OPTICAL DEVICE AND LASER MACHINING DEVICE

Abstract

Optical device (1) comprising a carrier (4), an optical element (2) and a radiation sink (3), wherein the optical element (2) is mounted on the carrier (4), the optical element (2) is movably attached to the carrier (4), the carrier (4) has a recess (7), wherein the optical device (1) is arranged to interact with electromagnetic radiation (9), dividing the electromagnetic radiation (9) in a first portion (91) and a second portion (92), the optical element is arranged to deflect the first portion in a definable direction, and the second portion (92) is incident into the recess (7) and impinges onto the radiation sink (3).

Claims

1. Optical device comprising a carrier, an optical element and a radiation sink, wherein the optical element is mounted on the carrier, the optical element is movably attached to the carrier, the carrier has a recess, wherein the optical device is arranged to interact with electromagnetic radiation, dividing the electromagnetic radiation in a first portion and a second portion, the optical element is arranged to deflect the first portion in a definable direction, and the second portion impinges onto the radiation sink.

2. Optical device according to claim 1, wherein the electromagnetic radiation and the first portion and/or the second portion is/are incident into the recess.

3. Optical device according to claim 2, wherein the recess extends completely through the carrier from a first side to a second side, wherein the first side is opposed to the second side.

4. Optical device according to claim 1, wherein the carrier and the radiation sink are connected by a thermally insulating material, wherein the thermal conductivity of the thermally insulating material is lower than the thermal conductivity of the radiation sink.

5. Optical device according to claim 1, wherein the mirror is fixedly attached to a chassis which is arranged to move with the mirror, wherein the mirror and the chassis form a movable portion of the optical device, which moves with respect to a fixed portion of the optical device, and a distance between a center of gravity of the movable portion and the first rotational axis is not more than 0.5 mm and a distance between a center of gravity of the movable portion and the second rotational axis is not more than 0.5 mm.

6. Optical device according to claim 5, comprising a bearing which is arranged to bear the movable portion on the carrier, wherein the bearing comprises at least two bending beams, an actuator which is arranged to generate forces which effect the rotation around the first axis of rotation and the rotation around the second axis of rotation independently of one another, wherein the actuator comprises a coil which is fixedly attached to the movable portion, and the bending beams comprise electrical contacts of the coil.

7. Optical device according to claim 1, comprising an actuator which is arranged to generate forces which effect the rotation around the first axis of rotation and the rotation around the second axis of rotation independently of one another, wherein the actuator comprises a coil which is fixedly attached to the carrier, and the thermal resistance between the coil and the movable portion is higher than the thermal resistance between the coil and the carrier.

8. Optical device according to claim 1, wherein the optical element has a first resonance frequency (f1) for rotation around the first rotational axis and a second resonance frequency (f2) for rotation around the second rotational axis, wherein the first resonance frequency (f1) differs from the second resonance frequency (f2) by maximum 10 Hz, preferably 1 Hz.

9. Optical device according to claim 1, comprising a measurement unit which is arranged to measure the deflection of the optical element, wherein the measurement unit is arranged to measure rotation of the optical element around the first rotational axis and rotation around the second rotational axis.

10. Optical device according to claim 9, wherein the measurement unit is arranged to generate a measurement beam which impinges on the movable portion, the movable portion is arranged to reflect the measurement beam, and the measurement unit comprises a detector, wherein the detector is arranged to detect the reflected measurement beam, wherein a location at which the reflected measurement beam impinges on the detector depends on the deflection of the optical element, and the measurement unit is arranged to determine the deflection of the optical element from the location.

11. Optical device according to claim 10, wherein the measurement beam impinges on a side of the optical element which is opposed to the side on which the beam impinges during intended operation.

12. Laser machining device comprising the optical device according to claim 1 and a laser source, wherein the laser source is arranged to emit a laser beam having an energy of at least 0.5 KW the optical device is arranged to interact with the laser beam, wherein the interaction separates the laser beam in a first portion and a second portion, the first portion is deflected in a definable direction, and the first portion of the laser beam has a higher optical power than the second portion of the laser beam.

13. Laser machining device according to claim 12, wherein the optical device is arranged to deflect the first portion along a linear, circular or arbitrary orbit.

