Beam shaping system suitable for lifting processing head nozzle and laser processing head

Abstract

The utility model discloses a beam shaping system suitable for raising a nozzle of a processing head and a laser processing head, laser output by the beam shaping system passes through the nozzle to act on the surface of a workpiece, and the distance between the nozzle and the surface of a material to be processed is not less than 10mm. The light beam shaping system provided by the utility model is adaptive to a laser processing head nozzle which is raised, and can solve the problems that a raised nozzle is not matched with a conventional light path structure, the nozzle is heated seriously and the processing efficiency is low in the prior art.

Description

Technical Field

[0001] The utility model relates to the field of laser processing, in particular to a beam shaping system suitable for raising a processing head nozzle and a laser processing head. Background Art

[0002] Nozzle height refers to the distance between the machining head nozzle outlet and the workpiece surface. If the nozzle height is too low, it can easily collide with the workpiece surface (i.e., hit the plate). Furthermore, reflected light generated during machining can easily enter the machining head, adversely affecting the optical path. Through a special design of the nozzle's air path, while maintaining the required air pressure and concentration, the nozzle is raised, raising the distance between it and the cutting surface to approximately 15 mm. This helps prevent hits and laser backscatter, thereby extending the service life of the nozzle and machining head.

[0003] However, the elevated nozzle design in existing technology only incorporates a suitable air path, while the processing head still uses a conventional optical path. Conventional laser beams have a large divergence angle, and the farther away from the focal point, the larger the spot diameter. This causes part of the larger aperture of the beam to impact the nozzle, increasing the nozzle temperature and making it difficult to focus the beam on the workpiece surface. This increases the time required to melt the workpiece, affecting processing efficiency and other issues.

[0004] Based on this, the utility model specifically proposes a beam shaping system and a laser processing head suitable for raising the nozzle, so as to solve the problems in the prior art that the raised nozzle is not compatible with the conventional optical path, the nozzle is severely heated, and the processing efficiency is low. Utility Model Content

[0005] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a beam shaping system and a laser processing head suitable for raising the nozzle of the processing head, so as to solve the problems in the prior art that the raised nozzle is not compatible with the conventional optical path, the nozzle is severely heated, and the processing efficiency is low.

[0006] To achieve the above-mentioned and other related purposes, the technical solution of the present utility model is as follows:

[0007] A beam shaping system suitable for raising the nozzle of a processing head. The laser output by the beam shaping system passes through the nozzle and acts on the surface of the workpiece. The distance between the nozzle and the workpiece surface is not less than 10mm.

[0008] As a preferred solution, the beam shaping system includes a beam shaper,

[0009] The beam shaper is used to collimate the laser beam output by the laser and expand the system spherical aberration of the optical path structure; or,

[0010] The beam shaper is used to collimate the laser beam output by the laser, expand the aperture angle of the collimated beam before it is incident on the focusing mirror, and increase the incident height of the collimated beam.

[0011] As a preferred solution, the beam shaping system further includes a focusing mirror, which is arranged downstream of the beam shaper along the light output direction and is used to expand the distance between the focal points where each annular light is focused on the optical axis to form an axially multi-focal beam.

[0012] As a preferred solution, the beam shaper includes a collimating mirror and a cone lens arranged in sequence along the beam emission direction. The radius of curvature of the incident surface of the collimating mirror is greater than that of its exit surface, and / or the radius of curvature of the incident surface of the cone lens is greater than that of its exit surface.

[0013] As a preferred solution, the collimating mirror is a biconvex lens, and both the incident surface and the exit surface of the collimating mirror are spherical surfaces.

[0014] As a preferred solution, the focusing mirror is a positive meniscus lens, and both the incident surface and the exit surface of the focusing mirror are spherical surfaces.

[0015] As a preferred solution, the radius of curvature of the incident surface of the focusing mirror is greater than that of the exit surface of the focusing mirror.

[0016] As a preferred solution, the waist diameter of the beam exiting from the focusing mirror is greater than 0.5 mm, and the divergence angle is less than 20 mrad.

[0017] As a preferred solution, the beam shaping system further includes at least one pair of right-angle prisms, which are arranged between the beam shaper and the focusing mirror and are optically connected to each other. The pair of right-angle prisms is used to perform beam shrinking and shaping on the beam output from the beam shaper.

[0018] As another aspect of the present application, a laser processing head suitable for raising the nozzle is also proposed, which adopts the beam shaping system in any of the above solutions.

