Laser cutting heads for machine tools

Abstract

A laser cutting head (1) capable of being associated with a machine tool comprises: a calibration component (2) for calibrating a laser beam (L) from a laser emitting device; a focusing component (5) for focusing the calibrated laser beam (L) at a focal point (F); an optical element (8, 38) for receiving the focused laser beam (L) and reflecting a focused first portion (L1) of the laser beam; and a wavefront sensor (9) for receiving the focused first portion (L1) of the laser beam (L), performing a phase measurement on the focused first portion (L1), obtaining a reconstructed wavefront based on the phase measurement, and sending the reconstructed wavefront to an electronic processor (12); the electronic processor compares the reconstructed wavefront with a reference wavefront, determines one or more optical aberrations to which the laser beam (L) is subjected, reduces such aberrations and changes the focal point (F).

Description

Technical Field

[0001] The present invention relates to a laser cutting device for a cutting machine tool, and more particularly to a laser cutting head used in a fiber laser cutting system in a cutting machine or a combined cutting / punching machine for metal sheets. Background Art

[0002] The use of laser systems for cutting, engraving and welding workpieces is known and widely used in the field of machine tools for processing metal sheets and plates.

[0003] As is known, a laser is a device capable of emitting monochromatic light by means of a stimulated emission process, i.e., monochromatic light having a single wavelength, being spatially coherent and concentrated in a beam having a very high luminosity (brightness). The ability to concentrate a large amount of energy in a very small area allows laser devices to cut, engrave, and weld metals. Cutting of metallic materials usually occurs by vaporization and, in particular, by melting. In the case of cutting metallic materials by melting, the laser beam melts a small area of ​​the workpiece and the molten metal (slag) is removed by blowing or ejecting gas.

[0004] In laser emitting equipment, different types of sources can be used to generate a laser beam suitable for cutting metals. Commonly used are gas lasers (carbon dioxide, carbon monoxide CO2) and solid-state lasers (doped glass laser diodes and fiber lasers).

[0005] Since high energy is required to cut sheet metal, even sheet metal with a large thickness, the size and weight of the laser emitting device prevent the laser emitting device from being directly positioned on the machine tool. To overcome this disadvantage, a laser cutting head or a simpler cutting head or focusing head can be positioned on the machine tool and connected to the laser emitting device via an optical chain (CO2 laser) or a transmission fiber (optical fiber, such as in a YAG laser diode) to emit the laser beam generated by the emitting device and focus the laser beam on the workpiece. Due to the small size and low weight of the cutting head, the cutting head can actually be moved accurately and quickly by the machine tool to cut the product.

[0006] In so-called fiber laser cutting systems in which a fiber optic cable with a diffuser prism is used to bring the laser beam to the cutting head, the cutting head typically includes a calibration assembly that transmits the light beam exiting the optical fiber to a focusing assembly that is capable of focusing the laser beam on the workpiece, i.e., the focusing assembly is capable of positioning the focal point or focus of the laser beam in a set point that is located on the surface of the workpiece, immediately above such surface, or immediately below such surface.

[0007] The focused laser beam exits the cutting head through a nozzle that focuses a gas puff or jet, which serves to remove the slag generated by the melting of the metal and minimizes its ability to reach the focusing assembly. For this purpose, a transparent element or protective window or glass is provided at the nozzle, separating the interior of the cutting head from the external environment and allowing the laser beam exiting the focusing assembly to pass through.

[0008] Accurate positioning of the focal point where all the energy of the laser beam is concentrated is crucial to properly cutting the material.

[0009] However, laser cutting heads, especially those with high power, are subject to a phenomenon generally referred to as "thermal focus shift", which results in a defocused or blurred optical aberration, i.e., the phenomenon causes the focus to shift relative to the desired and optimal point (on the surface of the piece or just below or just above the piece), as better explained below.

[0010] As is known, a small portion of the energy of the laser beam that passes through the lenses of the collimating and focusing optics is absorbed and converted into heat, primarily due to the non-absolute transparency of the optical elements (coating or substrate). Contamination and / or damage to surface layers typically provided on the lens surfaces can also lead to additional heat absorption.

