EP4041479A1

EP4041479A1 - Laser device for generating laser radiation and 3d printing device comprising a laser device of this type

Info

Publication number: EP4041479A1
Application number: EP20790224.8A
Authority: EP
Inventors: Aliaksei KRASNABERSKI; Stephan Schneider
Original assignee: Limo GmbH
Current assignee: Limo GmbH
Priority date: 2019-10-07
Filing date: 2020-10-06
Publication date: 2022-08-17
Also published as: US20240066630A1; JP2022551621A; WO2021069441A1; CN114631047A; KR20220044570A

Abstract

The invention relates to a laser device for generating laser radiation, which has an intensity distribution with a plurality of intensity maximums in a working plane (11), comprising a laser light source (1) that emits laser radiation (2) during operation of the laser device, forming a linear or planar intensity distribution (6) with a plurality of intensity maximums (7) in a first plane (5), wherein the intensity maximums (7) are at east partially at a first distance (d1) from one another in at least one transverse direction, which is perpendicular to the propagation direction of the laser radiation (2), as well as comprising a projection device (8) that projects the first plane (5) into the working plane (11) in such a way that a linear or planar intensity distribution (6') with a plurality of intensity maximums (7') is produced in the working plane (11).

Description

"Laser device for generating laser radiation as well as 3D printing device with such a laser device"

The present invention relates to a laser device for generating laser radiation, which has an intensity distribution with a plurality of intensity maxima in a working plane, as well as a 3D printing device with such a laser device.

Definitions: In the direction of propagation of the laser radiation, mean means the direction of propagation of the laser radiation, especially if this is not a plane wave or is at least partially divergent.

Unless expressly stated otherwise, a laser beam, light beam, partial beam or beam does not mean an idealized beam of geometrical optics, but a real light beam, such as a laser beam with a Gaussian profile or a modified Gaussian profile that is not infinitesimal has a small, but an extended beam cross-section. The M-profile denotes an intensity profile of laser radiation, the cross-section of which has a lower intensity in the middle than in one or more extra-central areas. With top hat distribution or top hat intensity distribution or top hat profile is one

Intensity distribution meant, which at least one direction can essentially be described by a rectangular function (rect (x)). Real intensity distributions that deviate from a rectangular function in the percentage range or have sloping edges are also to be referred to as top hat distribution or top hat profile.

A laser device of the type mentioned at the beginning and a 3D printing device of the type mentioned at the beginning are known, for example, from WO 2015/134075 A2. With the one described therein A 3D printing device uses a plurality of semiconductor lasers, the light of which is coupled into a plurality of optical fibers. The laser radiation emerging from the optical fibers is used for the targeted application of a starting material for 3D printing, which is arranged in a work area of the 3D printing device.

A disadvantage of laser devices known from the prior art and 3D printing devices with optical fibers from which the laser radiation required for 3D printing emerges is that, as a rule, only a small working distance can be achieved. This can damage or contaminate the optics used. Furthermore, there are gaps between the individual pixels used for 3D printing because the gaps between the cores of the optical fibers are comparatively large and the sheaths of adjacent optical fibers are arranged between the cores. Furthermore, the pixel size is often too large, so that a good resolution cannot be achieved.

The problem on which the present invention is based is to create a laser device of the type mentioned above and a 3D printing device of the type mentioned above, which allow a smaller pixel size in the working plane and / or a larger working distance.

According to the invention, this is achieved by a laser device of the type mentioned at the beginning with the features of claim 1 and by a 3D printing device of the type mentioned at the beginning with the features of claim 28. The subclaims relate to preferred embodiments of the invention. According to claim 1, it is provided that the laser device comprises a laser light source which, when the laser device is in operation, emits laser radiation that forms a linear or planar intensity distribution with a plurality of intensity maxima in a first plane, the intensity maxima in at least one transverse direction , which is perpendicular to the central direction of propagation of the laser radiation, at least partially have a first distance from one another, the laser device further comprising a projection device which maps the first plane into the working plane in such a way that a linear or planar intensity distribution with a plurality of intensity maxima is formed.

In particular, the intensity maxima of the intensity distribution in the first plane in at least one transverse direction, which is perpendicular to the direction of propagation of the laser radiation, can at least partially have a first distance from one another, the projection device being able to map the first plane into the working plane so reduced that the intensity maxima the intensity distribution in the working plane in at least one transverse direction, which is perpendicular to the direction of propagation of the laser radiation, at least partially have a second distance from one another which is smaller than the first distance. The intensity maxima in the working plane can all have the second distance from one another in the at least one transverse direction. Furthermore, the reduction achieved by the projection device can be between 1 and 20.

As a result of the reduction, the size of the intensity maxima or the pixel size in the working plane can be significantly reduced. Also the distances between the individual Intensity maxima can thereby be reduced. In particular, the gaps between the intensity maxima can be filled accordingly. For example, the pixel size can be significantly smaller than 100 μm or even smaller than the diameter of the cores of the optical fibers. It can be provided that the working distance between the projection device and the working plane is greater than 50 mm, in particular greater than 100 mm, preferably equal to or greater than 200 mm. In particular, a reducing projection device increases the working distance accordingly, so that, for example, distances of more than 200 mm can be achieved. In this way, damage to or contamination of the optics used can be avoided. Furthermore, there is an increased depth of field in the working plane.

Alternatively, it can be provided that the intensity maxima of the intensity distribution in the first plane in at least one transverse direction, which is perpendicular to the direction of propagation of the laser radiation, are at least partially at a first distance from one another, the projection device being able to map the first plane into the working plane in this way, that the intensity maxima of the intensity distribution in the working plane in at least one transverse direction, which is perpendicular to the direction of propagation of the laser radiation, at least partially have a second distance from one another, which is greater than the first distance or which is equal to the first distance. The projection device can achieve a magnification between 1 and 5 or a magnification of 1, for example.

