DE202015101457U1 - Optical system for a laser processing machine, having an optical element in a plug of a light guide cable - Google Patents

Abstract

An optical system (2) for a laser processing machine, comprising a) a light guide cable (3) with an optical fiber (5) for transmitting a coupled-in laser beam (1, 1f) to a machining head (4), and a connector (6) for connection b) a processing head (4), with a plug receptacle (8) for receiving the plug (6), and with an imaging optics (18) which, when the plug (6) is plugged in, have the optical fiber (5) Focusing from the optical fiber (5) laser beam (1a) in the beam propagation direction after the machining head (4), in particular on a surface of a workpiece (30) for processing the same, characterized in that in the plug (6) of the optical cable (3) an optical Element (13) is arranged, which images a fiber end face (12) of the optical fiber (5) in an intermediate focus (14), that the image of the fiber end face in the intermediate focus (14) is smaller than the fiber end face (12), and di divergence DIVZW of the laser beam (1b) emanating from the intermediate focus (14) is greater than the divergence DIVFE of the laser beam (1a) emerging from the fiber end surface (12), and if the plug (6) is plugged in the imaging optics (18) of the machining head (4 ) focuses the laser beam (1b) emanating from the intermediate focus (14) in the beam propagation direction after the machining head (4).

Description

• a) ein Lichtleitkabel, mit einer Lichtleitfaser zur Übertragung eines eingekoppelten Laserstrahls zu einem Bearbeitungskopf, und mit einem Stecker zum Verbinden der Lichtleitfaser mit dem Bearbeitungskopf,
• b) einen Bearbeitungskopf, mit einer Steckeraufnahme zur Aufnahme des Steckers, und mit einer Abbildungsoptik, die bei eingestecktem Stecker einen aus der Lichtleitfaser austretenden Laserstrahl in Strahlausbreitungsrichtung nach dem Bearbeitungskopf fokussiert, insbesondere auf einer Oberfläche eines Werkstücks zur Bearbeitung desselben.

The invention relates to an optical system for a laser processing machine,
full

• a) a light guide cable, comprising an optical fiber for transmitting a coupled-in laser beam to a machining head, and having a connector for connecting the optical fiber to the machining head,
• b) a processing head, with a connector receptacle for receiving the plug, and with an imaging optics, which focuses with the plug plugged in a light emerging from the optical fiber laser beam in the beam propagation direction of the processing head, in particular on a surface of a workpiece for processing the same.

Such an optical system is from the WO 2006/015795 A1 known.

By laser processing methods, in particular laser cutting and laser welding, workpieces, in particular sheets, can be processed with high precision.

In laser processing machines with solid-state lasers as the beam source, the laser beam generally passes through an optical fiber (also called transport fiber) from the laser into a processing head of the laser processing machine. The machining head forms the laser beam emerging from the optical fiber (or its fiber core) at a fiber end surface, in particular wherein the laser beam is focused onto a surface of a workpiece to be machined. The imaging optics in the processing head is matched to a mapping ratio for setting a suitable focus size under application-technical aspects of the machining process. The workpiece to be machined and the machining head are precisely positioned relative to each other during laser machining to ensure high quality machining.

Depending on the desired workpiece machining, lasers with different power are available to users. In recent years, it has become increasingly desirable in practice to machine workpieces with higher laser powers, for example more than 5 kW.

The fiber core diameter determines the dimension of the radiation field of a laser beam within the optical fiber. The higher the power to be transmitted, the higher the power density within the optical fiber and at the fiber end surfaces. When certain limits are exceeded, undesirable nonlinear effects occur, such as stimulated Raman scattering or stimulated Brillouin scattering. These can affect the efficiency of the power transmission and lead to the destruction of the optical fiber.

In an existing optical system for a laser processing machine, with processing head and connected optical fiber, therefore, the transmitted laser power can not be increased arbitrarily; rather, it is necessary to switch to larger fiber core diameters at higher desired laser powers. To preserve the beam quality, the coupling-in divergence into the optical fiber can be reduced with an increased fiber core diameter. Due to the changed fiber core diameter, however, the imaging ratios of the imaging optics arranged in the processing head generally have to be adapted, in particular in order to maintain a desired beam diameter on the workpiece. This requires a complex redesign of the imaging optics of the machining head, usually under increasing the overall length.

From the WO 2006/015795 A1 a laser device with a laser tool is known, in which a laser beam is fed via an optical waveguide with a fiber connector. The laser beam is directed onto a workpiece via a scattering optics, a mirror, collimating optics and focusing optics. The relative position of Leiterauskoppelpunkt at the end of the optical waveguide and the collimating optics is adjustable via the one adjusting device. Furthermore, the scattering optics is displaceable via an adjusting device in the laser tool. With the laser device, a focal spot can be tracked and the focal spot can be kept in a desired size.

The WO 2012/156678 A1 describes a device for isolating a light beam from a laser. A laser beam from a fiber cable is fed via an input lens through an optical isolator to an output plug provided at its end with a first lens array. The output plug is plugged into a collimator, at the end of which a second lens arrangement is provided which generates a collimated laser beam having a predetermined beam diameter. The device can be used with different collimators for different beam diameters of the collimated laser beam.

From the WO 2007/061543 A2 It has become known to arrange a negative lens at the end of an optical fiber, in particular in an end cap, and to arrange behind it a positive lens. Thereby, a compact collimating lens arrangement is provided.

