Measuring device and positioning device and method for relative positioning of measuring device having terahertz device

Abstract

The invention relates to a measuring device (11), a positioning device (50) and a method for relatively positioning a measuring device (11) having a terahertz device (16), in which a transmitter (17) for outputting emitted radiation (18) and a receiver (19) for detecting received radiation (20) are provided, both having an object-side focal point (30), at least one reflecting element (24, 54) with at least one angle adjusting element (24a, 24b) is arranged in the transmitting radiation (18) and the receiving radiation (20), and the at least one angle adjusting element (24a, 24b) can be controlled by the controller (25) in order to vary the angular position of the reflecting element (24, 54) in at least one spatial direction, the object-side focal point (30) of the emission radiation (18) and the reception radiation (20) and the at least one rotation center (21) of the emission radiation (18) and the reception radiation (20) coincide with each other.

Description

Technical Field

[0001] The invention relates to a measuring device having a terahertz (THz) device for emitting and receiving THz radiation to measure an object.

[0002] Furthermore, the present invention relates to a positioning device and a method for relative positioning of a measuring device having a terahertz device for performing measurements on a measurement object. Background Art

[0003] DE 102018126652 A1 discloses a method and system for aligning a terahertz sensor with a target surface of an object. The target surface may be, for example, a layer of paint on a vehicle, so that a sensor head of a terahertz sensor system can detect the thickness of one or more layers of paint on the vehicle body, for example. A manipulator is used to position the terahertz sensor relative to the target surface. To align the sensor head with the target surface, an estimated normal of the sensor head relative to the target surface is first determined. A light beam is then scanned across a selected area of ​​the target surface to identify an optimal normal based on the maximum peak amplitude. After determining the optimal normal, the sensor head is aligned relative to the target surface of the object based on the determined optimal normal to perform measurements on the object.

[0004] US 2008 / 0251720 A1 describes an image acquisition device in which terahertz radiation is directed onto a deflection mirror to direct the radiation onto the measurement object. The deflection mirror rotates about an axis, enabling transverse scanning of the surface of the measurement object. A similar device is known from US 2021 / 0389238 A1.

[0005] US2018 / 03476963A1 discloses a method for measuring coating thickness using a terahertz device for emitting and receiving terahertz radiation. It is proposed that lateral movement is controlled for coating thickness measurement to achieve different optical axes between the terahertz device and the measurement object.

[0006] DE 102013223945 A1 discloses a measuring device for measuring a test object, in particular for measuring the entire surface of a test object designed as a plastic tube with a circular cross-section. For this purpose, the measuring device comprises a transmitter-receiver unit and a mirror arrangement comprising a first mirror and a second mirror. The radiation reflected from the test object is evaluated by a control unit.

[0007] WO 2020 / 239694A1 discloses a method for performing coating thickness measurement using a terahertz device for emitting and receiving terahertz radiation, wherein the measuring device includes a sensor for distance measurement and a further sensor for angle measurement, and the recorded parameters of the two sensors are taken into account when evaluating the received radiation.

[0008] US 2015 / 0212060 A1 discloses a detection system for characterizing coatings, such as paint layers, using terahertz radiation. A terahertz device for emitting and receiving terahertz radiation is mounted on a manipulator. To measure coating thickness, the manipulator aligns the terahertz device with the surface of the object being measured and moves the device along the surface.

[0009] WO 2022 / 135763 A1 discloses a method for detecting a coating on a measurement object. The method includes a terahertz device for emitting and receiving terahertz radiation to measure the measurement object, in particular, to measure the coating thickness. The detected received radiation is compared with stored reference data to enable rapid evaluation and output of the detected received radiation. Summary of the Invention

[0010] The present invention is based on the object of providing a measuring device and a positioning apparatus, as well as a method for relative positioning of a measuring device having a terahertz device for emitting and receiving terahertz radiation for performing measurements on a measurement object, thereby reducing the cycle time for positioning the terahertz device relative to the measurement object for performing the measurements.

[0011] This object is achieved by a measuring device having a terahertz device for emitting and receiving terahertz radiation for performing measurements on a measurement object, in particular coating thickness measurements, wherein the emitted radiation and the received radiation are coaxially aligned with each other, wherein at least one reflective element having at least one angular adjustment element is provided in the emitted radiation and the received radiation, wherein the at least one angular adjustment element is controllable by a controller to change the angular position of the at least one reflective element in at least one spatial direction, and wherein the object-side focal point of the emitted radiation and the received radiation coincides with at least one rotation center of the emitted radiation and the received radiation, preferably with all rotation centers of the emitted radiation and the received radiation. This design of the measuring device enables rapid alignment of the emitted radiation and the received radiation of the terahertz device to correct angular tolerances, in particular after positioning the measuring device at a distance from the object to be measured. Furthermore, the association of the at least one rotation center of the emitted radiation and the received radiation with the object-side focal point of the emitted radiation and the received radiation enables distance-independent correction when the angular position of the at least one reflective element changes. Therefore, the cycle time for positioning and accurately aligning the terahertz device with respect to the measurement object can be reduced, and accurate measurement of the measurement object can be performed.