[0011] Therefore, prolonged use of a machine tool, especially one with extremely high laser power, leads to considerable heat absorption and, consequently, to an increase in the temperature of the entire cutting head. This temperature increase affects all optical elements forming the cutting head, namely, the diffusion prism of the transmission fiber, the collimating assembly, the focusing assembly, and the separator glass (particularly the focusing assembly and the separator glass, which are located very close to the workpiece or in a melting area of ​​the workpiece where very high temperatures are concentrated), and can lead to changes in both the refractive index of the lens and the shape of the lens.

[0012] Changes in refractive index and lens shape caused by temperature increases result in a shift in the focal point.

[0013] In order to compensate for the phenomenon of "thermal focus shift", the position of the focus point can be adjusted by appropriately moving the lenses of the focusing assembly, which lenses are mounted on corresponding trays or lens-carrying slides that can be moved linearly along an adjustment direction parallel to the direction of the laser beam to allow focusing of the laser beam. Alternatively, if it is appropriate or necessary to keep one or more lenses of the focusing assembly fixed, the correct positioning of the focus point on the workpiece is achieved by appropriately moving the lenses of the calibration assembly, which lenses are mounted on corresponding trays or slides that can be moved linearly.

[0014] The movement of the focusing or calibration assembly can be controlled manually by an operator through visual inspection of the laser beam projected on the workpiece, or by numerical control based on automatic measurement of the displacement of the focus point.

[0015] However, visual inspection and manual control limit the accuracy and repeatability of cutting to the operator's ability and hardly produce high-quality processing. On the other hand, the measurement of focus shift requires a lot of time and expensive equipment and means an increase in machine tool costs.

[0016] In addition, thermal absorption can also lead to a series of other aberrations such as spherical aberration, coma and astigmatism, which can also affect the wavefront of the laser beam. In particular, these aberrations can also affect the distribution of electromagnetic intensity within the laser beam, thereby causing the cutting features to be attenuated or unable to be cut. Summary of the Invention

[0017] The object of the present invention is to improve the known laser cutting heads, in particular fiber laser cutting heads, used in cutting machines or combined cutting / punching machines for sheet metal.

[0018] Another object is to obtain a laser cutting head capable of ensuring cutting precision and repeatability, in particular at extremely high laser powers and also under intensive and prolonged use of the machine tool on which the laser cutting head is mounted.

[0019] A further object is to obtain a laser cutting head which allows, in a simple and effective manner, to measure and reduce a plurality of optical aberrations affecting the wavefront of the laser beam exiting the cutting head.

[0020] Another object is to obtain a laser cutting head which has a compact shape and particularly limited dimensions and which is economical and easy to manufacture.

[0021] These and other objects are achieved by a laser cutting head according to the claims set out below. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The invention may be better understood and implemented with reference to the accompanying drawings which illustrate exemplary and non-limiting embodiments of the invention, in which:

[0023] - Figure 1 is a simplified cross section of a laser cutting head according to a first embodiment of the present invention;

[0024] - Figure 2 yes Figure 1 Simplified cross-section of a variant of a laser cutting head;

[0025] - Figure 3 is a simplified cross section of a laser cutting head according to various embodiments of the present invention. DETAILED DESCRIPTION

[0026] Figure 1 A first embodiment of a laser cutting head 1 according to the invention is shown, which can be associated with a machine element 100 , such as sheet metal, and a cutting machine or a combined cutting / punching machine for cutting.

[0027] The laser cutting head 1 can be powered by a laser emitting device (not shown in the figure) through an optical transmission device 4, such as an optical chain or a transmission fiber. In particular, the emitting device is a solid-state fiber laser stimulated emission device, such as a solid-state fiber laser stimulated emission device with high power, and the optical transmission device 4 includes an optical fiber cable for transmitting the laser beam L generated by the emitting device to the laser cutting head 1. The laser cutting head 1 can emit the laser beam L and focus the laser beam L on a focal point F, which is located on the surface 101 of the workpiece 100 facing the laser cutting head 1, or is located immediately below the surface 101, or is located immediately above the surface 101.

[0028] The laser cutting head 1 includes a calibration component 2 and a focusing component 5, wherein the calibration component 2 includes at least one calibration lens 3 for calibrating the laser beam L from the laser emitting device, and the focusing component 5 includes at least one focusing lens 6 for focusing the calibrated laser beam L leaving the calibration component 2 on a focal point F.

