Method and device for determining a spatial position of a non-spherical object

Abstract

Method for determining a spatial position of a non-spherical object (110) having at least one surface portion (111) of known shape, comprising the following steps: a) irradiating at least two light fields (100) through an objective lens (70) onto the object (110), each light field (100) having known phase fronts (104), the phase fronts (104) of the at least two light fields (100) differing from one another at least downstream of the objective lens (70), a curvature of the phase fronts (104) at an exit window of the objective lens (70) being less in at least one spatial direction than a smallest curvature of the surface section (111) of the object (110), for at least one of the light fields (100) there being at least one line lying in the surface section (111), along which line at least two local surface normals (112) of the surface section (111) are orthogonal to the phase front (104) of at least one of the light fields (100); b) detecting a reflected portion (102) of the at least two light fields (100) emanating from the object (110) by means of a detector (80); and c) determining the spatial position of the non-spherical object (110) from the detected reflected portion (102) of the at least two light fields (100), taking into account an expected backscatter signal resulting from the known shape of the surface section (111).

Description

Field of the InventionThe present invention relates to a method and a device for determining a spatial position of a non-spherical object and to an associated computer program. In many applications, the object is a cylindrical object, particularly a glass fiber; however, the use of another object is possible.Prior ArtThe present invention is located in the field of photonics, in particular in the field of the construction and connection technology of optical components. The challenge in this area is to effectively couple light from the outside into an optical component or to couple it out from an optical component to the outside. In this case, glass fibers, i.e. optical waveguides comprising a glass fiber core and a glass fiber cladding, are a basic module. They are designed to guide light effectively by utilizing an optical refractive index difference between the optical fiber core and the optical fiber cladding. However, in order to guide the light onto or away from an optical component, it is necessary to provide for the coupling or decoupling of the light from or into the glass fiber. The coupling of a glass fiber to an optical component, in particular a laser, a photonic integrated circuit (PIC) or a photodetector, can be effected in different ways; preferablyby direct mechanical coupling of the glass fiber (butt coupling);via an optical free-beam path by means of optical elements, in particular optical lenses or mirrors: or3D printed free-form waveguides (photonic wire bonds).There are different challenges for each of these coupling mechanisms.In the case of direct mechanical coupling, it is necessary to position the optical fiber exactly and to adapt a mode field on one side of the optical component to the mode field of the optical fiber. If the mode field of the optical component is not matched to the mode field of the glass fiber, optical lenses and collimator optics must be attached for the free-beam path, which also require a high-precision alignment. Prior art for positioning the glass fiber for light coupling is an active coupling (active alignment), in which a mechanical gripper moves the glass fiber spatially while simultaneously light is coupled in with a laser at one end of the glass fiber and the output signal is monitored with a photodiode. The higher the power in the photodiode, the better the coupling. If the coupling is satisfactory, the gripper is stabilized and the glass fiber is bonded. This procedure entails several disadvantages, on the one hand it is very time-consuming, on the other hand it involves continuous wear of the installations, furthermore it comprises a mechanically problematic adhesion of the glass fibres, and finally the optical path of the optical component must be accessible in order to be able to measure an injected signal on the photodiode. Another possibility for carrying out a direct coupling of an optical fiber to a chip without active coupling is the use of V-shaped etched trenches (engl. V-grooves) on the chip by aligning the glass fibre with the waveguide on the chip by mechanical limitations of the trenches during insertion. However, this procedure requires a higher outlay on the chip side. The mode field must be matched on the chip, and the trenches require valuable chip area. Furthermore, this form of coupling requires very tight tolerances in the production of the trenches and the diameter of the glass fiber, which are often not present in practice.In general, it is advantageous, in particular with regard to the outlay and speed of the procedure, not to actively perform the coupling of the glass fiber to the optical component, i.e. without measuring light through the glass fiber on a detector, in order to optimize for a signal. Passive coupling requires that the positions of the coupling points of a light inlet and a light outlet of glass fiber and the optical component, e.g. the PIC, are measured very accurately and an optical connection is established between the glass fiber and the optical component on the basis of this measured information. A determination of the position and orientation of a glass fiber core in space is often made more difficult by the fact that the facet of the glass fiber is not accessible and / or the glass fiber is embedded in a glass fiber array.When using free-form waveguides as an alternative to active coupling, an optical connection is established between two optical components by means of direct writing 3D lithography. In this case, it is likewise necessary to determine the position and orientation of the optical components exactly. This approach has an additional difficulty in that the optical fiber must be detected while it is installed in a two-photon lithography apparatus. Therefore, there are only limited possibilities for viewing the glass fiber from different sides by means of a classic imaging method. Typically, a system for two-photon lithography only comprises the possibility of viewing the optical components and / or the glass fiber from above by means of a camera or scanning it by means of a laser beam.In particular when using direct writing two-photon lithography, it is often necessary to determine the exact position and orientation of one or more objects, in particular in order to write at least one optical element to an object with precise alignment. An application can be selected in particular from a detection of the position and orientation of waveguides, coupling points or surfaces of optical components, preferably of glass fibers, optical chips or lasers. According to the prior art, imaging methods, preferably a camera, are used for this purpose, which can record images through an objective of a lithography system and can determine information about the position and the orientation by a suitable procedure, in particular by recording the optical component in different sectional planes (focus stacking). In principle, an optical element such as a glass fibre core can be detected by means of a microscope or by means of an optical system in a direct writing lithography system on the basis of the difference in refractive index between the glass fibre core and the glass fibre cladding, but undefined background illumination, as can occur in particular in the case of non-transparent structures, can lead to a low signal-to-noise ratio and thus to low reproducibility. In addition, in the case of a complex arrangement, the glass fibres can be arranged, for example, in a groove of V-shaped cross section (narrow. V-grove) cannot be unambiguously defined as to how the signal behaves, so that here the detection by means of classic imaging in a microscope can be carried out only to a very limited extent.In order to determine the exact position and orientation of a glass fiber, for example in a splicing device, special illumination is often used according to the prior art. U.S. Pat. No. 4,492,463 A discloses that for this purpose the glass fiber is illuminated from one side and the deflection of the light through the glass fiber on the opposite side is detected in transmitted light, wherein the glass fiber or the associated glass fiber core acts as an optical lens in this case. However, this method can only be used if the glass fiber is optically accessible from two opposite sides. This is usually not the case in particular in the case of completely assembled optical components, since here the glass fiber is typically attached to a metal or a silicon substrate. Another hurdle entails glass fibre arrays which have been glued into a glass block for better handling. The glass block can distort the course of the light and thus prevent a detection of the glass fiber in transmitted light. In a lithography system for producing photonic connections, a positioning table or a platform is often used, on which the optical components provided for the connection are placed. Cameras mounted on opposite sides would greatly restrict the size of the optical components. In addition, there is a high outlay in arranging the cameras in the integrated structure in a mechanically movable manner, with the result that higher wear of the lithography system is to be expected.U.S. Pat. No. 4,506,947 A or U.S. Pat. No. 4,690,493 A disclose that the glass fiber is irradiated with ultraviolet light and the associated glass fiber core is excited to fluorescence, wherein the fluorescent light thus generated is evaluated. However, this method can only be used if the optical component can be exposed to ultraviolet radiation. This is not possible when 3D lithography is used with a UV-sensitive photoresist, because it cures under UV irradiation. A further limitation of this method is the absolutely necessary difference in fluorescence between the glass fiber core and the glass fiber jacket.Furthermore, methods are known which use confocal microscopy for