[0012] Furthermore, it is preferred that at least one optical device be provided between a reflective element and the object-side focal point of the emitted and received radiation, and that the rotation center of the reflective element be located at a conjugate focal point relative to the object plane of the optical device, with the object-side focal point located in the object plane of the optical device. The optical device is preferably provided with an imaging optical device to align the emitted and received radiation with the rotation center. To correct the angular position of the tilted object plane of the measurement object, the rotation center of at least one reflective element is preferably designed as the rotation axis of the reflective element. By controlling the rotational movement about at least one rotation axis, any angular tolerances can be quickly and easily corrected. The relative angular movement of the emitted and received radiation relative to the measurement object is performed so that the rotation centers of the emitted and received radiation are located at the object-side focal point.

[0013] Due to the optical arrangement of the transmitted and received radiation, the object-side focal point is preferably located in the object plane of the measurement object, and the conjugate image-side focal points of the transmitted and received radiation are located on the at least one reflective element. This enables rapid correction of detected angular deviations and improves the evaluation of the received radiation for angular correction.

[0014] The optical device may include at least one optical element, such as a spherical lens, a parabolic mirror, or an aspherical lens, which can simplify the structural design.

[0015] According to a first embodiment, a single optical element is provided between the terahertz device and the optical device. Preferably, two reflective elements are provided, aligned with one another. At least one of the two reflective elements associated with the optical element can be adjusted in at least one spatial direction, preferably in two spatial directions. For example, at least one reflective element is designed as a tilting mirror with one or two rotation axes to vary the angular position. In this embodiment, a preferred optical element is a parabolic mirror in the collimated beam path.

[0016] Alternatively, the optical device may include two optical elements, the two optical elements being aligned with each other relative to an optical axis of the optical device and being arranged between a reflective element and the object-side focal point. This arrangement can result in a low distance dependency of the measurement device with respect to positioning relative to the measurement object.

[0017] Furthermore, it is preferred that the optical arrangement having two optical elements includes a first optical element and a second optical element, wherein the first optical element has a focal length f1 assigned to one of the reflective elements, and the second optical element has a focal length f2 assigned to the object-side focal point, wherein focal length f2 > focal length f1. This arrangement enables a larger or longer focal point in the direction of the object-side focal point, thereby reducing the distance sensitivity of the converging radiation.

[0018] Advantageously, the optical arrangement is designed for high distance tolerances and in particular comprises long focal length optics, the Rayleigh length of the emitted and received radiation of which is preferably greater than 6 mm, in particular greater than 10 mm, at a frequency of 1 THz. Advantageously, the distance tolerance can be increased by additional corrections on the software side.

[0019] According to another preferred embodiment, it can be provided that a distance and / or angle measurement between a measuring device and a measurement object is provided by detecting terahertz pulses using terahertz radiation. For example, when the measuring device is close to the object to be measured, the emitted and received radiation of the terahertz device can be used to measure the distance. Angle measurements can be performed in an overlapping or simultaneous manner, which reduces the time required for precise alignment of the measuring device and the measurement object. Advantageously, the change in the angular position of at least one reflective element of the optical device can be controlled during the distance and / or angle measurement, thereby enabling rapid correction if the distance and / or angle tolerances are exceeded.

[0020] Preferably, at least one independent sensor for measuring the distance and / or angle between the measuring device and the measured object is provided on or in the measuring device. In particular, the independent sensor can be used when the measuring device approaches the object to be measured for the first time.

[0021] Advantageously, the sensor is designed as an optical sensor. Advantageously, the at least one independent optical sensor is capable of operating with radiation in the visible or near-infrared range. This also makes it possible to detect and monitor the measurement surface of the measurement object. Advantageously, this makes it possible for the distance and / or angle measurement to be recorded by the optical sensor at an even greater distance from the measurement device to the measurement object and then for the distance and / or angle measurement to be performed in a smaller measurement range via precise measurement using terahertz radiation. The superimposition of these two distance and / or angle measurements makes it possible to achieve further cycle time optimization.

[0022] Advantageously, the emission and / or reception radiation of the at least one independent sensor is coaxially aligned with the emission and reception radiation of the terahertz device. In particular, the independent optical sensor located between the terahertz device and the at least one reflective element can be superimposed with the terahertz radiation of the terahertz device. This makes it possible to simultaneously scan the surface of the measurement object.

[0023] Advantageously, the optical coupling element is provided for coaxially superimposing the emission and / or reception radiation of the independent sensor with the emission and reception radiation of the terahertz device, the optical coupling element being designed as a reflective element for the emission and reception radiation of the terahertz device. The coupling element can also be the first reflective element. This makes it possible to make the arrangement compact. Such a coupling element can be designed, for example, as a glass element with an indium tin oxide coating. Alternatively, a film with this dual function can also be used.

