Constant path length laser machining system and method

Abstract

The application discloses a constant optical path laser processing system based on geometric constraint, and belongs to the technical field of laser processing. In view of the technical defects of the existing laser processing equipment, such as the change of optical path, the need of complex dynamic focusing, and the low switching efficiency of multiple materials and multiple processes, the application utilizes the geometric constraint of bipolar coordinates (the length L of a rotating arm is equal to the axial distance a), and through an optical path turning system arranged near the rotating center of the rotating arm, the laser beam is turned to propagate along the radial direction of the rotating arm, and then is turned by a mirror fixed on the outer periphery of the rotating arm to be vertically downward emitted to a processing head. The total optical path of the laser is determined as a constant value by the geometric size of the rotating arm, and the rotating arm only carries the light mirror and the processing head, and the motion inertia is extremely low. The application can be configured as a single light source swing arm structure or a multi-light source rotating disc structure, is suitable for laser processing of single material and multiple processes or composite material and multiple processes, and has the advantages of constant optical path, fast dynamic response, simple control, and simple structure.

Description

Technical Field

[0001] This invention relates to the field of laser processing technology, specifically to a constant optical path laser processing system and method based on bipolar coordinate geometric constraints, applicable to laser cutting, engraving, marking, welding and other processing of single materials with multiple processes or composite materials with multiple processes. Background Technology

[0002] Laser processing technology encompasses various processes such as cutting, engraving, marking, and welding, and is widely used in various fields of manufacturing. Existing laser processing equipment mainly employs gantry (XYZ three-axis), galvanometer scanning, or robotic arm structures, which generally suffer from the problem of optical path variation with movement position, leading to focus drift. This necessitates the use of complex dynamic focusing systems for compensation. For multi-process laser processing, current technologies require frequent changes in processing heads or equipment switching, resulting in low efficiency. For multi-material composite processing (such as processing metals and non-metals on the same workpiece), current technologies typically require multiple laser devices or frequent laser replacements on the same device, leading to high equipment investment and low efficiency. Although multi-wavelength laser beam combining technology exists, the complex optical path and limited wavelength combinations make rapid switching difficult.

[0003] Therefore, there is an urgent need for a universal laser processing system with constant optical path length, minimal structure, support for rapid optical switching between multiple processing heads, and scalability to multiple light source selection. The system should be applicable to a single light source configuration (for processing a single material) or scalable to a configuration with multiple light sources of different wavelengths (for processing multiple materials), and should maintain a constant optical path length for the processing beam regardless of the configuration. Summary of the Invention

[0004] The purpose of this invention is to overcome the technical shortcomings of existing laser processing equipment, such as variable optical path, the need for complex dynamic focusing, and low efficiency in switching between multiple materials / processes. It provides a constant optical path laser processing system based on bipolar coordinate geometric constraints. By fixing the laser generator to a fixed base, preventing it from moving with the rotary arm, the moment of inertia is greatly reduced. Simultaneously, the geometric structure ensures a constant optical path, eliminating the need for active compensation. Furthermore, it can be expanded into a multi-source circular arrangement and a rotary multi-processing head structure, achieving multi-functional integration.

[0005] To achieve the above objectives, the core concept of this invention is as follows: at least one laser generator is fixedly mounted on a fixed base, remaining stationary independently relative to the rotary arm; an optical path deflection system is set near the rotation center of the rotary arm to deflect the laser beam into radial propagation along the rotary arm; then, through a reflector fixed to the outer periphery of the rotary arm and moving synchronously with it, the radial beam is deflected and emitted vertically downwards to the workpiece. Since the laser generator does not move, the rotary arm only carries the reflector and the processing head (lightweight), resulting in low moment of inertia; simultaneously, the total optical path from the laser generator to the processing point is determined by the geometric dimensions of the rotary arm (radius a) and the fixed vertical distance, which is a constant value requiring no active compensation.