It can be provided that the projection device is a telecentric projection device, in particular a projection device that is telecentric on both sides. Through a telecentric Projection device, uniform angular distributions of the laser radiation can be achieved in the working plane. In 3D printing, the even angular distributions lead to even temperature distributions of the raw material to be heated. Compared to a non-telecentric projection device, a telecentric projection device has a greater depth of field and less distortion.

There is the possibility that at least one component of the projection device is cylindrical in shape. Alternatively or additionally, at least one component of the projection device can be cylindrical or spherical or aspherical in shape. Furthermore, it can be provided that at least one component of the projection device is a microlens array. It can be provided that the at least one microlens array is a refractive, reflective or holographic optical element or an optical element with a continuous surface or a binary or multi-stage diffractive optical element. There is the possibility that the laser light source comprises at least one fiber laser. Alternatively, other laser light sources such as laser diode bars or the like can also be provided.

It can be provided that the laser light source comprises a plurality of optical fibers, from the ends of which a partial radiation of the laser radiation emerges, the optical fibers being in particular single-mode fibers or large-mode area fibers or few-mode fibers. The diffraction index M ^{2 of} such light sources can especially for use with a converter, smaller than 2, preferably smaller than 1.5.

The laser light source can have a holder with a plurality of grooves, in particular V-shaped grooves, each of the optical fibers being arranged in one of the grooves. Through the

Mounted in V-grooves, the optical fibers can be precisely positioned with respect to one another. As a result, a very constant overlap of the individual intensity maxima of, for example, only 1 pm can be realized in the working plane. In order to improve the accuracy of the positioning, the part of the holder that has the V-grooves can be formed in one piece.

Alternatively, it can be provided that a one-dimensional or two-dimensional array of optical fibers is formed in that the optical fibers or their ends are connected directly, for example by gluing and / or splicing, to an optical component or to a window, in particular wherein the Connection of the optical fibers with the optical component or the window a, preferably one-piece, optical component is created. The optical component can be the first optical component arranged behind the laser light source in the direction of propagation of the laser radiation. The window can be part of a fiber holder or fiber carrier, for example.

There is the possibility that the intensity maxima generated in the first plane are each formed by the partial radiation exiting from one of the optical fibers. Suitable optics can be provided in order to focus the partial radiation in the first plane. It can be provided that the partial radiations in the individual optical fibers have a mode profile which corresponds to a Bessel profile or a Gaussian profile or an M profile or a top hat profile. Furthermore, the intensity maxima in the working plane can each have a Gaussian or a super Gaussian or a top hat profile or an M profile or a process-optimized profile. In particular, any profile can be generated in the working plane that can deviate from the named profiles. The profile of the intensity distributions can preferably be changed as a function of the materials to be processed.

There is the possibility that the laser device comprises at least one converter which can change the intensity profile of the laser radiation or one or more of the partial radiations, wherein the converter can, for example, convert a Gaussian profile into a top-hat profile.

It can be provided that the at least one converter is designed as a 2D Gaussian to Airy disc functions converter, in particular as an axially symmetrical binary phase plate, or that the at least one converter is designed as a 1 D Gaussian to Sinc -Function converter is designed, in particular as two cylindrical binary phase plates, which are aligned perpendicular to each other.

In particular, a plurality of converters can be provided, which are arranged in a one-dimensional or a two-dimensional array. Such an array of converters could be arranged between the laser light source and the projection device. It can be provided that the at least one converter is integrated into the projection device. In this case, a single converter could be used instead of an array of converters. There is a possibility that the intensity maxima in the

Working plane each have a circular or a square or a hexagonal outline. For example, square outlines are advantageous because gaps can be avoided between them. By changing the shape of the pixels in the working plane, an adaptation to the materials to be processed can be made.

It can be provided that the laser device comprises at least one collimation element, in particular a plurality of collimation elements, for collimation of the laser radiation emerging from the laser light source. The plurality of collimation elements can be arranged in a one-dimensional or a two-dimensional array, which is in particular a lens array. The collimation elements can reduce the divergence of the laser radiation. If the collimation elements are designed as crossed cylindrical lenses, spaces between individual partial beams can be reduced.

There is the possibility that the plurality of intensity maxima in the working plane can be switched on or off individually or in groups, in particular by appropriate control of the laser light source. This results in individually addressable pixels in the working plane for 3D printing. In particular, the individual pixels or intensity maxima in the working plane can have up to several 100 W of power per pixel. With a laser device according to the invention, linear or planar intensity distributions can be generated in the working plane.

It can be provided that the laser device comprises means for superimposing individual partial radiations emanating from the laser light source into individual pixels in the first plane and / or that the laser device comprises means for dividing individual or all partial radiations emanating from the laser light source into several pixels in the first level .

The superposition can take place, for example, in a geometrical or optical manner. Alternatively, a superposition can also be achieved via polarization couplers or wavelength couplers. The superposition of several partial beams to form a pixel can be advantageous, for example, to enable power scaling or to reduce the loads on critical optical elements or to have one or more reserve channels if individual channels fail.

The division of partial radiation into a plurality of pixels can be advantageous, for example, in the case of parallel processing.

There is the possibility that the laser device comprises at least one Fourier lens and / or at least one array of Fourier lenses, which are arranged in particular between the laser light source and the first plane. The at least one Fourier lens and / or the at least one array of Fourier lenses can serve, for example, as a means for superimposing individual partial radiations emanating from the laser light source into individual pixels in the first plane. It can be provided that several subsystems of the laser device, which for example generate several laser lines consisting of pixels, can be operated in parallel.

