Device and method for treating workpiece

Abstract

The invention relates to a device for treating a workpiece (4), in particular applying an anti-glare functionalization, by means of laser pulses (100) of a laser (1), comprising: a laser (1), in particular a short-pulse laser or ultra-short-pulse laser, which is arranged to provide a laser beam (10) having laser pulses (100); at least one scattering disk (2) arranged to scatter the laser beam (10); and at least one focusing optics (3) arranged to focus the laser beam (10) onto a focusing zone (120) on a focal plane (12) on the workpiece (4), where the workpiece (4) is applied with the laser beam (10) and thus processed, and the scattering disk (2) is arranged to apply a locally randomized intensity distribution on the focal plane (12) on the laser beam (10).

Description

Technical Field

[0001] The present invention relates to an apparatus and a method for processing a workpiece. Background Art

[0002] It is well known that during laser material processing, material can be removed from a workpiece by vaporizing or compacting the material within the focal zone of the laser beam due to the intense light-matter interaction. The resulting structures are known as recesses. In this regard, recesses are suitable for functionalizing the surface of a component, where, in particular, optical and tribological properties can be influenced.

[0003] However, when processing materials with pulsed lasers, regular structures, in particular regularly arranged recesses, often occur, for example due to the beat frequency between the repetition frequency of the laser system and other processing parameters such as the feed rate and the number of repetitions of the material pass. For example, such regular structures can lead to interference effects that disrupt the visual impression of the processed material when viewed.

[0004] For example, EP 3 735 332 B1 discloses an optical device for direct laser interference structuring, wherein a laser beam emitted by a laser beam source is split into two partial beams, and these partial beams are guided in an interfering manner onto the surface of a component using focusing optics to form structures. Summary of the Invention

[0005] Starting from the known prior art, the object of the present invention is to provide an improved device for processing materials and a corresponding method.

[0006] This object is achieved by a device for processing material having the features of claim 1. Advantageous developments emerge from the dependent claims, the description and the drawings.

[0007] Therefore, a device for processing a workpiece by means of laser pulses, in particular for applying an anti-glare functionalization, is proposed. The device comprises: a laser, in particular a short-pulse laser or an ultrashort-pulse laser, which is configured to provide a laser beam having laser pulses; at least one scattering disk, which is configured to scatter the laser beam; and at least one focusing optical element, which is configured to focus the laser beam onto a focal region in a focal plane on the workpiece, wherein the workpiece is exposed to the laser beam and thus processed. According to the invention, the scattering disk is configured to apply a locally randomized intensity distribution to the laser beam in the focal plane.

[0008] The material of the workpiece can be, for example, a polymer or plastic. The material can also be a semiconductor, for example, an elemental semiconductor such as silicon or germanium, a III-V semiconductor such as gallium arsenide, an organic semiconductor, or any other type of semiconductor. For example, the material can be a silicon wafer. However, the material can also include any metal, such as aluminum, magnesium, titanium, iron, or a steel alloy. In particular, the material can be a layer system, wherein each layer can be selected from any group of metals, polymers, plastics, or semiconductors. In particular, the material can also be a glass, such as sapphire or quartz glass.

[0009] The laser provides laser pulses of a laser beam, wherein the individual laser pulses form a laser beam in the beam propagation direction. The pulse duration of the laser pulses can be between 300 fs and 100 ps. The wavelength of the laser pulses can be between 300 nm and 3000 nm, preferably between 900 nm and 2200 nm.

[0010] Instead of individual laser pulses, the laser can also provide a laser pulse train, wherein each pulse train comprises the emission of multiple laser pulses. Thus, the laser pulses can be emitted very quickly in succession at intervals of a few picoseconds to a few nanoseconds within a specific time interval. In particular, the laser pulse train can be a GHz pulse train, wherein the sequence of successive laser pulses of the respective pulse train occurs in the GHz range. For example, the pulse train can comprise 2 to 20 laser pulses, preferably 2 to 10 laser pulses, wherein the time intervals between the laser pulses are between 10 ns and 50 ns. However, the pulse train can also comprise 30 to 300 laser pulses, wherein the time intervals between the laser pulses are between 100 ps and 1000 ps.

[0011] The repetition rate of the laser pulses and / or laser pulse trains can be greater than 1 kHz, preferably greater than 10 kHz. For example, the repetition rate can be 100 kHz or higher. For example, the laser emits more than 1000 pulses per second or more than 10,000 pulses per second.

[0012] The pulse energy of the laser pulse may be greater than 1 μJ, for example 2 μJ.

[0013] The diameter of the laser beam provided by the laser may be larger than 0.1 mm, for example 1 mm or 5 mm.

[0014] After passing through the remaining device, the laser pulse is introduced into the material, wherein the energy of the laser beam is at least partially absorbed into the material, for example by nonlinear interactions, in particular by multiphoton processing.

[0015] An incident laser beam from a laser first passes through a scattering disk. This scattering disk is configured to scatter the laser beam. This may mean, in particular, that the laser beam is converted into a plurality of partial laser beams, each with its own propagation direction and / or its own intensity and / or its own phase wavefront. In particular, the beam propagation direction of a partial laser beam may differ from the beam propagation direction of the incident laser beam.

[0016] Multiple partial laser beams are superimposed on a focal region on a focal plane via focusing optics, such as a 2f optical system. The focal point of the scattered laser beam can be on the workpiece along the beam propagation direction. The focal plane is on the workpiece when it is perfectly aligned with the workpiece surface or when it is above or below the surface in the beam propagation direction while the surface is still being processed. In particular, the focal position can be within ten times the Rayleigh length from the surface, where the Rayleigh length is the distance along the optical axis required for the laser beam to double its cross-sectional area from the beam waist or focal point.