[0019] As described above, a beam shaping system provided by the present utility model is suitable for raising the nozzle of the processing head. The laser output by it passes through the nozzle and acts on the surface of the workpiece. The distance between the nozzle and the surface of the workpiece is not less than 10 mm. The beam shaping system provided by the present utility model is adapted to the nozzle of the laser processing head with an elevated design. The beam shaper in it is used to collimate the laser beam output by the laser and expand the system spherical aberration of the optical path structure; or, it is used to collimate the laser beam output by the laser, expand the aperture angle of the collimated beam before it is incident on the focusing mirror, and increase the incident height of the collimated beam.

[0020] The technical solution of this application not only collimates the laser beam output by the laser through the beam shaper, but also expands the system spherical aberration of the optical path structure or expands the aperture angle of the collimated beam before it enters the focusing mirror and increases the incident height of the collimated beam. By using spherical aberration, the beam is focused at different positions on the optical axis. The axially multi-focal beam formed in this way can be not affected by the nozzle with an elevated design during the processing operation, and can meet the defocus use requirements of the laser processing head, effectively preventing the metal spatter and the return light generated during the processing from entering the nozzle interior, causing internal blockage and optical path damage. Moreover, the divergence angle of the beam output from the laser processing head of the present utility model is extremely small, the change rate of the spot size is low, and the nozzle is less heated. When the lens has a temperature drift, the influence of the beam output from the laser processing head of the present utility model on the consistency of the processing section is also small. It can solve the problems in the prior art that the elevated nozzle does not match the conventional optical path structure, the nozzle is severely heated, and the processing efficiency is low. Brief Description of the Drawings

[0021] One or more embodiments are exemplarily illustrated by the pictures in the corresponding attached drawings. These exemplifying illustrations do not constitute limitations on the embodiments. Elements with the same reference numerals in the attached drawings are represented as similar elements, unless otherwise stated, the drawings in the attached drawings do not constitute a proportional limitation.

[0022] Figure 1 is a schematic diagram of the position where laser converges in the prior art processing;

[0023] Figure 2 is a schematic diagram of the optical path structure in an embodiment of this application;

[0024] Figure 3 is adopted Figure 2 the schematic diagram of the effect that can be achieved after the optical path structure in;

[0025] Figure 4 is a schematic diagram of the structure of the plano-concave conical lens provided in this embodiment;

[0026] Figure 5 is a schematic diagram of the structure of the plano-convex conical lens provided in this embodiment;

[0027] Figure 6 is a schematic diagram before the improvement of the optical path structure;

[0028] Figure 7 is adopted Figure 6 the schematic diagram of the effect achieved after the optical path structure in;

[0029] Figure 8 is a schematic diagram of the optical path structure in another embodiment of this application;

[0030] Figure 9 is a schematic diagram of the optical path structure in another embodiment of this application;

[0031] Figure 10 This is a schematic diagram of the principle of using a prism to align collimated light to achieve lateral beam narrowing in an embodiment of the present application. Detailed implementation manners

[0032] For ease of understanding the present utility model, the present utility model will be described in more detail below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is expressed as "fixed to" another element, it can be directly on the other element, or there can be one or more intermediate elements therebetween. When an element is expressed as "electrically connected to" another element, it can be directly connected to the other element, or there can be one or more intermediate elements therebetween. The terms "upper", "lower", "inner", "outer", "bottom", etc. used in this specification indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation to the present utility model. In addition, the terms "first", "second", "third", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0033] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by those skilled in the technical field to which the present utility model belongs. The terms used in the specification of the present utility model are only for the purpose of describing specific embodiments and are not used to limit the present utility model. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0034] In addition, the technical features involved in different embodiments of the present utility model described below can be combined with each other as long as they do not conflict with each other.

[0035] The spot diameter of the focused beam output by the existing laser processing head is small, and the focal depth is limited. On the one hand, it is easy to cause a relatively thin cut / weld seam formed when it is applied to process medium-thick metal plates, with low laser energy utilization rate and being unfavorable for slag removal; on the other hand, even if the laser penetrates the plate, the material removal at the bottom of the plate is inconsistent, and a large amount of molten slag adheres, resulting in poor quality of the cut / weld joint.

[0036] Regarding the problem of poor processing quality in the medium and thick plate scenario, the focusing position of the output laser is usually adjusted to enable the processing head to achieve the same processing effect as that in the processing of thin plates in the application of medium and thick plate processing. Specifically, for example, in cutting applications, the height of the processing head is mechanically adjusted to adjust the focusing position of the output beam of the processing head. However, the nozzle height H (the distance between the bottom of the nozzle and the surface to be cut is defined as the nozzle height H in the industry) has a certain adjustment range, which is limited by the parameter limit of the air flow rate output by the nozzle. To ensure the air flow rate, the adjustment range of the relative height H between the nozzle and the workpiece surface is small (its height H is usually between 2 mm and 5 mm). The thickness of medium and thick plates is usually greater than 4.5 mm. That is to say, in the prior art, by translating the processing head to change its height and further adjusting the focal position, some processing requirements cannot be met. In some other solutions, a beam shaping system can also be designed in the laser processing head, and the adjustable optical axis direction spacing of the internal mirror group is set to achieve the zoom function, so that the focusing position of the laser is axially adjustable. Based on the axially adjustable focusing position function, subsequent negative defocus cutting processes for materials such as stainless steel and positive defocus cutting processes for materials such as carbon steel have been derived.