[0006] This invention can be configured in two preferred embodiments: one is a single-source swing arm structure (the laser generator is fixed vertically downwards directly above the rotation center, and the rotating arm is a swing arm), which is suitable for cutting or engraving scenarios with single wavelength, low cost, and high dynamic response; the other is a multi-source turntable structure (multiple laser generators are installed horizontally along the circumference and switched by a light source selection prism, and the rotating arm is a disc-shaped tool turntable), which is suitable for multi-wavelength, multi-power, and multi-process composite processing scenarios.

[0007] To achieve the above objectives, the present invention provides a constant optical path laser processing system based on geometric constraints, characterized in that it comprises: a fixed base; a rotating stage disposed on the fixed base for carrying a workpiece and rotatable about a first rotation axis (O); a rotary arm, the first end of which is rotatably connected to the fixed base via a fixed axis (O1), the fixed axis (O1) being located on the X-axis or Y-axis of the first rotation axis (O) and at a distance a from the first rotation axis (O), the length or radius of the rotary arm being equal to the distance a; and at least one laser generator fixedly mounted on the fixed base and relative to... The rotating arm is stationary independently; an optical path deflection system is fixedly disposed near the fixed axis (O1) to deflect the laser beam emitted by the laser generator into a radial direction along the rotating arm; at least one laser processing head is disposed on the outer periphery of the rotating arm, each laser processing head is correspondingly disposed with a reflector, the reflector is fixed on the rotating arm and moves synchronously with the rotating arm, and is used to deflect the radially propagating laser beam into a vertically downward emission; wherein, the total optical path from the laser generator to the processing point is determined by the geometric dimensions of the rotating arm, and the total optical path does not remain constant with the rotation angle of the rotating arm.

[0008] Furthermore, the at least one laser generator is a single laser generator, which is fixed directly above the fixed axis (O1) and the light emission direction is vertically downward along the axis; the optical path deflection system includes a first reflector fixed directly below the fixed axis (O1) for deflecting the vertically downward laser beam into a radial direction along the rotating arm; the rotating arm is in the shape of a swing arm and has a length of a.

[0009] Furthermore, the at least one laser generator is actually at least two, which are fixedly mounted on the fixed base along the circumferential direction, and the light emission direction of each laser generator is radially directed towards the fixed axis (O1); the optical path deflection system includes a light source selection prism and a first reflector assembly. The light source selection prism is disposed above the fixed axis (O1) and is used to selectively couple the laser beam of one of the laser generators to the first reflector assembly by rotation. The first reflector assembly is correspondingly disposed at the fixed axis (O1) position and is used to deflect the incident laser beam to propagate in the radial direction.

[0010] Furthermore, the rotary arm is a disc-shaped tool turntable, and at least two laser processing heads are arranged circumferentially on the outer periphery of the tool turntable. Each laser processing head is provided with a second reflector, and the distance from each second reflector to the fixed axis (O1) is equal to a. The first reflector assembly is installed in a mirror mount that can rotate around a vertical axis. The mirror mount is driven by a motor. By rotating the angle of the first reflector, the processing beam is selectively directed to different second reflectors, thereby realizing rapid optical switching between different laser processing heads.

[0011] Furthermore, the at least two laser generators include lasers of different types or different powers, and the different types include at least two of carbon dioxide lasers, fiber lasers, diode lasers, and solid-state lasers; the laser processing head is a laser cutting head, a laser engraving head, or a laser marking head, and the at least two laser processing heads provided on the rotary arm include at least two of the above types.

[0012] Furthermore, the rotary arm is equipped with a Z-axis drive mechanism, which is used to adjust the vertical position of the laser processing head according to the thickness of the workpiece to be cut, so as to keep the total laser optical path at the same height constant.

[0013] The present invention also provides a laser processing method using the above-described system, characterized by comprising the following steps: S1: Obtain the coordinates (x, y) of the target machining point in the model coordinate system, and calculate the polar radius ρ= And the polar angle θ0 = atan2(y,x); S2: Calculate the rotation angle of the rotary arm φ=arccos(1-ρ² / (2a²)) and the rotation angle of the rotary platform θ=φ / 2-θ0 according to the bipolar coordinate inverse kinematics formula; S3: Synchronously drive the rotating stage and rotary arm to bring the laser processing head to the target point; S4: Turn on the laser generator so that the processing beam is transmitted to the laser processing head through the first reflecting mirror, the horizontal section (a) and the second reflecting mirror. Since the optical path is constant, the laser focus is automatically aligned with the workpiece surface, and the processing can be completed without dynamic focusing.

