Measuring arrangement and measuring method for determining optical properties

Abstract

The invention relates to a measuring arrangement (10) for determining optical properties, in particular for determining optical properties of an optical shear plate (20), comprising a measuring beam generator (12) for generating a measuring beam (14), an imaging unit (16), an evaluation unit (18) and an optical shear plate (20) arranged in a beam path of the measuring beam (14) between the measuring beam generator (12) and the imaging unit (16), wherein the shear plate (20) is designed to generate a first partial measuring beam (14a) from the measuring beam (14) and a second partial measuring beam (14b) offset from the first partial measuring beam (14a) from the measuring beam (14), and to deflect the first and second partial measuring beams (14a, 14b) onto an imaging plane (24) of the imaging unit (16);wherein the evaluation unit (18) is designed to evaluate an interference pattern (28) generated by the first partial measuring beam (14a) and the second partial measuring beam (14b) on the imaging plane (24); wherein the measuring arrangement (10) comprises a rotating unit (50) on which the shear plate (20) is arranged; and that the rotating unit (50) is designed to rotate the shear plate (20) about at least one predetermined reference axis (54) of the shear plate (20). The invention also relates to a measuring method (74).

Description

Background of the invention

[0001] The invention relates to a measuring arrangement for determining optical properties, comprising a measuring beam generator for generating a measuring beam, an imaging unit, an evaluation unit, and an optical shear plate arranged in a beam path of the measuring beam between the measuring beam generator and the imaging unit. The shear plate is designed to generate an interference pattern on an imaging plane of the imaging unit. The invention also relates to a measuring method for determining an optical property of the measuring arrangement.

[0002] Such measurement arrangements are used, among other things, as shearing interferometers for determining the degree of collimation, or in other words, the divergence of laser beams. In the production of microchips using EUV lithography, a focusing device is used to focus an excitation laser beam onto a target material to generate extreme ultraviolet (EUV) radiation. To ensure high-precision focusing, determining the exact degree of collimation at the input of the focusing device is crucial.

[0003] Common shearing interferometers are wedge-shaped. When a laser beam is directed onto the wedge, a partial beam is reflected from the front and back sides. Due to the wedge thickness and the wedge angle of the wedge, the partial beams are offset from each other by an angle, which leads to the overlap of the partial beams on an imaging plane and the formation of an interference pattern. By analyzing the interference pattern, conclusions can be drawn, for example, about the degree of collimation of the laser beam.

[0004] To evaluate the interference pattern on conventional shearing interferometers, determining the alignment of the shearing plate to the laser beam is crucial, since, especially with wedge-shaped shearing plates, the interference pattern depends on the position of the shearing plate relative to the laser beam. If the alignment cannot be determined precisely, the evaluation of the interference pattern will exhibit significant measurement inaccuracies. Prior art involves applying a line marking to the shearing plate to indicate the alignment of the shearing plate relative to the alignment of the interference pattern for perfect collimation. However, the formation of the line marking is complex and subject to tolerances, so measurement inaccuracies persist.

[0005] The known inaccuracies of conventional shearing interferometers also prevent their use for determining other optical properties of the measurement setup, such as the wavefront of the laser beam or the wedge angle of the shearing plate. This requires additional, complex tests and / or measurements, which entails considerable effort. Object of the invention

[0006] It is an object of the invention to provide a device and a method for increasing the accuracy and flexibility when determining optical properties of a measuring arrangement. Description of the invention

[0007] This object is achieved according to the invention by a measuring arrangement having the features of patent claim 1. Furthermore, the object is achieved by a measuring method having the features of patent claim 12. The subclaims give preferred embodiments of the invention.

[0008] According to the invention, a measuring arrangement is provided.

[0009] The measuring arrangement is designed to determine optical properties. Optical properties are understood, both before and after, to be the optical properties of the measuring arrangement, in particular a shear plate, a measuring beam, and / or a collimation unit. For example, but not exclusively, optical properties include a degree of collimation of the measuring beam, a wavefront configuration of the measuring beam, an orientation of the shear plate relative to the measuring beam, a shear plate thickness, and / or a wedge angle of the shear plate.

[0010] The measuring arrangement comprises a measuring beam generator, for example, an EUV driver laser. The measuring beam generator is designed to generate the measuring beam – in the case of an EUV driver laser, a partial beam of an excitation laser beam generated by the EUV driver laser can function as the measuring beam. The measuring beam generator can have one or more beam sources. Typically, the measuring beam generator is designed to generate pulsed laser radiation. Preferably, the measuring beam generator comprises one or more optical amplifiers for amplifying the laser radiation, in particular the pulsed radiation. This makes the measuring arrangement particularly suitable for use in the field of EUV lithography.

