DE10007391A1 - Device for working material with laser, e.g. for boring and welding plastics, comprises position-focused modulator which produces predetermined power density distribution - Google Patents

Abstract

Device for working a material with a laser (4) comprises a position-focused modulator (1) which produces a predetermined power density distribution. Independent claims are included for: (a) a method for working a material with a laser containing the device; and (b) use of the modulator to produce a predetermined power density distribution when working a material.

Description

Technical field

The invention relates to a method and an apparatus for material handling and processing processing with electromagnetic radiation according to the generic terms of the independent Claims 1, 11, 16 and 17. A preferred area of application is surface treatment working of workpieces, such as hardening, coating, engraving, Labeling and surfacing of surfaces. Another area of application is welding and drilling, such as welding and drilling Plastics.

State of the art

When processing materials with electromagnetic radiation, and ins especially with laser radiation, plays the correctly set power density distribution (LDV) a dominant role on the workpiece. The correctly set LDV exists on the one hand, in the correct shape of the focal spot (e.g. round, elliptical or general elongated), as well as the correct intensity distribution within the focal spot. That's the way it is For example, advantageous when laser welding aluminum an elongated Use focal spot, the focus of its intensity related to the welding process tensile direction is in the front area.  

For the purpose of material processing, lei are required because of this density, especially lasers. These usually have a round beam profile, the trans to ensure process-adapted LDV using suitable optics must be formed. Static mirrors can be used for this, where the reflected radiation due to the surface structure of the mirror ge is suitable interfered. Another possibility is offered by deformable mirrors, in which over mechanically adjustable actuators the surface structure of the mirror surface and so that the reflection of the radiation is limited to a limited extent can be controlled. Ad is also a complex and error-prone method dition of at least two partial beams.

The possibilities mentioned have the disadvantage that they are specifically designed fits individual solutions that are inflexibly redesigned for every application Need to become. The abovementioned possibilities allow for many applications moreover, only a sequential processing, i.e. H. those to be charged Surface areas can only be irradiated one after the other in a slow manner become. This sequential, writing laser beam processing is used in welding applications also called contour welding. With contour welding there is a continuous movement of the respective machining geometry with the focused one Laser beam with a temporally constant power density distribution. This requires one Relative movement of workpiece and laser beam with corresponding error-prone highly dynamic, mechanical movements. An interesting alternative to Contour welding is simultaneous welding, in which the entire weld contour is joined at once. The resulting very short process times can be avoided this process especially for welding series parts in the Mass production may seem interesting.  

Presentation of the invention

The invention is based on the technical problem, the disadvantages of the prior art Avoid technology as much as possible and a device and a method for the Provide material processing and processing with which a predeterminable Power density distribution can be adjusted flexibly. Device and method should not only allow the sequential machining of workpieces.

The solution to the problem is achieved by a device and by a method according to the Preambles of claims 1, 11, 16 and 17 in conjunction with their characterizing Characteristics specified. Advantageous further developments of the invention direction and the method according to the invention are ge in the dependent claims give.

According to the invention, it was recognized that the problems mentioned are based on the prior art the technology with a device and a method for material processing with Avoid electromagnetic radiation where a spatially resolving beam modulator for generating a predeterminable power density distribution is provided. This makes it possible to process the material sequentially and simultaneously, however in addition to realize a material processing, which in terms of its nature between the sequential and simultaneous processing.

The modulated electromagnetic radiation is used for processing in the present case processing of the workpiece to be loaded. In this sense, everyone is basically Radiation sources can be used, which are the mostly thermal changes in the Can effect workpiece. The radiation densities required for the process lasers are particularly suitable for this purpose. Especially for plastic and processing are suitable for diode and excimer lasers.  

For the purposes of the invention, this can be an amplitude-modulating or an egg act a phase-modulating beam modulator. A combination of Am platitude and phase modulation is possible.

