METHOD AND APPARATUS FOR LITHOGRAPHY-BASED GENERATIVE MANUFACTURING OF A THREE-DIMENSIONAL COMPONENT

Abstract

In a method for the lithography-based generative manufacturing of a three-dimensional component, in which at least one beam emitted by an electromagnetic radiation source is successively focused by means of an irradiation device onto focal points within a material, as a result of which in each case a volume element of the material located at the focal point is solidified by means of multiphoton absorption, the focal point is displaced in a z-direction, the z-direction corresponding to a direction of irradiation of the at least one beam into the material, the displacement of the focal point in the z-direction being effected by means of at least one acousto-optical deflector arranged in the beam path, in which a sound wave is generated, the frequency of which is periodically modulated.

Claims

1. A method for lithography-based generative manufacturing of a three-dimensional component, in which at least one beam emitted by an electromagnetic radiation source is successively focused by means of an irradiation device onto focal points within a material, as a result of which in each case a volume element of the material located at each focal point is solidified by means of multiphoton absorption, characterized in that at least one of said focal points is displaced in a z-direction, the z-direction corresponding to a direction of irradiation of the at least one beam into the material, the displacement of said at least one focal point in the z-direction being effected by means of at least one acousto-optical deflector arranged in a beam path of the at least one beam, in which a sound wave is generated, a frequency of which is periodically modulated.

2. The method according to claim 1, characterized in that the at least one focal point is displaced by changing a sound wave frequency gradient of the frequency modulation.

3. The method according to claim 1, characterized in that at least two acousto-optical deflectors are used one behind the other in the beam path.

4. The method according to claim 1, characterized in that the at least one focal point is displaced in an x-y plane extending transversely to the z-direction, the displacement in the x-y plane being effected by means of a deflection unit different from the at least one acousto-optical deflector.

5. The method according to claim 1, characterized in that the three-dimensional component is built up layer by layer with layers extending in the x-y plane, a change from one layer to a next layer comprising changing a relative position of the irradiation device relative to the three-dimensional component in the z-direction.

6. The method according to claim 5, characterized in that the displacement of the at least one focal point in the z-direction by means of the at least one acousto-optical deflector takes place within a layer thickness of a layer.

7. The method according to claim 1, characterized in that the at least one focal point is displaced in the z-direction by means of the at least one acousto-optical deflector in order to form a curved outer contour or an outer contour of the three-dimensional component which is oblique relative to the x-y plane, a size of each of the volume elements forming the outer contour.

8. An apparatus-for the lithography-based generative manufacturing of a three-dimensional component using the method according to claim 1, the apparatus comprising a material carrier for a solidifiable material and the irradiation device which can be controlled for position-selective irradiation of the solidifiable material with the at least one beam, the irradiation device comprising an optical deflection unit, in order to focus the at least one beam successively onto focal points within the material, whereby in each case a volume element of the material located at at least one of said focal points can be solidified by means of multiphoton absorption, characterized in that the irradiation device comprises at least one acousto-optical deflector which is arranged in the beam path of the at least one beam and is designed to displace the at least one focal point in a z-direction, the z-direction corresponding to an irradiation direction of the at least one beam into the material.

9. The apparatus according to claim 8, characterized in that the at least one acousto-optic deflector comprises a frequency generator adapted to periodically modulate sound wave frequency.

10. The apparatus according to claim 9, characterized in that the frequency generator is adapted to vary a gradient of the sound wave frequency.

11. The apparatus according to claim 8, characterized in that at least two acousto-optical deflectors are arranged one behind the other in the beam path.

12. The apparatus according to claim 8, characterized in that the optical deflection unit is designed to displace the at least one focal point in an x-y plane extending transversely to the z-direction.

13. The apparatus according to claim 8, characterized in that the irradiation device is adapted to build up the three-dimensional component layer by layer with layers extending in the x-y plane, a change from one layer to a next layer comprising changing a relative position of the irradiation device relative to the three-dimensional component in the z-direction.

14. The apparatus according to claim 8, characterized in that the irradiation device is designed in such a way that the displacement of the at least one focal point in the z-direction by means of the acousto-optical deflector takes place within a layer thickness of a layer.

15. The method according to claim 3, wherein the at least two acousto-optical deflectors have either a direction of beam deflection which is substantially perpendicular to one another or have a same orientation of beam deflection.

16. The apparatus according to claim 11, wherein the at least two acousto-optical deflectors have either a direction of beam deflection extending substantially perpendicular to one another or have a same orientation of beam deflection.

