Method and apparatus for processing data associated with a model characterizing terahertz radiation propagation

Abstract

The present invention relates to a method for processing data associated with a model characterizing the propagation of terahertz (THz) radiation in a spatial region comprising at least one terahertz device for emitting and / or receiving terahertz radiation and / or at least one object which can be subjected to terahertz radiation, the method comprising: providing the model; characterizing the propagation of terahertz radiation in a region of at least one interface between two adjacent media in the spatial region by means of the model, wherein the model has a term which depends on at least one of the following elements: a) the frequency of the terahertz radiation, b) the spatial extension of at least one of the two adjacent media, for example along a first spatial direction.

Description

Technical Field

[0001] This disclosure relates to a method for processing data that is associated with a model characterizing the propagation of terahertz (THz) radiation within a space region.

[0002] This disclosure also relates to an apparatus for processing data associated with a model characterizing the propagation of terahertz (THz) radiation within a space region. Summary of the Invention

[0003] An exemplary embodiment relates to a method of processing data associated with a model characterizing the propagation of terahertz (THz) radiation in a spatial region, wherein the spatial region includes at least one terahertz device for emitting and / or receiving the terahertz radiation and / or at least one object capable of being exposed to the terahertz radiation, wherein the method includes: providing a model; characterizing the propagation of the terahertz radiation in a region of at least one interface between two adjacent media within the spatial region by means of the model, wherein the model includes a term characterizing the THz radiation, the term depending on at least one of the following elements: a) the frequency of the terahertz radiation; b) the spatial extension and / or location of at least one of the two adjacent media, for example, along a first spatial direction.

[0004] In another exemplary embodiment, it is provided that: the model characterizes terahertz radiation at least once at at least one interface between at least two media, wherein, for example, the model characterizes terahertz radiation at at least two interfaces between different media multiple times, wherein, for example, the term characterizing terahertz radiation has a different value for each of the at least two interfaces.

[0005] In another exemplary embodiment, a model is provided that characterizes terahertz radiation at multiple interfaces between every two adjacent media in a spatial region by means of a coherent superposition function, wherein the term is set as a weighting factor in addition to the weighting factors for at least some components of the coherent superposition function.

[0006] In another exemplary embodiment, it is provided that the model has a first component, which characterizes a sample measurement of the object in a reflecting or transmitting arrangement by means of terahertz radiation, wherein, for example, the first component may be characterized in the frequency domain for, for example, a reflecting arrangement, based on the following equation:

[0007]

[0008] Among them, F S(ω,x,y,z) represents the field strength of the sample signal, which is, for example, frequency-dependent, where ω represents the angular frequency associated with the frequency of the terahertz radiation, where x represents the first spatial coordinate, where y represents the second spatial coordinate, where z represents the third spatial coordinate, and where I0(ω,x,y,z) represents the field strength of the terahertz radiation at the transmitter that generates the terahertz radiation, which is, for example, frequency-dependent, where exp[] represents the exponential function, where i represents the imaginary unit, where c0 represents the speed of light in vacuum, where L represents the distance between the terahertz device and the reference object, where ΔD represents the offset between the reference object and the object, and where n A Characterizing the refractive index of a medium existing in the spatial region, the medium being, for example, air, where, ∈ A The extinction coefficient characterizes the medium existing in the spatial region, where Φ0(ω,x,y,z) characterizes the phase of the terahertz radiation at the emitter that generates the terahertz radiation, the phase being, for example, frequency-dependent, where t A1 The transmittance coefficient at the interface between the medium present in the spatial region and the layer characterizing the surface of the object, where t 1A The transmittance coefficient is defined as the coefficient of light transmitted from the layer representing the surface of the object to the interface of the medium existing in the spatial region, where r 1S The reflectance coefficient at the interface from the layer to the substrate of the object is characterized, where R represents the reflectivity, which in turn represents the quantity and / or sequence order of the reflection and / or transmission of the terahertz radiation, where r 1A The reflection coefficient is defined as the coefficient of reflection at the interface between the layer representing the surface of the object and the medium existing in the spatial region, where G(D,R,ω,x,y,z,α,β,Ω) represents the term or weighting coefficient characterizing the terahertz radiation, where D represents the layer thickness, n represents the refractive index of the layer, e represents the extinction coefficient of the layer, and r... A1 The reflection coefficient at the interface from the medium present in the spatial region to the layer characterizing the surface of the object, wherein α and / or β optionally characterize the angular orientation of the terahertz device relative to the object, wherein Ω optionally characterizes the properties of the surface of the object, wherein the properties of the surface of the object include at least one of, for example, the shape of the surface, such as curvature; b) the roughness of the surface.

[0009] In another exemplary embodiment, the model is provided to have a second component, which characterizes a reference measurement of a reference object in a reflecting or transmitting arrangement by means of the terahertz radiation, wherein, for example, the second component can be characterized in the frequency domain, for example, the reflecting arrangement, based on the following equation:

[0010]

[0011] Where F(ω,x,y,z) represents the field strength of the reference signal, which is, for example, frequency-dependent, where r AM Characterizing the reflectance at the interface between the medium present in the space region and the surface of the reference object.

[0012] In another exemplary embodiment, it is provided that the model, for example, is for reflection arrangements in the frequency domain, and the frequency domain can be characterized, for example, based on the following equation:

[0013]

[0014] Here, H(ω) characterizes the transmission function of the terahertz radiation, which is, for example, related to a reference measurement.

[0015] In another exemplary embodiment, it is provided that, alternatively or in addition to the following: a) the frequency of the terahertz radiation; and / or b) the spatial extension and / or position of at least one of the two adjacent media, for example, along a first spatial direction, the item depending on at least one of the following elements: c) reflectivity characterizing the quantity and sequence order of the reflections; d) the angular orientation of the terahertz device relative to the object and / or the reference object; e) for example, the distance between the at least one terahertz device and / or the at least one object; f) the characteristics of the surface of the at least one object, such as the shape of the surface and / or the roughness of the surface.

[0016] In another exemplary embodiment, it is provided that the model models the distance-dependent spectral variation of the transmission function of the terahertz radiation as distance-dependent and / or depth-dependent attenuation and / or amplification by using, for example, the terms and / or the weighting factors.

[0017] In another exemplary embodiment, it is provided that the model models the angle-dependent spectral variation of the transmission function of the terahertz radiation as an angle-dependent attenuation and / or amplification by using, for example, the terms and / or the weighting factors.

[0018] In another exemplary embodiment, the model is provided to model the spectral variation of the transmission function of the terahertz radiation based on the surface of the at least one object / at least one characteristic of the surface, such as the shape of the surface and / or the roughness of the surface, by using, for example, the terms and / or the weighting factors.

[0019] In another exemplary embodiment, the model is provided as follows: the model includes an object having multiple layers formed of different media, wherein, for example, the model characterizes at least one of the following elements: a) reflection and / or transmission of the terahertz radiation in the object, for example, between adjacent layers; b) multiple reflections and / or multiple transmissions of the terahertz radiation in the object; c) virtual reflection points and / or virtual transmission points in the object, which can be characterized, for example, by reflectivity; d) coherent superposition of different reflections and / or transmissions of the terahertz radiation in the object.

[0020] In another exemplary embodiment, the method is provided to further include: determining the item and / or individual values ​​of the item based on an optical model of the system, the system representing the terahertz device and the object and / or reference object, and optionally, the system representing the environmental medium surrounding the terahertz device and the object or the reference object, wherein, for example, the optical model represents the terahertz radiation, for example, a spectral transmission function within the system.

[0021] In another exemplary embodiment, the method is provided to further include: determining the item and / or individual values ​​of the item based on an optical model of the system, the system representing the terahertz device and the object and / or the reference object, and optionally, the system representing the environmental medium surrounding the terahertz device and the object or the reference object, wherein the optical model represents, for example, the amplitude and phase of the spatial spread across the terahertz radiation within the system.

[0022] In another exemplary embodiment, the optical model is provided to take into account the diffraction effect of terahertz radiation.