[0017] In particular, the term "focusing" is generally understood to mean a targeted increase in intensity, wherein the laser energy is concentrated in a "focusing region." Therefore, in particular, the term "focusing" is used below without regard to the actual beam shape used and the method used to induce the intensity increase. The position of the focusing region along the beam propagation direction can also be influenced by the focusing. For example, the focusing region can be almost point-shaped and have a Gaussian intensity profile, such as that provided by a Gaussian laser beam. The focusing region can also be linear or rectangular, or have the shape of an Airy distribution. Furthermore, other more complex beam shapes are possible, whose focus position extends in three dimensions, such as a multi-point profile of a Gaussian laser beam and / or a non-Gaussian intensity distribution.

[0018] Due to the energy absorbed from the laser beam in the focal zone, the material heats up, depending on the intensity distribution of the laser light in the focal zone, and / or is transformed into a temporary plasma state due to the electromagnetic interaction between the laser light and the material. In particular, in addition to linear absorption processes, nonlinear absorption processes can also be used, which are made possible by using high laser energy or laser intensity. Thus, the material is modified particularly in the focal zone of the laser light, since this is where the intensity of the laser beam is greatest. This is particularly possible when some of the material can be released from the composite material of the workpiece, for example by melting or vaporizing it. Therefore, regarding the interaction between the laser beam and the material of the workpiece to be processed, known process methods are possible, such as laser drilling, irradiation drilling, laser ablation, sandblasting, or compaction.

[0019] The interaction of the laser pulses with the material of the workpiece to be processed causes a corresponding material modification on the surface of the workpiece. In particular, laser pulses or trains of laser pulses can be used to produce the material modification.

[0020] This material modification occurs due to the intensity of the irradiated laser light, which vaporizes the material on the workpiece surface. In particular, the workpiece material vaporizes when the intensity of the laser beam exceeds a critical, material-specific processing threshold. Therefore, the shape and form of the laser beam, and in particular the intensity distribution of the laser beam in the focal plane, are crucial to the shape and form of the material modification.

[0021] For example, in the absence of a scattering disk, the laser beam has a Gaussian beam profile. A specific spatial region is formed around the focal point where the laser energy is above a critical threshold. In other words, within the intensity distribution of the laser beam at the focal point, there is a region of equal intensity, where the material can be vaporized. The shape and form of the material modification are determined by this region of equal intensity. In particular, the material modification can have a circular or elliptical cross-section in the plane of the material surface, with the material modification having a depth that gradually increases from the edge to the center. In particular, the cross-section of the material modification in a plane perpendicular to the surface can also be circular or rounded. However, the material modification can also have an elliptical or circular cross-section in the plane of the material surface, but with a steep edge slope, resulting in a substantially rectangular cross-section of the material modification in a plane perpendicular to the material surface. For example, such a material modification can also have a uniform depth.

[0022] However, when a scattering disk is located in the device's beam path, the laser beam is randomly scattered, resulting in a locally randomized intensity distribution in the focal plane. Consequently, the laser beam striking the scattering disk is scattered into a plurality of partial laser beams, whose intensities and propagation angles have a random or statistical distribution, such as a normal or Gaussian distribution. The intensities and propagation angles can also be distributed statistically, band-limited, such that the maximum and minimum propagation angles of the partial laser beams are determined by the shape and form of the scattering disk. This results in a random or statistical component to the intensity profile in the focal plane, exhibiting randomly distributed intensity peaks or valleys, each of which results in a particularly strong or weak material treatment. In particular, this scattering can impart a speckle pattern to the laser beam in the focal plane, such as that defined in Goodman's "Speckle phenomena in optics: theory and applications," Roberts and Company Publishers, 2007. This locally randomized intensity distribution enables non-uniform material treatment, thereby avoiding regular and / or smooth treatment structures in individual material modifications.

[0023] By introducing such an inhomogeneous material modification onto the surface of a material with the aid of a locally randomized intensity distribution, it is possible to modify the optical properties of the material, for example, by causing light guided through the transparent material to scatter at the material modification, thereby making the material appear diffuse and / or matte. In particular, such a material modification on the surface of the workpiece material can reduce reflections from the material.

[0024] For example, the tactile feel or the roughness can be adjusted by the type and shape of the material modification and its distribution over the surface of the component. However, it is also possible to adjust the scattering of light and thus the optical properties of the material.

[0025] In particular, material modification can be used to produce anti-glare functionalization. This anti-glare functionalization can include the incident light beam reflecting off the surface at more than just the angle of reflection according to Snell's law of refraction. In particular, it can also include the incident light beam reflecting or scattering off the surface at other angles. In particular, the incident light beam is directed into different spatial directions so that no sharp reflections occur—that is, the entire energy of the incident light beam is detected at a specific exit angle. More specifically, the energy of the incident light beam is distributed over a spatial region so that the energy of the incident light beam can be detected across a range of exit angles.

[0026] The at least one scattering disk may be arranged to scatter the laser beam in a transmissive or reflective manner.

[0027] For example, the scattering disk can transmit an incident laser beam, causing the laser beam to propagate through the scattering disk and thereby scatter. For example, the laser beam can be scattered at the scattering disk, causing the laser beam to be reflected by the scattering disk instead of penetrating the scattering disk. For example, the scattering disk can be a non-flat mirror having an irregular pattern.

[0028] At least one scattering disk can have a phase pattern, in particular a binary phase pattern, which is provided to impart a position-dependent phase difference to the laser beam; in particular, the phase pattern can be imparted in one or two dimensions.

[0029] The scattering disk has scattering regions that locally affect or do not affect the phase of the incident laser beam. Different scattering regions are randomly distributed on the scattering disk, so that the scattering of the laser beam depends on the irradiation point on the scattering disk.