In principle, amplitude modulation can be used with all radiation sources and is particularly versatile. The amplitude modulation is based on that, based on an already polarized radiation field, certain sub-areas This radiation field changes in its polarization state in a controlled manner and with an optical element (analyzer) according to its polarization state be selected. This is a modulation of the amplitude of the individual sections of the entire radiation field possible. The aim of phase modulation is to phase modulate an electromagnetic radiation field so that a desired Interference pattern arises. Starting from a polarized radiation field with The phase positions of individual sub-areas become sufficiently transverse coherent changed in such a controlled manner that these sub-areas in the desired manner interfere. Phase modulation has the advantage of an improved energy balance because there are no radiation components from the original, unmodulated radiation field be hidden. Therefore, phase modulation is particularly suitable for Applications where a particularly high LDV is required on the workpiece.

The beam modulator advantageously contains an arrangement of individual ones predefined LDV-controlling cells. In a simple arrangement, the cells are in arranged on a plane to which the radiation is applied perpendicularly. The given electromagnetic radiation field is broken down into individual cells Partial beam bundle divided. Each of the partial beams is in the cells individually modulated in amplitude and / or phase, in which case Amplitude modulation still requires an additional analyzer. After this Leaving the beam modulator form the individual partial beams in their entirety new, now amplitude and / or phase modulated electromagnetic Radiation field. After propagating the entire radiation field through  beam-shaping and beam-guiding optical elements on the workpiece predefined LDV reached. This solution has the advantage that the LDV per partial beam is possible, the LDV of a partial beam is independent of the LDV of other partial beams. The control is done with it particularly simple and flexible. The spatial resolution of the resulting LDV in the Workpiece level is largely determined by the beam quality of the original Radiation field, the geometry and number of the individual cells and the quality of the downstream beam-shaping and guiding optics.

The beam modulator thus modulates in a spatial resolution in the sense of the above statements and allows the generation of a specifiable or predefined LDV on the Workpiece. Both the focal spot and focus can be specified in its outer dimensions, as well as the intensity of the radiation within the desired focal spot. For example, if the user has a rectangular focus is specified by maximum hiding the corresponding cells of the Beam modulator ensures that no radiation intensity for points outside rectangular focus. Within the focus can be through an appropriate Modulation of the respective cells the specified LDV can be set. The The spatial resolution of the resulting LDV is then largely determined Geometry and number of individual cells.

There are various implementation options for the cells controlling the LDV.

One possibility is that each cell has at least one mobile micro contains mirror. The beam modulator then consists of a movable arrangement Micromirrors, the position of which is preferably electronically controllable (English DMD: digital mirror device). In the simplest version, the micromirrors can only do two Take positions. In a first position, the entire incident radiation reflected. In a second position, the opening behind it is maximally clear give. In a more advantageous embodiment, the tilt angles of the micromirrors can either  can be varied in steps or continuously. This enables finer control of the radiation impinging on the workpiece is possible. Through a control unit the tilt angle required for the desired LDV is determined and set.

Another possibility of designing the beam modulator is that the Cells contain a micropolarizer. The beam modulator then consists of one Arrangement of micropolarizers. Phase modulation is thus possible directly. in the Interaction with a Polari arranged downstream of the micropolarizer arrangement sator can amplitude-modulate the radiation passing through a micropolarizer become.

In a preferred embodiment, the individual (modulation) cells of the Beam modulator made of liquid crystals. In this case, the beam modulator has one Arrangement of individual liquid crystal cells. The liquid crystal cells can in be arranged flat over a regular scheme and then form one regular arrangement or an array of individual liquid crystal cells, d. H. individual modulators.

