Laser projection device and method for projecting laser radiation

Abstract

The present invention relates to a laser projection device and a method for projecting images onto a surface. The laser projection device comprises an arrangement of optical waveguides, each having a light-emitting surface limited by an adjustable aperture device. The aperture device is configured to have an aperture opening corresponding to the light-emitting surface. The light-emitting surface can be imaged onto an intermediate image plane by a first imaging optic. The intermediate image plane can be imaged onto an image plane by a second imaging optic. The image plane is the target image area onto which the light-emitting surface is projected. The procedure comprises the steps of providing a laser projection device, adjusting the aperture of the aperture device to correspond to the target image area, and projecting the laser light, limited in the intermediate image plane, into the image plane.

Description

Technical field

[0001] The present invention relates to a laser projection device and a method for projecting laser radiation onto a target image area. The invention enables flexible and precise projection of laser radiation onto a target object, particularly for applications in materials processing, medicine, and other fields. The invention is especially suitable for projecting multimode diode laser radiation or fiber laser radiation. State of the art

[0002] From DE102014106472 A1 a method for radiation scribing of a semiconductor substrate is known in which a two-dimensional field of laser points is used.

[0003] US20160121426 A1 discloses a laser fiber array for singulating semiconductor wafers.

[0004] From JP2011227269 A a laser processing device and a laser processing method are known in which a laser fiber array is used.

[0005] WO03 / 076150 A1 discloses a method and system for processing fragile material using a laser fiber array.

[0006] From DE19840926 A1 a method and arrangement for material processing using laser beams is known, in which a laser fiber array is used.

[0007] From JPH11-254160 A a laser beam source with an optical fiber bundle is known.

[0008] WO94 / 17576 A1 discloses a power-controlled fractal laser system with an optical fiber bundle.

[0009] From JPH02-142695 A a laser beam source with an optical fiber bundle is known.

[0010] From JPS60-221185 A a laser welding process is known in which the spot size can be adjusted by means of a fiber optic bundle.

[0011] The above-mentioned known arrangements have the disadvantage that the spot size can only be adjusted in steps, that the treatment or processing area is unevenly illuminated, and that stray light can reach the side of the treatment or processing area.

[0012] From DE 10 2019 126 888 A1, a laser device for generating laser radiation is known, in which a laser light source has several fibers, the laser radiation being projected onto a working plane. The fibers of the light source can be designed as fiber-coupled semiconductor lasers.

[0013] From WO 2017 / 020 054 A1, a laser lighting device for vehicle headlights is known, comprising two or more laser light sources configured to generate a primary laser light beam. Each laser light source is associated with a light guide for receiving the primary laser light. Object of the invention

[0014] The object of the invention is to provide an improved device for laser treatment and laser processing, which avoids the disadvantages of the known devices. Solution to the task

[0015] The problem is solved by a device according to claim 1 and a method according to claim 8. Advantages of the invention

[0016] With the method and device according to the invention, the target image area to be illuminated can be adjusted not only stepwise but continuously. Furthermore, the processing area onto which the laser radiation can be projected can be illuminated effectively and uniformly, and stray light next to the treatment or processing area can be avoided. Energy can also be saved because unused laser beam sources can be deactivated and the target image area can be illuminated effectively. Description

[0017] The device and method according to the invention are described below.

[0018] The laser projection device comprises several laser beam sources, each connected to an optical waveguide. The optical waveguides can be multimodal. Each optical waveguide has a light-exit end with a rectangular cross-section, arranged in a matrix-like configuration. The light-exit ends can advantageously be arranged in an M x N matrix, where 3 ≤ M ≤ 6 and 3 ≤ N ≤ 6. Particularly advantageous is the arrangement in an M x M matrix, for example, 3x3, 4x4, 5x5, or 6x6.

[0019] The optical waveguides can advantageously be designed as optical fibers and each have a fiber core with a rectangular cross-section. A square cross-section of the fiber core and / or the light-emitting surface of each optical fiber can be particularly advantageous. The optical fibers can, but do not necessarily have to, have a taper at the light-emitting end with a rectangular light-emitting surface. The taper can reduce the divergence of the laser radiation and enable more uniform illumination of the target image area. A taper can be understood as a core cross-section of the waveguide that widens continuously towards the light-emitting end along its length. The taper can therefore be understood as a widening of the optical fiber core.

[0020] However, the fiber ends can also be manufactured without a taper. This can be more cost-effective and result in higher luminance at the fiber ends. It is also advantageous to thin or remove the waveguide sheaths of the optical fibers in a region near the light-exit end to reduce or eliminate gaps between the fiber cores. This can lead to more uniform illumination of the target image area. However, this would entail higher manufacturing costs.