[0037] Exemplarily, such as Figure 1 In (1a) of shows a schematic diagram of the laser convergence position during the negative defocus operation of the laser processing head (only the nozzle part is shown). Such as Figure 1 In (1b) of shows a schematic diagram of the laser convergence position during the non-defocus operation of the laser processing head (only the nozzle part is shown). Such as Figure 1 In (1c) of shows a schematic diagram of the laser convergence position during the positive defocus operation of the laser processing head (only the nozzle part is shown).

[0038] Combined with Figure 1 In (1a), (1b), and (1c) of , the nozzle height H of the laser processing head is small. When cutting, a large amount of dust and smoke will be formed, and these impurities will adhere to the protective lens (not shown) of the laser processing head, which easily leads to power attenuation and optical path heat loss. And when the nozzle height H is too small, the probability of these impurities entering the nozzle and the interior of the processing head can be significantly increased. Also, due to the too small nozzle height, when the nozzle faces a complex surface, limited by the spatial position of the nozzle, it cannot reach the predetermined position for operation, resulting in poor cutting effect; and due to the low flatness of the workpiece, it is easy to hit the plate, which is not conducive to mass production. Such as Figure 1 As shown in (1c) and (1d) of , by increasing the nozzle height H, the probability of impurity adhesion can be reduced, the reliability of laser processing can be improved, the replacement frequency of consumables can be reduced, and the adaptability to cutting complex surfaces can be improved.

[0039] However, when the nozzle height is raised, such as Figure 1As shown in (1a), when the laser beam is in negative defocus operation, the waist radius of the laser beam is located below the surface of the workpiece material. Due to the divergence of the laser, when the negative defocus degree of the focus of the laser beam is too large, the light beam at the edge of the laser beam will be blocked by the nozzle. Although most of the energy of the laser beam is concentrated at the axis of the light beam, the laser for processing medium and thick plates is a high-power laser (usually above 5kw), and the edge light beam will still cause the temperature of the nozzle to continue to increase until the temperature is too high, resulting in the shutdown of the laser cutting system, which will affect the stability of the laser processing head and the equipment availability. When the nozzle height is raised, as Figure 1 shown in (1e), in order to prevent the edge of the laser beam from being blocked by the nozzle, the negative defocus depth of the laser beam will actually be reduced, resulting in poor negative defocus cutting effect of the laser processing head, or even unable to perform negative defocus operation.

[0040] To overcome the defects existing in the above-mentioned prior art, an embodiment of the present invention provides a beam shaping system suitable for raising the nozzle of the processing head. In one embodiment, the beam shaping system includes, arranged in sequence along the laser transmission direction: a beam shaper 11 and a focusing lens 13, as shown in Figure 2 . Among them, the beam shaper 11 is used to collimate the laser beam output by the laser and expand the system spherical aberration of the optical path structure; or

[0041] The beam shaper is used to collimate the laser beam output by the laser, expand the aperture angle of the collimated beam before it enters the focusing lens, and increase the incident height of the collimated beam.

[0042] The focusing lens 13 is arranged downstream of the beam shaper 11 along the light output direction, and is used to expand the distance between the foci where each annular light is focused on the optical axis, so as to form an axially multi-focus beam.

[0043] In one embodiment, the beam shaper includes a collimating mirror 111 and a cone lens 112 arranged along the beam emission direction. The collimating mirror 111 is used to collimate the laser beam output by the laser; the cone lens 112 is arranged downstream of the collimating mirror 111 to expand the aperture angle of the collimated beam before it enters the focusing lens 13 and increase the incident height of the collimated beam; the focusing lens 13 is used to converge each annular light with different incident heights in the laser beam to different positions along the optical axis direction, forming an axially multi-focus beam.

[0044] When the optical path structure shown in Figure 2 is applied to cutting, the effect is as shown in Figure 3 . The spot formed at the positive focus position is annular, and the spot formed at the negative focus position maintains a circular shape. The spot diameter at the waist is larger than that without adding the beam shaper, the beam divergence angle is reduced, and the change of the spot size along the optical axis direction is relatively slow, which is beneficial to reducing the sensitivity of the cutting process to the focus.