[0011] The beam source(s) typically generate one or more pre-pulses and / or one or more main pulses that follow one another in close temporal succession. The pre-pulses and the main pulses can originate from one beam source or from different beam sources. The beam sources can generate laser radiation of the same and / or different wavelengths. In particular, CO2 lasers with a wavelength of approximately 10.6 micrometers and / or solid-state lasers in wavelength ranges from 1 micrometer to 3 micrometers are used. Preferably, solid-state lasers with a wavelength of 1 micrometer are used for a pre-pulse, and CO2 lasers with a wavelength of 10.6 micrometers are used for the main pulse.

[0012] The measuring arrangement also has an imaging unit. The imaging unit typically comprises an imaging plane. The imaging unit, or the imaging plane, is preferably designed to visually display incident laser radiation.

[0013] The measuring arrangement also includes an optical shear plate. An optical shear plate is understood above and below to be an optical component designed to guide, in particular reflect and / or refract, light radiation. The optical shear plate is preferably designed to be at least partially transparent to light radiation. The optical shear plate is arranged in a beam path of the measuring beam between the measuring beam generator and the imaging unit.

[0014] The optical shear plate is designed to generate a first partial measuring beam from the measuring beam. In other words, the optical shear plate is designed to at least partially deflect the measuring beam as a first partial measuring beam. Furthermore, the optical shear plate is designed to generate a second partial measuring beam from the measuring beam. The second partial measuring beam is typically offset from the first partial measuring beam. Typically, the second partial measuring beam is radially offset in the propagation direction of the first partial measuring beam.

[0015] The optical shear plate is further configured to deflect the first and second partial measuring beams onto the imaging plane of the imaging unit. Typically, the partial measuring beams are deflected when the partial measuring beams are generated. Deflecting can involve reflecting and / or refracting the measuring beam. Typically, the shear plate has an exit axis to which the first partial measuring beam and / or the second partial measuring beam are deflected parallel.

[0016] Typically, an optical axis of the measuring beam incident on the shear plate and the exit axis of the shear plate form a deflection plane or folding plane.

[0017] By deflecting the radially offset partial measuring beams onto the imaging unit, an image section is created on the imaging plane in which the first partial measuring beam and the second partial measuring beam intersect or overlap. In other words, the light radiation of the first partial measuring beam overlaps the light radiation of the second partial measuring beam. This creates an interference pattern in the imaging section with several parallel interference fringes of varying widths.

[0018] The measuring arrangement also includes an evaluation unit. The evaluation unit typically has at least one computer. The evaluation unit is designed to evaluate the interference pattern generated on the imaging plane by the first partial measuring beam and the second partial measuring beam. Typically, the evaluation unit includes at least one camera for capturing the imaging plane, in particular the imaging section. The evaluation unit is preferably subsequently designed to further process the captured imaging plane.

[0019] According to the invention, the measuring arrangement comprises a rotating unit to which the shear plate is arranged, preferably releasably attached. This allows the rotating unit to be used to determine optical properties on multiple shear plates.

[0020] According to the invention, the rotating unit is designed to rotate the shear plate about at least one predetermined reference axis of the shear plate. A reference axis is understood to be a characteristic axis of the shear plate, both preceding and following. A reference axis can be understood, for example, as a perpendicular to the surface of the shear plate or an orthogonal to the perpendicular to the surface, in particular a wedge axis, of the shear plate.

[0021] Preferably, the rotary unit is designed to rotate the shear plate about two or more reference axes. Rotation about the reference axis can be achieved by directly rotating the reference axis and / or by indirectly rotating the reference axis superimposed by a translational displacement of the rotary unit. Particularly preferably, the rotary unit is designed for motor-driven rotation. Typically, the rotary unit comprises one or more electric motors.

[0022] In summary, a measuring arrangement is specified in which the shear plate can be rotated about one or more reference axes by means of a rotating unit, while a laser beam is deflected via the shear plate onto the imaging unit. This allows multiple interference patterns at known rotation angles to be recorded using the evaluation unit. In other words, an interference pattern graph can be created that shows a change in the interference pattern, in particular an interference fringe spacing, an interference fringe thickness and / or an interference fringe angle as a function of the rotation angle. This allows, on the one hand, the precise alignment of the shear plate to the measuring beam to be determined and, on the other hand, an evaluation of the interference patterns to be carried out independently of the alignment of the shear plate to the measuring beam.The device and measuring method proposed by the invention thus enables particularly precise determination of the optical properties of the measuring arrangement, in particular the alignment of the shear plate and / or the degree of collimation of the measuring beam. The invention eliminates the need for complex and inaccurate line marking.

