DEVICE FOR GENERATING A DOUBLE SPOT IN LASER MATERIAL PROCESSING

Abstract

A device for variable beam shaping (10) of a light beam (90), comprising: a. an entrance aperture with an entrance cross-section and with an entrance axis which passes through the center of the entrance aperture, wherein a continuation of the entrance cross-section along the entrance axis defines a free propagation volume; b. a collimating optic (85) arranged between the entrance aperture and an array of mirrors; c. the arrangement of mirrors, comprising i. a first mirror (21), the first mirror (21) having a reflective surface only on a side facing a collimated laser beam and being arranged partially in a collimated laser beam for reflecting a partial beam; ii. a second mirror (22) having a reflecting surface in the direction of the reflecting surface of the first mirror (21) for redirecting the reflected partial beam of the collimated laser beam from the first mirror (21); iii. a third mirror (23) comprising a reflecting surface in the direction of the collimated laser beam to redirect the remaining partial beam of the collimated laser beam onto the second mirror (22); d. a displacement device connected to the first mirror (21) of the array of mirrors for moving it into or out of the collimated laser beam at an angle to the beam direction; e. an angle adjustment device connected to the third mirror (23) of the arrangement of mirrors for rotating it; and f. a focusing optics (87) arranged behind the second mirror (22) for focusing the reflected partial beams of the laser beam with a double focus (99).

Description

Field of the invention

[0001] The invention relates to a device and a method for generating a multiple spot during laser material processing. Description of the relevant state of the art

[0002] When laser processing metals or other materials, it is often desirable to be able to use a double spot or even multiple spots. Various state-of-the-art solutions are known for generating such spots.

[0003] The published German patent application DE 199 61 918 A1 describes a method and device for laser material processing with at least two laser beam foci that are imaged onto the workpiece to be processed. The use of refractive elements in a variable focus geometry creates a double focus from a single laser beam focus, with the distance and intensity between the foci being freely selectable. The technical solution of this document is based on refractive elements, which in practice limits the usable power to up to approximately 10 kW.

[0004] The published German patent application DE 40 24 299 A1 teaches a device for focusing a light beam into at least two focal points, comprising a mirror element that splits the light beam into a number of partial beams corresponding to the number of focal points. The mirror element has a number of mirror surfaces that at least corresponds to the number of focal points, and the mirror element is movable relative to the incident light beam to vary the beam intensity at the individual focal points and the distance between the individual focal points. The system accordingly has at least two mirrors for a double focus. The first concave mirror focuses a collimated laser beam. Between this mirror and the focus is a second mirror that has two different mirror surfaces that are at an angle other than 0° to one another.By varying the position of the second mirror along or perpendicular to the optical axis, the intensity and position of the two spots can be adjusted. A major disadvantage of this invention is that the distance between the second mirror and the workpiece depends on the desired distance between the two spots. During laser material processing, droplets, metal vapors, etc. are created, which limit the service life of the optics. A protective glass is normally used for this purpose, which must be robust enough to withstand a process operation. For an acceptable service life, a geometric distance to the process, i.e. to the focus, is required. Further disadvantages of the teaching of this document are the lack of adjustment options for independently adjusting the intensities and positions of more than two spots and the complexity of the second mirrors, especially with regard toof the coating to the line where the two optical surfaces meet. The surface there has an extremely small radius of curvature, which, combined with the mechanical stresses inherent in the coating, has a strongly negative effect on yield during production.

[0005] A complex mirror is avoided in the system from published international application WO 98 / 51442 A1. In the system described in this document, a first mirror also deflects the laser beam, but in this case the beam is subsequently directed onto two different mirrors. The power distribution is adjusted using the vertical position of the first mirror. The position of the two spots can be changed by horizontally shifting the other two mirrors. Even with this system, however, it is still difficult to adjust the power in more than two spots independently of one another. A major problem, however, is the inherent gap between the other two mirrors. This is disadvantageous for the application of the described system for high laser power because the gap will always be within the laser beam.

[0006] The gap problem is reduced by the teaching of the published Chinese utility model CN 2 05 764 433 U, which arranges mirrors directly next to each other. The distance between two or three different spots is adjusted by tilting the corresponding mirrors. This design is essentially limited to a maximum of three spots, and the power would only be adjustable independently for two spots.

[0007] The object of the present invention is therefore to enable the generation of a double spot with a laser material processing optics for a power of at least 10 kW. Both the position and the power in the different spots should be adjustable. Brief description of the invention

[0008] The present invention provides a device for variable beam shaping of a light beam, comprising: a. an entrance aperture with an entrance cross-section and with an entrance axis which passes through the center of the entrance aperture, wherein a continuation of the entrance cross-section along the entrance axis defines a free propagation volume; b. a collimating optic arranged between the entrance aperture and an array of mirrors; c. the arrangement of mirrors, comprising i. a first mirror, the first mirror having a reflective surface only on a side facing a collimated laser beam and being partially arranged in a collimated laser beam for reflecting a partial beam; ii. a second mirror having a reflecting surface in the direction of the reflecting surface of the first mirror for redirecting the reflected partial beam of the collimated laser beam from the first mirror; iii. a third mirror comprising a reflective surface in the direction of the collimated laser beam for redirecting the remaining portion of the collimated laser beam onto the second mirror; d. a displacement device connected to the first mirror of the array of mirrors for moving it into or out of the collimated laser beam at an angle to the beam direction; e. an angle adjustment device connected to the third mirror of the arrangement of mirrors for its rotation; and f. a focusing optics arranged behind the second mirror for focusing the reflected partial beams of the laser beam with a double focus.