The modulation of a partial beam falling on the individual cell takes place within the cell through targeted influencing and utilization of the electro-optical Effects. For example, you can look at the birefringence properties of the Make use of liquid crystals. Specifically, by applying an electrical Voltage to the liquid crystal cell the extraordinary refractive index of the Liquid crystals are changed. As a result, the polarization of the incident electromagnetic radiation can be changed. The direction of polarization can be continuously or depending on the applied voltage step by step. By applying individual tensions to the individual Cells of the liquid crystal cell arrangement are thus obtained within the overall beam a variety of individual polarization directions. By doing this, one is Phase modulation possible directly. Depending on the amplitude of the applied to a cell  alternating voltage, usually a square wave voltage, can be the refractive indices of the liquid crystals can be set specifically. Through the targeted modulation of the phases of the individual partial beams, these partial beams are achieved in the workpiece plane Interfer to the desired LDV. Is also in the beam path Analyzer, so the radiation can be amplitude modulated. Also a combination of amplitude and phase modulation is feasible, for example in the inside of a single modulator two liquid crystal arrays in optical alignment one after the other to be ordered.

The modulating unit, consisting of an arrangement of liquid crystal cells and the polarizer, modulates the radiation in a spatially resolved manner and is therefore used in the literature occasionally referred to as a spatial light modulator (SLM). Deviating from this is in some references, and also in the context of this invention Description of the application, already the arrangement of liquid crystal cells as spatially resolving Beam modulator understood.

If amplitude modulation is used, the polarizer can be reflected in reflection or in transmission po larize. A reflective polarizer is particularly advantageous at high LDV because a polarizer operated in transmission would heat up too much. It is expedient to absorb the unused radiation components in a beam trap.

Antiferroelectric liquid crystals are suitable for the purposes of the present invention such as nematic, smectic and cholestric liquid crystals. This allow in particular continuous modulation of the polarization or Phase position. This enables a particularly fine adjustment of the polarization or Phase position and thus particularly fine gradations possible within the LDV. Further can also be used ferroelectric liquid crystals, which have the advantage bring about short switching times, but only a gradual or leaping one Allow adjustment of the polarization or phase position. This requires coarser Gradations in the setting of the polarization or phase position and thus coarser  Gradations within the LDV. With ferroelectric liquid crystals, this is a lower resolution of the LDV compared to anti-ferroelectric Liquid crystals possible.

The preferred choice of one containing an array of liquid crystal cells Beam modulator makes use of a modular arrangement of Hochlei Stungsdiodelaserbaren or an excimer laser as electromagnetic radiation source particularly attractive. Liquid crystal cell arrangements are usually flat, rectangular cut, so that a homogeneous, rectangular beam profile of a Arrangement of high-power diode lasers or an excimer laser with special low imaging errors can be mapped. The individual cells can have different shapes. With one-dimensional beam modulators they have individual cells have a rectangular, for example strip-like shape. At Two-dimensional beam modulators should match the shape and arrangement of each Cells must be selected so that the cell gaps are kept small to avoid the local resolution of the LDV fine and the undefined or unmodulated areas small to keep. Rectangular, square or hexagonal geometries are available. It other geometries are also conceivable, which then correspond to the task be adjusted. With other lasers there is usually a round beam profile, so that elaborate optics are required, which match the round beam profile to the rectangular one Show liquid crystal arrangement. Alternatively, with a round beam profile, either some of the cells are not exposed to radiation or the beam accordingly be expanded, which would however be less efficient.

In order to utilize the output LDV of the available radiation source as effectively as possible, little radiation should be lost through the beam modulator and the beam guiding and shaping optical elements. An LDV specified for the individual machining process with the greatest possible intensity on the workpiece can be realized in particular if the destruction threshold of the individual optical components forming the beam modulator is not exceeded or if cells with the highest possible destruction threshold are selected. For the purpose of material processing and processing, it is therefore advantageous not to fall below a destruction threshold of 100 W / cm ² , for certain areas of application even higher values of at least 200 W / cm ² to 1000 W / cm ^{2 are} advantageous.

To ensure an increased dynamic range and easier handling homogeneous illumination of the active area of the beam modulator is advantageous. Homogeneous illumination means that all cells have the same Radiation intensity can be applied.