detecting objects. HOVIS, e.g.; Heauer, A.H.: The use of laser scanning confocal microscopy (LSCM) in materials science. In: Journal of Microscopy, Vol. 240, 2010, No. 3, pp. 173-180. - issn 0022-2720 (p); 1365-2818 (e). DOI: 10.1111 / j.1365-2818.2010.03399.x describes a classic confocal microscope which has a focal point which can be moved by means of galvanometric scanners. In classic confocal microscopy or in laser scanning confocal microscopy, by scanning the surface by means of the focal point, either the surface reflection of an object or the fluorescence of the object to be detected or of the environment is used to generate image data. A classic confocal microscope can also be used in a direct writing lithography system; in this case, an exposure laser can be used for a confocal measurement, wherein a laser intensity is typically selected below the polymerization threshold. This makes it possible to detect the surface of optical components, e.g. waveguides, or of associated coupling points, e.g. in optical chips or lasers. Objects such as optical components or substrates with and without topography can be detected by means of a confocal scan, provided they have a certain reflectivity. However, in a simple confocal scan using a beam focused on the surface of an optical fiber, there is a problem that the lateral position of the axis of the optical fiber cannot be detected accurately enough because the detected backscatter signal falls off very quickly when the focus is moved away from the optical fiber perpendicular to the direction of the optical fiber. Furthermore, inaccuracies in the detection result if only one segment of the glass fiber surface is scanned and the radius of the object is determined by means of a fit. Furthermore, in the case of cylindrical objects made of transparent material, the axis of rotation cannot be detected with high accuracy.If an optical component, for example a glass fiber, is embedded in a medium which exhibits two-photon fluorescence upon irradiation with light, the position and orientation of the glass fiber could be detected by scanning a (partial) volume around the glass fiber with a laser, in particular with the exposure laser of a lithography system, at low powers. A transition between the presence and absence of fluorescence defines an interface of the glass fiber over which the extent of the glass fiber can be determined. Knowing these data, the radius and position of the fiber can be determined. However, this method is inherently slow because a large volume must be scanned. Furthermore, inaccuracies in the detection result if only one segment of the glass fiber is scanned and the radius is determined by means of a fit. For this purpose, the radius of the glass fiber must be as uniform as possible, since otherwise further inaccuracies occur. Furthermore, the presence of a fluorescent material outside the glass fiber is required.WEI, Wieland [et al.]: Imaging of spheres with the confocal scanning optical microscope. In: Optics Letters (OL), Vol. 21, 1996, No. 22, pp 1800-1802-issn 0146-9592 (p); 1539-4794 (e). DOI: 10.1364 / OL.21.001800 describes a theoretical, three-dimensional distribution of a backscatter signal which results from the recording of a reflecting sphere with a confocal microscope and compares this with corresponding measurements. However, this publication does not describe a method for determining the spatial position of an object, in particular of the sphere. Furthermore, here, no consideration is given to the back reflection of non-spherical objects which is required for detecting a cylindrical glass fiber.XIAO, Yang; QIU, Lirong; ZHAO, Weiqian: Laser confocal cylindrical radius measurement method and its system. In: Applied Optics, Vol. 56, 2017, No. 23, pp. 6596-6602-issn 1559-128x(p); 2155-3165(e). DOI: 10.1364 / AO.56.006596 describes a confocal characterization of hollow cylinders. For this purpose, a cylindrical phase front is radiated onto a cylindrical test object, wherein the property is used that a section of a cylinder surface functions as a retroreflector when the illumination light field is focused on the center point of the cylinder. In this constellation, however, the position is known exactly a priori and the measurement is used exclusively to determine the radius of the cylinder. Furthermore, exclusively hollow cylinders are used as test objects.CHIARIOTTI, P. [et al.]: High-accuracy dimensional measurement of cylindrical components by an automated test station based on confocal chromatographic sensor. In: 2018 Workshop on Metrology for Industry 4.0 and IoT, 16-18 April 2018, Brescia, Italy, pp. 58-62. - ISBN 978-1-5386-2497-5. DOI: 10.1109 / METROI4.2018,8428340 describes using chromatic confocal detectors to characterize radii of hollow cylinders. In the described method, the orientation of the axis of the hollow cylinder relative to the measurement system is determined in order to automatically place the detector centrally in the hollow cylinder. For this purpose, a chromatic confocal sensor is placed inside a hollow cylinder and rotated. The chromatic confocal sensor determines the distance to the cylinder in a direction by which the rotation of the sensor within the cylinder and the spatial position of the axis of the hollow cylinder are determined. However, the method requires a light source to rotate within the object and is thus suitable only for hollow cylinders. In addition, a light source for determining the spatial position of glass fibers within an optical arrangement rotating about the glass fiber axis can only be implemented with considerable difficulties.BURGE, J.H.: Fizeau interferometric for large convex surfaces. In: Optical manufacturing and testing: 9-11 July 1995, San Diego, California. Bellingham, Wash.: SPIE, 1995 (Proceedings of SPIE; 2536). S.127-138. - ISBN 0-8194-1895-1. DOI: 10.1117 / 12.218415 describes the construction of a special Fizeau interferometer. In this case, a spherical reference surface is used to determine a surface quality of a test object by means of an interferometric structure. A determination of a spatial position of an object is not described here and is also not readily possible with this construction.DE 10 2006 017 401 A1 discloses a method for optically determining the center point of a transparent sphere, in which an approximately punctiform light source is imaged in a focus via an optical imaging system. The transparent sphere is placed in the beam path from the light source behind the imaging system and the intensity of the light reflected back from the transparent sphere is measured at a location which is optically equivalent to the position of the light source. By a relative movement between focus and center point of the sphere, the measured intensity of the light reflected at the sphere is minimized. In the corresponding relative position, the focus and the center point of the sphere coincide.DE 10 2015 009 471 A1 discloses an outer dimension measuring device which includes a light source; an optical system which focuses the light emitted by the light source onto an optical axis; a reflector which reflects the focused light; a detector which detects an intensity of the reflected light; A computing device that computes an outer dimension of a measured object using a first focus position, a second focus position, and a position of the reflector on the optical axis, wherein the first focus position is on the optical axis where a peak in a reflected light intensity is detected by the detector for light reflected by a first surface, and wherein the second focus position is on the optical axis where a peak in a reflected light intensity is detected by the detector for light reflected by the reflector and emitted on a second surface.JP 2002 195 814 A discloses a method and an apparatus in which attention is paid to the occurrence of the phenomenon that when light converged by an objective lens as a condensing optical system to the center of curvature of a spherical surface is reflected from the surface of the spherical surface, the reflected light thereof propagates in the reverse direction to the incident light, and the occurrence of the phenomenon that an incident light converged by the objective lens having an optical axis passing the center of the spherical surface is also reflected from the point to form a light traveling in the reverse direction in the same path as that, the position information for the condensation points of the two is obtained by observing both phenomena to determine the distance of both positions, and the distance is determined as a radius of curvature of the spherical surface.JP 2004 37 191 A discloses a measurement method and a measurement device for spherical parts for determining a radius of curvature of the spherical parts. To this end, the radius of curvature of a spherical inspection object is determined on the basis of the distance between two focal points when focusing light emitted from a light source on the upper side of the inspection object and when focusing toward the center of the inspection object.GU, K. [et al.]: Location tracking scanning method based on multi-focus in confocal coordination measurement system. In: Precision Engineering, Vol. 71, pages 170-177, ISSN 0141-6359, https: / / doi.org / 10.1016 / j.precisionng.2021.03.012 proposes a novel scanning method for detecting positions which is based on a multifocus application. In this method, the relative horizontal scan trajectory includes continuous linear motion during the process of axial tomography, and the horizontal motion surface is localized by a series of foci to generate the axial response signal.KLEIN, pp. [et al.]: Soliton guide and multiphoton absorption processes in photopolymerizable materials for optical integrated circuits, Organic Optoelectronics and Photonics, Proc. SPIE 5464, Organic Optoelectronics and Photonics, 08.09.2004, https: / / doi.org / 10.1117 / 12.547950 describes a method for producing three-dimensional optically integrated circuits.Object of the InventionProceeding from this, the object of the present invention is to provide a method and a device for determining a spatial position of a non-spherical object and an associated computer program, which at least partially