[0024] The task underlying the application is also solved by a positioning device for the relative positioning of a measuring device with respect to a measurement object for measuring the measurement object, the measuring device having a terahertz device for emitting and / or receiving terahertz radiation. The positioning device has a handling device having a connection junction which is assigned to an external nominal operating point, wherein the measuring device according to one of the above-mentioned embodiments is arranged at the connection junction of the handling device and the object-side focal point of the emitted and received radiation of the terahertz device coincides with at least one, preferably all, centers of rotation of the emitted and received radiation of the terahertz device, advantageously the object-side focal point of the emitted and received radiation of the terahertz device and at least one center of rotation of the emitted and received radiation of the terahertz device coincide with the external nominal operating point of the handling device and the object-side focal point of the emitted and received radiation of the terahertz device can be positioned by the handling device of the measuring device with respect to the measurement object such that the object-side focal point of the emitted and received radiation is arranged in a defined position with respect to the measurement object. The defined position with respect to the measurement object is preferably understood to mean that the object-side focal point of the emitted and received radiation is aligned with a measurement point which is located at, in or on the measurement object, in particular that the object-side focal point of the measuring device is located on a measurement surface of the measurement object or in a specific layer of the measurement object. This depends on the measurement task. For example, in the case of a coating thickness measurement, the object-side focal point on the measurement surface of the object to be measured or on the base body of the object to be measured, at least one coating, in particular a lacquer coating, being applied, can be understood to be the defined position with respect to the object to be measured.

[0025] The external nominal operating point of the handling device which is assigned to the connection point is formed by a coordinate system of the handling device, whereby the external nominal operating point is preferably a so-called tool center point (TCP). The handling device can have its own tool coordinate system, wherein the TCP is used as a basis for simple control. This can enable a short cycle time for the positioning of the measuring device and the measurement object with respect to one another and for the scanning of the relative movement of the measuring device and the measurement object in order to perform measurements at a plurality of measurement points.

[0026] The object underlying the present invention is also achieved by a method for positioning emission and reception radiation of a terahertz device relative to a measurement object for measuring the measurement object, wherein a measuring device according to one of the above-described embodiments is aligned relative to the measurement object by a manipulator, and the object-side focal points of the emission and reception radiation are positioned relative to the measurement object, and wherein the setting of a preferred orthogonal angle of the emission and reception radiation relative to the measurement object (in particular relative to an object plane or measurement surface of the measurement object) is controlled by at least one angle adjustment element on at least one reflective element of the emission and reception radiation of the terahertz device. The method enables the measuring device to be moved relative to the measurement object to an observation position in order to subsequently perform a distance and / or angle measurement of the emission and reception radiation of the terahertz device or of a separate, preferably optical, sensor to the measurement object, and the relative positioning of the measuring device relative to the measurement object is controlled or regulated by the at least one angle adjustment element of at least one reflective element of the emission and reception radiation until predetermined tolerances are achieved with respect to the distance and angle between the measuring device and the object-side focal points of the emission and reception radiation.

[0027] The relative positioning of the measuring device relative to the measured object is advantageously controlled by an external controller, in particular a controller of the manipulator, so that the object-side focal points of the emitted and received radiation coincide with an external nominal operating point of the manipulator, or the object-side focal points of the emitted and received radiation and the external nominal operating point of the manipulator are brought into alignment by the controller by aligning these points with one another. This effectively results in a rotational movement of the measuring device, in particular of the at least one reflective element, about the nominal operating point, thereby enabling an angular correction to be achieved in a simple manner without requiring a change in distance.

[0028] To position the measuring device relative to the measured object, according to a preferred embodiment of the method, the distance between the measuring device and the measured object can first be detected. If the detected distance exceeds a predetermined value, repositioning is performed. Alternatively, if the detected distance falls below a predetermined value, a reference spectrum of the measured object stored in the control unit is compared with the actually detected distance. Subsequently, after a defined or predetermined distance has been covered, a change in the angle of at least one reflective element and / or the measuring device relative to the measured object is triggered until a predetermined angle relative to the measured object is covered. The predetermined distance of the object-side focal points of the emitted and received radiation relative to the measured object and the predetermined angular position of the measuring device relative to the measured object correspond to a target position of the terahertz device relative to the measured object. In this target position, the emitted and received beams of the terahertz device are preferably aligned orthogonally to the measured object, in particular, to the object plane of the measured object. This results in improved measurement quality, wherein a power drop of preferably less than 10% at 4 THz is not exceeded.

[0029] Alternatively, it can be provided that the relative positioning of the measuring device with respect to the measurement object is first performed by detecting the angle of the reflective element with respect to the measurement object, and then, after the reflective element has reached a defined angle, a defined distance between the measuring device and the measurement object of the object-side focal points of the emitted radiation and the received radiation is approached or controlled.

[0030] It can also be provided that the distances of the object-side focal points of the emitting radiation and the receiving radiation relative to the object to be measured and the angle of at least one reflective element of the measuring device relative to the object to be measured are continuously controlled simultaneously or alternately during the movement of the manipulator and / or the object to be measured.

[0031] In the above-described embodiment, the at least one angle adjustment element of the at least one reflective element to be set can be used to additionally or simultaneously adjust the angle of the emitted radiation and the received radiation relative to the measurement object, preferably to adjust the emitted radiation and the received radiation to be orthogonally aligned with the measurement object. When the relative distance and / or relative angle are set, the distance and / or angle between the measuring device and the measurement object are known, thereby allowing the measuring device to be moved relative to the measurement object, the measurement object to be moved relative to the measuring device, or both the measurement object and the measuring device to be moved relative to each other and / or their positions to be changed simultaneously.

