Device and method for processing material by means of laser pulses introduced in spatially statistical distribution around spatial target value

Abstract

The invention relates to a method and a device for processing a material by means of laser pulses of a pulsed laser, in which the laser pulses are introduced into the material for processing the material, in which the laser pulses (300) are introduced into the material (6) in a spatially statistical distribution around a spatial target value, and in which the laser pulses (300) are distributed in a spatially statistical distribution around the spatial target value. The statistical distribution of the laser pulses can be adjusted and set according to the current feed speed.

Description

Technical Field

[0001] The invention relates to a device and a method for processing material by means of laser pulses of a pulsed laser. Background Art

[0002] When processing materials using a pulsed laser, a regular structure is usually formed, which is achieved, for example, due to the beat frequency between the repetition rate and other processing parameters such as the feed speed and the number of repeated passes through the material. For example, such a regular structure can lead to interference effects that disturb the visual impression of the processed material.

[0003] A method and a device for laser cutting, in particular for laser cutting stents, are known from EP 3 613 228 A1.

[0004] A method for structuring a substrate surface is known from DE 10 2017 006 358 A1.

[0005] A machining process with a random triggering function for an ultrashort pulse laser is known from US 2018 / 0207748 A1. Summary of the invention

[0006] Based on the known prior art, the object of the present invention is to provide an improved method for processing materials and a corresponding device.

[0007] This object is achieved by a method for processing material having the features of claim 1. Advantageous developments emerge from the dependent claims, the description and the drawing.

[0008] Accordingly, a method for processing a material by means of laser pulses of a pulsed laser is proposed, wherein the laser pulses are introduced into the material for processing the material. According to the invention, the laser pulses are introduced into the material in a manner that is spatially statistically distributed around a spatial target value.

[0009] Here, the material to be processed can be a material such as a metal foil, a polymer or a plastic. The material to be processed can also be a semiconductor, for example an elemental semiconductor such as silicon or germanium, or a III-V semiconductor such as gallium arsenide, or an organic semiconductor or any other type of semiconductor. Exemplarily, the material can be a silicon wafer. In particular, the material can be a layer system, wherein each layer can be selected from the group consisting of a metal, a polymer, a plastic or a semiconductor. In particular, the material can also be glass, for example sapphire.

[0010] Here, the laser provides laser pulses of a laser beam, wherein each laser pulse forms a laser beam along a beam propagation direction. In particular, the laser can be an ultrashort pulse laser, wherein the pulse length of each laser pulse is preferably shorter than 10 ns, more preferably shorter than 500 ps.

[0011] Instead of a single laser pulse, the laser can also provide a laser pulse train, wherein each pulse train comprises the emission of a plurality of laser pulses. In this case, the laser pulses can be emitted very closely one after the other at intervals of a few picoseconds to a few nanoseconds in a specific time period. In particular, the laser pulse train can be a GHz pulse train, wherein the sequence of successive laser pulses of the individual pulse trains occurs in the GHz range.

[0012] The laser pulses are introduced into the material so that the material can be processed. In this context, introduction can mean that the energy of the laser beam is at least partially absorbed into the material. In this context, the focus of the laser beam can be located above the surface of the material to be processed in the beam propagation direction or below the surface in the volume of the material to be processed. The focal position can also be exactly on the surface of the material to be processed.

[0013] In particular, the term "focus" may be generally understood as a targeted area of ​​increased intensity. Therein, the laser energy is focused into a "focal region". Therefore, in particular, the term "focal point" is used below independently of the beam shape actually used and the method for causing the intensity increase. By "focusing", the position of the intensity increase along the beam propagation direction can also be influenced. For example, the intensity increase can be approximately point-shaped and the focal region can have a Gaussian-shaped intensity profile, as provided by a Gaussian laser beam.

[0014] The intensity increase can also be designed linearly, wherein a Bessel-type focal region is obtained around the focal position, as can be provided by a non-diffracting beam. In addition, other more complex beam shapes are also possible, whose focal position extends in three dimensions, such as a multi-point profile consisting of a Gaussian laser beam and / or a non-Gaussian intensity distribution.

[0015] Due to the absorbed laser beam energy, the material heats up, depending on the intensity distribution of the laser, and / or due to the electromagnetic interaction between the laser and the material is converted into a temporary plasma state. In particular, in addition to linear absorption processes, nonlinear absorption processes can also be used, which can be achieved by using high laser energy or laser intensity. Accordingly, the material is modified in particular at the focus of the laser, since this is where the intensity of the laser beam is greatest. In particular, it can be achieved that a part of the material can be removed from the material complex, for example melted or evaporated. For this purpose, known processing processes are possible with regard to the interaction between the laser and the material to be processed, which are known, for example, as laser drilling, percussion drilling or laser ablation.

[0016] By the interaction of the laser pulses with the material to be processed, material modifications can also be introduced or imparted to the material.

[0017] The material modification may be, for example, a permanent modification of the network structure of the material or of the (local) density of the material, which is caused by local heating caused by direct laser irradiation, subsequent cooling and / or electron relaxation processes.

[0018] In this case, a material modification in or on the material can be, for example, a modification of the structure, in particular the crystalline structure and / or amorphous structure and / or chemical structure and / or mechanical structure of the material.