Object of the invention

The invention has for its object to be able to use a processing head of an optical system for a laser processing machine, which is adapted to image the Faserendfläche an inserted optical fiber cable, in a simple manner in conjunction with higher power lasers.

Brief description of the invention

This object is achieved by an optical system of the type mentioned, which is characterized
in that an optical element is arranged in the plug of the optical cable, which images a fiber end surface of the optical fiber into an intermediate focus,
that the imaging of the fiber end surface in the intermediate focus is smaller than the fiber end surface, and the divergence DIVZW of the laser beam emanating from the intermediate focus is greater than the divergence DIVFE of the laser beam emerging from the fiber end surface,
and that, with the plug inserted, the imaging optics of the machining head focus the laser beam emanating from the intermediate focus in the beam propagation direction after the machining head.

In the context of the present invention, it is provided to adapt the laser beam emanating from the fiber end surface of the optical fiber in the plug of the optical cable by the (at least one) optical element of the plug so that the image of the fiber end surface in an intermediate focus the properties of a virtual, positioned at the intermediate focus Optical fiber with a smaller fiber end face (ie smaller diameter of the fiber core) and with greater divergence of the guided in the virtual optical fiber laser beam corresponds.

By means of the system according to the invention, a machining head designed for an optical fiber with a smaller fiber core and greater divergence of the laser beam can also be used with the optical fiber with a larger fiber core, smaller divergence of the laser beam and the plug with the optical element, the imaging optics in the machining head does not need to be changed. In particular, identical beam diameters can be obtained on a workpiece positioned identically behind the machining head.

The diameter of a fiber core and the divergence of a laser beam guided therein are factors in the beam parameter product of the laser beam (which is a measure of the optical brilliance and diffraction limit of the laser beam). Accordingly, it is possible with the optical system according to the invention, while maintaining the Strahlparameterprodukts starting from different fiber core diameters of the optical fiber on the connector set a virtual fiber size. Due to the larger fiber core in the optical fiber in the connector with optical element, a larger power of a connected laser can be transmitted and used for workpiece machining.

In general, in the optical system according to the invention light guide cables with different diameter of the fiber core, and thus suitable for different laser powers, can be used on the same machining head, without changing the imaging properties of the entire system, in particular the geometric conditions in the illumination of a workpiece by the laser beam. The optical system becomes "plug-and-play" capable, i. H. Fiber optic cables with different fiber core diameter can be easily reconnected to the machining head. It should be noted that, in particular, the optical element with regard to focal length and position in the plug and the fiber end surface have to be matched with respect to their position in the plug or adapted to the respective application, in particular to the fiber core diameter of the connected optical fiber cable.

The optical element on the plug can be used instead of a flat protective window, which is provided to protect an optical fiber against contamination, or in addition to a flat protective window.

Preferably, the optical element causes no change in the beam quality of the laser beam. To obtain a diffraction-limited divergence conversion, aspherized radii of curvature can be used on the optical element. Particular preference is given to using high-index substrates with high thermal conductivity and low thermo-optical coefficients.

The processing head comprises one or more optical elements, in particular lenses. The optical element of the connector is typically made of quartz, sapphire, CaF2, BaF2 or ZnS. Typically, the plug comprises exactly one optical element; but it is also possible to provide further optical elements (in front of said optical element), which participate in the imaging of the fiber end face.

Preferred embodiments of the invention

In a particularly advantageous embodiment of the optical system according to the invention, the intermediate focus is a virtual intermediate focus within the connector of the optical fiber cable. Of the Interim focus is therefore on the same side of the optical element as the Faserendfläche. In this way, a small size of the connector is achieved.

Also preferred is an embodiment which provides that the imaging optics of the processing head comprise a collimating lens or collimating lens group and a focusing lens or focusing lens group and that, with the plug inserted, the intermediate focus is at a distance AB in front of the collimating lens or collimating lens group corresponding to the focal length BW of the focal length Collimating lens or collimating lens group corresponds. Also preferred is an embodiment which provides that the imaging optics of the processing head comprise a collimating lens or collimating lens group and a focusing lens or focusing lens group, wherein the collimating lens or collimating lens group and / or the focusing lens or focusing lens group is displaceable in the machining head, and that with the plug inserted, the intermediate focus in at least one position of the collimating lens or collimating lens group and the focusing lens or the focusing lens group at a distance in front of the collimating lens or collimator lens group corresponding to the focal length of the collimating lens or collimating lens group. The collimating lens or lens group, in this positioning, generates a collimated beam which is focused by the focusing lens or lens group, typically at the surface or slightly below the surface of the workpiece to be machined.

Advantageously, in one embodiment of the optical system in the plug exactly one optical element is provided. As a result, the structure of the plug is particularly simple; In particular, only this needs an optical element (in addition to the fiber end) in the connector relative to the processing head (or its imaging optics) to be aligned. In practice, the alignment takes place on a reference surface of the plug, which rests in the inserted state on a mating surface (stop surface) of the connector receptacle or more generally of the machining head.

In an advantageous embodiment, the optical element is a diverging lens or a converging lens. Such lenses are inexpensive, robust and can be easily integrated into a connector. With a diverging lens, a virtual intermediate focus and thus a particularly compact construction can be set up.

