Material processing device and method for preparing a material processing device

Abstract

Method for preparing a material processing device (10) for material processing by creating optical openings in or on an object, which has a variable, three-dimensionally acting focus adjustment device (18) for focusing processing laser radiation on different locations in or on the object, - wherein a contact element (20) which is transparent to the processing laser radiation and which is to be placed on the object is attached to the material processing device (10), and which has a contact surface (22) on its side to be placed on the object and an entry surface (24) for the processing laser radiation on its side facing the material processing device (10), - wherein, prior to processing the object, a shape of the contact surface (22) and / or entry surface (24) is determined by means of irradiating the contact surface (22) and / or entry surface (24) with measuring laser radiation (14), by ◯ the measuring laser radiation (14) is focused near or onto the contact surface (22) and / or entrance surface (24) by means of the variable focus adjustment device (18), wherein the energy density of the focused measuring laser radiation (14) is too low to generate an optical breakthrough, ◯ Radiation backscattered or backreflected from the focus of the measuring laser radiation (14) is detected confocally, ◯ from the confocally detected radiation and the associated setting of the variable focus adjustment device (18) a position of intersection points on the contact surface (22) and / or entrance surface (24) is determined, and ◯ a three-dimensional surface model is adapted to the determined location of the intersection points, whereby the surface model provides the 3-dimensional shape of the contact surface (22) and / or entry surface (24).

Description

[0001] The invention relates to a method for preparing a material processing device for material processing by creating optical openings in or on an object, and to a material processing device configured to carry out the method. Furthermore, the invention relates to a computer program comprising commands that cause the material processing device to carry out the method, and to a computer-readable medium on which the computer program is stored.

[0002] In material processing, a laser is often focused on the areas of an object to be processed. This involves using processing laser radiation with an intensity high enough to create optical breakthroughs. To focus the processing laser radiation onto predetermined positions, it is generally essential that the object is aligned and held in a precisely defined position relative to the laser beam. A contact element is typically used to hold the object in this precise position, thus enabling defined conditions. The contact element therefore becomes part of the beam path of the processing laser radiation.

[0003] This is particularly necessary for the micromachining of materials that exhibit only low linear optical absorption in the spectral range of the laser radiation being processed, or for the creation of structures within the object, especially in laser-induced refractive index changes (LIRIC). With such materials, non-linear interactions between the laser radiation and the material are typically exploited, usually in the form of an optical breakthrough created at the focus of high-energy laser radiation. Since the processing effect then only occurs at the laser beam focus, it is crucial to precisely align the focus in three dimensions. Therefore, in addition to two-dimensional deflection of the laser beam, precise depth adjustment of the focus position is required.The contact element serves to ensure constant and also known with a certain degree of accuracy optical conditions in the beam path to the object, by mechanically coupling the object and the laser processing device through the contact element and also providing the object surface with a shape with a known optical effect.

[0004] A typical application for such a contact element is in ophthalmic procedures, particularly ablation and / or photodisruption and / or laser-induced refractive index change (LIRIC), where the contact element, which may comprise, for example, glass, plastic, PMMA, and / or polymers, should be transparent, at least to the processing laser beam. The material processing device is equipped with an ophthalmic laser that focuses laser radiation into the cornea. An optical breakthrough can occur at the focus, causing a local separation of the corneal tissue. By appropriately arranging these optical breakthroughs, corneal layers can then be ablated or a corneal volume isolated and removed.

[0005] The shape and position of the contact element are crucial for accuracy in such material processing, with the position of the contact element relative to the material processing device being determined after coupling to it and before material processing during the preparation of the material processing device. The basic shape of the contact element is usually known, although it may deviate slightly from a specified shape.

[0006] From publication DE 10 2006 046 370 A1, a device and a method for material processing using a transparent contact element are known; from publication DE 10 2006 036 800 A1, a device for individual therapy planning and position-accurate modification of an optical element is known; and from publication EP 2 349 149 B1, an ophthalmological laser system is known.