[0029] The supporting and moving device 7 is used to support at least one of the calibration component 2 and the focusing component 5, for example Figure 1 In the embodiment shown in FIG, only the focusing assembly 5 is supported, and at least one of the focusing assembly 5 is moved along the adjustment direction X to change the focus F of the laser beam L. The supporting and moving device 7 includes a linear guide device 71 for slidably supporting the focusing assembly 5 and guiding the focusing assembly 5 along the adjustment direction X, thereby preventing displacement and / or oscillation transverse to the adjustment direction X, which would cause a displacement of the focus F of the laser beam L and / or a change in the size and / or shape of the same focus F on the workpiece 100.

[0030] The laser cutting head 1 further comprises at least one optical element 8, which is configured to: receive the focused laser beam L exiting from the focusing assembly 5; reflect a focused first portion L1 of the received laser beam L at a given reflection angle, for example, a reflection angle between about 10° and about 100°; and transmit a focused second portion L2 of the received laser beam L to a focal point F. The optical element 8 is, for example, a beam splitter, in particular a beam splitter selected from a cubic beam splitter (CBS), an optical prism, and a semi-transparent mirror.

[0031] The housing device 15 of the laser cutting head 1 forms an inner space 20 , which is suitable for accommodating at least the calibration assembly 2 , the focusing assembly 5 , the supporting and moving device 7 and the optical element 8 .

[0032] The interior space 20 is closed and sealed in a gas-tight manner from the external environment of the laser cutting head 1, i.e., airtight. In other words, the housing device 15 prevents contaminants and foreign elements, in particular slag and solid and gaseous residues generated by laser cutting, from entering the interior space 20. These contaminants and foreign elements could dirty the collimating lens 3, the focusing lens 5, and the optical element 8 or endanger the operation of the supporting and moving device 7.

[0033] To this end, the housing device 15, which can have a generally cylindrical shape, a parallelepiped shape, or a complex geometric shape, is provided with: an inlet opening 51 coupled to the optical transmission device 4, which allows the laser beam L generated by the emission device to enter the interior space 20; a side opening 53, which is closed in a gas-tight manner by a transparent optical element 11, which serves to transmit the focused first portion L1 of the laser beam L toward the external environment; and an outlet opening 52, which is positioned at the cutting nozzle 30 and is closed in a gas-tight manner by a partition glass 32. The partition glass 32, in addition to being suitable for separating the interior space 20 of the laser cutting head 1 from the external environment, also allows the collimated and focused laser beam L, in particular the focused second portion L2, to be transmitted from the laser cutting head 1 toward the external environment.

[0034] The cutting nozzle 30 concentrates the blowing or ejection of gas intended to remove slag generated by melting the workpiece 100 and at the same time helps reduce the possibility that the slag can reach the interior of the laser cutting head 1 in the event of the above-mentioned consequences.

[0035] The linear guide 71 and the further anti-rotation device are also accommodated inside the housing device 15 and, in particular, are fixed to the inner wall of the housing device 15. The anti-rotation device, of a known type and not shown in detail in this figure, is arranged to prevent the supporting and moving device 7 from rotating about an axis parallel to the adjustment direction X during the movement of the calibration assembly 2 and the focusing assembly 5. The rotation of the lens, in particular the calibration lens 3, can actually lead to a shift of the focus F of the laser beam L and a change in the size and / or shape of this focus F on the workpiece 100.

[0036] The laser cutting head 1 also includes: a wavefront sensor 9 of a known type and not described in further detail, such as a Shack-Hartmann wavefront sensor; and an electronic processor 12, which is connected to both the wavefront sensor 9 and the support and movement device 7, in particular, the electronic processor 12 is connected to the linear guide device 71.

[0037] In the embodiment shown, the wavefront sensor 9 positioned outside the housing device 15 is suitable for: receiving a focused first part L1 of the laser beam L, which first part L1 passes through a transparent optical element 11 that closes the side opening 53 of the housing device 15; performing phase measurement on the wavefront of the focused first part L1, in particular, the focused first part L1 is calibrated by a corresponding calibration optical system 19 with reference to the propagation direction P1 of the focused first part L1, and the calibration optical system 19 is positioned upstream of the wavefront sensor 9; and then obtaining a reconstructed wavefront based on the phase measurement and sending the reconstructed wavefront to the electronic processor 12.