[0023] In another exemplary embodiment, the method is provided to further include: determining the optical model based on modeling by means of a) ray tracing and / or b) a description based on diffraction theory, such as by means of diffraction integrals, such as Collins integrals, and / or c) parameter calculations with model functionality; and optionally, calibrating the optical model, wherein, for example, the determination and / or calibration of the optical model is performed by frequency-resolved techniques.

[0024] In another exemplary embodiment, the method is provided to further include calibrating the optical model based on at least one of the following elements, for example, relative to the spectral transmission function and / or spatial amplitude and / or phase: a) the angle between the optical axis of the terahertz device and the surface normal of the object or the reference object; b) the distance between the terahertz device and the surface of the object or the reference object; c) the surface / characteristics of the at least one object and / or the reference object, for example, based on the shape of the surface such as curvature and / or the roughness of the surface; d) the frequency of the terahertz radiation.

[0025] In another exemplary embodiment, the spatial location of the reflection point and / or transmission point characterized by the model is changed; based on the change, the characteristics of at least one layer of the object formed by the medium are derived, such as thickness, wherein, for example, at least one of the following elements is used in the derivation: a) performing a correlation method, b) performing a method for pattern recognition, c) determining peaks and / or valleys, d) using a machine learning method, e) performing a fitting method, such as by adapting a model, for example based on least squares.

[0026] In another exemplary embodiment, it is provided that when the spatial location of the reflection point and / or transmission point is changed, for example, in the process of determining the thickness of a layer of an object, the value and / or multiple values ​​of the item or weighting factor are not changed.

[0027] In another exemplary embodiment, it is provided that when the spatial location of the reflection point and / or transmission point is changed, for example, in the process of determining the thickness of a layer of an object, the value and / or multiple values ​​of the item or weighting factor will be changed.

[0028] In another exemplary embodiment, it is provided that the value and / or multiple values ​​of the item or weighting factor are interpolated when the spatial location of the reflection point and / or transmission point is changed by using, for example, available values. In another exemplary embodiment, it is provided that the method further includes: determining, for example, pre-calculating, at least one component and / or optical model of the model, and optionally, storing the result of the determination, for example, the pre-calculated result, wherein, for example, the result is stored in a database.

[0029] In another exemplary embodiment, the method is provided as follows: the method further includes: determining reference data for a plurality of different spatial arrangements of the terahertz device and the object and / or the reference object relative to each other, for example including: arranging the terahertz device and the object and / or the reference object relative to each other in a given arrangement; and determining reference data for the given arrangement, and optionally, repeating the arrangement and determination steps until, for example, a predetermined termination criterion has been reached, wherein the arrangement includes, for example, positioning the terahertz device and / or the object or the reference object by means of a positioning device, such as a robot.

[0030] In another exemplary embodiment, the reference data may be stored at least intermittently using at least one database.

[0031] In another exemplary embodiment, the method is provided to further include: using, for example, a sensor (e.g., another sensor) to determine at least one of the following elements: a) the distance between the terahertz device and the object or the reference object; b) the angular orientation of the terahertz device and the object or the reference object, for example, in a one-dimensional or two-dimensional arrangement; c) the shape of the surface of the object or the reference object / such as the curvature of the surface. In another exemplary embodiment, optical sensors (e.g., for laser distance measurement and / or laser angle measurement), and / or acoustic sensors (e.g., ultrasonic sensors), and / or sensors based on electromagnetic waves (e.g., radar sensors) may be used for this purpose.

[0032] In another exemplary embodiment, the method is provided to further include using distance and / or angular orientation and / or shape in the model, for example, to determine the item and / or the individual values ​​of the item.

[0033] In another exemplary embodiment, the method is provided as follows: the method further includes: determining whether at least one region of interest, for example, a reflection point, is located within a parameter range (the reference range may be characterized, for example, by a distance range and / or an angle range), wherein, for the parameter range, there are values ​​for the terms and / or reference data, for example, that can be characterized by a calculated and / or calibrated transmission function; and based on the determination, changing the spatial arrangement, for example, distance and / or angle, by means of at least one positioning device (e.g., a robot), wherein, for example, the change is repeated until the region of interest is located within the parameter range, and optionally, performing an evaluation.

[0034] Further exemplary embodiments relate to an apparatus for performing the methods according to these embodiments.

[0035] Another exemplary embodiment relates to a machine-readable storage medium including instructions that, when executed by a computer, cause the computer to perform the method according to these embodiments.

[0036] Another exemplary embodiment relates to a computer program including instructions that, when executed by a computer, cause the computer to perform the method according to these embodiments.

[0037] Another exemplary embodiment relates to a data carrier signal that transmits and / or characterizes the computer program according to these embodiments.

[0038] Further exemplary embodiments relate to a method and / or device according to these embodiments and / or machine-readable storage medium according to these embodiments and / or computer program according to these embodiments and / or data carrier signal according to these embodiments for use in at least one of the following elements: a) determining at least one characteristic of the object, such as the layer thickness of at least one layer of the object; b) enhancing the accuracy of the model, for example by taking into account that the terahertz radiation propagates in a non-planar form, such as a wave that is not entirely planar; c) taking into account the dependence of the spectral transmission function on the distance to the terahertz device; d) taking into account the dependence of the spectral transmission function on the angle relative to the terahertz device; e) taking into account the surface / characteristics of the surface of the at least one object or reference object, such as the shape of the surface, such as curvature, and / or the roughness of the surface.

[0039] Additional features, usage options, and advantages can be seen in the following description of the exemplary embodiments illustrated in the accompanying drawings. Any feature described or represented herein, either alone or in any combination, forms the object of the exemplary embodiments, regardless of how they are summarized in the claims or subsequent references, and regardless of their representation and / or representation in the specification and / or drawings. Attached Figure Description

[0040] Figure 1 A simplified block diagram of a THz device that will be used with an exemplary embodiment is shown schematically.

[0041] Figure 2 A simplified flowchart according to another exemplary embodiment is schematically shown.

[0042] Figure 3 A simplified block diagram according to another exemplary embodiment is shown schematically.

[0043] Figure 4A A simplified block diagram according to another exemplary embodiment is shown schematically.

[0044] Figure 4B A simplified block diagram according to another exemplary embodiment is shown schematically.

[0045] Figure 5 A simplified block diagram according to another exemplary embodiment is shown schematically.

[0046] Figure 6 A simplified block diagram according to another exemplary embodiment is shown schematically.

[0047] Figure 7 A simplified flowchart according to another exemplary embodiment is schematically shown.

[0048] Figure 8 A simplified flowchart according to another exemplary embodiment is schematically shown.

[0049] Figure 9 A simplified block diagram according to another exemplary embodiment is shown schematically.

[0050] Figure 10 A simplified flowchart according to another exemplary embodiment is schematically shown.

[0051] Figure 11 A simplified flowchart according to another exemplary embodiment is schematically shown.

[0052] Figure 12 A simplified flowchart according to another exemplary embodiment is schematically shown.

[0053] Figure 13 A simplified flowchart according to another exemplary embodiment is schematically shown.

[0054] Figure 14 A simplified flowchart according to another exemplary embodiment is schematically shown.

[0055] Figure 15 A simplified flowchart according to another exemplary embodiment is schematically shown.

[0056] Figure 16 A simplified block diagram according to another exemplary embodiment is shown schematically.

[0057] Figure 17 The illustration schematically shows aspects of usage options according to other exemplary embodiments, and

[0058] Figure 18 A simplified block diagram according to another exemplary embodiment is shown schematically. Detailed Implementation

[0059] Figure 1A block diagram schematically illustrates a THz device 10 suitable for use with the method according to an exemplary embodiment. The THz device 10 is configured, for example, to emit and / or receive THz radiation TS, such as THz radiation TS that has been reflected at or transmitted through the object 20.

