Laser processing system and laser processing method for components

Abstract

A system (1) for laser processing of a component, in particular for laser cutting of a component, comprising: a source (L) for emitting a pulsed laser beam; a first subsystem (LDO); at least first and second deflectors, with non-parallel axes; a second subsystem (LQO) adjusting the polarization of the beam exiting the deflectors; a deflector control subsystem; a synchronization subsystem (DG); a first focusing subsystem (F), comprising a first lens FT and located after the second subsystem (LQO), adjusting the polarization of the beam exiting the deflectors; a subsystem simultaneously controlling the divergence and the deflection of the laser beam at the output of the deflectors, comprising (i) a second focusing subsystem (RF), and (ii) a propagation module (SPF), the subsystem simultaneously controlling the divergence and the deflection being located between the output of the deflectors and the first focusing subsystem (FT); and a beam stabilization subsystem (MS).

Description

Technical Field

[0001] This invention relates to laser processing systems for components, particularly outside the field of watchmaking. The invention also relates to a laser processing method. Background Technology

[0002] Laser processing is used in microtechnology to manufacture parts. In particular, femtosecond lasers can precisely process small parts at very high speeds without thermal damage. However, traditional methods of focusing and guiding the laser beam make it difficult to produce parts with straight sides along the cutting line. The conical shape of the laser beam at the focal point, the non-uniform intensity distribution of the laser beam, and the nonlinear tendency of the ablation depth according to the light intensity result in a side tilt of several degrees.

[0003] To address this issue, a recognized approach involves manipulating the workpiece and / or laser processing head using a five-axis mechanical system. This technique allows the workpiece and / or laser head to tilt to compensate for the taper at the focal point on the remaining side of the workpiece.

[0004] Another widely used method is through spiral laser processing, which uses a laser beam that is tilted and rotated about an axis via an optomechanical device. The focusing of this rotating beam produces a specific focal point. The laser beam is slightly tilted in the opposite direction relative to the processing plane to compensate for the taper, and its focal point describes a circular trajectory. This circle forms the base of a cone, the apex of which lies above the processing plane. Therefore, the length of the processing path increases, and the volume of material removed also increases.

[0005] In both of the aforementioned cases, the machining feed rate is significantly reduced. In the first method, this reduction in feed rate is due to the limited travel speed of the table or machining head. In the second method, the beam requires additional time to complete its path around the circumference of the circle. Furthermore, the stability of optomechanical systems containing optical elements rotating at high speeds (up to 30,000 revolutions per minute or 500 Hz) is prone to rapid degradation and is often accompanied by harmful vibrations.

[0006] In conventional femtosecond laser processing, femtosecond lasers remove material through ablation while minimizing thermal load. To achieve this, the energy delivered with each pulse is kept just above the ablation threshold. The beam is focused on the workpiece to create a circular focal spot. This requires overlap between successive pulses to ensure uniform material removal. Given a shallow ablation depth, multiple passes along the cutting contour are necessary.

[0007] The overlap between consecutive pulses is typically 50%–75%. The feed rate for a focal spot with this overlap is...

[0008] vmax = flaser × dfocal × (1 − arec), where

[0009] -flaser is the laser pulse frequency.

[0010] -dfocal is the focal spot diameter.

[0011] -arec represents the degree of overlap between consecutive pulses.

[0012] Typically, arec=0.75, dfocal=10μm, and flasher=1~10 MHz, which produces a vmax value between 2.5 m / s and 25 m / s. The latter corresponds to the maximum velocity of the galvanometer system.

[0013] In the case of laser processing using a precessing beam, such as Figure 1 As shown, the laser beam is tilted at an angle α relative to the normal N of the workpiece S to be processed. To achieve the desired taper on both sides regardless of the processing direction, the tilted beam rotates around the precession axis AP. The BFI (Best Focus Individual) plane is defined as the instantaneous focal plane of the laser beam. The laser trace in this BFI plane has a circular shape. The beam itself describes a cone in space around the AP axis, and its apex must be located above the BFI plane to achieve the desired taper on the sides.

[0014] For rotary machining, the overlap principle between continuous pulses is transformed into the overlap between two continuous rotary circles. The rotary frequency fprec limits the maximum feed rate according to the following formula:

[0015] vmax=fprec×dfocal×(1-arec).

[0016] At fprec = 500 Hz (30,000 rpm), existing rotating optical systems are typical.

[0017] arec=0.75,

[0018] dfocal=10μm,

[0019] We obtain vmax = 0.00125 m / s = 1.25 mm / s. This feed rate is much lower than the maximum speed of the galvanometer system estimated above.

[0020] When the diameter of the opening on the side where the laser beam enters the workpiece is greater than the diameter of the opening on the output side, this is called positive taper. When both diameters are the same, the taper is considered zero, resulting in a straight-line shape on the machined side: the machining geometry is a small cylinder in static drilling mode. Conversely, if the diameter of the opening on the input side is smaller than the diameter of the beam's output, the taper becomes negative.