[0038] The electronic processor 12 is then configured to compare the reconstructed wavefront obtained by the wavefront sensor 9 with a reference wavefront and thereby determine one or more optical aberrations to which the focused first portion L1 of the laser beam L is subjected based on this comparison.

[0039] It should be noted that, with respect to the focused second portion L2 of the laser beam L that impinges on and processes the workpiece 100, the focused first portion L1 is subject to further optical aberrations due to the transparent optical element 11 that closes the side opening 53 and through which it passes to reach the wavefront sensor 9. In order to improve the accuracy of the system, the further optical aberrations are advantageously known to the electronic processor 12, for example by an initial or periodic calibration of the laser cutting head 1.

[0040] The reference wavefront to which the reconstructed wavefront is compared can be an ideal wavefront without optical aberrations, for example when high-precision processing of the workpiece 100 is required, or the reference wavefront can be a predetermined wavefront affected by predetermined optical aberrations, for example when the processing of the workpiece 100 must meet less stringent precision requirements.

[0041] The electronic processor 12 can then cause the supporting and moving means 7 to operate so as to move the calibration assembly 2 and / or the focusing assembly 5, in particular Figure 1 In the embodiment shown in FIG, only the focusing assembly is moved along the adjustment direction X so that the optical aberrations of the laser beam L are reduced and the focus F is changed, in particular taking into account that only the focused first portion L1 is subjected to further aberrations so that the optical aberrations of the focused second portion L2 are reduced and the focus F is changed.

[0042] In more detail and with reference to what has already been emphasized, in the case of high-precision processing, that is, in the case of an ideal reference wavefront without optical aberrations, the electronic processor 12 is configured to operate the supporting and moving device 7 so that the optical aberrations of the laser beam L are minimized, and in particular, the optical aberrations of the laser beam L are returned to zero, and the focus F is changed accordingly; and in the case of processing with less stringent precision requirements, that is, in the case of a predetermined reference wavefront affected by a predetermined optical aberration, the electronic processor 12 is configured to operate the supporting and moving device 7 so that the optical aberrations of the laser beam L are less than or equal to the predetermined optical aberration, thereby changing the focus F accordingly.

[0043] Advantageously, the electronic processor 12 can control an alarm device of known type (not shown in the figures), such as a visual and / or audible alarm device. When the electronic processor 12 detects that the optical aberrations experienced by the laser beam L exceed a predetermined threshold value, such as a threshold value pre-set by the user, the electronic processor 12 sends an activation signal to the alarm device, which generates a visual or audible error signal. Thus, when the aberrations exceed the threshold value and are therefore harmful to the workpiece 100 because the laser beam L is not focused at the correct focal point F, the user can stop processing the workpiece 100 before the workpiece 100 is irreversibly damaged by the laser beam L.

[0044] When the laser cutting head 1 is associated with a machine tool and put into use, the laser cutting head 1 can perform the method according to the present invention for controlling laser cutting of a workpiece 100. The method comprises the following steps:

[0045] - laser cutting of the workpiece 100 by means of a laser cutting head 1 associated with a machine tool;

[0046] - Powering the laser cutting head 1 with a laser beam L from a laser emitting device;

[0047] - The laser beam L is collimated by means of the collimating assembly 2 and is focused by means of the focusing assembly 5

[0048] The laser beam L is focused into the focal point F;

[0049] - reflecting at least a first focused portion L1 of the focused laser beam L exiting from the focusing assembly 5 by the optical element 8;

[0050] - performing phase measurement of the wavefront of the focused first portion L1 by means of a wavefront sensor 9;

[0051] - obtaining a reconstructed wavefront based on phase measurements by the same wavefront sensor 9;

[0052] - comparing the reconstructed wavefront with a reference wavefront by means of the electronic processor 12;

[0053] - by means of the same electronic processor 12 and based on said comparison, a

[0054] or more optical aberrations to determine;

[0055] - reducing the optical aberrations to which the laser beam L is subjected in order to change the focus F, in particular again by means of the electronic processor 12;

[0056] According to what has been seen so far, if high-precision processing is required, i.e. the reference wavefront is an ideal wavefront without optical aberrations, the reduction step comprises minimizing one or more of the aforementioned optical aberrations, in particular zeroing them. Alternatively, if processing with less stringent precision requirements is required and the reference wavefront is therefore a predetermined wavefront affected by predetermined optical aberrations, the method according to the invention comprises the step of reducing the optical aberrations such that they are less than or equal to the predetermined optical aberrations.

