Measuring device and positioning device and method for relative positioning of the measuring device with a thz device

Abstract

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

Description

[0001] Measuring device and positioning device and method for relative positioning of the measuring device with a THz device

[0002] The invention relates to a measuring device with a THz device for transmitting and receiving THz radiation to carry out a measurement on an object.

[0003] Furthermore, the invention relates to a positioning device and a method for the relative positioning of the measuring device with a THz device for carrying out the measurement on a measurement object.

[0004] DE 10 2018 126 652 A1 discloses a method and a system for aligning a THz sensor to a target surface of an object. This target surface can be, for example, a paint layer of a vehicle in order to detect, for example, the thickness of one or more paint layers on a vehicle body using a sensor measuring head of a THz sensor system. The THz sensor is positioned relative to the target surface using a handling device. To align the sensor measuring head to the target surface, an estimated normal of the sensor measuring head with respect to the target surface is first determined. Subsequently, the selected area of ​​the target surface is scanned with a beam of rays to identify an optimal normal based on a maximum peak amplitude.The sensor measuring head is then aligned relative to the target surface of the object based on the optimal normal after its determination in order to perform the measurement on the object.

[0005] US 2008 / 0251720 A1 discloses an image capture device in which THz radiation is directed onto a deflection mirror to direct the radiation onto a measurement object. The deflection mirror is rotated about an axis, enabling a lateral scan of the surface of the measurement object. An analogous device is known from US 2021 / 0389238 A1. US 2018 / 03476963 A1 discloses a method for measuring layer thicknesses using a THz device for transmitting and receiving THz radiation. It is provided that a traversing movement is controlled for the layer thickness measurement to achieve different optical axes between the THz device and the measurement object.

[0006] DE 10 2013 223 945 A1 discloses a measuring device for measuring a test object, in particular for the complete measurement of test objects designed as plastic pipes with circular cross-sections. For this purpose, the measuring device comprises a transmitter-receiver unit and a mirror arrangement with a first mirror and a second mirror. The radiation reflected by the test object is evaluated by a control unit.

[0007] From WO 2020 / 239694 A1 a method for carrying out a layer thickness measurement with a THz device for transmitting and receiving THz radiation is known, wherein the measuring device comprises a sensor for distance measurement and another sensor for angle measurement and the recorded parameters of the two sensors are taken into account in the evaluation of the received radiation.

[0008] US 2015 / 0212060 A1 discloses a detection system for characterizing a coating, such as a paint layer, using THz radiation. A handling device is provided with a THz device for transmitting and receiving THz radiation. To measure the coating thickness, the THz device is aligned with the surface of the measuring object by the handling device and moved along the measuring surface.

[0009] WO 2022 / 135763 A1 discloses a method for detecting layers on a measurement object. This method comprises a THz device for transmitting and receiving THz radiation to perform a measurement, in particular a layer thickness measurement, on a measurement object. The detected received radiation is compared with stored reference data to enable rapid evaluation and output of the detected received radiation.

[0010] The invention is based on the object of proposing a measuring device as well as a positioning device and a method for the relative positioning of the measuring device with a THz device for transmitting and receiving THz radiation for carrying out a measurement on a measurement object, whereby a cycle time for positioning the THz device with respect to a measurement object for carrying out a measurement is reduced.

[0011] This object is achieved by a measuring device with a THz device for transmitting and receiving THz radiation for carrying out a measurement, in particular layer thickness measurement on a measurement object, in which the transmitting and receiving radiation are coaxially aligned with one another, in which at least one reflective element with at least one angle adjustment element is provided in the transmitting and receiving radiation, wherein the at least one angle element, which can be controlled by a controller for a change in an angular position of the at least one reflected element in at least one spatial direction and in which the object-side focal point of the transmitting and receiving radiation and at least one center of rotation, preferably all centers of rotation, of the transmitting and receiving radiation coincide.This design of the measuring device enables rapid alignment of the transmit and receive radiation of the THz device to correct an angular tolerance, particularly after positioning the measuring device at a distance from the measurement object. Furthermore, the alignment of the at least one center of rotation of the transmit and receive radiation with the object-side focal point of the transmit and receive radiation enables a distance-independent correction in the event of a change in the angular position of the at least one reflective element. This reduces the cycle time for positioning and precisely aligning the THz device to the measurement object, allowing for precise measurements on the measurement object.

[0012] Furthermore, it is preferably provided that at least one optical device is provided between the one reflective element and the object-side focal point of the transmitted and received radiation, and the center of rotation of the reflective element lies at a conjugate focal point with respect to an object plane of the optical device in which the object-side focal point lies. An imaging optical device is preferably provided in the optical device in order to align the transmitted and received radiation with the center of rotation. To correct an angular position in the case of a tilted object plane of the measurement object, the center of rotation of the at least one reflective element is preferably designed as a rotation axis of the reflective element. By controlling a rotational movement about the at least one rotation axis, a correction of possible angular tolerances is thus possible in a simple and rapid manner.In this case, relative angular movements of the transmitting and receiving radiation to the measuring object are carried out in such a way that a center of rotation of the transmitting and receiving radiation lies in the object-side focal point.