[0030] For example, after being scattered at the first scattering region, the first partial laser beam may have a phase shift relative to the second partial laser beam. This phase shift may cause the partial laser beam to deviate from its original propagation direction.

[0031] The number of different phase shifts that can be generated using a scattering disk is determined by phase quantization of the scattering disk. At a phase quantization of 2, the scattering disk exhibits a binary phase pattern. With a binary phase pattern, only two phase shifts can be generated between the partial laser beams, for example, 0° and 180°. At a phase quantization of four, four different phase shifts can be generated, for example, 0°, 90°, 180°, and 270°. However, a scattering disk can also allow, for example, 8 or 16 different phase shifts between the partial laser beams.

[0032] For example, the first scattering region can have a first material thickness, and the second scattering region can have a second material thickness. If the scattering disk is reflective, the first thickness and the second thickness can be selected so that the path difference of the reflected partial laser beams corresponds to half a wavelength. Thus, adjacent partial laser beams at the scattering regions have a phase difference of 180°.

[0033] However, the laser beam can also be transmitted through a scattering disk having scattering regions of different thicknesses, wherein the different thicknesses of the scattering regions provide different optical path lengths. If the optical path lengths differ by half a wavelength, the phase difference of the parts of the laser beam is 180°.

[0034] If the scattering disk has a binary pattern, this can mean that the scattering disk provides only two different optical path lengths. This pattern can be distributed within the geometric extent of the scattering disk, so that the scattering disk has, for example, statistically distributed regions of a first thickness and regions of a second thickness.

[0035] If the scattering disk has a binary pattern in two dimensions, this may mean that the scattering disk has randomly distributed scattering areas in both height and width. However, if the scattering disk has a binary pattern in only one dimension, this may mean that the scattering disk has randomly distributed scattering areas only in height or width. For example, the binary pattern corresponds to a striped pattern.

[0036] In particular, the spatial frequency of the locally randomized intensity distribution can be adjusted via the size of the scattering area of ​​the scattering disk. The spatial frequency can be understood as the inverse of the period length of the scattering area. For example, if the scattering disk has a small rectangular scattering area, this will result in a large spatial frequency of the locally randomized intensity distribution and, therefore, a particularly inhomogeneous intensity distribution.

[0037] For example, the edge length of a pixel may be greater than 1 μm, such as 20 μm or 100 μm.

[0038] The scattering disk can be a spatial light modulator or a diffractive optical element.

[0039] The spatial light modulator can be, for example, a nanograting or a hybrid element, which can impose a defined phase distribution on the laser beam through its intrinsic structure or configuration. However, the light modulator can also be, for example, a spatial light modulator, whose cells or pixels influence the laser beam through tunable birefringence properties.

[0040] Diffractive optical elements (DOEs) are similar to light modulators and are designed to influence an incident laser beam in two spatial dimensions with respect to one or more properties. In contrast to LCD-based spatial light modulators, DOEs are fixed components that can be used to precisely generate a specific beam shape from an incident laser beam. Typically, DOEs are specially formed diffraction gratings, which diffract the laser beam into the desired beam shape.

[0041] At least two scattering disks can be provided and scatter the laser beam in succession, wherein a first scattering disk can be moved relative to a second scattering disk, in particular rotated or displaced relative to the second scattering disk.

[0042] By rotating or shifting, the laser beam's impingement point on the scattering disk can be changed. Because the scattering properties at different impingement points vary, a first laser pulse can have a first locally randomized intensity distribution, while a second laser pulse can have a second locally randomized intensity distribution, where the intensity distributions differ.

[0043] For example, the second scattering disk can be rotated, and then two consecutive pulsed scattered laser beams irradiate different positions on the rotating scattering disk, so that the intensity distribution of the first laser pulse in the focal plane is different from the intensity distribution of the second laser pulse.

[0044] However, the first scattering disk can also be rotated so that the laser pulses illuminate different scattering areas of the first scattering disk, while different intensity distributions always illuminate the second scattering disk.

[0045] However, the first scattering disk and the second scattering disk can also be rotated, for example, at different rotation frequencies. This further randomizes the intensity distribution in the focal plane. In particular, the scattering disks can also be rotated relative to each other, i.e., in opposite directions.

[0046] However, the second scattering disk can also be displaced laterally relative to the first scattering disk, ie perpendicularly to the beam propagation direction. The first disk can also be displaced laterally relative to the second disk. However, the first scattering disk and the second scattering disk can also be displaced laterally relative to each other.

[0047] The scattering disk can also be moved in an oscillatory manner, for example, using a piezoelectric actuator to which an AC voltage is applied. The AC voltage causes the piezoelectric actuator to periodically expand and contract according to the AC voltage frequency, thereby causing an oscillatory displacement of the scattering disk. For example, the frequency of the AC voltage can be greater than 100 Hz, preferably greater than 1 kHz. The amplitude of the movement can be, for example, 10 μm, 100 μm, or 1 mm, or values ​​therebetween.

[0048] The advantage of this is that different randomized intensity distributions can be generated in the focal plane, for example, by using a statically formed scattering disk with a fixed binary pattern that in principle scatters the laser beam uniformly. This makes it possible to avoid periodic, repetitive patterns in the material modification, thus achieving particularly high-quality material processing.

[0049] A particular advantage is that double dispersion achieved by a slight rotation or displacement of the scattering disk can produce a large difference in the local randomization of the intensity distribution.

[0050] The feed device can be configured to move the laser beam and the workpiece relative to each other by means of feeding, wherein the feed device comprises a scanner device and / or an axis device, wherein the scanner device preferably comprises an AOM and / or a galvanometer scanner and / or a polygon scanner.

[0051] "Displaceable relative to each other" means that the laser beam can be displaced translationally relative to the stationary material and the material can also be displaced relative to the laser beam, or both the material and the laser beam can be moved.