[0007] Furthermore, WO 2008 / 040 436 A1 discloses a generic device and a method for preparing the device for material processing by creating optical openings in or on an object. The device has a variable, three-dimensionally acting focus adjustment device for focusing pulsed processing laser radiation onto different locations in or on the object. A contact element, transparent to the processing laser radiation and placed on the object, is attached to the device and has a curved contact surface of a previously known shape on its side that rests on the object. Before processing the object, the position of the contact surface relative to the focus adjustment device is determined by irradiating the contact surface with measuring laser radiation by focusing the measuring laser radiation near or onto the contact surface using the variable focus adjustment device.The energy density of the focused measuring laser radiation is too low to generate an optical breakthrough, and the focus position of the measuring laser radiation in a measuring surface is adjusted such that it intersects the expected position of the contact surface, wherein backscattered or reflected radiation from the focus of the measuring laser radiation is detected confocally, wherein the position of intersection points between the measuring surface and the contact surface is determined from the confocally detected radiation and the associated setting of the variable focus adjustment device, wherein the position of the contact surface is determined from the position of the intersection points and the previously known shape of the contact surface.

[0008] A disadvantage of determining the position of the contact element in this way is that its exact shape must be known beforehand in order to calculate the position of the contact surface from the points of intersection. However, contact elements can have certain tolerances that can distort such a position determination.

[0009] Therefore, the object of the present invention is to improve the preparation of the material processing device, in particular to avoid the disadvantages of the prior art.

[0010] This problem is solved by the inventive method, the inventive devices, the inventive computer program, and the inventive computer-readable medium. Advantageous embodiments with expedient further developments of the invention are specified in the respective dependent claims, wherein advantageous embodiments of the method are to be regarded as advantageous embodiments of the treatment device, the control device, the computer program, and the computer-readable medium, and vice versa.

[0011] The invention is based on the idea that the shape of the contact element, in particular a contact surface and / or entry surface, and thus its position relative to the processing laser radiation, can be determined directly using measuring laser radiation without needing to know the exact shape beforehand. For this purpose, a plurality of intersection points of the laser radiation with the contact surface and / or entry surface can be determined, from which the shape can then be calculated.

[0012] The invention provides a method for preparing a material processing device for material processing by creating optical openings in or on an object. The material processing device has a variable, three-dimensionally acting focus adjustment device for focusing processing laser radiation onto different locations in or on the object, wherein a contact element, transparent to the processing laser radiation, is attached to the material processing device and is placed on the object. This contact element has a contact surface on its side facing the object and an entry surface for the processing laser radiation on its side facing the material processing device.Before processing the object, the shape of the contact surface and / or entry surface is determined by irradiating the contact surface and / or entry surface with measuring laser radiation. This is done by focusing the measuring laser radiation near or onto the contact surface and / or entry surface using the variable focus adjustment device. If the energy density of the focused measuring laser radiation is too low to generate an optical breakthrough, backscattered or backreflected radiation from the focus of the measuring laser radiation is detected confocally. From the confocally detected radiation and the associated setting of the variable focus adjustment device, the position of intersection points on the contact surface and / or entry surface is determined, and a three-dimensional surface model is fitted to the determined position of the intersection points. The surface model provides the 3-dimensional shape of the contact surface and / or entry surface.

[0013] In other words, the material processing device can include one or more lasers, wherein the laser(s) are configured to provide processing laser radiation capable of creating optical breakthroughs in the object. Furthermore, the laser(s) can be configured to provide measurement laser radiation whose energy is too low to create optical breakthroughs. The measurement laser radiation can preferably be focused onto the contact surface and / or entry surface of the contact element by the same focus adjustment device used to focus the processing laser radiation. The contact element, which is transparent to the processing laser radiation, can be pre-coupled to the material processing device so that it is in the beam path of the processing laser radiation and / or the measurement laser radiation.