[0032] The changes in distance and / or angle used to position the measuring device relative to the measurement object can be detected, for example, by at least one independent, preferably optical, sensor. Alternatively, the changes in distance and / or angle can be detected based on a terahertz measurement signal of terahertz radiation. Combinations are also possible. To optimize the relative positioning of the measuring device relative to the measurement object, the changes in the angular position of at least one reflective element can be controlled by a control system during the distance and / or angle measurement of the reflective element. This makes it possible to optimize the relative positioning of the measuring device relative to the measurement object, or the relative positioning of the emitted and received radiation of the terahertz device relative to the measurement object.

[0033] A preferred embodiment of the method is based on the following consecutive steps:

[0034] By controlling a manipulator toward a target position of the measurement object stored in the control system, the object-side focal points of the transmitted and received radiation are positioned relative to the measurement object. At least one distance measurement and / or angle measurement is then performed to determine the actual relative position of the measurement device relative to the measurement object. If the approached distance and / or angle exceeds a tolerance range, repositioning is performed to correct the distance and / or angle. A stored reference spectrum of the measurement object is then compared in the control system with the actual measured distance between the object-side focal points of the transmitted and received beams and the measurement object, particularly after reaching the end position of the distance between the measurement object and the measurement device. Alternatively, when the distance falls below a defined distance, a comparison is performed with a stored reference spectrum of the measurement object. Subsequently, at least two measurements are performed using terahertz radiation with at least one reflective element in different angular positions. Consequently, at least one correction value for controlling the at least one reflective element is controlled, and the at least one reflective element is moved toward the target position based on the correction value, wherein the transmitted and received radiation are preferably aligned orthogonally to the measurement object in the target position. Measurements using the terahertz device can then be initiated. Preferably, a coating thickness measurement is performed, for example of a paint layer on a vehicle body.

[0035] During the positioning of the measuring device relative to the object to be measured, a distance measurement can be performed using at least one independent, preferably optical, sensor and / or terahertz radiation from a terahertz device. The measuring device can be brought into a controlled proximity, thereby controlling the change in the angular position of at least one reflective element, particularly during the distance measurement relative to the object-side focal point. The independent optical sensor is preferably used to perform multi-point triangulation for distance and / or angle correction. Structured or scanned irradiation in the visible or near-infrared range is preferably used for this purpose. Once a distance between the measurement object and the measuring device is reached at which the terahertz pulse is detected by the terahertz radiation from the measurement object, further distance and / or angle corrections can be optimized based on the terahertz signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] The invention and other advantageous and further embodiments will be described and explained in more detail below with reference to the examples shown in the accompanying drawings. The features that can be derived from the description and the drawings may be used individually or in any combination according to the invention. The drawings show:

[0037] Figure 1 is a perspective view of a positioning apparatus wherein a measuring device is aligned with a measurement object;

[0038] Figure 2 It is a schematic diagram of the structure of the measuring device;

[0039] Figure 3 is relative to Figure 2 A schematic diagram of an optional setup of a measuring device; and

[0040] Figure 4 is a schematic sequence of steps for positioning a measuring device and an object to be measured relative to each other. Specific embodiments

[0041] Figure 1A schematic diagram is shown in which the measuring device 11 is in a measuring position to perform a measurement on a measurement object 12. The positioning apparatus 50 comprises at least one handling device 14, for example a multi-axis robot. Furthermore, a controller 25 is provided, which can be part of the positioning apparatus 50. The control unit 25 can be designed to control the handling device 14 and / or the measuring device 11 and / or to perform a measurement with the measuring device 11. The measuring device 11 is arranged on the handling device 14. The handling device 14 can be used to position the measuring device 11 relative to the measurement object 12. In individual applications, it can be provided that the measuring device 11 is fixedly positioned and the measurement object 12 is moved relative to the measuring device 11. Applications in which the measuring device 11 and the measurement object 12 are positioned relative to one another are also possible, i.e. the measuring device 11 and the measurement object 12 change the distance and / or the angle to one another simultaneously or alternately.

[0042] The measuring device 11 comprises a terahertz device 16, which has an emitter 17 for emitting an emission radiation 18 and a receiver 19 for receiving a reception radiation 20. Preferably, a transceiver 35 is provided, whereby the emission radiation 18 and the reception radiation 20 are coaxial with one another.

[0043] The measuring device 11 is arranged on the handling device 14 via a connection point 13. In particular, the handling device 14 comprises an external nominal operating point 22, also referred to as tool center point (TCP), which starts from the connection point 13. This means that the handling device 14 has an imaginary working point in its coordinate system, which can be controlled by the controller 25 to move the connection point 13 and thus the measuring device 11 in space.

[0044] Figure 2A schematic diagram shows the arrangement of an exemplary embodiment of a measuring device 11. Starting from a terahertz device 16, in particular a transceiver, terahertz radiation is deflected at a coupling element 23 and directed onto a reflective element 24. The coupling element 23 and the reflective element 24 have a common beam axis 48. An optical element 26 may be arranged between the coupling element 23 and the reflective element 24 in order to direct the terahertz radiation onto the reflective element 24, preferably in a focused manner. The terahertz radiation is deflected at the reflective element 24 and fed to an optical device 28, whereupon the terahertz radiation is focused by the optical device 28 onto a focal point 30. The focal point 30 is a so-called object-side focal point, which lies in an object plane 38. In the measuring position of the measuring device 11 relative to the measured object 12, the object-side focal point 30 is preferably located on or in the measured object 12 or in the object plane 38 of the measured object 12. The measuring device 11 may further comprise a detection device 32 , by means of which the measured object 12 or an object-side focus 30 of the emitted radiation 18 and the received radiation 20 may be detected on the measured object 12 .