[0014] Furthermore, when there are multiple laser generators or multiple laser processing heads, a switching step is also included: switching the laser generator by rotating the light source selection prism, or switching the laser processing head by rotating the first reflector assembly; and compensating the target rotation angle θ of the rotating stage according to the installation angle δ of the switched laser processing head: θ′=θ-δ; or compensating the rotation angle of the light source selection prism or the first reflector assembly according to the installation angle φ of the switched laser generator.

[0015] Compared with the prior art, the present invention has achieved the following significant advancements: 1. Simplified structure: No additional mechanisms such as optical path trolley, compensation mirror group, and fiber optic cable chain are required. The optical path can be kept constant through the reflector, which greatly reduces the manufacturing cost and assembly and debugging difficulty of the equipment. 2. Constant optical path: For coplanar processing, the optical path is fixed by the geometric structure, eliminating problems such as detection error, control lag, and residual compensation error found in active compensation schemes. The consistency of spot size and energy density is superior to existing technologies. 3. Simple control logic: Only polar coordinate kinematics calculation and simple angle compensation are required. No optical path closed-loop control, no optical path detection sensor, and no compensation motor control algorithm are needed. The complexity of the control system is significantly reduced, the control cycle is short, and the real-time performance and reliability are improved. 4. Low moment of inertia: The laser generator is fixedly installed and does not move with the rotary arm. The rotary arm only carries the lightweight reflector and processing head, which significantly reduces the moment of inertia and allows for higher acceleration and processing speed. It is especially suitable for high-speed laser engraving and precision cutting. 5. Improved reliability: No bending fatigue issues associated with moving optical cables / fibers, no risk of mechanical failure in compensation mechanisms, and significantly improved MTBF of the equipment; 6. Multi-wavelength and multi-process integration: By arranging multiple laser generators in a circle and rotating multi-processing heads, and with the help of light source selection prisms, seamless switching between multiple processes such as CO2 laser cutting, fiber laser marking, and diode laser engraving can be achieved on a single machine. All processing can be completed in one workpiece clamping, avoiding repeated positioning errors. Attached Figure Description

[0016] Figure 1 This is a geometric diagram based on the bipolar coordinate system of this invention.

[0017] Figure 2 This is a schematic diagram of the overall structure of Embodiment 1 (single light source swing arm structure) of the present invention.

[0018] Figure 3 This is a schematic diagram of the overall structure of Embodiment 2 (multi-light source turntable structure) of the present invention.

[0019] Figure 4 This is a top view of the arrangement of the light source selection prism and laser generator in Embodiment 2 of the present invention.

[0020] Figure 5 This is a schematic diagram of the optical path principle of the present invention (side view, taking a single light source as an example).

[0021] Figure 6 This is a flowchart of the optical path control method of the present invention. Detailed Implementation

[0022] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0023] The constant optical path laser processing system of the present invention is based on the geometric constraint relationship of a bipolar coordinate system as follows: Figure 1 As shown, the mechanical structure must ensure that the length L of the rotary arm 300 is equal to the distance a between the two rotation centers. A coordinate system is established with the center O of the rotating platform 200 as the origin (0,0) and the rotation center O1 of the rotary arm 300 fixed at (0, a). The target point P(x,y) in this coordinate system is first calculated using the polar radius ρ = ... The polar angle θ0 = atan2(y, x) is then used to directly calculate the rotation angle φ of the 300° rotary arm and the rotation angle θ of the 200° rotary platform in the bipolar coordinate system using a preset calculation formula.

[0024] The preset calculation formulas are: rotation angle of the slewing arm φ = arccos(1-ρ² / (2a²)); rotation angle of the rotating platform θ = φ / 2-θ0.

[0025] To ensure that each reachable point corresponds to a unique joint angle solution, the above preset calculation formula avoids the problem of multiple solution selection by constraining φ∈[0,π], thus simplifying path planning.