[0019] If the material modification is introduced primarily into the volume of the material, the material modification is in the material. In contrast, if the material modification is primarily a surface modification of the material, the material modification is on the material. However, depending in particular on the focus position and the beam profile of the laser beam, the material modification can be introduced or applied both into the material and onto the material.

[0020] The material modification can also be a direct change in physical properties, such as strength and / or flexural strength and / or the resistance of the material to bending and shearing forces as well as shearing and tensile stresses. In particular, the material modification can also be a local density change, which can depend on the material selected. For example, a density change in the material can produce stress and compression areas, which have a higher material hardness than the untreated material. It is also possible that the material modification determines the visual properties of the material, for example in that the material modification scatters light transmitted through the transparent material and makes the material appear hazy.

[0021] According to the method proposed here, the laser pulses are introduced into the material in a manner that is spatially statistically distributed around a spatial target value.

[0022] The spatial target value can be given, for example, by a point or a coordinate on the material. However, the spatial target value can also be given by a track or a point set on the material.

[0023] The spatial target value can correspond to the actually set processing trajectory, for example a weld seam to be created, a segmentation contour to be introduced and / or a surface processing to be introduced. In other words, the spatial target value is the spatial position at which material processing takes place in the conventional manner and the laser pulses for processing are introduced accordingly.

[0024] The laser pulses which are spatially statistically distributed around the spatial target value therefore have a statistical distribution of the spatial distance from the spatial target value, so that the laser pulses are introduced into the material at irregular distances from the spatial target value due to the spatial distribution.

[0025] However, the laser pulses also have different spacings from one another. The spatial distribution of the spacings results, for example, via Fourier transformation, in the spatial frequency distribution of the introduced laser pulses in the spatial frequency space. The greater the spacing difference, the greater the bandwidth of the spatial frequency distribution. In particular, both the spacing to the spatial target value and the spatial frequency distribution can correspond to a statistical distribution.

[0026] This has the advantage that the laser pulses are introduced into the material at irregular spacings relative to one another, so that disruptive visual effects such as interference are reduced or avoided.

[0027] Laser pulses may also be introduced into the material in a manner that is statistically distributed in energy around an energy target value.

[0028] The energy target value can be, for example, a correspondingly selected energy. For example, due to the different energies applied, the material modification portion can have different sizes. This can further prevent patterns that appear regularly on the processed material surface or in the processed material.

[0029] The laser pulses may be statistically distributed in at least one spatial dimension.

[0030] This may mean that the laser pulses may have a statistical distribution, for example, along the x-axis, the y-axis or the z-axis.

[0031] However, this may also mean that the laser pulses may have such a statistical distribution in two or three dimensions.

[0032] For example, the laser pulses may have a Gaussian distribution along the x-axis. For example, the spacing between laser pulses along the x-axis is also a Gaussian distribution. This is because the Fourier transform of a Gaussian function is also a Gaussian function.

[0033] For example, the laser pulses can also have a Gaussian distribution along the x-axis and the z-axis. In this case, the laser pulses are then statistically distributed along the surface of the material and in the depth of the material.

[0034] The laser beam and the material can be displaced relative to one another by an advance.

[0035] "Displaceable relative to each other" means that either the laser beam is displaced translationally relative to the stationary material, or the material is displaced relative to the laser beam, or both the material and the laser beam are in motion.

[0036] In particular, the focus of the laser beam can thereby be placed at different locations on the material in order to introduce the laser pulses. In this case, the laser pulses are located in particular on so-called feed paths. The feed paths can be straight or curved, for example. In particular, the local feed direction is always the y direction, while the z axis is parallel to the surface normal and the x axis is oriented perpendicular to the y axis and parallel to the material surface.

[0037] For example, the laser beam can thereby be moved in a feed manner while the laser pulses are emitted into or onto the material.

[0038] In particular, during the feeding, the laser pulses may be output with a temporal statistical distribution (statistically distributed in time) around a temporal target value.

[0039] In particular, a temporally statistical output of the laser pulses can thus lead to a spatially statistical distribution of the laser pulses in the material, wherein the feeding then preferably takes place uniformly.

[0040] For example, if the laser outputs a series of laser pulses, the pulses are spaced apart relative to one another. In particular, the frequency of the laser pulse output in the frequency space is obtained from the temporal variation via Fourier transformation. Furthermore, if the laser pulses are spaced apart at different times, the laser pulses are distributed in the frequency space around the frequency of the laser pulse output.

[0041] The laser pulses which are statistically distributed in time around the target value thus have a distribution of the time intervals relative to one another, so that the temporal distribution results in the laser pulses being introduced into the material irregularly in time. The target value determines the time order within which the laser pulse output occurs, while the statistical distribution determines to a certain extent the fine structure of the laser pulse output. If the laser beam and the material are moved in feed during the loading with the laser pulses, the spatial statistical distribution around the target value results from the temporal statistical distribution around the target value.

[0042] Here, the time target value can be, for example, the fundamental frequency of a laser or a system clock. However, the target value can also be any type of trigger signal.

[0043] The statistical distribution of the laser pulses may correspond to a Gaussian distribution or a uniform distribution or a triangular distribution or a sawtooth distribution.