[0023] In a preferred embodiment of the measuring arrangement, the shear plate has a first optical planar surface. The first optical planar surface is typically formed on a side of the shear plate facing the incident measuring beam. The first optical planar surface is designed to generate the first partial measuring beam by reflecting the measuring beam incident along the optical axis. Reflection of the first partial measuring beam typically occurs at a folding angle, wherein the folding angle is determined by the optical axis of the measuring beam and the exit axis of the shear plate. Preferably, the degree of deflection or reflection is determined by a folding half-angle, wherein the folding half-angle is formed between the optical axis of the measuring beam and a surface normal to the first optical planar surface.

[0024] A preferred embodiment of the measuring arrangement is one in which the first optical planar surface is designed to generate the second partial measuring beam. The shear plate is designed to generate the second partial measuring beam by partially refracting the incident measuring beam. In other words, the first optical planar surface is designed to generate the first partial measuring beam and the second partial measuring beam from the measuring beam.

[0025] A further preferred embodiment of the measuring arrangement is one in which the shear plate has a second optical planar surface. The second optical planar surface is arranged downstream of the first optical planar surface along the optical axis of the measuring beam, or is formed on the shear plate. The second optical planar surface is designed to reflect the second partial measuring beam in the direction of the first optical planar surface. In other words, the second partial measuring beam refracted by the first optical planar surface in the direction of the second optical planar surface is reflected back to the first optical planar surface by the second optical planar surface.

[0026] A further preferred embodiment of the measuring arrangement is one in which the first optical plane surface is designed to refract the second partial measuring beam reflected by the second optical plane surface. Typically, the second partial measuring beam is refracted by the first optical plane surface parallel to the shear plate's axis of incidence. This allows the first partial measuring beam and the second partial measuring beam to be aligned with a radial offset from one another using only one optical component.

[0027] In a preferred embodiment of the measuring arrangement, the at least one predetermined reference axis is designed as a surface normal to the first optical plane surface and / or as an orthogonal to the surface normal to the first optical plane surface. In other words, the rotation unit can be designed to rotate the shear plate about the surface normal to the first optical plane surface and / or to rotate about an axis oriented orthogonally to the surface normal to the first optical plane surface. In a particular embodiment, the orthogonal is designed perpendicular to the surface normal to the first optical plane surface and perpendicular to a wedge axis of the shear plate. The inventors have recognized that rotation about the aforementioned reference axes can be carried out particularly reliably and ensures particularly precise evaluation of the interference patterns.

[0028] Alternatively or additionally, it can also be provided that the predetermined reference axis is formed as a surface normal of the second optical planar surface or as a resultant of the assumed surface normal of the first optical planar surface and the assumed surface normal of the second optical planar surface.

[0029] Further preferred is an embodiment of the measuring arrangement in which the rotary unit is designed to rotate the shear plate about two mutually perpendicular reference axes. For example, the rotary unit can be designed to rotate the shear plate about the perpendicular to the surface of the first optical plane surface and to rotate the shear plate about the perpendicular to the surface. This allows the interference patterns to be evaluated taking into account various rotational movements of the shear plate, thereby increasing the accuracy of the evaluation.

[0030] In a preferred embodiment of the measuring arrangement, the first optical plane surface and the second optical plane surface of the shear plate are parallel to each other. This eliminates the need to determine and / or consider a wedge axis. Typically, the interference patterns are evaluated by determining the interference fringe thickness and / or the interference fringe spacing.

[0031] An alternative embodiment of the measuring arrangement is preferred in which the first optical plane surface and the second optical plane surface of the shear plate form an optical wedge. In other words, the first optical plane surface and the second optical plane surface extend obliquely to one another and form the wedge angle. By forming a wedge angle, a rotation of the interference pattern can be detected and evaluated depending on the degree of collimation of the measuring beam. In particular, an interference fringe angle can be evaluated to determine the degree of collimation of the measuring beam.

[0032] In a preferred embodiment of the measuring arrangement, the optical wedge has a wedge angle of at most 2 degrees, preferably of at most 1 degree, particularly preferably of at most 0.5 degrees. This allows a defined offset between the first partial measuring beam and the second partial measuring beam to be achieved, while simultaneously maintaining the overlap area of ​​the partial measuring beams on the imaging plane.

[0033] Furthermore, an embodiment of the measuring arrangement is preferred in which the evaluation unit is designed to automatically determine optical properties. Automatic evaluation is understood to mean the evaluation of the detected interference patterns or the generated interference pattern graph without further intervention by an operator. In particular, the automatic determination of a reference axis of the shear plate and / or a wavefront configuration of the measuring beam can be provided. This allows for automated use in a laser processing machine, for example, in EUV lithography, for the automated calibration of a focusing unit.

[0034] The underlying task is also solved by a measurement method.

[0035] The measurement method is designed to determine optical properties. In particular, the measurement method is designed to determine optical properties of a measurement setup described above and below. The measurement method is particularly suitable for EUV lithography and also particularly suitable for use in an EUV driver laser.