[0021] A rotary focusless system for precession laser processing is known from document WO 2016 / 024069 A1. The laser beam is displaced parallel to its initial axis by an arrangement of two rotating off-axis lenses. This displacement is achieved by the focusing lens at an angle that can compensate for the taper of the side of the hole or cutting path.

[0022] Document EP3700705A1 discloses a method for scanning a laser beam up to 5 or 6 axes (5D or 6D) using path interpolation between reference points. The 5-axis or 6-axis includes:

[0023] - The 3-position coordinate axis (x, y, z) of the focus.

[0024] - The tilt angles α and β of the laser beam relative to the path, and

[0025] - The angle of linear polarization of the laser beam.

[0026] Two 4D (x, y, α, β) control subsystems for the laser beam, based on four single-axis galvanometer mirrors or two bi-axis galvanometer mirrors, are mentioned as examples. Control on the z-axis is provided by a focusing lens or by a workpiece holder.

[0027] Document EP3195041A1 discloses a system for transforming a laser beam using a tilting mirror that rotates about its axis of symmetry. To compensate for angular deviations in the beam, a back reflector reflects it back onto a mirror, which, through a second reflection, returns the beam to a path parallel to and deviating from the initial beam. As a result, the laser beam traces a circle centered on the axis. This circular motion is then converted into a precessing motion by a focusing lens, which can compensate for the taper of the sides of a hole or cutting path.

[0028] A rotary optomechanical precession system for performing laser processing with adjustable lateral taper is known from document WO2012035031A1. The element for adjusting the circular deflection of the laser beam is an inclined plate with parallel surfaces.

[0029] Document US20160250714A1 discloses a laser processing system, including:

[0030] 1) A first positioning system for applying a first relative motion of the laser beam axis relative to the workpiece along the beam path;

[0031] 2) A processor for determining a second relative motion of the laser beam axis, the second relative motion having a reduced amplitude (jitter) compared to the first motion;

[0032] 3) A second positioning system for applying the second relative motion; and

[0033] 4) A laser source used to emit laser beam pulses.

[0034] The first system is a galvanometer deflector, and the second system is an acousto-optic deflector (AOD). This application aims to protect the high-speed processing of conductive tracks with variable cross-sections and variable geometries for use in semiconductor chip packaging (semiconductor packaging).

[0035] Intermediate lenses are used to guide the laser beam after the second system (AOD) toward the first galvanometer system. These lenses may introduce aberrations and prevent proper focusing of the laser beam. Therefore, processing time may increase or processing accuracy may decrease.

[0036] Methods for manufacturing gemstone watches with and without holes are described in documents EP3770697A1, EP4004654A1, CH 716430 A2, EP3770698A1, EP4004653A1, and CH716431A2, respectively. These methods include an ultrashort pulse laser ablation step with a duration of less than 100 ps. A 3-axis spiral advance system is used to scan the laser beam to eliminate and / or control the taper of the machined sides. Summary of the Invention

[0037] The object of this invention is to provide a laser processing system that overcomes current limitations associated with the use of moving optics, particularly in terms of the speed of laser processing via precession (limited by the precession speed and its circular trajectory) and in terms of controlling taper and roughness. Trajectories of closed shapes (such as circles, ellipses, or polygons) or open shapes (such as spirals) can be achieved at high speed. The invention also aims to overcome some limitations on the power transmitted to the workpiece caused by optics containing multiple refractive elements. Furthermore, the invention enables flexible laser processing, allowing for near-instantaneous switching between precession processing modes and conventional processing without precession.

[0038] The laser processing system according to the present invention is defined by claim 1.

[0039] Various embodiments of the laser processing system according to the present invention are defined by claims 2 to 12.

[0040] The laser processing method according to the present invention is defined by claim 13.

[0041] The embodiments of the method according to the invention are defined by claims 14 and 15. Attached Figure Description

[0042] The accompanying drawings illustrate, by way of example, an embodiment of the laser processing system according to the present invention.

[0043] Figure 1This is a schematic diagram illustrating the principle of laser processing with rotation.

[0044] Figure 2 This is a schematic diagram illustrating the operating principle of the acousto-optic deflector.

[0045] Figure 3 This is a block diagram of an embodiment of the laser processing system according to the present invention.

[0046] Figure 4 This is a schematic diagram of an embodiment of the laser processing system according to the present invention.

[0047] Figure 5 It is a diagram showing the envelope shape of a laser beam that spins in without a divergence control system.

[0048] Figure 6 It is a diagram showing the envelope shape of a precessing laser beam that implements a divergence control system.

[0049] Figure 7 This is a table summarizing the parameters for implementing the processing method according to the present invention. Detailed Implementation

[0050] The following is for reference. Figures 3 to 7 The implementation scheme of System 1 is described. In particular, the laser processing system can be a laser cutting or laser engraving system.

[0051] System 1 includes:

[0052] -Laser source L used to emit pulsed laser beams,

[0053] - The first subsystem used to adjust the polarization of the laser beam, the LDO, especially the half-wave plate LDO,

[0054] -At least the first and second deflectors, particularly the first and second acousto-optic deflectors (AOD) or the first and second electro-optic deflectors, have non-parallel axes, particularly vertical axes.