[0060] Another exemplary embodiment, Figure 2 This involves a data processing DAT (Data Acquisition Technology). Figure 1 The method, wherein the data DAT is associated with a model MOD characterizing the propagation of terahertz (THz) radiation TS within a space region RB, wherein the space region RB includes at least one terahertz device 10 for emitting and / or receiving terahertz radiation TS, and / or at least one object 20 that may be exposed to terahertz radiation TS, wherein the method includes: providing 100 ( Figure 2 Model MOD; characterized (e.g., described) by means of the model MOD, at least one interface GF between two adjacent media M1, M2 in the space region RB of 102 terahertz radiation TS (reference) Figure 3 The propagation in the region of ), wherein the model MOD includes a term T characterizing the THz radiation TS, the term depending on at least one of the following elements: a) the frequency of the terahertz radiation TS, b) at least one of the two adjacent media M1, M2, for example, the spatial extension D and / or location along the first spatial direction Rx.

[0061] In another exemplary embodiment, two adjacent media M1 and M2 within the spatial region RB may be materials of the THz device 10 (e.g., the material of the THz transmitter). Figure 1 (not shown) and / or optional materials for forming THz optical systems, etc.) and / or media present in the environment UM of space region RB, such as ambient air and / or dry air and / or protective gases, etc., and / or substances of object 20, see according to Figure 3 Exemplary layer structures M1 and M2.

[0062] In another exemplary embodiment, the spatial extension D can be, for example, the thickness, such as the layer thickness of layer M1 of object 20.

[0063] Figure 3 It shows that according to Figure 1 An exemplary structure of object 20, wherein the given structure has, for example, four layers 20-1, 20-2, 20-3, 20-4, each layer being composed of corresponding materials M1, M2, M3, M4. The reference numeral GF-0 indicates the interface between the medium M1 of layer 20-1 and the environmental medium present in the environment UM. Figure 1In the accompanying drawings, reference numeral GF-1 indicates the interface between medium M1 of layer 20-1 and medium M2 of layer 20-2; reference numeral GF-2 indicates the interface between medium M2 of layer 20-2 and medium M3 of layer 20-3; and reference numeral GF-3 indicates the interface between medium M3 of layer 20-3 and medium M4 of layer 20-4. According to... Figure 4A THz radiation propagating within the structure Figure 4A The dashed arrow TS is used to represent this.

[0064] Figure 4B It shows something similar to what is shown according to Figure 4A Examples of the structure of the construction, in which some reflection and / or transmission details of the THz radiation TS component radiated in the form of THz pulses are described, for example, by way of example below.

[0065] In another exemplary embodiment, medium M1 may represent, for example, an environmental medium in the environment UM between the THz device 10 and the object (20).

[0066] In another exemplary embodiment, the medium M4 may, for example, represent a metal substrate. In this example, two layers 20-2 and 20-3 made of other media M2 and M3, such as layers made of a coating material including a polymer (e.g., a coating for coating the substrate M4), may be disposed on the metal substrate.

[0067] In another exemplary embodiment, a model MOD is provided. Figure 1 The term T(t0, t1, t0', t1' and / or at least one transmission t0, t1', t0', t1' of terahertz radiation TS at at least one interface GF-1, GF-2, GF-3 between at least two media M1, M2, M3, M4, is used to characterize terahertz radiation TS at at least two interfaces GF-1, GF-2, GF-3 between various media. For example, the model MOD characterizes multiple reflections and / or multiple transmissions of terahertz radiation TS at at least two interfaces between various media. For example, the term T(t0, t1, t0', t1' characterizing terahertz radiation is used to characterize terahertz radiation.) Figure 1 For each of the at least two interfaces, there are different values ​​T-1 and T-2. Figure 4A ), T-1, T-2, T-3 ( Figure 4B ).

[0068] In another exemplary embodiment, it is provided that the model MOD has a first component MOD-1, which is characterized by terahertz radiation TS for sample measurements of the object 20 in a reflecting or transmitting arrangement, wherein, for example, the first component MOD-1 can be characterized in the frequency domain, for example, in a reflecting arrangement, based on the following equation:

[0069]

[0070] Among them, F S (ω,x,y,z) characterizes the field strength of the sample signal, which is, for example, frequency-dependent (and can be received by the THz device 10 as a component of the THz radiation TS reflected at or transmitted through the object 20), where ω characterizes the angular frequency f (e.g., according to ω = 2πf) associated with the frequency of the terahertz radiation TS, where x characterizes the first spatial coordinate, where y characterizes the second spatial coordinate, where z characterizes the third spatial coordinate, where I0(ω,x,y,z) characterizes the field strength of the terahertz radiation TS at the transmitter 11 that generates the terahertz radiation TS, which is, for example, frequency-dependent, where exp[] characterizes the exponential function, where i characterizes the imaginary unit, where c0 characterizes the speed of light in vacuum, where L characterizes the distance between the terahertz device 10 and the reference object 20' (e.g., having a known structure, such as a metal "layer") Figure 6 ), where ΔD represents the offset between the reference object 20' and the object 20, where n A The characterization exists in the spatial region RB ( Figure 1 The refractive index of a medium in which the medium is, for example, air (e.g., ambient air, dry air), wherein, ∈ A The extinction coefficient characterizes the medium existing in the space region RB, where Φ0(ω,x,y,z) characterizes the phase of the terahertz radiation TS at the emitter 11 that generates the terahertz radiation TS, the phase being, for example, frequency-dependent, where t A1 The interface GF-0, representing the medium existing in the spatial region RB to the layer 20-1 of the surface 20a of the characterized object 20, is characterized by the medium GF-0. Figure 4A The transmission coefficient at t, where t 1A The transmittance coefficient at the interface from layer 20-1 of surface 20a of characterizing object 20 to the medium existing in spatial region RB is defined as r. 1S The reflection coefficient at the interface GF-3 from layer 20-3 of object 20 to substrate 20-4 is characterized, where R represents the reflectivity, which represents the quantity and / or sequence order of reflection and / or transmission of terahertz radiation TS, where r 1A The reflection coefficient is characterized at the interface GF-0 from layer 20-1 of surface 20a of characterizing object 20 to the medium existing in spatial region RB, where G(D,R,ω,x,y,z,α,β,Ω) characterizes the term T or weighting coefficient or said weighting coefficient (weight, for example, the addend of the expression) characterizing the terahertz radiation TS.

[0071]

[0072] Where D represents the layer thickness of layers 20-1 and 20-2, n represents the refractive index of layers 20-1, 20-2, ..., ∈ represents the extinction coefficient of layers 20-1, 20-2, ..., and r A1 The reflection coefficient is characterized at the interface from the medium present in the spatial region RB to the layer characterizing the surface 20a of the object 20, wherein α and / or β optionally characterize the angular orientation of the terahertz device 10 relative to the object 20, wherein Ω optionally characterizes the properties of the surface 20a of the object 20, wherein the properties of the surface 20a of the object 20 include at least one of the following elements, for example: a) the shape of the surface 20a, such as curvature; b) the roughness of the surface 20a.

[0073] In another exemplary embodiment, in Figure 5 The provided information is that the model MOD has a first component MOD-1, which characterizes the sample measurements of the object 20 in a reflective or transmissive arrangement by means of terahertz radiation TS. For example, the first component MOD-1 can be characterized in the frequency domain in the reflective arrangement based on the following equation:

[0074]