Also preferred is an embodiment which provides that a focal length f of the optical element in the plug and its distance a to the fiber end surface are selected such that the following applies to the divergence DIVZW of the laser beam emitted by the intermediate focus: DIVZW / DIVFE = (1 - a / f) ≤ 3.

This upper limit for DIVZW has proven itself to avoid aberrations, so that a good machining quality on the workpiece can be ensured.

Also preferred is an embodiment in which the following applies for a focal length f of the optical element of the plug and for a distance a of the optical element to the fiber end surface: -1000 mm ≤ f ≤ -4 mm, and 6 mm ≤ a ≤ 100 mm.

The negative focal length f means that the optical element has dissipative properties (and is formed approximately as a negative lens). These ranges have also been proven in practice to obtain a compact connector while diffraction-limited transformation of the fiber exit divergence of the laser beam. In addition, compatibility with many types of machining heads can be achieved in these areas.

Inventive kit

• a) verschiedene Typen TLKi von Lichtleitkabeln, mit i: Typenindex, jeweils mit einer Lichtleitfaser zur Übertragung eines eingekoppelten Laserstrahls zu einem Bearbeitungskopf, und einem Stecker zum Verbinden der Lichtleitfaser mit dem Bearbeitungskopf, wobei zumindest ein Teil der Typen TLKi von Lichtleitkabeln ein optisches Element im Stecker aufweist, und wobei die verschiedenen Typen TLKi von Lichtleitkabeln verschiedene Faserkerndurchmesser DMFKi aufweisen,
• b) einen Typus TBK von Bearbeitungskopf, mit einer Steckeraufnahme zur Aufnahme der Stecker aller Typen TLKi von Lichtleitkabeln, und einer Abbildungsoptik, die bei eingestecktem Stecker einen aus der jeweiligen Lichtleitfaser austretenden Laserstrahl in Strahlausbreitungsrichtung nach dem Bearbeitungskopf fokussiert,
• c) für jeden Typus TLKi von Lichtleitkabel ein eigener, zugeordneter Typus TEKi von Einkoppelvorrichtung, mit der Laserstrahlung von einem Laser in die Lichtleitfaser des Lichtleitkabels eingekoppelt wird, und mit der ein eigener Divergenzwinkel DIVFEi der eingekoppelten Laserstrahlung in der Lichtleitfaser erhalten wird, wobei in allen Typen TLKi von Lichtleitkabeln die Position der Faserendfläche im Stecker und/oder die Position des optischen Elements im Stecker und/oder die Brennweite fi des optischen Elements im Stecker so gewählt ist, dass
• – eine gleiche Position POS einer Faserendfläche der Lichtleitfaser oder einer Abbildung der Faserendfläche durch das optische Element im Stecker in einem Zwischenfokus relativ zu einer Referenzfläche des Steckers erhalten wird,
• – eine gleiche Größe DMFKi der Faserendfläche an dieser Position POS oder DMZWi der Abbildung der Faserendfläche an dieser Position POS erhalten wird,
• – und eine gleiche Divergenz DIVFEi des an dieser Position POS aus der Faserendfläche austretenden Laserstrahls oder DIVZWi des an dieser Position POS vom Zwischenfokus ausgehenden Laserstrahls erhalten wird.

The scope of the present invention also includes a modular system for assembling optical systems for laser processing machines, comprising:

• a) different types TLKi of optical cables, with i: type index, each with an optical fiber for transmitting a coupled laser beam to a machining head, and a connector for connecting the optical fiber to the machining head, wherein at least a part of the types TLKi of optical cables an optical element in the Connector, and wherein the different types TLKi of optical cables have different fiber core diameters DMFKi,
• b) a type TBK of machining head, with a connector receptacle for receiving the connectors of all types TLKi of optical cables, and an imaging optics, which focuses a plugged from the respective optical fiber laser beam in beam propagation direction after the processing head,
• c) for each type TLKi of optical fiber cable a dedicated type TEKi of coupling device, with the laser radiation from a laser in the optical fiber of the optical fiber cable DIVFEi of the coupled laser radiation is obtained in the optical fiber, wherein in all types TLKi of fiber optic cables, the position of the fiber end face in the plug and / or the position of the optical element in the plug and / or the focal length fi of the optical Elements in the plug is chosen so that
• A similar position POS of a fiber end surface of the optical fiber or an image of the fiber end surface is obtained by the optical element in the plug in an intermediate focus relative to a reference surface of the plug,
• An equal size DMFKi of the fiber end surface is obtained at this position POS or DMZWi of the image of the fiber end surface at this position POS,
• And an equal divergence DIVFEi of the laser beam emerging at this position POS from the fiber end face or DIVZWi of the laser beam originating at this position POS from the intermediate focus is obtained.

From the modular system, in particular the above-described optical systems according to the invention can be assembled. Depending on the requirements (that is, depending on the required diameter of the fiber core for transmitting a desired laser power), a suitable TLKi type of optical fiber cable can be selected from the construction kit and inserted with its plug into the plug receptacle of the machining head. For the selected type TLKi of fiber optic cable, the appropriate TEKi type of coupling device is selected, with which the laser beam is coupled into the optical fiber. With the various optical systems (including associated coupling device) assembled with the modular system, a similar beam quality of the laser beam is obtained within certain limits, so that it does not significantly affect the beam geometry of the laser beam on the workpiece. The position and size of the real or virtual fiber endface as well as the divergence of the laser beam emanating from the fiber endface or from the intermediate focus are unified. The laser beam can thus be imaged for all composite optical systems with approximately the same beam geometry on the workpiece. In particular, for all types TLKi of optical cables, the associated types TEKi of coupling devices can be selected such that a same beam quality SPP of the laser beam is obtained at the fiber end surface, with DIVFEi * DMFKi * 1/4 = SPP.