[0026] The working range of the laser processing head is a circular area with a maximum radius of ρ=2a. Due to the influence of mechanical structure interference, the actual processing range 210 is less than or equal to the circular area with a radius of ρ=2a. Example 1: Single-light source swing arm structure

[0027] like Figure 2As shown, this embodiment provides a laser processing system with a single-source swing arm structure. The system mainly includes a fixed base 100, a rotating stage 200, a rotating arm 300, a laser generator 400, a first reflector 500 (as an optical path deflection system), a second reflector 600, and a laser processing head 700.

[0028] The fixed base 100 provides support for the entire machine. The rotating platform 200 is mounted on the fixed base 100 and can rotate around the first rotation axis O to support the workpiece (not shown in the figure). The first end of the rotary arm 300 is rotatably connected to the fixed base 100 through a fixed axis O1. O1 is located in the positive Y-axis direction of the first rotation axis O, and the distance between O and O1 is a. The length of the rotary arm 300 is equal to a.

[0029] The laser generator 400 is fixedly mounted on the fixed base 100, with its light outlet located directly above the fixed axis O1 and the light emission direction vertically downward (along the negative Z-axis). The laser generator 400 is stationary independently relative to the rotating arm 300 and does not move with the arm. In this embodiment, the laser generator 400 uses a 40W carbon dioxide laser tube, suitable for cutting and engraving non-metallic materials.

[0030] The first reflector 500 (as an optical path deflection system) is fixedly positioned directly below the fixed axis O1, with its reflective surface at a 45° angle to the horizontal plane. It is used to deflect the vertically downward laser beam into a horizontal direction (along the radial direction of the rotating arm 300) for propagation.

[0031] The second reflector 600 is fixedly mounted at the second end (i.e., the end point) of the rotary arm 300. Its reflective surface forms a 45° angle with the horizontal plane. It is used to redirect the horizontal laser beam propagating along the swing arm direction back into a vertically downward direction, which is then emitted from the laser processing head 700 onto the surface of the workpiece. The second reflector 600 moves synchronously with the rotary arm 300.

[0032] The laser processing head 700 is mounted below the second reflecting mirror 600 and contains a focusing lens and a focusing mechanism. Since the laser generator 400 does not move with the swing arm, the rotary arm 300 only supports the second reflecting mirror 600 and the laser processing head 700, resulting in extremely low moment of inertia and enabling very high acceleration and scanning speed.

[0033] The rotary arm 300 is equipped with a Z-axis drive mechanism 10, which is used to drive the rotary arm 300 and the laser processing head 700 to move in the vertical direction to adjust the focal position for processing materials of different thicknesses.

[0034] Optical path principle as follows Figure 5As shown (taking a single light source as an example): the vertical distance from the laser generator 400's output port to the first reflecting mirror 500 is H; the distance from the first reflecting mirror 500 to the second reflecting mirror 600 is equal to the swing arm length a; and the vertical distance from the second reflecting mirror 600 to the workpiece surface is h. The total laser optical path is L. total = H + a + h, where H is a fixed constant, a is a geometric constant, and h varies very little (usually a few millimeters). Furthermore, since the laser beam is parallel or focused in the vertical segment, changes in h do not affect the actual accuracy of the focused spot position; therefore, the total optical path can be considered constant. Unlike traditional flying optical path schemes, this scheme requires no active compensation mechanism when processing the same horizontal plane.

[0035] The control system in this embodiment can be implemented based on an embedded microcontroller. The rotating stage 200 and the rotary arm 300 are driven by stepper motors or servo motors in conjunction with encoders; the inverse kinematics calculation adopts a direct bipolar coordinate calculation formula; the optical path control does not require any sensors or compensation algorithms, and only the reflector angle needs to be calibrated during equipment initialization. Example 2: Multi-light source turntable structure

[0036] like Figure 3 , Figure 4 As shown, this embodiment provides a laser processing system with a multi-source turntable structure. The system mainly includes a fixed base 100, a rotating stage 200, a tool turntable 800, multiple laser generators (401, 402, 403), a light source selection prism 900, a first reflector assembly 500', multiple second reflectors (601, 602, 603), and multiple laser processing heads (701, 702, 703).