[0013] Due to the optical arrangement of the transmit and receive radiation, the object-side focal point is preferably located on an object plane of the measurement object, and the conjugate image-side focal point of the transmit and receive radiation is located on the at least one reflective element. This enables rapid correction of detected angular deviations as well as improved evaluation of the receive radiation for angle correction.

[0014] The optical device can comprise at least one optical element, such as a spherical lens, a parabolic mirror, or an aspheric lens. This enables a structurally simple design. Between the THz device and the optical device, which according to a first embodiment comprises only one optical element, two mutually aligned reflective elements are preferably provided, wherein at least one of the two reflective elements, which is assigned to the optical element, is adjustable in at least one, preferably two, spatial directions. For example, the at least one reflective element is designed as a tilting mirror with one or two axes of rotation for changing the angular position. In such an embodiment, a parabolic mirror is preferably provided as the optical element in the collimated beam path.

[0015] Alternatively, the optical device can comprise two mutually aligned optical elements along its optical axis, which are arranged between the one reflective element and the object-side focal point. This arrangement can enable the measuring device to exhibit a low distance dependence with regard to its positioning relative to the measurement object.

[0016] Furthermore, it is preferably provided that the optical device with two optical elements comprises a first optical element assigned to the one reflective element and having a focal length fi, and a second optical element assigned to the object-side focal point and having a focal length f2, wherein the focal length f2 > fi. This arrangement enables a larger or longer focus to be achieved in the direction of the object-side focal point, thereby reducing the distance sensitivity of the converged radiation.

[0017] Advantageously, the optical device is designed for a high distance tolerance and, in particular, comprises a long focal length optic with a Rayleigh length of the transmitted and received radiation, which is preferably greater than 6 mm and, in particular, greater than 10 mm at a frequency of 1 THz. Advantageously, the distance tolerance can be increased by additional software correction. According to a further preferred embodiment, a distance and / or angle measurement between the measuring device and the measurement object is provided using the THz radiation by detecting THz pulses. For example, when the measuring device approaches the measurement object, the transmitted and received radiation of the THz device can be used for distance measurement. An angle measurement can be carried out superimposed or simultaneously, thereby enabling a reduction in the time required for precise alignment of the measuring device to the measurement object.Advantageously, a change in the angular position of the at least one reflective element of the optical device can be controlled during the distance and / or angle measurement, thereby enabling a rapid correction in the event of distance and / or angle tolerances outside the tolerance range.

[0018] Preferably, at least one separate sensor for measuring the distance and / or angle between the measuring device and the measurement object is provided on or in the measuring device. This separate sensor can be used in particular during a first approach of the measuring device to the measurement object.

[0019] Advantageously, the sensor is designed as an optical sensor. Advantageously, the at least one separate optical sensor can operate with radiation in the visible range or near infrared range. This also enables the measurement surface of the measurement object to be detected and monitored. Advantageously, this enables distance and / or angle measurements to be recorded by the optical sensor at an even greater distance between the measuring device and the measurement object, and subsequently the distance and / or angle measurement can be carried out via a precise measurement using THz radiation in a smaller measuring range. This superposition of the two distance and / or angle measurements can enable further cycle time optimization. Advantageously, it is provided that the transmit and / or receive radiation of the at least one separate sensor is aligned coaxially with the transmit and receive radiation of the THz device.In particular, the separate optical sensor between the THz device and the at least one reflective element can be superimposed with the THz radiation of the THz device. This also enables simultaneous scanning of the surface of the measurement object.

[0020] Advantageously, an optical coupling element is provided for coaxially superimposing the transmit and / or receive radiation of the separate sensor with the transmit and receive radiation of the THz device. This coupling element is designed as a reflection element for the transmit and receive radiation of the THz device. This coupling element can also be the first reflective element. This enables a compact arrangement. Such a coupling element can, for example, be designed as a glass element with an indium tin oxide coating. Alternatively, a membrane with such a dual function can also be used.