For controlled modulation of the radiation component that is generated by a single It passes through the modulation cell if the individual modulation cells are individually and individually addressable. The individual addressing can lead to Example, an individual voltage is applied to an individual liquid crystal cell become. The addressing is preferably electrical, but is also optical Addressing possible. The addressing takes place via a suitable external Control unit, for example via a computer. Appropriate means ensure that Delivery of the addressing signal from the control unit to the individual cell. This Means can be, for example, electrical cables, controllers, optical fibers and the like his. The control unit ensures quick and flexible adaptation of the LDV to the respective requirements of the machining process and the material parameters in order to achieve an optimal processing result.

In addition to the external control unit mentioned, it is also possible to use the control unit to combine the beam modulator into one unit. In a broader sense this can also be seen as a beam modulator. The control unit can for example one or more programmed or programmable chips such as For example, be Asics or Eproms. Then with a suitable power supply the beam modulator does its work autonomously. The prerequisite here is that the individual cells can be individually addressed by the integrated control unit. Of  The advantage here is that the beam modulator or the one contained therein Control unit is also addressable. Then namely the functioning of the chips can also be influenced externally and for example between several in the Memory modules existing work programs to be changed.

To ensure that the beam modulator is acted on as homogeneously as possible, can optionally optics for homogenizing the radiation to be seen. This is particularly advantageous with diode lasers, since these are usually large Show divergence angles. The radiation emerging from the beam modulator can also optionally mapped onto the workpiece via another lens (focused) become.

In the sense of the present invention, the beam modulator can dim one sionale as well as a two-dimensional beam modulation. One can and two-dimensional modulators are used. The two-dimensional modulators allow simultaneous machining of workpieces, while the one-dimensional modulators do not allow this. Both variants of Beam modulators allow processing that is of a type between the two Variants sequential processing and simultaneous processing. Will with the Welded device according to the invention, so the welding process is a thing in between between contour welding and simultaneous welding.

The device according to the invention and the method according to the invention are intended are explained below using exemplary embodiments.

FIG. 1a shows the method of the one-dimensional beam modulation with the aid of the device according to the invention. The beam modulator ( 1 ) in this example consists of 10 elongated or strip-shaped (modulation) cells ( 2 ) with a downstream polarizer ( 3 ) for amplitude modulation. In the present case, the cells are smectic liquid crystal cells. The longitudinal direction of the cells is the y direction. The cells are arranged next to each other in the x direction. Polarized radiation ( 4 ) from a diode laser is applied to the cells vertically from above, which is indicated by the arrows shown. The active area ( 5 ) is available for beam modulation. The electromagnetic radiation passing through a single modulation cell receives a certain modulated polarization. However, neighboring cells modulate differently, so that one-dimensional modulation with different radiation intensities in the x direction occurs. In the workpiece plane ( 6 ), this is expressed by a stripe-shaped intensity pattern. No modulation is carried out in the y direction. There the intensity is constant within a strip or corresponds to the initial LDV.

The one-dimensional beam modulation lends itself when for the machining process an elongated focus on the workpiece must be mapped, d. H. if the Fo kiss length is greater than the focus width. As a special case, there is a linear focus possible. In the direction of the focus length or the long axis of the focus line, that is subsequently the x-direction is modulated and the given one above Intensity distribution set. Perpendicular to this, d. H. in the y direction, won't modulated. The intensity distribution in the y direction is then correct except for a constant one Factor coincides with that intensity distribution with which the beam modulator acts was struck. During processing, there is a relative movement of the focus line and Workpiece, for example the parts to be acted upon the resting Workpiece surface can be scanned one after the other by the machining beam. Doing so dynamically set the required intensity distribution on the workpiece. The processing takes place quasi-simultaneously, i. H. the feed movement is continuous an adjustment of the intensity distribution in discrete steps. For every focus position the required LDV is calculated using a corresponding sentence Voltage values set. The number of processing steps required corresponds to the quotient of the machining length and the selected focus or Machining step width. This number also corresponds to the number of required  Sets of electrical voltage values available from the control unit must be asked. The interaction of the selected feed rate and focus width determines the frequency at which the liquid crystal device as dynamic mask sets the desired LDV on the workpiece.