[0057] Advantageously, the method according to the invention comprises the step of emitting an error signal by means of an alarm device controlled by the electronic processor 12 when the optical aberration exceeds a predetermined threshold value set in advance by the user.

[0058] Likewise advantageously, the method according to the invention may further comprise the step of calibrating the laser cutting head 1 once, for example when the machine tool is started up, or periodically during the processing of the workpiece 100. Thus, in particular, further optical aberrations to which the focused first portion L1 is subjected, introduced by the transparent optical element 11, can be detected.

[0059] Therefore, the laser cutting head 1 of the present invention can ensure cutting accuracy and repeatability even under extremely high laser power and under intensive and long-term use of the machine tool on which the laser cutting head 1 is installed.

[0060] Since the wavefront sensor 9 is connected to the electronic processor 12, it is actually possible to measure a variety of optical aberrations, including, for example, a shift in focus due to "thermal focus shift", spherical aberration, coma, and astigmatism, which affect the laser beam L leaving the cutting head, especially when the machine tool is used for a long time and with extremely high laser power, thereby causing an increase in the temperature of all optical components and a change in both the refractive index and the shape of the lens, thereby causing a shift in the focus F. Based on the measurement of the wavefront, the electronic processor 12 can change the structure of the optical system, in particular by operating the device 7 for supporting and moving the calibration optical assembly 2 and / or the focusing optical assembly 5, so as to easily and effectively reduce the optical aberrations to which the laser beam L is subjected and thus change the focus F so that the focus F is positioned and centered at a desired point, which is located on the surface 101 of the workpiece 100, or just below or just above the surface 101.

[0061] In the first embodiment of the laser cutting head 1 according to the present invention Figure 2 In the variant shown, the output opening 52 positioned at the cutting nozzle 30 is closed in a gas-tight manner by an optical element 38 capable of: receiving the focused laser beam L exiting the focusing assembly 5; reflecting a focused first portion L1 of the received laser beam L at a reflection angle, for example, between about 10° and about 100°; and transmitting a focused second portion L2 of the same received laser beam L to a focal point F. The optical element 38 is, for example, a beam splitter, in particular selected from a cubic beam splitter (CBS), an optical prism and a semi-transparent mirror.

[0062] The optical element 38 is positioned as a partitioning glass that separates the interior space 20 of the laser cutting head 1 from the external environment. Consequently, the laser cutting head 1 requires fewer optical components and has a compact form, particularly limited dimensions and reduced weight, making it suitable, in particular, for use in conjunction with machine tools with stringent dimensional and handling requirements. This variant is also economical and easy to manufacture.

[0063] Figure 3 A second embodiment of a laser cutting head 1 according to the invention is shown, which is also associated with a cutting and / or punching machine for cutting and / or punching, respectively, a machine part 100 , for example sheet metal.

[0064] In this second embodiment, the laser cutting head 1 includes components similar to those described above and designated by the same reference numerals, namely: a calibration assembly 2 for calibrating a laser beam L from a laser emitting device; a focusing assembly 5 for focusing the collimated laser beam L exiting the calibration assembly 2 onto a focal point F; at least one optical element 8 for receiving the focused laser beam L exiting the focusing assembly 5 and reflecting a focused first portion L1; and an electronic processor 12. The calibration assembly 2, the focusing assembly 5, and the optical element 8 are housed in an interior space 20 of a housing device 15. In particular, a fixing device 70 supports the calibration assembly 2 and the focusing assembly 5 and maintains the calibration assembly 2 and the focusing assembly 5 in a fixed position relative to the housing device 15.

[0065] In a variant not shown, the optical element that receives the focused laser beam L, reflects the focused first part L1 and transmits the focused second part L2, and also serves as a partition glass intended to separate the internal space 20 of the laser cutting head 1 from the external environment, which optical element has the above-mentioned advantages of the compact shape of the laser cutting head 1, in particular the limited dimensions, reduced weight and low cost.