According to claim 28 it is provided that the laser device is a laser device according to the invention. An inventive

Laser device represents an industrially very attractive solution with which, in particular, 3D printing can be carried out with metallic starting materials.

The working plane of the laser device can correspond to the working area of the 3D printing device. The scanning device can be designed such that the laser radiation is moved relative to the work area or the work area is moved relative to the laser radiation.

In particular, the laser radiation generated by the laser device can be deflected by the scanning device as a whole, the scanning device being designed, for example, as a galvano scanner. This is possible in particular because of the good beam quality that can be generated with the laser device according to the invention, the large working distance and the large depth of field in the working plane.

There is therefore no need to deflect each individual partial radiation with, for example, a single mirror. Further features and advantages of the present invention will become clear on the basis of the following description of preferred exemplary embodiments with reference to the accompanying figures. 1 shows a schematic side view of a first embodiment of a laser device according to the invention;

2a shows a first intensity distribution of a laser radiation generated with a laser device according to the invention in a working plane;

2b shows a second intensity distribution of a laser radiation generated in a working plane with a laser device according to the invention;

3a shows a third intensity distribution of a laser radiation generated in a working plane with a laser device according to the invention;

3b shows a fourth intensity distribution of a laser radiation generated in a working plane with a laser device according to the invention;

4 shows a fifth intensity distribution of a laser radiation generated in a working plane with a laser device according to the invention;

5 shows a schematic side view of a second embodiment of a laser device according to the invention; 6 shows a schematic side view of a third embodiment of a laser device according to the invention;

7a shows a sixth intensity distribution of a laser radiation generated with a laser device according to the invention in a working plane;

FIG. 7b shows a diagram which illustrates the sixth intensity distribution according to FIG. 7a; FIG.

7c shows a seventh intensity distribution of a laser radiation generated in a working plane with a laser device according to the invention;

7d shows a diagram which illustrates the seventh intensity distribution according to FIG. 7c;

8 shows a schematic side view of a fourth embodiment of a laser device according to the invention;

9 shows a schematic side view of a fifth embodiment of a laser device according to the invention;

10 shows a schematic side view of a sixth embodiment of a laser device according to the invention;

1 1 shows a schematic side view of a seventh embodiment of a laser device according to the invention; 12 shows a schematic side view of an eighth embodiment of a laser device according to the invention;

13 shows a schematic side view of a ninth embodiment of a laser device according to the invention;

14 shows a schematic side view of a tenth embodiment of a laser device according to the invention;

15 shows a schematic side view of an eleventh embodiment of a laser device according to the invention;

16 shows an eighth intensity distribution of a laser radiation generated in a working plane with a laser device according to the invention;

17 shows a schematic side view of a twelfth embodiment of a laser device according to the invention;

18 shows a schematic side view of a detail of a first embodiment of a 3D printing device according to the invention;

19 shows a schematic side view of a detail of a second embodiment of a 3D printing device according to the invention; 20 shows a schematic side view of a detail of a third embodiment of a 3D printing device according to the invention;

21 a shows a schematic side view of a first embodiment of a projection device of a laser device according to the invention, with some exemplary beams of a laser radiation moving through the projection device being shown;

FIG. 21 b shows a schematic side view of the projection device according to FIG. 21 a, in which the laser radiation moving through the projection device is shown; FIG.

21c shows a schematic side view, rotated by 90 °, of the projection device according to FIG. 21a, in which the laser radiation moving through the projection device is shown;

22a is a schematic side view of a second

Embodiment of a projection device of a laser device according to the invention, some exemplary beams of a laser radiation moving through the projection device being shown;

22b shows a schematic side view of the projection device according to FIG. 22a, in which the

Laser radiation moving through the projection device is shown; 22c shows a schematic side view, rotated by 90 °, of the projection device according to FIG. 22a, in which the laser radiation moving through the projection device is shown; 23a is a schematic side view of a third one

23b shows a schematic side view of the projection device according to FIG. 23a, in which the laser radiation moving through the projection device is shown; 23c is a schematic side view of FIG

Projection device according to FIG. 23a, in which the laser radiation moving through the projection device is shown;

24 shows a schematic side view of a detail of a thirteenth embodiment of a laser device according to the invention.

Identical or functionally identical parts are provided with the same reference symbols in the figures. A Cartesian coordinate system is drawn in some of the figures.

The first embodiment of a laser device according to the invention depicted in FIG. 1 comprises a laser light source 1 for generating one that is only indicated schematically in FIG. 1 Laser radiation 2. The laser light source 1 is designed in particular as an array of lasers, preferably as an array of fiber lasers with a plurality of optical fibers 3, from each of which a partial radiation of the laser radiation 2 emerges. The continuous wave output power of the laser light source 1 can be between 1 W and 1000 W, for example. The wavelength of the laser radiation 2 emitted by the laser light source 1 can be, for example, 1080 nm.

Alternatively, it can also be provided that, instead of a plurality of fiber lasers, a plurality of other lasers such as a laser diode bar with a plurality of emitters are provided, the light of which is each coupled into an optical fiber.

In the exemplary embodiment shown, the optical fibers 3 are arranged next to one another in a direction which corresponds to the vertical direction in FIG. 1. This results in a one-dimensional array of optical fibers 3, from the ends of which one of the partial radiation emerges. The distance between the centers of the optical fibers can be between 20 μm and several millimeters.