[0045] Furthermore, a separate, preferably optical, sensor 34 can be provided on or within the housing 15 of the measuring device 11. This sensor 34 operates using radiation in the visible or near-infrared range. This sensor 34 can be used to detect the distance between the measuring device 11 and the object 12 being measured. Advantageously, this sensor 34 can be aligned with the emitted radiation 18 and the received radiation 20 of the terahertz device 16, such that the radiation of the optical sensor 34 is coaxially aligned with the emitted radiation 18 and the received radiation 20 of the terahertz device 16.

[0046] In accordance with Figure 2 In the embodiment, the optical device 28 includes a first optical element 36 and a second optical element 37. The optical device 28 is preferably designed as an imaging optical device 28. For example, the first optical element 36 and the second optical element 37 can be designed as parabolic mirrors. Advantageously, the focal lengths of the optical elements 36 and 37 differ from each other, in particular, the focal length f1 of the optical element 36 is smaller than the focal length f2 of the optical element 37. The greater focal length of the second optical element 37 compared to the first optical element 36 enables a greater depth of field and thus reduces distance sensitivity. At least the second optical element 37 is movable along the optical axis 42 to adjust the focal position.

[0047] On the optical axis 42 of the optical device 28, both the object-side focus 30 and the conjugate focus 44 lie within the image plane. When the measuring device 11 is aligned with the optical axis 42 perpendicular to the measurement surface, the main beams 51 of the transmitted radiation 18 and the received radiation 20 lie on the optical axis 42. The rotation axis 46 of the reflective element 24 is preferably located at the conjugate focus 44. The rotation axis 46 can form the rotation center 45 of the reflective element 24, so that the transmitted and received radiation rotate about the object-side focus 30. Therefore, if the measurement object 12 is not positioned orthogonally, or if the object plane 39 is tilted relative to the measuring device 11, angular variations of the reflective element 24 allow the angular position to change, thereby causing the rotation center 21 of the transmitted and received radiation to correspond to the object-side focus 30 of the transmitted and received radiation. Consequently, angular variations of the reflective element 24 at the rotation center 21 of the transmitted and received radiation do not result in a distance-varying effect. By changing the angular position of the reflective element 24, the tilted object plane 39 can be corrected in the object plane 38 so that a target position is reached in which the terahertz radiation is arranged perpendicular to the surface of the measurement object 12, in particular perpendicular to the tilted surface of the measurement object 12. This makes it easier to detect and correct the angular position or tilt between the measurement object 12 and the measuring device 11.

[0048] At least one angle adjustment element 24a, 24b is provided for adjusting and changing the angular position of the reflective element 24. The angle adjustment element 24a can rotatably control the reflective element 24, for example, about a rotation axis 46, preferably about a first spatial direction.

[0049] The angle adjustment element 24b can, for example, rotate the reflective element 24 about another rotation axis 47, preferably about another spatial direction or a second spatial direction. The further rotation axis 47 is preferably arranged perpendicular to the rotation axis 46, such as the X-axis. The further rotation axis 47 can also form a rotation center 45 of the reflective element 24. The rotation axis 46 and the rotation axis 47 preferably intersect on the optical axis 48, so that the rotation center 45 is preferably located at the intersection of the axes.

[0050] For example, the optical axis 48 is located according to Figure 2 The reflective element 24 can be adjusted in at least one spatial direction, preferably in two spatial directions, preferably by means of at least one angle adjustment element 24a, 24b.

[0051] Figure 3 Shows relative to Figure 2An alternative embodiment of the measuring device 11 is provided. In this embodiment, it is arranged that the optical device 28 comprises only one optical element 36. The reflective element 24 is associated with one optical element 36. The reflective element 24 corresponds to Figure 2 The reflective element 24 is shown.

[0052] In the direction of the beam axis 48, which is preferably located along the Z axis, an additional reflective element 54 is positioned at a distance from the reflective element 24. This additional reflective element 54 is preferably variable in at least one spatial direction, preferably in two spatial directions, via at least one angle adjustment element 24a, 24b. At least one axis of rotation 46, 47, preferably both axes of rotation, of the additional reflective element 54 are parallel to the axes of rotation 46, 47 of the reflective element 24. The additional reflective element 54 can correspond to one of the embodiments of the reflective element 24. In the normal position of the reflective elements 24, 54 (solid line), the main beam (central beam) 51 of the emitted radiation 18 and the received radiation 20 lies on the optical axis 42. Furthermore, only the relevant marginal beams 52 are shown in solid lines. The measurement surface 38 is arranged perpendicular to the optical axis 42 or the main beam 51.

[0053] If the measurement surface is tilted relative to the measurement device 11, the object plane 39 will also be tilted. To compensate for this, the reflective elements 24, 54 are controlled so that the optical axes 42 of the transmitted and received light beams 18, 20 are arranged perpendicular to the tilted surface 39. For example, the main light beam (central light beam) 51 ′ is shown in dashed lines in relation to the alignment elements 24, 54 (also dashed lines).