[0045] Optionally, the beam shaping system further includes a driving unit, which is connected to the collimating mirror 111 and is used to drive the collimating mirror 111 to move along the optical axis to adjust the energy distribution of the collimated beam, so that the energy of the collimated beam is evenly distributed along the optical axis, thereby improving the axial utilization rate of the collimated beam. Optionally, the driving unit can adopt a vibration motor. It can be understood that by driving the collimating mirror to move along the optical axis, the energy can be evenly distributed on a certain section of the optical axis, realizing an optical energy state with a long depth of field to achieve high-speed cutting.

[0046] In this embodiment, the beam shaper raises the incident height of the laser beam, and further reversely curves the focusing mirror, so that the focusing position of the laser beam on the optical axis is dispersed, that is, the beam is focused at different positions on the optical axis by using aberration, and there is a certain distance between each focusing position. The axially multi-focal beam formed in this way can be not affected by the nozzle with an elevated design during the processing operation, can meet the defocusing use requirements of the laser processing head, and effectively prevent the metal spatter and the return light generated during the processing from entering the nozzle, causing internal blockage and optical path damage. At the same time, the present application also drives the collimating mirror to vibrate along the optical axis at a predetermined frequency through the driving unit to adjust the energy distribution of the collimated beam, so that the energy of the collimated beam is evenly distributed along the optical axis, thereby improving the axial utilization rate of the collimated beam.

[0047] In the prior art, the spot diameter of the focused beam output from a conventional laser processing head is usually small, and the focal depth is limited. When it is applied to cutting medium and thick metal plates, due to the small spot diameter, the formed cutting seam is thin, which is not conducive to cutting slag removal. Even if the laser penetrates the plate, the material removal at the bottom of the plate is inconsistent, a large amount of slag adheres, and the cut quality is poor. For the problem of poor quality in the medium and thick plate scenario, usually, the focusing position of the output laser is adjusted to obtain the same processing effect as cutting thin plates during cutting of medium and thick plates. However, the nozzle height H of the laser processing head has a certain adjustment range, and the focusing position can be adjusted by mechanically adjusting the height H of the processing head; this adjustment range is limited by the parameter limit of the gas flow rate output by the nozzle. To ensure the gas flow rate, the adjustment range of the relative height H between the nozzle and the surface to be processed is small (its height H is usually between 2 mm and 5 mm; in the industry, the distance between the bottom of the nozzle and the surface to be cut is defined as the nozzle height H), which is only applicable to thin plate welding with a thickness between 0.5 mm and 4 mm. The thickness of medium and thick plates is usually greater than 4.5 mm, which makes it impossible to meet the actual application requirements by translating the processing head to change the overall height of the processing head and further change the focusing position.

[0048] Such as Figure 6As shown, a conventional laser processing head only has a collimator 111 and a focusing lens 13, and the collimator is usually fixedly arranged. After the collimated beam exits from the collimator 111, it enters the incident surface of the focusing lens 13 at the same incident height as before and with a 0° aperture angle. To reduce the optical medium surfaces of the beam shaping system and simplify the system design, the focusing lens 13 usually adopts a biconvex lens for converging the beam. When designing the focusing lens 13, the method of curve matching is used to eliminate aberrations, so as to eliminate the aberrations of the optical path system as much as possible and make the laser beam converge at the same position on the optical axis as much as possible.

[0049] Adopting a laser processing head with the optical path structure as Figure 6 shown, the spots formed at the positive focus and the negative focus are both circular spots. The spot diameter at the beam waist is small, and the optical path for processing is short, as Figure 7 shown.

[0050] In an embodiment of the present invention, a cone lens 112 is added between the collimator 111 and the focusing lens 13, and in cooperation with the collimator vibrating along the optical axis direction at a predetermined frequency, the direction of the collimated beam is changed. At the same time, the beam enters the focusing lens 13 at a certain aperture angle after exiting from the beam shaper 11, and at the same time, the incident height of the beam is increased, so that the spot area of the collimated beam incident on the focusing lens 13 is larger. That is, the beam that should originally enter the focusing lens 13 from the paraxial region is changed to enter the focusing lens 13 from a relatively off-axis region. The driving unit drives the collimator to vibrate and adjusts the vibration frequency of the collimated beam, so that the energy of the laser can be evenly distributed in a specific area per unit time, thereby realizing uniform heating of the molten pool formed on the surface of the workpiece, which is beneficial to reducing the spatter generated during the processing.