[0066] The laser cutting head 1 in this second embodiment comprises at least one adaptive optical device 10 having an adjustable shape.

[0067] As is known, the adaptive optical device 10 comprises an adaptive optical element 16 having a thickness that allows for its deformability, and a suitable support comprising a piezoelectric actuator, an electromagnetic actuator, or an electromechanical actuator (not visible in the figure), which connects the adaptive optical element 16 to an electronic processor 12 in order to shape at least one deformable surface 17 of the adaptive optical element 16. Thus, the electronic processor 12 is able to adjust the shape of the adaptive optical device 10 by controlling the piezoelectric actuator or the electromagnetic actuator supporting the adaptive optical element 16.

[0068] With reference to the propagation direction P of the laser beam L from the calibration assembly 2 to the focusing assembly 5, the adaptive optical device 10 is positioned upstream of the focusing assembly 5, preferably downstream of the calibration assembly 2. Figure 3The laser beam L generated by the transmitting device and transmitted to the laser cutting head by the optical transmission device 4 leaves the calibration component 2 after calibration, hits the variable surface 17 of the adaptive optical element 16, and the laser beam L is reflected by the adaptive optical element 16 along the propagation direction P toward the focusing component 5.

[0069] The laser cutting head 1 according to this second embodiment also includes at least one wavefront sensor 9, which is suitable for: receiving the focused first part L1 of the laser beam L; performing phase measurement on the wavefront of the focused first part L1; obtaining a reconstructed wavefront based on the phase measurement; and sending the reconstructed wavefront to the electronic processor 12.

[0070] The electronic processor 12 is configured to: compare the reconstructed wavefront with a reference wavefront; determine one or more optical aberrations experienced by the laser beam L based on this comparison, thereby excluding additional optical aberrations experienced by only the focused first portion L1; and control the piezoelectric actuator or electromagnetic brake to adjust the shape of the adaptive optical device 10, reduce the above-mentioned optical aberrations and change the focus F.

[0071] Similar to what has already been seen, in the case of high-precision processing, the reference wavefront is an ideal wavefront without optical aberrations, and the electronic processor 12 is configured to adjust the shape of the adaptive optical device 10 so that the optical aberrations of the laser beam L are minimized and, in particular, zeroed, and thereby change the focus F. In the case of processing with less stringent precision requirements, the reference wavefront is a predetermined wavefront influenced by a predetermined optical wavefront, and the electronic processor 12 is configured to adjust the shape of the adaptive optical device 10 so that the optical aberrations of the laser beam L are less than or equal to these predetermined optical aberrations, and change the focus F.

[0072] In a different embodiment not shown, the laser cutting head 1 according to the present invention may include both a supporting and moving device 7 and an adaptive optical device 10, the supporting and moving device 7 supporting at least one of the calibration assembly 2 and the focusing assembly 5 and moving at least one of the calibration assembly 2 and the focusing assembly 5 along the adjustment direction X, these components being accommodated in the internal space 20. In this case, the actuator of the adaptive optical device 10 and the supporting and moving device 7 are connected to the electronic processor 12. In order to reduce the optical aberrations of the laser beam L and change the focus F, the electronic processor is able to operate the supporting and moving device 7 of the optical group and control the piezoelectric actuator or electromagnetic brake of the adaptive optical device 10 simultaneously or alternately.

[0073] Alternatively to that shown in the figure, the wavefront sensor 9 can be positioned at the side opening 53 of the housing device 15 and the side opening 53 of the housing device 15 is sealed in an airtight manner, or the wavefront sensor 9 is positioned inside the internal space 20 of the laser cutting head 1, in which second case the side opening 53 and the transparent optical element 11 that seals the side opening in an airtight manner are not necessary.

[0074] The laser cutting head 1 according to any of the further described embodiments and variants or possible combinations thereof, when associated with a machine tool and put into use, can implement the steps of the method of the invention for controlling laser cutting of a workpiece 100 according to what has been described.