Alternatively, it can be provided that the optical fibers 3 are not arranged next to one another in one direction but rather are arranged next to one another in two directions, in particular perpendicular to one another. In this case, there is a two-dimensional array of optical fibers 3, each of which has one of the ends

Partial radiation escapes. Here, too, the center-to-center spacing of the optical fibers can be between 20 μm and several millimeters. The laser light source 1 comprises, in particular, a holder (not shown) with a plurality of V-shaped grooves which are arranged equidistant from one another. Each of the optical fibers 3 is arranged in one of the grooves. The holder can in particular consist of silicone or glass.

The optical fibers 3 can be positioned precisely with respect to one another by means of this holder in V-grooves. In order to improve the accuracy of the positioning, the part of the holder that has the V-grooves can be formed in one piece. Alternatively, there is the possibility of forming a one-dimensional or two-dimensional array of optical fibers by connecting the optical fibers or their ends directly to an optical component, for example by gluing and / or splicing. The optical component can be the first in the direction of propagation

Acting laser radiation behind the laser light source arranged optical component. Alternatively, the optical fibers can also be connected to a window that is part of a fiber holder or fiber carrier, for example. In particular, by connecting the optical fibers to the optical component or the window, a preferably one-piece optical component can be created.

The diameter of the core 4 of the optical fibers 3 indicated in FIG. 1 can be between a few μm and 100 μm or more. The mode profile of the laser radiation in each of the optical fibers 3 can be a Bessel profile or a Gaussian profile or a quasi-Gaussian profile or an M profile. The laser radiation 2 emerging from the fiber ends forms in a first plane 5 an intensity distribution 6, indicated schematically in FIG. 1, which has a plurality of intensity maxima 7 spaced apart from one another. The intensity maxima 7 can each have a Gaussian profile, for example. Each of these intensity maxima 7 is formed by one of the partial radiations which emerge from one of the ends of the optical fibers 3. The half width (FWHM) of the individual intensity maxima 7 can be between 10 pm and more than 1 mm. The first distance di of these intensity maxima 7 from one another is indicated in FIG. 1.

The laser device further comprises a projection device 8, which is indicated in FIG. 1 only by a rectangle. The projection device 8 is in particular a telecentric, preferably a double-sided telecentric projection device.

The numerical aperture of the projection device 8 can be between 0.001 and 0.1 or more.

The projection device 8 can comprise at least one refractive component and / or at least one diffractive component and / or at least one reflective component. There is the possibility that at least one component of the projection device is cylindrical or spherical or aspherical in shape. It can be provided that at least one component of the projection device 8 is a microlens array. The at least one microlens array can be a refractive, reflective or holographic optical element or an optical element with a continuous surface or a binary or multi-stage diffractive optical element. The projection device 8 can comprise at least one component which is used to correct chromatic aberration. The projection device 8 can have a zoom function in order to adapt the size of pixels in the working plane or line sizes. The projection device 8 can at least one of the folding of the

Include component serving the beam path, such as a mirror, for example, in order to reduce the length of the projection device. In order to project laser radiation with powers of, for example, more than 10 kW, the projection device 8 can comprise at least one component with a cooling function.

Examples of complexly structured projection devices can be found in DE 198 184 44 A1 and US Pat. No. 6,560,031 B1.

The first embodiment of a projection device 8 depicted in FIG. 1 maps the first plane 5 into the working plane 11. The projection device 8 performs a scaled-down

Figure by. The intensity distribution 6 ‘of the laser radiation 2 in the working plane 1 1 is thereby compressed compared to the intensity distribution 6 in the first plane 5. The second distance d2 of the intensity maxima 7 ‘from one another in the working plane 11 is smaller than the first distance di of the intensity maxima 7 in the first plane 5. The reduction in size of the projection device 8 can be between 1 and 20, for example.

The projection device 8 further increases the working distance of the working plane 11 from the laser device. The size of the intensity maxima 7 'in the working plane 11 can also be influenced by selecting a working plane that is spaced apart from the working plane 11 and into which a plane adjacent to the first plane is mapped. In Fig. 1 are examples of this two planes 5 ', 5 "adjacent to the first plane 5 and two planes 1 1", 1 1' adjacent to the working plane 1 1 are shown.

The intensity maxima 7 'of the laser radiation generated in the working plane 11 can be viewed as pixels of a laser radiation that is used for a 3D printing device for generating a spatially extended product. For this purpose, the working plane 11 can be arranged in a working area of a 3D printing device, with the starting material for 3D printing to be applied to the laser radiation being able to be supplied to the working area.

Due to the residual divergence of the partial radiation, the extent of the partial radiation changes slightly from plane 5 to plane 5 ″. Since a telecentric projection device 8, in contrast to a non-telecentric projection device, has a large depth of field due to the same magnification factor for the

Levels 1 1 to 1 1 ", the second distance d2 for the levels 1 1 to 1 1" is more or less the same, whereas the size of the individual partial beams in the levels 1 1 to 1 1 "due to the residual divergence as for the Levels 5 to 5 "are slightly different from each other.

This is an important advantage for material processing, because an optimal pixel size is determined not only by the optical pixel size and / or the intensity profile, but also by the physical properties of the materials to be processed, such as the thermal conductivity and the density of the material to be processed. The size of the partial radiation or the pixels can be adapted by simply changing from one level 1 1 to another level 1 1 ', 1 1 ". This can be, for example, a change from a level 1 1, 1 1', 1 1 " with the best homogeneity of the line intensity to another level 1 1,

1 1 ‘, 1 1“, in which the size of the partial radiation or the pixels is different, for example in which the size of the partial radiation or the pixel is smaller than the distance d2.