[0051] It should be noted that for the focusing lens 13 (spherical lens) used to achieve the converging effect in the present invention, the image-side intercept of the beam incident from the off-axis region is smaller than that of the beam incident from the paraxial region. Therefore, the converging point of the beam incident from the off-axis region on the optical axis is closer to the exit surface of the focusing lens 13 than that of the beam incident from the paraxial region; based on the above principle, the beam shaper 11 is set to make the spot area of the collimated beam larger, which makes the beam enter the focusing lens at a higher incident height, and finally makes the focusing position of the laser beam on the optical axis more dispersed, and there are multiple focusing positions of the beam on the optical axis.

[0052] Among them, to cooperate with the beam shaper 11, the focusing lens 13 provided in this embodiment adopts a double convex spherical lens to minimize the cost of the optical path system. Moreover, during its design, the curvature matching method is used in reverse to increase the aberration of the focusing lens (adjust the curvature ratio of the incident surface and the exit surface of the focusing lens for the purpose of increasing the aberration), so that the distance between the focusing positions of the beams incident from the off-axis region on the optical axis is greater than that of the beams incident from the paraxial region on the optical axis, so as to further disperse the focusing positions of the laser beam on the optical axis and expand the spacing of each focusing position; through the cooperation of the axicon lens and the focusing lens, as Figure 1 and Figure 2 shown, D3 > L3, D2 > L2, D1 > L1, the spacing of each focusing position (F0, F1, F2, F3) on the optical axis increases, so that the depth of focus DOF of the formed beam increases, and while meeting the requirements of negative defocus operation, the edge of the beam will not be blocked by the raised nozzle.

[0053] At the same time, it should be additionally noted that in the scenario of cutting medium and thick plates with high-power lasers, the laser beam formed by the conventional zoom system is a Gaussian beam, and the energy density at the focal position of the laser beam is too large, which is prone to hole explosion during operation and is not conducive to slag discharge. Therefore, laser cutting is usually performed at a position with a slightly larger spot diameter. In actual processing applications, each plate thickness and each material has a relatively appropriate spot size.

[0054] Using the beam shaping system provided in this embodiment as shown in Figure 2 can move the energy of the beam waist part to the negative defocus direction, which can improve the negative defocus cutting efficiency, and the spot diameters of the beams acting on the material are relatively small, and the change degree of the energy density is small, which can avoid the section being stepped and is conducive to reducing hole explosion. And compared with Figure 1 and Figure 2 , due to the limitation requirements of the cutting process on the spot size, when the same spot size acts on the material surface, Figure 2 the formed cutting beam requires a deeper negative defocus depth than Figure 1 the formed cutting beam to meet the operation requirements. A relatively deeper defocus depth (the nozzle height remains unchanged) will result in higher beam energy acting on the nozzle, which not only causes the nozzle to get hot but also reduces the energy utilization rate; Figure 1 the formed cutting beam compared with Figure 2 the formed cutting beam can meet the spot size requirements only by adjusting the defocus depth of the beam within a small depth range. At the same time, the divergence angle of the beam segment acting on the inside of the material is small, and the change rate of the spot size is low. When the lens has temperature drift, it will not affect the consistency of the cutting section due to temperature drift.

[0055] As an example, as Figure 4As shown, the conical lens 112 is a plano-concave conical lens, with its concave surface as the incident surface. The cone angle of the concave surface is between 0.5° and 3°. Moreover, in order to prevent the incident surface from forming a sharp surface, the paraxial region of the plano-concave conical lens is set as a smooth surface, such as a smooth spherical surface that is smoothly connected to the conical surface, to avoid heat concentration. When a plano-concave conical lens is used and the focusing lens has a reverse curvature design, due to different incident heights of the incident light beam, it converges at different positions on the optical axis respectively.

[0056] As another example, the conical lens 112 uses Figure 4 the shown plano-concave conical lens, where the cone angle of the concave surface is between 0.5° and 3°. However, its planar surface is used as the incident surface and the concave surface is used as the exit surface. Also, the paraxial region of the plano-concave conical lens is set as a smooth surface, which can also increase the incident height of the collimated light beam and cooperate with the focusing lens with a reverse curvature design to form a multi-focus light beam.

[0057] As another example, as Figure 5 shown, the conical lens 112 is a plano-convex conical lens, with its planar surface as the incident surface and the convex surface as the exit surface. The cone angle of the convex surface is between 0.5° and 3°. Also, the paraxial region of the plano-convex conical lens is set as a smooth surface, which can also increase the incident height of the collimated light beam and cooperate with the focusing lens with a reverse curvature design to form a multi-focus light beam. When using a plano-convex conical lens, sufficient space needs to be reserved between the conical lens and the focusing lens, and its length is longer than that of the beam shaping system using a plano-concave conical lens.