[0021] The object underlying the invention is further achieved by a positioning device for the relative positioning of a measuring device with a THz device for transmitting and / or receiving THz radiation relative to a measurement object for carrying out a measurement on the measurement object, which positioning device has a handling device with a connection interface, wherein the connection interface is assigned to an external nominal operating point, wherein a measuring device according to one of the previously described embodiments is provided at the connection interface of the handling device and the object-side focal point of the transmitting and receiving radiation and at least one center of rotation of the transmitting and receiving radiation of the THz device, preferably all centers of rotation,and advantageously corresponds to the external nominal operating point of the handling device and can be positioned by the handling device of the measuring device relative to the measuring object, so that the object-side focal point of the transmitting and receiving radiation is aligned in a defined position relative to the measuring object. The defined position relative to the measuring object is preferably understood to mean that an object-side focal point of the transmitting and receiving radiation is aligned with a measuring point on, in or on the measuring object, in particular that the object-side focal point of the measuring device lies on the measuring surface of the measuring object or in a specific layer of the measuring object. This depends on the measuring task. For example, in a layer thickness measurement, the object-side focal point can be on the measuring surface of the measuring object or on the base body of the measuring object, on which at least one layer,in particular a lacquer layer is applied, can be understood as a defined position to the measuring object.

[0022] 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. This external nominal operating point is preferably a so-called tool center point (TCP). The handling device can have its own tool coordinate system, and the TCP is used as the basis for simple control. This enables short cycle times for the relative positioning of the measuring device and the measuring object, as well as scanning or relative movement of the measuring device and the measuring object to perform a measurement at multiple measuring points.

[0023] The object underlying the invention is further achieved by a method for the relative positioning of a transmit and receive radiation of a THz device to a measurement object for carrying out a measurement on the measurement object, wherein a measuring device according to one of the previously described embodiments is aligned with a handling device relative to the measurement object and the object-side focal point of the transmit and receive radiation is positioned relative to the measurement object and wherein the setting of a preferred orthogonal angle of the transmit and receive radiation to the measurement object, in particular to the object plane or measurement surface of the measurement object, is controlled by the at least one angle adjusting element on the at least one reflective element in the transmit and receive radiation of the THz device.This method enables the measuring device to be moved relative to the measurement object into an observation position in order to subsequently carry out a distance and / or angle measurement of the transmitted and received radiation of the THz device or the separate, preferably optical sensor to the measurement object and to carry out a controlled or regulated correction for the relative positioning of the measuring device to the measurement object by means of the at least one angle adjusting element of the at least one reflective element in the transmitted and received radiation until, in particular, predetermined tolerances with regard to the distance and the angle between the measuring device or the object-side focal point of the transmitted and received radiation of the THz device and the measurement object are achieved.

[0024] The relative positioning of the measuring device to the measurement object is advantageously controlled by an external controller, in particular by a controller of the handling device, wherein the object-side focal point of the transmitting and receiving radiation and the external nominal operating point of the handling device coincide or are brought into alignment by the controller by bringing the points into alignment. This essentially results in a rotational movement of the measuring device, in particular of the at least one reflective element, around the nominal operating point, which enables a simple angle correction without any associated change in distance.

[0025] For the relative positioning of the measuring device to the measurement object, according to a preferred embodiment of the method, a distance between the measuring device and the measurement object can first be recorded. In the one case, where the recorded distance exceeds a predefined value, repositioning takes place. In the other case, where the recorded distance falls below a predefined value, stored reference spectra of the measurement object in the controller are compared to the actually recorded distance. Subsequently, after a defined or predetermined distance has been reached, an angular change of at least one reflective element and / or the measuring device to the measurement object is controlled until a predetermined angle of the transmitted and received radiation to the measurement object is reached.This predetermined distance of the object-side focal point of the transmitted and received radiation and the predetermined angular position of the measuring device relative to the measurement object correspond to a target position of the THz device relative to the measurement object. In this target position, the transmitted and received radiation of the THz device is preferably aligned orthogonally to the measurement object, in particular to an object plane of the measurement object. This allows for increased measurement quality while preferably maintaining a power loss of less than 10% at 4 THz.

[0026] Alternatively, it can be provided that the relative positioning of the measuring device to the measuring object is initially carried out by detecting an angle of the reflecting element to the measuring object and, after the reflecting element has assumed a defined angle, a defined distance of the object-side focal point of the transmitting and receiving radiation between the measuring device and the measuring object is subsequently approached or controlled.

[0027] It can also be provided that a distance of the object-side focal point of the transmitting and receiving radiation and an angle of the at least one reflecting element of the measuring device to the measuring object are controlled simultaneously or alternately during the movement of the handling device and / or the measuring object.

[0028] In the above-described embodiments, an angle change of the transmitted and received radiation relative to the measurement object can be adjusted additionally or simultaneously with the at least one angle adjustment element of the at least one reflective element, wherein an orthogonal alignment of the transmitted and received radiation relative to the measurement object is preferably adjusted. Adjusting a relative distance and / or a relative angle refers to the distance and / or angle between the measuring device and the measurement object, wherein both the measuring device relative to the measurement object and the measurement object relative to the measuring device, or both simultaneously, can be moved relative to one another and / or their positions can be changed.