[0052] In particular, this allows the focal zone of the laser beam to be positioned at different locations on the material to introduce the laser pulses. In this case, the laser pulses are located, in particular, along a feed path. The feed path can be, for example, straight or curved. 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.

[0053] For example, when laser pulses are emitted into or onto a material, the laser beam can be moved along with the feed so that different focal zones can be arranged adjacent to one another or even overlap, enabling uniform and flat processing of the workpiece.

[0054] The feed device may preferably comprise an axis device and / or a scanner device.

[0055] For example, the axis arrangement can be used to mechanically move the material, while the scanner arrangement is used to move the laser beam over the material. In particular, the axis arrangement can be an XYZ stage with stepper motor control. However, the axis arrangement can also be configured with piezoelectric adjustment for the fastest possible adjustment. In particular, the scanner arrangement can be a galvanometer scanner. However, the feed arrangement can also be a roll-to-roll device.

[0056] In an acousto-optic deflector (AOD), an AC voltage is applied to a piezoelectric crystal in an optically adjacent material to generate an acoustic wave that periodically modulates the material's refractive index. The wave can propagate through the optical material, for example as a propagating wave or wave packet, or as 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 thereby deflected at least partially at an angle to its original beam propagation direction. The grating constant of the diffraction grating, and therefore the deflection angle, depends, among other things, on the wavelength of the acoustic wave and, therefore, the frequency of the applied AC voltage.

[0057] 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, which in turn alters the path of the laser beam through the prism.

[0058] Spatial statistical distribution using electro-optical and / or acousto-optic deflectors can be achieved at clock rates exceeding 1 MHz. Thus, laser pulses can be repositioned millions of times per second. In particular, electro-optical and / or acoustic deflectors can be used to reposition laser pulses with single-pulse precision, allowing each individual laser pulse to be introduced into a different location on the material.

[0059] In a galvanometer scanner, a rotating mirror is used to reposition the laser beam with high accuracy and repeatability. In particular, a one-dimensional galvanometer scanner deflects the laser beam in only one direction, while a two-dimensional galvanometer scanner deflects the laser beam in two different directions, which are preferably orthogonal to each other.

[0060] The feeding device can in particular change the position of the laser relative to the workpiece so that successively emitted laser pulses process the workpiece at different positions. Thus, the laser beam can cover the entire surface of the workpiece and thus perform surface material processing.

[0061] The material modifications produced on the workpiece can overlap.

[0062] By overlapping the material modifications, a continuous treated surface of the workpiece can be formed. This has the particular advantage that regular patterns, which are produced, for example, by a uniform deflection of the laser beam at the feed rate between two laser pulses, can be avoided.

[0063] In particular, it is also possible to process planar portions of a workpiece. It is also possible to process the entire surface of a workpiece.

[0064] A planar portion means that a continuous area having an extent corresponding to at least two focal zones has been processed, while full-surface treatment of the workpiece surface means that at least the side facing the laser beam has been processed.

[0065] The focusing optical device can have at least: a first lens with a first focal length and a second lens with a second focal length, wherein the first lens is arranged at a distance of the first focal length from the scattering disk, wherein the second lens is arranged at a distance of the second focal length from the workpiece, and wherein the first lens and the second lens are arranged at the following distance relative to each other: the distance corresponds to the sum of the focal lengths of the first lens and the second lens.

[0066] Overall, this positioning of the components creates a so-called 4f optical system, which allows any positional and angular deviations of the scattered light from the scattering disk, particularly the laser beam, to be transferred to a corresponding scattering plane. This allows, for example, the focal zone to be enlarged or reduced, allowing larger or smaller areas of the workpiece to be processed in the focal plane. In particular, by reducing the focal zone, the laser power can be concentrated on a smaller area, enabling material processing even with low-power laser systems. For example, the first and second lenses can have an aperture ratio of f100.

[0067] The focusing optics may comprise a cylindrical lens arranged to generate a linear focal zone on the workpiece. In particular, the first lens of the focusing optics may be a cylindrical lens arranged to generate a linear focal zone on the workpiece.

[0068] By including a cylindrical lens in the focusing optics, the focal zone of the laser beam can be stretched in one direction in the focal plane. For example, a cylindrical lens has an aperture ratio of f200 in one direction, but no focal length in the perpendicular direction. In particular, the cylindrical line can produce a linear focal zone in the focal plane. This also means that the energy of the laser beam is distributed in only one dimension, providing high power density or high intensity in the focal plane.

[0069] This enables adequate material processing even with low-power laser systems.

[0070] The beam shaping device can be configured to impart a beam shape, in particular a flat-top beam shape, to the laser beam, wherein the beam shaping device is preferably arranged upstream of the first scattering disk.

[0071] The beam shaping device can generate an elliptical geometry, a circular geometry or a rectangular geometry, in particular a square flat-top beam shape.

[0072] The beam shaping optics can be, for example, commercially available Pi-shaped beams, which impart a flat-top beam shape to the laser beam. In contrast to a Gaussian laser beam, a flat-top laser beam has a uniform intensity across the beam cross-section, with the intensity rapidly decreasing after reaching the beam diameter. In a sense, a flat-top laser beam has a substantially rectangular intensity profile, whereas a Gaussian laser beam has a Gaussian intensity profile.

[0073] A particularly simple beam shape is provided by a flat-top laser beam. For example, a flat-top laser beam makes it particularly easy to produce several adjacent material modifications that are adjacent to one another or partially overlap, since intensity variations at the edges of the Gaussian laser beam do not need to be compensated.

[0074] The above-mentioned object is also achieved by a method for processing materials having the features of claim 10. Advantageous further developments of the method can be found in the dependent claims, the present description and the figures.