[0036] The measuring method comprises at least the following method steps: In method step a) of the measuring method, a measuring beam is aligned to an imaging plane of an imaging unit, wherein an interference pattern consisting of a first partial measuring beam and a second partial measuring beam offset transversely to the propagation direction of the first partial measuring beam is generated on the imaging plane by means of a shear plate. In other words, a first partial measuring beam and a second partial measuring beam are generated from the measuring beam directed onto the shear plate by the shear plate and deflected onto the imaging unit, thereby generating an interference pattern in the overlap region of the partial measuring beams on the imaging plane.

[0037] In a subsequent method step b) of the measuring method, the shear plate is rotated about at least one predetermined reference axis of the shear plate. During the rotation, an interference pattern graph is generated by an evaluation unit detecting the interference pattern as a function of the angle of rotation. The interference pattern graph is preferably generated by an evaluation device as described above and below.

[0038] The interference pattern graph may, for example, have a dependence of an interference fringe angle of the interference fringes, an interference fringe width of the interference fringes and / or an interference fringe spacing on a rotation angle.

[0039] A further method step c) of the measuring method provides for determining an optical property by evaluating the interference pattern graph by the evaluation unit. The evaluation can provide for a comparison of the interference pattern graph with reference lines. Furthermore, the evaluation of the interference pattern graph can provide for a zero point analysis and / or an extreme point analysis. From an evaluation of the interference pattern graph, for example, a maximum and / or minimum interference fringe angle, a maximum and / or minimum interference fringe spacing, and / or a maximum and / or minimum interference fringe width can be determined. This allows conclusions to be drawn about the optical properties of the measuring arrangement.

[0040] In step d) of the measurement method, the determined optical property is output. Preferably, the determined optical property is output graphically. Particularly preferably, the measurement setup is automatically adjusted based on the determined optical property. This can increase the degree of automation.

[0041] In a preferred embodiment of the measuring method, continuous rotation around a reference axis occurs in method step b). Continuous rotation is understood as an uninterrupted progression of the rotational movement. Typically, continuous rotation involves at least one revolution, or 360 degrees. Particularly preferred is continuous rotation around a perpendicular to the surface of the shear plate. This allows the alignment of the shear plate to be determined particularly accurately.

[0042] Further preferred is an embodiment of the measuring method in which stepwise rotation is provided in method step b). Stepwise rotation is to be understood as a rotational movement interrupted in time. Typically, a single rotation step covers an angular range of at least 2 degrees, particularly preferably at least 5 degrees. Stepwise rotation can comprise multiple rotation steps. Preferably, stepwise rotation occurs around an orthogonal line to a surface perpendicular to the shear plate.

[0043] Further preferred is an embodiment of the measuring method in which an orientation of the wedge axis of the shear plate is determined in method step c). For this purpose, a continuous rotational movement about the surface normal and a step-by-step rotation about the orthogonal are preferably carried out in method step b). Typically, a continuous rotation about the surface normal with at least one revolution takes place, followed by a step-by-step rotation about the orthogonal. This can generate an interference pattern graph with a family of curves. The orientation of the wedge axis can then be determined, for example, by determining the intersection points from the family of curves and / or by determining a maximum deviation of an interference fringe angle.

[0044] Furthermore, an embodiment of the measuring method is preferred in which, in method step c), a wavefront formation of the measuring beam is determined. For example, by evaluating the direction of rotation of the interference fringes when rotated about a surface perpendicular, it can be determined whether the wavefront is concave or convex.

[0045] Further advantages of the invention will become apparent from the description and the drawings. Likewise, the above-mentioned and further-described features can be used individually or in combination in any desired manner. The embodiments shown and described are not intended to be exhaustive, but rather are exemplary in nature for describing the invention. Detailed description of the invention and drawing Fig. 1 shows a schematic representation of a measuring arrangement according to the invention for determining optical properties with a shear plate arranged on a rotating unit. Fig. 2 shows a schematic representation of an interference pattern graph generated by an evaluation unit of the measuring arrangement. Fig. 3 shows a schematic representation of a measuring method according to the invention for determining optical properties of a measuring arrangement.

[0046] Fig. 1 shows a measuring arrangement 10 for determining optical properties in a schematic representation.

[0047] The measuring arrangement 10 has at least one measuring beam generator 12 for generating a measuring beam 14. The measuring beam 14 is typically designed as a laser beam.

[0048] The measuring arrangement 10 also has an imaging unit 16 for imaging the measuring beam 14. The imaging unit 16 is typically designed to display the measuring beam 14 in a visually detectable wavelength range.