[0058] As another example, as Figure 5 shown, the conical lens 112 is a plano-convex conical lens, with its convex surface as the incident surface and the planar surface as the exit surface. The cone angle of the convex surface is between 0.5° and 3°. Also, the paraxial region of the plano-convex conical lens is set as a smooth surface, which can also increase the incident height of the collimated light beam and cooperate with the focusing lens with a reverse curvature design to form a multi-focus light beam.

[0059] As another embodiment of the present application, please refer to Figure 8 and Figure 9 . Its optical path structure includes: a collimating mirror 111 and a focusing mirror 13. Among them, the collimating mirror 111 is used to receive the divergent laser and convert the divergent laser into collimated light that exits parallelly. That is, the laser exiting from the collimating mirror can be approximated as a collimated light beam. Moreover, it is also used to expand the spherical aberration of the optical path system. The focusing mirror 13 is used to converge the collimated light beam onto the optical axis to form a focused light beam. Moreover, it is also used to increase the aperture of the optical path system to form an axial multi-focus light beam.

[0060] As an example, as Figure 8As shown, the collimating mirror 111 is a double convex lens, and the focusing mirror 13 is also a double convex lens. Moreover, the surface with a smaller radius of curvature in the collimating mirror 111 faces the collimated beam, and the surface with a larger radius of curvature faces the divergent beam. The surface with a smaller radius of curvature in the focusing mirror 13 faces the collimated beam, and the surface with a larger radius of curvature faces the converging beam, so as to minimize the spherical aberration; each lens adopts Figure 8 The size relationship of the radius of curvature ratio of the structure shown can make the formed focusing beam converge as much as possible at the same position on the optical axis. However, due to the use of spherical lenses, the spherical aberration of the system can only be corrected and reduced as much as possible and cannot be completely eliminated. As Figure 8 shown, the beams of different annuli (different incident heights) are focused at different axial focusing positions on the optical axis (the focusing position is the intersection of the converged beams of different annuli and the optical axis).

[0061] As an example, as Figure 9 shown, the collimating mirror 111 is a double convex lens. The surface with a smaller radius of curvature of this double convex lens faces the divergent beam, and the surface with a larger radius of curvature faces the collimated beam. That is, the collimating mirror 111 adopts reverse curvature matching, making the radius of curvature of the incident surface larger than that of the exit surface, increasing the spherical aberration while satisfying the collimation function; the focusing mirror 13 is a spherical meniscus lens. Moreover, the surface with a smaller radius of curvature faces the collimated beam, and the surface with a larger radius of curvature faces the converging beam. That is, a positive meniscus lens is adopted. The positive meniscus lens can increase the system NA of the optical path structure. The larger the NA, the larger the spherical aberration, and it can increase the distance between the axial focusing positions of the focusings of different annuli on the optical axis. It should be noted that the collimated beam formed by the collimating mirror 111 provided in this embodiment is a weakly collimated beam, which is not a strictly parallel beam. While satisfying the magnification design requirements, since it also undertakes the design function of increasing the spherical aberration, therefore, in the output beam, the beam of the edge annulus (off-axis) forms a certain angle with the optical axis relative to the beam of the near-axis annulus, so that the beam with a higher incident height is incident on the focusing mirror 13 from the more edge of the collimating mirror 111. The increase in the incident height can increase the distance between the axial focusing positions.

[0062] Through the cooperation of the collimating mirror 111 and the focusing mirror 13, as Figure 8 and Figure 9As shown, D3 > L3, D2 > L2, D1 > L1. The spacing limit of each focusing position (F0, F1, F2, F3) on the optical axis increases, increasing the depth of focus DOF of the formed light beam. While meeting the requirements of negative defocus operation, the edge of the light beam will not be blocked by the raised nozzle. At the same time, it should be additionally noted that in the scenario of cutting medium and thick plates with high-power lasers, the laser beam formed by the conventional zoom system is a Gaussian beam. The energy density at the focus position of the laser beam is too high, and it is easy to explode holes during operation and is not conducive to slag discharge. Therefore, laser cutting is usually carried out at a position with a slightly larger spot diameter. In actual processing applications, each plate thickness and each material have their own relatively appropriate spot size.