[0044] For example, the spatial target value may correspond to the expected value of a Gaussian distribution, and the statistical distribution may be characterized by the half width. For example, the expected value may be a straight line trajectory on the material, and the standard deviation may be 10 μm, where more than 68% of the laser pulses are output within ±10 μm around the trajectory.

[0045] For example, the spatial statistical distribution can be a uniform distribution, in which each spacing occurs with equal probability in an interval around a target value. The target value can be given, for example, by the center of the material. The interval can be ±100 μm around the center point of the material surface. Then, the probability that the spacing of the laser pulse to the center point is 7 μm, -8.5 μm, 9 μm, 9.3 μm, -12 μm, 56.2 μm, -99 μm and 100 μm is equal.

[0046] The spatial statistical distribution can be, for example, a triangular distribution. The spatial target value can then be the most likely value, and the fluctuation range is determined by the length of the side (Schenkel) of the probability distribution. For example, the fluctuation range can be -5 μm to +10 μm, while the target value can be 20 μm relative to the current arrival point on the feed trajectory. Therefore, the triangular distribution can show inherent asymmetry.

[0047] The spatial statistical distribution can be, for example, a sawtooth distribution. The most likely value can then be the spatial target value, and the fluctuation range is determined by the length of the falling edge of the probability distribution. The target value can be, for example, 30 μm, while the fluctuation range is +11 μm. The laser pulses then have a spatial spacing of 30 μm to 41 μm accordingly.

[0048] The time target value may correspond to the expected value of the Gaussian distribution, for example. The expected value may be given, for example, by a specific time point, and the standard deviation may be 20 μs, where more than 68% of the laser pulses are output within ±20 μs around the trajectory. For example, in the time-frequency space, the target value may be given by a frequency, such as the fundamental frequency of the laser or a regular system clock. The laser pulses may then be distributed in the time-frequency space around the fundamental frequency corresponding to the expected value.

[0049] The energy statistical distribution may be, for example, a sawtooth distribution. The target value may be, for example, 0.1 mJ, while the fluctuation range is +0.4 mJ. The laser pulses then have an energy in the range of 0.1 mJ to 5 mJ.

[0050] In particular, the laser pulses may have a spatial statistical distribution, an energy statistical distribution and / or a temporal statistical distribution.

[0051] In general, a statistical distribution can also consist of different statistical distributions. For example, a normal distribution can be superimposed on a uniform distribution. However, it is also possible that the statistical distribution is distorted. For example, a Gaussian distribution can also have a skewness.

[0052] Regular structures can be interrupted and randomized particularly easily by means of a statistical distribution of the laser pulses.

[0053] In particular, the statistical distribution may be configurable.

[0054] For example, the half width of a Gaussian distribution may be adjustable, or the expected value of the distribution may be adjustable.

[0055] For example, the temporal distribution may be adjusted more accurately than 1 μs. This may mean that the temporal output of the laser pulses is adjusted accurately to 1 μs, so that the laser pulse output in time follows the desired temporal distribution.

[0056] In particular, the feed rate can be selected such that laser pulses emitted in quick succession do not overlap.

[0057] This is the case in particular when the feed rate is greater than the ratio of the diameter of the laser focus to the time interval between the laser pulses.

[0058] If this minimum feed rate is exceeded, the introduced material modifications do not overlap. In particular, this enables a single-pulse modification that is not based on a heat accumulation of successively introduced pulses.

[0059] For example, the diameter of the laser focus is 5 μm and the repetition rate of the laser pulses is 10 kHz. This results in a minimum feed speed of 0.5 m / s.

[0060] In particular, for example, changes in the spatial and / or temporal distribution can be adapted in curves that are usually traveled at a lower speed. This prevents laser pulses introduced successively from overlapping in the workpiece.

[0061] For example, at a constant time interval, successive laser pulses may overlap in the material at low speeds. In contrast, such an overlap can be avoided if the temporal statistical distribution is broadened, for example by increasing the standard deviation and / or the expected value.

[0062] The statistical distribution of the laser pulses can be adapted to the current feed speed.

[0063] This may mean that for a first, low feed speed a first statistical distribution is used and for a second, higher feed speed a second statistical distribution is used.

[0064] For example, at low feed speeds, a uniform distribution of laser pulses can be used, since the spatial spacing of the laser pulses must be kept as large as possible in order to avoid pulse overlap. At the same time, at higher feed speeds, it makes sense to distribute the laser pulses with a Gaussian distribution so that the laser pulses are more concentrated on the feed track.

[0065] However, it is also possible to adjust the fluctuation range (eg, expected value) to be smaller at higher feed speeds, ie to make the actual spatial fluctuation range of the laser pulses on the material always similar or identical at higher feed speeds.

[0066] In particular, the temporal statistics can be adapted for the feed speed, so that, for example, the spatial statistics generated by the laser pulses on the material remain the same or change when the feed speed changes.

[0067] The statistical distribution can be adapted depending on the process stage.

[0068] For example, a first statistical distribution may be useful for a first machining process, while a second statistical distribution may be useful for a second machining process.

[0069] For example, when machining a surface, it can be useful to use a meandering feed trajectory, wherein the laser pulses are spatially Gaussian distributed around the meander. By running antiparallel through adjacent lines of the meander and overlapping the Gaussian distribution on the flanks, uniform machining of the material can be achieved on the surface.