[0075] Advantageously, the laser cutting head 1 of the present invention may further include: a cooling unit fixed to the exterior of the corresponding wall of the housing device 15; and a heat conducting device connecting the supporting and moving device 7 or the fixing device 70 to the wall of the housing device 15, so as to extract the heat generated in the focusing optical component 5 by heat conduction from the supporting and moving device 7 or the fixing device 70, the collimating optical component 2, and the focusing optical component 5 when the supporting and moving device 7 or the fixing device 70, the collimating optical component 2, and the focusing optical component 5 pass through the laser beam L. To this end, at least the corresponding wall of the housing device 15, the supporting and moving device 7, and the fixing device 70 are made of a material having high thermal conductivity.

[0076] In a version of the laser cutting head 1 of the invention that is not shown in the figures, the calibration lens 3 and the focusing lens 6 are cooled by a cooling system of known type, which consists in introducing a gas at a controlled temperature (usually nitrogen) into the interior of the laser cutting head 1 so as to come into contact with the lenses and thereby cool them.

Claims

1. A laser cutting head (1), capable of being associated with a machine tool, comprising: - a calibration component (2), said calibration component (2) being used to calibrate the laser beam (L) from the laser emitting device; - a focusing assembly (5) for focusing the collimated laser beam (L) exiting from the collimating assembly (2) at a focal point (F); - a supporting and moving device (7), the supporting and moving device (7) being used to support at least one of the calibration component (2) and the focusing component (5), and to move at least one of the calibration component (2) and the focusing component (5) along an adjustment direction (X); at least one optical element (8; 38) for receiving the focused laser beam (L) exiting from the focusing assembly (5), and reflecting the focused first portion (L1) of the received laser beam (L); an electronic processor (12) adapted to operate the supporting and moving device (7) to move at least one of the calibration assembly (2) and the focusing assembly (5) along the adjustment direction (X); - housing means (15), said housing means (15) forming an inner space (20), said inner space (20) being suitable for accommodating at least said calibration assembly (2), said focusing assembly (5), said supporting and moving means (7) and said at least one optical element (8), The laser cutting head (1) is characterized in that the laser cutting head (1) comprises at least one wavefront sensor (9), wherein the at least one wavefront sensor (9) is adapted to: receiving the focused first portion (L1) of the laser beam (L); performing a phase measurement on the wavefront of the focused first portion (L1); obtaining a reconstructed wavefront based on the phase measurement; and sending the reconstructed wavefront to the electronic processor (12), the electronic processor being configured to: compare the reconstructed wavefront with a reference wavefront; determine one or more optical aberrations to which the laser beam (L) is subjected based on the comparison; and operate the supporting and moving device (7) to reduce the one or more optical aberrations and change the focus (F), The housing device (15) is provided with a lateral opening (53), the lateral opening (53) being sealed in an airtight manner by a transparent optical element (11), the transparent optical element (11) being used to transmit the focused first part (L1) of the laser beam (L) toward the external environment, the wavefront sensor (9) being located outside the housing device (5).

2. The laser cutting head (1) according to claim 1, wherein: The reference wavefront is an ideal wavefront without optical aberrations, and the electronic processor (12) is configured to operate the supporting and moving device (7) so that: the one or more optical aberrations are minimized, or the one or more optical aberrations are reset to zero; or, the reference wavefront is a predetermined wavefront affected by predetermined optical aberrations, and the electronic processor (12) is configured to operate the supporting and moving device (7) so that: the one or more optical aberrations are less than or equal to the predetermined optical aberrations.

3. A laser cutting head (1), capable of being associated with a machine tool, comprising: - a calibration component (2), said calibration component (2) being used to calibrate the laser beam (L) from the laser emitting device; - a focusing assembly (5) for focusing the collimated laser beam (L) exiting from the collimating assembly (2) at a focal point (F); - at least one adaptive optical device (10), said adaptive optical device (10) having an adjustable shape; at least one optical element (8; 38) receiving the focused laser beam (L) exiting from the focusing assembly (5) and reflecting a focused first portion (L1) of the received laser beam (L); - an electronic processor (12) adapted to adjust the shape of the adaptive optical device (10); The laser cutting head (1) is characterized in that the laser cutting head (1) includes at least one wavefront sensor (9), which is suitable for: receiving the focused first part (L1) of the laser beam (L); performing phase measurement on the wavefront of the focused first part (L1); obtaining a reconstructed wavefront based on the phase measurement; and sending the reconstructed wavefront to the electronic processor (12), which is configured to: compare the reconstructed wavefront with a reference wavefront; determine one or more optical aberrations experienced by the laser beam (L) based on the comparison; and adjust the shape of the adaptive optical device (10) so that the one or more optical aberrations are reduced and the focus (F) is changed.