14. Laser machining device according to claim 12 comprising a displacement device which is arranged to move the workpiece and the optical device with respect to each other in a definable direction with a definable velocity.

15. Laser machining device according to claim 12, wherein the first portion of the laser beam is arranged to heat the workpiece, for cutting, welding, engraving or imprinting the workpiece.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0044] FIG. 1 shows an exemplary embodiment of the laser machining device in a side view;

[0045] FIGS. 2 and 3 show exemplary embodiments of the optical device in a top view;

[0046] FIG. 4 shows an exemplary embodiment of the optical device in a schematic perspective view;

[0047] FIG. 5 shows an exemplary embodiment of the optical device in a schematic sectional view;

[0048] FIGS. 6 and 7 show an exemplary embodiment of the optical device in a schematic perspective view, and

[0049] FIG. 8 shows the exemplary embodiment of FIG. 7 in a schematic sectional view.

DETAILED DESCRIPTION

[0050] Identical, similar or elements having identical effects are provided with the same reference signs in the figures. The figures and the proportions of the elements represented in the figures to each other are not to be considered as true to scale. Rather, individual elements may be oversized for better representability and/or comprehensibility.

[0051] FIG. 1 shows an exemplary embodiment of a laser machining device 60 in a schematic side view. The laser machining device 60 comprises an optical device 1 and a laser source 5. The laser source is arranged to emit a laser beam 9. The laser beam 9 has an optical power of at least 0.5 kW. The optical device 1 interacts with the laser beam 9, dividing the laser beam 9 in a first portion 91 and a second portion 92, wherein a first portion 91 of the laser beam 9 is deflected.

[0052] The optical device 1 comprises a carrier 4, an optical element 2 and a radiation sink 3. The optical element 2 is mounted on the carrier 4. The optical element 2 is movably attached to the carrier 4. By moving the optical element 2, the first portion 91 of the laser beam 9 is deflected in a definable direction. The carrier 4 has a recess, wherein the second portion 92 of the laser beam 9, which is transmitted through the optical element 2, is incident into the recess 7. The recess 7 extends completely through the carrier 4 from a first side 45 to a second side 46. The second portion 92 impinges onto the radiation sink 3. The first portion 91 of the laser beam 9 has a higher optical power than the second portion 92 of the laser beam. For example, the optical power of the first portion 91 is at least ten times higher than the optical power of the second portion 92.

[0053] The optical element 2 is a mirror, wherein the first portion 91 is reflected by the mirror and the second portion 92 is transmitted through the mirror. The mirror 2 is tiltable around a first rotational axis 21 and a second rotational axis 22. The direction in which the first portion 91 is reflected is definable by tilting the mirror.

[0054] The optical device 1 is arranged to deflect the first portion 91 along a circular orbit. Thus, the mirror performs a wobbling motion. The deflected first portion 91 impinges onto a workpiece. The point in which the first portion 91 impinges on the surface of the workpiece moves along a circular path if the workpiece 6 is not moved with respect to the optical device 1.

[0055] The workpiece 6 is arranged on a displacement device 61, which is arranged to move the workpiece 6 with respect to the optical device 1. In particular, the displacement device 61 is arranged to move the workpiece 6 in a definable direction with a definable velocity with respect to the optical device 1. The displacement device 61 is arranged to move the workpiece 6 along a displacement plane 62. The displacement plane 62 extends essentially perpendicularly with respect to an extension direction of the first portion 91. The displacement device 61 may be an X-Y-table.

[0056] The first portion 91 of the laser beam 9 is arranged to heat the workpiece 6, for cutting, welding, or imprinting the workpiece 6. In particular, the wavelength range of the laser beam 9 and the material properties of the workpiece 6 are selected such, that a particularly large portion of the first portion 91 is absorbed by the workpiece 6.