The individual intensity maxima 7 ‘or pixels of the laser radiation 2 used for 3D printing can be switched on and off in a targeted manner. This switching on or off of the pixels can in particular be achieved by appropriate control of the laser light source 1. For example, some of the

Fiber lasers can be switched on or off.

The cross section of the intensity maxima 7 ‘or of the pixels is circular in the embodiment according to FIG. 1. The cross section is indicated in FIG. 1 by the circles 12 arranged next to one another.

2a shows a linear intensity distribution 6 6 of the laser radiation 2 in the working plane 1 1 in a state in which all pixels or intensity maxima 7 ‘are present. In contrast, Fig. 2b shows the intensity distribution 6 ‘in a state in which every second pixel is switched off.

FIGS. 3a and 3b show a similar comparison for a laser device which generates a planar intensity distribution 6 ′ in the working plane 11. The individual pixels or intensity maxima 7 'are arranged next to one another in two mutually perpendicular directions which lie in the plane of the drawing. 3a shows the intensity distribution 6 'of the laser radiation 2 in the working plane 11 in a state in which all pixels or intensity maxima 7' are present are. In contrast, FIG. 3b shows the intensity distribution 6 'in a state in which every second pixel is switched off.

Fig. 4 shows a planar intensity distribution 6 ‘in the working plane 1 1, in which the pixels or intensity maxima 7 sind are hexagonally densely packed.

The embodiment shown in FIG. 5 essentially corresponds to that in FIG. 1. In contrast to this, the embodiment according to FIG. 5 comprises a schematically indicated additional array 13 of optical elements 14 between the laser light source 1 and the projection device 8. The optical elements 14 can be collimation lenses in order to collimate the laser radiation 2 emerging from the laser light source 1. As an alternative or in addition, the optical elements 14 can also be imaging elements or telescopic elements in order to enlarge the depth of field of a focal plane generated in the first plane 5. The optical elements 14 can, for example, map the fiber ends into the first plane 5. The optical elements 14 can be cylindrical or spherical in shape.

It is possible to provide two or more than two arrays 13 of optical elements 14 instead of one array 13 of optical elements 14. When using two arrays 13, the optical elements 14 of the two arrays 13 can, for example, be cylindrical lenses that are crossed with respect to one another.

The embodiment shown in FIG. 6 essentially corresponds to that in FIG

Embodiment according to FIG. 6 an additional array 15 of converters 16 and an additional array 17 of Fourier lenses 18. The converters 16, together with the Fourier lenses 18, can Change the intensity profile of the laser radiation 2 or one or more of the partial radiations, each of the converters 16 being able to convert, for example, a Gaussian profile into a top-hat profile. Alternatively, each of the converters 16 can convert a Gaussian profile into an M profile, for example.

A converter can be provided which is designed as a 2D Gaussian to Airy disc functions converter. An Airy disc function corresponds to ~ Ji (r) / r, where Ji is a Bessel function of the first type. Such Airy disc functions are described, for example, in US Pat. No. 9,285,593 B1. An example of a 2D Gaussian to Airy Disc

Functions converter is an axially symmetric binary phase plate. Such a phase plate is described in US Pat. No. 5,300,756.

A converter can also be provided which is designed as a 1 D Gaussian-to-Sinc function converter. A sinc function corresponds to 5ίh (pc) / pc. An example of a 1 D Gaussian-to-Sinc function converter are two cylindrical binary phase plates which are aligned perpendicular to one another.

Such a converter, for example a 2D converter or two 1 D plates aligned perpendicularly to one another, is used together with a Fourier lens as a Gaussian-to-Tophat converter or a Gaussian-to-M-shape converter.

It is entirely possible to provide more than one array 13 of optical elements 14 and / or more than one array 15 of converters 16 and / or more than one array 17 of Fourier lenses 18. 6 indicates schematically that the intensity maxima 7 in the first plane 5 and the intensity maxima 7 'in the working plane 11 have a top hat shape.

7a and 7b show a linear intensity distribution 6 of the laser radiation 2 in the working plane 11 in a state in which all pixels or intensity maxima 7 ‘are present. In contrast, FIGS. 7c and 7d show the intensity distribution 6 ‘in a state in which every second pixel is switched off. This makes it clear that the intensity maxima 7 ‘in FIG. 7d have a top-hat profile.

The embodiment shown in FIG. 8 essentially corresponds to that in FIG. 6. In contrast to this, the embodiment according to FIG. 8 comprises only one array 13 of optical elements 14, which can be designed as collimation lenses, for example, and an additional array 15 of converters 16, the Fourier lenses being integrated into this array 15.

The embodiment shown in FIG. 9 essentially corresponds to that in FIG. 8. In contrast to this, the embodiment according to FIG. 9 comprises only one array 13 of optical elements 14, which can be designed as collimation lenses, for example, the converter and the Fourier lenses in this array 15 are integrated.

The embodiment shown in FIG. 10 corresponds essentially to that in FIG. 6. In contrast to this, in the embodiment according to FIG. 10, the cross section is

Intensity maxima 7 'or the pixels are square. The cross section is indicated in FIG. 10 by the squares 19 arranged next to one another. A square cross section of the Intensity maxima 7 'can be achieved, for example, by using crossed cylinder lenses instead of spherical or aspherical circular lenses. This can be the lenses of the arrays 13, 17. The embodiment shown in Fig. 1 1 corresponds to

Essentially that in FIG. 8. In contrast to this, in the embodiment according to FIG. 11, the cross section of the intensity maxima 7 or of the pixels is square. The cross section is indicated in FIG. 11 by the squares 19 arranged next to one another.