[0054] The reflective element 24 and / or the at least one angle adjustment element 24a, 24b of the further reflective element 54 may be identical in terms of design and / or actuation of the reflective element 24 and the further reflective element 54.

[0055] Furthermore, only one angle control element 24 a is capable of controlling the angular position of the reflective element 24 , whereas the further angle control element 24 b is capable of controlling the angular position of the further reflective element 54 .

[0056] This arrangement enables the Figure 2 The object-side focus 30 of the emitted radiation 18 and received radiation 20 coincides with the center of rotation 21 of the emitted radiation 18 and received radiation 20 .

[0057] Preferably, the connection point 19 or the external nominal operating point 22 of the manipulator 14 corresponds to the object-side focus 30 of the measuring device 11, or the object-side focus 30 of the measuring device 11 is aligned with the nominal operating point 22 or can be adjusted to the nominal operating point 22, so that the measuring device 11 can be simply positioned relative to the measured object 12 by the manipulator 14.

[0058] The following Figure 4 A preferred procedure for positioning the measuring device 11 relative to the measurement object 12 is shown.

[0059] According to step 61, the measuring device 11 is moved by the manipulator 14 in a direction toward a measuring point on the measurement object 12, i.e., toward a target position (nominal position). This measuring point of the measurement object 12 has been previously determined or taught in the control system of the manipulator 14. During the approach of the measuring device 11 to the measurement object 12, in order to relatively position the measuring device 11 with respect to the measurement object 12, the distance between the measuring device 11 and the measurement object 12 can preferably be first detected, and then, after the defined distance is covered, the emission radiation 18 and the reception radiation 20 of the terahertz device 16 with respect to the measurement object 12 are controlled to a defined angle. Alternatively, in order to relatively position the emission radiation 18 and the reception radiation 20 of the terahertz device 16 with respect to the measurement object 12, the angle is first detected, and after the defined angle has been reached, the defined distance between the measuring device 11 and the measurement object 12 is then controlled. Alternatively, the relative distance of the measuring device 11 relative to the measurement object 12 and the angles of the emitted radiation 18 and the received radiation 20 of the terahertz device 16 relative to the measurement object 12 can be controlled continuously, simultaneously or alternately, during the lateral movement of the manipulator 14 and / or the measurement object 12. After reaching a predetermined distance, which can be detected by a separate, preferably optical sensor 34 or determined by the controller 25 of the manipulator 14, the lateral movement speed is reduced according to step 62 so that the measuring device 11 is brought closer to the measurement position relative to the measurement object 12. During this approach, the change in distance and / or angle can be determined by the separate, preferably optical sensor 34 and / or by the determined properties of the emitted radiation 18 and the received radiation 20 of the terahertz device 16, whereby a 1D or 2D scan of the surface of the measurement object (12) can be performed by the terahertz device 16.

[0060] In step 63, at least one distance measurement and / or angle measurement may be performed to determine the actual relative position of the measuring device 11 with respect to the measurement object 12, wherein: a) if the detected distance exceeds a limit value, repositioning is performed; or b) if the detected distance is below the limit value, a reference spectrum of the measurement object 12 stored in the control system is compared with the actual detected distance from the measuring device 11 to the measurement object 12. Preferably, software calibration is performed, i.e., it is not necessary to move the measurement device 11.

[0061] In a subsequent step 64, an angle measurement is performed to determine the orientation of the emitted radiation 18 and the received radiation 20 of the terahertz device 16 relative to the measurement object 12. Based on this angle measurement, correction values ​​are determined to align the emitted radiation 18 and the received radiation 20 with the at least one reflective element 24, 54 with respect to its angular position relative to the measurement object 12, preferably an orthogonal position relative to the measurement object. Control of the at least one optical reflective element 24, 54 may be sufficient to perform the angle correction. By controlling two different angular positions of the reflective element 24, 54, the correction values ​​for the alignment of the reflective element 24, 54 can be controlled so that an inclined arrangement of the measurement object 12 or an inclined surface of the measurement object 12 relative to the geometric axis 42 of the optical device 28 is compensated.

[0062] The terahertz signal is evaluated to determine the angle correction. Additionally and / or alternatively, an angle measurement can also be performed by means of the at least one optical sensor 34 .

[0063] After the controlled angular position of the at least one reflective element 24 has been reached, a measurement of the measurement object 12 , such as a coating thickness measurement, can be performed according to step 65 by the terahertz device 16 .

Claims

1. A measuring device comprising: a terahertz device (16) for emitting and receiving terahertz radiation to perform measurements on a measurement object (12), in particular coating thickness measurements; The terahertz device (16) comprises a transmitter (17) for transmitting transmission radiation (18) onto the measurement object (12) and a receiver (19) for detecting reception radiation (20), both the transmitter (17) and the receiver (19) having a focal point (30) on the object side. Its characteristics are: The transmitted radiation (18) and the received radiation (20) are coaxial with each other; At least one reflective element (24, 54) having at least one angle adjustment element (24a, 24b) is arranged in the transmitted radiation (18) and the received radiation (20), wherein the at least one angle adjustment element (24a, 24b) can be controlled by a controller (25) to change the angular position of at least one reflective element (24, 54) about at least one rotation axis (46, 47) in at least one spatial direction, and the rotation center (45) is located on the at least one rotation axis (46, 47); At least one optical device (28) is arranged between at least one of the reflective elements (24, 54) and the object-side focus (30) of the emitted radiation (18) and the received radiation (20); and The object-side focus (30) of the transmitted radiation (18) and the received radiation (20) formed by the optical device (28) coincides with the rotation center (21) of the transmitted radiation (18) and the received radiation (20), and the rotation center (21) of the transmitted radiation (18) and the received radiation (20) can be controlled by the at least one angle adjustment element (24a, 24b).