[0075] Where FS(ω,x,y,z) characterizes the field strength of the sample signal, which may be, for example, frequency-dependent (and may be received by, for example, THz device 10 as a component of the THz radiation TS reflected or transmitted at object 20), where (e.g., according to ω = 2πf) ω characterizes the angular frequency f associated with the frequency of the terahertz radiation TS, where x characterizes the first spatial coordinate, where y characterizes the second spatial coordinate, where z characterizes the third spatial coordinate, and where I0(ω,x,y,z) characterizes the field strength of the terahertz radiation at the transmitter 11 ( Figure 6 The terahertz radiation field strength TS at point ) can be, for example, frequency-dependent, where exp[] characterizes an exponential function, where i characterizes the imaginary unit, where c0 characterizes the speed of light in vacuum, and where L characterizes the distance between the terahertz device 10 and the reference object 20' (having, for example, a known structure, such as a metal "layer") Figure 6 ), where ΔD represents the offset between reference object 20' and object 20, where n A The characterization exists in the spatial region RB ( Figure 1 The refractive index of a medium, such as air (e.g., ambient air, dry air), where ∈ A The extinction coefficient characterizes the medium existing in the space region RB, where Φ0(ω,x,y,z) characterizes the phase of the terahertz radiation TS at the transmitter 11 that generates the terahertz radiation TS, the phase being frequency-dependent, where t A1The interface GF-0 (characterized from the medium existing in the spatial region RB to the layer 20-1 of the surface 20a of the characterized object 20) represents the interface between the medium and the layer 20-1. Figure 4A The transmission coefficient at point t, where t 1A The transmittance coefficient is defined as the ratio of the layer 20-1 on the surface 20a of the characterizing object 20 to the interface of the medium existing in the spatial region RB, where r 1S The reflection coefficient at the interface GF-3 from layer 20-3 of object 20 to substrate 20-4 is characterized, where R represents the reflectivity, and the reflection coefficient characterizes the quantity and / or sequence order of reflection and / or transmission of terahertz radiation TS, where r 1A The reflection coefficient is characterized at the interface from layer 20-1 of surface 20a of the characterized object 20 to the medium existing in the spatial region RB, where G(D,R,ω,x,y,z,α,β,Ω) is represented by the term T( Figure 1 The term T represents the terahertz radiation TS or the weighting coefficient G (weighted, for example, the summation of the expression):

[0076]

[0077] Where D represents the layer thickness of layers 20-1, 20-2, ..., where n represents the refractive index of layers 20-1, 20-2, ..., where ∈ represents the extinction coefficient of layers 20-1, 20-2, ..., where r A1 The reflection coefficient is characterized at the interface from the medium present in the spatial region RB to the layer characterizing the surface 20a of the object 20, wherein α and / or β optionally characterize the angular orientation of the terahertz device 10 relative to the object 20 (e.g., in one or both spatial directions), wherein Ω optionally characterizes the properties of the surface 20a of the object 20, wherein the properties of the surface 20a of the object 20 include, for example, at least one of the following elements: a) the shape of the surface 20a, such as curvature; b) the roughness of the surface 20a.

[0078] In another exemplary embodiment, in Figure 5 The provided information indicates that the model MOD has a second component MOD-2, which is characterized by terahertz radiation TS at the reference object 20' in a reflecting or transmitting arrangement. The second component MOD-2 can be characterized, for example, in a reflecting arrangement in the frequency domain based on the following equation:

[0079]

[0080] Wherein, F(ω,x,y,z) characterizes the field strength of a reference signal (which may be, for example, a component of THz radiation TS emitted at reference object 20' and received by THz device 10), the field strength being, for example, frequency-dependent, where rAM The reflection coefficient is characterized at the interface between the medium existing in the space region RB and the surface 20a' of the reference object 20'.

[0081] In another exemplary embodiment, the provided model is MOD ( Figure 1 , Figure 5 For example, a reflection arrangement in the frequency domain can be characterized based on the following equation:

[0082]

[0083] Here, H(ω) characterizes the transmission function of terahertz radiation TS, which is, for example, related to a reference measurement.

[0084] In another exemplary embodiment, it is provided that, alternatively or in addition to the following: a) the frequency and / or angular frequency of the terahertz radiation TS; and / or b) at least one of two adjacent media, for example, the spatial extension D and / or position (e.g., characterized by coordinates x, y, z) along a first spatial direction Rx, the term T and / or the weighting factor G (e.g., characterized by the symbol G(D,R,ω,x,y,z,α,β,Ω)). ) The characterization depends on at least one of the following elements: c) reflectivity R, which characterizes the quantity and sequence of the reflections and / or transmissions; d) the angular orientation of the terahertz device 10 relative to the object 20 (e.g., it can be characterized by angles α, β between the optical axis OA of the THz device 10 and the normal vector 20a-n of the surface 20a); e) the distance L between, for example, at least one terahertz device 10 and / or at least one object 20; f) the characteristics of the surface 20a of at least one object 20, such as the shape and / or roughness of the surface 20a.

[0085] In another exemplary embodiment, the sum in the following part of the equation is not evaluated until the upper boundary is “infinity”, as mentioned herein by way of example, but rather until a predetermined finite value R of reflectivity is reached. max Only then is it evaluated. Therefore, in another exemplary embodiment, the following equation applies:

[0086]

[0087] Instead

[0088]

[0089] And / or the following equations apply:

[0090]

[0091] Instead

[0092]

[0093] In another exemplary embodiment, for R max The value can be selected based on at least one of the following elements: a) desired accuracy, b) available computing power.

[0094] In another exemplary embodiment, it is provided that the model MOD models the distance-dependent spectral variation of the transmission function of terahertz radiation TS as distance-dependent and / or depth-dependent attenuation and / or amplification by using, for example, the term T and / or the weighting factor G.

[0095] In another exemplary embodiment, it is provided that the model MOD models the angle-dependent spectral variation of the transmission function of terahertz radiation TS as angle-dependent attenuation and / or amplification by using, for example, the term T and / or weighting factors.

[0096] In another exemplary embodiment, it is provided that the model MOD models the spectral variation of the transmission function of terahertz radiation TS based on at least one property of the surface 20a of at least one object 20, such as the shape and / or roughness of the surface 20a, by using, for example, the term T and / or the weighting factor G.

[0097] In another exemplary embodiment, the model MOD is capable of modeling the propagation of THz radiation TS, which may be referred to as "differential modeling". Thus, for example, for modeling purposes, the paths of individual reflections may be specifically considered (and / or, in this regard, the paths of arbitrary individual reflections).

[0098] In another exemplary embodiment, the model MOD can individually describe possible combinations of reflection and / or transmission of (partial) pulses of THz radiation TS, for example, up to a predetermined maximum order, which can be determined, for example, by a value R. max Characterization. In another exemplary embodiment, the thickness-related distance of each reflection point is defined (e.g., in the region of the interface) by using a corresponding trajectory for each such point. Thus, in another exemplary embodiment, the sample-derived geometric effects of object 20 can be effectively integrated (so that, in another exemplary embodiment, the distance-related spectral variation of the transmission function can be modeled as depth-related attenuation).

[0099] In another exemplary embodiment, the provided model MOD includes multiple layers 20-1, 20-2, 20-3, 20-4 (…). Figure 4BThe object 20, wherein the plurality of layers 20-1, 20-2, 20-3, 20-4 are formed by at least partially different media M1, M2, M3, M4, wherein, for example, the model MOD characterizes at least one of the following elements: a) reflection and / or transmission of terahertz radiation TS in the object 20, for example, between adjacent layers; b) multiple reflections and / or multiple transmissions of terahertz radiation TS in the object 20; c) virtual reflection points and / or virtual transmission points in the object 20, which can be characterized by, for example, reflectivity R / reflectivity R; d) coherent superposition of different reflections and / or transmissions of terahertz radiation TS in the object 20.

[0100] In other exemplary embodiments, such as Figure 7 As shown, the method further includes: based on the system SYS ( Figure 1 The optical model MOD-OPT determines the terms T and / or the individual values ​​T-1, T-2, T-3... of the terms T, and the system SYS characterizes the terahertz device 10 and the object 20 and / or the reference object 20'. Figure 6 ), and optionally, the system SYS characterizes the ambient medium UM surrounding the terahertz device 10 and the object 20 or reference object 20', wherein, for example, the optical model MOD-OPT characterizes the terahertz radiation TS, for example, the spectral transmission function within the system SYS.

[0101] In other exemplary embodiments, the reflection principle further mentioned above by way of example may be used to perform the measurement. Figure 6 The dashed box 12, for example, represents an optional detector for detecting THz radiation TS (e.g., THz radiation reflected at (reference) objects 20, 20').

[0102] In another exemplary embodiment, alternatively, or in addition to the reflection principle further mentioned above by way of example, the measurement can be performed using the transmission principle, referring to... Figure 6 The optional THz detector 12' on the right side is capable, for example, of detecting the component TS' of the THz radiation TS transmitted by the (reference) objects 20, 20'. For embodiments based on measurements according to the transmission principle, the various aspects of the model MOD described herein and the use of item T will be applied in a corresponding manner.