[0009] A further subject of the present application relates to a device for variable beam shaping of a light beam, comprising a. an entrance aperture with an entrance cross-section and with an entrance axis which passes through the center of the entrance aperture, wherein a continuation of the entrance cross-section along the entrance axis defines a free propagation volume; b. a collimating optics arranged between the entrance aperture and an arrangement of four mirrors, where i. a first mirror has a reflective surface only on a side facing the collimated laser beam in order to deflect a partial beam of a collimated laser beam reflected thereon, wherein the first mirror is connected to a displacement device in order to move it into or out of the collimated laser beam at an angle to the beam direction of the collimated laser beam; ii. a second mirror has a reflective surface in the direction of the first mirror to redirect the reflected partial beam of the collimated laser beam to a focusing optics, and the second mirror is connected to an angle adjustment device for its rotation, and wherein the second mirror is arranged partially overlapping behind a fourth mirror; iii. a third mirror has a reflective surface only on a side facing the collimated laser beam, the third mirror being arranged partially overlapping behind the first mirror in order to redirect the remaining partial beam of the collimated laser beam; iv. a fourth mirror comprising a reflective surface in the direction of the third mirror for redirecting the reflected partial beam of the collimated laser beam onto a focusing optic, wherein the fourth mirror is connected to a displacement device for moving it into or out of the collimated laser beam at an angle to the beam direction, and wherein the fourth mirror is arranged partially overlapping behind a second mirror; wherein the reflective surfaces of the first and third mirrors are arranged parallel to one another and the reflective surfaces of the second and fourth mirrors are arranged parallel to one another.

[0010] Furthermore, all four mirrors can also be displaceable transversely to the direction of deflection of the partial beam of the laser beam and the first mirror can additionally be connected to the angle adjustment device.

[0011] Additional aspects, features, and advantages of the present invention will be readily apparent from the following detailed description, which simply shows preferred embodiments and implementations. The present invention is capable of being embodied in other and different embodiments, and its several details are capable of modification in various obvious aspects without departing from the spirit and scope of the present invention. Accordingly, the drawings and descriptions are to be regarded as illustrative and not restrictive. Additional objects and advantages of the invention will be set forth in part in the following description and in part will be obvious from the description, or may be learned by practice of the invention. Short description of the characters

[0012] The invention is described in more detail below with reference to the figures. It will be apparent to those skilled in the art that these are only possible exemplary embodiments, without limiting the invention to the embodiments shown. It shows: Fig. 1 shows an embodiment with three mirrors, wherein one mirror is displaceable in the direction of deflection of the axis of the laser beam. Fig. 2 shows an embodiment with four mirrors, two mirrors being movable parallel to the direction of deflection of the axis of the laser beam. Fig. 3 shows an embodiment with four mirrors, two mirrors being movable transversely to the direction of deflection of the axis of the laser beam. Fig. 4 shows an embodiment with four mirrors, where four mirrors are displaceable in the direction of deflection of the axis of the laser beam. Fig. 5 shows an embodiment with three mirrors, wherein three mirrors are displaceable in the direction of deflection of the axis of the laser beam. Fig. 6 shows an embodiment with three mirrors, two mirrors being movable in the direction of deflection of the axis of the laser beam. Detailed description of the invention

[0013] The above-stated object of the invention is achieved by the features of the independent claims. The dependent claims cover further specific embodiments of the invention.

[0014] The invention provides a device capable of generating at least one double spot. According to the present invention, the power distribution is selected by inserting at least a first mirror into the laser beam. The light beam always falls on only one side of the mirror, so that the mirror can be manufactured simply and cost-effectively. The resulting (reflected) partial beams of the laser beam are mirrored by additional mirrors in such a way that they are reflected again next to the non-reflected (direct) part of the laser beam. The total diameter of the recombined partial beams (reflected and direct) is kept as small as possible so that the downstream optical system can also be as small as possible. A raw beam diameter of between 20 - 50 mm increases by a maximum of only 1 mm with the present invention.The solution benefits both a cost-effective solution and a long service life of the protective glass.

[0015] A first embodiment with three mirrors is shown in Fig. 1. The divergent light beam 97 is collimated by the collimation optics 85. The collimated beam strikes the first and third mirrors 21, 23 and is reflected as first and second partial beams 91, 92 onto the second mirror 22, which reflects the beam onto the focusing optics 87, which then forms a double focus 99. In this embodiment, the power distribution is achieved by inserting the first mirror 21 into the laser beam in the direction of the double arrow, i.e., in the direction of deflection. However, here the laser light that is not coupled out is slightly tilted by the third mirror 23, which is connected to an angle adjustment device. Both beams then strike the second mirror 22, which guides the partial beams of the laser beam toward the focusing lens 87. The Fig. The embodiment shown in Figure 1 is cost-effective due to the small number of small mirrors.