Description

[0045] In FIG. 1, a substrate or carrier is denoted with 1, on which a component is to be built. The substrate is arranged in a material vat, not shown, which is filled with a photopolymerizable material. A laser beam emitted from a radiation source 2 is successively focused into the material by an irradiation device 3 at focal points within the photopolymerizable material, thereby solidifying a volume element of the material located at each focal point by multiphoton absorption. For this purpose, the irradiation device includes an imaging unit comprising a lens 4 that introduces the laser beam into the material within a writing area.

[0046] The laser beam first enters a pulse compressor 5 from the radiation source 2 and is then passed through at least one acousto-optic deflector module 6, whose two acousto-optic deflectors split the beam into a zero-order beam and a first-order beam. The zero-order beam is collected in a beam trap 7. The acousto-optic deflector module 6 comprises two acousto-optic deflectors arranged one behind the other, the direction of beam deflection of which is perpendicular to each other. With regard to the deflected beam of first order, the acousto-optic deflector module 6 acts in each case as a cylindrical lens with an adjustable focal length, so that the first-order beam has an adjustable divergence. The beam of first order is now guided via relay lenses 8 and a deflection mirror 15 into a deflection unit 9, in which the beam is reflected successively by two mirrors 10.

[0047] The mirrors 10 are driven to pivot about axes of rotation that are orthogonal to each other, so that the beam can be deflected in both the x and y axes. The two mirrors 10 can each be driven by a galvanometer drive or electric motor. The beam exiting the deflection unit 9 preferably enters the objective via a relay lens system, not shown, which focuses the beam into the photopolymerizable material as mentioned above.

[0048] To build up the component layer by layer, volume elements of one layer after the other are solidified in the material. To build up a first layer, the laser beam is successively focused on focal points located in the focal plane of the objective 4 within the material. The deflection of the beam in the x,y plane is performed here with the aid of the deflection unit 9, whereby the writing area is limited by the objective 4. For the change to the next plane, the objective 4 attached to a carrier 11 is displaced in the z-direction relative to the substrate 1 by the layer distance, which corresponds to the layer thickness. Alternatively, the substrate 1 can be displaced relative to the fixed objective 4.

[0049] If the component to be produced is larger in the x and/or y direction than the writing area of the objective 4, partial structures of the component are built up next to each other (so-called stitching). For this purpose, the substrate 1 is arranged on a x-y-stage 12, which can be moved in the x and/or y direction relative to the irradiation device 3.

[0050] Furthermore, a control unit 13 is provided which controls the at least one acousto-optical deflector 6, the deflection device 9, the carrier 11 and the x-y-stage 12.

[0051] The acousto-optic deflector 6 forms a cylindrical lens effect that depends on the sound wave frequency gradient of the frequency modulation. The equivalent focal length of the cylindrical lens F.sub.1 can be calculated as follows:

[00001]$F_l=\frac{v_a^2}{\lambda \frac{d{F}_a}{dt}}$

[0052] where v.sub.a is the acoustic propagation velocity in the crystal, A is the wavelength of the laser beam, and dF.sub.a/d.sub.t is the acoustic wave frequency gradient in the crystal. In TeO.sub.2 with a propagation speed of 4200 m/s at a laser wavelength of 780 nm and traversing a bandwidth of ±25 MHz (e.g., starting from a fundamental excitation frequency of 110 MHz) within 0.2 μs, the focal length of the acousto-optic cylindrical lens is 90 mm. For an objective 4 with a focal length of 9 mm and a 20× expansion, this results in a new focal length of the entire system of

[00002]$F_{total}=\frac{F_{Obj}{F}_l}{F_{Obj}+F_l}$

[0053] which corresponds to a displacement in the z-direction, depending on the sign of the gradient, of ±90 μm for the parameters mentioned above. By changing the sound wave frequency gradient, the z-position of the volume element can be adjusted linearly and continuously.

[0054] According to the invention, the described possibility for a continuous displacement of the focal point in the z-direction can be exploited to optimally approximate an inclined or curved surface, as shown schematically in FIG. 3. In FIG. 3, the individual volume elements are labeled 15 and the curved surface of the component is labeled 14. It can be seen that the z-position of the volume elements 15 follows the surface shape, although the size of the individual volume elements 15 can remain the same.

[0055] FIG. 2 shows a modified embodiment of the device according to FIG. 1, in which the acousto-optical deflector module 6, in contrast to FIG. 1, has two acousto-optical deflectors between which relay lenses are arranged to ensure that the focus point at the input and output of the acousto-optical deflector module 6 are arranged on the same line.