[0103] In other exemplary embodiments, such as Figure 7As shown, the method further includes: determining, based on the optical model MOD-OPT of the system SYS, the terms T and / or individual values ​​T-1, T-2, T-3... of the terms T, wherein the system SYS characterizes the terahertz device 10 and the object 20 and / or the reference object 20', and optionally, the system SYS characterizes the ambient medium UM surrounding the terahertz device 10 and the object 20 or the reference object 20', wherein the optical model MOD-OPT characterizes, for example, the amplitude and phase of the spatial spread of trans-terahertz radiation TS within the system SYS.

[0104] In another exemplary embodiment, the optical model MOD-OPT is provided to take into account the diffraction effect of terahertz radiation TS.

[0105] Figure 7 Optional step 1127 indicates the purpose of item T, or more precisely, the use of item T for example, to determine and / or use the value of model MOD.

[0106] In other exemplary embodiments, such as Figure 8 As shown, the method further includes: determining an optical model MOD-OPT based on modeling by means of a) ray tracing 120a, and / or b) a description based on diffraction theory 120b, such as by means of diffraction integrals, such as Collins integrals, and / or c) parameter calculations with model functionality 120c, and optionally, calibrating the optical model MOD-OPT 122, wherein, for example, the determination 120 and / or the calibration 122 of the optical model MOD-OPT are performed by frequency-resolved techniques.

[0107] In another exemplary embodiment, the method is provided as follows: the method further includes calibrating the 122 optical model MOD-OPT based on at least one of the following elements, for example, relative to the spectral transmission function and / or spatial amplitude and / or phase: a) the optical axis OA of the terahertz device 10 ( Figure 9 a) Angles α and β between the surface normals 20a-n of object 20 or reference object 20' and the surface of terahertz device 10; b) Distance (L) between the terahertz device 10 and the surface 20a of object 20 or reference object 20'; c) Characteristics of at least one surface 20a of object 20 and / or reference object 20', such as the shape FO of the surface 20a, 20a' and / or the roughness of the surface 20a, 20a'; d) Frequency of terahertz radiation TS.

[0108] Figure 9 The dashed box 11 represents an optional emitter used to generate THz radiation (TS), and Figure 10The dashed box 12 represents an optional detector for detecting THz radiation TS, such as a portion of the THz radiation TS that has already been reflected or transmitted at object 20 and / or at reference object 20'.

[0109] In another exemplary embodiment, the calculation of the optical model MOD-OPT is performed by starting from a “starting plane” (which may be characterized, for example, by the THz transmitter 11) and extending to the object 20 (including, for example, positional variations of the object 20 within a local range and / or angular range) via an optional optical (THz) system (not shown) that may be provided where appropriate, and returning from the object 20 to the THz detector 12 (“target plane”) via the optional optical system.

[0110] In another exemplary embodiment, by changing the geometry (taking into account interference with respect to the shape of (object 20) and / or distance and angle in one or two spatial directions), the transfer function of the THz signal can be calculated using frequency-resolved techniques, and in a further exemplary embodiment, the term T can be determined based on this transfer function.

[0111] In another exemplary embodiment, the receive path and transmit path can be pre-calculated separately and stored, for example, in a database DB. The receive path can be characterized, for example, by the distance from object 20 to THz detector 12. The transmit path can be characterized, for example, by the distance from THz transmitter 11 to object 20.

[0112] In another exemplary embodiment, the model used as the optical model MOD-OPT may be, for example, a parametric optical model based on an ABCD matrix, which characterizes, for example, the moments of the power density distribution and / or the propagation of said moments.

[0113] In another exemplary embodiment, the model used as the optical model MOD-OPT can be, for example, a numerical optical model.

[0114] In other exemplary embodiments, such as Figure 10 As shown, the method further includes: changing the spatial location of reflection points and / or transmission points (e.g., in the region of the interface of interfaces GF-0, GF-1...) characterized by the model MOD 130; and deriving, based on the change 130, the characteristics of at least one layer 20-2 of the object 20 formed by the medium M2 132. Figure 4B The characteristic is, for example, thickness D-M2, wherein, for example, at least one of the following elements is used in the derivation 132: a) performing the 132a correlation method; b) performing the 132b method for pattern recognition; c) determining the 132c peaks and / or valleys; d) using the 132d machine learning method; e) performing the 132e fitting method.

[0115] In other words, in another exemplary embodiment, at least one parameter of the model MOD is being modified until, for example, the transmission function of the THz radiation TS characterized by the model corresponds to a predefined tolerance measurement, for example, to at least one transmission function of the determinable THz radiation TS, and / or has been determined by a measurement of object 20. In another exemplary embodiment, the measurement may be performed, for example, by the derivation based on at least one of aspects a) to e), wherein the transmission function is:

[0116]

[0117] In other exemplary embodiments, such as Figure 12 As shown, the method further includes: determining 140, for example, pre-calculating, at least one component of model MOD, MOD-1, MOD-2, and / or optical model MOD-OPT; and optionally, at least temporarily storing 142 the result VE of determining 140, for example, pre-calculating, wherein, for example, the result VE is stored in a database DB (see also...). Figure 1 )middle.

[0118] In another exemplary embodiment, for example, model MOD and / or at least one component MOD-1, MOD-2 of model MOD are pre-calculated for multiple possible parameter values ​​(e.g., layer thickness D-M2 of different layers of object 20), such that the characteristics of object 20 (e.g., layer thickness of layer 20-2 and / or layer thickness D-M2) can be effectively determined, for example by comparing the transmission function H for THz radiation TS with at least one possible transmission function pre-determined by the pre-calculation 140.

[0119] In other exemplary embodiments, such as Figure 13 As shown, the method further includes: determining reference data RD for a plurality of different spatial arrangements (e.g., characterized by distance L and / or at least one angle α, β) of the terahertz device 10 and the object 20 and / or the reference object 20' relative to each other, for example including: arranging the terahertz device 10 and the object 20 and / or the reference object 20' relative to each other in a given arrangement 150a; and determining reference data RD for the given arrangement 150b; and optionally, repeating the steps of arranging 150a and determining 150b until, for example, a predetermined termination criterion has been reached, wherein the arrangement 150a includes, for example, positioning devices PE, PE' ( Figure 9 The positioning devices PE and PE' are used to locate the terahertz device 10 and / or object 20 or reference object 20', such as robots.

[0120] In other exemplary embodiments, such as Figure 14 As shown, the method further includes determining, for example, using sensors (e.g., additional sensors) at least one of the following elements: a) distances L and AB between the terahertz device 10 and the object 20 or the reference object 20'; b) the angular orientation WA between the terahertz device 10 and the object 20 or the reference object 20', for example, in a one-dimensional arrangement (i.e., characterized by angle α) or a two-dimensional arrangement (characterized by angles α and β); c) the shape FO, such as curvature, of the surfaces 20a, 20a' / 20a' of the object 20 or the reference object 20'. In further exemplary embodiments, optical sensors (e.g., for laser distance measurement and / or laser angle measurement) and / or acoustic sensors (e.g., ultrasonic sensors) and / or sensors based on electromagnetic waves (e.g., radar sensors) may be used for the determination at 160.

[0121] In other exemplary embodiments, such as Figure 14 As shown, the method further includes using distance L, AB and / or angular orientation WA and / or shape FO of 162 for model MOD, for example, to determine the terms T and / or individual values ​​of terms T.

[0122] In other exemplary embodiments, such as Figure 15 As shown, the method further includes: determining 170 whether at least one region of interest, such as a reflection point GF (and / or all significant reflection points, i.e., all reflection points that provide a predefined minimum contribution to the measurement and / or the measurement result) is within a parameter range of values ​​T-1, T-2, T-3... of term T (e.g., characterizable by a range of distances and / or angles), and / or whether reference data RD, characterizable by a calculated and / or calibrated transmission function, is available; and, based on the determination 170, changing 172 the spatial arrangement, such as distances and / or angles, wherein, for example, the change 172 is repeated 173 until the region of interest is within the parameter range; and optionally, performing 174 an evaluation. In another exemplary embodiment, the evaluation 174 may also be performed to pre-calculate 140 ( Figure 12 To be carried out for the purpose of Figure 12 ).