[0014] In particular, a refractive index change can occur at the interface between air and the contact surface and / or entrance surface of the contact element. This allows backscattered or backreflected radiation to be distinguished from focused radiation in air and / or within the contact element. This enables the determination of intersection points of the measurement laser radiation on the contact surface and / or entrance surface, especially using confocal measurement. Confocal detection of backscattered or reflected measurement laser radiation advantageously utilizes the fact that the proportion of transmitted radiation backscattered at the interface of a transparent medium and detected confocally is significantly higher than the proportion within the transparent contact element.Confocal detection, through the spatial filtering that occurs, provides a sufficient signal whose strength depends essentially on the refractive index difference of the media adjacent at the contact surface. The principle of confocal measurement is known from the prior art.

[0015] Once the location of intersection points on the contact surface and / or entry surface has been determined, a three-dimensional surface model can be fitted to the determined location of these intersection points. This means that, for example, mathematical models can be fitted to the intersection points to determine the shape of the contact surface and / or entry surface. Therefore, it is not necessary to know the shape of the contact surface and / or entry surface beforehand to determine the position of the contact element relative to the material processing device. This method allows the shape of the respective surface to be directly determined within the coordinate system of the material processing device or the processing laser beam, thus simultaneously revealing the position of the contact element.It is evident to a person skilled in the art that increasing the number of intersection points leads to a more accurate determination of the three-dimensional shape of the contact surface and / or the entry surface. Therefore, for this application, a person skilled in the art will seek a sufficient number of intersection points and / or, if necessary, repeat the irradiation with measuring laser radiation until a sufficiently high number of intersection points is found. Preferably, if a basic shape of the contact element is known, a suitable distribution of the measuring laser radiation, and thus of the intersection points, can also be selected to scan this shape.

[0016] The processing laser radiation and / or measuring laser radiation can preferably be pulsed laser radiation, wherein an energy range of the measuring laser radiation is below an energy for optical breakthrough, in particular below one joule per square centimeter or a power density per pulse below 10 9 Watts per square centimeter.

[0017] The invention offers the advantage of improving preparation for material processing by eliminating the need for prior knowledge of the contact element, since the method allows the shape and thus the position relative to the material processing device or the processing laser radiation to be determined directly. In particular, irradiation planning can then be adapted to the determined shape.

[0018] The invention also includes embodiments that offer additional advantages.

[0019] One implementation involves creating a grid structure based on the location of the intersection points on the contact surface and / or the entry surface. Polygons are then fitted to this grid structure to form the three-dimensional surface model. This means that the measuring laser beam scans a space containing the contact surface and / or the entry surface, with the confocally detected intersection points representing the respective surface as a three-dimensional grid structure. Polygons can then be fitted to this grid structure to create the three-dimensional shape of the respective surface. These polygons can be generated, for example, by connecting the intersection points that form the grid structure, particularly adjacent intersection points, so that a closed surface is created between the grid points.This can preferably be carried out for all grid points of the grid structure in order to obtain the shape of the respective surface using a closed polygon. Thus, the three-dimensional shape of the respective surface in space can be determined in a simple way.

[0020] Another embodiment provides that polynomials, in particular a polynomial chain, are fitted to the intersection points on the contact surface and / or the entry surface. In other words, a function consisting piecewise of polynomials of degree n, for example, bicubic, can be fitted to the intersection points. Such splines (polynomial chain) can then be used to interpolate the intersection points and the intervening surface, thus providing the three-dimensional shape of the contact surface and / or entry surface. Preferably, this can be done by fitting algorithms that use the intersection points in one or more planes to fit the polynomials. This offers the advantage of providing a further preferred embodiment.