[0037] The fixed base 100 and the rotating stage 200 are configured the same as in Embodiment 1. The tool turntable 800 is rotatably connected to the fixed base 100, and its rotation center is the fixed axis O1. O1 is located in the positive Y-axis direction of the first rotation axis O, and the distance between O and O1 is a. The radius of the tool turntable 800 is equal to a.

[0038] The laser processing heads (701, 702, 703) are fixedly installed below the second reflectors (601, 602, 603), and each of them is equipped with a focusing lens and a focusing mechanism.

[0039] Three laser generators 401, 402, and 403 are horizontally fixed on the fixed base 100 along the circumferential direction, with the light output direction of each laser pointing radially towards the fixed axis O1. In this embodiment, laser generator 401 is a 100W CO2 laser (wavelength 10.6μm, the laser beam is deflected into a horizontal direction by a prism), suitable for non-metallic cutting; laser generator 402 is a 10W diode laser (wavelength 445nm), suitable for plastic marking and engraving; laser generator 403 is a 50W fiber laser (wavelength 1064nm, the laser beam is deflected into a horizontal direction by a prism), suitable for metal marking and thin plate cutting; the three lasers are distributed at intervals on the circumference. All laser generators are independently stationary relative to the tool turntable 800 and do not move with it.

[0040] The light source selection prism 900 is positioned directly above the fixed axis O1 and is a triangular prism that can rotate about a vertical axis. This prism is driven to rotate by a hollow stepper motor 910, and can be rotated to a preset angle under controller commands. This causes a horizontal radial beam emitted from a laser to be reflected by the prism and then, through the hollow axis of the stepper motor 910, become a vertically downward beam. The rotation angle of the light source selection prism 900 is precisely matched to the installation angles of the three lasers. The reflective surface of the prism is coated with a wide-band high-reflectivity film, covering the operating wavelengths of the three lasers.

[0041] The first reflector assembly 500' is positioned directly below the fixed axis O1 and includes a reflector 510 rotatable about a vertical axis. Its reflecting surface is at a 45° angle to the horizontal plane, used to deflect a vertically downward laser beam into a horizontal direction (propagating radially along the tool turntable). The first reflector assembly 500' is also driven by a stepper motor and can rotate to different angles under controller commands to guide the laser beam to different optical path channels on the tool turntable 800.

[0042] Multiple laser processing heads are evenly arranged along the outer periphery of the tool turntable 800: processing head 701 is a CO2 laser cutting head, processing head 702 is a diode laser engraving head, and processing head 703 is a fiber laser marking head. Each processing head corresponds to a second reflector (601, 602, 603), which is fixed on the tool turntable 800 and is used to deflect the radially propagating laser beam into a vertically downward emission.

[0043] This embodiment includes a compensation module: phase compensation—compensating for the target rotation angle θ of the rotating stage based on the currently selected installation angle δ of the laser processing head (θ′=θ-δ); light source compensation—compensating for the target rotation angle θ of the rotating stage or the rotation angle of the first reflector assembly based on the currently selected installation position angle φ of the laser generator, ensuring the consistency of the coordinate system of the processing point after switching. The above compensation values ​​are pre-calibrated and stored in the controller.

[0044] During operation, the user selects the required laser type and processing head according to the processing task. For example, first use a CO2 laser to cut a non-metallic shell (select laser 401, processing head 701), then switch to diode laser engraving of plastic decorations (rotate to 402 and 702), and then switch to fiber laser marking of metal signs (rotate the light source selection prism to position 403, and simultaneously rotate the first reflector assembly to the radial channel corresponding to 703). The compensation module automatically adjusts the coordinate system, keeping the workpiece fixed on the rotating platform at all times, completing all processes in one clamping operation.

