniformity error between the output light spot and the target light spot according to the image of the output light spot; When the size of the output light spot is larger than the size of the target light spot, reducing the zoom ratio of the subsequent zoom projection unit and increasing the zoom ratio of the preceding zoom homogenization unit; When the size of the output light spot is smaller than the size of the target light spot, increasing the zoom ratio of the subsequent zoom projection unit and reducing the zoom ratio of the preceding zoom homogenization unit; When the uniformity error is greater than a preset threshold, the compensation mirror group of the front-stage zoom homogenization unit and the compensation mirror group of the rear-stage zoom projection unit are driven simultaneously to compensate for the uniformity error.

5. The adaptive beam control system according to claim 3, wherein: The control unit is specifically used for: The equivalent focal length of the front-stage zoom homogenization unit and the equivalent focal length of the rear-stage zoom projection unit are adjusted in a linked manner according to a pre-calibrated zoom parameter coupling equation, wherein the focal parameter coupling equation is: Wherein, γ is the zoom ratio adjustment value of the rear zoom projection unit, f1 is the equivalent focal length of the front zoom homogenization unit, f2 is the equivalent focal length of the rear zoom projection unit, η is the zoom ratio of the size of the illumination area compared to the reference size of the micro-mirror device, K s Nonlinear correction coefficient determined by the workpiece shape.

6. The adaptive beam control system according to claim 1, wherein: Also includes: an infrared camera, used to monitor the temperature distribution field on the surface of the workpiece in real time and transmit the temperature to the control unit; The control unit is further configured to: determining an abnormal temperature region on the surface of the workpiece according to the temperature distribution field; determining the abnormal micro-mirror corresponding to the abnormal temperature area according to a mapping relationship between the workpiece surface and the micro-mirror array; Determining a temperature difference between a real-time temperature of a temperature abnormality region in the temperature distribution field and a target temperature; When the temperature difference is greater than 0, the abnormal micro-mirror is switched to an on-state with an adjustable duty cycle, and the on-state duty cycle of the abnormal micro-mirror is adjusted by a reduction amount ΔD based on the following formula: ΔD=K p e (ΔT / τ) ×100%; (2) Among them, K p is the proportional adjustment coefficient, ΔT is the temperature difference, and τ is the temperature sensitivity constant; When the temperature difference is less than 0, all micro-mirrors in the illumination area are controlled to switch to an on-state with adjustable duty cycle, and the on-state duty cycle of the abnormal micro-mirror is controlled to be lower than the on-state duty cycles of other micro-mirrors.

7. The adaptive beam control system according to claim 6, wherein: The control unit is further configured to increase the laser power output by the laser light source when the temperature difference is less than 0.

8. The adaptive beam control system according to claim 1, wherein: The front-stage zoom homogenizing unit is a cylindrical lens group, and the rear-stage zoom projection unit is a lens group.

9. The adaptive beam control system according to claim 1, wherein: The homogenized optical fiber is a square core multimode homogenized optical fiber.

10. The adaptive beam steering system according to any one of claims 1 to 9, characterized in that: The light source unit further comprises: a fiber combiner disposed between the output fiber of the laser light source and the homogenizing fiber; The adaptive beam control system further includes: An energy recovery system, the energy recovery system comprising: a coupling lens and a transmission optical fiber, the coupling lens being used to couple light reflected by the micro-reflectors in the off state within the illumination area of ​​the micro-reflector device into the transmission optical fiber, the output end of the transmission optical fiber being connected to the input end of the optical fiber combiner.

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