[0021] Laser radiation can be generated by laser beam sources. The laser radiation generated by the laser beam sources can be single-mode, for example, TEM. 00It can be a Gaussian beam. However, it can be particularly advantageous if the laser beam sources are multimode. This allows for higher laser powers, reduces speckle patterns, and improves the illumination of the rectangular core fibers across their entire cross-section. Each laser beam source can comprise or be configured as a laser generator, such as a solid-state laser (which could be a fiber laser, disk laser, or diode laser), or a gas laser. Each laser beam source can also include multiple laser generators, which can be coupled together into an optical fiber, for example, using collimation optics. Polarization coupling can also be incorporated if the laser generators produce linearly polarized laser light.The laser wavelength can advantageously be between 300nm and 1800nm, and particularly advantageously between 700nm and 1100nm.

[0022] A first imaging optical system images the light exit ends of the optical waveguides onto an intermediate image plane. The intermediate image plane can be an xy-plane. An adjustable aperture device, comprising an aperture opening, is arranged in the intermediate image plane. The aperture opening can advantageously be rectangular. The aperture device can advantageously include at least one adjustable cutting edge. The cutting edge can be straight. Advantageously, the aperture device can include two opposing adjustable cutting edges, which extend in the y direction and whose position is adjustable perpendicular to it in the x direction. Particularly advantageous are four adjustable cutting edges, one on each side of a rectangular aperture opening. Two of the cutting edges can extend in the y direction and be displaceable in the x direction, and the other two apertures can extend in the x direction and be displaceable in the y direction.Thus, a rectangular aperture can be represented, forming any rectangular opening within an adjustment range. The optical axis can be arranged in a z-direction, where x, y, and z can form a Cartesian coordinate system. The first imaging optic can comprise one or more lenses. The first imaging optic can be designed for magnification.

[0023] A second imaging optic projects the intermediate image plane onto an image plane. The image plane can be perpendicular to the optical axis. The optical axis can run in a straight line in the z-direction. Beam deflection and / or beam folding can also be incorporated. In this case, the optical axis can undergo a coordinate transformation at the point of beam deflection. The second imaging optic can comprise one or more lenses. It can be configured for magnification, 1:1 imaging, or reduction. It can also incorporate a zoom function.

[0024] A laser control unit is used to activate the laser beam sources. This laser control unit is designed to activate each laser beam source individually. Activation means switching on the laser beam source so that it emits a specific laser power. The inactive laser beam sources can then remain switched off, i.e., emit no laser power.

[0025] The light-exit ends of the waveguides can each have a light-exit core area. They can also have optical waveguide cladding surfaces that surround the core areas. The light-exit core areas can form a non-contiguous total light-exit core area. The total light-exit core area can be more than 70%, advantageously more than 80%, of the area of ​​the smallest convex enveloping surface of the total light-exit core area, and particularly advantageously more than 90%.

[0026] The process includes the following steps: • Provide a laser projection device with the components described above. • Setting the aperture of the aperture device to an aperture opening corresponding to the target image area. • Selecting a first group of laser beam sources whose intermediate image lies at least partially within the aperture. This selection can be performed using a processing unit, which may be integrated into the laser control unit. • Generating laser light by activating the laser beam sources of the first group. • Imaging the light exit ends of the waveguides into the intermediate image plane using the first imaging optics. • Limiting the laser light in the intermediate image plane using the adjusted aperture device. In this step, if necessary, at least a partial area of ​​the intermediate image at the light exit end of at least one laser beam source can be blocked out. • Projecting the laser light, confined in the intermediate image plane, into the image plane using the second imaging optic. In this step, the projection can advantageously be performed with a degree of blurring, such that the spaces between the light-exit ends of the optical waveguides are illuminated in the projection onto the image plane. More precisely, each light-exit end can have a core surface surrounded by waveguide cladding. Since the light in a waveguide is only guided in the core, the waveguide cladding can be dark, i.e., non-light-guiding. With a sharp projection, this can result in spaces in the target image area that are not illuminated or only weakly illuminated. A blurred projection can remedy this to achieve uniform illumination of the target image area.The blurriness can be achieved by slightly defocusing the second imaging optic and / or the first imaging optic.

[0027] The steps can advantageously be carried out in the specified order, although setting the aperture and selecting the first groups can also be done in reverse order or simultaneously.

[0028] The procedure can advantageously be performed multiple times in succession with different target image areas and / or different activated laser beam sources. The target image area can advantageously be a treatment area of ​​a patient or a processing area of ​​a workpiece intended for processing with the projected laser radiation.

[0029] The present invention can be used in various applications, in particular: • Material processing (e.g. exposure, hardening, cutting, drilling, engraving, paint removal, adhesive softening, surface processing of wafers or films) • Medicine (e.g., laser surgery, laser treatment of skin diseases, hair removal) • Other areas (e.g., research, development, quality assurance).