2. The measuring device according to claim 1, characterized in that The rotation center (45) of one of the reflective elements (24) is located at a conjugate focus (44) relative to an object plane (38) of the optical device (28), the object-side focus (30) is located in the object plane (38) of the optical device (28), the rotation center (45) of one of the reflective elements (24) is assigned to the object (12) to be measured, and the rotation center (45) of one of the reflective elements (24) is preferably designed as at least one rotation axis (46, 47) of one of the reflective elements (24).

3. The measuring device according to claim 2, characterized in that A conjugate image-side focal point (44) of the transmitted radiation (18) and the received radiation (20) is located on at least one of the reflective elements (24).

4. The measuring device according to any one of the preceding claims, characterized in that The optical device (28) comprises at least one optical element (36, 37), in particular a spherical lens, a parabolic mirror or an aspherical lens.

5. The measuring device according to any one of the preceding claims, characterized in that Two mutually aligned reflective elements (24, 54) are arranged between the terahertz device (16) and the optical device (28), which comprises only one optical element (36).

6. The measuring device according to claim 5, characterized in that At least one of the reflective elements (24, 54) can be adjusted in at least one spatial direction, preferably in at least two spatial directions, by means of the at least one angle adjustment element (24a, 24b).

7. The measuring device according to any one of claims 1 to 4, characterized in that The optical device (28) comprises two optical elements (36, 37), which are aligned with respect to an optical axis (42) of the optical device (28) and are arranged between at least one reflective element (24) assigned to the object (12) to be measured and the object-side focus (30), and preferably at least one of the optical elements (36, 37) is movable along the optical axis (42) to adjust the position of the focus.

8. The measuring device according to claim 7, characterized in that The optical device (28) having the two optical elements (36, 37) comprises: a first optical element (36) having a focal length f1 associated with one of the reflective elements (24); and a second optical element (37) having a focal length f2 associated with the object-side focal point (30), Wherein, the focal length f2>the focal length f1.

9. The measuring device according to any one of claims 1 to 8, characterized in that The optical device (28) is designed for high distance tolerances and in particular has a long focal length optical device, the Rayleigh length of the emitted radiation and the received radiation of which is in particular greater than 6 mm, preferably greater than 10 mm at a frequency of 1 THz, and the distance tolerance is advantageously increased by additional correction on the software side.

10. The measuring device according to any one of the preceding claims, characterized in that By means of the terahertz radiation, a distance and / or angle measurement between the measuring device (11) and the measurement object (12) is provided by detecting terahertz pulses, wherein, preferably during the distance and / or angle measurement, a change in the angular position of at least one of the reflective elements (24, 54) can be controlled by at least one angle adjustment element (24a, 24b).

11. The measuring device according to any one of the preceding claims, characterized in that At least one independent sensor (34) for distance and / or angle measurement and / or topology measurement between the measuring device (11) and the measured object (12) is arranged on or in the measuring device (11).

12. The measuring device according to claim 11, characterized in that The at least one independent sensor (34) is an optical sensor, and preferably the at least one independent sensor (34) operates with radiation in the visible range or the near infrared range.

13. The measuring device according to claim 11 or 12, characterized in that The at least one independent sensor (34) is coaxially aligned with the emitted radiation (18) and the received radiation (20) of the terahertz device (16), and in particular the at least one independent sensor (34) is coaxially superposed with the emitted radiation (18) and the received radiation (20) of the terahertz device (16) between the emitter (17) and the receiver (19) of the terahertz device (16) and at least one of the reflective elements (24, 54).

14. The measuring device according to claim 13, characterized in that An optical coupling element (23) is provided for the coaxial superposition of the emission radiation (18) and / or the reception radiation (20) of the at least one independent sensor (34) and the emission radiation (18) and / or the reception radiation (20) of the terahertz device (16), and is designed as a reflective element for the emission radiation (18) and / or the reception radiation (20) of the terahertz device (16).

15. A positioning device for relative positioning of a measuring device (11) relative to a measurement object (12) for performing measurements on the measurement object (12), the measuring device (11) having a terahertz device (16) for emitting and / or receiving terahertz radiation, The positioning device has an actuating device (14) having a connecting joint (13), wherein: An external nominal operating point (TCP) is assigned to the connection joint (13), Its characteristics are: The measuring device (11) according to any one of claims 1 to 14 is arranged at the connecting joint (13) of the operating device (14); the object-side focal points (30) of the emission radiation (18) and the reception radiation (20) of the measuring device (11) and at least one of the rotation centers (21; 45) of the emission radiation (18) and the reception radiation (20) coincide with each other; and The measuring device (11) can be positioned relative to the measurement object (12) by means of the manipulator device (14) such that the object-side focus (30) of the emission radiation (18) and the reception radiation (20) is aligned in a defined position relative to the measurement object (12).