[0070] During the segmentation process, it can be advantageous to process the material in a forward manner in the direction of the feed trajectory, i.e. the laser pulse is partially placed in front of the target position of the laser beam. Thus, for example, a spatial sawtooth distribution can be used in order to achieve a particularly clean segmentation of the material. In this case, the laser pulses are individually steered in the direction of the feed direction in front of the current position of the laser beam, so that the material is already weakened there in a targeted manner. Thus, a targeted crack propagation can take place from the current position of the laser beam, which corresponds, for example, to the individual position of the laser pulse, which current position of the laser beam corresponds to the target value.

[0071] The method according to the invention can be advantageously used in a variety of processes.

[0072] For example, the material processing process can be a segmentation process or a deep engraving process, in which the material is removed in multiple passes with a small spatial overlap of successive laser pulses. By randomizing the laser pulse output in the feed direction, a uniform distribution of the laser pulses can be achieved, resulting in high-quality cut edges or engravings. In particular, the engraving then has no periodic structure, so that there are no disruptive diffraction phenomena that could interfere with the visual impression.

[0073] The process can also be used for structuring metals or for surface destocking. Here, the visual impression depends largely on the surface quality. In particular, the randomization of the laser pulses ensures that no unwanted patterns are applied to the surface of the material.

[0074] Another important processing process is the so-called pit structuring of surfaces for anti-glare functionalization. In other words, pits or indentations can be introduced into the surface of the material with the aid of laser pulses, where the incident light is scattered. This can achieve matte surface properties of the material.

[0075] In particular, particularly advantageous visual and haptic target properties of the material can be achieved by the method according to the invention after the dimple structuring. For example, such dimple structuring can be used when processing display glasses, in particular cover glasses. In this case, for example, the gloss ("Funkeln"), i.e. a measure of irregular intensity fluctuations and color fluctuations, can be adjusted. The gloss is dependent on the size of the dimples. In particular, the gloss can be set to less than 4%. If the glass is to be used on a display with particularly high resolution, it is advantageous to reduce the size of the dimples in order to ensure low gloss values.

[0076] Another important parameter is the image sharpness. This parameter is a measure of the sharpness of the user information to be read. The sharpness of the image is inversely proportional to the scattering or diffusion of light through the display cover glass. The image sharpness can be set to more than 70% using the method according to the invention. In particular, the image sharpness can be adjusted via the surface filling of the display glass with recesses, wherein the surface filling preferably accounts for 40% to 95% of the display surface.

[0077] Another important parameter is the diffusion, which is a measure of the scattering strength of the display glass. In particular, the diffusion also depends on the shape and properties of the individual pits. For example, the diffusion of the display glass can be set to more than 22%.

[0078] In addition, the method according to the invention can avoid the moire effect, which usually occurs when the pixel period of the display panel is of the same order of magnitude as the period of the pit arrangement.The moire effect can be avoided by randomly introducing the pits into the display glass via a statistical distribution.

[0079] In particular, the material modification can also take the form of elevations, ie bumps, in the material, which are produced by brief melting and thermal expansion of the material.

[0080] In particular, a tactile change of the material surface is also achieved by material modification, in particular elevations and depressions.

[0081] For example, the roughness can be used as a tactile target value. In particular, the tactile impression can be adapted by the density of the modification. A higher density generally produces a stronger or rougher tactile impression.

[0082] By means of the successive interaction of the same material region with at least two laser pulses, so-called laser-induced periodic surface structures (hereinafter referred to as LIPSS) can also be produced.

[0083] In this context, dimples and LIPSS are suitable for functionalizing the surface of components, wherein in particular the visual properties, the wetting properties and the tribological properties can be influenced.

[0084] In a particularly preferred embodiment, pits having a diameter of between 13 μm and 20 μm are produced in this way, wherein the period of the laser-induced periodic surface structure is between 650 nm and 1000 nm.

[0085] The above-mentioned object is also achieved by a device for processing material having the features of claim 10. Advantageous further developments of the method can be found in the dependent claims, the description and the figures.

[0086] Accordingly, a device for processing materials is proposed, which includes: a system clock generator, which is designed to provide a system clock signal; a statistical generator, which is designed to receive the system clock signal, apply a time statistical distribution to the system clock signal, and provide a statistical clock signal; a laser, which is designed to receive the statistical clock signal or the system clock signal, and output a laser pulse when the clock signal is received; a feeding device, which is designed to move the laser beam and the material relative to each other; and a processing optical unit, which is designed to transfer the laser beam to the focal area and introduce it into the material, thereby processing the material.

[0087] Here, the system clock generator can provide a clock in the entire device so that all devices used can be synchronized to a common clock. Here, the system clock generator outputs a pulse base signal with a base frequency, for example.

[0088] It is also possible that the base signal of the system clock generator corresponds directly to the time target value of the statistical distribution of the pulse output in time, for example. However, it is also possible that the base signal must be passed through a suitable multiplier in order to provide the target value of the temporal pulse output. The former is always used below. However, it is also possible that the system clock generator outputs only individual signal pulses as the system clock signal, i.e. the system clock signal does not have a fixed base frequency.

[0089] The system clock generator can be built into the pulse laser itself and correspond to the repetition rate, or it can be an external pulse generator. However, it is also possible that the system clock exhibits irregularities and only represents a general trigger signal and is output by the feed device or the position shift device.