[0049] The measuring arrangement 10 also has an evaluation unit 18 for capturing and evaluating the measuring beam 14 imaged on the imaging unit 16. The evaluation unit 18 preferably comprises a camera for capturing the imaged measuring beam 14 in a digital or computer-processable data format. Further preferably, the evaluation unit 18 is configured to evaluate the imaged measuring beam 14, in particular automatically, using stored evaluation algorithms.

[0050] Furthermore, the measuring arrangement 10 comprises an optical shear plate 20, which is designed to deflect the measuring beam 14 onto the imaging unit 16.

[0051] In the present case, the measuring beam 14 only has, for example, a coherence length that satisfies the following condition: lc>>2*σ*n, where I c a coherence length of the measuring beam 14, σ a thickness of the shear plate 20 and n a refractive index of the shear plate 20.

[0052] According to the invention, the shear plate 20 is designed to generate a first partial measuring beam 14a from the measuring beam 14 and a second partial measuring beam 14b, radially offset from the first partial measuring beam 14a, from the measuring beam 14. In other words, by means of the shear plate 20, two separate partial measuring beams 14a, 14b are generated from the measuring beam 14 incident along an optical axis 22.

[0053] The partial measuring beams 14a, 14b are deflected by the shear plate 20 onto an imaging plane 24 of the imaging unit 16, whereby an interference pattern 28 is generated in an imaging section 26 as a result of an overlap of the partial measuring beams 14a, 14b. The imaging plane 22 is shown rotated 90 degrees relative to the drawing plane for clarity.

[0054] As shown, the first partial measuring beam 14a is generated by partially reflecting the measuring beam 14 at a first optical plane surface 30 of the shear plate 20. The first partial measuring beam 14a is typically deflected or folded along a reflection axis 32 in the direction of the imaging unit 16 or the imaging plane 24. The degree of deflection can be determined by a folding half-angle 34 between the optical axis 22 and a surface normal 36 of the first optical plane surface 30. A folding half-angle 34 can, as shown, be 45 degrees, whereby the first partial measuring beam 14a is deflected or folded by 90 degrees.

[0055] The optical axis 22 of the measuring beam 14 and the exit axis 32 of the first partial measuring beam 14a typically form a folding plane 38. The surface normal 36 typically lies in the folding plane 38.

[0056] As shown, the second partial measuring beam 14b can be generated by refracting the measuring beam 14 at the first optical plane surface 30. Typically, the second partial measuring beam 14b is first refracted in the direction of a second optical plane surface 40 of the shear plate 20, which is located behind the first optical plane surface 30 in the propagation direction (indicated by the arrow directions) of the measuring beam 14. Preferably, the second partial measuring beam 14b is reflected at the second optical plane surface 40 in the direction of the first optical plane surface 30 and then, as shown, refracted at the first optical plane surface 30 in the direction of the imaging unit 16. As a result, two partial measuring beams 14a, 14b can be generated from one measuring beam 14, which are offset transversely to the axis of incidence 32.

[0057] Preferably, the second optical plane surface 40 is formed at an end of the shear plate 20 facing away from the first optical plane surface 30. Further preferably, the shear plate 20 has a constant refractive index. The shear plate 20 can be formed from a homogeneous yet translucent material, typically glass.

[0058] The first optical plane surface 30 and the second optical plane surface 40 of the shear plate 20 can be formed parallel to each other.

[0059] Alternatively and preferably, the first optical planar surface 30 and the second optical planar surface 40 of the shear plate 20 can form an optical wedge, as shown. In other words, the first optical planar surface 30 and the second optical planar surface 40 can enclose a wedge angle 42.

[0060] The specific arrangement of the optical plane surfaces 30, 40, i.e., both in a parallel arrangement and in an angled arrangement when configured as an optical wedge, allows rotation of the interference pattern 28 to be effected depending on a corresponding wavefront configuration of the measuring beam 14, for example, a convex or concave wavefront. This enables, for example, the determination of a convergent or divergent configuration of the measuring beam 14.

[0061] Typically, the shear plate 20 configured as an optical wedge has a wedge axis 44. The wedge axis 44 typically lies in the first optical plane surface 30 and can be used to determine a local wedge thickness 46 perpendicular to the first optical plane surface 30. The wedge axis 44 can thus be understood as a reference for a wedge alignment of the optical shear plate 20.

[0062] As shown, the measuring arrangement 10 has a collimation unit 48 for collimating the measuring beam 14 generated by the measuring beam generator 12. This allows a collimated or rectified measuring beam 14 with a flat wavefront to be formed, which, for example, allows the optical properties of the shear plate 20 to be determined particularly accurately.

[0063] According to the invention, the measuring arrangement 10 comprises a rotating unit 50 on which the shear plate 20 is arranged. Preferably, the shear plate 20 is detachably arranged or attached to the rotating unit 50. The rotating unit 50 has at least one, as shown, three, axes of rotation 52a-c.