[0055] - The second subsystem, LQO, is used to adjust the polarization of the beam emitted from the deflector. In particular, one or two quarter-wave plate LQOs are used to convert the linear polarization of the laser beam into circular polarization.

[0056] - The deflector control subsystem, particularly the controllable radio frequency generator (GRP), which can be implemented by a digital frequency synthesizer or a voltage-controlled oscillator, controls the energy and emission of the laser pulse by controlling the deflector. Specifically, it controls the acoustic excitation of the acousto-optic deflector or the refractive index of the electro-optic deflector to adjust the intensity of the laser beam at the output of the deflector.

[0057] - An adjustable delay generation subsystem (DG) that enables the laser beam resonator (GRP) to be synchronized with the laser clock to control the deflection of the anode (AOD) between two consecutive laser pulses, or a synchronization subsystem (DG) used to synchronize the laser beam emission source with the control subsystem (GRP).

[0058] - The first focusing subsystem F, including the first lens FT and located after the second subsystem LQO, is used to adjust the polarization of the beam exiting the deflector.

[0059] - A subsystem for simultaneously controlling the divergence and linear deflection of the laser beam at the output of the deflector, and

[0060] - A beam stabilization subsystem MS located downstream of the laser source and / or upstream of the first deflector.

[0061] Preferably, the system is configured to generate a precession of the laser beam.

[0062] In addition, the subsystems for simultaneously controlling the divergence and linear deflection of the laser beam include:

[0063] -Second focusing subsystem RF, such as the first telescope RF, and

[0064] - A necessary length of propagation module SPF to achieve:

[0065] (a) The distance from the first lens FT to the beam focal point (the distance between the BFI plane and the upstream reference point O of the BFI plane) is greater than the distance from the first lens FT to the apex of the precession cone (the distance between the BFG plane and the upstream reference point O of the BFG plane), and

[0066] (b) Predefined precession ring diameter. Furthermore, a subsystem for simultaneously controlling divergence and linear deflection is located between the deflector output and the first focusing subsystem FT.

[0067] In embodiments of the laser processing system shown and described in more detail, the deflector is an acousto-optic deflector (hereinafter referred to as an AOD deflector or AOD).

[0068] In this embodiment, an acousto-optic deflector is used to generate the precessing beam, as described in the following reference. Figure 2 As described. Powered by radio frequency generator G RF The driven piezoelectric element PZ excites the acoustic wave OA in crystal C, generating an in-phase waveguide whose propagation speed is the same as the speed of sound propagation in the material. Due to the acousto-optic effect, the refractive index of the material is periodically modulated by the compression and expansion regions generated by the acoustic wave. The incident laser beam B1 is diffracted by this moving grating. The diffracted beam B2 has a diffraction angle θ relative to the direction of the incident beam B1. The angle θ is approximated by the following relationship:

[0069] θ = (λ × f)RF ) / V,

[0070] in:

[0071] λ is the wavelength of the laser beam.

[0072] f RF It is the frequency of the sound wave, and

[0073] V is the velocity of these waves.

[0074] Therefore, the diffraction angle can be modified by changing the acoustic frequency. However, the maximum angle amplitude is not high, typically on the order of 1°.

[0075] Preferably, the undiffracted beam B1 is typically not used and is blocked by absorber A. Typically, up to 90% of the energy of the incident beam B1 can be converted into beam B2.

[0076] Advantageously, AOD also includes an acoustic absorber (AAC).

[0077] Advantageously, AODs are combined in pairs, with their deflection directions orthogonal to each other. This allows the beam to be guided in two dimensions, and in particular, to precess to form a precessing beam.

[0078] When the deflector is of the AOD type, the amplitude and frequency of the acoustic wave are adjusted according to the desired diffraction angle and laser beam intensity.

[0079] When the deflector is of the EOD type, the amplitude of the deflector drive voltage varies depending on the desired angle of refraction.

[0080] To achieve the fastest possible laser processing using femtosecond pulses, where the laser is driven by a precession motion, it is necessary to ensure sufficient overlap between the precession circles. These circles are generated by the action of an acousto-optic deflector, and the laser processing system also includes a galvanometer system SG (scanner head) that provides the processing feed movement. Therefore, the SG galvanometer system ensures a large achievable working area for this processing. This principle requires maximizing the precession speed to fully utilize the maximum scanning speed of the galvanometer system.

[0081] The use of acousto-optic deflectors (AODs) typically increases addressing speed in the working plane, thereby increasing the precession frequency, especially since their response time is approximately 1 μs (the duration corresponds to the propagation of sound along the beam diameter), rather than the millisecond range achievable by mechanical rotating systems. However, specific measures are advantageously employed to improve the utilization of AODs:

[0082] a) The nonlinear effects caused by high-intensity laser pulses are reduced.

[0083] b) Compensation depends on the variability of the intensity of the diffracted light due to the diffraction angle and polarization.