[0021] Another approach involves fitting Zernike polynomials or a Fourier series to the intersection points on the contact surface and / or entry surface as a three-dimensional surface model. This means that Zernike polynomials, in particular, can be fitted to the intersection points to provide smooth and derivable surfaces. Zernike polynomials are used to represent wavefronts, especially in ophthalmology, where determining the three-dimensional shape of the contact surface and / or entry surface using Zernike polynomials is particularly suitable for contact elements in ophthalmology. Alternatively, a Fourier series can be fitted to the intersection points, where the Fourier series is a periodic, piecewise continuous function consisting of sine and cosine functions.This design allows for the creation of further suitable three-dimensional surface models for determining the three-dimensional shape of the contact surface and / or entry surface.

[0022] Another embodiment involves focusing the measuring laser radiation near or onto the contact surface and / or entry surface according to a predefined scanning strategy. This means that a scanning strategy can be provided to obtain a sufficient number of intersection points with the contact surface and / or entry surface to adapt the three-dimensional surface model. Depending on the three-dimensional surface model used, a different scanning strategy can be employed. For example, a sufficient number of intersection points can initially be sought, and if a threshold is not met, a measurement can be repeated, particularly with a modified scanning area, until enough intersection points are achieved. Specifically, the person skilled in the art will determine the required number of intersection points for the respective three-dimensional surface model used based on experience and / or experiments.The desired accuracy in determining the three-dimensional shape and the required intersection points are also adjusted by a person skilled in the art according to the required precision. For example, hexagonal, rectangular, and / or circular grids can be used as predefined scanning strategies. Alternatively or additionally, an Albrecht distribution, a Jacobi distribution, and / or a Legendre distribution can be used to scan an area. Preferably, one of the aforementioned grids or distributions can be scanned in an xy-plane, followed by adjusting the z-position (depth direction) and scanning the next plane again using one of these scanning strategies. This can be repeated for several z-positions until a sufficiently large number of intersection points are found.

[0023] Preferably, the focal points of the measuring laser radiation are distributed uniformly within a spatial region where the contact surface and / or entry surface is expected, according to the scanning strategy. Thus, the focusing device in the scanning strategy can focus the measuring laser radiation directly into the areas where, based on experience, the contact surface and / or entry surface are expected. The focal points of the measuring laser radiation can then be distributed uniformly within this three-dimensional spatial region to detect confocal intersection points.

[0024] Particularly preferred is the scanning strategy in which the focus adjustment device is set to focus the measuring laser radiation to an xy-position located in a plane perpendicular to the emission direction of the focus adjustment device. In this xy-position, several focus points are scanned along a z-axis that lies on a depth axis relative to the focus adjustment device. According to this scanning strategy, several different xy-positions are measured iteratively, with each subsequent scan along the z-axis. In other words, several successive points can be scanned along the depth direction, for example, the direction leading from the entrance surface to the contact surface. The position in the plane can then be adjusted, and the depth direction can be scanned again in this new position.This can be done for several xy positions in the plane until a sufficiently high number of intersections with the contact surface and / or the entry surface are determined.

[0025] In a further advantageous embodiment, the scanning strategy provides that the focus adjustment device is set to focus the measuring laser radiation to a z-position located on a depth axis parallel to the emission direction of the focus adjustment device. At this z-position, several different xy-positions, lying on an xy-plane perpendicular to the emission direction of the focus adjustment device, are scanned according to a grid, a spiral, and / or concentric circles. According to this scanning strategy, several different z-positions are measured iteratively, with each subsequent scan of the xy-plane. In other words, this embodiment defines a plane in the depth direction, and this plane, which is spanned in the xy-direction, is then scanned.A grid can be used, preferably one of the grids or distributions mentioned above. A spiral path can be scanned from the inside out or from the outside in within this area, and / or several concentric circles can be scanned to obtain intersections with the contact surface and / or entry surface. The position in the depth direction can then be changed, meaning that a next level is addressed, where this scanning strategy is repeated. After addressing several different z-positions, a space or volume can thus be scanned to obtain the intersections with the contact surface and / or entry surface.

