Electromagnetic jet thickness measurement device for an identified product during manufacturing

Abstract

The invention relates to a measuring device (100) that implements an inspection process for an identified product during its manufacture, characterized in that the measuring device uses an electromagnetic jet as a thickness measurement. The invention also relates to an inspection process for an identified product that is implemented by the disclosed measuring device (100). The invention further relates to a thickness measurement system for an identified product during its manufacture, comprising the disclosed measuring device (100) and a communication network that manages the data entering the system from the measuring device (100). The communication network incorporates one or more communication servers, each comprising one or more processors capable of executing programmed instructions stored in memory to implement the steps of the disclosed inspection process. Figure for the abstract: Fig. 4

Description

Title of the invention: Device for measuring thickness by electromagnetic jet of an identified product during manufacturing. Technical field

[0001] The invention relates to a device for measuring the thickness of an identified product during its manufacture. More particularly, the invention relates to a device for measuring thickness by electromagnetic jet with a sub-metric spatial resolution in industrial applications. Context

[0002] In industrial sectors, the measurement and characterization of materials are routinely carried out in manufacturing and testing workshops. In the context of their use, it is often necessary to find new technological approaches to accurately measure spatial distances and product layer thickness.

[0003] Several technologies have already been tested or developed to determine the thickness of a material (either a material to be removed or a material intended for inclusion in a product during manufacturing). For example, there are magnetic sensors that use eddy currents, but these do not allow for precise distance measurements because the thickness is averaged over the entire surface of the sensor (the deeper the penetration into the material, the larger the sensor must be). For a system using this type of technology, the spatial resolution is low (due to the size of the sensor), and therefore the system cannot handle significant curvature of an object.

[0004] Ultrasonic measurements also exist, which require a coupling to perform the measurement. Data interpretation is often difficult, and accuracy can be low.

[0005] In addition, there is thermography which requires direct heating (for example, by an infrared lamp) or indirect heating (for example, by induction) of the product being measured, which implies a significant consumption of energy.

[0006] There are also traditional wave sensors whose thickness measurement is carried out by Terahertz wave (for example, as disclosed by the Applicant's patent FR3117210).

[0007] Other optical-based technologies have been systematically ruled out since they do not penetrate opaque materials or penetrate them very little.

[0008] Among the measurement methods commonly used to characterize the properties of materials are waveguide and free-space techniques in the microwave range. Although these methods are reliable and efficient, they have some Disadvantages: Measurements in waveguides are destructive, and measurements in free space require a large, often flat, sample. Furthermore, the "traditional" systems that implement these long-established methods have characteristics directly dependent on the wavelength used, including: - A spatial resolution power dependent on the diffraction limit defined by the Rayleigh criterion, i.e. approximately X / 2. - A power of discrimination and characterization (e.g., thickness) of materials depending on the frequency band used: the wider the frequency band, the more precise the characterization. - Restricted penetration into materials, induced by the dispersion of the emission power on the wavefront.

[0009] To overcome these limitations, the electromagnetic jet concept was introduced as a method for local free-space characterization (see Ghaddar, Ali et al. “Electromagnetic Jet Towards Characterization Applications,” 17th Microwave and Materials Characterization Days, https: / / hal.science / hal-04059278 (April 2023) (“Ghaddar reference”). The electromagnetic jet is derived from the photonic jet concept where a dielectric sphere, illuminated by a near-field wave, can focus fundamentally into a beam whose width is narrower than the diffraction limit (see Ghaddar reference) (citing Chen, Zhigang and Taflove, Allen, “Photonic nanojet enhancement of backscattering of light by nanoparticles: a potential novel visible-light ultramicroscopy technique,” ​​Opt. Express, vol. 12, no. 7, p. 1214, doi: 10.1364 / OPEX. 12.001214 (2004) ("the Chen reference").Ghaddar observes that "this beam has a high intensity and propagates over several wavelengths in the form of a quasi-plane wave," and therefore the photonic jet has been widely studied and applied in industry and laboratory tools.

[0010] With reference to [Fig. 1] (which corresponds to [Fig. 1] of Ghaddar 1), an electromagnetic beam 10 is designed to study the electromagnetic response of a simple material composed of a substrate with a ground plane on the back face. The electromagnetic response of multilayer systems with different refractive indices can be treated analytically using Maxwell's equations (it is known that Maxwell's equations describe the propagation of electromagnetic waves in any type of medium).