Due to the selection of (or due to a change between the) types of optical fiber cable and associated coupling device so no readjustments or re-constructions in the imaging optics of the machining head or for the Bearbeitungspositlon of the machining head relative to the workpiece are basically necessary. The machining head can thus be used in a simple manner universally with different fiber core diameters or with different laser powers.

• d) verschiedene Typen TLAi von Lasern, mit i: Typenindex, insbesondere wobei für jeden Typus TLKi von Lichtleitkabel eine eigene, zugeordnete Kombination von Typus TLAi von Laser und Typus TEKi von Einkoppelvorrichtung vorgesehen ist, wobei sich die verschiedenen Typen TLAi von Laser zumindest in ihrer Laserleistung unterscheiden.

In a preferred embodiment of a kit according to the invention, the latter further comprises:

• d) different types TLAi lasers, with i: type index, in particular wherein for each type TLKi of optical fiber cable own dedicated combination of type TLAi laser and TEKi type of coupling device is provided, wherein the different types TLAi laser at least in their Distinguish laser power.

For lasers with different laser powers, different optical systems can then be assembled, in particular to avoid transmission losses or damage to the optical fiber due to non-linear effects. Larger laser power lasers are typically operated with fiber optic cables of larger fiber core diameter. Within the scope of the invention, it is also possible to use lasers with a laser power of more than 5 kW, in particular 8 kW or more.

An embodiment is preferred in which, in the case of a type TLKi of optical fiber cable, the plug is formed without an optical element, and the fiber end surface is arranged at the position POS relative to the reference surface of the plug. For this type of machining head is usually designed originally. The plug is particularly simple here, since no optical element for imaging the Faserendfläche is necessary. But it is possible to provide an optically ineffective plane-parallel protection window in this connector. Typically, in this type of optical fiber, the smallest diameter of a fiber core of an optical fiber is installed.

Also preferred is an embodiment in which at least two types TLKi of optical fiber cables are formed with an optical element in the plug. In this case, the type of the optical fiber cable can be more accurately adapted to the laser power to be used.

Also preferred is an embodiment in which in all types TLKi of optical fiber cable with an optical element for adjusting the divergence DIVZWi of the outgoing laser beam from the intermediate focus, the optical element positioned in the plug and the focal length fi of the optical element and its distance ai selected to the fiber end are that for the divergence DIVZWi of the laser beam emanating from the intermediate focus: DIVZWi / DIVFEi = (1 - ai / fi) ≤ 3.

This upper limit for DIVZWi has proven itself to avoid aberrations, so that a good machining quality on the workpiece can be ensured.

An inventive modular system can be used to compose an optical system according to the invention.

Further advantages of the invention will become apparent from the description and the drawings. Likewise, according to the invention, the above-mentioned features and those which are still further developed can each be used individually for themselves or for a plurality of combinations of any kind. The embodiments shown and described are not to be understood as exhaustive enumeration, but rather have exemplary character for the description of the invention.

Detailed description of the invention and drawing

The invention is illustrated in the drawing and will be explained in more detail with reference to embodiments. Show it:

1 a schematic cross section through an optical arrangement according to the invention with the plug plugged in;

2 a schematic cross section through the optical arrangement of 1 connected to a laser with a coupling device;

3 a schematic cross-sectional view of three optical systems that have been assembled from a kit according to the invention.

Embodiment of an optical arrangement according to the invention

The 1 shows in a cross section along the propagation direction of a laser beam 1 (in 1 from left to right) an optical system according to the invention 2 for a laser processing machine comprising a light guide cable 3 and a machining head 4 , The fiber optic cable 3 includes an optical fiber 5 and a plug 6 , wherein the optical fiber 5 in the plug 6 is fixed for example by jamming.

The plug 6 is in a plug receptacle 8th of the machining head 4 held, with a reference surface 9 on a shoulder of the plug 6 on a stop surface 10 of the machining head 4 is applied and thereby the plug 6 relative to the machining head 4 is defined.

At a fiber end surface 12 the optical fiber 5 emerges from a fiber core 11 the optical fiber 5 the laser beam 1a out, which has a divergence DIVFE here.

The laser beam 1a is through an optical element 13 (here a negative lens), in the plug 6 is fixed to a laser beam 1b widened. This expanded laser beam 1b has a divergence DIVZW that is greater than the divergence DIVFE when exiting the fiber endface 12 , The optical element 13 forms the fiber end surface 12 in an intermediate focus 14 from. Because this intermediate focus 14 in front of the optical element 13 , ie on the same side of the optical element as the fiber end surface 12 is, this intermediate focus 14 as a virtual intermediate focus 14 designated. The laser beam 1b shines for a viewer behind the optical element 13 from the intermediate focus 14 go out. The in virtual intermediate focus 14 Imaged Faserendfläche appears here with a smaller diameter than the real Faserendfläche 12 ; Preferably, the magnification is 1/3 or more (not further illustrated in FIG 1 , but see 3 ).