[0090] The statistics generator receives the system clock signal and can apply a statistical distribution to the signal pulses of the system clock signal. For example, the signal pulses can have a Gaussian distribution around the original signal pulses.

[0091] The statistical generator can be, for example, an FPGA or a computer or a microchip or an application-specific integrated circuit (ASIC) or a microcontroller, which makes it particularly easy to adjust to various statistical distributions, for example.

[0092] The statistical clock signal may be received by the laser, which preferably has a pulse-on-demand function. Accordingly, the laser outputs a laser pulse each time a pulse of the system clock signal is received. Therefore, the output laser pulse has the same time course as the pulse of the statistical clock signal. In other words, the pulse-on-demand signal is manipulated by the system clock generator for the pulsed laser and the statistical generator.

[0093] The statistical variation of the received base signal pulses can be achieved by means of a statistics generator with a clock rate of more than 1 MHz. This has the advantage that the statistics generator can reliably impose the same statistical distribution on the pulses of the base signal even at very high clock rates.

[0094] The device also has a processing optical unit that can focus the laser beam into the material. In particular, the processing optical unit can convert an angular deviation into a location deviation, so that in the case of a statistical angular deviation described below, a statistical location deviation can be generated particularly easily.

[0095] The laser beam can be focused into / onto the workpiece by means of a processing optical unit or a scanner unit, wherein the numerical aperture of the processing optical unit is NA>0.01 and the numerical aperture of the scanner unit is NA<0.1.

[0096] For example, the numerical aperture of the processing optical unit is between 0.01 and 0.2, in particular 0.04.

[0097] Here, the numerical aperture NA primarily refers to the opening angle of the laser beam at the focus, wherein a large numerical aperture means a large opening angle. This allows the extension of the focal region in the beam propagation direction to be adjusted, and thus also the size of the material modification in the beam propagation direction to be adjusted.

[0098] The apparatus may also include a feed device for moving the laser beam and the material relative to each other.

[0099] The feed device may preferably comprise an axis device and / or a scanner device.

[0100] For example, the material can be moved mechanically by means of an axis arrangement, while the scanner arrangement serves to move the laser beam over the material. In particular, the axis arrangement can be an XYZ stage with stepper motor control. However, it is also possible that, in order to achieve the fastest possible adjustment, the axis arrangement is designed to have a piezoelectric adjustment section. In particular, the scanner arrangement can be a galvanometer scanner. However, the feed device can also be a roll-to-roll device.

[0101] The feed device can receive the system clock.

[0102] For example, the system clock can be used to clock a stepper motor so that a certain number of steps is performed per second. Thus, by adjusting a multiplier on the motor, the feed speed can be adjusted particularly easily. For example, the system clock can be a regular clock with which the scanner periodically deflects the laser beam on the material.

[0103] The feed device may receive a statistical clock signal.

[0104] For example, the feed device can form a non-uniform feed path, thereby also producing a statistical distribution around the feed path, in particular also in the direction of the feed path.

[0105] However, it is also possible for the feed device to provide the system clock.

[0106] Therefore, the feed device itself outputs a system clock which is sent to the statistical generator. External components for generating the system clock are thus omitted and the laser pulse output is automatically adapted to the feed device and thus to the current position and speed.

[0107] In the simplest case, the feed device can output a system clock signal each time it moves a certain length. In this case, the laser pulses can be output automatically depending on the distance traveled and independently of the feed speed. In this case, this is called a position synchronization signal, which is output by the feed device. In particular, the current speed can be estimated from the position synchronization signal in order to adapt the statistical distribution if necessary.

[0108] The device can have a position offset device which is designed to receive the statistical clock signal and to impart a spatial statistical distribution about a spatial target value to the laser pulses.

[0109] In particular, the position shifting device may be an electro-optical deflector and / or an acousto-optical deflector and / or be based on coherent beam combining.The position shifting device may receive a statistical clock signal and deflect the laser pulses accordingly.

[0110] In an acousto-optic deflector, an acoustic wave is generated in an optically adjacent material by an alternating voltage across a piezoelectric crystal, which periodically modulates the refractive index of the material. In this case, the wave can propagate through the optical material, for example as a propagating wave or wave packet or a standing wave. Due to the periodic modulation of the refractive index, a diffraction grating for the incident laser beam is realized. The incident laser beam is diffracted at the diffraction grating and is thus at least partially deflected at an angle to its original beam propagation direction. The grating constant of the diffraction grating and therefore the deflection angle depends in particular on the wavelength of the acoustic wave and therefore on the frequency of the applied alternating voltage.

[0111] Electro-optical deflectors are based on prisms made of electro-optical crystals. By applying a voltage, the refractive index of the electro-optical crystal changes, causing the path of the laser beam through the prism to also change.

[0112] The spatial statistical distribution achieved by the electro-optical deflector and / or the acousto-optical deflector can be performed at a clock rate exceeding 1 MHz. Accordingly, the laser pulse can be repositioned millions of times per second. In particular, the single pulse of the laser pulse can be accurately repositioned by the electro-optical deflector and / or the acoustic deflector, so that each single laser pulse is introduced into a different position on the material.

[0113] However, the position shifting device can also be a swinging prism. Here, the swinging prism includes a prism that performs an angular deflection of the laser beam. The spatial deflection of the laser beam is achieved by mechanical deflection of the prism.