[0084] c) Since the diffraction angle is limited to approximately 1°, a system is realized that can convert the angular deflection of the laser beam into a linear displacement in a plane perpendicular to the beam, preferably approximately 10 mm.

[0085] d) The incident beam is stabilized due to the small deflection angle and the limited aperture of the AOD, which is typically on the order of 5 mm.

[0086] e) Implement a control system PC to control the focus of the spiral beam in order to achieve the desired taper during laser processing.

[0087] In the variant, addressing along the contour (which can be closed or open) is followed by the machining system in a random or continuous manner to optimize side roughness and thermal load.

[0088] The use of AOD is limited by laser damage and laser repetition rate. The crystal in the AOD is made of quartz, a dielectric with a high damage threshold flux. For a single pulse of 515 nm and a pulse duration of 500 fs, the estimated damage threshold in silica is approximately 2.5 J / cm². -2 However, due to the incubation effect, this threshold drops to approximately 0.6 J / cm² after 100,000 pulses. -2 Since the AOD has a maximum aperture of 7 mm, the maximum energy per pulse is estimated to be 230 mJ. Therefore, the damage threshold is assumed to be approximately 0.6 J / cm². -2 If the pulses remain relatively stable for more than 100,000 pulses, the AOD can be safely used with current industrial lasers with a power of 300 W and a pulse frequency in the range of 0.1 MHz to 1 MHz.

[0089] The maximum usable laser repetition rate is limited by the velocity of sound in the AOD crystal and the beam size. For a beam diameter of 7 mm, based on the sound wave at approximately 5,700 ms... -1 The estimated maximum frequency is 814 kHz, which is the time required for the speed to traverse that distance.

[0090] The control subsystem includes a delay generator (DG) that synchronizes the excitation of acoustic waves in the AOD with the arrival of laser pulses to generate a diffraction grating, thereby optimizing the intensity of the diffracted light. This subsystem also adjusts the diffraction efficiency based on the acoustic intensity. This control allows the intensity of the laser beam to be homogenized along its annular path in a plane perpendicular to the system's optical axis, ensuring uniform ablation of the material throughout the processing, particularly when the laser beam follows a circular trajectory. In one embodiment, the control may be based on a lookup table that correlates diffraction angle values ​​with specific acoustic frequencies and intensities. In another embodiment, the intensity of the laser pulse at the source output can be adjusted according to the diffraction angle to ensure uniform beam intensity along the path downstream of the AOD.

[0091] To compensate for deviations, particularly those caused by thermal fluctuations in the beam at the output of the laser source L, the MS laser beam stabilization subsystem is advantageously integrated upstream of the AOD. Therefore, the laser beam stabilization subsystem MS can be located between the amplifier EF and the input of the first acousto-optic deflector (AOD). This subsystem also advantageously reduces pre-processing waiting time due to laser preheating after power-on.

[0092] After passing through the AOD, the laser beam, following a circular trajectory, is focused by the first focusing subsystem F, specifically by a telecentric F-θ lens, which has the advantage of maintaining the focal spot size and minimizing aberrations throughout the working field. Because the beam divergence is smaller than the deflection angle of the AOD in the circular trajectory mode, the beam is focused before the apex of the precession cone. Figure 5 and Figure 6 As shown, the BFG (Best Focus Global) plane is a plane perpendicular to the optical axis in which the minimum cross-sectional dimension of the virtual intersection of the precessing laser beams is formed, very close to the apex of the cone formed by the precessing laser beam. Essentially, material processing is performed outside the apex of the precessing cone (downstream of the BFG plane) to obtain a side profile with zero or negative taper. The BFI plane (for the "Best Focus Individual") is a plane perpendicular to the optical axis of the focused laser beam. If the beam is properly collimated, the BFI plane coincides with the focal plane of the lens.

[0093] like Figure 5 As shown, early focusing of the laser beam prevents optimized spiraling machining. The width of the cut groove is significantly wider than the BFG plane (compared to a beam without spiraling), which requires a more powerful pulse and compromises accuracy. This increases the risk of overheating the processed material and reducing side quality.

[0094] The difference Δ between the BFI and BFG planes is given by the following equation:

[0095] Δ=BFG-BFI=f / (r / (f×tanα)-1),

[0096] in

[0097] f is the focal length of the focusing subsystem F.

[0098] r is the radius of the beam circle at the entrance of the focusing subsystem F.

[0099] α is the angle between the laser beam and the precession axis (optical axis).

[0100] For typical values:

[0101] -100mm focal length,

[0102] The angle α between -0.1° and 1°, and

[0103] - The radius r is 10mm.

[0104] Obtain a value for ∆ between 1 mm and 20 mm. This is disadvantageous because the BFG plane is always downstream of the BFI plane.