The optical element 13 is located at a distance a in the beam propagation direction after the fiber end surface 12 , The intermediate focus 14 is located at a distance Δz behind the Faserendfläche 12 ,

The machining head 6 has in its interior a fixed collimating lens in this example 15 on that the laser beam 1b into a collimated laser beam 1c reshapes. The collimation lens 15 is at a distance AB from the intermediate focus 14 arranged, the focal length BW of the collimation lens 15 equivalent. With a fixed focusing lens here 16 becomes the collimated laser beam 1c then into a focused laser beam 1d reshaped. The collimation lens 15 and the focusing lens 16 make up the imaging optics 18 of the machining head 4 , The focus (focal spot) 17 of the laser beam 1d lies in the beam propagation direction behind the machining head 4 , typically on the surface of a workpiece to be machined (not shown in detail). Note that alternatively the collimation lens 15 and / or the focusing lens 16 also movable along the optical axis OA of the machining head 6 can be stored, with the in 1 Positioning shown can be adjusted via a suitable mechanism (not shown).

Overview of the invention

In the context of the present invention, an optical element 13 in the plug 6 a fiber optic cable 3 arranged, for example by one in the plug 6 arranged optical window is given an optical effect, in particular by the provision of radii of curvature on the surfaces of the protective window, by the application of diffractive structures or by varying the refractive index over the surface. This will be the end of the fiber 12 outgoing radiation 1a transformed so that the designed for a smaller fiber core diameter imaging optics 18 of the laser processing head 4 does not need to be changed. The optical element 13 generates a laser beam at the connector output 1b How it would emerge from a fiber with a smaller fiber core diameter, ie by the fiber connector according to the invention 6 with optical element 13 The jet properties become one out of one fiber 5 emulated with smaller fiber core diameter exiting beam. In this way, the optical system according to the invention 2 "Plug-and-play" capable, ie fiber optic cable 3 or optical fibers 5 with different fiber core diameter can on the machining head 4 simply be repositioned.

The far-field divergence DIVZW of the beam 1b after the optical element 13 depends on the divergence DIVFE of the fiber 5 emerging beam 1a and the focal length f of the optical element 13 and from its distance a to the fiber end face 12 : DIVZW = DIVFE · (1 - a / f)

The from the (virtual) intermediate focus 14 outgoing laser beam 1b acts on the imaging optics 18 in the processing head 4 like a jet that would emanate from a fiber with a smaller fiber core diameter.

The beam parameter product SPP of the laser beam 1 which is determined by the fiber core diameter DMFK and the emitted far-field divergence DIVFE without the optical element according to FIG DIVFE · DMFK · 1/4 = SPP, remains after the Divergence conversion from DIVFE to DIVZW: SSP = DIVFE · DMFK · 1/4 = DIVZW · DMZW · 1/4 where DMZW is the diameter of the fiber core in the image at the intermediate focus 14 designated.

The (virtual) intermediate focus 14 does not lie in the same place as the real fiber end, but points away from the fiber end surface 12 a distance Δz. Δz = a · (1 + (a / f-1) ^-1 )

This must be in the arrangement of Faserendfläche 12 and the optical element 13 inside the fiber connector 6 be taken into account. The fiber connector 6 must be long enough for a shift in the fiber end face 12 by Δz from the design position, from which the construction of the machining head 4 goes out to allow. For the length l before the design position, which in the construction of the fiber connector 6 therefore, it is preferable that: l ≥ 1.5 · a · (1 + (a / f - 1) ^-1 )

Should optical fibers (transport fibers) 5 with different fiber core diameter on the same machining head 4 simply be interchangeable, so must the fiber connector 6 a reference surface 9 always have the same distance to those in the machining head 4 arranged optical elements (lenses 15 . 16 ), when the plug 6 at the machining head 4 is attached. To this reference area 9 must either the fiber end face (without optically effective protective window) or the virtual intermediate focus 14 (when using an optical element in the plug) always have the same distance.

Embodiment of an optical system with coupling device and laser

The 2 shows an optical system according to the invention 2 , such as in 1 presented to a laser 20 (here a solid state laser) is connected. The laser 20 emits a laser beam 1e that has a coupling device 21 in a front end 22 the optical fiber 5 is coupled. Through the coupling device 21 is thereby a divergence of the coupled laser radiation 1f which determines the divergence DIVFE at the fiber endface 12 the optical fiber 5 corresponds (cf. 1 ). This divergence DIVFE is tuned to the diameter of a fiber core of the optical fiber to a particular beam parameter product SPP of the laser beam in and behind the optical fiber 5 to obtain.

For a specific type TLKi of fiber optic cable 3 is thus each a separate type TEKi of coupling device 21 intended. In general, TLKi continues to be for each type of fiber optic cable 3 a separate type pair TEKi, TLAi of coupling device 21 and lasers 20 provided, the laser power to the fiber core diameter in the associated type TLKi of fiber optic cable 3 is tuned.

Inventive kit and composable optical systems

According to the invention, for a given machining head, several types of optical cables and coupling devices, and typically also lasers, are provided which can be used with the machining head without changing the geometrical radiation conditions in the laser machining with the machining head on a workpiece.

3 shows schematically three different optical systems with different types TLKi, TLK2, TLK3 of optical cables 3 that with the same type TBK of machining head 4 can be used.