[0057] FIG. 2 shows an exemplary embodiment of an optical device 1 in a schematic top view. The optical device comprises a mirror 2 which is coupled to the carrier 4. The optical device is arranged to deflect a laser beam 9 having an optical power of at least 0.5 kW, in particular at least 10 kW. The carrier 4 comprises a gimbal bearing comprising an outer portion 41, an inner portion 42, an outer bearing 43 and an inner bearing 44. The outer portion 41 and the inner portion 42 have a frame-like geometry. The outer bearing 43 couples the outer portion 41 and the inner portion 42. The inner bearing 44 couples the optical element 2 and the inner portion 42. The inner bearing 44 and the outer bearing 43 are springs, which are arranged to guide a tilt of the optical element 2. The outer bearing 43 provides a restoring force against the rotation of the optical element 2 around a first optical axis 21. The inner bearing 44 provides a restoring force against the rotation of the optical element 2 around a second optical axis 22. The first rotational axis 21 and the second rotational axis 22 extend along a reflective surface, in particular in the reflective surface, of the mirror 2. In particular, the optical element 2 is mirror-symmetrical with respect to the first rotational axis 21 and the second rotational axis 22.

[0058] The mass of the optical element 2, the mass of the inner portion 42 and the spring constant of the outer bearing 43 essentially define a first resonance frequency f1. The mass of the optical element 2 and the spring constant of the inner bearing 44 essentially define a second resonance frequency f2. The first resonance frequency f1 and the second resonance frequency f2 differ at most by 1 Hz. In operation, the optical element 2 has a first amplitude a1 for a rotation around the first rotational axis 21 at the first resonance frequency f1 and a second amplitude a2 for a rotation around the second rotational axis a2 at the second resonance frequency f2. For example, the first amplitude a1 differs from the second amplitude a2 at most by 0.1°. The inner bearing 44 and the outer bearing 45 may be arranged such that the optical element 2 is rotatable around the first rotational axis 21 and the second rotational axis 22 by at least ±0.05°, preferably by at least ±0.1°.

[0059] The optical device comprises a radiation sink 3 (represented by a dotted line) which is arranged behind the carrier 4 and the optical element 2 as seen in viewing direction of FIG. 3. As seen in a top view. The radiation sink 3 protrudes over the optical element 2 in all lateral directions.

[0060] The motion of the optical device 2 with respect to the carrier 4 is controlled by means of a driver 8. The driver 8 comprises at least one actuator, which is arranged to apply a force to tilt the optical element 2. The actuator may comprise a voice coil actuator, a piezo actuator, an electro-permanent-magnet-actuator, or a shape memory actuator. The driver 8 integrated in the carrier 4.

[0061] FIG. 3 shows an exemplary embodiment of an optical device 1 in a schematic top view.

[0062] The embodiment shown in FIG. 3 differs from the embodiment shown in FIG. 2 in the structure of the carrier 4 and in the bearing. The carrier 4 is a single continuous element. The carrier 4 is connected to the optical element 2 by means of the bearing 46. The bearing 46 comprises four leaf springs, which guide the tilt motion of the optical element 2 around the first optical axis 21 and the second optical axis 22. By opposing control of the actuators, a motion of the optical element 2 in a direction perpendicular to the surface of the mirror 2 is minimized. For example, multiple leaf springs, in particular all leaf springs, are fabricated in a one-piece manner.

[0063] The invention is not limited to the description based on the exemplary embodiments. Rather, the invention comprises each new feature as well as each combination of features, which in particular includes each combination of features in the claims, even if this feature or combination itself is not explicitly stated in the claims or examples.

[0064] FIG. 4 shows an exemplary embodiment of the optical device 1 in a schematic perspective view. The carrier 4 comprises a PCB, wherein the carrier 4 is the mechanically supporting structure of the optical device 1. Four magnets 510 are mounted on the carrier 4 around the opening 7. The opening 7 has a diameter of approximately 23.5 mm. The optical element 2 is circular and has a diameter of 25 mm and a thickness of 2.5 mm. A movable portion 10 is mounted on the carrier 4 by means of a bearing 70. The bearing 70 comprises four mounting posts 72 and four bending beams 71. The bending beams 71 essentially define the mechanical properties of the bearing 70. The bearing 70 bears the optical element 2, wherein the movable portion 10 is rotatable around the first 21 and the second 22 rotational axis. In particular, the first and second rotational axis extend perpendicular with respect to each other. Moreover, bearing may enable a translation of the movable portion 10 in a direction perpendicular with respect to the first 21 and second 22 rotational axis. The bearing has a particularly high stiffness for translation along the plane defined by the first rotational axis 21 and the second rotational axis 22.