[0075] Therefore, a method for processing a workpiece using laser pulses, in particular for applying an anti-glare functionalization, is proposed. The laser is in particular a short-pulse laser or an ultrashort-pulse laser, wherein a laser beam having the laser pulses is scattered by at least one scattering disk, wherein the scattered laser beam is focused by focusing optics onto a focal zone on a focal plane in or on the workpiece, wherein the workpiece is exposed to the laser beam and thus processed. According to the invention, a locally randomized intensity distribution is applied to the laser beam at the focal zone by the scattering disk.

[0076] At least two scattering disks can be moved relative to one another, wherein the locally randomized intensity distribution undergoes a corresponding randomized change.

[0077] The workpiece and the laser beam can be moved relative to each other along a feed trajectory.

[0078] The focal regions of different laser pulses, in particular consecutive laser pulses, can overlap.

[0079] The focal area can cover the surface section of the workpiece ( Abschnitt).

[0080] This allows particularly simple flat processing of the material.

[0081] Another aspect of the invention relates to a workpiece with anti-glare functionalization produced by the method.

[0082] The method can be used to produce a functionalized surface of a workpiece in such a way that it reduces direct reflection of light on the workpiece.

[0083] For example, direct reflection is the zeroth order of diffraction at the surface of the component. Direct reflection is suppressed if less than 90%, preferably less than 70%, particularly preferably less than 50% of the incident light is reflected at a certain reflection angle according to Snell's refraction law.

[0084] The sparkle of the surface with anti-glare functionalization can be less than 5%.

[0085] Sparkle describes the optical effect of a transparent component that visibly sparkles or shimmers when light is reflected from its surface or transmitted through it. The appearance depends significantly on the chosen angle of incidence and viewing angle of the light. Sparkle is therefore a measure of irregular intensity and color fluctuations.

[0086] The sparkle level can be quantified, for example, as the intensity modulation of the light by the flash, in particular as an intensity increase or intensity decrease under uniform illumination.

[0087] With the aid of anti-glare functionalization, this glare can be suppressed, and transmission and reflection can be homogenized.

[0088] Image clarity can exceed 70%.

[0089] Image Distinctness (DOI) describes image sharpness and quantifies the deviation from theoretical light propagation due to light scattering at material modifications. A high DOI specifically indicates high image sharpness. Light scattering at recessed areas affects both light reflection at the surface and light transmission through the surface. With low DOI, light scattering is high, while with high DOI, light scattering is low, resulting in high image sharpness. Therefore, DOI is inversely proportional to scattering or diffusion.

[0090] Scattering can exceed 22%.

[0091] Scattering is a measure of the scattering intensity of a material. Scattering also depends, among other things, on the shape and properties of the individual material modifications, so that the scattering can be adjusted via the beam shape of the laser beam and the size and depth of the material modification.

[0092] The transparent component may be a covering portion or a protective portion of the smart device.

[0093] In particular, the smart device may be an electronic device that is touch-sensitive and controllable by finger gestures, such as a smart watch, a smart phone, a tablet computer, or an image display device in a car, etc. Typically, the smart device includes a screen and a display.

[0094] However, it may also be the case that the transparent component is arranged on the rear side of the smart device and provides the rear side with a particularly high-quality and non-slip surface finish due to its matte surface and the roughness caused by the material modification. BRIEF DESCRIPTION OF THE DRAWINGS

[0095] 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:

[0096] Figure 1A 、 Figure 1B 、 Figure 1C and Figure 1D A schematic representation of the apparatus showing a first embodiment;

[0097] Figure 2A 、 Figure 2B 、 Figure 2C and Figure 2D a schematic representation showing a device of a second embodiment;

[0098] Figure 3A 、 Figure 3B 、 Figure 3C A schematic representation showing the operating principle of the beam shaping device;

[0099] Figure 4A 、 Figure 4B 、 Figure 4C 、 Figure 4D and Figure 4E a schematic representation showing a device of a third embodiment;

[0100] Figure 5A 、 Figure 5B and Figure 5C shows a schematic representation of a diffuser plate;

[0101] Figure 6A 、 Figure 6B and Figure 6C shows schematic representations of other diffuser panels; and

[0102] Figure 7A and Figure 7B A schematic representation of the method according to the invention is shown. DETAILED DESCRIPTION

[0103] Preferred exemplary embodiments are described below with reference to the accompanying drawings. In different drawings, identical, similar or elements having the same effect are provided with the same reference numerals, and repeated descriptions of these elements are omitted in some instances to avoid redundancy.

[0104] Figure 1A A device according to a first embodiment is schematically shown. The device comprises a laser 1, in particular a short-pulse laser or an ultrashort-pulse laser, which provides laser pulses 100 forming a laser beam 10. The laser beam 10 passes through a scattering disk 2, which scatters the laser beam 10, thereby forming a plurality of partial laser beams whose intensities and propagation directions are randomized by the scattering. A focusing optical system 3, which consists of a first lens 30, focuses the scattered laser beam 10 or the plurality of partial laser beams onto a focal region 120 on a focal plane 12, which, for example, coincides with the surface 40 of the workpiece 4. As a result, the focused and scattered laser beam 10 has a locally randomized intensity distribution on the focal plane 12, so that the surface 40 of the workpiece 4 is provided unevenly within the focal region 120, resulting in an uneven material modification.

[0105] The alignment of the focal plane 12 with respect to the surface 40 of the workpiece 4 is achieved, for example, by means of an axis system (not shown), by means of which the distance between the focusing lens 3 and the surface 40 can be adjusted. By varying the distance, a desired intensity can be set in the local maximum of the focal region 120 on the surface 40.