[0105] To remedy this situation, the laser processing system advantageously includes a second focusing subsystem RF located downstream of the AOD, specifically a first slightly focused telescope. Beam divergence can be modified by slightly focusing the beam divergence and utilizing its divergent portion beyond the focal point by adjusting the distance between lenses L1 and L2 of the second focusing subsystem RF. Soft focusing is necessary to prevent optical breakdown at this intermediate focal point. This is characterized by a long effective focal length. Advantageously, this long distance is also used to increase the beam scanning radius of the AOD. Positioning the subsystem RF at the output of the AOD sets the deflection focus near the center of the positive lens, which remains constant or slightly modifies the deflection angle required for the advance. This is the opposite in terms of beam divergence, thus allowing precise adjustment of the distance between the BFI and BFG planes to form the optimal focus for advance processing with controlled taper.

[0106] exist Figure 5 and Figure 6 In the image, the beam divergence angle has been magnified for easier understanding.

[0107] The first focusing subsystem FT, which includes a telecentric F-θ lens in the scanner head, offers two main advantages for achieving straight sides in precession laser processing. The first advantage is that the average incident angle of each laser beam remains perpendicular to the surface of the workpiece at both the center and edges of the machined area. This prevents interference caused by cos(θ). 4 The law (which defines the attenuation of beam energy as a function of the beam incident angle θ) causes a loss of processing uniformity. A second advantage stemming from the first is the maintenance of a constant circular beam focusing shape even at processing depths. In the event of vertical displacement during processing, this ensures the stability of the incident angle, thereby ensuring the consistency of lateral tilt and the quality of their surfaces.

[0108] In contrast, a scanner head equipped with a standard F-θ lens during laser processing can cover a larger working area than a telecentric F-θ lens. However, the angle of incidence of the light changes: it is perpendicular to the working plane at the center but gradually slopes towards the edges. Therefore, a standard F-θ lens cannot maintain perpendicular incidence of the laser beam under lateral and vertical offsets, nor can it span the entire working surface. Furthermore, the shape of the focal point is distorted into an ellipse outside the center of the working plane, making it difficult (if not impossible) to achieve a side with a constant angle of incidence by using a non-telecentric laser beam. In practice, the angle of incidence becomes dependent on the location of the processing point on the working plane and the processing depth.

[0109] Figure 3 and Figure 4 A precession-based laser processing system with controlled taper is schematically illustrated according to one embodiment. The system includes a laser source L, which is excited by an acousto-optic deflector AOD synchronized with a delay generator DG. The beam emitted from the laser source is amplified by a telescope EF before entering a stabilization subsystem MS. After passing through the stabilization subsystem MS, the beam polarization is adjusted by a first laser beam polarization adjustment subsystem LDO to maximize the diffraction efficiency of the AOD. A second subsystem LQO converts the linear polarization of the beam after the AOD to circular polarization to adjust the polarization of the beam leaving the acousto-optic deflector. Next, the beam divergence is modified by a subsystem including a first telescope to simultaneously control the laser beam divergence and linear deflection. A beam propagation module SPF provides the necessary path length to adjust its divergence and also converts angular deflection into linear deflection before the beam enters a first focusing subsystem F. The first focusing subsystem F includes a galvanometer mirror SG and a first telecentric F-θ focusing lens FT.

[0110] The laser source L can be associated with a frequency multiplier. Therefore, the laser source L can deliver pulses with a repetition rate of 100 kHz to 1 MHz, a pulse energy of 1 μJ to 200 mJ, a wavelength of 300 nm to 2,000 nm, and a beam diameter of 1 to 10 mm, with a duration in the range of 10 fs to 10,000 fs.

[0111] The EF telescope preferably increases the beam diameter from 3 mm to 5 mm, thereby allowing for better utilization of the 7 mm total aperture of the AOD.

[0112] The subsystem for simultaneously controlling the divergence and linear deflection of the laser beam includes an RF telescope. The telescope comprises, for example, two lenses, L1 and L2, with focal lengths of 150 mm and -100 mm, respectively. They can be positioned approximately 40 mm apart on an electric axis, allowing this distance to be adjusted via a control subsystem PC.

[0113] The divergence obtained after passing through the RF telescope is 0.1 to 5 milliradians, typically 1 to 2 milliradians. At the entrance of the SG galvanometer system, the diameter of the non-precessing beam is 3 mm to 18 mm. The diameter of the precessing circle can be set from 0.1 mm to 20 mm. Therefore, the outer diameter of this circle at the entrance of the first F focusing subsystem is approximately 3 mm to 38 mm, typically 10 mm to 20 mm. The total beam propagation distance between the RF telescope output and the SG galvanometer system input is approximately 3 mm to 10 mm, typically 5 mm to 7 mm.

[0114] The first F focusing subsystem in Figure 4 As shown in the diagram. The first F-focusing subsystem may include:

[0115] - The scanner head SG includes two galvanometer mirrors, specifically capable of receiving beams up to 40 mm in diameter, typically 20 mm to 30 mm.

[0116] - Telecentric F-θ lens FT, especially with a focal length of 100 mm.

[0117] The beam scanning speed can reach 8 m / s -1 and 14 m / s -1 The distance between the BFG plane and the BFI plane can vary from 10 μm to 5000 μm, typically between 100 μm and 500 μm, depending on the beam divergence and AOD deflection value.