[0065] FIG. 5 shows an exemplary embodiment, in particular the embodiment shown in FIG. 4, of the optical device 1 in a schematic sectional view along the first rotational axis 21. The optical device 1 comprises a measurement unit 80 comprising an emitter 83, which emits a measurement beam 83. The measurement beam 81 impinges onto the optical element 2 on a second side which is opposed to a first side 23 of the optical element 2. The electromagnetic radiation 9 impinges onto the first side 23. The first 21 and the second 22 side both comprise dielectric mirrors, wherein the dielectric mirror on the first side 23 has a higher reflectivity for the electromagnetic radiation 9 which is divided in the first portion 91 and the second portion 92 than for the measurement beam 81. The dielectric mirror on the second side 24 has a higher reflectivity for the measurement beam 81 than for the electromagnetic radiation 9, in particular for the second portion 92. The measurement unit 80 is arranged to determine the position of the optical element by means of a detector 82, which is arranged to detect the location of the reflected measurement beam 81.

[0066] Coils 511 are fixedly attached on each side of the movable portion 10, in particular the chassis 49, facing the magnets 510. The coils 511 have a winding axis around which conductive tracks of the coil are wound, respectively. The winding axes extend along a plane, which is defined by the first and the second rotational axis. In particular, at least one coil comprises a winding axis extending along the first rotational axis 21 and at least one coil has winding axis extending along the second rotational axis 22.

[0067] The magnets 510 comprises two magnet portions 512 respectively, which are magnetized in an antiparallel fashion. The magnet portions 512 are arranged above one another in a direction perpendicular with respect to the first and second rotational axes. The magnet portions are magnetized in a direction along a plane defined by the first 21 and second 22 rotational axis. In particular, the magnet portions 512 are magnetized along the first rotational axis 21 or the second rotational axis 22. Depending on the direction of the current within the coil, the coil is attracted to and repelled from a magnet portion 512, which creates a momentum rotating the optical element 2 around the first rotational 21 axis or the second rotational axis 22 in a clockwise or counterclockwise direction. The magnet 510 comprises a return structure 510, which guides the magnetic field of two magnet portions 512, which are magnetized in an antiparallel fashion.

[0068] The coils 511 may be controlled in pairs so that coils 511 that cause a rotation around the same axis of rotation 21, 22 are controlled commonly. In particular, coils 511 causing a rotation around different axes of rotation 21, 22 may be controlled separately. The coils 511 may be electrically connected by means of the bearing 70. In particular, the bearing posts 72 and the bending beams 71 may be formed from an electrically conductive material, which is connected electrically to the coils 511. FIGS. 4 and 5 show an embodiment of the optical device 1, wherein the coils are fixedly attached to the moving portion 10 and the magnets 10 are fixedly attached to the carrier 4. Typically, the mass of the magnets is higher than the mass of coils, whereby this embodiment enables a lower mass being moved with the movable portion 10, which is particularly advantageous for fast movement of the movable portion 10. According to an alternative embodiment, the magnets 510 may be fixedly attached to the moving portion 10 and the coils 511 may be fixedly attached to the carrier 4. Advantageously such embodiment simplifies the electrical connection of the coils and simplifies dissipating the heat generated within the coils during operation. According to a third alternative, some coils may be attached to the movable portion 10 and other coils may be attached to the carrier 4 and some magnets may be attached to the movable portion 10 and some magnets may be attached to the carrier 4. For example, coils causing a rotation around the first rotational axis 21 are attached to the movable portion 10 and coils 511 causing a rotation around the second rotational axis 22 are attached to the carrier 4 and magnets causing a rotation around the first rotational axis are attached to the carrier 4 and magnets causing a rotation around the second rotational axis are attached to the movable portion 10.