[0016] Furthermore, it is possible to shift the mirrors not perpendicular to the laser beam, but rather diagonally to it, as in Fig. 2 is shown as an example with respect to the first mirror 21 and fourth mirror 24. The second mirror 22 can be tilted or rotated to adjust the distance of the double focus. Fig. 3 shows a variant of the representation from Fig. 2, in which the first and fourth mirrors 21, 24 can also be moved transversely to the laser beam direction (point with circle as axis) into the collimated laser beam. In principle, the displacement or tilting is not limited to individual mirrors, as in Fig. 4 is shown as an example and the direction of movement is indicated by the double arrows.

[0017] A significantly shorter variant of the present invention is described in Fig. 5. Here, the first mirror 21 and the third mirror 23 are moved together with the laser beam, either vertically ( Fig. 5) or diagonally ( Fig. 6). For this purpose, the first mirror 21 is also tilted slightly so that the two partial beams are focused on different positions on the workpiece. The vertical distance between the first mirror 21 and the third mirror 23 is chosen such that no vertical gap is created between these two mirrors for any possible tilt of mirror 21. This ensures that each laser light beam falls either on mirror 21 or mirror 23.

[0018] For example, in Fig. In the embodiment shown in Figure 5, the second mirror can also be omitted, which then results in the laser material processing head having a 90° angle and no longer being linear. Reference symbol 10 Beam shaping device 21 first mirror 22 second mirror 23 third mirror 24 fourth mirror 85 Collimation optics 87 Focusing optics 90 light beam 91 first partial beam 92 second partial beam 97 divergent light beam 98 focused light beam 99 Double Focus

Claims

[1] A device for variable beam shaping (10) of a light beam (90), comprising: a. an entrance aperture with an entrance cross-section and with an entrance axis which passes through the center of the entrance aperture, wherein a continuation of the entrance cross-section along the entrance axis defines a free propagation volume; b. a collimating optic (85) arranged between the entrance aperture and an array of mirrors; c. the arrangement of mirrors, comprising i. a first mirror (21), the first mirror (21) having a reflective surface only on a side facing a collimated laser beam and being arranged partially in a collimated laser beam for reflecting a partial beam; ii. a second mirror (22) having a reflecting surface in the direction of the reflecting surface of the first mirror (21) for redirecting the reflected partial beam of the collimated laser beam from the first mirror (21); iii. a third mirror (23) comprising a reflecting surface in the direction of the collimated laser beam to redirect the remaining partial beam of the collimated laser beam onto the second mirror (22); d. a displacement device connected to the first mirror (21) of the array of mirrors for moving it into or out of the collimated laser beam at an angle to the beam direction; e. an angle adjustment device connected to the third mirror (23) of the arrangement of mirrors for rotating it; and f. a focusing optics (87) arranged behind the second mirror (22) for focusing the reflected partial beams of the laser beam with a double focus (99). [2] A device for variable beam shaping (10) of a light beam (90), comprising a. an entrance aperture with an entrance cross-section and with an entrance axis which passes through the center of the entrance aperture, wherein a continuation of the entrance cross-section along the entrance axis defines a free propagation volume; b. a collimating optic (85) arranged between the entrance aperture and an array of four mirrors, wherein; i. a first mirror (21) has a reflective surface only on a side facing the collimated laser beam in order to deflect a partial beam of a collimated laser beam reflected thereon, wherein the first mirror (21) is connected to a displacement device in order to move it into or out of the collimated laser beam at an angle to the beam direction of the collimated laser beam; ii. a second mirror (22) has a reflective surface in the direction of the first mirror (21) in order to deflect the reflected partial beam of the collimated laser beam onto a focusing optics (87), and the second mirror (22) is connected to an angle adjustment device for its rotation, and wherein the second mirror (22) is arranged partially overlapping behind a fourth mirror; iii. a third mirror (23) has a reflective surface only on a side facing the collimated laser beam, the third mirror (23) being arranged partially overlapping behind the first mirror (21) in order to deflect the remaining partial beam of the collimated laser beam; iv. a fourth mirror (24) comprising a reflective surface in the direction of the third mirror (23) for redirecting the reflected partial beam of the collimated laser beam onto a focusing optics (87), wherein the fourth mirror (24) is connected to a displacement device in order to move it into or out of the collimated laser beam at an angle to the beam direction of the collimated laser beam and wherein the fourth mirror (24) is arranged partially overlapping behind the second mirror (22); wherein the reflective surfaces of the first and third mirrors (21, 23) are arranged parallel to one another and the reflective surfaces of the second and fourth mirrors (22, 24) are arranged parallel to one another. [3] The device (10) according to claim 2, wherein all four mirrors (21, 22, 23, 24) are additionally displaceable transversely to the direction of deflection of the partial beam of the laser beam and the first mirror is additionally connected to the angle adjustment device.

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