[0118] Examples of possible processing parameters are in Figure 7 The table provides the information.

[0119] According to the method of the present invention, or when using the machining system according to the present invention, various parameters control the machining taper and the surface roughness:

[0120] - Number of passes. With increasing passes, the taper becomes more negative until it reaches a limit dependent on the ablation threshold. The ablation threshold for a given material operated on by a laser pulse depends on the wavelength, pulse duration, pulse energy, and energy intensity (J / cm²) on the material surface. -2 The latter is determined by a focusing device, usually a lens.

[0121] - The ring diameter described by the laser beam deflected by the AOD. This diameter defines the angle of attack, or precession cone. The larger the diameter, the more negative the taper at a given focal length of the focusing lens.

[0122] - The number of laser pulses around the annular circumference, described by the laser beam deflected by AOD. This value ranges from 1 to 10,000, and is typically 1 to 1,000.

[0123] - The focal length of the F-θ lens and the diameter of the advance cone, given by the deflection of the AOD, define the angle of incidence of the material to be processed.

[0124] The roughness of the side surface depends on the number of passes and the type of beam path. It decreases with increasing number of passes and by machining homogenization to create beam paths with the most uniform focal overlap and no repeating patterns. To achieve this, the precession (rotation of the laser beam via the AOD) alternates between clockwise and counterclockwise directions. Non-sequential addressing (e.g., random addressing) of points on the circumference of the precession ring also reduces roughness.

[0125] Two different machining modes can be used to control the taper.

[0126] In the first mode, the deflection angle of the laser beam by the AOD is constant to form a ring with a constant final diameter. In this first mode, the cone does not change along the processing path of the part, and the control of the laser beam by the scanner head is not synchronized with the deflection angle of the AOD.

[0127] In the second mode, a taper value is assigned to each location along the machining contour of the part. The position of the scanner head, which tracks the contour of the part, is used to calculate the deflection required for AOD (Advanced Occurrence Displacement) to create the appropriate feed taper. Therefore, the scanner head is synchronized with the AOD. This synchronization is performed by the control subsystem PC.

[0128] In the context of this invention, tests show that with an F-θ lens at a focal length of 100 mm, the lateral taper range is ±5°. By changing the focal length to 50 mm, this range is extended to ±10°.

[0129] Materials suitable for laser processing by spin advance according to the present invention include:

[0130] -Metal,

[0131] - metal alloys,

[0132] -ceramics,

[0133] -Glass,

[0134] -polymers, and

[0135] - Combinations of these materials, especially in the form of composite materials.

[0136] These materials can be crystalline, particularly polycrystalline, or amorphous, particularly amorphous, natural, or synthetic. Examples of polycrystalline and crystalline materials include metallic alloys, semiconductors, ceramics, cermets, sapphire, and ruby. Examples of amorphous materials include mineral glasses and amorphous metallic alloys.

[0137] The wavelength of the laser source is selected based on the absorption of the material to be processed. Generally, metals can be processed well, with all practical wavelengths between 2 μm and 300 nm. Wavelengths from 300 nm to 600 nm are preferred for transparent or translucent materials and metals due to their higher processing precision.

[0138] Regardless of the implementation or variation, AOD can be made from crystalline silica SiO2. Alternatively, other acousto-optic materials can be used for AOD, such as:

[0139] -Tellium oxide TeO2,

[0140] - Potassium niobate (KNbO3)

[0141] -Lithium niobate (LiNbO3)

[0142] -Lithium tantalate LiTaO3, or

[0143] - Lead molybdate (PbMoO4).

[0144] Regardless of the implementation or variation, electro-optic deflectors (EODs) can be used as an alternative to AODs. Among these deflectors:

[0145] - Electro-optic effects, especially the Pockels effect or linear electro-optic effect (proportional to the electric field strength), and

[0146] - Kerr effect or second electro-optic effect

[0147] It can also be used to construct electro-optic deflectors. The advantage of this EOD is the absence of undeflected beams, which eliminates the need for cooling absorbers to absorb undeflected beams. This allows for the creation of more compact deflectors that do not require water cooling.

[0148] There are two main configurations for constructing electro-optic deflectors. The first configuration utilizes refraction at the facets of a prism. The second configuration utilizes refraction caused by a refractive index gradient perpendicular to the propagation direction of the laser beam. In both configurations, an electric field is applied perpendicular to the direction of light propagation.

[0149] Similar to acousto-optic deflectors, electro-optic deflectors exhibit similar deflection characteristics, with deflection frequencies ranging from 1 MHz to 100 MHz and amplitudes ranging from 0.1° to 1°.

[0150] Materials suitable for manufacturing Pockels effect electro-optic deflectors include, for example:

[0151] -Lithium niobate (LiNbO3)

[0152] - Lithium tantalate (LiTaO3)

[0153] - Potassium dihydrogen phosphate (KDP) KH2PO4 and its deuterated variant (DKDP) KD2PO4,

[0154] - Potassium triphosphate (HGKTP) K3PO4 synthesized hydrothermally.