[0063] As a comparison, using the Y1 segment shown in Figure 8 to act on the material for cutting, since the plate thickness is greater than the depth of focus, the spot diameter in the Y1 segment increases synchronously in a certain proportion with the divergence angle of the laser beam. The change rate of the spot size is large, the change degree of the energy density is large, the cut seam is stepped, most of the cutting waste residues accumulate and cannot be discharged downward, normal perforation cannot be carried out, and even explosion holes may occur, returning the waste residues to the original optical path, piercing the protective mirror, and damaging the processing head. Using the laser processing head with the optical path structure shown in Figure 2 of this embodiment, the energy of the beam waist part is moved to the negative defocus direction, which can improve the negative defocus cutting efficiency, and the spot diameters of the light beams acting on the material are relatively small, the change degree of the energy density is small, the stepped shape of the cut surface can be avoided, and it is beneficial to reduce explosion holes. And, comparing Figure 8 and Figure 9 , due to the limitation requirements of the cutting process on the spot size, when using the same spot size to act on the material surface, Figure 8 the formed cutting light beam requires a deeper negative defocus depth than Figure 9 the formed cutting light beam to meet the operation requirements. A relatively deeper defocus depth (the nozzle height remains unchanged) will result in a higher beam energy acting on the nozzle, which not only causes the nozzle to heat up but also reduces the energy utilization rate;

[0064] It can be understood that Figure 9 the formed cutting light beam relative to Figure 8 the formed cutting light beam can meet the spot size requirements only by adjusting the defocus depth of the light beam within a small depth range. At the same time, the divergence angle of the light beam segment acting on the material inside is small, and the change rate of the spot size is low. When the lens has temperature drift, the consistency of the cutting section will not be affected by the temperature drift.

[0065] Optionally, Figure 9 the beam waist diameter of the formed focused light beam is greater than 0.5 mm, while Figure 8The formed focused beam waist diameter is usually less than 0.1 mm. A larger beam waist diameter is not suitable for fine cutting of thin plates, but can be adapted to cutting medium and thick plates. And due to the low change rate of the spot size, the cutting section has better consistency.

[0066] In this application, a prism pair 10 can also be used to refract and linearly scale the collimated beam at least once to achieve lateral beam shrinking of the laser beam. The principle of using the prism pair 11 to achieve lateral beam shrinking of the collimated light is as Figure 1 of 10 shown. This principle has been shown in "Design of Shaping Prisms for Semiconductor Laser Systems" (Zhang Ping, note in 1990), so it will not be elaborated in this application.

[0067] Arrange the first right-angle prism 101 and the second right-angle prism 102 at a predetermined spatial position in the optical path. The collimated beam emitted from the collimator 111 enters through a right-angle surface of the first right-angle prism and exits through the inclined surface of the second right-angle prism, which is beneficial to reducing the spot diameter at the beam waist, achieving a higher energy density and a better focusing effect, and ensuring that the edge shape of the processing beam is clear.

[0068] It should be noted that the collimator mentioned in this embodiment should be understood as a lens group for realizing the collimation function. Its collimation function can be realized by a single lens or by the cooperation of multiple lenses; in the beam shaping system of the laser processing head, multiple protective lenses can be added to realize the sealing protection of the collimator and the focusing lens, and a beam splitter can be added to realize the process monitoring of laser processing. To avoid redundancy, it is not shown in the laser processing head structure of this application, and these lenses can be selected in actual applications.

[0069] It should be noted that the collimator mentioned in this embodiment should be understood as a lens group for realizing the collimation function. Its collimation function can be realized by a single lens or by the cooperation of multiple lenses; in the optical path structure of the laser output head, multiple protective lenses can be added to realize the sealing protection of the collimator and the focusing lens, and a beam splitter can be added to realize the process monitoring of laser processing. To avoid redundancy, in Figure 1 the shown laser processing head structure, it is not shown, and these lenses can be selected in actual applications.

[0070] In addition, to improve the focusing effect of the beam output by the beam shaping system, the beam shaping system further includes at least one group of right-angle prism pairs. The right-angle prism pair is arranged between the beam shaper and the focusing lens, and the three are optically connected. The right-angle prism pair is used to shrink and shape the beam output from the beam shaper.

[0071] As Figure 1 of 10As shown, the first right-angle prism 101 and the second right-angle prism 102 are arranged at predetermined spatial positions in the optical path. The collimated beam emitted from the autocollimator 11 enters through a right-angle face of the first right-angle prism and exits through the inclined face of the second right-angle prism, which is beneficial for reducing the spot diameter at the beam waist, achieving a higher energy density and a better focusing effect, and ensuring a clear edge shape of the processing beam.

[0072] It can be understood that when the right-angle prism pair is configured as one, and the first collimated beam with a circular cross-sectional shape exits from the right-angle prism pair, a second collimated beam with an elliptical cross-section is formed (that is, the beam is compressed in one direction and remains unchanged in the other direction). By utilizing the refraction effect of the prism and the linear scaling effect on the laser collimated beam, the shaping and beam shrinking of the collimated light are achieved.