The embodiment shown in FIG. 12 essentially corresponds to that in FIG. 9. In contrast to this, in the embodiment according to FIG. 12, the cross section of the intensity maxima 7 ‘or of the pixels is square. The cross section is indicated in FIG. 12 by the squares 19 arranged next to one another.

There is definitely the possibility of providing a hexagonal cross section instead of a circular or a square cross section for the intensity distributions 7. In the embodiment of FIG. 13 is within the

Projection device 8, a converter 20 is provided, which can change the intensity profile 6 of all partial radiations of the laser radiation 2. The converter 20 can, for example, convert a Gaussian profile into a top hat profile or a Gaussian profile into an M profile. In the specific embodiment, the intensity maxima 7 in the first plane 5 have a Gaussian profile and the intensity maxima 7 ′ in the working plane 11 have a top-hat profile. The converter 20 can be designed as a 2D Gaussian to Airy disc functions converter. An example of a 2D Gaussian to Airy disc functions converter is an axially symmetric binary phase plate. The converter 20 can also be designed as a 1 D Gaussian-to-Sinc function converter. An example of a 1 D Gaussian-to-Sinc function

Converters are two cylindrical binary phase plates that are aligned perpendicular to each other. In both cases, the second half of the projection lens 8, which is arranged behind the converter 20, can serve as a Fourier lens. However, a different Fourier lens can alternatively be provided.

The converter 20 is arranged in the projection device 8 at a location at which aperture diaphragms are usually provided.

The embodiment shown in FIG. 14 essentially corresponds to that in FIG. 13. In contrast to this, the embodiment according to FIG. 14 comprises a schematically indicated additional array 13 of optical elements 14 between the laser light source 1 and the projection device 8. The optical elements 14 can Be collimation lenses in order to collimate the laser radiation 2 emerging from the laser light source 1. As an alternative or in addition, the optical elements 14 can also be imaging elements or telescopic elements in order to enlarge the depth of field of a focal plane generated in the first plane 5. The optical elements 14 can, for example, map the fiber ends into the first plane 5. The optical elements 14 can be cylindrical or spherical in shape.

It is possible to provide two arrays 13 of optical elements 14 instead of one array 13 of optical elements 14. The embodiment shown in FIG. 15 essentially corresponds to that in FIG. 13. In contrast to this, in the embodiment according to FIG. 15, the cross section of the intensity maxima 7 ′ or of the pixels is square. The cross section is indicated in FIG. 15 by the squares 19 arranged next to one another.

FIG. 16 shows a planar or rectangular intensity distribution 6 ‘of the laser radiation 2 in the working plane 11 that can be generated by the laser device according to FIG. 15. For example, it can have 5 by 150 pixels with a top hat profile and a

Diameters of more than 100 μm can be provided. In the state shown in FIG. 16, every second pixel or intensity maximum 7 is switched off.

The embodiment shown in FIG. 17 essentially corresponds to that in FIG. 14. In contrast to this, in the embodiment according to FIG. 17, the cross section of the intensity maxima 7 ′ or of the pixels is square. The cross section is indicated in FIG. 17 by the squares 19 arranged next to one another. In the embodiment of a 3D printing device shown in FIG. 18, a scanning device 21, indicated only schematically, is provided in addition to a laser device, with which the laser radiation 2 can be moved in the working plane 11. The scanning device 21 can be designed, for example, as a polygon scanner or as a galvanometer scanner. In the exemplary embodiment shown in FIG. 18, the scanning device 21 is arranged between the projection device 8 and the working plane 11. The working plane 11 of the laser device can correspond to a working area of the 3D printing device to which the starting material for the 3D printing to be acted upon with the laser radiation 2 can be supplied. In the laser device according to FIG. 18, all of the in FIGS.

1, 5, 6, 8 to 15 and 17 are indicated. There are therefore both the arrays 13, 15, 17 in front of the projection device 8 and a common converter 20 in the projection device 8. Furthermore, both circles 12 and squares 19 are indicated as possible cross-sectional shapes of the pixels in the working plane 11. Furthermore, both intensity maxima 7 einem with a Gaussian profile and intensity maxima 7 with a top hat profile are indicated in the working plane.

It should be noted that these are alternatives that cannot or should not all be implemented simultaneously or in one structure. Rather, with reference to FIGS. 1, 5, 6, 8 to 15 and FIG.

17 can be integrated into the 3D printing device according to FIG. 18. The embodiment shown in FIG. 19 corresponds to FIG

Essentially that in Fig. 18. In contrast to this, in the embodiment according to Fig. 19, the scanning device 21 is arranged in the projection device 8, in particular between a first part 9 and a second part 10 of the projection device 8. The common converter 20 is between the

Scanning device 21 and the second part 10 are provided. The two parts 9, 10 can form a Fourier transforming device. The first part 9 can, for example, have a zoom function to have. Furthermore, the second part 10 can serve, for example, as an F-theta lens or as a flat field lens.

The embodiment shown in FIG. 20 corresponds essentially to that in FIG. 19. In contrast to this, in the embodiment according to FIG

Projection device 8 arranged, wherein the scanning device 21 can nevertheless be arranged in particular between two schematically indicated parts 9, 10 and in front of the common converter 20. In this case too, the two parts 9, 10 can form a Fourier transforming device. The first part 9 can have a zoom function, for example. Furthermore, the second part 10 can serve, for example, as an F-theta objective or as a flat field lens.

It should be noted at this point that at least one of the components 9, 10, 20 should be used, while the other components are optional.

In the embodiments of 3D printing devices shown in FIGS. 18 to 20, the laser radiation 2 generated by the laser device can be deflected by the scanning device 21 as a whole.