With the fiber optic cable 3 of the first type TLKi forms the collimating lens 15 of the imaging system 18 the fiber end surface 12 of the fiber optic cable 5 directly from. The at the fiber end surface 12 of the fiber core 11 laser beam emitted with diameter DMFK1 1a with the divergence DIVFE1 reaches the collimating lens 15 without passing through an optically active element in the plug 6 , The fiber end surface 12 is here at the axial position POS (here with the axial position of the reference surface 9 of the plug 6 that are on a stop surface 10 of the machining head 4 is present, coincides). The position POS is also at a distance AB corresponding to the focal length BW of the collimating lens 15 arranged in front of this.

A laser with the fiber optic cable 3 of the first type TLK1 has, for example, a laser power of 3 kW.

With the fiber optic cable 3 of the second type TLK2 becomes the fiber endface 12 from an optical element 13 with a focal length f2 into a virtual intermediate focus 14 displayed. The fiber core diameter DMFK2 of the optical fiber 5 or their fiber core 11 is larger than the fiber core diameter DMFK1 of the first type TLK1.

Instead of the divergence DIVFE2 at the fiber endface 12 (which is determined by a coupling device not shown here for this type TLK2, cf. 2 ) has the intermediate focus 14 outgoing load beam 1b a greater divergence DIVZW2. However, the divergence DIVZW2 is equal to the divergence DIVFE1 of the first type TLK1.

The size (diameter) DMZW2 of the figure of the fiber end surface at the intermediate focus 14 is also equal to the fiber core diameter DMFK1 of the first type TLK1.

The intermediate focus 14 is located at the axial position POS (here, as already mentioned, the axial position of the reference surface 9 corresponds). The fiber end surface 12 is located at a distance Δz2 in front of the position POS, and between the optical element 13 and the fiber endface 12 there is a distance a2.

A laser with the fiber optic cable 3 of the second type TLK2 has, for example, a laser power of 6 kW.

With the fiber optic cable 3 of the third type TLK2 becomes the fiber endface 12 from an optical element 13 with a focal length f3 in an intermediate focus 14 displayed. The fiber core diameter DMFK3 of the optical fiber 5 or their fiber core 11 is here even larger than the fiber core diameter DMFK2 of the second type TLK2.

Instead of the DIVFE3 divergence at the fiber endface 12 (which is determined by a coupling device, not shown here for the type TLK3, see 2 ) has the intermediate focus 14 outgoing load beam 1b a greater divergence DIVZW3. The divergence DIVZW3 is again equal to the divergence DIVFE1 of the first type TLK1.

The size (diameter) DMZW3 of the figure of the fiber end surface at the intermediate focus 14 is again equal to the fiber core diameter DMFK1 of the first type TLK1.

The intermediate focus 14 is also located at the axial position POS (here, as already mentioned, the axial position of the reference surface 9 corresponds). The fiber end surface 12 is located at a distance Δz3 before the position POS, and between the optical element 13 and the fiber endface 12 there is a distance a3.

A laser with the fiber optic cable 3 of the third type TLK3, for example, has a laser power of 9 kW.

The machining head 4 is typically original for the first type TLK1 of fiber optic cable 3 designed with fiber core diameter DMFK1; the divergence DIVFE1 is determined by a coupling device, not shown, of a first type TEK1 (cf. 2 ). Under these conditions arise with the imaging optics 18 certain imaging conditions on a workpiece 30 to which the entire laser processing machine is arranged, for example, regarding the positioning of the workpiece to be machined relative to the machining head 4 ,

The relatively small fiber core diameter DMFK1 limits the usable laser power the laser processing of the workpiece 30 , For a higher laser power or the use of a larger fiber core diameter DMFK2 or DMFK3 according to the invention on one of the types TLK2 or TLK3 of fiber optic cable 3 passed over, with the respective connector 6 with an optical element 13 is provided. The design of the respective connector 6 can be carried out according to the invention as follows: With a constant, known beam parameter product SPP results in a desired larger fiber core diameter DMFKi (with i = 2 or 3) an associated lower divergence DIVFEi than the first type TLK1 of fiber optic cable 3 about the context DIVFE1 · DMFK1 · 1/4 = DIVFEi · DMFKi · 1/4.

This divergence DIVFEi must be provided by the respective type TEKi of coupling device and is thus known.

By the picture of the optical element 13 let there be an {increased} divergence DIVZWi of the laser beam 1b at the intermediate focus 14 which is equal to the divergence DIVFE1. The relationship for the distance ai and the focal length fi according to DIVFE1 = DIVZWi = DIVFEi (1 - ai / fi) and accordingly DIVFE1 / DIVFEi = (1 - ai / fi) (1)

In addition, the optical element 13 in the plug 6 so positioned and the focal length fi of the optical element 13 and its distance ai to the fiber end face 12 chosen such that for the divergence DIVZWi of the laser beam emanating from the intermediate focus 1b applies: DIVZWi / DIVFEi = (1 - ai / fi) ≤ 3. (2)

Within the value range determined by these two mathematical relationships, the distance ai is selected, for example, such that the power density of the laser beam 1b on the optical element 13 the same as the power density of the laser beam 1a on a visually ineffective plane-parallel protection window (not shown) in the plug 6 for the fiber optic cable 3 of the first type TLK1. By defining the distance ai, equation 1 gives the associated focal length fi of the optical element 13 ,

The length of the plug 6 must be set so that the fiber end face 12 of the fiber optic cable 3 of the type TLK2, TLK3 after a shift by Δzi according to Δzi = ai * (1 + (ai / fi-1) ^-1 ) opposite the position POS still within the plug 6 is arranged.