[0155] -β-barium borate (BBO)β-BaB2O4,

[0156] - Potassium titanium phosphate KTiOPO4.

[0157] Regardless of the implementation or variation, as an alternative to the galvanometer system (galvanometer reflector) of the scanner head SG, a combination of a stage (XY) capable of translation in two non-parallel directions and a focusing lens (particularly a telecentric lens integrated into the focusing subsystem F) can be used. In this implementation, the machining path is achieved by translating the XY stage rather than by oriented scanning of the laser beam via the galvanometer reflector. Due to the integrated compressed gas nozzle system, this implementation allows for the production of a laser machining head with improved removal of machining waste, resulting in better cutting quality.

[0158] Regardless of the implementation or variation, the first focusing subsystem may be a scanner head comprising two SG galvanometer mirrors and a telecentric F-θ lens FT. Regardless of the implementation or variation, the first focusing subsystem may include a compressed gas nozzle, particularly a compressed air nozzle, to remove the cut product from the focal point of the lens.

[0159] Regardless of the implementation or variation, the machining system may include a translation stage with two, three, four, five, or more axes to move the workpiece relative to the laser beam. Such a stage can be used as an alternative to or supplement to a scanner head (with a galvanometer reflector or a dual-axis translation stage).

[0160] Regardless of the implementation scheme or variant, the control subsystem PC allows the deflector and scanner head to be synchronized so as to achieve controlled taper of the sides by adjusting the advance diameter of the laser beam according to the position on the machining contour of the part.

[0161] Regardless of the implementation or variation, laser beam stabilization modules typically include a motorized biaxial mirror driven by a stepper motor, servo motor, or piezoelectric actuator. These actuators can be controlled by a closed-loop or open-loop configured electronic system to maintain the angular and linear position of the beam using the position of the beam relative to two position sensors (e.g., quadrant photodiodes or imaging cameras) as references. These sensors are typically located behind two partially transparent mirrors arranged along the beam's propagation axis.

[0162] Regardless of the implementation or variant, when the AOD is controlled via a programmable frequency synthesizer, sequences of frequencies and amplitudes corresponding to beam deflection and laser intensity, respectively, are advantageously stored in a LUT (lookup table) in memory. A clock edge from the laser system is sent to the input of the frequency synthesizer to trigger a transition from one set of LUT values ​​to the next. To ensure that the transient response triggered by this change in frequency and amplitude does not disrupt the laser beam, the beam is synchronized between two consecutive laser pulses. This synchronization is ensured by appropriately adjusting the adjustable delay generator (DG). The LUT values ​​and delay values ​​are transmitted to the generator from the control computer (PC). The delay generator can be used in either master or slave mode relative to the scanner head.

[0163] The present invention also relates to a laser processing procedure, the method for performing which is described below. Such a processing procedure can be implemented using a laser processing system as described above. The laser processing method allows for the processing of components, particularly watch components or non-watch components.

[0164] The processing method includes the following steps:

[0165] - First step E1, which adjusts the laser parameters, particularly the pulse frequency, energy and duration of the laser pulse, and the path pattern, based on the material of the part to be processed and the desired roughness of the surface to be processed, in order to achieve an ablation depth of 1 μm to 20 μm, preferably 1 μm to 10 μm, and even more preferably 2 μm to 5 μm in a single pass.

[0166] - Second step E2, which is used to adjust the laser beam divergence control system at the output of the acousto-optic deflector (AOD) according to the material of the part to be processed and the desired tilt of the side to be processed, in particular adjusting the distance between the RF telescope lenses to obtain...

[0167] (i) The distance between the focal point (or BFI plane) of the laser beam and a reference point (such as an FT lens) upstream of the focal point of the laser beam, which is greater than

[0168] (ii) The distance between the vertex of the advance cone (or the BFG plane) and a reference point (such as an FT lens) upstream of the vertex of the advance cone.

[0169] - The third step, E3, adjusts the feed rate of the laser beam on the machining plane based on the precession velocity of the laser beam obtained by the action of the acousto-optic deflector (AOD).

[0170] - Step E4: Laser processing of the component is performed using the parameters determined in steps one, two, and three.

[0171] The above solution reduces machining or cutting time for parts with straight sides by a factor of ten compared to existing solutions, outside of the watchmaking industry. According to the invention, the processing system has no moving parts, particularly rotating parts, to generate the precession of the laser beam. Precession is actually achieved using deflectors, particularly AOD or EOD. Scanning in a direction transverse to the laser beam is achieved using a galvanometer reflector (scanner head).