[0064] Preferably, at least one of the rotation axes 52a-c is designed as a reference axis 54 of the shear plate 20. Typically, the surface normal 36 and / or the wedge axis 44 of the optical shear plate 20 is to be understood as a reference axis 54 of the shear plate 20. Furthermore, an orthogonal line 56, which is formed perpendicular to the surface normal and in particular perpendicular to the wedge axis 44, can be understood as a reference axis 54.

[0065] As shown, the rotating unit 50 is designed to rotate the shear plate 20 about the surface perpendicular 36. Furthermore, the alignment of the shear plate 20 relative to the optical axis 22 can be adjusted by rotating it about the rotation axes 52b, 52c.

[0066] In a particular embodiment, the rotating unit 50 can be designed to be movable parallel to the optical axis 22, represented by the arrow 58. This allows the alignment of the shear plate 22 with respect to the optical axis 22 to be even more precise.

[0067] The rotating unit 50 can be configured to perform a continuous and / or step-by-step rotary movement. Furthermore, the rotating unit 50 can be configured to perform rotary movements of less than 360 degrees and / or to perform one or more revolutions of more than 360 degrees. The rotating unit 50 can also be configured to perform rotary movements in different directions.

[0068] One use of the measuring arrangement 10 provides for the shear plate 20 to be rotated during the irradiation of the imaging device 16. As a result, an effect on the interference pattern 28 attributable to the formation of the measuring beam 14 can be superimposed by an effect on the interference pattern 28 attributable to the alignment of the shear plate 20 to the optical axis 22.

[0069] The evaluation unit 18 records the generated interference pattern 28 as a function of the angle of rotation. In other words, the change in the interference pattern 28 when rotating the shear plate 20 is recorded. Preferably, an interference pattern graph 60 (see Fig. 2) generated and evaluated by the evaluation unit 18.

[0070] An evaluation by the evaluation unit 18 typically involves separating the effect on the interference pattern 28 attributable to the formation of the measuring beam 14 from the effect on the interference pattern 28 attributable to the alignment of the shear plate 20. This subsequently allows for an exact determination of optical properties, for example, of the measuring beam 14 and / or the optical shear plate 20.

[0071] The evaluation unit 18 is preferably designed to automatically determine optical properties. In other words, evaluation by the evaluation unit 18 can be performed without operator intervention, allowing for a particularly fast and automated determination of the optical properties.

[0072] Particularly preferably, the evaluation unit 18 is designed to determine a reference axis 54 of the shear plate 20, the wedge angle 42 of the shear plate 20 and / or a formation of the wavefront of the measuring beam 14.

[0073] In summary, the measuring arrangement 10 described above and below is suitable and designed for determining optical properties of an optical shear plate 12 or an optical property of a measuring beam 14.

[0074] Fig. 2 shows an interference pattern graph 60. Typically, the interference pattern graph 60 is generated by means of an evaluation unit 18 described above and below (see Fig. 1) was created.

[0075] The Fig. The interference pattern graph 60 shown in Figure 2 is described below using an exemplary determination of a wavefront formation of the measuring beam 14 (see Fig. 1). In other words, a beam divergence, or the converging or diverging beam propagation, of the measuring beam 14 is determined starting from a perfectly collimated beam.

[0076] As shown, the interference pattern graph 60 has an interference fringe angle 62, which was detected by the evaluation unit 18 as a function of a wedge rotation angle 64. The wedge rotation angle 64 typically relates to a rotation of the shear plate 20 (see Fig. 1) around the surface perpendicular 36 (see Fig. 1). Under a wedge rotation angle 64, the position change of the wedge axis 44 (see Fig. 1) when rotating the shear plate 20 about the surface normal 36. Preferably, the interference pattern graph 60 has been generated over a wedge rotation angle 64 of at least 360 degrees, preferably 720 degrees. The interference pattern graph 60 shows - here three - angle profiles 66a-c, which are for three different folding half-angles 34 (see Fig. 1). In other words, the interference pattern graph 60 shown is created by repeatedly rotating the shear plate 20 (see Fig. 1) around a reference axis 54, here the surface perpendicular 36 of the first optical plane surface 30, and by gradually rotating the optical shear plate 20 around the orthogonal 56 (see Fig. 1) was created.

[0077] At an interference fringe angle 62, the inclination of interference fringe 68 (see Fig. 1) compared to an unchanging or fixed-position reference line 70 (see Fig. 1) be understood.

[0078] The inventors have recognized that the effect of the beam divergence of the measuring beam 14 on the interference fringe angle 62 is maximum when the wedge axis 44 is aligned perpendicular to the folding plane 38 and minimum when the wedge axis 44 is aligned in the folding plane 38.