[0011] By way of example, the electromagnetic jet 10 includes a horn antenna (or " antenna") 10a filled with polytetrafluoroethylene (or "PTFE"). The horn antenna 10a extends along a predetermined height H, which is defined between a predetermined minimum diameter d and a predetermined maximum diameter D. The horn antenna 10a is extended by a cylinder, which is also made of PTFE. This cylinder includes a cylindrical tip 10b of predetermined height h and predetermined radius R at the antenna outlet. The cylindrical tip 10b forms a transient part at the antenna input, minimizing reflections due to the change in medium (air / PTFE).

[0012] An electromagnetic wave encounters two different media at the exit of the horn antenna 10a: the cylindrical tip 10b of PTFE in the center, surrounded by air at the ends. The portion of the wave traveling in the air has a faster propagation speed than the portion of the wave propagating in the PTFE. The wavefront at the exit of the horn antenna has a concave shape, and the wave takes on a convex shape at the tip after passing through it (this deformation is explained by the difference in propagation speed between the air and the PTFE). Subsequently, Fonde refraction towards the air amplifies the convexity of the wave, resulting in a more intense spot at the tip 5 mm from its end. Thus, the difference in propagation speed between the air and the PTFE is the cause of the focusing phenomenon of the electromagnetic jet 10.The focused wave exhibits a significant field concentration and appears to be less distorted, to the point that it can be considered approximately planar.

[0013] It is understood that the cylindrical tip 10b of the electromagnetic jet 10 is not limited to the geometry shown in [Fig. 1]. For example, the cylindrical tip 10b could be replaced by two or more concentric cylinders, by an elongated rectangular tip, or by another geometry that functions as equivalent to the cylindrical tip 10a.

[0014] Thus, it is appreciated that there is good agreement between the response of a material detected by an electromagnetic beam such as that shown in [Fig. 1] and a theoretical response of that material when illuminated by a plane wave. By using this type of beam focused near or below the diffraction limit, the electromagnetic beam makes it possible to offer new measurement systems in industry, including in the microwave and terahertz ranges. This method, which performs localized measurements in free space without damage, has favorable characteristics, including, but not limited to: - Stronger penetration into carbonaceous materials compared to conventional methods; - Increased spatial accuracy (X / 10 minimum instead of X / 2 with conventional systems); - A very localized and homogeneous focus; - Very good detection and discrimination of materials; and - A possibility of characterizing metallic oxidation.

[0015] The electromagnetic jet concept has recently seen increasing progress due to its applications in detection and imaging, ranging from the optical domain to microwave frequencies. Thus, the disclosed invention employs an innovative electromagnetic jet device that enables near-field detection and / or measurement. Compared to conventional methods (such as the use of free-space plane waves or specific phenomena), the disclosed invention makes it possible to track transverse and longitudinal curvatures (for example, along the edges of inspected products) more closely as they evolve. Furthermore, the disclosed invention achieves the same measurement certainty while meeting requirements such as reasonable deployment costs, multi-material detection, and increased detectability. Summary of the invention

[0016] The invention relates to a thickness measuring device that is part of a system that implements a process for inspecting an identified product during its manufacture, characterized in that the measuring device comprises: - an electromagnetic jet comprising a horn antenna extending along a predetermined height defined between a predetermined minimum diameter and a predetermined maximum diameter, the horn antenna being extended by a cylinder comprising a cylindrical tip having a predetermined height and a predetermined radius at the antenna outlet; and - a means of generating signals in a predetermined frequency band, the emitted frequency band of which is chosen according to the properties of the identified product.

[0017] In one embodiment of the measuring device of the invention, the electromagnetic jet is made of polytetrafluoroethylene (PTFE).

[0018] In one embodiment of the measuring device of the invention, the measuring device further comprises a robot having a measuring peripheral supported by a pivoting elongated arm, the measuring peripheral extending from the elongated arm to a free end which allows the installation of the electromagnetic jet; so that the measuring device is fixed in such a way as to allow its rotation relative to the free end and also to allow its spinning around a predefined axis of rotation during the inspection process.

[0019] In one embodiment of the measuring device of the invention, the means for generating signals includes a synthesizer disposed at the free end of the measuring device.

[0020] In one embodiment of the measuring device of the invention, the frequency band emitted by the means of generating signals is between 20 and 40 GHz inclusive.