[0030] The figures show the following: Fig. Figure 1 shows a first embodiment. Fig. Figure 2 shows a representation of the optical fiber end surface. Fig. Figure 3 shows an intermediate image. Fig. Figure 4 shows a projection onto the image plane. Fig. Figure 5 shows a blurred projection of the intermediate image onto the image plane. Fig. Figure 6 shows another intermediate image. Fig. Figure 7 shows the projection of the further intermediate image onto the image plane. Fig. Figure 8 shows the smallest convex envelope of the total area of ​​the light-emitting core. Fig. Figure 9 shows an embodiment of the method. Examples of implementation

[0031] The invention is explained below using exemplary embodiments.

[0032] Fig. Figure 1 shows a first embodiment. The figure shows a laser projection device 1, which comprises several laser beam sources 2 and several optical waveguides 4, each with a light exit end 5 connected to one of the laser beam sources 2. The light exit ends 5 are arranged in a matrix-like arrangement. The arrangement of the light exit ends 5 forms an optical waveguide end surface 6, which contains all the light exit ends 5. The light exit surfaces can be imaged onto an intermediate image plane 13 by a first imaging optic 10. The intermediate image plane 13 can be imaged onto an image plane 18 by a second imaging optic 17. The target image area 21, which is to be illuminated, is located in the image plane 18. The laser radiation 3 is limited in the intermediate image plane 13 by an adjustable aperture device 14. The aperture device 14 is set such that it has an aperture opening 15 that corresponds to the target image area 21.The adjustment is made by means of a movable cutting edge 16. The cutting edge is arranged here in the x-direction, whereby the position of the cutting edge is movable in the y-direction, as indicated by a double arrow. A workpiece 30 or a treatment site of a patient can be arranged in the image plane 18.

[0033] The positions of representations AA, BB and CC of the following figures are also indicated in this figure.

[0034] Fig. Figure 2 shows a representation of the optical fiber end surface. The optical fiber end surface 6, shown in plane AA, is formed by the arrangement of the light exit ends of the optical fibers 5. The light exit ends 5 are formed by the light exit core surfaces 7, each of which is surrounded by an optical fiber cladding 8. The arrangement of the light exit surfaces can, but does not have to, be embedded in a ferrule 9.

[0035] Fig. Figure 3 shows an intermediate image. The intermediate image 11 shown in plane BB represents the arrangement of the light exit ends of the optical waveguides 5 in the intermediate image plane 13. The aperture 15 is set to fully open. By moving a depicted cutting edge 16 in the negative x-direction, part of the laser radiation can be blocked.

[0036] Fig. Figure 4 shows a projection onto the image plane. The projection of the intermediate image plane onto the image plane CC is depicted. The target image area 21 is illuminated. With a sharp image, gaps 21 can then occur in which no or only a small amount of laser power is emitted. This is due to the... Fig. 2 shown between the light exit core surfaces 7 are optical waveguide cladding surfaces 8, which cannot conduct light.

[0037] Fig. Figure 5 shows a blurred projection of the intermediate image onto the image plane. This blurring allows for more even illumination of the target image area 21. The blurring can be achieved by defocusing the second imaging optic and / or the first imaging optic.

[0038] Fig. Image 6 shows another intermediate image. Here, two cutting edges are set 16 closer together than in [previous image]. Fig. 3. The intermediate images of some laser beam sources lie outside the aperture 15. These are deactivated, i.e., switched off. The deactivated laser beam sources 12 are indicated in the intermediate image by dashed lines. Some laser beam sources that are only partially imaged outside the aperture 15 are likewise activated, but their laser radiation is spatially clipped by the aperture device.

[0039] Fig. Figure 7 shows the projection of the further intermediate image onto the image plane. The target image area 21 is limited; some laser beam sources are partially blocked at the right edge of the image shown. In a non-figurative variation, a uniformly illuminated target image area can be achieved by slightly blurring the projection.

[0040] Fig. Figure 8 shows the smallest convex envelope of the total light-emitting core area. The total light-emitting core area is a non-connected surface consisting of the light-emitting core surfaces 7 of the optical waveguides. This is shown here in plane AA. The smallest convex envelope 20 of the total light-emitting core area is also shown.

[0041] Fig.Figure 9 shows an embodiment of the method. The method comprises the steps of providing a laser projection device 23, adjusting an aperture of the aperture device 24 corresponding to the target image area 21, selecting a first group of laser beam sources 25, generating laser light 26, imaging the light exit ends of the waveguides into the intermediate image plane (25), limiting the laser light in the intermediate image plane 28, and projecting the laser light limited in the intermediate image plane into the image plane 29.