overcome the disadvantages and limitations of the prior art mentioned.In particular, the present invention is intended to enable the most accurate possible determination of the spatial position of an object, in particular of a glass fiber, especially when the object, in particular the glass fiber, is located on a substrate in a poorly accessible manner and / or within a system for two-photon lithography in a poorly accessible manner. In this case, the determination of the spatial position of the object should also be possible if the object is at least partially surrounded by a photoresist. Furthermore, the determination of the spatial position of the object should also be possible if the accessible detection volume is very small. Furthermore, the optics for detecting the position of the object should largely coincide with the optics for exposing the object, in particular in order to reduce potential errors and offsets between the manufacture of the object and the detection of the object.Disclosure of the InventionThis object is achieved by a method and a device for determining a spatial position of a non-spherical object and by an associated computer program having the features of the independent patent claims. Advantageous refinements which can be implemented individually or in any desired combination are presented in the following description and the dependent claims.In a first aspect, the present invention relates to a method for determining a spatial position of a non-spherical object, which has at least one surface section of known shape. The term "object" as used herein refers to an extended article, animate or animate in nature, having a surface accessible by the present method. The term "non-spherical object" refers to an object whose surface deviates from a spherical shape. The non-spherical object can preferably be a cylindrical object, in particular a glass fiber. The term "glass fiber" here denotes a cylindrical object comprising a glass fiber core and a glass fiber cladding that is configured as an optical fiber to efficiently guide light by utilizing an optical refractive index difference between the glass fiber core and the glass fiber cladding.The term "spatial position" denotes an indication with respect to a localization of an extended object in a space, in particular in the form of values with reference to a coordinate system. The coordinate system can preferably be selected from a Cartesian coordinate system, a cylindrical coordinate system or a polar coordinate system; however, the use of another coordinate system is conceivable. In general, the spatial position of the object can be composed of a position of the object and an orientation of the object. In this case, the term "position" denotes a location in space at which a point, in particular a center point or a center of gravity, of the object is located, while the term "orientation" specifies a direction in which an axis of the object, in particular a longitudinal axis of a cylindrical object, preferably a glass fiber, is aligned.The present method for determining a spatial position of a non-spherical object having at least one surface section of known shape comprises the following steps: a) irradiating at least two light fields through an objective onto the object, wherein each light field has known phase fronts, wherein the phase fronts of the at least two light fields differ from one another at least after the objective, wherein a curvature of the phase fronts at an exit window of the objective in at least one spatial direction is less than a smallest curvature of the surface section of the object, wherein for at least one of the light fields there is at least one line lying in the surface section, along which at least two local surface normals of the surface section are orthogonal to the phase front of the at least one of the light fields; b) detecting a reflected portion of the at least two light fields emanating from the object by means of a detector; and c) determining the spatial position of the non-spherical object from the detected reflected portion of the at least two light fields taking into account an expected backscatter signal which results from the known shape of the surface section.The steps of the present method can preferably be carried out in the stated order, starting with step a), following with step b) and ending with step c), wherein one or more, in particular successive steps, can also be carried out at least partially simultaneously. In a preferred embodiment, steps a) and b) of the present method can be repeated with a multiplicity of different light fields generated successively in time, each of which has phase fronts that differ from one another. The term "successively in time" here denotes a chronological sequence according to which the respective light fields are generated successively in time and are radiated onto the object. A time interval between two light fields following one another in time is preferably 0.1 μs to 100 ms, particularly preferably 1 μs to 100 μs; however, the use of a different time interval is possible. In an alternative configuration, the at least two light fields can be irradiated simultaneously in step a) if the detector used according to step b) is configured to detect the reflected portion of the at least two light fields respectively emanating from the object in a spatially resolved manner. Independently of the choice of the configuration, the determination of the spatial position of the object can preferably take place within 30 seconds, particularly preferably within 10 seconds.According to the invention, the determination of the spatial position of a non-spherical object is carried out by scanning a surface section of the object with at least two light fields which have phase fronts different from one another at least after the objective according to step a). In front of the objective, the at least two light fields can still be identical, while according to the invention they differ from one another after the objective. The specification "after the objective" here denotes a direction in the propagation direction of the at least two light fields. As described in more detail below, in a particular configuration, by moving the objective in the z direction, a difference can be produced between the phase fronts downstream of the objective, wherein the position of the at least one galvanometric scanner in the xy plane remains the same. However, other embodiments for generating the required difference between the phase fronts downstream of the objective are conceivable.The term "light field" here denotes a spatially extended light beam, which is preferably present as a collimated light beam, wherein the term "spatially extended" indicates that the light beam has a diameter, preferably from 0.1 mm to 100 mm, preferably from 1 mm to 20 mm. "Scanning" of the surface section of the object is effected in that the at least two light fields are in each case focused one by means of an objective and therefore the phase fronts which are different from one another and are preferably substantially spherical in design strike the surface section of the object. The scanning of the surface section of the object can preferably be effected by means of 2 to 2,000,000, preferably 50,000 to 750,000, light fields with phase fronts different from one another; however, the use of a different number of light fields is possible.The term "surface portion" refers to a portion of the surface of the extended article, the geometric shape of which is known as the "shape". In this case, the shape of the surface section can be characterized by means of local surface normals, wherein the term "surface normal" denotes an imaginary vector which is orthogonal to the outer surface of the surface section. The term "orthogonal" here denotes an angle of 90°±1°, preferably 90°±0.1°. In a particular configuration, the surface portion of known shape may comprise an entire surface of the object. Alternatively or additionally, a distribution of a reflected portion of the at least two light fields over the entire surface of the object may be known, modeled or estimated. The term "spherical" refers here to phase fronts which represent a section of a spherical surface. The term "substantially" here comprises a deviation of the total area of the phase front of at most 10%, preferably of at most 1%, from a section of a spherical surface.The term "surface portion of known shape" here denotes the presence of basic information about the spatial shape of the surface portion. For this purpose, it is not necessary for the shape to be known in detail or with all parameters. In an embodiment in which the surface section has a cylindrical shape, it is not necessary for the method according to the invention for determining the spatial position of the non-spherical object to know the diameter of the object, information that a cylindrical shape is present is sufficient. Alternatively or additionally, the basic information about the spatial shape of the surface section can also be determined indirectly, preferably by means of a detection according to the invention and an additional ex situ measurement using a further method, preferably in order in this way to establish a relative position between a detected maximum in the light field and the surface section.The term "phase front" denotes an imaginary surface on which all points have the same phase, wherein the phase front moves at the speed of light in the direction of the surface normal of the phase front. The phase fronts which differ from one another at least after the objective and which simultaneously or preferably consecutively impinge on the surface section of the object can preferably be generated by moving a focal point of the light field as far as possible in all three spatial directions by means of a device configured for this purpose. Here, at least one of the light fields can be changed accordingly, preferably in a beam path in front of an objective. For this purpose, preferably at least one galvanometric scanner can be used. Alternatively or additionally, a relative displacement between the objective and the object can take place between the irradiation of the at least two light fields. For this