[0026] Preferably, the scanning strategy involves scanning one or more helical curves. This means that a measurement path for the laser radiation can be provided, which helically or as a helix scans a space where the contact surface and / or the entry surface is expected. After scanning a helical curve once, for example, the radius of the helical curve can be changed and a new scan can be performed. Thus, for example, several different radii can be used iteratively to scan helical curves in order to scan the space containing the contact surface and / or the entry surface.

[0027] Preferably, the scanning strategy provides for one or more planes that are inclined relative to the focus adjustment device to be scanned. In other words, the focus adjustment device can use both the xy-axis and the z-axis control to scan a measuring plane that is inclined in space.

[0028] Another advantageous embodiment involves increasing the density of sampling points in the vicinity of an intersection point after that point has been located. Specifically, the density of sampling points in the vicinity of the intersection point can be increased compared to focus points where no intersection point is found. In other words, by finding at least one intersection point, an approximate location of the respective surface can be determined, and the sampling around this intersection point can then be refined, for example, by doubling it, to obtain enough intersection points for fitting the three-dimensional surface model. This embodiment offers the advantage of accelerating the process.

[0029] Preferably, it can also be provided that, if a basic shape of the contact element is known, the measuring laser radiation is adjusted along a surface expected from the basic shape, preferably with predetermined variances, in order to increase the number of intersection points. This allows the determination of the surface shape to be accelerated and / or improved.

[0030] Another embodiment provides that the measuring laser radiation is supplied by a laser radiation source that is also intended for generating the processing laser radiation. Thus, the material processing device preferably comprises only one laser capable of generating processing laser radiation and, for example, providing measuring laser radiation by reducing its laser energy, particularly through an energy attenuator. This embodiment offers the advantage that the use of a separate laser for generating the measuring laser radiation can be dispensed with, thereby saving costs.

[0031] Particularly preferred is the material processing device for preparation for laser eye treatment. In other words, the material processing device can be a treatment device for treating a human or animal eye, wherein a contact element for fixing the eye for treatment by the method is measured and its contact area and / or entry area is determined.

[0032] Another aspect of the invention relates to a material processing device, in particular comprising at least one ophthalmic laser for treating a human or animal eye, and a contact element that can be fixed thereto. The treatment of the eye can, for example, include the separation of a lenticule from a cornea with predefined interfaces by means of optical openings and / or corneal ablation and / or a laser-induced change in the refractive index. The material processing device can therefore be configured to perform a method according to one of the preceding embodiments.

[0033] In other words, the material processing device can be designed as a treatment device with at least one ophthalmic laser, at least one focus adjustment device or beam deflection device, and a fixing device, wherein, for example, a control unit of the material processing device can be designed to carry out a method according to one of the preceding embodiments.

[0034] The control unit or control device can be designed, for example, as a control chip, control unit, or application program ("app"). The control device can preferably include a processor and / or a data storage device. A processor is understood to be a device or device component for electronic data processing. The processor can, for example, include at least one microcontroller and / or at least one microprocessor. The optional data storage device can preferably contain program code for executing the method. The program code can be designed, when executed by a processor, to cause the control device to perform one of the described configurations of the method.

[0035] Preferably, the laser is capable of emitting laser pulses in a wavelength range between 300 nanometers and 1400 nanometers, preferably between 700 nanometers and 1200 nanometers, with a pulse duration between one femtosecond and one nanosecond, preferably between ten femtoseconds and ten picoseconds, and a repetition frequency greater than ten kilohertz, preferably between 100 kilohertz and 100 megahertz. Such a femtosecond laser is particularly well suited for the fabrication of volume structures within the cornea.

[0036] The material processing device may preferably include the control unit with at least one storage device for at least temporary storage of at least one control data set, wherein the control data set(s) may include control data for positioning and / or focusing individual laser pulses into the cornea and / or the contact element.

[0037] Further features and their advantages can be found in the descriptions of the invention aspects, whereby advantageous embodiments of each invention aspect are to be regarded as advantageous embodiments of the other invention aspect.