The two-dimensional beam modulation is shown in Fig. 1b. In this example, the beam modulator ( 1 ) consists of a total of 25 individual cholesteric liquid crystal cells ( 2 ), with 5 cells each in the x and y directions. Beam modulator ( 1 ) and polarizer ( 3 ) form the modulating unit with which it is possible to modulate the laser radiation ( 4 ) in both the x and y directions. The intensity is therefore not constant in either the x or y direction. The great advantage of two-dimensional beam modulation is that it enables simultaneous machining of the workpiece. This will be explained below with reference to FIGS. 2a to 2c.

If, for example, the contour of the letter "M" is to be engraved on a workpiece, the entire path along the points 1 → 2 → 3 → 4 → 5 must be carried out in succession or according to FIG be run serial. Such an engraving requires a certain processing time. It would be desirable to shorten the process time, ie to process all areas to be processed simultaneously, ie simultaneously.

Such simultaneous processing allows two-dimensional beam modulation as shown in Fig. 2b and Fig. 2c. The only prerequisite for this is that the letter "M" fits into the active surface ( 5 ) projected onto the workpiece. In this case, the individual cells of the beam modulator can be controlled so that only the contour of the letter "M" is exposed to radiation in the workpiece plane. All of these points are applied simultaneously. Conversely, the cells of the beam modulator can also be controlled in such a way that all points except for the points on the contour are exposed to radiation. The results of these two options correspond to positive ( Fig. 2b) and negative ( Fig. 2c) in photography. With the number of cells per unit area, both the possible resolution of a contour and the effort of addressing the individual cells increase.

The one-dimensional beam modulation allows processing that combines the short process times of simultaneous processing with the flexibility of sequential processing. This workpiece machining or processing with one-dimensional beam modulation is referred to below as quasi-simultaneous machining. You should reference to FIG. 3a and Fig. 3b are explained.

In the quasi-simultaneous material processing, the work is applied pieces such that the elongated focus predetermined parts of the to be processed The workpiece surface moves sequentially (sequentially), and the radiation along the long focus axis is beam or intensity modulated.

Fig. 3a and Fig. 3b respectively show a workpiece to be machined surface (6), which can be imagined divided conceptually into individual partial surfaces (7). Accordingly, the workpiece surface ( 6 ) appears in Fig. 3a and Fig. 3b as a square pattern. In FIG. 3a, the linear focus ( 8 ) with its long axis in the x direction is larger in the x direction than the extent of the working surface in the x direction, ie wider than the width of the letter "M". If the focus line is in the position shown, all points of the contour can be processed simultaneously along the x-direction. As described above, this is done by individually modulating all partial areas ( 7 ) of the linear focus ( 8 ). During machining, the focus and workpiece are shifted relative to each other in the y direction. This is indicated by the vertical double arrows on the left and right edges of Fig. 3a. In this way, the workpiece surface to be machined is machined in succession in the y direction. The same applies analogously if the focus line ( 8 ) is aligned vertically or in the y direction, the relative movement then taking place in the x direction, which is indicated by the horizontal double arrows at the top and bottom of FIG. 3a.

In the sense of the above, it is also sufficient that the linear focus ( 8 ) in the x direction is the same size as the extent of the contour of the letter "M" in the x direction.

However, if the line-shaped focus (8) with its aligned in the x-direction long axis smaller than the extension of the contour of the letter "M" in the x direction, so must the focus (8) as in Fig. 3b not only in the y- Direction, but can also be moved in the x direction. In Fig. 3b, several examples of such foci (8) are shown. The partial areas to which the focal spot is directed depends on the respective process requirements. It may be necessary to scan and machine the entire surface of the workpiece. In this case, rectangular partial areas are particularly advantageous, particularly in the case of diode lasers used, because of their rectangular output LDV. It may also be sufficient for only parts of the entire workpiece surface to be traversed, as in particular in FIG. 3b. The fact that only the predetermined partial areas of the workpiece are traversed and these are machined simultaneously enables the machining speed to be increased considerably.