[0106] Figure 1B A scattering disk 2 is schematically shown. The scattering disk has various scattering areas arranged in a grid, for example, in a shape similar to rectangular pixels. White scattering areas do not produce any phase shift, while black scattering areas produce a 180° phase shift compared to the white scattering areas. Due to the randomized scattering areas, i.e., the random arrangement of scattering areas that produce or do not produce a phase shift, the laser beam 10 transmitted through the scattering disk 2 can be impressed with a randomized intensity distribution in the focal plane 12.

[0107] Figure 1C and Figure 1D This locally randomized intensity distribution is shown. Figure 1C shows the intensity distribution of the laser beam 10 on the focal plane 12 during the first passage through the scattering disk 2 at the first irradiation point, and Figure 1D Different intensity distributions are shown during another pass through the scattering disk 2 at a second irradiation point. The intensity distributions differ from one another and therefore produce different material modifications on the surface 40 of the workpiece 4. To produce different locally randomized intensity distributions in the focal plane 12, the scattering disk 2 can be rotated or shifted, for example, using an adjustment mechanism 2, so that the irradiation point of the laser beam 10 on the scattering disk 2 can be adjusted.

[0108] The intensity distribution has a coarse structure based on the shape of the pixel-shaped scattering area. For example, diffraction at a rectangular pixel produces a sinc superimposed by a randomized intensity gradient. 2 The randomized intensity curve reflects the influence of different scattering regions on the laser beam 10.

[0109] Figure 2A A further embodiment of the device according to the invention is shown. Figure 1A In contrast, the laser beam 10 is shaped by the beam shaping device 6. For example, a flat top beam is formed by the Gaussian laser beam of the laser, so that the envelope of the intensity distribution in the focal region 12 becomes uniform, see Figure 2C .

[0110] The device also includes two scattering plates 2, 2', through which the laser beam 10 sequentially passes. The laser beam 10 scattered by the first scattering plate 2 is further scattered by the second scattering plate 2'. To further randomize the scattering of the laser beam 10, the first scattering plate 2 and the second scattering plate 2' can be moved and / or rotated relative to each other using associated adjustment mechanisms 20, 20', as described in detail below. Consequently, different laser pulses 100 from the laser 1 experience different scattering, and the laser pulses sequentially introduced into the material of the workpiece 4 also result in different types of material modifications.

[0111] The scattered laser beam 10 is directed onto the focusing optical system 3, which includes a first lens 30 and a second lens 32. The first lens 30 is located at a distance f1 from the scattering disk 2', while the second lens 32 is spaced apart from the first lens by a distance equal to the sum of the first focal length f1 and the second focal length f2. The focal plane 12 is located behind the second lens 32 at a distance f2 in the direction of beam propagation and coincides with the surface 40 of the workpiece 4. Imaging 4f into the focal plane 12 allows the size of the scattered light from the scattering plate to be magnified or reduced.

[0112] The device may also include a scanner 50 configured as a galvanometer scanner or AOM. The second lens 32 generally transforms the laser beam 10 from angle to position, so that the laser beam 10 deflected in front of the second lens 32 is mapped to a different position on the focal plane 12 after the second lens 32. Therefore, it is particularly advantageous to position the scanner 50 that deflects the laser beam 10 at a distance of the second focal length f2 in front of the second lens 32. Thus, the angular deflection performed by the scanner is converted into a spatial deflection on the focal plane 12.

[0113] Figure 2BThe first intensity profile of a scattered laser beam 10 at focal plane 12 is shown. The intensity profile of a flattened laser beam 10 provides uniform illumination of a region, with the intensity distribution being strictly confined toward the edges of the region. The double scattering process produces a locally randomized intensity pattern in the surface, similar to laser speckle. For example, the locally randomized intensity distribution can show more than 100 local intensity maxima, resulting in highly inhomogeneous and irregular material modification.

[0114] Figure 2C Shown in a comparative manner Figure 1C (dashed line) and Figure 2B (solid line) is the envelope of the intensity distribution. It can be clearly seen that the sinc 2 The shaped intensity curve concentrates most of the intensity on a small spatial area, while the use of a flat-top laser beam significantly simplifies the surface processing of the workpiece 4.

[0115] Figure 2D The following shows a different intensity distribution generated when the first scattering disk 2 is rotated or displaced relative to the second scattering disk 2'. Since the first scattering disk scatters the laser beam 10 differently in the displaced or rotated position, different local randomized intensity curves are generated in the focal plane 12. This makes it possible to avoid repeated randomized intensity distributions on the surface 40 of the workpiece 4. Figure 2B 、 Figure 2D The diameter of the focal zone is about 1 mm, so that the power distribution of the laser is about 0.8 mm. 2 on the area.

[0116] Figure 3A The operating principle of the flat top beam former 6 is shown schematically. The laser beam 10 running on the optical axis and illuminating the beam shaping device 6 has a first diameter, which is, for example, 1 / e of the intensity maximum of the laser beam 10. 2 The intensity of the incident laser beam 10 decreases. In the beam shaping device 6, the laser beam 10 can be reshaped using a combination of a phase plate, a spherical lens, and an aspherical lens. For example, the portion of the laser beam that forms the maximum intensity of the incident laser beam 10 can be distributed away from the optical axis, so that although the maximum intensity is lower on the optical axis, a uniform intensity profile is present over a larger area. The portion of the laser beam can then be parallelized again to form a flattened laser beam 10'. The diameter of the flattened laser beam can be larger than that of a Gaussian laser beam.

[0117] Depending on the beam diameter of the incident laser beam 10, different beam shapes can be generated using the same beam shaping device 6, for example see Laskin et al., "Variable beam shaping with using the same fieldmapping refractive beam shaper", Laser Resonators, Microresonators, and Beam Control XIV, Vol. 8236, SPIE, 2012. Figure 3B In the example, the incident laser beam 10 has a Figure 3A This results in the formation of edge peaks in the intensity profile of the flat-top laser beam after the beam shaping device 6. Figure 3C In the example, the incident laser beam 10 has a Figure 3A Therefore, the flattened laser beam 10' has a lower edge steepness.