[0038] Another aspect of the invention relates to a computer program comprising commands that cause the material processing device to perform process steps according to one of the preceding embodiments.

[0039] According to the invention, a computer-readable medium is also provided on which the computer program according to the preceding aspect of the invention is stored. This offers the same advantages and possibilities for variation as the other aspects of the invention.

[0040] Further features of the invention are evident from the claims, the figures, and the description of the figures. The features and combinations of features mentioned above in the description, as well as those subsequently mentioned in the description of the figures and / or shown in the figures alone, are not only usable in the combinations specified, but also in other combinations without departing from the scope of the invention. Thus, embodiments that are not explicitly shown and explained in the figures, but which can be derived and generated from the explained embodiments by separate combinations of features, are also to be considered as encompassed and disclosed by the invention. Embodiments and combinations of features that do not exhibit all the features of an originally formulated independent claim are also to be considered disclosed.Furthermore, embodiments and combinations of features, in particular those set out above, are to be considered disclosed which go beyond or deviate from the combinations of features set out in the cross-references of the claims. This shows:

[0041] This shows: Fig. 1 a schematic representation of a material processing device according to an exemplary embodiment; Fig. 2 schematic patterns for a sampling strategy.

[0042] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0043] In Fig. Figure 1 is a highly schematic representation of a material processing device 10, in particular a treatment device 10, for treating an eye. The material processing device 10 includes a laser 12 configured to generate processing laser radiation, wherein the processing laser radiation can create optical breakthroughs in an object (not shown) for processing the object. Furthermore, the laser 12 can be configured to generate measurement laser radiation 14, wherein the energy of the measurement laser radiation is below the energy required for an optical breakthrough, in particular below 1 joule per square centimeter. Preferably, the material processing device 10 and the laser 12 can be provided for laser eye treatment.

[0044] In addition to the laser 12, the material processing device 10 can have a control unit 16, which can be configured to control the laser 12 by means of control data, so that it can emit pulsed laser pulses, for example for the treatment of an eye. Furthermore, the control unit 16 can control a three-dimensionally acting focus adjustment device 18, so that the focus adjustment device 18 focuses the processing laser beam and / or the measuring laser beam 14 to predetermined positions, in particular positions in or on the object and / or a contact element 20, as specified by control data.

[0045] The laser 12 is preferably a photodisruptive and / or ablative laser configured to emit laser pulses in a wavelength range between 300 nm and 1400 nm, preferably between 700 nm and 1200 nm, with a pulse duration between 1 fs and 1 ns, preferably between 10 fs and 10 ps, ​​and a repetition frequency greater than 10 kHz, preferably between 100 kHz and 100 MHz. The control device 16 optionally also includes a storage device (not shown) for at least temporarily storing at least one control data set, wherein the control data set(s) comprise control data for positioning and / or focusing individual laser pulses.

[0046] Furthermore, the material processing device 10 can include a contact element 20 that is transparent to the processing laser radiation. The contact element 20 can preferably be attached to the material processing device 10. The contact element 20 can be designed to fix an object, for example an eye, in a position for processing with the laser 12. For this purpose, the contact element can have a contact surface 22, which is a side of the contact element 20 that is placed on the object. The contact surface 22 preferably has a shape adapted for processing the object, whereby in the case of eye treatment, a convex shape, for example a semicircle, can be provided. On the side facing the material processing device 10, the contact element 20 can have an entry surface 24 through which the laser radiation passes through the contact element 20, which is transparent to the processing laser radiation.