In FIGS. 21 a to 21 c, a preferred embodiment of a projection device 8 is shown, which brings about a reduction by a factor of 5 when imaging from the first plane 5 into the working plane 11. In the projection device 8, three groups 22, 23, 24 of at least one lens each are provided.

The first group 22 has a positive refractive power, the second group 23 has a negative refractive power and the third group 24 in turn has a positive refractive power. 21b and 21c show the passage of the laser radiation 2 through the projection device 8 in two mutually perpendicular directions x, y transversely to the direction of propagation z.

In FIGS. 22a to 22c, a likewise preferred embodiment of a projection device 8 is shown, which effects a 1: 1 mapping from the first plane 5 into the working plane 11. In the projection device 8 there are again three groups 22, 23, 24 each provided by at least one lens. The first group 22 has a positive refractive power, the second group 23 has a negative refractive power and the third group 24 in turn has a positive refractive power.

22b and 22c show the passage of the laser radiation 2 through the projection device 8 in two mutually perpendicular directions x, y transverse to the direction of propagation z. The projection device 8 depicted in FIGS. 23a to 23c corresponds to that according to FIGS. 22a to 22c except for an additional converter 20 which is arranged in the projection device 8 at a location where aperture diaphragms are usually provided. In the exemplary embodiment shown, the converter 20 consists of two Gaussian-to-top hat converters which are arranged one behind the other and are arranged crossed with respect to one another.

23b and 23c show the passage of the laser radiation 2 through the projection device 8 in two mutually perpendicular directions x, y transverse to the direction of propagation z. The embodiment shown in FIGS. 23a to 23c can on the one hand be viewed as a projection device or imaging device with an additional converter. Alternatively, the embodiment can also be understood in this way that between a first Fourier-transforming part 25 and a second Fourier-transforming part 26 of the converter 20 is arranged.

It should be noted at this point that the projection device 8 was shown in the same way in FIGS. 1, 5, 6 and 8 to 12 or in FIGS. 13 to 18 and 20. Nevertheless, the projection device 8 shown in individual of the figures can have components or a structure or properties that differ from those of other individual or all other projection devices 8 in the other figures. Furthermore, due to a different environment of the projection device 8, such as the addition of an array 13 (see FIGS. 1 and 5 or FIGS. 13 and 14), the imaging properties of the projection device 8, such as the distance from the first level 5 to working level 1 1, even if the distance is shown in simplified form in each case the same in the figures.

It should also be noted that by mapping the first plane 5 into the working plane 11, the order of the intensity maxima 7, 7 ‘or the pixels arranged next to one another can be maintained or changed.

For example, three pixels a - b - c arranged next to one another in the first level 5 in the working plane 11 could also be in the order a '- b' - c 'or, for example, in the order c' - b '- a' or for example be arranged in the order b '- a' - c '.

In the embodiment according to FIG. 24, a two-dimensional array, not shown, of for example 9 by 150 optical fibers is provided, of which the laser radiation 2 shown in FIG. 24 goes out. The embodiment comprises two arrays 13 of optical elements 14, which are designed as cylindrical lenses and are used for collimation. The cylinder axes of the cylinder lenses on the two arrays 13 are aligned perpendicular to one another or designed as crossed cylinder lenses.

The embodiment according to FIG. 24 furthermore comprises two mutually crossed arrays 15 of converters 16. Furthermore, the embodiment comprises a Fourier lens 27 and an adjoining array 17 of Fourier lenses 18. The converters 16, together with the Fourier lenses 18, can define the intensity profile of the laser radiation 2 or change one or more of the partial radiations, each of the converters 16 being able to convert, for example, a Gaussian profile into a top-hat profile. Alternatively, each of the converters 16 can convert a Gaussian profile into an M profile, for example.

The nine partial radiations of the laser radiation 2 running next to one another in the vertical direction in FIG. 24 are combined by the Fourier lens 27 with one another in the first plane 5, so that a linear intensity distribution with 1 by 150 pixels is generated there. The intensity distribution from the first plane 5 is mapped into the working plane 11 by the projection device (not shown).

Claims

Patent claims:

1 . Laser device for generating laser radiation which has an intensity distribution with a plurality of intensity maxima in a working plane (1 1), comprising a laser light source (1) which emits laser radiation (2) which in a first plane (5 ) forms a linear or planar intensity distribution (6) with a plurality of intensity maxima (7), a projection device (8) which maps the first plane (5) into the working plane (11) in such a way that in the working plane ( 1 1) a linear or planar intensity distribution (6 ') with a plurality of intensity maxima (7') is formed.

2. Laser device according to claim 1, characterized in that the intensity maxima (7) of the intensity distribution (6) in the first plane (5) in at least one transverse direction which is perpendicular to the direction of propagation of the laser radiation (2), at least partially a first Distance (di) from one another, the projection device (8) depicting the first plane (5) reduced in size in the working plane (1 1) in such a way that the intensity maxima (7 ') of the intensity distribution (6') in the working plane (1 1) in at least one transverse direction, which is perpendicular to the direction of propagation of the laser radiation (2), at least partially have a second distance (d2) from one another which is smaller than the first distance (di).

3. Laser device according to claim 1, characterized in that the intensity maxima (7) of the intensity distribution (6) in of the first plane (5) in at least one transverse direction, which is perpendicular to the direction of propagation of the laser radiation (2), at least partially have a first distance (d 1) from one another, the projection device (8) in such a way in the working level (1 1) shows that the

Intensity maxima (7 ') of the intensity distribution (6') in the working plane (1 1) in at least one transverse direction that is perpendicular to the direction of propagation of the laser radiation (2), at least partially have a second distance (d2) from one another which is greater than is the first distance (di) or which is equal to the first distance (di).