purpose, at least one element can be used which is configured for displacing the object and / or the objective, preferably selected from a positioning table which can preferably be operated piezoelectrically, or on by means of an inductive element, in particular a voice coil (voice coil). The term "phase fronts different from one another" denotes a difference of the phase fronts relative to the object, in particular to a surface section of the object.Further alternatively or additionally, the change of at least one of the light fields can be carried out by means of a diffractive element. The diffractive element can in particular comprise a digital light modulation element which has a multiplicity of individually controllable optical elements which are configured for modulating an incoming light beam. The digital light modulation element can preferably have a spatial light modulator or a digital micromirror unit. The term "spatial light modulator" (SLM) denotes an optical device which is configured to apply an intensity pattern, in particular in the form of a spatial modulation of an amplitude and / or a phase, to an incident light beam, wherein the application of the intensity pattern can be effected electronically and / or optically. A digital micromirror device (DMD) is an arrangement which has a multiplicity of tiltable micromirrors arranged in the form of a matrix, which have an edge length in the micrometer range, each micromirror being individually adjustable by means of electrostatic fields.By a relative change of the position of the focal point with respect to the object, the preferably substantially spherical phase fronts can strike the surface section of the object from different directions and with different curvatures. If, furthermore, according to step a), the curvature of the phase front in at least one spatial direction corresponds to the curvature of the surface section in the same spatial direction or at least one line exists in the surface section, along which line at least two local surface normals of the surface section are orthogonal to the phase front of the light field just impinging on the surface section, a significant proportion of the light field incident on the object is reflected back onto itself as a reflected proportion of the at least two light fields. The term "reflected" here denotes a process in which a portion of the light field impinges on a surface, wherein the phase fronts of the light field change in such a way that the light field impinging on the surface is superimposed. The term "curvature" refers to a local deviation of a course of a surface from a plane in at least one dimension. Furthermore, the term "line" denotes an imaginary course of a spatial arrangement; in the present case, the imaginary course of the spatial arrangement of the at least two local surface normals, which are orthogonal to the phase front of the light field just impinging on the surface section, on the surface section under consideration.In order for the respective light field to be reflected at the object, a refractive index difference can exist between the object and the medium surrounding the object. Here, a refractive index difference of already ≤0.2, preferably ≤0.1, can be sufficient for a detectable backscatter signal. In particular, if it is a transparent or partially transparent object, the reflected portion of the at least two light fields emanating from the object can be generated at the surface section of known shape and at an inner boundary surface in an interior space of the object. In this case, at an inner boundary surface in the interior there are two local surface normals of the surface section which are orthogonal to the phase front of the light field just impinging on the surface section. In a particular configuration, a combination of both the reflection of the at least two light fields at the surface and at the inner interface can be used for detection.Alternatively, the object can be non-transparent, preferably in that it can be coated at least in the region of the surface section. In this embodiment, the reflected portion of the at least two light fields emanating from the object can be generated exclusively at the surface section of known shape. If the illumination field is fully reflected before it propagates through the focus region, no real focus region exists. In this case, a virtual focus area can be considered as the focus area of the imaginary non-reflected beam. However, the determination of the spatial position of the object, in particular of an axis of symmetry of a cylindrical object, is also possible if only one virtual focus region exists. A coating of at least the surface section of the object can preferably be effected by means of metallization or by means of deposition of a dielectric layer stack (Bragg mirror); however, an alternative or additional use of another process is possible. This embodiment can be advantageous in particular in that a higher signal contrast can be obtained by the non-transparent coating of at least the surface section of the object.In a particularly preferred embodiment, according to which the spatial position of a cylindrical object, in particular a glass fiber, is determined, the curvature of the substantially spherical phase fronts only corresponds in one spatial direction to the curvature of the object if the focus region lies in the center of the cylinder. The term "focus range" here denotes a volume around the focal point, within which the radiated intensity exceeds a predefined intensity threshold. The intensity threshold may be a value of at least 36.8% (i.e., ≈1 / e) or at least 50% of the maximum intensity occurring at the focal point; however, the use of a different value is possible.In a particularly preferred embodiment, the at least two local surface normals of the surface section can be orthogonal to the phase front of the light field currently impinging on the surface section, wherein the distance between the focal point and the surface section preferably corresponds to at least twice the diameter of the focal region, particularly preferably at least five times the diameter of the focal region.According to step b), the reflected portion of the at least two light fields emanating from the object is detected by means of a detector, preferably a confocal detector. The reflected portion of the at least two light fields is detected for this purpose for at least two light fields having phase fronts that are different from one another. For this purpose, the reflected portion of the at least two light fields can be coupled out from a common beam path with the portion of the light field incident on the object by means of a beam splitter in order to generate the light field incident on the detector; however, it is possible to use at least one other optical element or another type of beam path suitable for this purpose.In a particularly preferred embodiment, the detector can comprise a focusing optical unit which is configured to focus the light field impinging on the detector onto an aperture before it impinges on a photodetector. In an alternative embodiment, the confocal detector can have a glass fiber instead of the aperture, which is configured to guide the light field impinging on the glass fiber onto the photodetector.In a further embodiment, the detector can detect the backscatter signal from a plurality of positions in a spatially resolved manner. This configuration is advantageous in particular when the at least two light fields are irradiated simultaneously in step a).However, further configurations of the detector are conceivable.In a particular configuration, the detection of the reflected portion of the at least two light fields emanating from the object can be carried out by means of the detector synchronously with the generation of the light fields following one another in time. As soon as a newly configured light field having a phase front different from the preceding light field is irradiated onto the object, the detection of the reflected portion of the at least two light fields emanating from the object can be carried out again. The term "synchronous" thus denotes a temporal coordination between steps a) and b), and preferably additionally step c), i.e. between the generation and irradiation of a selected light field onto the object according to step a) and the detection of a reflected portion of the selected light field emanating from the object by means of the detector according to step b) and, preferably, the determination of the spatial position of the object from the detected reflected portion of the selected light field according to step c). Other configurations are possible, however.If the shape of the surface section and the irradiated phase fronts are known, the spatial position, i.e. the position and the orientation, of the object is thus determined according to step c). By repeatedly executing steps a) and b), information on an intensity of the component reflected by the object can be obtained for each of the irradiated light fields having different phase fronts. The intensity of the light field detected in the detector is highest when at least one line lying in the surface section exists, along which at least two local surface normals of the surface section are orthogonal to the phase front of at least one of the light fields. From detected signals of the detector, together with the associated radiated light fields and phase fronts, those signals can be determined which have the highest intensity. The respectively associated phase fronts then represent individual surface sections which, in summary, enable the detection of the position and orientation of the object.In a preferred embodiment, the focused portion of the light field can first be deflected laterally, i.e. perpendicularly to the propagation direction of the light field, in two dimensions and the reflected signal can be recorded for each point on this surface spanned by the two dimensions. The focal point is preferably located within a cylindrical object, particularly preferably in the vicinity of the axis of rotation of the cylindrical object. The spatial sampling rate can preferably be 10 nm to 10 μm, particularly preferably 50 nm to 500 nm. The