[0029] The change in distance and / or angle for positioning the measuring device relative to the measurement object can be detected, for example, by at least one separate, preferably optical, sensor. Alternatively, this change in distance and / or angle can be detected based on THz measurement signals of the THz radiation. A combination is also possible. To optimize the relative positioning of the measuring device relative to the measurement object, changes in the angular position of the at least one reflective element can be controlled by the controller during the distance and / or angle measurement of the at least one reflective element. This can enable optimization of the relative positioning of the measuring device or of the transmitted and received radiation of the THz device relative to the measurement object.

[0030] A preferred embodiment of the method is based on the following successive steps:

[0031] The object-side focal point of the transmitted and received radiation is positioned relative to the measurement object by controlling the handling device to the target position of the measurement object stored in the controller. At least one distance measurement and / or angle measurement is then carried out to determine the actual relative position of the measuring device to the measurement object. If the distance and / or angle reached is outside a tolerance range, the distance and / or angle is corrected by following the movement or repositioning process. The stored reference spectra of the measurement object in the controller are then compared with the actually recorded distance of the object-side focal point of the transmitted and received beams to the measurement object, in particular after the final position of the distance between the measurement object and the measuring device has been reached.In the other case, where the defined distance has already been undershot, a comparison is made with the stored reference spectra of the measurement object. Subsequently, at least two measurements are carried out using THz radiation with differing angular positions of the at least one reflective element. From this, at least one correction value is determined for controlling the at least one reflective element and a movement of the at least one reflective element by the correction value to a desired position is controlled, wherein in the desired position the transmit and receive radiation is preferably aligned orthogonally to the measurement object. Subsequently, the measurements can be started and carried out using the THz device. A layer thickness measurement, for example of paint layers on a vehicle body, is preferably carried out.

[0032] While the measuring device is being positioned relative to the measurement object, a distance measurement can be performed by the at least one separate, preferably optical sensor and / or by THz radiation from the THz device, and the measuring device can be moved into a controlled manner for acquisition, wherein a change in the angular position of the at least one reflective element is controlled, in particular during the distance measurement to the object-side focal point. Multipoint triangulation is preferably performed by this separate optical sensor for distance and / or angle correction. Structured or scanning illumination in the visible or near-infrared range is preferably used for this purpose. As soon as the measurement object reaches a distance from the measuring device at which a THz pulse from the measurement object is detected by the THz radiation, a further distance and / or angle correction can be optimized based on the THz signal.The invention, as well as further advantageous embodiments and developments thereof, are described and explained in more detail below with reference to the examples shown in the drawings. The features evident from the description and the drawings can be used individually or in any combination according to the invention. They show:

[0033] Figure 1 is a perspective view of a positioning device with a measuring device aligned with a measuring object,

[0034] Figure 2 is a schematic view of a structure of the measuring device,

[0035] Figure 3 is a schematic view of an alternative construction of the measuring device to Figure 2, and

[0036] Figure 4 shows a schematic sequence of steps for the relative positioning of the measuring device and the measuring object to each other.

[0037] Figure 1 shows a schematic view of a measuring device 11 in a measuring position for performing a measurement on a measurement object 12. A positioning device 50 comprises at least one handling device 14, such as a multi-axis robot. Furthermore, a controller 25 is provided, which can be part of the positioning device 50. The controller 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 provided on a handling device 14. The measuring device 11 can be positioned relative to the measurement object 12 by the handling device 14. In individual application cases, it can be provided that the measuring device 11 is positioned stationary and the measurement object 12 is moved relative to the measuring device 11.Applications are also possible in which a relative positioning of the measuring device 11 and the measuring object 12 takes place, ie that the measuring device 11 and the measuring object 12 change simultaneously or alternately in terms of distance and / or angle to one another.

[0038] The measuring device 11 comprises a THz device 16, which has a transmitter 17 for emitting a transmitted radiation 18 and a receiver 19 for receiving a received radiation 20. A transceiver 35 is preferably provided, whereby the transmitted and received radiation 18, 20 are coaxial with each other.

[0039] The measuring device 11 is arranged on the handling device 14 via a connection point 13. The handling device 14 comprises, in particular, an external nominal operating point 22, also referred to as a tool center point (TCP), extending from the connection point 13. This means that the handling device 14 has an imaginary operating point in its coordinate system, which can be controlled by a controller 25 for a spatial movement of the connection point 13 and thus the measuring device 11.