[0045] The tool turntable 800 is also equipped with a Z-axis drive mechanism 10 and a distance sensor 20. The distance sensor 20 measures the distance from the tool turntable 800 to the machining surface. The measurement data from the distance sensor 20 is fed back to control the drive mechanism 10 and / or the machining head focusing mechanism, so that the tool turntable 800 moves in the vertical direction and / or the focal length of the machining head is adjusted to adjust the focal position for machining materials with different planar heights. Example 3: Processing Control Method

[0046] like Figure 6 As shown, this embodiment provides a polar coordinate laser processing method, which can be applied to both Embodiment 1 and Embodiment 2. The method includes the following steps: S1: Obtain the coordinates (x, y) of the target machining point in the model coordinate system, and calculate the polar radius ρ= And the polar angle θ0 = atan2(y,x); S2: Calculate the rotation angle of the rotary arm φ=arccos(1-ρ² / (2a²)) and the rotation angle of the rotary platform θ=φ / 2-θ0 according to the bipolar coordinate inverse kinematics formula; S3: Synchronously drive the rotating stage and rotary arm to bring the laser processing head to the target point; S4: Turn on the laser generator so that the processing beam is transmitted to the laser processing head through the first reflecting mirror, the horizontal section (a) and the second reflecting mirror. During the rotation stage and the rotary arm drive process, the total optical path of the laser from the laser generator to the processing point remains constant, and the laser focus is automatically aligned with the workpiece surface. Processing can be completed without dynamic focusing.

[0047] Since the laser generator does not move with the rotary arm, the moment of inertia of the rotary arm only includes the reflector and the laser processing head.

[0048] When there are multiple laser generators or multiple laser processing heads, the method further includes a switching step S5: switching the laser generator by rotating the light source selection prism or switching the laser processing head by rotating the first reflector assembly; and compensating the target rotation angle θ of the rotating stage according to the installation angle δ of the switched laser processing head (θ′=θ-δ); or compensating the rotation angle of the light source selection prism or the first reflector assembly according to the installation angle φ of the switched laser generator, so as to ensure the consistency of the coordinate system of the processing point.

[0049] To achieve stable and continuous control of the system, it is also necessary to handle boundary conditions, angle continuity, and abnormal situations during the actual motion control process.

[0050] It should be noted that the above specific implementation method is based on the calculation formula given for fixing the rotation center O1 of the rotary arm at (0,a). In practical applications, the rotation center O1 of the rotary arm may not be limited to (0,a), but may also be located in other quadrants, such as (a,0), (-a,0), or (0,-a). The constraint range of the rotation angle φ of the rotary arm may also be φ∈[π:2π]. These configurations based on bipolar coordinate system geometric constraints through coordinate rotation transformation should all be covered within the protection scope of this invention.

[0051] It should be further explained that the constant optical path principle of this invention is based on the following facts: the total optical path is the sum of the vertical distance H from the laser generator output port to the first reflecting mirror, the distance a (i.e., the length or radius of the rotating arm) from the first reflecting mirror to the second reflecting mirror, and the vertical distance h from the second reflecting mirror to the workpiece surface. Here, a is a fixed value. Although H and h can change during Z-axis drive mechanism adjustment, H+h remains a constant value when machining on the same horizontal plane. Since the vertical beam is parallel or a pre-focused beam, dynamic focusing is unnecessary when machining on the same horizontal plane. When machining workpieces of different thicknesses, the machining head height can be adjusted synchronously via the Z-axis drive mechanism or through the focusing mechanism inside the machining head. In this case, the optical path change can be pre-calibrated and does not rely on real-time feedback compensation.

[0052] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A constant optical path laser processing system, characterized in that, include: A fixed base; A rotating platform is disposed on the fixed base for supporting the workpiece and can rotate about the first rotation axis (O); A rotary arm, the first end of which is rotatably connected to the fixed base via a fixed shaft (O1), the fixed shaft (O1) is located on the X-axis or Y-axis of the first rotating shaft (O), and the distance between the fixed shaft (O) and the first rotating shaft (O) is a, the length or radius of the rotary arm is equal to the distance a; At least one laser generator is fixedly mounted on the fixed base and is stationary independently of the rotating arm; An optical path deflection system is fixedly installed near the fixed axis (O1) to deflect the laser beam emitted by the laser generator into a direction that propagates along the radial direction of the rotating arm. At least one laser processing head is disposed on the outer periphery of the rotary arm, and each laser processing head is provided with a corresponding reflector. The reflector is fixed on the rotary arm and moves synchronously with the rotary arm to deflect the radially propagating laser beam into a vertically downward emission. The total optical path from the laser generator to the processing point is determined by the geometric dimensions of the rotary arm, and the total optical path does not remain constant as the rotation angle of the rotary arm changes.