[0021] In one embodiment of the measuring device of the invention, the electromagnetic jet has a variable resolution depending on the contrast of the materials from X / 10 to X / 100.

[0022] The invention also relates to a system for measuring the thickness of an identified product during manufacturing, characterized in that the system comprises: - the disclosed measuring device; and - a communication network that manages the data entering the system from the measuring device, the communication network incorporating one or more communication servers each comprising one or more processors operationally connected to a memory configured to store an application for analyzing data representative of the identified products to be inspected, the processor(s) include an analysis application execution module which performs the data processing, of which the processor(s) are capable of executing programmed instructions stored in memory to implement the steps of the inspection process.

[0023] In one embodiment of the measurement system of the invention, the measurement system further comprises a vector network analyzer (VNA).

[0024] The invention further relates to a process for inspecting a product during production, the inspection process implemented by the disclosed measurement system, characterized in that the inspection process comprises the following steps: - a first step in which the measurement device of the system employs at least one method among: a frequency domain spectroscopy - cavity resonance (FDS-CR) method and a time domain spectroscopy - cavity resonance (TDS-CR) method, this step comprising a step of calculating a fast Fourier transform (FFT); - a second stage in which the reference spectrum is divided, such that: - or the wavelength is a submultiple of the thickness, the wave resonates exactly with the substrate, and the reflected signal of the wave is at its minimum; and - or the wavelength is not a submultiple of the thickness but a fraction thereof, the wave enters into constructive or destructive resonance; - a third step performing an Inverse Fourier Transform (iFFT) before specific signal processing, so that the signal processing is carried out in the time domain; - a fourth signal processing step including a thickness calculation according to the following expression: [Math 2] - e; represents the thickness of a layer i; - c represents the speed of light; - At represents the propagation delay between two interfaces representing an input interface and an output interface of layer i; and - n; represents the real part of the refractive index of the material in layer i; - and a final step of calculating a Fast Fourier Transform (FFT) on the cleaned signal; so that, at the end of the inspection process, the processed frequency transfer function is obtained.

[0025] In one embodiment of the inspection process of the invention, the fourth step of the inspection process comprises: - a step to obtain the refractive index of the identified product, where the refractive index is represented according to the following expression: [Math 3] n = ri + zn'where: n' represents the real part of the complex refractive index related to the wave propagation speed; and - n” represents the imaginary part of the complex refractive index related to the absorption of the wave; - and a step to determine the behavior of the wave through the materials it passes through, in which the angle of the refracted wave is governed by the following expression: [Math 4] ni sinj = n 2 sin 05; Or : - nor represents the refractive index of a first substrate; and - n2 represents the refractive index of a second substrate.

[0026] In one embodiment of the inspection process of the invention, the fourth step of the inspection process further includes a step to determine the refractive index of the identified products for a given frequency band according to the following expression:

[0027] [Math.5] _ c "i “ 2^Af Or : - ej represents the thickness of layer i; - c represents the speed of light; - Af represents the frequency difference between two successive resonances; and - n; represents the refractive index of the material in layer i.

[0028] In one embodiment of the inspection process of the invention, during the fourth stage of the inspection process, each interface in the time domain generates Gaussians which are discriminated in the form of the center of the Gaussians.

[0029] Other aspects of the invention will become evident from the following detailed description. Brief description of the drawings

[0030] The nature and various advantages of the invention will become more evident upon reading the following detailed description, together with the accompanying drawings, in which the same reference numbers designate identical parts throughout, and in which: [Fig.1] Fig.1 represents an embodiment of an electromagnetic jet used by the invention. [Fig.2] Fig.2 represents a schematic view demonstrating a link between A / and A / . [Fig.3] Fig.3 represents a schematic view of an electromagnetic wave and the link between its frequency and the round-trip propagation time. [Fig.4] Fig.4 represents an embodiment of a measuring device of the invention which implements a process for inspecting the product(s) identified during manufacturing. [Fig.5] Fig.5 represents a comparison of wavelength as a function of a horn antenna used. [Fig.6] Fig.6 represents a schematic view of a simulation in which the plane wave is focused at the output of the device. [Fig.7] Fig.7 represents a flow diagram of an inspection process implemented by the measuring device of the invention. [Fig.8] [Fig.9] Fig.8 and Fig.9 represent diopters representing interfaces between two layers of a substrate. [Fig. 10] The [Fig. 10] represents frequency resonance points that are strongly correlated with substrate thicknesses. [Fig.11] The [Fig. 11] represents a ratio between the refractive indices of the substrates. Detailed description