[0040] Figure 2 shows a schematic view of a structure for one embodiment of the measuring device 11. Starting from the THz device 16, in particular a transceiver, the THz 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 can be provided between them in order to direct the THz radiation, preferably in a focused manner, onto the reflective element 24. The THz radiation is deflected at the reflective element 24 and fed to an optical device 28, wherein the optical device 28 focuses the THz radiation onto a focal point 30. This focal point 30 is a so-called object-side focal point, which lies in an object plane 38.In a measuring position of the measuring device 11 relative to the measuring object 12, this object-side focal point 30 is preferably located on or in the measuring object 12 or in the object plane 38 of the measuring object 12. The measuring device 11 may further comprise a detection device 32 by which the measuring object 12 or the object-side focal point 30 of the transmitting and receiving radiation 18, 20 on the measuring object 12 can be detected.

[0041] Furthermore, a separate, preferably optical sensor 34 can be provided on or in a housing 15 of the measuring device 11. This sensor 34 operates with radiation in the visible or near-infrared range. This sensor 34 can detect a distance between the measuring device 11 and the measurement object 12. Advantageously, this sensor 34 can be aligned with the transmit and receive radiation 18, 20 of the THz device 16 such that the radiation of the optical sensor 34 is coaxial with the transmit and receive radiation 18, 20 of the THz device 16.

[0042] In the exemplary embodiment according to Figure 2, the optical device 28 comprises a first and a second optical element 36, 37. The optical device 28 is preferably designed as an imaging optical device 28. For example, these can be designed as parabolic mirrors. Advantageously, the focal lengths of the optical elements 36, 37 differ from one another, wherein in particular the focal length fi 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 can, in particular, enable a greater depth of field and thus a reduction in distance sensitivity. At least the second optical element 37 can be movable along an optical axis 42 to adjust the focus position.

[0043] The object-side focal point 30 and a conjugate focal point 44 lie in the optical axis 42 of the optical device 28 in an image plane. When the measuring device 11 is aligned with the optical axis 42 perpendicular to the measuring surface, the main beam 51 of the transmitted and received radiation 18, 20 lies in the optical axis 42. A rotation axis 46 of the reflective element 24 preferably lies in the conjugate focal point 44. The rotation axis 46 can form a center of rotation 45 of the reflective element 24, so that the transmitted and received radiation rotates around the object-side focal point 30.This has the consequence that in the case of a non-orthogonal positioning of the measurement object 12 or a tilted object plane 39 to the measuring device 11, a change in the angular position is possible by changing the angle of the reflective element 24, wherein a center of rotation 21 of the transmitted and received radiation coincides with the object-side focal point 30 of the transmitted and received radiation. Thus, the change in the angle of the reflective element 24 in the center of rotation 21 of the transmitted and received radiation does not result in a change in distance. By changing the angular position of the reflective element 24, the tilted object plane 39 can be corrected to the object plane 38, so that a target position is assumed in which the THz radiation is oriented perpendicular to the surface of the measurement object 12, in particular perpendicular to the tilted surface of the measurement object 12. As a result, an angular position ora tilt between the measuring object 12 and the measuring device 11 can be detected and corrected.

[0044] 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, for example, control the reflective element 24 so that it can rotate about the rotation axis 46, preferably about a first spatial direction.

[0045] The angle adjustment element 24b can, for example, control the reflective element 24 to rotate about a further axis of rotation 47, preferably about a further or second spatial direction. The further axis of rotation 47 is preferably aligned perpendicular to the axis of rotation 46, for example the X-axis. The further axis of rotation 47 can also form the center of rotation 45 of the reflective element 24. Both axes of rotation 46 and 47 preferably intersect at the optical axis 48, so that the center of rotation 45 preferably lies at the intersection point of the axes. In an x / y / z coordinate system, which is aligned, for example, as shown in Figure 2, the optical axis 48 lies. The axis of rotation 46 lies on a Y-axis. The further axis of rotation 47 lies on an X-axis. The reflective element 24 can be changed in at least one spatial direction, preferably in two spatial directions, preferably by the at least one angle adjustment element 24a, 24b.

[0046] Figure 3 shows an alternative embodiment of the measuring device 11 to Figure 2. In this embodiment, the optical device 28 comprises only one optical element 36. The reflective element 24 is assigned to the one optical element 36. This reflective element 24 corresponds to the reflective element 24 shown in Figure 2.

[0047] In the direction of the beam axis 48, which preferably lies in the Z-axis, a further reflective element 54 is positioned at a distance from the reflective element 24. This further reflective element 54 can be changed, preferably by the at least one angle adjustment element 24a, 24b, in at least one spatial direction, preferably in two spatial directions, wherein the at least one rotational axis 46, 47, preferably both rotational axes, of the further reflective element 54 are parallel to the rotational axes 46, 47 of the reflective element 24. The further reflective element 54 can correspond to one of the embodiments of the reflective element 24. In a normal position (solid line) of the reflective elements 24, 54, the main beam (central beam) 51 of the transmitted and received radiation 18, 20 lies in the optical axis 42. In addition, only an associated edge beam 52 is shown with a solid line.The measuring surface 38 is aligned perpendicular to the optical axis 42 or the main ray 51.