intensity of the reflected signal detected in the detector can preferably be stored together with the associated position of the focal point. The focal point can then be shifted in the propagation direction of the light field, preferably by 10 nm to 10 μm, particularly preferably by 50 nm to 500 nm, so that a further surface can be scanned perpendicularly to the propagation direction and the intensity values can be stored together with the associated positions of the focal point. By further repetitions of this procedure, a volume can be scanned layer by layer by the focal point. From the stored data of the scanned volume, those focal points or groups of focal points can now be determined for which the intensity is the highest. The expression that "the intensity is the highest" here denotes an intensity above a defined intensity threshold. The position of these focal points substantially corresponds to the sought spatial position of the central axis of the cylindrical object. The term "substantially" here comprises a deviation of the position of the central axis of the cylindrical object of better than 1 μm, particularly preferably of better than 500 nm, and a deviation of the orientation of preferably better than 1°, particularly preferably better than 0.5°, with respect to the actual spatial position of the central axis of the cylindrical object, which can be determined in particular in tests for calibrating the present method by means of other methods and apparatuses.To determine the highest intensity, methods from industrial image processing can preferably be used. In this case, edge recognition can be carried out for each scanned surface in order to determine a light-dark contrast between the focal points or the groups of focal points and their surroundings on the respective surface. Preferably, an axis of symmetry of the cylindrical object can be determined in the surface or in a partial region of the surface which has the highest light-dark contrast.In a particularly preferred embodiment, the present invention enables the position and the orientation of a glass fiber to be determined by scanning a volume in the glass fiber body perpendicular to the axis of rotation by means of a focused light field, wherein a confocal detector is preferably used for the detection. The glass fiber can be part of a structure which comprises other optical components in addition to the glass fiber. The structure can be configured such that a photonic wire bond or a microlens can be introduced as an optical connection between the glass fiber and a further optical component by means of a direct writing lithography method. A part of the glass fiber and / or a part of the structure can be embedded in a photoresist for this purpose. By appropriate arrangement of the light source, the objective, the object and the detector, only those beams which intersect the center of the glass fiber can be detected with the detector and are thus guided through the glass fiber core. In other words: When scanning a subvolume, the backscatter signal detected with the detector can then achieve a maximum of an amplitude if the focus region is located in the center of the optical fiber, i.e. in the optical fiber core. In this embodiment, not the surface of the glass fiber but the interior of the glass fiber is scanned, resulting in a higher accuracy of the detection. After detection, the photonic wire bond or microoptical can be produced in situ using the same light source and the same objective.In a further aspect, the present invention relates to a computer program for determining a spatial position of a non-spherical object. In a preferred embodiment, the computer program is stored on a non-transient computer-readable medium. The terms "non-transient computer-readable medium" or "computer-readable medium" refer here to a non-volatile data storage medium, for example a hardware storage medium, on which computer-executable instructions are stored, in particular a random access memory (RAM) or a read-only memory (ROM). The non-transitory computer readable medium may preferably include instructions which, when executed by the computer or a computer network, cause the computer or the computer network to control and / or execute at least step c), preferably all steps, of determining the spatial location of the non-spherical object according to the method described herein for determining a spatial location of a non-spherical object.In a further aspect, the present invention relates to a device for determining a spatial position of a non-spherical object, which has at least one surface section of known shape. The device comprises:at least one light source which is configured to generate at least two light fields, each light field having known phase fronts, the phase fronts of the at least two light fields differing from one another at least after the objective, a curvature of the phase fronts at an exit window of the objective in at least one spatial direction being less than a smallest curvature of the surface section of the object, at least one of the light fields having at least one line lying in the surface section, along which at least two local surface normals of the surface section are orthogonal to the phase front of the at least one of the light fields, existing for at least one of the light fields;at least one objective which is configured to irradiate the at least two light fields onto the object;at least one detector which is configured to detect a reflected portion of the at least two light fields emanating from the object; andat least one evaluation and control device which is configured to determine the spatial position of the non-spherical object from the detected reflected portion of the at least two light fields taking into account an expected backscatter signal which results from the known shape of the surface section.The term "evaluation and control device" denotes a device which is set up for receiving, processing and outputting data. This can preferably be an electronically or optoelectronically controllable device which can in particular have a computer, microcomputer or programmable chip, e.g. an application-specific integrated circuit (ASIC) or an FPGA (field-programmable gate array), wherein the evaluation and control device can access one or more computer programs which can be configured to carry out the method described herein. Alternatively or additionally, the evaluation and control device can be comprised by a mobile communication device, in particular a smartphone, tablet or laptop. Other embodiments of the evaluation and control device are possible, however, for example, an integration of the evaluation and control device into a server. However, it is not necessary here for the evaluation and control device to be located in the same room or in the same environment as the remaining components of the apparatus; using a computer network, the evaluation and control device can also be arranged in another room, another building, another city, another state or another continent.For further details with respect to the present apparatus and the computer program, reference is made to the description of the method according to the invention.Advantages of the InventionThe present invention solves the problem of determining the most accurate possible value for the position and orientation of an object in space, in particular a glass fiber, which is preferably introduced into a lithography system. In this case, the position and orientation of the object in space can be determined by means of an optical method, wherein the shape of at least one surface section of the object is known. In particular, the present invention can reliably detect axes of rotation of cylindrical, transparent or non-transparent objects. In this case, the object to be detected can be fixed on a carrier which is not transparent and / or the accessibility of which from different spatial directions is restricted. Thus, the object may generally not be accessible from all sides, but may be irradiated with a light field essentially only from one spatial direction and its back reflection may be observed. The position and orientation of the object in space can advantageously be determined independently of any background illumination or scattered light of the environment.In the present invention, detection of an object surrounded at least partially by a photoresist is also possible. Furthermore, the object can also be detected with a very small accessible detection volume, preferably of 300 μm×300 μm×300 μm or less, in particular of 80 μm×80 μm×80 μm or less; for glass fibers, a detection volume of 200 μm×200 μm×200 μm or less, in particular of 40 μm×40 μm×40 μm or less, can be sufficient for reliable detection. The present invention further enables a construction and use of a two-photon lithography system, so that the optics for detecting the position of the object correspond in wide parts to the optics for exposure for producing an object. In particular, a laser, which is often pulsed in the fs range, the galvanometric scanner and the objective of a lithography system can be used to generate the at least two light fields. This type of construction minimizes, in particular, potential errors and offsets between the production of the object and the detection of the object.The detection of the position of the object in space with the present invention can be performed robust regardless of the type of optical structure and the environment of the object. In particular, the position of the object can thus be detected with an accuracy of preferably better than 1 μm, particularly preferably better than 500 nm, and the orientation can be detected with a deviation of preferably better than 1°, particularly preferably better than 0.5°. In this way, a particularly low-loss coupling to a glass fiber, the position of which in space was determined with the present invention, can take place. Although, when using the glass fiber in a high-resolution lithography system, the image field for detecting the glass fiber is limited by the optics of the lithography system, the present invention makes it possible to detect the glass fiber with the same optical system as is also used for lithography.In particular in the