16. The positioning device according to claim 15, characterized in that At least one of the rotation centers (21; 45) of the emitted radiation (18) and the received radiation (20) coincides with the outer nominal operating point (TCP) of the manipulator (14).

17. A method for positioning an emission radiation (18) and a reception radiation (20) of a terahertz device (16) relative to a measurement object (12) for performing a measurement on the measurement object (12), Its characteristics are: The measuring device (11) according to claim 1 is aligned relative to the measurement object (12) by means of a manipulator (14), wherein the object-side focus (30) of the transmitted radiation (18) and of the received radiation (20) is positioned relative to the measurement object (12), the object-side focus (30) of the transmitted radiation (18) and of the received radiation (20) preferably being located on the surface of the measurement object (12); and The at least one angle adjustment element (24a, 24b) on at least one of the reflective elements (24, 54) in the optical path of the emission radiation (18) and the reception radiation (20) of the terahertz device (16) is used to control the angular setting of the emission radiation (18) and the reception radiation (20) relative to the measurement object (12).

18. The method according to claim 17, characterized in that The relative positioning of the measuring device (11) with respect to the measurement object (12) is controlled by an external controller (25), which in particular controls the manipulator (14), and the object-side focus (30) of the transmitted radiation (18) and the received radiation (20) coincides with an external nominal operating point (TCP) of the manipulator (14).

19. The method according to claim 17 or 18, characterized in that: In order to position the measuring device (11) relative to the measurement object (12), the distance between the measuring device (11) and the measurement object (12) is first detected, and then, after a defined distance has been reached, the emission radiation (18) and the reception radiation (20) of the terahertz device (16) are controlled at defined angles relative to the measurement object (12); or For relative positioning of the emitted radiation (18) and the received radiation (20) of the terahertz device (16) with respect to the measurement object (12), an angle is first detected and, after a defined angle has been reached, a defined distance between the measurement device (11) and the measurement object (12) is subsequently controlled; or The relative distance of the measuring device (11) relative to the object (12) to be measured and the angles of the emitted radiation (18) and the received radiation (20) of the terahertz device (16) relative to the object (12) to be measured are controlled simultaneously or alternately and continuously during the lateral movement of the manipulator (14) and / or the object (12) to be measured, and In this case, additionally or simultaneously, the relative angles of the transmitted radiation (18) and the received radiation (20) relative to the measurement object (12) are set by means of the at least one angle adjustment element (24a, 24b) of at least one of the reflective elements (24, 54), preferably in a manner orthogonal to the measurement object (12).

20. The method according to any one of claims 17 to 19, characterized in that A change in the distance and / or angle for positioning the emitted radiation (18) and the received radiation (20) of the measuring device (11) and / or the terahertz device (16) relative to the object (12) to be measured is detected by at least one independent sensor (34) and / or a terahertz measurement signal based on the terahertz radiation, and preferably during the distance and / or angle measurement, the at least one angle adjustment element (24a, 24b) is actuated to change the angular position of at least one of the reflective elements (24, 54).

21. The method according to any one of claims 17 to 20, characterized in that The method comprises the following steps: relative positioning of the object-side focal points (30) of the transmitted radiation (18) and the received radiation (20) with respect to the object (12) by controlling the manipulator (14) toward a target position of the object (12) stored in the controller (25); At least one distance measurement and / or angle measurement is performed to determine the actual relative position of the measuring device (11) relative to the object (12) to be measured, wherein: a) if the detected distance exceeds a defined value, repositioning is performed; or b) if the detected distance is lower than the defined value, comparing a reference spectrum of the measurement object (12) stored in the control system with the actually detected distance from the measurement device (11) to the measurement object (12); and performing at least two measurements at mutually different angular positions of at least one of the reflective elements (24, 54), preferably by means of terahertz radiation, and determining correction values ​​for the actuation of the at least one angle adjustment element (24a, 24b), and moving the at least one angle adjustment element (24a, 24b) based on the correction values ​​to the desired position, at which the emission radiation (18) and the reception radiation (20) of the terahertz device (16) are preferably orthogonally aligned with the measurement object (12); and Measurements are performed with the aid of the terahertz device (16), which is used to emit and receive terahertz radiation for performing measurements, in particular coating thickness measurements.

22. The method according to claim 21, characterized in that At least one distance measurement and / or angle measurement is performed by means of the at least one independent, preferably optical, sensor (34) and / or the emitted radiation (18) and the received radiation (20) of the terahertz device (16) during the positioning of the measuring device (11) relative to the measurement object (12), and the measuring device (11) is approached in a controlled manner in order to reach the desired position, wherein the angular position of at least one of the reflective elements (24, 54) and / or the change in the distance are preferably controlled during the positioning of the measuring device (11) relative to the object (12) to be measured, and correction values ​​for the control of the at least one angle adjustment element (24a, 24b) are determined and the at least one angle adjustment element (24a, 24b) is controlled by means of the correction values ​​to the desired position in which the emitted radiation (18) and the received radiation (20) of the terahertz device (16) are preferably aligned orthogonally to the object (12) to be measured.

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