2. The constant optical path laser processing system according to claim 1, characterized in that, The at least one laser generator is a single laser generator, and the laser generator emits light in a direction that is perpendicular to the downward axis of the fixed axis (O1); the optical path deflection system includes a first reflector fixed directly below the fixed axis (O1) for deflecting the vertically downward laser beam into a direction that propagates along the radial direction of the rotating arm; the rotating arm is in the shape of a swing arm and has a length of a.

3. The constant optical path laser processing system according to claim 1, characterized in that, The at least one laser generator is at least two, which are fixedly mounted on the fixed base along the circumferential direction, and the light emission direction of each laser generator is radially directed towards the fixed axis (O1); the optical path deflection system includes a light source selection prism and a first reflector assembly. The light source selection prism is disposed above the fixed axis (O1) and is used to selectively couple the laser beam of one of the laser generators to the first reflector assembly by rotation. The first reflector assembly is correspondingly disposed at the fixed axis (O1) position and is used to deflect the incident laser beam to propagate in the radial direction.

4. The constant optical path laser processing system according to claim 3, characterized in that, The rotary arm is a disc-shaped tool turntable. At least two laser processing heads are arranged circumferentially on the outer periphery of the tool turntable. Each laser processing head is provided with a second reflector, and the distance from each second reflector to the fixed axis (O1) is equal to a. The first reflector assembly is installed in a mirror mount that can rotate around a vertical axis. The mirror mount is driven by a motor. By rotating the angle of the first reflector, the processing beam is selectively directed to different second reflectors, thereby realizing rapid optical switching between different laser processing heads.

5. The constant optical path laser processing system according to claim 3 or 4, characterized in that, The at least two laser generators include lasers of different types or different powers, and the different types include at least two of carbon dioxide lasers, fiber lasers, diode lasers, and solid-state lasers; the laser processing head is a laser cutting head, a laser engraving head, or a laser marking head, and the at least two laser processing heads provided on the rotary arm include at least two of the above types.

6. The constant optical path laser processing system according to claim 1, characterized in that, The rotary arm is equipped with a Z-axis drive mechanism, which is used to adjust the vertical position of the laser processing head according to the thickness of the workpiece to be cut, so as to keep the total laser path at the same height constant.

7. A laser processing method using the system described in any one of claims 1-6, characterized in that, Includes the following steps: S1: Obtain the coordinates (x, y) of the target machining point in the model coordinate system, and calculate the polar radius ρ= And the polar angle θ0 = atan2(y,x); S2: Calculate the rotation angle of the rotary arm φ=arccos(1-ρ² / (2a²)) and the rotation angle of the rotary platform θ=φ / 2-θ0 according to the bipolar coordinate inverse kinematics formula. S3: Synchronously drive the rotating stage and rotary arm to bring the laser processing head to the target point; S4: Turn on the laser generator so that the processing beam is transmitted to the laser processing head through the first reflecting mirror, the horizontal section (a) and the second reflecting mirror. Since the optical path is constant, the laser focus is automatically aligned with the workpiece surface, and the processing can be completed without dynamic focusing.

8. The laser processing method according to claim 7, characterized in that, When there are multiple laser generators or multiple laser processing heads, the process also includes a switching step: switching the laser generator by rotating the light source selection prism, or switching the laser processing head by rotating the first reflector assembly; and compensating the target rotation angle θ of the rotating stage according to the installation angle δ of the switched laser processing head: θ′=θ-δ; or compensating the rotation angle of the light source selection prism or the first reflector assembly according to the installation angle φ of the switched laser generator.

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