[0047] To prepare the material processing device 10, the shape of the contact surface 22 and / or the entry surface 24 can be determined after the contact element has been attached. For this purpose, the laser 12 can focus measuring laser radiation 14 onto the contact surface 22 and / or the entry surface 24 using the focus adjustment device 18, whereby a reflection signal is generated at a refractive index transition on the respective surface, which can be measured as the intersection point with the contact surface 22 and / or the entry surface 24. This measurement of the backscattered and / or backreflected radiation can preferably be performed confocally, wherein, in the reverse direction of the beam path, the backscattered or backreflected radiation is emitted back into the material processing device 10 by the focus adjustment device 18, and this backscattered or backreflected radiation can be measured by a detector 28 via a beam splitter 26.A pinhole 30 can be arranged in front of the detector 28 so that only the back-reflected radiation originating from the focal point of the focus adjustment device is measured. Since the principle of confocal measurement is known, further details of the optical components of the confocal measurement are not described for the sake of clarity.

[0048] After detection of the backscattered or backreflected radiation by the detector 28, the associated setting of the variable focus adjustment device 18 can be used to determine the location of intersection points on the contact surface 22 and / or the entrance surface 24.

[0049] If the position of the intersection points on the contact surface 22 and / or the entry surface 24 of the contact element 20 is known, a three-dimensional surface model can be adapted or fitted to it, for example by the control device 16, whereby the surface model provides the three-dimensional shape of the contact surface 22 and / or the entry surface 24.

[0050] For example, polygons can be fitted to the determined intersection points with the respective surface, which may be in the form of a grid structure, and these polygons together yield the three-dimensional shape. Alternatively or additionally, polynomials or a polynomial chain (splines) can be fitted to the intersection points of the contact surface 22 and / or entry surface 24, which together yield the shape of the respective surface. Zernike polynomials or Fourier series can also be fitted to the intersection points of the respective surface, which are particularly preferred for determining the shape.

[0051] To obtain a sufficient number of intersection points with the contact element 20, it is also preferably possible to use a predefined scanning strategy that focuses the measuring laser radiation 14 near or on the contact surface 22 and / or the entry surface 24. The scanning strategy can also define a density, specifying how many focal points are scanned in a spatial region where the contact surface 22 and / or the entry surface 24 are expected. Exemplary grids or distributions that can be used for the scanning strategy are shown in Fig. 2 shown.

[0052] For example, hexagonal distributions can be used as a sampling strategy, as in the grid R1 of the Fig. Figure 2 illustrates this. Alternatively, rectangular grids can be used as the sampling strategy, as shown in Grid R2. Other possibilities include circular grids R3, an Albrecht distribution R4, a Jacobi distribution R5, and / or a Legendre distribution R6.

[0053] Particularly advantageous is the use of confocal measurement to first locate an intersection point with the contact surface 22 and / or the entry surface 24, whereby the density of sampling points is increased in the area where the intersection point is found to obtain an improved resolution of the respective surface. It is also possible to scan the respective surfaces plane by plane, meaning that an xy-surface is scanned, then a z-position (depth direction) is changed, and the xy-surface is measured again at this z-position. For example, the following can be used in this way: Fig.The grids shown in the two diagrams can be used, and / or a spiral and / or concentric circles can be scanned. Instead of scanning plane by plane in the xy direction, scanning can also be performed in the respective z direction, whereby the xy position is subsequently adjusted and the corresponding z direction is scanned. Further scanning strategies include helical curves, in particular with a variable radius, and / or planes lying obliquely to the focus adjustment device 18, which intersect the contact surface 22 and / or the entrance surface 24.

[0054] Overall, the examples show how, without prior knowledge of the exact parameters of the contact element 20, the shape of the contact surface 22 and / or the entry surface 24 can be determined in order to prepare the material processing device 10 for processing an object.