case of optical assemblies in which an object is mounted on an assembly carrier, with the present invention, despite inadequate illumination, optical detection can take place although the object is poorly accessible because it is either installed on a sample or because access cannot be ensured due to a process machine. The present invention is particularly suitable for industrial use, since it enables a rapid measurement, achieves low cycle times and is thus able to save outlay and costs without the accuracy of the measurement being restricted as a result. The method is also suitable for detecting general objects and is therefore also not dependent on the presence of fluorescence in the object or the environment of the object for detection.Furthermore, it is not necessary to measure the surface of the object separately for detecting an object or to determine it by an approach method, in particular a fit. In particular, in the case of a cylindrical object, the backscatter signal becomes maximum in the method according to the invention when the focal point lies on the axis of the object to be detected. In this way, a high precision of detection can be achieved.Herein, the terms "have," "have," "comprise," or "include," or any grammatical variations thereof, are used in a non-exclusive manner. Accordingly, these terms may refer to situations in which, in addition to the features introduced by these terms, no further features are present, or to situations in which one or more further features are present. For example, the term "A has B", "A has B", "A comprises B" or "A includes B" can refer both to the situation in which, apart from B, no further element is present in A (i.e. to a situation in which A consists exclusively of B) and to the situation in which, in addition to B, one or more further elements are present in A, for example element C, elements C and D or even further elements.It is also pointed out that the terms "at least one" and "one or more" and grammatical modifications of these terms, when used in conjunction with one or more elements or features and are intended to express that the element or feature can be provided once or multiple times, are generally used only once, for example when the feature or element is introduced for the first time. In the case of a subsequent renewed mention of the feature or element, the corresponding term "at least one" or "one or more" is generally no longer used, without limiting the possibility that the feature or element can be provided once or more than once.Furthermore, the terms "preferred", "preferably", "in particular", "for example" or similar terms are used herein in conjunction with optional features, without alternative embodiments being restricted thereby. Thus, features introduced by these terms are optional features and are not intended to limit the scope of the claims and in particular the independent claims by these features. Thus, as will be appreciated by those skilled in the art, the invention may also be practiced using other configurations. Similarly, features initiated by "in one embodiment of the invention" or by "in one embodiment of the invention" are understood as optional features, without the intention of restricting alternative configurations or the scope of protection of the independent claims. Furthermore, these introductory expressions are intended to leave all possibilities for combining the features initiated thereby with other features, whether they be optional or non-optional features, uncontacted.Brief Description of the FiguresFurther details and features of the present invention will become apparent from the following description of a preferred embodiment, in particular in conjunction with the dependent claims. In this case, the respective features can be realized on their own or in combination with one another to a plurality thereof. The invention is not limited to the exemplary embodiments. The exemplary embodiments are illustrated schematically in the following figures. In this case, identical reference numerals in the figures denote identical or functionally identical elements or elements corresponding to one another with regard to their functions. In detail, the following show: FIG. 1 shows a schematic representation of an embodiment of a device for determining a spatial position of a non-spherical object; and FIG. 2 shows a schematic representation of an exemplary embodiment of a method for determining a spatial position of a non-spherical object.DESCRIPTION OF THE EMBODIMENTSFIG. 1 shows a schematic representation of an embodiment of a device 10 for determining a spatial position of a non-spherical object 110 comprising at least one surface section 111 of known shape, wherein the shape of the surface section 111 can be characterized by means of local surface normal 112. The non-spherical object 110 illustrated here by way of example is a cylindrical object which can be embodied in particular as a glass fiber, wherein any part of the cladding of the cylindrical object, in particular of the glass fiber, can be used as the surface section 111 of known shape. In a particularly preferred embodiment, the position of a glass fiber can be detected within a lithography system. In this case, the position and orientation of the glass fiber core of the glass fiber are to be detected in three dimensions. The glass fiber can preferably be a component of an optical structure, whereby accessibility from all spatial directions can be restricted. In particular, a front facet of the glass fiber may be inaccessible to imaging optical systems. Examination of an object 110 of different shape is possible, however, as long as its shape is known in at least one surface section 111.The exemplary device 10 schematically illustrated in FIG. 1 comprises a light source 50, a beam splitter 60, an optional galvanometric scanner 75, an objective 70, and a detector 80. The light source 50 is configured to generate a light field 100 which is guided onto the objective 70 in a beam path illustrated in FIG. 1A. According to the coordinate system 120 likewise illustrated in FIG. 1A, the light field 100 is guided in the z direction for this purpose. The light source 50 can preferably be embodied as a laser or comprise a laser, in particular a femtosecond laser (fs laser). In a particularly preferred embodiment, the light source 50 can be configured simultaneously as an exposure laser of a lithography system. This allows detection and writing at exactly the same position; calibration errors or imaging errors can be compensated automatically. The wavelength of the light source is preferably 300 nm to 3000 nm, particularly preferably 500 nm to 1500 nm. However, the use of another type of light source 50 is possible.The objective lens 70 is configured to generate a focused portion 101 from the light field 100 generated by the light source 50, which is focused on a focal point 103 surrounded by a focal region. In the illustration of FIG. 1A, the focal point 103 is a real focal point that lies within the object 110. Furthermore, the galvanometric scanner 75 is configured to influence the light field 100 generated by the light source 50 in the beam path in front of the objective 70 in such a way that the focus range around the focus point 103 generated by the objective 70 is adjusted in the lateral direction. According to the schematically illustrated coordinate system 120, this is the x-direction and / or the y-direction. The galvanometric scanner 75 can be configured in particular to deflect the light field 110 at a variable angle, wherein the angle can be predetermined by an evaluation and control device 150.Alternatively or additionally to the galvanometric scanner 75, the light field 100 generated by the light source 50 can be influenced by displacing the objective 70, in particular by means of a positioning table, which is preferably operated piezoelectrically, or on by means of an inductive element, in particular a voice coil (voice coil). This alternative is illustrated schematically in particular in FIGS. 1B and 1C. Other possibilities for influencing the light field 100 generated by the light source 50 are conceivable, preferably by means of a diffractive element (not shown). The diffractive element can comprise, in particular, a digital light modulation element explained in more detail above, in particular a spatial light modulator or a digital micromirror unit.In a preferred embodiment, the object 110 is transparent or at least partially transparent with respect to the incident light field 110, such that the focused portion 101 of the light field 100 generated by the objective 70 can enter an interior 113 of the object 110 in a region of the surface section 111 of known shape. In particular, due to a difference in refractive index between a substance located in the interior 113 of the object 110 and a material bypassing the object 110, a part of the focused portion 101 of the light field 100 generated by the objective 70 is reflected at an inner boundary surface 114 of the object 110 and thus a reflected portion 102 of the light field 100 is generated. The material which at least partially surrounds the object 110 can be selected in particular from air, an adhesive which can also be configured for fastening the object, an immersion medium for an objective having a high numerical aperture NA, in particular a numerical aperture NA >1, or a photoresist which can likewise be configured as an immersion medium.In an alternative embodiment (not shown), the object 110 can have a substance that is non-transparent with respect to the incident light field 100, or at least one of the surface sections 111 of the object 110 can be provided with a coating that is non-transparent with respect to the incident light field 100, such that the reflected portion 102 of the light field 100 is generated by reflection of the focused portion 101 of the light field 100 generated by the objective 70 on the relevant surface section 111 of the object 110. In this embodiment, the optical paths illustrated in FIG. 1 within the object 110, including the focal point 103, are to be considered virtual. If the light field 100 is fully reflected before propagating through the focus area, there is no real focus