[0079] An evaluation may provide for a minimal change in the interference fringe angle 62 to be determined from one of the angle profiles 66a-c in order to determine the orientation of the wedge axis 44. Furthermore, it may be provided for the intersection points 72 of the angle profiles 66a-c to be determined. At the intersection points 72 of the angle profiles 66a-c, there is no influence of the beam divergence, so that the intersection points 72 determine the angular position of the wedge axis 44. This allows the orientation of the shear plate 20 to be determined.

[0080] An interference pattern graph 60 may alternatively or additionally include an interference fringe thickness (not shown) of the interference fringes 68 and / or an interference fringe spacing 73 (see Fig. 1) depending on an angle of rotation.

[0081] Fig. 3 shows a schematic representation of a measuring method 74 according to the invention.

[0082] The measuring method 74 is designed to determine optical properties of a measuring arrangement 10, in particular as described previously and subsequently.

[0083] The measuring method 74 comprises at least the following process steps: In a method step 76 of the measuring method 74, the measuring beam 14 is aligned (see Fig. 1) is provided on the imaging plane 24 of the imaging unit 16, particularly described previously and subsequently. The alignment of the measuring beam 14 is carried out by means of the shear plate 20 (see Fig. 1), wherein the first and the second partial measuring beam 14a, 14b are generated by the shear plate 20 and deflected radially offset from each other onto the imaging plane 24. In an imaging region 26 of the imaging plane 24, in which the first partial measuring beam 14a and the second partial measuring beam 14b overlap, an interference pattern 28 (see Fig. 1) is generated.

[0084] In a further method step 78 of the measuring method 74, the shear plate 20 is rotated about at least one predetermined reference axis 54 (see Fig. 1) of the shear plate 20. Typically, rotation occurs about two or more reference axes 54. Preferably, rotation of the shear plate 20 occurs at least about the surface normal 36 (see Fig. 1) and / or the orthogonal 56 (see Fig. 1).

[0085] During the rotation of the shear plate 20, an interference pattern graph 60 (see Fig. 2) by detecting the interference pattern 28 (see Fig. 1) depending on the angle of rotation, in particular the wedge rotation angle 64 (see Fig. 2) by the evaluation unit 18 (see Fig. 1) is generated.

[0086] The rotation can be continuous or stepwise. Continuous rotation preferably comprises rotation of at least 360 degrees, more preferably of 720 degrees or more. Stepwise rotation typically comprises tilting about a rotation axis 52a-c (see Fig. 1) and / or about a reference axis 54. Tilting preferably occurs by at least 2 degrees, particularly preferably by at least 5 degrees.

[0087] A subsequent method step 80 of the measuring method 74 provides for the determination of at least one optical property by evaluating the interference pattern graph 60 by the evaluation unit 18.

[0088] An evaluation can in particular provide for the determination of a beam divergence of the measuring beam 14, or a concave or convergent wavefront of the measuring beam 14. In this way, a degree of collimation or, in other words, a beam divergence of the measuring beam 14 can be determined. Subsequently, it can be provided that the collimation unit 48 (see Fig. 1) is adjusted to increase the degree of collimation of the measuring beam 14.

[0089] An evaluation may alternatively or additionally provide that an alignment of the wedge axis 44 of the shear plate 20 and / or a wedge angle 42 (see Fig. 1) of the shear plate 20. This allows for a more precise adjustment of a shearing interferometer.

[0090] A further method step 82 of the measurement method 74 provides for outputting the determined optical property. Output typically occurs in the form of a graphical output to an operator (not shown).

[0091] Alternatively or additionally, it may be provided that an output of the determined optical property is used to automatically correct the measuring arrangement 10. For example, it may be provided that an alignment of the shear plate 20 and / or an alignment of the collimation unit 48 is corrected. List of reference symbols 10 measuring arrangement; 12 measuring beam generators; 14 measuring beam; 14a first partial measuring beam; 14b second partial measuring beam; 16 imaging unit; 18 evaluation unit; 20 shear plate; 22 optical axis; 24 imaging plane; 26 Figure section; 28 interference patterns; 30 first optical plane surface; 32 dropout axle; 34 folding half angles; 36 surface perpendiculars; 38 folding plane; 40 second optical plane surface; 42 wedge angles; 44 wedge axis; 46 wedge thickness; 48 collimation unit; 50 rotating unit; 52a-c rotation axis; 54 Reference axis; 56 orthogonals; 58 arrow; 60 interference pattern graph; 62 interference fringe angles; 64 wedge rotation angles; 66a-c angle gradients; 68 interference fringes; 70 reference line; 72 intersection points; 73 interference fringe spacing; 74 measurement methods; 76 process steps; 78 process steps; 80 process steps; 82 process steps.