The electromagnetic radiation leaving the modulating system can ei optically untreated to reach the workpiece level or by means of a beam-guiding and / or beam-shaping optics mapped in the workpiece plane become.

On further optical influencing of the modulated radiation after leaving the modulating system can optionally be dispensed with if the plant brings the part level close to the modulating system, so that any Diffraction or scattering losses and thus resolution losses are kept low. It it makes sense to provide means that contaminate the module system due to particles detached and / or evaporated from the workpiece prevent. So the modulating system can be accommodated in one housing  be, the radiation acting on the workpiece by a for the respective Radiation transparent protective window is coupled out of the housing. Also It is possible to use a cross-air flow (so-called cross-jet), which from the Machining area distracts particles.

It is also possible to use an optical system downstream of the modulation map the generated power density distribution into the workpiece plane. This allows especially an exact adaptation of the dimensions of the LDV to the factory piece dimensions as well as a variation of the working distance.

FIG. 4 shows a block diagram for realizing a spatially resolved one-dimensional beam modulation with the beam modulator according to the invention. The radiation from a diode laser ( 9 ) is homogenized by means of optics ( 10 ) and acts on a beam modulator ( 1 ). The beam modulator consists of an arrangement with 640 strip-shaped nematic liquid crystal cells ( 2 ), each with a width of approximately 97 µm and a distance of 3 µm. The active area ( 5 ) is about 64 mm wide and 7 mm high. The active area is homogeneously illuminated by an upstream homogenization, so that each modulation cell is exposed to approximately the same radiation intensity. The originally emitted diode laser radiation is 90% linearly polarized relative to the pn junction.

At an optical destruction threshold of the liquid crystal arrangement of approximately 150 W / cm ² , the active area is subjected to a power P ₀ of a maximum of 650 W homogeneously. Approximately 70% of P ₀ reach the workpiece surface and form a linear focal spot with the dimensions 30 mm × 1 mm. This leads to a partial intensity of 1400 W / cm ² . A second liquid crystal arrangement with a higher destruction threshold of 500 W / cm ² results in a partial intensity of approximately 4600 W / cm ² . Destruction thresholds of 500 W / cm ² and more are desirable for machining processes with high intensity requirements on the workpiece surface.

The upper half of FIG. 4 corresponds to the view of the entire structure in the front view, ie the view in the direction of the fast axis, while the lower half of the picture shows the same arrangement in plan view or in the direction of the slow axis. The slow axis runs in the x direction and the fast axis runs in the y direction. For reasons of clarity, the repeated representation of the components ( 11 , 12 , 13 , 14 ) has been omitted in the lower half of the figure.

A diode laser arrangement serves as the radiation source ( 9 ). The emitted radiation is first homogenized using an optical system ( 10 ) so that the homogeneous area of the beam modulator ( 1 ) is homogeneously illuminated. Before and after the beam modulator, the power density distributions P (x) and P (y) in the x and y directions are plateau-like (top hat). However, they differ with regard to the polarization in the partial beams. The polarizer ( 3 ) carries out the selection and thus the modulation in accordance with the polarization layers impressed by the strip-shaped liquid crystal modulator ( 1 ).

After the beam modulator ( 1 ), the radiation passes through a polarizer ( 3 ). The beam modulator and the polarizer operating in reflection together form the modulating unit. The unused radiation is absorbed in a beam trap ( 11 ), which is cooled by cooling ( 12 ). In the case of one-dimensional amplitude modulation, there is no modulation along the x direction. Before or after the polarizer, the radiation is focused in the x direction in order to achieve a higher intensity along the linear focus within the workpiece plane ( 6 ). The reduction in focus caused by the focusing in the x direction leads to the fact that P (x) has a smaller half-value width than P (y) after exiting the imaging optics ( 15 ), as can be seen in FIG. 4. In the representation of the power density P (x) present directly in front of the workpiece surface ( 6 ) in FIG. 4, P (x) is parameterized with the y position.