[0123] Other exemplary embodiments, such as Figure 16 As shown, reference is made to a device 200 for performing the methods described according to these embodiments.

[0124] In another exemplary embodiment, the device 200 is provided to include a computing device (“computer”) 202 and a storage device 204 associated with the computing device 202, the storage device 204 being used to store at least temporarily at least one of the following elements: a) data DAT (e.g., data of a model MOD and / or at least a plurality of portions of a database DB). Figure 1 (a) b) Computer program PRG, particularly for performing the method according to the embodiments described.

[0125] In another preferred embodiment, the storage device 204 has volatile memory 204a (e.g., working memory (RAM)) and / or non-volatile memory 204b (e.g., flash EEPROM).

[0126] In another exemplary embodiment, computing device 202 has and / or is configured to be at least one of the following elements: microprocessor (μP), microcontroller (μC), application-specific integrated circuit (ASIC), system-on-chip (SoC), programmable logic device (e.g., field-programmable gate array, FPGA), hardware circuit, or any combination thereof.

[0127] Another exemplary embodiment relates to a machine-readable storage medium SM, the machine-readable storage medium SM including instructions PRG', which, when executed by a computer 202, cause the computer 202 to perform the method according to the embodiment.

[0128] Another exemplary embodiment relates to a computer program PRG that includes instructions that, when executed by a computer 202, cause the computer 202 to perform the method according to the embodiment.

[0129] Another exemplary embodiment relates to a data carrier signal (DCS) that represents and / or transmits a computer program (PRG) according to an embodiment. This data carrier signal (DCS) may be received, for example, via an optional data interface 206 of device 200.

[0130] In another exemplary embodiment, at least one positioning device PE, PE' can also be controlled via data interface 206.

[0131] like Figure 17As shown, further exemplary embodiments relate to a method and / or device according to an embodiment and / or machine-readable storage medium according to an embodiment and / or computer program according to an embodiment and / or data carrier signal according to an embodiment for at least one of the following elements: a) determining at least one characteristic of object 202, such as the layer thickness D-M2 of at least one layer 20-2 of object 20; b) enhancing the accuracy of model MOD 304, for example, by taking into account the non-planar propagation of terahertz radiation TS. For example, waves that are not entirely planar; c) considering the correlation between the 306 spectral transmission function and the distance L to the terahertz device 10 and / or the angular orientation between the terahertz device 10 and the object 20 and / or the shape and / or surface characteristics of the object 20; d) considering the dependence of the 306 spectral transmission function on the angles α, β relative to the terahertz device 10; e) considering the characteristics of the surface 20a of at least one object 20 or reference object 20', such as the shape FO of the surface 20a, 20a', and / or the roughness of the surface 20a, 20a'.

[0132] Figure 18 A simplified block diagram according to another exemplary embodiment is schematically shown. An arrangement is illustrated, such as a measuring object, having two paint layers 20-1, 20-2 coated on a substrate 20-3 (e.g., metal), and the arrangement is surrounded by an environmental medium UM such as air. Exemplary embodiments and aspects will be referenced below. Figure 18 The arrangement is described. For example, the incident plane wave and the outgoing plane wave of THz radiation are distinguished by the symbols "+" / "-".

[0133] In another exemplary embodiment, a model MOD ( Figure 1 Set one or more of the following additional parameters (related to the equations described herein):

[0134] · The frequency-dependent field strength of the THz pulse traveling in the opposite direction in the air during the nth iteration step.

[0135] · The frequency-dependent field strength of the reverse-running THz pulse in the first coating layer (“Layer 1”) 20-1 during the nth iteration step.

[0136] · The frequency-dependent field strength of the reverse-running THz pulse in the second coating layer (“Layer 2”) 20-2 in the nth iteration step.

[0137] · The frequency-dependent field strength of the THz pulse moving positively in the air UM during the nth iteration step.

[0138] · The frequency-dependent field strength of the THz pulse in the first coating layer 20-1 during the nth iteration step.

[0139] · The frequency-dependent field strength of the THz pulse in the positively running THz pulse in the second coating layer 20-2 during the nth iteration step.

[0140] ·r 12 Reflection coefficient at boundary layer 1 / layer 2

[0141] ·r 21 Reflection coefficient at boundary layer 2 / layer 1

[0142] ·t 12 Transmission coefficient at boundary layer 1 / layer 2

[0143] ·t 21 Transmission coefficient at boundary layer 2 / layer 1

[0144] ·r 2S Reflectance coefficient at boundary layer 2 / substrate 20-3

[0145] • D1: Layer thickness of layer 1 (layer 20-1)

[0146] • D2: Layer thickness of layer 2 (layer 20-2)

[0147] • R1: Reflectivity of layer 1

[0148] • R2: Reflectivity of layer 2

[0149] • n1, n1 is the refractive index of layer 1 and layer 2.

[0150] e1 and e2 are the extinction coefficients of layer 1 and layer 2, respectively.

[0151] In another exemplary embodiment, a model MOD ( Figure 1 It provides one or more of the following phase terms (e.g., as relevant parameters):

[0152] · Phase term running twice through layer 1

[0153] · Phase term running once through layer 1

[0154] · Phase terms that run twice through layer 2.

[0155] Since multiple reflections can be considered in other exemplary embodiments, an infinite number of terms can be generated, which, in other exemplary embodiments, are based on... Figure 18The arrangement generates and reaches the THz detectors 12, 12' ( Figure 6 electric field Constrained by consecutive rows, for example, it can be represented by the following equation:

[0156]

[0157] In another exemplary embodiment, the electric fields in layers 20-1, 20-2 (and optionally, in the ambient medium UM) associated with the propagating THz radiation are each defined by the corresponding row according to at least one of the following equations, or can be characterized by at least one of the equations:

[0158]

[0159] In another exemplary embodiment, the starting conditions are selected as follows:

[0160] · Entering electric field

[0161] ·

[0162] In another exemplary embodiment, the additional terms are defined as follows:

[0163] · (Only one incident THz pulse)

[0164] ·

[0165] ·

[0166] ·

[0167] ·

[0168] In another exemplary embodiment, the transfer function is determined as follows:

[0169] Reflected THz pulse The distance traveled in the air was taken into account, and measurements were also taken at layers 20-1 and 20-2, as well as reference measurements (see also...). Figure 6 The offset ΔD between the two is used for correction:

[0170]

[0171] In another exemplary embodiment, the reference measurement is as follows:

[0172]

[0173] To account for different distance (“z”) dependencies, in another exemplary embodiment, the term T described above and / or the term G (D, also known as the weighting factor (or geometric factor)) are inserted. 1, R1(n), D2, R2(n), ω, x, y, z, α, β). For this purpose, in another exemplary embodiment, a correction factor is provided for the outgoing light ray.

[0174] · (For example, there is only one incident THz pulse)

[0175] ·

[0176] ·

[0177] ·

[0178] ·

[0179] ·

[0180] For example, R1(n) and R2(n) characterize multiple reflections of THz radiation in layer 1 or layer 2. In another exemplary embodiment, for example, when calculating rows, these terms can be determined by the power of A(1) and A(2) in the corresponding terms.

[0181] In another exemplary embodiment, a generalization of the model MOD can be established and applied to "L-layer objects" (arrangements and / or measurement objects with multiple L layers), where F m,n The electric field representing the THz radiation of the m-th layer used in the n-th iteration step can be characterized, for example, by the following equation:

[0182] ·

[0183] ·

[0184] In other exemplary embodiments, the following special cases may be considered:

[0185] ·

[0186] ·

[0187] ·m=L(letzteSchicht)

[0188]

[0189] Starting conditions:

[0190] The input electric field, and all other terms are, for example, zero.

[0191] In other exemplary embodiments, the principles described in the embodiments can therefore also be applied to, for example, L-layer objects and / or models MOD, MOD-1, MOD-2 for L-layer objects.