Claims

[1] Method for preparing a material processing device (10) for material processing by creating optical openings in or on an object, which has a variable, three-dimensionally acting focus adjustment device (18) for focusing processing laser radiation on different locations in or on the object, - wherein a contact element (20) which is transparent to the processing laser radiation and which is to be placed on the object is attached to the material processing device (10), and which has a contact surface (22) on its side to be placed on the object and an entry surface (24) for the processing laser radiation on its side facing the material processing device (10), - wherein, prior to processing the object, a shape of the contact surface (22) and / or entry surface (24) is determined by means of irradiating the contact surface (22) and / or entry surface (24) with measuring laser radiation (14), by ◯ the measuring laser radiation (14) is focused near or onto the contact surface (22) and / or entrance surface (24) by means of the variable focus adjustment device (18), wherein the energy density of the focused measuring laser radiation (14) is too low to generate an optical breakthrough, ◯ Radiation backscattered or backreflected from the focus of the measuring laser radiation (14) is detected confocally, ◯ from the confocally detected radiation and the associated setting of the variable focus adjustment device (18) a position of intersection points on the contact surface (22) and / or entrance surface (24) is determined, and ◯ a three-dimensional surface model is adapted to the determined location of the intersection points, whereby the surface model provides the 3-dimensional shape of the contact surface (22) and / or entry surface (24). [2] Method according to claim 1, wherein a grid structure is provided by the position of the intersection points on the contact surface (22) and / or the entry surface (24), wherein polygons are adapted to the grid structure as the three-dimensional surface model. [3] Method according to one of the preceding claims, wherein polynomials, in particular a polynomial train, are adapted to the intersection points on the contact surface (22) and / or the entry surface (24). [4] Method according to one of the preceding claims, wherein Zernike polynomials or a Fourier series are fitted to the intersection points on the contact surface (22) and / or entry surface (24) as a three-dimensional surface model. [5] Method according to one of the preceding claims, wherein the measuring laser radiation (14) is focused near or onto the contact surface (22) and / or entry surface (24) according to a predetermined scanning strategy. [6] Method according to claim 5, wherein focal points of the measuring laser radiation (14) are distributed uniformly in a spatial area in which the contact surface (22) and / or entry surface (24) is expected according to the scanning strategy. [7] Method according to claim 5 or 6, wherein, according to the scanning strategy, the focus adjustment device (18) is set to focus the measuring laser radiation (14) on an xy position which lies in a surface perpendicular to the direction of emission of the focus adjustment device (18), and in this xy position several focus points are scanned along a z-axis which lies on a depth axis with respect to the focus adjustment device (18), wherein, according to this scanning strategy, several different xy positions are measured iteratively with each subsequent scanning along the z-axis. [8] Method according to one of claims 5 or 6, wherein, according to the scanning strategy, the focus adjustment device (18) is set to focus the measuring laser radiation (14) on a z-position which lies in a depth axis parallel to the emission direction of the focus adjustment device (18), and in this z-position several different xy-positions which lie in an xy-surface perpendicular to the emission direction of the focus adjustment device (18) are scanned according to a grid, a spiral and / or concentric circles, wherein, according to this scanning strategy, several different z-positions are measured iteratively with each subsequent scanning of the xy-surface. [9] Method according to one of claims 5 or 6, wherein one or more helix curves are sampled according to the sampling strategy. [10] Method according to one of claims 5 or 6, wherein, according to the scanning strategy, one or more planes inclined with respect to the focus adjustment device (18) are scanned. [11] Method according to any one of claims 5 to 10, wherein after finding an intersection point, the density of sampling points in the vicinity of the intersection point is increased. [12] Method according to one of the preceding claims, wherein the measuring laser radiation (14) is provided from a laser radiation source (12) which is also intended for generating the processing laser radiation. [13] Method according to one of the preceding claims, wherein the material processing device (10) is prepared for laser eye surgery. [14] Material processing device (10), in particular comprising at least one ophthalmic surgical laser (12) for the treatment of a human or animal eye, and a contact element (20) that can be fixed thereto, wherein the material processing device (10) is configured to carry out a method according to one of the preceding claims. [15] Computer program comprising commands that cause the material processing device (10) according to claim 14 to perform the process steps according to any one of claims 1 to 13. [16] Computer-readable medium on which the computer program according to claim 15 is stored.

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