[0031] To understand the measurement system of the invention and the use of the electromagnetic jet, it is helpful to introduce the underlying theoretical study. It is understood that electromagnetic phenomena are represented using the electric field (E) and the magnetic field (H), which are two vector physical quantities. The intrinsic properties of a medium are represented by the electrical permittivity (ε), the electrical conductivity (μ₁), the magnetic permeability (μ), and the magnetic losses. (p”). Electrical conductivity and magnetic loss characterize the ability of a medium to absorb the electrical and magnetic energy of a wave propagating in that medium (see Gazave, Julien, “Contribution to the implementation of numerical simulation methods for the study of the vulnerability of electrical systems subjected to the radiative and electromagnetic environment of the Laser Mégajoule”, Thesis No. 70-2007, University of Limoges (2007)).

[0032] In the frequency domain, the inventors observed that the reflection coefficient exhibits an alternation of constructive and destructive resonances. Considering that the frequency difference A / between two successive resonances corresponds to the time A / for the wave to propagate back and forth in a substrate (i.e., a "medium"), [Fig. 2] represents a diagram to demonstrate this relationship between A / and A / . [Fig. 2] illustrates the penetration of an electromagnetic wave (or "EM wave") onto the upper surface of a substrate at time t, the arrival of the EM wave at the lower surface at time t + At / 2, and the return of the EM wave to the upper surface at time t + A / . The interference observed on the reflection spectrum corresponds to the result of the superposition of the incident wave and the wave that has returned to the upper surface after being reflected from the lower surface.

[0033] On this basis, the thickness of a sample can be detected from the reflection coefficient in the frequency domain. Figure 3 shows the diagram of an EM wave and the relationship between its frequency and the round-trip propagation time. The Fourier transform allows the signal to be converted from the time domain to the frequency domain (or vice versa): [Math 1] "z . G30 r " j^where the signal F(a') is the Fonde EM reflection coefficient measured in frequency sweep (w represents the frequency pulsation of Fonde EM).

[0034] To study this basic conversion from frequency domain to time domain, the inventors consider a signal representing the reflection coefficient of a substrate, calculated analytically from Maxwell's equations.

[0035] With further reference to the figures, in which the same numbers identify identical elements, [Fig. 4] represents an embodiment of a measuring device (or "device") 100 of the invention. The measuring device 100 can be part of an industrial system (or "system") in which an inspection process is carried out during the manufacture of one or more products. The measuring device 100 of the invention implements such an inspection process, enabling the measurement, by electromagnetic jet, of the thickness of a product (and / or a part of a product) during its manufacture.

[0036] In one embodiment of the measuring device 100 of the invention, the measuring device 100 comprises a robot having a measuring peripheral 102 supported by a pivoting elongated arm 104. The measuring peripheral 102 extends from the elongated arm 104 to a free end 102a, which allows for the attachment of an electromagnetic jet 106. The electromagnetic jet 106, being of the type shown in [Fig. 1], comprises a horn antenna 106a and a cylindrical tip 106b, both made of PTFE. The measuring device 106 is mounted in such a way as to allow its rotation relative to the free end 102a and also to allow its rotation around a predefined axis of rotation during an inspection process. By way of example, the electromagnetic jet 106 can be attached to the measuring peripheral 102 by screwing on an adapter.It is understood that the attachment of the electromagnetic jet 106 to the measuring device 102 can be achieved by one or more known attachment methods (including, without limitation, welding, bonding, and equivalent methods). Thus, the robot facilitates the inspection of a variety of products without interrupting the rotation and / or movement of the electromagnetic jet 106.

[0037] The measuring device 100 is set in motion so that the measuring device 102 can perform the inspection of an identified product to be inspected. The term "identified product" (in the singular or plural) is used here to refer to a manufactured product (and / or a product in the process of being manufactured) and present in the physical environment of the measuring device 100 (the physical environment being, for example, a manufacturing facility incorporating the measuring device 100).