Correspondingly formed types TLKi of optical fiber cable with optical element in the plug, typically together with the first type TLK1 without optical element in the connector, the corresponding types TEKi of coupling devices, preferably also associated types TLAi of lasers, and the one type TBK of the machining head form a Modular system from which various optical systems can be assembled, with which a workpiece can be processed, always the same type TBK can be used by machining head.

A laser processing machine equipped with an optical system composed of a construction kit according to the invention can be used in particular for cutting and welding metallic workpieces, such as metal sheets.

LIST OF REFERENCE NUMBERS

i

laser beam

1a

Laser beam after fiber end surface

1b

Laster beam after intermediate focus

1c

Laser beam after collimation lens

1d

Laser beam after focusing lens

1e

Laser beam after laser

1f

Laser beam after coupling device

2

optical system

3

optical cable

4

processing head

5

optical fiber

6

plug

8th

plug receptacle

9

reference surface

10

stop surface

11

fiber core

12

fiber end face

13

optical element

14

intermediate focus

15

collimating lens

16

focusing lens

17

Focus / focal spot

18

imaging optics

20

laser

21

coupling device

22

front end of the optical fiber

30

workpiece

a

Distance fiber end surface to optical element (indicated if necessary)

FROM

Distance between focus to collimation lens

BW

Focal length collimation lens

DIVFE

Divergence after fiber endface / divergence after coupling device (possibly indicated)

DIVZW

Divergence after intermediate focus (if indicated)

DMFK

Diameter / size of the fiber core (if indicated)

DMZW

Diameter / size of the imaged fiber core at the intermediate focus (if indicated)

f

Focal length optical element (if indicated) Typusindex

OA

optical axis

TBK

Type of machining head

Teki

Type of coupling device (i = 1, 2, 3)

TLAi

Type Laser (i = 1, 2, 3)

TLKi

Type of fiber optic cable (i = 1, 2, 3)

POS

unified position of the fiber end surface (type without optical element) or the intermediate focus (types with optical element)

Az

Distance fiber end surface to intermediate focus (if indicated)

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2006/015795 A1 [0002, 0008]
• WO 2012/156678 A1 [0009]
• WO 2007/061543 A2 [0010]

Claims (14)