[0114] The wavelength of the laser pulses can be between 200nm and 3000nm. This makes the method adaptable to many different materials and processes.

[0115] The repetition rate of the laser light can be between 10 kHz and 100 MHz, in particular between 19 kHz and 2 MHz. The repetition rate determines the time interval between the output of at least two successive laser pulses.

[0116] The laser pulse may consist of a plurality of laser pulse trains, in particular of 2 to 100 laser pulse trains. In this case, instead of a single laser pulse, a laser pulse train may be output at a particularly high frequency of more than 1 GHz. In this case, instead of a single pulse deflection, a single laser pulse train deflection is used.

[0117] The energy fluence can be greater than 0.05 J / cm^2, in particular between 0.1 J / cm^2 and 50 J / cm^2. This makes the method adaptable to many different materials and processes.

[0118] The laser pulse duration may be between 10 fs and 100 ns, in particular between 100 fs and 100 ps.

[0119] For example, the length of the laser pulse can be between 100ps and 100ns, in particular between 1ns and 20ns, wherein the wavelength can be between 300nm and 550nm, in particular 355nm, wherein the repetition rate of the laser pulse can be between 10kHz and 100kHz, in particular between 10kHz and 50kHz, wherein the energy of the laser pulse can be between 60μJ and 300μJ, and 1 to 4 pulses can be output at each point.

[0120] For example, the length of the laser pulse can be between 200fs and 1000fs, in particular between 300fs and 450fs, wherein the wavelength can be between 900nm and 2300nm, in particular 1030nm, wherein the repetition rate of the laser pulse can be between 10kHz and 400kHz, wherein the laser pulses are output in a laser pulse train, wherein each laser pulse train can contain 2 to 4 laser pulses, wherein the energy of the laser pulse train can be between 100μJ and 400μJ, and the numerical aperture can be between 0.01 and 0.2, in particular 0.08.

[0121] In particular, the laser may further include an unstable seed laser and an amplifier, wherein the unstable seed laser includes a statistical generator and outputs laser pulses with a temporal statistical distribution, and wherein the amplifier amplifies the laser pulses of the seed laser.

[0122] Furthermore, the laser beam may have a Gaussian beam shape or a non-diffractive beam shape.

[0123] A Gaussian beam is to be understood in particular as a beam whose intensity cross section corresponds to a Gaussian bell curve.

[0124] A non-diffracting light beam and / or a Bessel-type light beam (quasi-Bessel light beam) is to be understood in particular as a light beam whose transverse intensity distribution is propagation-invariant. In particular, for a non-diffracting light beam and / or a Bessel-type light beam, the transverse intensity distribution is substantially constant along the longitudinal direction and / or propagation direction of the light beam.

[0125] For the definition and properties of non-diffracted beams, refer to the following book: "Structured Light Fields: Applications in Optical Trapping, Manipulation and Organisation", M. Springer Science & Business Media (2012), ISBN 978-3-642-29322-1. This document is expressly and in its entirety cited.

[0126] Accordingly, non-diffracting laser beams have the advantage that they can have an intensity distribution that is elongated in the beam propagation direction and is significantly larger than the lateral extent of the intensity distribution. In particular, this can produce material modifications that are elongated in the beam propagation direction, so that these material modifications can penetrate both sides of the workpiece particularly easily.

[0127] Furthermore, the laser beam may have a flat top beam shape and / or a super Gaussian beam shape and / or a top hat beam shape. BRIEF DESCRIPTION OF THE DRAWINGS

[0128] The preferred further embodiments of the present invention are described in more detail by the following description of the accompanying drawings. In the accompanying drawings:

[0129] FIG1 shows a schematic structure of a device according to the prior art;

[0130] Figure 2A , Figure 2B , Figure 2C and Figure 2D shows a further schematic structure of the device according to the present invention;

[0131] Figure 3 shows a further schematic structure of the device according to the present invention;

[0132] FIG4 shows a method according to the prior art;

[0133] Figure 5A and Figure 5B A method with spatial statistical distribution of laser pulses according to the present invention is shown;

[0134] Fig. 6A and Figure 6B The method with spatial statistical distribution and temporal statistical distribution of laser pulses according to the present invention is shown;

[0135] Figure 7 A further method according to the invention with a spatial statistical distribution and a temporal statistical distribution of laser pulses is shown; and

[0136] Figure 8 A further method according to the invention is shown with a spatial and temporal distribution of the laser pulses. DETAILED DESCRIPTION

[0137] Preferred embodiments are described below with reference to the accompanying drawings. Here, in different figures, the same, similar or elements having the same effect are provided with the same reference numerals, and repeated descriptions of these elements are partially omitted to avoid redundancy.

[0138] FIG1 schematically shows a device for processing a material 6 according to the invention. Here, the device has a system clock generator 1. The system clock generator 1 preferably outputs a signal pulse of a fixed frequency, i.e., a system clock signal. In particular, the system clock generator 1 can be a pulse generator. However, as described below, the system clock generator 1 can also be formed internally in one of the other installed device elements.