[0118] Figure 4A Another embodiment of the device is shown. Figure 2A In contrast, the first lens 30 of the focusing device 3 is a cylindrical lens. The cylindrical lens focuses the laser beam 10 in only one direction. Therefore, the area irradiated by the laser power is smaller than Figure 2A The irradiated area is reduced. As a result, the power is distributed over a smaller area, and the intensity in the focal plane becomes greater. This also enables the use of lower-performance laser systems for material processing.

[0119] in addition, Figure 4A There is also a first telescope 60 in front of the beam shaping device 6, and a second telescope 62 behind the beam shaping device 6. This structure is of course Figure 2A It is also possible.

[0120] The first telescope 62 may be configured to adjust the beam diameter of the incident laser beam 10 to the beam shaping device 6. Figure 3A 、 Figure 3B 、 Figure 3C As shown, the intensity distribution of the outgoing laser beam can be adjusted by adjusting the beam diameter in front of the beam shaping device 6.

[0121] The second telescope 62 can be configured to adjust the size of the illuminated area on the scattering disk 2. This means that in addition to the focusing optics 3, the size of the focal zone 120 on the workpiece can also be adjusted. The second telescope 62 can be implemented, for example, as a simple telescope with two lenses according to Galileo, or as a flexible telescope with three lenses and thus variable magnification and divergence matching.

[0122] Figure 4B and Figure 4C The scattering disks 2 and 2' are shown as phase plates. In particular, the phase plates have only a one-dimensional binary pattern, whereby the laser beam 10 is also scattered in only one direction. However, it is also possible that both phase plates or only one of the two phase plates has a pattern such as Figure 1B The two-dimensional pattern shown.

[0123] Figure 4D and Figure 4E Show how to use according to Figure 4A The intensity curve on the focal plane 12 is generated by the device. Figure 4D and Figure 4E Two different intensity curves are shown as they can be produced after a rotation or displacement of the scattering disk 2, 2'. Figure 4D and Figure 4E The focal zone through the cylindrical lens is only about 2 mm wide and 30 μm high. This distributes the laser power to only about 0.06 mm 2 Therefore, the power density or energy density of the cylindrical lens in the focal area is Figure 2B and Figure 2D More than 10 times of that.

[0124] In order to particularly easily randomize the intensity profile of the scattered laser beam 10 in the focal plane 12, the first scattering disk 2 and the second scattering disk 2' can be rotated relative to each other, for example, as shown in FIG. Figure 5A In particular, the two scattering disks 2, 2' can rotate at different rotational frequencies. It is also possible to rotate only one of the two scattering disks 2, 2'.

[0125] The device can also have three scattering discs 2, 2', 2", such as Figure 5B All three scattering discs can also be moved parallel to each other along different axes to achieve further randomization. In particular, the scattering discs can oscillate back and forth along different axes, preferably at different frequencies.

[0126] It is also possible to move one scattering disk and rotate the other scattering disk (not shown).

[0127] Figure 5C Another possible embodiment is shown in which both scattering disks 2 and 2' are reflective. For example, the laser beam 10 impinges on the first scattering disk 2 at a certain angle and is then reflected by the scattering disk 2' and thus scattered. This process is repeated several times until the scattered laser beam 10 is scattered by the second scattering disk 2' in the direction of the focusing device 3. The first scattering disk, the second scattering disk, or both scattering disks can have an adjustment mechanism 20 so that the laser beam 10 impinges on the respective scattering disks 2 and 2' at different points, thereby further randomizing the intensity distribution on the focal plane 12.

[0128] Figure 6A Another embodiment for further randomizing the intensity distribution is shown. An incident laser beam 10 is deflected by a first scanner 50 and directed through a first lens, a first scattering disk 2, a second scattering disk 2', and a second lens. The scattered laser beam is then further deflected by another scanner 50'. The first scanner 50 can direct the laser beam 10 to different areas on the scattering disks 2, 2'. A second scanner 50', which can be synchronized with the first scanner 50, can compensate for spatial offsets caused by the deflection.

[0129] Figure 6B Show Figure 6A The second half of the beam path can also be replaced by a mirror 52 which is arranged, for example, behind the first scattering disk 2 .

[0130] However, it is also possible to Figure 6C As shown, only one scanner 50 is arranged in front of the scattering disk 2 , and a telescope consisting of two lenses then images the scattered laser beam 10 .

[0131] Figure 7A A corresponding method for processing a workpiece 4 is shown. Here, a laser pulse 100 is emitted by a laser 1, forming a laser beam 10. The laser beam 10 is scattered by at least one scattering disk 2 and focused onto a surface 40 of a workpiece 4 by means of focusing optics 3. The laser beam 10 irradiates the workpiece 4 in a focal plane 12, thereby processing it. The intensity distribution of the laser beam is locally randomized in the focal plane 12, making it possible, for example, to functionalize the surface 40 of the workpiece 4, in particular to provide anti-glare functionalization.

[0132] The workpiece 4 is moved by the feed device 5 so that the focal zone 120 of the laser beam 10 successively covers the entire surface 40 of the workpiece 4 or a portion of the surface 40. The focal zones 120 of different laser pulses 100 can overlap. This means, in particular, that a first laser pulse 100 is introduced into a first focal zone 120 at a first position x in the material of the workpiece 4, while a second laser pulse 100 ′ is introduced into a second focal zone 120 ′ at a second position x′ in the material of the workpiece 4.

[0133] If different focal planes 12, 12' have different randomized intensity distributions, the scattering disks 2, 2' of the device can be rotated or displaced relative to one another. Thus, even with uniform feed, a uniform material modification is not produced on the surface 40 of the workpiece 4, thereby avoiding the formation of disturbing interference or diffraction patterns when observing the surface.