Claims

1. A method for processing data (DAT) associated with a model (MOD) characterizing the propagation of terahertz (THz) radiation (TS) in a space region (RB) for detecting (302) at least one characteristic of an object (20), the space region (RB) having at least one terahertz device (10) and at least one object (20), the at least one terahertz device (10) for emitting and receiving the terahertz radiation (TS), the at least one object (20) being exposed to the terahertz radiation (TS), wherein, The method includes: Provide the model (MOD) described in (100); The propagation of the terahertz radiation (TS) described in (102) is characterized using the model (MOD) in the region of at least one interface (GF) between two adjacent media (M1, M2) within the space region (RB). The model (MOD) has a term (T) characterizing the terahertz radiation, which depends on at least one of the following elements: a) The frequency of the terahertz radiation (TS); b) The spatial extension (D) and / or position of at least one of the two adjacent media (M1, M2), The model (MOD) characterizes the multiple reflections (r0, r1, r2, r0', r1') and / or multiple transmissions (t0, t1, t0', t1') of the terahertz radiation (TS) at multiple interfaces (GF-1, GF-2) between two corresponding adjacent media (M1, M2) within the spatial region (RB) using a coherent superposition function. The term (T) is set as a weighting factor (G) for at least some components of the coherent superposition function.

2. The method according to claim 1, wherein, The Model (MOD) characterizes at least one reflection and / or at least one transmission of the terahertz radiation (TS) at at least one interface between two adjacent media, wherein the Model (MOD) characterizes multiple reflections and / or multiple transmissions of the terahertz radiation (TS) at at least two interfaces between various different media, wherein the term (T) characterizing the terahertz radiation (TS) has a different value for each of the at least two interfaces, wherein the term (T) is set as a weighting factor (G) in addition to the weighting factor (G) used for at least some components of the coherent superposition function.

3. The method according to claim 1, wherein, The model (MOD) has a first component (MOD-1) which is characterized by the terahertz radiation (TS) of a sample measurement of the object (20) in a reflective or transmissive arrangement, wherein the first component (MOD-1) is characterized in the frequency domain.

4. The method according to claim 3, wherein, For the aforementioned reflection arrangement, the first component (MOD-1) is characterized based on the following equation: Among them, F S (ω,x,y,z) represents the field strength of the sample signal, which is frequency-dependent, where ω represents the angular frequency associated with the frequency of the terahertz radiation (TS), where x represents the first spatial coordinate, where y represents the second spatial coordinate, where z represents the third spatial coordinate, where I0(ω,x,y,z) represents the field strength of the terahertz radiation (TS) at the transmitter (11) that generates the terahertz radiation (TS), which is frequency-dependent, where exp[] represents the exponential function, where i represents the imaginary unit, where c0 represents the speed of light in vacuum, where L represents the distance between the terahertz device (10) and the reference object (20'), where ΔD represents the offset between the reference object (20') and the object (20), where n A Characterizes the refractive index of the medium existing in the said spatial region (RB), where, ∈ A The extinction coefficient of the medium existing in the spatial region (RB) is characterized, wherein Φ0(ω,x,y,z) characterizes the phase of the terahertz radiation (TS) at the emitter (11) that generates the terahertz radiation (TS), the phase being frequency-dependent, wherein t A1 The transmittance coefficient characterizing the distance from the medium present in the spatial region (RB) to the interface of the first layer (20-1) characterizing the surface (20a) of the object (20), where t 1A The transmittance coefficient is defined as the coefficient of transmission from the first layer (20-1) of the surface (20a) of the object (20) to the interface of the medium existing in the spatial region (RB), where r 1S The reflection coefficient is characterized at the interface (GF-3) from the third layer (20-3) of the object (20) to the substrate (20-4), where R represents the reflectivity, which represents the quantity and / or sequence order of the reflection and / or transmission of the terahertz radiation (TS), where r 1A The reflection coefficient is characterized at the interface from the first layer (20-1) of the surface (20a) of the object (20) to the medium existing in the spatial region (RB), where G(D,R,ω,x,y,z,α,β,Ω) characterizes the term (T) characterizing the terahertz radiation (TS), where D characterizes the layer thickness, where n characterizes the refractive index of the layer, where ∈ characterizes the extinction coefficient of the layer, where r A1 The reflection coefficient is characterized at the interface from the medium present in the spatial region (RB) to the first layer (20-1) of the surface (20a) of the object (20), wherein α and / or β characterize the angular orientation of the terahertz device (10) relative to the object (20), wherein Ω characterizes the properties of the surface (20a) of the object (20), wherein the properties of the surface (20a) of the object (20) include at least one of the following elements: a) the shape of the surface (20a); b) the roughness of the surface (20a), wherein the first component (MOD-1) can be characterized based on the following equation: Among them, R max <∞, Among them, R max A finite value that can be predetermined to characterize the reflectivity.

5. The method according to claim 1, wherein, The model (MOD) has a second component (MOD-2) that is characterized by the terahertz radiation (TS) at a reference object (20') in a reflective or transmissive arrangement, wherein the second component (MOD-2) can be characterized in the frequency domain.

6. The method according to claim 5, wherein, For the aforementioned reflection arrangement, the second component (MOD-2) is characterized based on the following equation: Among them, F s (ω,x,y,z) represents the field strength of the reference signal, which is frequency-dependent, where ω represents the angular frequency associated with the frequency of the terahertz radiation (TS), where x represents the first spatial coordinate, where y represents the second spatial coordinate, where z represents the third spatial coordinate, where I0(ω,x,y,z) represents the field strength of the terahertz radiation (TS) at the transmitter (11) that generates the terahertz radiation (TS), which is frequency-dependent, where exp[] represents the exponential function, where i represents the imaginary unit, where c0 represents the speed of light in vacuum, where L represents the distance between the terahertz device (10) and the reference object (20'), where n A Characterizes the refractive index of the medium existing in the said spatial region (RB), where, ∈ A The extinction coefficient of the medium existing in the spatial region (RB) is characterized, wherein Φ0(ω,x,y,z) characterizes the phase of the terahertz radiation (TS) at the emitter (11) that generates the terahertz radiation (TS), the phase being frequency-dependent, wherein r AM The reflectance coefficient is characterized at the interface (GF-0') from the medium present in the space region (RB) to the surface (20a') of the reference object (20').

7. The method according to claim 1, wherein, The model (MOD) can be characterized in the frequency domain based on the following equation for the reflection arrangement: Wherein, H(ω) characterizes the transmission function of the terahertz radiation (TS), which is related to a reference measurement, and the model can be characterized in the frequency domain based on the following equation: Where exp[] represents the exponential function, where i represents the imaginary unit, where ω represents the angular frequency associated with the frequency of the terahertz radiation (TS), where c0 represents the speed of light in vacuum, where ΔD represents the offset between the reference object (20') and the object (20), where n A Characterizes the refractive index of the medium existing in the said spatial region (RB), where, ∈ A The extinction coefficient characterizing the medium present in the said spatial region (RB), where t A1 The transmittance coefficient characterizing the distance from the medium present in the spatial region (RB) to the interface of the first layer (20-1) characterizing the surface (20a) of the object (20), where t 1A The transmittance coefficient is defined as the coefficient of transmission from the first layer (20-1) of the surface (20a) of the object (20) to the interface of the medium existing in the spatial region (RB), where r 1S The reflection coefficient is characterized at the interface (GF-3) from the third layer (20-3) of the object (20) to the substrate (20-4), where R represents the reflectivity, which represents the quantity and / or sequence order of the reflection and / or transmission of the terahertz radiation (TS), where r 1A The reflection coefficient is characterized at the interface from the first layer (20-1) representing the surface (20a) of the object (20) to the medium present in the spatial region (RB), where G(D,R,ω,x,y,z,α,β,Ω) represents the term (T) characterizing the terahertz radiation (TS), where D characterizes the layer thickness, where x characterizes the first spatial coordinate, where y characterizes the second spatial coordinate, where z characterizes the third spatial coordinate, where α and / or β characterize the angular orientation of the terahertz device (10) relative to the object (20), where Ω characterizes the properties of the surface (20a) of the object (20), where n characterizes the refractive index of the layer, where ∈ characterizes the extinction coefficient of the layer, where r A1 The reflectance coefficient at the interface from the medium present in the spatial region (RB) to the first layer (20-1) representing the surface (20a) of the object (20), where r AM The reflectance coefficient at the interface (GF-0') from the medium present in the spatial region (RB) to the surface (20a') of the reference object (20') is characterized, wherein a predetermined finite value R of reflectance is used. max .