area; in this embodiment, a virtual focus area can be considered as the focus area of the imaginary non-reflected light field. This embodiment can be advantageous in particular in that an increase in signal contrast can be made possible by the non-transparent coating of at least the surface section 111 of the object 110. The coating of at least the surface section 111 of the object 110 can preferably be effected by means of metallization; however, an alternative or additional use of another process is possible.As FIG. 1 further shows, the portion 101 of the light field 100 generated by the light source 50 and focused by the objective 70 has known phase fronts 104, which are schematically illustrated as dashed lines. In the embodiment shown, the phase fronts 104 are substantially spherical, wherein a curvature of the substantially spherical phase fronts 104 at an exit window of the objective 70 in at least one spatial direction, in FIG. 1, in particular in the direction along the z-axis, is less than a smallest curvature of the surface section 111 of the object 110. As a result, in particular for the substantially spherical phase fronts 104, a working distance suitable for carrying out the present method can be set between the objective 70 and the surface section 111 of the object 110.As is also shown in FIG. 1, the beam splitter 60 is configured to guide the reflected portion 102 of the light field 100 in the direction of the detector 80, which thereby forms a light field 105 impinging on the detector 80. In particular, in order to achieve the highest possible spatial resolution, the detector 80 can be designed as a confocal detector. For this purpose, the detector 80 can have a focusing optical unit (not shown), which focuses the light field 105 impinging on the detector 80 onto an aperture before it impinges on a photodetector. In an alternative embodiment, the confocal detector can have, instead of the aperture, a glass fiber (not shown), which is configured to guide the light field 105 impinging on the glass fiber to the photodetector.The use of the objective 70 as a common optical element, which is illustrated by way of example in FIG. 1 and is configured both for illuminating the object 110 and for detecting the reflected portion 102 of the light field 100, is advantageous, in particular since in this way any aberrations in the objective 70 are automatically corrected and therefore an additional calibration of a second objective can be dispensed with.According to the invention, the surface section 111 of the object 110 is illuminated successively in time with at least two, preferably a plurality, of different light fields 100, which each have a known phase front 104, wherein the phase fronts 104 of the at least two, preferably of the plurality, of the light fields 100 differ from one another at least after the objective 70. In this way, in particular, a "scanning" of the surface section 111 of the object 110 can take place. According to the invention, the scanning of the surface section 111 of the object 110 is carried out until, for at least one of the light fields 100, at least one line (not shown) lying in the surface section 111 exists, along which the at least two local surface normals 112 of the surface section 111 are orthogonal to the phase front 104 of the at least one light field 110.Signals are generated in the detector 80 which are based on the light field 105 impinging on the detector 80 and which can be detected and recorded by means of an evaluation and control device 150. Here, the detection and recording of the signals of the detector 80 can preferably take place synchronously with the movement of the focal point 103. By means of an algorithm set up for this purpose, the sought position and orientation of the object 110 can be determined from the signals. As schematically shown in FIG. 1, the evaluation and control device 150 can be used as a computer (computer. The control unit may be a personal computer or PC) which can be controlled by means of a monitor 152 and / or a keyboard 154. Alternatively or additionally (not shown), the evaluation and control device 150 can be designed as an electronic communication device, preferably a smartphone, tablet or laptop, which comprises the monitor 152 and the keyboard 154. The monitor 152 can have a screen 153 on which the object 110 and / or its determined spatial position can be displayed. The evaluation and control device 150 can furthermore have connections 151, by means of which it can be connected in particular to the light source 50, the galvanometric scanner 75, the detector 80, the monitor 152 and / or the keyboard 154, wherein the connection 151 can be implemented in a wired or wireless manner. As mentioned above, however, it is not necessary here for the evaluation and control device 150 to be located in the same room or in the same environment as the remaining components of the apparatus 10; using a computer network, the evaluation and control device 150 can also be arranged in another room, another building, another city, another state or another continent. Other embodiments of the evaluation and control device 150 are possible.As illustrated in FIG. 1A, a portion 101 of the light field 102 focused on the real or virtual focal point 103 is imaged on itself when the focal region intersects an axis of symmetry of the object 110. If the focus region is located at the center 115 of the cylindrical object, in particular the glass fiber, the inner boundary surface 114 of the cylindrical object 110 functions as a retroreflector, which generates the reflected portion 102 of the light field 100, which-on account of the back reflection-spatially overlaps the portion 101 of the light field 100 focused on the focus point 103. By means of the beam splitter 60, the reflected portion 102 of the light field 100 can strike the detector 80 as the light field 105 and can be registered there with a signal intensity.However, if the focus region, as in the representations according to FIGS. 1B and 1C, is located real or virtually outside the center point 115 of the cylindrical object 110, the portion 102 of the light field 100 reflected at the inner boundary surface 114 of the cylindrical object 110 does not form on itself and is thereby defocusing when it strikes the detector 80, resulting in a low signal intensity-in comparison to the situation shown in FIG. 1A.In order to determine the position and the orientation of the object 110 in space, at least two, preferably a plurality of points are identified in a region of the surface section 111 at which the surface of the object 110 functions as a retroreflector which is as good as possible. In order to obtain the plurality of points in the surface portion 111, the position of the focal point 103 may be changed preferably relative to the center point 115 of the object 110. For this purpose, as described above, the movable objective 70 and / or the galvanometric scanner 75 can be used, wherein the galvanometric scanner 75 is configured to deflect the light field 110 at a variable angle, wherein the angle to be set in each case can be predefined by the evaluation and control device 150. By determining a plurality of maxima in the light field 105 which impinges on the detector 80, it is possible in particular to determine an axis of a cylindrical object 110; for this purpose, a further dimension, in particular a radius, of the cylindrical object 110 does not have to be known.FIG. 2 shows a schematic representation of an exemplary embodiment of a method for determining a spatial location of a non-spherical object 110 in space. The objective lens 70 generates the focused portion of the light field 101 from the light field 100. According to steps a) and b), the focal point 103 is first deflected laterally in a surface 201 of the xy plane in the coordinate system 120 by means of the galvanometric scanner 75, and the light field 105 impinging on the detector 80 is recorded for each point in this surface 201 by means of the detector 80. The focal point 103 is preferably located within the object 110, preferably the cylindrical object, in particular the glass fiber. Scanning of the surface with the focal point 103 is not necessary. The spatial sampling rate, i.e. a distance between the points 210 in the surface representing the respective focal point 103, is preferably 10 nm to 10 μm, particularly preferably 50 nm to 500 nm. The detected intensity of the reflected signal is stored together with the associated position of the focal point 103 in the monitoring and evaluation unit 150. Thereafter, the focal point 103 is shifted in the propagation direction of the light field 100, i.e. along in the z direction, preferably by 10 nm to 5 μm, particularly preferably by 50 nm to 500 nm. The displacement in the z direction can be effected by displacement of the objective 70. A further surface 202, 203, 204 is then scanned in the xy plane and the intensity values detected by the detector 80 are stored together with the associated positions of the points 210 representing the respective focal point 103. By further repetitions of this process, a volume is scanned layer by layer by the focal point 103. From the data of the scanned volume stored in the monitoring and evaluation unit 150, it is now possible to determine those focal points 103 or groups of focal points 103 for which the intensity is the highest. The position of these focal points 103 substantially coincides with the position of the central axis of the cylindrical object 110. In order to determine the maximum intensity, at least one intensity threshold can be defined here, wherein those intensities can be considered as highest intensities which exceed the intensity threshold which has the highest value.For determining the highest intensity, methods from industrial image processing can preferably be used. Edge recognition can thus be carried out for each scanned surface 201, 202, 203, 204, in particular in order to determine a light-dark contrast between the points 210 representing the respective focal points 103 and their surroundings on the associated surface 201, 202, 203, 204. From the surface 201, 202, 203, 204 which has the highest edge contrast, the position of an axis of