Claims

[1] Measuring arrangement (10) for determining optical properties, in particular for determining optical properties of an optical shear plate (20), comprising a measuring beam generator (12) for generating a measuring beam (14), an imaging unit (16), an evaluation unit (18) and an optical shear plate (20) arranged in a beam path of the measuring beam (14) between the measuring beam generator (12) and the imaging unit (16), wherein the shear plate (20) is designed to generate a first partial measuring beam (14a) from the measuring beam (14) and a second partial measuring beam (14b) offset from the first partial measuring beam (14a) from the measuring beam (14) and to deflect the first and second partial measuring beams (14a, 14b) onto an imaging plane (24) of the imaging unit (16); wherein the evaluation unit (18) is designed to evaluate an interference pattern (28) generated by the first partial measuring beam (14a) and the second partial measuring beam (14b) on the imaging plane (24); characterized by that the measuring arrangement (10) comprises a rotating unit (50) on which the shear plate (20) is arranged; and that the rotating unit (50) is designed to rotate the shear plate (20) about at least one predetermined reference axis (54) of the shear plate (20). [2] Measuring arrangement (10) according to claim 1, characterized by that the shear plate (20) has a first optical planar surface (30) for generating the first partial measuring beam (14a) by, in particular partially, reflecting the measuring beam (14) incident along an optical axis (22). [3] Measuring arrangement (10) according to claim 2, characterized bythat the first optical planar surface (30) is designed to generate the second partial measuring beam (14b) by partially refracting the incident measuring beam (14). [4] Measuring arrangement (10) according to claim 3, characterized by in that the shear plate (20) has a second optical planar surface (40) arranged downstream of the first optical planar surface (30) along a propagation direction of the measuring beam (14) for at least partially reflecting the second partial measuring beam (14b) in the direction of the first optical planar surface (30). [5] Measuring arrangement (10) according to claim 4, characterized by that the first optical plane surface (30) is designed to refract the second partial measuring beam (14b) reflected by the second optical plane surface (40). [6] Measuring arrangement (10) according to one of the preceding claims, characterized bythat the at least one predetermined reference axis (54) is designed as a surface normal (36) of the first optical planar surface (30) and / or as an orthogonal (56) of the surface normal (36) of the first optical planar surface (30). [7] Measuring arrangement (10) according to one of the preceding claims, characterized by that the rotating unit (50) is designed to rotate the shear plate (20) about two mutually perpendicular reference axes (54). [8] Measuring arrangement (10) according to one of the preceding claims, characterized by that the first optical plane surface (30) and the second optical plane surface (40) of the shear plate (20) are formed parallel to one another. [9] Measuring arrangement (10) according to one of claims 1 to 7, characterized by that the first optical plane surface (30) and the second optical plane surface (40) of the shear plate (20) form an optical wedge. [10] Measuring arrangement (10) according to claim 9, characterized bythat the optical wedge has a wedge angle (42) of at most 2 degrees, preferably of at most 1 degree, particularly preferably of at most 0.5 degrees. [11] Measuring arrangement (10) according to one of the preceding claims, characterized by that the evaluation unit (18) is designed to automatically determine optical properties, in particular a reference axis (54) of the shear plate (20) and / or a formation of the wavefront of the measuring beam (14), from an interference pattern (28) generated on the imaging plane (24) by the first partial measuring beam (14a) and the second partial measuring beam (14b). [12] Measuring method (74) for determining optical properties of a measuring arrangement (10), in particular according to one of the preceding claims, characterized by the procedural steps: a) aligning (76) a measuring beam (14) onto an imaging plane (24) of an imaging unit (16) by means of a shear plate (20), whereby an interference pattern (28) is generated on the imaging plane (24) from a first partial measuring beam (14a) and a second partial measuring beam (14b) offset radially to the propagation direction of the first partial measuring beam (14a); b) rotating (78) the shear plate (20) about at least one predetermined reference axis (54) of the shear plate (20), wherein an interference pattern graph (60) is generated by detecting the interference pattern (28) as a function of the angle of rotation by an evaluation unit (18); c) determining (80) an optical property by evaluating the interference pattern graph (60) by the evaluation unit (18); d) outputting (82) the determined optical property. [13] Measuring method (74) according to claim 12, wherein in method step b) a continuous rotation about a surface perpendicular (36) of the shear plate (20) takes place, wherein the shear plate (20) is preferably rotated by at least 360 degrees. [14] Measuring method (74) according to claim 12 or 13, wherein in method step b) a stepwise rotation about an orthogonal (56) of a surface perpendicular (36) of the shear plate (20) takes place, wherein the shear plate (20) is preferably rotated by at least 5 degrees. [15] Measuring method (74) according to one of claims 12 to 14, wherein in method step c) an orientation of a wedge axis (44) of the shear plate (20) is determined. [16] Measuring method (74) according to one of claims 12 to 15, wherein in method step c) a wavefront formation of the measuring beam (14) is determined.

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