Optical system ( 2 ) for a laser processing machine, comprising a) a light guide cable ( 3 ), with an optical fiber ( 5 ) for transmitting a coupled-in laser beam ( 1 . 1f ) to a processing head ( 4 ), and with a plug ( 6 ) for connecting the optical fiber ( 5 ) with the processing head ( 4 ), b) a processing head ( 4 ), with a plug receptacle ( 8th ) for receiving the plug ( 6 ), and with an imaging optics ( 18 ), with the plug ( 6 ) one of the optical fiber ( 5 ) emerging laser beam ( 1a ) in beam propagation direction after the processing head ( 4 ), in particular on a surface of a workpiece ( 30 ) for processing the same, characterized in that in the plug ( 6 ) of the optical fiber cable ( 3 ) an optical element ( 13 ), which has a fiber end surface ( 12 ) of the optical fiber ( 5 ) into an intermediate focus ( 14 ) shows that the image of the fiber end face in the intermediate focus ( 14 ) is smaller than the fiber end surface ( 12 ), and the divergence DIVZW of the interim focus ( 14 ) outgoing laser beam ( 1b ) is greater than the divergence DIVFE of the fiber end face ( 12 ) emerging laser beam ( 1a ), and that with plugged in ( 6 ) the imaging optics ( 18 ) of the machining head ( 4 ) of the intermediate focus ( 14 ) outgoing laser beam ( 1b ) in beam propagation direction after the processing head ( 4 ) focused. Optical system ( 2 ) according to one of the preceding claims, characterized in that the intermediate focus ( 14 ) a virtual intermediate focus ( 14 ) inside the plug ( 6 ) of the optical fiber cable ( 3 ). Optical system ( 2 ) according to one of the preceding claims, characterized in that the imaging optics ( 18 ) of the machining head ( 4 ) a collimating lens ( 15 ) or collimating lens group and a focusing lens ( 16 ) or a focusing lens group, and that when the plug is inserted ( 6 ) the intermediate focus ( 14 ) at a distance (AB) in front of the collimating lens (FIG. 15 ) or collimating lens group, the focal length (BW) of the collimating lens ( 15 ) or collimating lens group. Optical system ( 2 ) according to one of the preceding claims, characterized in that the imaging optics ( 18 ) of the machining head ( 4 ) a collimating lens ( 15 ) or collimating lens group and a focusing lens ( 16 ) or focusing lens group, wherein the collimating lens ( 15 ) or collimating lens group and / or the focusing lens ( 16 ) or focusing lens group is displaceable in the processing head, and that when plugged in ( 6 ) the intermediate focus ( 14 ) in at least one position of collimating lens ( 15 ) or collimating lens group and focusing lens ( 16 ) or focusing lens group at a distance (AB) in front of the collimating lens ( 15 ) or collimating lens group, the focal length (BW) of the collimating lens ( 15 ) or collimating lens group. Optical system ( 2 ) according to one of the preceding claims, characterized in that in the plug ( 6 ) exactly one optical element ( 13 ) is provided. Optical system ( 2 ) according to one of the preceding claims, characterized in that the optical element ( 13 ) is a diverging lens or a converging lens. Optical system ( 2 ) according to one of the preceding claims, characterized in that a focal length f of the optical element ( 13 ) in the plug ( 6 ) and its distance a to the fiber end surface ( 12 ) are chosen so that DIVZW's divergence from the intermediate focus ( 14 ) outgoing laser beam ( 1b ) applies: DIVZW / DIVFE = (1 - a / f) ≤ 3. Optical system ( 2 ) according to one of the preceding claims, characterized in that for a focal length f of the optical element ( 13 ) of the plug ( 6 ) and for a distance a of the optical element ( 13 ) to the fiber end surface ( 12 ) applies: -1000 mm ≤ f ≤ -4 mm, and 6 mm ≤ a ≤ 100 mm. Building set for assembling optical systems ( 2 ) for laser processing machines, comprising: a) various types TLKi (TLK1, TLK2, TLK3) of optical cables ( 3 ), with i: type index, each with an optical fiber ( 5 ) for transmitting a coupled-in laser beam ( 1 . 1f ) to a processing head ( 4 ), and a plug ( 6 ) for connecting the optical fiber ( 5 ) with the processing head ( 4 ), whereby at least a part of the types TLKi (TLK2, TLK3) of optical cables ( 3 ) an optical element ( 13 ) in the plug ( 6 ) and wherein the different types TLKi (TLK1, TLK2, TLK3) of optical cables ( 3 ) have different fiber core diameters DMFKi (DMFK1, DMFK2, DMFK3), b) a type TBK of machining head ( 4 ), with a plug receptacle ( 8th ) for receiving the plug ( 6 ) of all types TLKi (TLK1, TLK2, TLK3) of optical cables ( 3 ), and an imaging optics ( 18 ), with the plug ( 6 ) one of the respective optical fiber ( 5 ) emerging laser beam ( 1a ) in beam propagation direction after the processing head ( 4 c) for each type of TLKi (TLK1, TLK2, TLK3) of optical fiber cable ( 3 ) a dedicated type TEKi of coupling device ( 21 ), with the laser radiation ( 1e ) from a laser ( 20 ) in the optical fiber ( 5 ) of the optical fiber cable ( 3 ) and with a separate divergence angle DIVFEi (DIVFE1, DIVFE2, DIVFE3) of the coupled-in laser radiation ( 1f ) in the optical fiber ( 5 ) in all types of TLKi (TLK1, TLK2, TLK3) of fiber optic cables ( 3 ) the position of the fiber end surface ( 12 ) in the plug ( 6 ) and / or the position of the optical element ( 13 ) in the plug ( 6 ) and / or the focal length fi of the optical element ( 13 ) in the plug ( 6 ) is selected such that - a same position POS of a fiber end face ( 12 ) of the optical fiber ( 5 ) or an image of the fiber end surface by the optical element ( 13 ) in the plug ( 6 ) in an intermediate focus ( 14 ) relative to a reference surface ( 9 ) of the plug ( 6 ) - an equal size DMFKi (DMFK1) of the fiber endface ( 12 ) is obtained at this position POS or DMZWi (DMZW2, DMZW3) of the image of the fiber end surface at this position POS, and an equal divergence DIVFEi (DIVFE1) of the fiber end surface at this position POS (FIG. 12 ) emerging laser beam ( 1a ) or DIVZWi (DIVZW2, DIVZW3) of the intermediate focus at this position POS ( 14 ) outgoing laser beam ( 1b ). Building set according to claim 9, wherein for all types TLKi (TLK1, TLK2, TLK3) of optical cables ( 3 ) with the associated type TEKi of coupling device ( 21 ) an equal beam quality SPP of the laser beam ( 1a ) at the fiber end surface ( 12 ), with DIVFEi · DMFKi · 1/4 = SPP. Kit according to claim 9 or 10, characterized in that it further comprises: d) different types TLAi of lasers ( 20 ), with i: type index, in particular for each type TLKi (TLK1, TLK2, TLK3) of optical fiber cable ( 3 ) an own, associated combination of type TLAi of laser ( 20 ) and type TEKi of coupling device ( 21 ), whereby the different types TLAi of laser ( 20 ) differ at least in their laser power. Building kit according to claim 9, 10 or 11, characterized in that in one type TLKi (TLK1) of optical fiber cable ( 3 ) The plug ( 6 ) without an optical element ( 13 ), and the fiber end surface ( 12 ) at the position POS relative to the reference surface ( 9 ) of the plug ( 6 ) is arranged. Building kit according to one of claims 9 to 12, characterized in that at least two types TLKi (TLK2, TLK3) of optical fiber cable ( 3 ) with an optical element ( 13 ) in the plug ( 6 ) are formed. Building set according to one of claims 9 to 13, characterized in that for all types TLKi (TLK2, TLK3) of optical fiber cable ( 3 ) with an optical element ( 13 ) to terminate the divergence DIVZWi (DIVZW2, DIVZW3) of the intermediate focus ( 14 ) outgoing laser beam ( 1b ) the optical element ( 13 ) in the plug ( 6 ) and the focal length fi of the optical element (FIG. 13 ) and its distance ai to the fiber end surface ( 12 ) are chosen so that for the divergence DIVZWi (DIVZW2, DIVZW3) of the intermediate focus ( 14 ) outgoing laser beam ( 1b ) applies: DIVZWi / DIVFEi = (1 - ai / fi) ≤ 3.

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