8. The method according to claim 1, wherein, In addition to the following: a) the frequency of the terahertz radiation (TS); and / or b) the spatial spread (D) and / or location of at least one of the two adjacent media (M1, M2), the item (T) depending on at least one of the following elements: c) reflectivity (R) characterizing the quantity and sequence order of the reflections (r0, r1, r2, r0', r1') and / or transmissions (t0, t1, t0', t1'); d) the angular orientation of the terahertz device (10) relative to the object (20) and / or the reference object (20'); e) the distance between the at least one terahertz device (10) and / or the at least one object (20); f) the characteristics of the surface (20a) of the at least one object (20), the characteristics being the shape of the surface (20a) and / or the roughness of the surface (20a).

9. The method according to claim 1, - Wherein, the model (MOD) models the distance-dependent spectral variation of the transmission function of the terahertz radiation (TS) as distance-dependent and / or depth-dependent attenuation and / or amplification by using the term (T) and / or the weighting factor (G); and / or -in, The model (MOD) models the angle-dependent spectral variation of the transmission function of the terahertz radiation (TS) as angle-dependent attenuation and / or amplification by using the term (T) and / or the weighting factor (G); and / or - wherein the model (MOD) models the spectral variation of the transmission function of the terahertz radiation (TS) based on at least one characteristic of the surface (20a) of the at least one object (20) by using the term (T) and / or the weighting factor (G).

10. The method according to claim 9, wherein, The at least one characteristic of the surface (20a) of the at least one object (20) is the shape of the surface (20a) and / or the roughness of the surface (20a).

11. The method according to claim 1, wherein, The model (MOD) comprises the object (20) having multiple layers (20-1, 20-2, 20-3, 20-4), the multiple layers (20-1, 20-2, 20-3, 20-4) being formed by different media (M1, M2, M3, M4), wherein the model (MOD) represents at least one of the following elements: a) The reflection and / or transmission of the terahertz radiation (TS) in the object (20); b) The terahertz radiation (TS) is reflected and / or transmitted multiple times in the object (20); c) Virtual reflection points and / or virtual transmission points in the object (20), wherein the virtual reflection points and / or the virtual transmission points can be characterized by reflectivity; d) Coherent superposition of the different reflections and / or transmissions of the terahertz radiation (TS) in the object (20).

12. The method according to claim 4, further comprising: The optical model (MOD-OPT) based on the system (SYS) determines (110) the item (T) and / or the individual values ​​(T-1, T-2, T-3...) of the item (T), the system (SYS) characterizing the terahertz device (10) and the object (20) and / or the reference object (20'), and the system (SYS) characterizing the ambient medium (UM) surrounding the terahertz device (10) and the object (20) or the reference object (20').

13. The method according to claim 12, wherein, The optical model (MOD-OPT) characterizes the spectral transmission function of the terahertz radiation (TS) within the system (SYS), and / or, wherein the optical model (MOD-OPT) characterizes the amplitude and phase of the spatial spread of the terahertz radiation (TS) within the system (SYS).

14. The method according to claim 12, wherein, The optical model (MOD-OPT) takes into account the diffraction effect of the terahertz radiation (TS).

15. The method of claim 12, further comprising: The optical model (MOD-OPT) is determined based on modeling by means of a) ray tracing (120a), and / or b) description based on diffraction theory (120b), by means of diffraction integral, and / or c) parameter calculation with modeling capabilities (120c). and The optical model (MOD-OPT) is calibrated (122), wherein the determination (120) and / or calibration (122) of the optical model (MOD-OPT) is performed by frequency-resolved techniques.

16. The method of claim 15, further comprising: The optical model (MOD-OPT) is based on at least one of the following elements relative to the spectral transmission function and / or spatial amplitude and / or phase calibration (122): a) The angles (α, β) between the optical axis (OA) of the terahertz device (10) and the surface normal (20a-n) of the object (20) or the reference object (20'); b) The distance (L) between the terahertz device (10) and the surface (20a) of the object (20) or the reference object (20'); c) Characteristics of the surface (20a) of the at least one object (20) and / or the surface (20a') of the reference object (20'); d) The frequency of the terahertz radiation (TS).

17. The method according to claim 16, wherein, The characteristic of the surface (20a) of the at least one object (20) and / or the surface (20a') of the reference object (20') is the roughness of the surface (20a, 20a').

18. The method of claim 15, further comprising: Change (130) the spatial positions of the reflection points (GF-0, GF-1, GF-2, ...) and / or transmission points (GF-0, GF-1, GF-2, ...) characterized by the model (MOD); Based on the change (130), the characteristics of at least one layer (20-2) of the object (20) formed by the medium (M2) are derived (132). At least one of the following elements is used in the derivation (132): a) Perform the relevant method (132a); b) Perform the method (132b) for pattern recognition; c) Identify the (132c) peaks and / or valleys; d) Using the (132d) machine learning method; e) Perform the (132e) fitting method.

19. The method of claim 12, further comprising: At least one component (MOD-1, MOD-2) and / or optical model (MOD-OPT) of the model (MOD) is determined by pre-calculation (140), and the result (VE) of the model (MOD) determined by pre-calculation (140) is stored (142) at least temporarily, wherein the result (VE) is stored in a database (DB).

20. The method of claim 15, further comprising: Determining (150) reference data (RD) for a plurality of different spatial arrangements of the terahertz device (10) and the object (20) and / or the reference object (20') relative to each other includes: arranging (150a) the terahertz device (10) and the object (20) and / or the reference object (20') relative to each other in a given arrangement; and Determine (150b) reference data (RD) for the given arrangement, and repeat (152) the steps of the arrangement (150a) and the determination (150b) until a predetermined termination criterion has been reached, wherein the arrangement (150a) includes positioning the terahertz device (10) and / or the object (20) or the reference object (20') by means of positioning devices (PE, PE').

21. The method of claim 15, further comprising: Use a sensor to determine at least one of the following elements (160): a) The distance (L, AB) between the terahertz device (10) and the object (20) or the reference object (20'); b) Angular orientation (WA) of the terahertz device (10) and the object (20) or the reference object (20') in a one-dimensional or two-dimensional arrangement; c) The shape (FO) of the surface (20a, 20a') of the object (20) or the reference object (20').

22. The method of claim 21, further comprising: Based on the shape (FO) of the surface (20a) of the at least one object (20) or the surface (20a') of the reference object (20a) and / or the roughness of the surface (20a, 20a'), the distance (AB) and / or the angular orientation (WA) and / or the characteristics of the surface (20a, 20a') are applied (162) to the model to determine the terms (T) and / or the individual values ​​of the terms (T) (T1, T2, T3...).

23. The method of claim 20, further comprising: Determine (170) whether at least one region of interest lies within a parameter range, wherein, for the parameter range, there exist values ​​for the term (T) (T-1, T-2, T-3…) and / or reference data (RD) that can be characterized by a calculated and / or calibrated transmission function; and Based on the determination (170), the spatial arrangement, distance and / or angle are changed (172), wherein the change (172) is repeated (173) until the region of interest is within the range of the parameters, and an evaluation is performed (174).

24. The use of the method according to claim 1 for at least one of the following elements: a) Determine at least one characteristic of the object (20) as described in (302); b) Enhance the accuracy of the model (MOD) by taking into account the propagation of the terahertz radiation (TS) in a non-planar manner; c) Consider the dependence of the (306) spectral transmission function on the distance (L, AB) to the terahertz device (10); d) Consider the dependence of the (310) spectral transmission function on the angle (α, β) relative to the terahertz device (10); e) Based on the shape (FO) of the surface (20a) of the at least one object (20) or the surface (20a') of the reference object (20') and / or the roughness of the surface (20a, 20a'), the characteristics of the surface (20a, 20a') are taken into consideration (308).

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