[0069] FIG. 6 shows an exemplary embodiment of the optical device 1 in a schematic perspective view. The optical device 1 comprises a sealing structure 100 with a sealing surface 102. The sealing surface 102 is a flat surface, which surrounds the movable portion 10 and the bearing 70 as seen in a top view. In particular the sealing surface 102 is a continuous flat surface. The sealing structure may comprise the return structure 513. In other words, the sealing structure 100 comprises a recess in which the movable portion 10 and the bearing 70 are arranged.

[0070] FIG. 7 shows an exemplary embodiment of the optical device in a schematic perspective view, wherein a sealing membrane 101 is arranged on the sealing surface 102. The sealing membrane 102 has an opening 101a. In the region of the opening 102a the sealing membrane is attached to the movable portion 10. Thus, the sealing membrane 102 forms continuous surface connecting the movable portion 10 and the carrier 4, in particular the outer portion 41. The sealing membrane 102 is arranged to form an airtight connection between the movable portion 10 and the carrier 4. In particular, the sealing member forms an airtight barrier between optical element 2 and the actuator 50 as well as between the optical element and the bearing 70. Typically, particles emerge from abrasion due to relative movement of adjacent structures. Thus, the actuator 50 and the bearing 70 bear a high risk of emerging particles. Advantageously, the sealing membrane 101 provides a physical separation between the structures which cause particles, namely the bearing and the actuator 50, and the structures which are particularly damageable by particles, namely the optical element 2. Thus, the sealing membrane 101 prevents deposition of particles on the optical element 2, which improves the optical quality and reduces the risk of failure of the optical device 1.

[0071] FIG. 8 shows the exemplary embodiment of FIG. 7 in a schematic sectional view. The sealing membrane 101 may be adhesively connected to the sealing surface 102 and to the movable portion 10. In particular, the stiffness of the sealing membrane is lower than the stiffness of the bearing 70. For example, the stiffness of the sealing membrane is at least 10 times lower, preferably at least 100 times lower, highly preferred at least 1000 time lower, than the stiffness of the bearing 70. The sealing membrane 101 comprises a decoupling structure 101b, which is arranged to minimize forces which are transferred from the movable portion 10 to the sealing structure 100. The decoupling structure 101b may be formed by a portion of the sealing membrane 101 which has a particularly low stiffness. For example, the decoupling structure 101b is formed by a bulge of the sealing membrane 101. In particular, the decoupling structure 101b surrounds the opening 101a. In particular, the sealing membrane is free of the sealing structure 100 and free of the movable portion 10 in the region of the decoupling structure 101b.

[0072] In the embodiments shown in FIGS. 4, 5 and 8 the coil 511 is fixedly attached to the moving portion and the magnet 510 is fixedly attached to the carrier. However, the coil 511 and the magnets 510 may be interchanged. Thus, the coil 511 may be attached to the carrier and the magnet 510 may be attached to the moving portion.

LIST OF REFERENCE SIGNS

[0073] 1 optical device [0074] 2 optical element [0075] 3 radiation sink [0076] 4 carrier [0077] 5 laser source [0078] 6 workpiece [0079] 7 recess [0080] 8 driver [0081] 9 laser beam [0082] 10 Movable portion [0083] 21 first rotational axis [0084] 22 second rotational axis [0085] 23 First surface [0086] 24 Second surface [0087] 31 thermally insulating material [0088] 41 outer portion [0089] 42 inner portion [0090] 43 outer bearing [0091] 44 inner bearing [0092] 45 first side of carrier [0093] 46 second side of carrier [0094] 47 bearing [0095] 48 axis element [0096] 49 chassis [0097] 50 actuator [0098] 51 Actuator portion [0099] 510 Magnet [0100] 511 Coil [0101] 512 Magnet portion [0102] 513 Return structure [0103] 60 laser machining device [0104] 61 displacement device [0105] 62 displacement plane [0106] 70 Bearing [0107] 71 Bending beam [0108] 80 Measurement unit [0109] 81 Measurement beam [0110] 82 detector [0111] 91 first portion of laserbeam [0112] 92 second portion of laser beam [0113] 100 Sealing structure [0114] 101 Sealing membrane [0115] 101a Opening in sealing membrane [0116] 101b Decoupling structure [0117] 102 Sealing surface [0118] f1 first frequency [0119] f2 second frequency [0120] a1 first amplitude [0121] a2 second amplitude