[0139] The system clock generator 1 is designed to send a system clock signal to a statistics generator 2. The statistics generator 2 receives a pulsed base signal from the system clock generator 1 and can impose a statistical distribution on the pulses of the base signal. In particular, the statistics generator 2 can change the intervals between the pulses of the system clock signal so that the signal pulses of the system clock signal have a statistical distribution. For example, the intervals between the pulses of the base signal can be adapted for this purpose. For example, the statistical distribution can be derived from the time intervals of the adapted signal pulses to the unchanged pulses of the system clock signal.

[0140] These statistical clock signals can be received by the laser 3. For each signal pulse received by the laser 3, the laser 3 outputs a laser pulse 300 that propagates along the laser beam 30 of the laser 3. This function is also called pulse on demand. The laser pulse 30 can then be focused into the material 6 or onto the surface of the material 6 by the processing optical unit 5. Thus, the laser pulses 300 are introduced with a statistical distribution of the statistical generator 2.

[0141] The laser pulse 300 can induce material processing in the material 6 , so that processing of the material 6 takes place.

[0142] The feed device 4 can move the material 6 and the laser beam 30 relative to each other, so that the laser beam 30 moves along the feed path with a feed amount. For example, the feed device is designed as a scanner device, with which the laser beam 30 is periodically moved on the material 6. When the laser pulses 300 are triggered and introduced into the material 6 with the statistical distribution during the feed, the material modification also exists in the material 6 with a certain statistical distribution. In particular, it should be emphasized here that the statistical distribution of the laser pulses 300 is a distribution in time, while the statistical distribution of the material modification in the material 6 exhibits a statistical distribution in place due to the simultaneous feeding.

[0143] Figure 2A1 shows a device according to the invention. Here, the pulse generation of the laser 3 is carried out similarly to FIG. 1 . However, a position shifting device 7 is arranged downstream of the laser 3 in the direction of beam propagation. For example, the position shifting device 7 can be an acousto-optic deflector. The acousto-optic deflector 7 also receives a signal from the statistical generator 2 and can spatially deflect the laser pulse 300 triggered by the laser 3 accordingly. Here, for example, the time deviation of the signal pulse from the fundamental frequency can be converted into a spatial deflection. At the same time, the laser 3 can receive a statistical clock signal from the statistical generator 2 and impose a time variation on the laser pulse 300.

[0144] However, it can also be, Figure 2B As shown, only the position shifting device 7 affects the spatial statistical distribution of laser pulses 300, and the laser 3 is operated via the system clock generator 1. Here, the laser 3 outputs laser pulses 300 at regular intervals according to the fundamental frequency, and only the position shifting device generates the spatial statistical distribution of laser pulses 300.

[0145] However, it can also be, Figure 2C As shown, the feed device 4 outputs a system clock signal and thus triggers a laser pulse 300 , for example, after a certain path has been traveled. In addition, the system clock signal can be influenced by the statistics generator 2 , so that the position shifting device 7 causes an additional spatial statistical distribution of the laser pulses 300 .

[0146] It can also be, Figure 2D As shown, the feed device 4 outputs a system clock signal and influences the system clock signal via the statistical generator 2. In particular, the laser 3 can thus receive the statistical clock signal, thereby, for example, enabling pulse triggering corresponding to the statistical distribution. In addition, the position shifting device 7 can cause a spatial statistical distribution of the laser pulses 300 via the received statistical signal.

[0147] Furthermore, it is also possible that the laser 3 also receives a statistical clock signal and is thus subjected to an additional temporal statistical distribution.

[0148] exist Figure 3 Another possible embodiment of the device is shown in FIG. Here, the laser 3 includes an unstable seed laser 34 and an amplifier 36. If the seed laser 34 receives a pulse of a base signal from a system clock generator, the seed laser outputs a laser pulse, which is amplified by the amplifier. Thus, the output of the laser pulses in time achieved by the seed laser 34 is inherently statistically distributed due to instability.

[0149] Figure 4 shows a method according to the prior art. Here, laser pulses are output at regular intervals and introduced into the material. Therefore, the laser pulses have only one temporal frequency, namely the repetition frequency.

[0150] When the laser 3 outputs laser pulses 300, the material 6 can be uniformly moved relative to the laser beam 30 by means of the feeding device. Therefore, the laser pulses 300 also have uniform spacing on the material 6, so that the laser pulses have only one spatial frequency in the spatial frequency space.

[0151] Figure 5A The method according to the invention for processing a material 6 by means of a laser pulse 300 of a pulsed laser 3 is shown, wherein the laser pulse 300 is introduced into the material 6 for processing the material 6. In the present case, the laser 3 outputs the laser pulse 300 at a specific frequency, which corresponds, for example, to the system clock of the system clock generator 1. Here, the triggered laser pulse falls on the position shifting device 7, by which the triggered laser pulse is deflected. For example, the position shifting device 7 can be controlled via the statistical generator 2. Accordingly, the laser pulse 300 is deflected with a statistical distribution, for example, perpendicular to the feed direction. By deflecting the laser pulse 300, the laser pulse is therefore spatially statistically distributed around the feed trajectory.

[0152] Figure 5B The laser beam 30 is periodically moved in a meandering manner over the material 6, while the laser pulses are deflected perpendicularly to the trajectory by a position shifting device 7. Due to the uniform pulse output, the laser pulses are present in a regular pattern in the y direction, but have a spatial statistical distribution perpendicular to the meandering structure.