[0048] If the measuring surface is tilted relative to the measuring device 11, a tilted object plane 39 is present. To compensate, the reflective elements 24, 54 are controlled so that the optical axis 42 of the transmitting and receiving radiation 18, 20 is aligned perpendicular to the tilted surface 39. For example, the main beam (central beam) 51' is shown with dashed lines relative to the aligned elements 24, 54 (also dashed lines).

[0049] The at least one angle adjustment element 24 a, 24 b of the reflective element 24 and / or the further reflective element 54 can be the same in design and / or in the control of the reflective element 24 and the further reflective element 54.

[0050] Also, only one angle adjusting element 24 a can control the angular position of the reflective element 24 and the other angle adjusting element 24 b can control the further reflective element 54 in the angular position.

[0051] This arrangement allows the same mode of operation as in the embodiment of the measuring device 11 in Figure 2 to be achieved. An object-side focal point 30 of the transmitting and receiving radiation 18, 20 coincides with the center of rotation 21 of the transmitting and receiving radiation 18, 20.

[0052] Preferably, the external nominal operating point 22 of the connection point 19 or of the handling device 14 corresponds to the object-side focal point 30 of the measuring device 11, or the object-side focal point 30 of the measuring device 11 is aligned with the nominal operating point 22 or adjustable thereto, so that a simple positioning of the measuring device 11 relative to the measuring object 12 with the handling device 14 can be enabled.

[0053] Figure 4 below shows a preferred procedure for positioning the measuring device 11 relative to the measuring object 12.

[0054] According to step 61, the measuring device 11 is moved with the handling device 14 toward a measuring point on the measuring object 12, i.e., toward a target position (nominal position). This measuring point of the measuring object 12 has previously been determined or taught in the control system of the handling device 14.During this approach of the measuring device 11 to the measurement object 12, preferably for the relative positioning of the measuring device 11 to the measurement object 12, a distance to the measurement object 12 can first be detected and then, after a defined distance has been reached, a defined angle of the transmitting and receiving radiation 18, 20 of the THz device 16 to the measurement object 12 can be controlled, or for the relative positioning of the transmitting and receiving radiation 18, 20 of the THz device 16 to the measurement object 12, an angle can first be detected and then, after a defined angle has been reached, a defined distance between the measuring device 11 and the measurement object 12 can be controlled.Alternatively, a relative distance of the measuring device 11 and an angle of the transmit and receive radiation 18, 20 of the THz device 16 to the measurement object 12 can be controlled simultaneously or alternately during the movement of the handling device 14 and / or the measurement object 12. After reaching a predetermined distance, which is either detected by the separate, preferably optical, sensor 34 or determined via the controller 25 of the handling device 14, a reduction in the speed of the movement follows according to step 62 to approach the measuring device 11 into the measuring position to the measurement object 12.During this approach, a change in distance and / or angle can be determined by the separate, preferably optical, sensor 34 and / or by the determined properties of the transmit and receive radiation 18, 20 of the THz device 16, wherein an ID scan or 2D scan of the surface of the measurement object (12) can be carried out by the THz device 16.

[0055] In step 63, at least one distance measurement and / or angle measurement can be performed to determine the actual relative position of the measuring device 11 to the measurement object 12, wherein either a) repositioning occurs if the detected distance exceeds a defined value, or b) a comparison of stored reference spectra of the measurement object 12 in the controller to the actually detected distance of the measuring device 11 to the measurement object 12 occurs if the detected distance falls below the defined value. Preferably, a software correction is performed, i.e., the measuring device 11 does not need to be moved.

[0056] In a subsequent step 64, an angle measurement is performed to determine the alignment of the transmit and receive radiation 18, 20 of the THz device 16 with the measurement object 12. Based on this angle measurement, correction values ​​are determined to align the transmit and receive radiation 18, 20 with the at least one reflective element 24, 54 with respect to its angular position in a preferably orthogonal position to the measurement object 12. Controlling the at least one optical reflective element 24, 54 may be sufficient to perform the angle correction. By controlling two mutually different angular positions of the and / or the reflective elements 24, 54, a correction value for the alignment of the reflective element 24, 54 can be controlled, so that a tilted arrangement of the measurement object 12 or a tilted surface of the measurement object 12 with respect to the geometric axis 42 of the optical device 28 is compensated.

[0057] To determine the angle correction, a THz signal is evaluated. Additionally and / or alternatively, an angle measurement can also be performed by the at least one optical sensor 34.

[0058] After the controlled angular position of the at least one reflective element 24 has been assumed, the measurement on the measurement object 12, such as a layer thickness measurement, can be carried out by the THz device 16 according to step 65.