symmetry of the cylindrical object 110 can thus be determined. For a more accurate determination of the position of the axis of symmetry, each detected surface 201, 202, 203, 204 can preferably be divided into partial regions perpendicular to the presumed axis of symmetry, and the light-dark contrast can be detected for each partial region. The position of the axis of symmetry can then be effected by evaluating the partial regions with the highest contrast over all surfaces 201, 202, 203, 204.For example, points 210 on a left-hand portion of the surface 203 may have the highest intensity. From this determination, it is then possible to infer the position and orientation of the position of the axis of symmetry in the object 110 and, given known symmetry, in particular given the existence of a cylindrical object, the position of the entire object 110. Many other examples are conceivable.The slice-by-slice scanning of the volume in the interior of the object 110 in lateral slices is only one possible exemplary embodiment. Other procedures such as scanning in vertical planes or also, for example, spirals, are likewise conceivable. Furthermore, it is also possible to configure the sampling in an adaptive manner, for example to adapt the sampling rate as a function of the signal on the detector 115.List of reference characters10 Device for determining a spatial position of a non-spherical object 50 light source 60 beam splitter 70 objective 75 galvanometric scanner 80 detector 100 light field 101 focused portion of the light field 102 reflected portion of the light field 103 focal point 104 phase front 105 light field 105 impinging on the detector 110 object 111 surface section 112 local surface normal 113 interior 114 inner boundary surface 115 center 120 coordinate system 150 evaluation and control device 151 connection 152 monitor 153 screen 154 keyboard 201, 202, 203, 204 surface 210 points in the surface representing the respective focal point

Claims

Method for determining a spatial position of a non-spherical object (110) having at least one surface section (111) of known shape, comprising the following steps: a) irradiating at least two light fields (100) through an objective (70) onto the object (110), wherein each light field (100) has known phase fronts (104), wherein the phase fronts (104) of the at least two light fields (100) differ from one another at least after the objective (70), wherein a curvature of the phase fronts (104) at an exit window of the objective (70) in at least one spatial direction is less than a smallest curvature of the surface section (111) of the object (110), wherein at least one line lying in the surface section (111) exists for at least one of the light fields (100), along which at least two local surface normals (112) of the surface section (111) are orthogonal to the phase front (104) of the at least one of the light fields (100); b) detecting a reflected portion (102) of the at least two light fields (100) originating from the object (110) by means of a detector (80); and c) determining the spatial position of the non-spherical object (110) from the detected reflected portion (102) of the at least two light fields (100) taking into account an expected backscatter signal which results from the known shape of the surface section (111).Method according to the preceding claim, wherein the irradiation of the at least two light fields (100) by the objective (70) onto the object (110) takes place in chronological succession.The method according to any of the preceding claims, wherein the at least two light fields (100) are or comprise focused beams, wherein the focused beams have substantially spherical phase fronts (104).Method according to one of the preceding claims, wherein the at least two local surface normals (112) of the surface section (111) are orthogonal to the phase front (104) of the light field (100) just impinging on the surface section (111), wherein a distance between the focal point (103) and the surface section (111) corresponds to at least twice the diameter of a focal region.Method according to one of the preceding claims, wherein the phase fronts (104) of the at least two light fields (100) differ from one another in that - at least one of the light fields (100) is changed in a beam path upstream of the objective (70) by means of a galvanometric scanner (75); or - at least one of the light fields (100) is changed by means of a diffractive element; or - a relative displacement between the objective (70) and the object (110) takes place between the irradiation of the at least two light fields (100).Method according to one of the preceding claims, wherein the reflected portion (102) of the at least two light fields (100) originating from the object (110) is generated at the surface section (111) of known shape and / or at an inner boundary surface (114) in an interior space (113) of the object (110).Method according to any one of the preceding claims, wherein the surface portion (111) of known shape comprises an entire surface of the object (110), or wherein a distribution of the reflected portion (102) of the at least two light fields (100) is known, modeled or estimated over the entire surface of the object (110).Method according to one of the preceding claims, wherein the detection of the reflected portion (102) of the at least two light fields (100) emanating from the object (110) takes place by means of a detector (80) synchronously with the generation of the time-sequential light fields (100).Method according to one of the preceding claims, wherein a focused portion (101) of the light field (100) is deflected in two dimensions perpendicularly to the propagation direction of the light field (100), and the reflected portion (102) of the light field (100) originating from the object (110) is detected on at least two surfaces (201, 202, 203, 204) spanned in the two dimensions, wherein between a detection of the reflected portion (102) of the light field (100) originating from the object (110) on two different surfaces (201, 202, 203, 204) a relative change of the position of a focal point (103) of the light field (100) with respect to the object (110) takes place, wherein the determination of the spatial position of the object (110) takes place from those focal points (103) or groups of focal points (103), which have an intensity of the reflected portion (102) of the light field (100) emanating from the object (110) above at least one intensity threshold and a distance from the surface of the object (110) which corresponds to at least twice the diameter of the focus region.Method according to Claim 9, wherein a method for edge detection on the at least two surfaces (201, 202, 203, 204) is used to determine the intensity of the reflected portion (102) emerging from the object (110), wherein the method for edge detection is configured to determine a light-dark contrast between the focal points (103) or the groups of focal points (103) and their respective environment on the relevant surface (201, 202, 203, 204).A computer program for determining a spatial location of a non-spherical object (110) having a surface portion (111) of known shape, the computer program comprising instructions which, when the computer program is executed by a computer or a computer network, cause the computer or the computer network to perform at least step c) of the method for determining a spatial location of a non-spherical object (110) having at least one surface portion (111) of known shape according to any of the preceding method claims.Device for determining a spatial position of a non-spherical object (110) having a surface section (111) of known shape, comprising: - at least one light source (50) which is configured to generate at least two light fields (100), each light field (100) having known phase fronts (104), wherein the phase fronts (104) of the at least two light fields (100) differ from one another at least after the objective (70), wherein a curvature of the phase fronts (104) at an exit window of the objective (70) in at least one spatial direction is less than a smallest curvature of the surface section (111) of the object (110), wherein at least one line lying in the surface section (111) exists for at least one of the light fields (100), along which at least two local surface normals (112) of the surface section (111) are orthogonal to the phase front (104) of the at least one of the light fields (100); at least one objective (70) which is configured to irradiate the at least two light fields (100) onto the object (110); at least one detector (80) which is configured to detect a reflected portion (102) of the at least two light fields (100) which originates from the object (110); and at least one evaluation and control device (150) which is configured to determine the spatial position of the non-spherical object (110) from the detected reflected portion (102) of the at least two light fields (100) taking into account an expected backscatter signal which results from the known shape of the surface section (111).The apparatus of the preceding claim, wherein the light source (50) is a laser of a direct writing lithography system.Device according to one of the preceding device claims, wherein the at least one objective (70) is further configured to irradiate at least one light field (105) onto the detector (80).Device according to one of the preceding device claims, further comprising at least one galvanometric scanner (75) which is configured to change at least one of the light fields (100) in a beam path in front of the objective (70).Device according to one of the preceding device claims, further comprising at least one element which is configured for displacing the object (110) and / or the objective (70), preferably selected from a positioning table or an inductive element.Device according to one of the preceding device claims, further comprising at least one diffractive element which is configured to bring about a change in at least one of the light fields (100), wherein the diffractive element is preferably a digital light modulation element, in particular selected from a spatial light modulator or a digital micromirror unit.

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