[0153] However, in addition to the spatial statistical distribution achieved by the position shifting device 7, the laser 3 can also output laser pulses 300 with a temporal statistical distribution, for example, by triggering a pulse-on-demand function of the laser 3 with the aid of a signal from the statistical generator 2. Fig. 6A The time statistics of the laser pulse output can be shown in the case of the existing feed, where the laser pulses 300 are also distributed along the feed direction, such as Figure 6B Here, the laser pulses have a Gaussian distribution both in the x-direction and in the y-direction. In particular, the laser pulses 300 are also offset from one another in the feed direction (at a constant feed speed).

[0154] like Figure 7 As shown, the temporal statistical distribution and the spatial statistical distribution may also be different distributions, such as triangular distribution and uniform distribution.

[0155] Figure 8It is also shown that the pulses of the system clock signal (dashed line) can be triggered at irregular intervals, for example because the feed device 4 outputs such a system clock signal only after a certain distance has been traveled. In particular, such irregular pulse output in time space can be formed at non-uniform speeds. Since the statistical generator 2 receives the signal from the feed device 4, an additional time statistical distribution can be applied, so that the laser pulses are introduced into the material 6 at irregular intervals.

[0156] To the extent applicable, all individual features presented in the embodiments may be combined with one another and / or interchanged without departing from the scope of the invention.

[0157] Reference numerals list

[0158] 1 System clock generator

[0159] 2 Statistics Generator

[0160] 3 Lasers

[0161] 30 laser beams

[0162] 32 Focus Area

[0163] 300 laser pulses

[0164] 34 seed lasers

[0165] 36 amplifiers

[0166] 4 Feeding device

[0167] 40-axis device

[0168] 42 Scanner device

[0169] 400 feed track

[0170] 5. Processing optical unit

[0171] 6 Materials

[0172] 7. Position offset device

Claims

1. A method for processing a material (6) by means of laser pulses (300) of a pulsed laser (3), wherein: The laser pulses (300) are introduced into the material (6) to process the material (6), It is characterized in that The laser pulses (300) are introduced into the material (6) in a spatially statistically distributed manner around a spatial target value, wherein the statistical distribution of the laser pulses is adjustable and adapted as a function of the current feed speed.

2. The method according to claim 1, characterized in that The laser pulses (300) are statistically distributed in at least one spatial dimension.

3. The method according to any one of claims 1 or 2, characterized in that The laser beam (30) and the material (6) are moved relative to one another in an advance manner, wherein the advance speed is in particular greater than 50 mm / s.

4. The method according to any one of the preceding claims, characterized in that During the feeding, the laser pulses are output in a manner that is temporally statistically distributed around a temporal target value.

5. The method according to any one of the preceding claims, characterized in that The statistical distribution of the laser pulses (300) corresponds to a Gaussian distribution, a uniform distribution, a triangular distribution, or a sawtooth distribution.

6. The method according to any one of the preceding claims, characterized in that The statistical distribution has an upper cutoff value and / or a lower cutoff value.

7. The method according to any one of the preceding claims, characterized in that Laser pulses emitted in quick succession do not overlap.

8. The method according to any one of the preceding claims, characterized in that The temporal statistical distribution of the laser pulses is adapted as a function of the current feed speed.

9. A device for processing a material (6), the device comprising: A system clock generator (1), which is designed to provide a system clock signal; A statistical generator (2) designed to receive a system clock, apply a time statistical distribution to the system clock, and provide a statistical clock signal; A laser (3) designed to receive the statistical clock signal or the system clock signal and output a laser pulse (300) when receiving the clock signal; a feeding device (4) designed to move the laser beam (300) and the material (6) relative to each other; A processing optical unit (5) is designed to transmit the laser beam (30) to a focal region (32) and introduce it into the material (6), thereby processing the material (6).

10. The device according to claim 9, characterized in that A position shifting device (7) is provided, which is designed to receive the statistical clock signal and to impart a spatial statistical distribution around a spatial target value to the laser pulse (300).

11. The device according to any one of claims 9 or 10, characterized in that The feeding device (4) receives the system clock signal or receives the statistical clock signal or provides the system clock signal.

12. The device according to any one of claims 9 to 11, characterized in that The position shifting device (7) is an electro-optical deflector and / or an acousto-optical deflector and / or is based on coherent beam combination, which receives the statistical clock signal and deflects the laser pulse (300) accordingly, wherein, preferably, the spatial statistical distribution is carried out at a clock rate exceeding 100 kHz, preferably 1 MHz.

13. The device according to any one of claims 9 to 12, characterized in that - the wavelength of the laser pulse (300) is between 200 nm and 3000 nm, and / or - the laser light has a repetition rate between 10 kHz and 100 MHz, in particular between 10 kHz and 100 MHz, and / or - the laser pulse (300) consists of a plurality of pulse trains, in particular 2 to 100 pulse trains, and / or - an energy fluence greater than 0.05 J / cm^2, in particular between 0.1 J / cm^2 and 50 J / cm^2, and / or The laser pulse duration is between 10 fs and 100 ns, in particular between 100 fs and 100 ps.

14. The device according to any one of claims 9 to 13, characterized in that The laser beam (30) has a Gaussian beam shape or a non-diffraction beam shape, in particular a flat top beam shape and / or a super Gaussian beam shape and / or a top hat beam shape.

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