Claims

Claims 1. A measuring device with a THz device (16) for transmitting and receiving THz radiation for carrying out a measurement, in particular layer thickness measurement, on a measurement object (12), with a transmitter (17) for emitting a transmitted radiation (18) onto the measurement object (12) and a receiver (19) for detecting a received radiation (20), both of which have an object-side focal point (30), characterized in that the transmitted radiation and received radiation (18, 20) are coaxial to one another, that at least one reflective element (24, 54) with at least one angle adjustment element (24 a, 24 b) is arranged in the transmitted and received radiation (18, 20), wherein the at least one angle adjustment element (24 a, 24 b) is configured to change an angular position of the at least one reflective element (24, 54) about at least one rotation axis (46, 47) in at least one spatial direction by a control (25) is controllable, and in which at least one rotation axis (46,47) a rotation center (45) is located, that at least one optical device (28) is provided between the at least one reflecting element (24, 54) and the object-side focal point (30) of the transmitting and receiving radiation (18, 20), and that the object-side focal point (30) of the transmitting and receiving radiation (18, 20) formed by the optical device (28) and a rotation center (21) of the transmitting radiation (18) and receiving radiation (20), which is formed by the at least, an angle adjusting element (24a, 24b) can be controlled.

2. Measuring device according to claim 1, characterized in that the center of rotation (45) of the one reflective element (24) which is assigned to the measurement object (12) and which is preferably designed as at least one axis of rotation (46, 47) of the one reflective element (24) lies in a conjugate focal point (44) with respect to an object plane (38) of the optical device (28), in which the object-side focal point (30) lies.

3. Measuring device according to claim 2, characterized in that the conjugate image-side focal point (44) of the transmitting and receiving radiation (18, 20) lies on the at least one reflective element (24).

4. Measuring device according to 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. Measuring device according to one of the preceding claims, that between the THz device (16) and the optical device (28), which comprises only one optical element (36), two mutually aligned reflective elements (24, 54) are provided.

6. Measuring device according to claim 5, characterized in that the at least one reflective element (24, 54) is adjustable by the at least one angle adjusting element (24 a, 24 b) in at least one spatial direction, preferably in at least two spatial directions.

7. Measuring device according to one of claims 1 to 4, characterized in that the optical device (28) comprises two mutually aligned optical elements (36, 37) for its optical axis (42), which are arranged between the at least one reflective element (24) assigned to the measurement object (12) and the object-side focal point (30), and preferably the at least one optical element (36, 37) is movable along the optical axis (42) for adjusting the focus position.

8. Measuring device according to claim 7, characterized in that the optical device (28) with two optical elements (36, 37) comprises a first optical element (36) assigned to the one reflecting element (24) with a focal length fi and a second optical element (37) assigned to the object-side focal point (30) with a focal length f2, wherein the focal length f2 > fi.

9. Measuring device according to one of claims 1 to 8, characterized in that the optical device (28) is designed for a high distance tolerance and in particular has a long focal length optic with a Rayleigh length of the transmit and receive radiation of in particular > 6 mm, preferably > 10 mm at a frequency of 1 THz and advantageously the distance tolerance is increased by an additional software correction.

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

11. Measuring device according to one of the preceding claims, characterized in that at least one separate sensor (34) for distance and / or angle measurement and / or topology measurement between the measuring device (11) and the measuring object (12) is provided on or in the measuring device (11).

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

13. Measuring device according to claim 11 or 12, characterized in that the at least one separate sensor (34) is aligned coaxially with the transmitting and receiving radiation (18, 20) of the THz device (16), and in particular between the transmitter (17) and receiver (19) of the THz device (16) and the at least one reflective element (24, 54) is coaxially superimposed with the transmitting and receiving radiation (18, 20) of the THz device (16).

14. Measuring device according to claim 13, characterized in that for the coaxial superposition of the transmit and / or receive radiation (18, 20) of the at least one separate sensor (34) with the transmit and receive radiation (18, 20) of the THz device (16), an optical coupling element (23) is provided and is designed as a reflection element for the transmit and receive radiation (18, 20) of the THz device (16).

15. Positioning device for the relative positioning of a measuring device (11) with a THz device (16) for transmitting and / or receiving THz radiation relative to a measurement object (12) for carrying out a measurement on the measurement object (12), with a handling device (14) which has a connection interface (13), wherein an external nominal operating point (TCP) is assigned to the connection interface (13), characterized in that a measuring device (11) according to one of claims 1 to 14 is arranged at the connection interface (13) of the handling device (14), that the object-side focal point (30) of the transmitted and received radiation (18, 20) of the measuring device (11) and the at least one center of rotation (21; 45) of the transmitted radiation and received radiation (18, 20) coincide, and that the measuring device (11) can be positioned relative to the measurement object (12) by means of the handling device (14), so that the object-side focal point (30) of the transmitted radiation and received radiation (18, 20) is aligned in a defined position relative to the measurement object (12).