[0134] Figure 7BIt shows that different focal zones 120, 120' of laser pulses 100, 100', which are introduced successively at a time pulse interval t0, can overlap in order to achieve the most planar possible treatment of the workpiece 4. Between the laser pulses 100, 100', the scattering of the laser beam 10 can be varied by a corresponding relative movement of the scattering disks 2, 2' to achieve inhomogeneous material treatment.

[0135] At a laser repetition rate of 10 kHz and a focal zone diameter of 1 mm, feed speeds of up to 10 m / s are possible, allowing the surface of the workpiece to be processed very quickly.

[0136] Where applicable, all individual features presented in the exemplary embodiments may be combined with one another and / or interchanged without departing from the scope of the present invention.

[0137] Reference Signs List

[0138] 1 laser

[0139] 10 laser beams

[0140] 12 focal planes

[0141] 120 Focus Area

[0142] 100 laser pulses

[0143] 102 parts of laser beam

[0144] 2 scattering disks

[0145] 20 Adjustment mechanism

[0146] 3 Focusing optics

[0147] 30 first lens

[0148] 32 Second lens

[0149] 4 workpieces

[0150] 40 workpiece surface

[0151] 5 Feeding device

[0152] 50 Scanner Device

[0153] 52-axis system

[0154] 6 Beam shaping device

[0155] 60 First Telescope

[0156] 62 Second Telescope

[0157] V feed

Claims

1. A device for processing a workpiece (4) by means of laser pulses (100) of a laser (1), in particular for applying an anti-glare functionalization, comprising: A laser (1), in particular a short-pulse laser or an ultrashort-pulse laser, is arranged to provide a laser beam (10) having laser pulses (100), at least one scattering disk (2), the at least one scattering disk being arranged to scatter the laser beam (10), at least one focusing optical device (3) arranged to focus the laser beam (10) into a focal zone (120) on a focal plane (12) on the workpiece (4), wherein the workpiece (4) is subjected to the laser beam (10) and is thereby processed, It is characterized in that The scattering disk (2) is configured to impart a locally randomized intensity distribution to the laser beam (10) in the focal plane (12).

2. The device according to claim 1, characterized in that The at least one scattering disk (2) is configured to scatter the laser beam (10) in a transmission or reflection manner.

3. The device according to any one of the preceding claims, characterized in that The at least one scattering disk (2) has a phase pattern, in particular a binary phase pattern, which is configured to impart a position-dependent phase difference to the laser beam (10), in particular wherein the phase pattern is imparted in one or two dimensions.

4. The device according to any one of the preceding claims, characterized in that The scattering disk (2) is a spatial light modulator or a diffraction optical element.

5. The device according to any one of the preceding claims, characterized in that At least two scattering disks (2, 2') scatter the laser beam (10) in sequence, wherein the first scattering disk (2) is movable relative to the second scattering disk (2'), in particular, is rotatable or displaceable relative to the second scattering disk.

6. Device according to any one of the preceding claims, characterized in that A feed device (5) is arranged to move the laser beam (10) and the workpiece (4) relative to each other by means of a feed (V), wherein the feed device comprises a scanner device (50) and / or an axis system (52), wherein the scanner device preferably comprises an AOM and / or a galvanometer scanner and / or a polygon scanner.

7. The device according to any one of the preceding claims, characterized in that The focusing optical device (3) comprises at least a first lens (30) having a first focal length and a second lens (32) having a second focal length, wherein the first lens (30) is arranged at a distance of the first focal length from the scattering disk (2), wherein the second lens (32) is arranged at a distance of the second focal length relative to the workpiece (4), and The first lens (30) and the second lens (32) are arranged at a distance relative to each other: the distance corresponds to the sum of the focal lengths of the first lens (30) and the second lens (32).

8. The device according to any one of the preceding claims, characterized in that The focusing optical device (3) comprises a cylindrical lens, which is arranged to generate a linear focusing area (120) on the workpiece (4).

9. The device according to any one of the preceding claims, characterized in that A beam shaping device (6) is provided for imparting a beam shape, in particular a flat-top beam shape, to the laser beam (10), wherein the beam shaping device (6) is preferably arranged in front of the first scattering disk (2).

10. A method for processing a workpiece (4) by means of laser pulses (100) of a laser (1), in particular for applying an anti-glare functionalization, wherein the laser is in particular a short-pulse laser or an ultrashort-pulse laser, A laser beam (10) with the laser pulses is scattered by at least one scattering disk (2), wherein the scattered laser beam is focused by focusing optics (3) into a focal region (120) on a focal plane (12) on the workpiece (4), wherein the workpiece (4) is exposed to the laser beam (10) and thereby processed. It is characterized by: A locally randomized intensity distribution is imparted to the laser beam (10) in the focal plane (12) by the scattering disk (2).

11. The method according to claim 10, characterized in that At least two scattering disks (2, 2') are moved relative to one another, wherein the locally randomized intensity distribution undergoes a correspondingly randomized change.

12. The method according to claim 10, wherein: The workpiece (4) and the laser beam (10) are displaced relative to each other along a feed trajectory.

13. The method according to claim 10, wherein The focal regions (120) of different laser pulses (100) overlap, in particular the focal regions (120) of consecutive laser pulses overlap.

14. Method according to one of claims 10 to 13, characterized in that The focusing region (120) covers a planar section of the workpiece (4).

15. A workpiece (4) having an anti-glare functionalization produced by the method according to one of claims 10 to 14, wherein The direct reflection of light on the workpiece is less than 50%, and / or the sparkle of the surface with the anti-glare functionalization is less than 5%, and / or the clarity of the image is greater than 70%, and / or the scattering is greater than 22%.

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