[0042] Please note that the figures are not to scale.

[0043] The reference symbols used uniformly in all figures are as follows: 1 Laser projection device 2 Laser beam source 3 Laser radiation 4 optical fibers 5 Light exit end 6 Light guide end surface 7 Light emission core area 8 Optical fiber cladding 9 Ferrule 10 First imaging optics 11 Intermediate image 12 deactivated laser beam sources in the intermediate image 13 Intermediate image plane 14 Aperture device 15 adjustable aperture 16 adjustable cutting edges 17 second imaging optics 18 Image plane 19 Laser control unit 20 smallest convex envelopes of the total light emission core area 21 Target image area 22 space 23. Providing a laser projection device 24. Setting the aperture of the aperture device to an aperture corresponding to the target image area, 25 Selecting an initial group of laser beam sources 26 Generating laser light 27. Imaging the light exit ends of the waveguides into the intermediate image plane 28 Limiting the laser light in the intermediate image plane 29 Projecting the laser light confined in the intermediate image plane into the image plane 30 workpieces, patient AA, BB, CC Display layers

Claims

[1] Laser projection device (1) comprising ◯ multiple laser beam sources (2), ◯ several optical waveguides (4) connected to each of the laser beam sources (2), each with a light exit end (5) having a rectangular cross-section, wherein the light exit ends (5) are arranged in a matrix-like manner, ◯ A first imaging optic (10) for imaging the light exit ends (5) of the several optical waveguides (4) into an intermediate image plane (11), wherein in the intermediate image plane (11) an intermediate image of the light exit end (5) of the connected optical waveguide can be generated from each laser beam source (2), ◯ an aperture device (14) arranged in the intermediate image plane (11) with an adjustable aperture opening (15), ◯ a second imaging optic (17) for projecting the intermediate image plane (11) onto an image plane (18), ◯ a laser control unit (19) for individually activating the laser beam sources (2) [2] Laser projection device (1) according to claim 1, wherein the aperture opening (15) is rectangular. [3] Laser projection device (1) according to one of the preceding claims, wherein the light output ends (5) are arranged in an M x N matrix with 3<=M<=6 and 3<=N<=6, and / or wherein the light output ends (5) are arranged in an M x M matrix. [4] Laser projection device (1) according to one of the preceding claims, wherein the aperture device (14) comprises at least one adjustable cutting edge (16). [5] Laser projection device (1) according to one of the preceding claims, wherein the optical waveguides (4) are designed as optical fibers. [6] Laser projection device (1) according to one of the preceding claims, wherein the optical fibers each have a fiber core (7) with a rectangular cross-section and / or wherein the optical fibers at the light exit end (5) each have a taper with a rectangular light exit surface (7). [7] Laser projection device (1) according to one of the preceding claims, wherein the light emission ends (5) each have a light emission core area (7), and the light emission core areas (7) form a non-contiguous total light emission core area, and the total light emission core area is more than 80% of the area of ​​a smallest convex envelope (20) of the total light emission core area. [8] Method for projecting laser radiation into a target image area, comprising a) Providing (23) a laser projection device (1) comprising: • multiple laser beam sources (2), • several optical waveguides (4) connected to each of the laser beam sources (2), each with a light exit end (5) having a rectangular cross-section, wherein the light exit ends (5) are arranged in a matrix-like manner, • A first imaging optic (10), • an adjustable aperture device (14) arranged in the intermediate image plane (11), • a second imaging optic (17), • a laser control unit; b) Setting (24) an aperture opening (15) of the aperture device (14) corresponding to the target image area (21), c) Selecting (25) a first group of laser beam sources (2) whose intermediate image lies at least partially within the aperture (15), d) Generating (26) laser light by activating the laser beam sources (2) of the first group by means of the laser control unit (19), e) Imaging (27) the light exit ends (5) of the waveguides into the intermediate image plane (11) using the first imaging optics (10), f) Limiting (28) the laser light in the intermediate image plane (11) by means of the aperture device (14) set in step b), g) Projecting (29) the laser light confined in the intermediate image plane (11) into the image plane (18) using the second imaging optics (17). [9] Method according to claim 8 wherein in step f) at least a partial area of ​​the intermediate image of the light exit end (5) of at least one laser beam source (2) is hidden. [10] Method according to claims 8 to 9, wherein the projection in step f) is carried out with such a blur that spaces (22) between the light exit ends (5) are illuminated in the projection in the image plane (18). [11] Method according to claims 8 to 10, wherein the target image area (21) is a treatment area of ​​a patient or a processing area of ​​a workpiece (30) which is intended to be processed with the projected laser radiation (3). [12] Method according to claim 11, wherein the method is carried out several times successively with different target image areas (21) and / or different activated laser beam sources (2).

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