Claims

1. A system (1) for laser processing of components, specifically a system (1) for laser cutting of components, said system (1) comprising: - Laser source (L), which is used to emit pulsed laser beams. - First subsystem (LDO), which is used to adjust the polarization of the laser beam, particularly the half-wave plate (LDO). -At least the first and second deflectors, particularly the first and second acousto-optic deflectors (AOD), or the first and second electro-optic deflectors (EOD), have non-parallel axes, particularly perpendicular axes. - The second polarization adjustment subsystem (LQO) is used for the beam exiting the deflector, specifically one or two quarter-wave plates (LQO). - Deflector control subsystem (GRP), especially controllable radio frequency generator (GRP). - A subsystem (DG) for synchronizing the laser beam emission source (L) with the control subsystem (GRP), particularly an adjustable delay generator. - A first focusing subsystem (F), which includes a first lens (FT) and is located after a second subsystem (LQO) for adjusting the polarization of the beam exiting the deflector. - A subsystem for simultaneously controlling the divergence and deflection of the laser beam at the output of the deflector, comprising (i) a second focusing subsystem (RF), specifically a first telescope (RF), and (ii) a propagation module (SPF), the subsystem for simultaneously controlling divergence and deflection located between the output of the deflector and the first focusing subsystem (FT), and - Beam stabilization subsystem (MS) located downstream of the laser source and / or upstream of the first deflector (AOD). The system is configured to generate the spin-in of the laser beam.

2. The system (1) according to claim 1, wherein, The system (1) includes a laser beam diameter expander (EF), and in particular a second telescope (EF).

3. The system (1) according to claim 2, wherein, The beam stabilization subsystem (MS) is located between the input of the amplifier (EF) and the first deflector (AOD).

4. The system (1) according to any one of the preceding claims, wherein, The first focusing subsystem (F) includes a scanner head (SG), which includes two galvanometer mirrors.

5. The system (1) according to claim 4, wherein the system (1) includes a control subsystem (PC) configured to synchronize: - Deflector (AOD), and - Scanner head (SG) By adjusting the precession diameter of the laser beam, a controlled taper of the machined side can be obtained based on its position on the machining contour of the component.

6. The system (1) according to any one of claims 1 to 5, wherein, The first focusing lens (FT) is an F-θ telecentric lens.

7. The system (1) according to any one of claims 1 to 3, wherein, The first focusing subsystem (F) includes: - Compressed gas nozzles, particularly compressed air nozzles, are used to remove the processed product from the focal point of the first lens (FT), and - A worktable (T) for moving a component relative to a first lens (FT) along two axes, or along three axes, or along four axes, or along five or more axes.

8. The system (1) according to any one of the preceding claims, wherein, The second focusing subsystem (RF) is configured to generate a diverging portion (DP) of the laser beam outside the central focal point (C).

9. The system (1) according to any one of the preceding claims, wherein, The second focusing subsystem (RF) is the first telescope system (RF), which includes lenses with different focal lengths, specifically a first lens with a focal length of approximately 150 mm and a second lens with a focal length of approximately -100 mm.

10. The system (1) according to any one of the preceding claims, wherein, The deflector is configured to cause the laser beam to form a ring shape in a plane perpendicular to the optical axis (B), specifically a circular shape.

11. The system (1) according to any one of the preceding claims, wherein, The deflector control subsystem (GRP) controls the energy and emission of the laser pulse by controlling the deflector. Specifically, it controls the acoustic excitation of the acousto-optic deflector (AOD) or the refractive index of the electro-optic deflector (EOD) to adjust the intensity of the laser beam at the output of the deflector.

12. The system (1) according to any one of the preceding claims, wherein, The synchronization subsystem (DG) synchronizes the control subsystem (GRP), especially with the laser clock, thereby controlling the deflection amount of the deflector between two consecutive laser pulses.

13. A laser processing method, particularly a laser cutting method, for non-watch parts, comprising the following steps: - First step (E1), which is used to adjust the laser parameters, particularly the pulse frequency, energy and duration of the laser pulse, based on the material of the part to be processed and the desired roughness of the processed side, in order to achieve an ablation depth of 1 μm to 20 μm, preferably 1 μm to 10 μm, and even more preferably 2 μm to 5 μm in a single pass. - The second step (E2) involves adjusting the laser beam divergence control system located at the output of the deflector (AOD) based on the material of the part to be processed and the desired tilt of the processing side, specifically adjusting the distance between the lenses of the telescope (RF) to achieve... (i) The distance between the focal point of the laser beam and a reference point (O) upstream of the focal point of the laser beam, wherein the reference point upstream of the focal point of the laser beam is specifically the first lens (FT), and this distance is greater than (ii) The distance between the vertex of the spiral cone and the reference point (O) upstream of the vertex of the spiral cone, wherein the reference point upstream of the vertex of the spiral cone is in particular the first lens (FT). - The third step (E3) is used to adjust the feed rate of the laser beam on the machining plane based on the laser beam precession rate obtained through the action of the deflector (AOD). - Fourth step (E4), which uses the parameters determined in the first step (E1), the second step (E2) and the third step (E3) to perform laser processing on the part.

14. The method according to claim 13, wherein the method comprises: Use the system (1) according to any one of claims 1 to 12.

15. The method according to claim 13 or 14, wherein, Simultaneous control of the divergence and deflection of the laser beam allows for independent adjustment: - The position of the focal point of the laser beam; and - The position of the vertex of the spiral cone.

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