4. The laser cutting head (1) according to claim 3, wherein: The reference wavefront is an ideal wavefront without optical aberrations, and the electronic processor (12) is configured to adjust the shape of the adaptive optical device (10) so that: the one or more optical aberrations are minimized, or the one or more optical aberrations are reset to zero; or, the reference wavefront is a predetermined wavefront affected by predetermined optical aberrations, and the electronic processor (12) is configured to adjust the shape of the adaptive optical device (10) so that: the one or more optical aberrations are less than or equal to the predetermined optical aberrations.

5. The laser cutting head (1) according to claim 3 or 4, wherein: The adaptive optical device (10) is positioned upstream of the focusing assembly (5) with respect to the propagation direction (P) of the laser beam (L).

6. The laser cutting head (1) according to claim 1 or 3, wherein: The at least one wavefront sensor (9) is a wavefront sensor of the Shack-Hartmann type.

7. The laser cutting head (1) according to claim 1 or 3, wherein: The at least one optical element (8; 38) is a beam splitter.

8. The laser cutting head (1) according to claim 1 or 3, wherein: The at least one optical element (8; 38) is selected from a cube beam splitter, an optical prism and a semi-transparent mirror.

9. The laser cutting head (1) according to claim 1, wherein: The optical element (38) is suitable for separating the inner space (20) of the laser cutting head (1) from the external environment.

10. The laser cutting head (1) according to claim 1 or 3, wherein: The laser emitting device is a fiber laser.

11. A method for controlling laser cutting of a workpiece (100), the method comprising the following steps: - laser cutting the workpiece (100) by means of a laser cutting head (1) according to claim 1 associated with a machine tool; - energizing the laser cutting head (1) with a laser beam (L); - collimating the laser beam (L) and focusing the laser beam (L) into a focal point (F); - reflecting at least one focused first portion (L1) of the focused laser beam (L); - performing a phase measurement of the wavefront of the at least one focused first portion (L1) by means of the at least one wavefront sensor (9) located outside the housing means (5); - obtaining a reconstructed wavefront based on said phase measurement; - comparing the reconstructed wavefront with a reference wavefront; - determining one or more optical aberrations to which said laser beam (L) is subjected based on said comparison; - operating the supporting and moving means (7) so as to reduce the one or more optical aberrations to which the laser beam (L) is subjected, in order to change the focus (F) of the laser beam (L).

12. A method for controlling laser cutting of a workpiece (100), the method comprising the following steps: - laser cutting the workpiece (100) by means of a laser cutting head (1) according to claim 3 associated with a machine tool; - energizing the laser cutting head (1) with a laser beam (L); - collimating the laser beam (L) and focusing the laser beam (L) into a focal point (F); - reflecting said at least one focused first portion (L1) of said focused laser beam (L); - performing a phase measurement on the wavefront of the at least one focused first portion (L1); - obtaining a reconstructed wavefront based on said phase measurement; - comparing the reconstructed wavefront with a reference wavefront; - determining one or more optical aberrations to which said laser beam (L) is subjected based on said comparison; - adjusting the shape of the adaptive optical device (10) to reduce the one or more optical aberrations to which the laser beam (L) is subjected, so as to change the focus (F) of the laser beam (L).

13. The method according to claim 11 or 12, wherein: The reference wavefront is an ideal wavefront without optical aberrations, and the reduction includes: minimizing the one or more optical aberrations, or returning the one or more optical aberrations to zero; or, the reference wavefront is a target wavefront affected by predetermined optical aberrations, and the method includes the following steps: reducing the optical aberrations so that: the optical aberrations are less than or equal to the predetermined optical aberrations.

14. The method according to claim 11 or 12, wherein: The steps of performing phase measurement and obtaining the reconstructed wavefront are performed by a wavefront sensor (9).

15. The method according to claim 11 or 12, further comprising the steps of: When the optical aberration exceeds a preset threshold, an error signal is sent.

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