The amplitude modulation takes place exclusively in the y direction (one-dimensional amplitude modulation). After the radiation emerges from the polarizer ( 3 ), P (y) varies accordingly and is adapted to the machining process.

The amplitude modulation is controlled by means of a computer ( 13 ) which electrically controls the beam modulator ( 1 ) via the voltage supply ( 14 ). The computer calculates process-adapted sets of voltage values with which the individual cells are individually acted upon with the aid of an electrical supply ( 14 ) and means for transmitting the electrical addressing signals (not shown). Since the optical axis of the respective liquid crystal cell follows the applied voltage practically without delay, the control unit allows a dynamic adaptation of the LDV to the respective machining requirements during the relative movement of the workpiece and the beam. A downstream imaging optics ( 15 ) images the modulated LDV onto the workpiece surface ( 6 ).

Reference list

1

Beam modulator

2

single (modulation) cell

3rd

Polarizer

4

electromagnetic radiation

5

active surface of the beam modulator, ie surface that can be exposed to radiation

6

Workpiece surface

7

Partial area

8th

Focus (focal spot area)

9

laser

10th

Optics for beam homogenization

11

Beam trap

12th

cooling

13

computer

14

electrical supply

15

Imaging and / or focusing optics

Claims (17)

1. Device for processing materials with electromagnetic radiation ( 4 ), in particular with laser radiation, characterized in that a spatially resolving beam modulator ( 1 ) is provided for generating a predeterminable power density distribution. 2. Device according to claim 1, characterized in that an amplitude and / or phase-modulating beam modulator is provided. 3. Device according to at least one of claims 1 to 2, characterized in that the beam modulator contains an arrangement of individual, the predetermined power density distribution controlling cells ( 2 ). 4. Device according to one of claims 1 to 3, characterized in that the cells ( 2 ) contain a movable micromirror or a micropolarizer or are liquid crystal cells. 5. The device according to claim 4, characterized in that it is in the Liquid crystals around antiferroelectric liquid crystals, in particular around nematic, smectic or cholestric liquid crystals, or ferroelectric Liquid crystals. 6. The device according to at least one of claims 3 to 5, characterized in that the cells ( 2 ) are individually addressable. 7. The device according to at least one of claims 1 to 6, characterized in that the beam modulator ( 1 ) is addressable. 8. The device according to claim 6 or 7, characterized in that an optical or electrical addressability is provided.   9. The device according to at least one of claims 1 to 8, characterized in net that a one- or two-dimensional beam modulation is provided. 10. The device according to at least one of claims 1 to 9, characterized in that an optics ( 10 ) for locally homogeneous exposure of the beam modulator ( 1 ) with the electromagnetic radiation ( 4 ) is provided. 11. A method for material processing with electromagnetic radiation ( 4 ), in particular using a device according to at least one of claims 1 to 10, characterized in that a predetermined power density distribution is generated with a spatially resolving beam modulator ( 1 ). 12. The method according to claim 11, characterized in that a laser beam, and in particular a diode laser or excimer laser beam is modulated in a spatially resolved manner. 13. The method according to at least one of claims 11 to 12, characterized indicates that the beam is modulated in one or two dimensions. 14. The method according to at least one of claims 11 to 13, characterized records that the beam is amplitude and / or phase modulated. 15. The method according to at least one of claims 11 to 14, characterized records that the power density distribution is dynamic during the materialbear processing is adjusted. 16. A method for material processing with electromagnetic radiation ( 4 ), in particular according to a method according to at least one of claims 11 to 15, characterized in that an elongated focus ( 8 ) moves in predetermined parts of the workpiece surface to be machined ( 6 ) in succession, and thereby Radiation ( 4 ) along the long focus axis is beam or intensity modulated. 17. Use of a spatially resolving beam modulator ( 1 ) to generate a predeterminable power density distribution during material processing