16. Positioning device according to claim 15, characterized in that the at least one center of rotation (21; 45) of the transmitting and receiving radiation (18, 20) coincides with the external nominal operating point (TCP) of the handling device (14).

17. Method for the relative positioning of a transmitting and receiving radiation (18, 20) of a THz device (16) to a measurement object (12) for carrying out a measurement on the measurement object (12), characterized in that a measuring device (11) according to one of claims 1 to 14 is provided with a handling device (14) relative to the The measuring object (12) is aligned, wherein the object-side focal point (30) of the transmitting and receiving radiation (18, 20) is positioned relative to the measuring object (12), which focal point preferably lies on the surface of the measuring object (12), and in that the setting of an angle of the transmitting and receiving radiation (18, 20) to the measuring object (12) is controlled by the at least one angle adjusting element (24 a, 24 b) on the at least one reflecting element (24, 54) in the beam path of the transmitting and receiving radiation (18, 20) of the THz device (16).

18. The method according to claim 17, characterized in that the relative positioning of the measuring device (11) to the measuring object (12) is controlled by an external control (25), in particular control of the handling device (14), and the object-side focal point (30) of the transmitted radiation and received radiation (18, 20) and the external nominal operating point (TCP) of the handling device (14) coincide.

19. Method according to one of claims 17 or 18, characterized in that for the relative positioning of the measuring device (11) to the measurement object (12), first a distance to the measurement object (12) is detected and then, after taking a defined distance, a defined angle of the transmitting and receiving radiation (18, 20) of the THz device (16) to the measurement object (12) is controlled, or that for the relative positioning of the transmitting and receiving radiation (18, 20) of the THz device (16) to the measurement object (12), first an angle is detected and after taking a defined angle, a defined distance between the measuring device (11) and the measurement object (12) is subsequently controlled, or that simultaneously or alternately a relative distance of the measuring device (11) and an angle of the transmitting and receiving radiation (18, 20) of the THz device (16) to the measurement object (12) is controlled during the displacement movement of the handling device (14) and / or the measurement object (12), and wherein additionally or simultaneously a relative angle of the transmitting and receiving radiation (18, 20) to the measurement object (12) is set with the at least one angle adjusting element (24 a, 24 b) of the at least one reflective element (24, 54), preferably orthogonally, to the measurement object (12).

20. Method according to one of claims 17 to 19, characterized in that the distance and / or angle change for positioning the measuring device (11) and / or transmitting and receiving radiation (18, 20) of the THz device (16) to the measuring object (12) is detected by at least one separate sensor (34) and / or based on THz measuring signals of the THz radiation, and preferably during the distance and / or angle measurement the at least one angle adjusting element (24 a, 24 b) is controlled to change the angular position of the at least one reflecting element (24, 54).

21. Method according to one of claims 17 to 20, characterized by the following steps: Relative positioning of the object-side focal point (30) of the transmitting and receiving radiation (18, 20) to the measuring object (12) by controlling the handling device (14) on the target position of the measuring object (12) stored in the control (25), Carrying out at least one distance measurement and / or angle measurement to determine the actual relative position of the measuring device (11) to the measuring object (12), wherein a) repositioning takes place if the detected distance exceeds a defined value, or b) a comparison of stored reference spectra of the measuring object (12) in the control system to the actually detected distance of the measuring device (11) to the measuring object (12) takes place if the detected distance falls below the defined value, and Carrying out at least two measurements, preferably by means of THz radiation, at mutually differing angular positions of the at least one reflecting element (24, 54) and determining a correction value for the control of the at least one angle adjusting element (24 a, 24 b) and moving the at least one angle adjusting element (24 a, 24 b) by the correction value into the desired position, in which the transmitting and receiving radiation (18, 20) of the THz device (16) is preferably aligned orthogonally to the measurement object (12), and Carrying out measurements by means of the THz device (16) for transmitting and receiving THz radiation to carry out a measurement, in particular a layer thickness measurement.

22. Method according to claim 21, characterized in that during the positioning of the measuring device (11) to the measuring object (12) at least one distance measurement and / or angle measurement is carried out by the at least one separate, preferably optical sensor (34) and / or the transmitting and receiving radiation (18, 20) of the THz device (16), and the measuring device (11) is moved in a controlled manner to assume the desired position, wherein, preferably during the positioning of the measuring device (11) relative to the measurement object (12), a change in the angular position and / or the distance of the at least one reflective element (24, 54) is controlled, a correction value for controlling the at least one angle adjusting element (24 a, b) is determined, and the at least one angle adjusting element (24 a, b) is controlled by the correction value into the desired position, in which the transmitting and receiving radiation (18, 20) of the THz device (16) is preferably aligned orthogonally to the measurement object (12).

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