[0073] In some embodiments, when the right-angle prism pair is configured as two (adding another prism group based on the above-mentioned one right-angle prism pair) and arranged at a certain spatial position, a third collimated beam with a smaller cross-sectional area than that of the first collimated beam can be formed (achieving the compression of the beam in two mutually perpendicular directions), and the cross-section of the third collimated beam is also circular. In this embodiment, the first right-angle prism pair causes the beam to change in the XY direction, and the second right-angle prism pair causes the beam to change in the XZ direction. It should be noted that the principle of using the prism pair 11 to achieve lateral beam shrinking of the collimated light has been shown in "Design of Shaping Prisms for Semiconductor Laser Systems" (Zhang Ping, 1990 note), so it will not be elaborated in this application.

[0074] Based on the above, the present application also proposes a laser processing head suitable for raising the nozzle, which adopts the beam shaping system in any of the above solutions, and thus also has all the beneficial effects of this beam shaping system.

[0075] In summary, for the beam shaping system of a laser processing head suitable for raising the nozzle described in the present utility model, the laser output therefrom passes through the nozzle and acts on the surface of the workpiece, and the distance between the nozzle and the workpiece surface is not less than 10 mm. The beam shaping system provided by the present utility model is adapted to the nozzle of the laser processing head designed to be raised. The beam shaper therein is used to collimate the laser beam output from the laser and expand the system spherical aberration of the optical path structure; or, it is used to collimate the laser beam output from the laser, expand the aperture angle of the collimated beam before it enters the focusing mirror, and increase the incident height of the collimated beam.

[0076] The technical solution of this application not only collimates the laser beam output by the laser through the beam shaper, but also expands the system spherical aberration of the optical path structure or expands the aperture angle of the collimated beam before it enters the focusing mirror and increases the incident height of the collimated beam. By using the spherical aberration, the beam is focused at different positions on the optical axis. Thus, the axially multi-focus beam formed can be not affected by the nozzle with an elevated design during the processing operation, and can meet the defocus use requirements of the laser processing head, effectively preventing the metal spatter and the retro-reflected light generated during the processing from entering the nozzle interior, causing internal blockage and optical path damage. Moreover, the divergence angle of the beam output from the laser processing head of the present utility model is extremely small, the change rate of the spot size is low, and the nozzle is less heated. When the lens has a temperature drift, the influence of the beam output from the laser processing head of the present utility model on the consistency of the processing section is also small. It can solve the problems in the prior art that the elevated nozzle is not compatible with the conventional optical path structure, the nozzle is severely heated, and the processing efficiency is low. Therefore, the present utility model effectively overcomes various disadvantages in the prior art and has high industrial utilization value.

[0077] The above embodiments are only illustrative of the principles and effects of the present utility model, and are not used to limit the present utility model. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present utility model. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present utility model should still be covered by the claims of the present utility model.

Claims

1. A beam shaping system suitable for raising the nozzle of a processing head, characterized in that: The beam shaping system includes a beam shaper, and the beam shaper includes a collimator and an aconic lens arranged in sequence along the beam emission direction. The collimating mirror is used to collimate the laser beam output by the laser; The curvature radius of the incident surface of the axicon is greater than the curvature radius of the exit surface thereof, so as to enlarge the aperture angle of the collimated light beam before it is incident on the focusing lens and increase the incident height of the collimated light beam; The beam shaping system further includes a focusing mirror, which is arranged downstream of the beam shaper along the light output direction and is used to expand the distance between the focal points of each annular light on the optical axis to form an axial multi-focus beam; The laser output by the beam shaping system passes through the nozzle and acts on the surface of the workpiece, and the distance between the nozzle and the surface of the workpiece is not less than 10 mm.

2. The beam shaping system according to claim 1, wherein: The collimating lens is a double convex lens, and both the incident surface and the exit surface of the collimating lens are spherical.

3. The beam shaping system according to claim 1, wherein: The focusing mirror adopts a positive meniscus lens, and both the incident surface and the exit surface of the focusing mirror adopt spherical surfaces.

4. The beam shaping system according to claim 1, wherein: The curvature radius of the incident surface of the focusing mirror is greater than the curvature radius of the exit surface of the focusing mirror.

5. The beam shaping system according to claim 1, wherein: The beam waist diameter of the light beam emitted by the focusing mirror is greater than 0.5 mm, and the divergence angle is less than 20 mrad.

6. The beam shaping system according to claim 1, wherein: The beam shaping system further includes at least one pair of right-angle prisms, which are arranged between the beam shaper and the focusing lens, and the three are optically connected. The right-angle prisms are used to perform beam shrinkage shaping on the light beam output from the beam shaper.

7. A laser processing head suitable for raising the processing head nozzle, characterized in that: A beam shaping system as described in any one of claims 1 to 6 is used.

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