4. Laser device according to one of claims 2 or 3, characterized in that the intensity maxima (7 ‘) in the working plane (1 1) in the at least one transverse direction all have the second distance (d2) from one another.

5. Laser device according to one of claims 1 to 4, characterized in that the reduction achieved by the projection device (8) is between 1 and 20 or that the projection device (8) achieves a magnification between 1 and 5 or a magnification of 1.

6. Laser device according to one of claims 1 to 5, characterized in that the projection device (8) is a telecentric projection device, in particular a projection device that is telecentric on both sides.

7. Laser device according to one of claims 1 to 6, characterized in that at least one component of the projection device (8) is cylindrical in shape.

8. Laser device according to one of claims 1 to 7, characterized in that at least one component of the projection device (8) is a microlens array.

9. Laser device according to claim 8, characterized in that the at least one microlens array is a refractive, reflective or holographic optical element or an optical element with a continuous surface or a binary or multi-stage diffractive optical element.

10. Laser device according to one of claims 1 to 9, characterized in that the working distance between the projection device (8) and the working plane (1 1) is greater than 50 mm, in particular greater than 100 mm, preferably equal to or greater than 200 mm is.

1 1. Laser device according to one of Claims 1 to 10, characterized in that the laser light source (1) comprises at least one fiber laser.

12. Laser device according to one of claims 1 to 1 1, characterized in that the laser light source (1) comprises a plurality of optical fibers (3), from the ends of which a partial radiation of the laser radiation (2) emerges, the optical fibers (3) in particular Single-mode fibers or large-mode area fibers or few-mode fibers are.

13. Laser device according to claim 12, characterized in that the laser light source (1) has a holder with a plurality of grooves, in particular V-shaped grooves, each of the optical fibers (3) being arranged in one of the grooves.

14. Laser device according to claim 13, characterized in that a one-dimensional or two-dimensional array of optical fibers (3) is formed in that the optical fibers (3) or their ends directly, for example by gluing and / or splicing, with an optical component or be connected with a window, in particular wherein the connection of the optical fibers (3) with the optical component or the window creates a preferably one-piece optical component.

15. Laser device according to one of claims 12 to 14, characterized in that the intensity maxima (7) generated in the first plane (5) are each formed by the partial radiation exiting from one of the optical fibers (3).

16. Laser device according to one of claims 12 to 15, characterized in that the partial radiation in the individual

Optical fibers (3) have a mode profile which corresponds to a Bessel profile or a Gaussian profile or an M profile or a top hat profile.

17. Laser device according to one of claims 1 to 16, characterized in that the intensity maxima (7 ') in the working plane (1 1) each have a Gaussian or a super-Gaussian or a top hat profile or an M profile or a have a process-optimized profile.

18. Laser device according to one of claims 1 to 17, characterized in that the laser device at least one

Converter (16, 20) comprises the intensity profile (6) of the laser radiation (2) or one or more of the partial radiations can change, the converter (16, 20) being able to convert, for example, a Gaussian profile into a top-hat profile.

19. Laser device according to claim 18, characterized in that the at least one converter (16, 20) is designed as a 2D Gaussian to Airy disc functions converter, in particular as an axially symmetrical binary phase plate, or that the at least one Converter (16, 20) is designed as a 1 D Gaussian-to-Sinc function converter, in particular as two cylindrical binary phase plates which are aligned perpendicular to one another.

20. Laser device according to one of claims 18 or 19, characterized in that a plurality of converters (16) are provided, which are arranged in a one-dimensional or a two-dimensional array (15).

21st Laser device according to one of Claims 18 to 20, characterized in that the at least one converter (20) is integrated into the projection device (8).

22. Laser device according to one of claims 1 to 21, characterized in that the intensity maxima (7 ‘) in the working plane (1 1) each have a circular or a square or a hexagonal outline.

23. Laser device according to one of claims 1 to 22, characterized in that the laser device comprises at least one collimation element (14), in particular a plurality of collimation elements (14), for collimation of the laser radiation emerging from the laser light source.

24. Laser device according to claim 23, characterized in that the plurality of collimation elements (14) is arranged in a one-dimensional or a two-dimensional array (13), which is in particular a lens array.

25. Laser device according to one of claims 1 to 24, characterized in that the plurality of intensity maxima (7 ') in the working plane (1 1) can be switched on or off individually or in groups, in particular by corresponding control of the laser light source (1) .

26. Laser device according to one of claims 1 to 25, characterized in that the laser device comprises means for superimposing individual partial beams emanating from the laser light source (1) into individual pixels in the first plane (5) and / or that the laser device comprises means for dividing individual ones or all of the partial radiations emanating from the laser light source (1) into a plurality of pixels in the first plane (5).

27. Laser device according to one of claims 1 to 26, characterized in that the laser device comprises at least one Fourier lens (27) and / or at least one array (17) of Fourier lenses (18), in particular between the laser light source (1) and the first level (5) are arranged.

28. 3D printing device for generating a spatially extended product, comprising a laser device for generating laser radiation (2) which has an intensity distribution (6 ') with a plurality of intensity maxima (7') in a working plane (11) , a work area to which the starting material for 3D printing to be acted upon by the laser radiation (2) is or can be supplied, the work area being arranged in the 3D printing device in such a way that the laser radiation (2) strikes the work area, as well as a scanning device (21) which can target the laser radiation (2) to different locations in the work area, characterized in that the laser device is a laser device according to one of claims 1 to 27.