[0038] It is understood that the configuration of the measuring device 100 is given by way of example. For example, the measuring device 100 may include a fixed robot installed on a manufacturing facility, attached, for example, to a support from which the robot extends (for example, a base not shown). In this case, it is understood that the robot may be attached to a ceiling, a wall, a floor, or any support that allows the inspection process to be carried out. It is understood that the measuring device 100 may include at least one mobile robot. By "mobile," it is understood that the measuring device may be set in motion either by integrated means of motion (for example, one or more integrated motors) or by non-integrated means of motion (for example, one or more mobile means, including autonomous mobile means).It is understood that the measuring device 100 can be a conventional industrial robot, a collaborative robot, or even a delta or cable robot.

[0039] Referring again to [Fig. 4], the measuring device 100 further comprises a means for generating signals in a predetermined frequency band. By way of example, the measuring device 100 comprises a synthesizer 108 arranged at the free end 102a of the measuring device 102. It is understood that the frequency band emitted by the synthesizer 108 is chosen according to the products intended for an inspection process. In one embodiment, the chosen frequency band is between 20 and 40 GHz.

[0040] The use of the electromagnetic jet 106 allows for precise control of the width and length of a plane wave pocket thanks to the design of a dielectric disruptor. Thus, the small width of the electromagnetic jet 106 (given the diameter of the cylindrical nozzle 106b) makes it possible to focus the measurement on a very small area. This property allows for a unique spatial resolution (as described below). Furthermore, the width of the electromagnetic jet 106 is "straight" and "stable" along the length of a useful inspection area, which makes the spatial resolution homogeneous over a distance of only a few wavelengths. The combination of these characteristics, as well as the refraction properties implemented by the electromagnetic jet 106, promotes the concentration of the plane wave intensity in the useful area. Once past the useful area, the wave diverges again in the form of spherical waves.The electromagnetic jet maintains a uniform focal width, thus ensuring consistent accuracy. Concentrating the wave intensity in the useful area allows for better penetration of absorbing materials.

[0041] Incorporating the electromagnetic jet allows the detection limit to be lowered below the conventional diffraction limit (being on the order of X / 2). Conventionally, the diffraction limit is based on calculations for standard optical systems. Most often, the Rayleigh criterion is used as a reference. This technique cannot be applied to the electromagnetic jet, so another means of comparison between different systems must be found. In this case, known methods are associated with the FWHM (or "Full Width at Half Maximum") of the main lobe of the Airy disk generated by the analyzed system.

[0042] To perform an inter-system comparison independently of wavelength (or operating frequency), a dimensionless ratio denoted d / X is used, where d is the FWHM width and X is the wavelength. By comparing different conventional systems (particularly, the empty horn antenna 5A and the horn antenna equipped with a Fresnel lens 5B) (see [Fig. 5]) with the electromagnetic jet (represented by the horn antenna with the cylindrical tip 5C) (see [Fig. 5]), it is found that the electromagnetic jet allows performance well below the equivalent characteristics compared to the conventional diffraction limit (as shown below in Table 1). [Tables 1] @30GHz, i.e., X = 0.00999m ~ 0.01m FWHM or d (in m) Ratio d / X Empty horn antenna 0.039 3.9 Horn antenna with Fresnel lens 0.012 1.2 Horn antenna with cylindrical tip 0.008 0.8

[0043] The electromagnetic jet has a variable resolution depending on the contrast of the materials from X / 10 to / . / 100.

[0044] As one might expect, the electromagnetic jet offers the possibility of using the generated plane waves, and consequently, all the common characterization methods associated with plane waves, as well as other methods more specific to the electromagnetic jet. Characterization by the electromagnetic jet is carried out in the useful zone of the jet; currently, it is restricted to the plane wave zone. Referring to [Fig. 6], a simulation is shown in which the plane wave is highly localized in a focused area at the exit of the perturbator (represented in the figure by the "plane wave pocket"). Within a material with a higher refractive index than air (for example, an eraser with n=3.15), the plane wave vector is very pronounced, and the waves are significantly plane. This zone forms the basis of all electromagnetic jet-based measurements.Thus, characterization is understood to mean the determination of one or more properties of a material or a complex structure of different kinds (for example, a multilayer product).

[0045] It is understood that frequency domain spectroscopy (FDS) and time domain spectroscopy (TDS) are used in all areas of electromagnetic spectroscopy. Consequently, these methods are also applicable to electromagnetic beam spectroscopy. The FDS method, having a long measurement rate, is usable over large thicknesses. The TDS method, having a fast measurement rate, is usable over small thicknesses.

[0046] With reference to [Fig. 7], and further to Figures 8 to 12, a detailed description is given by way of example of embodiments of an inspection process carried out by the measuring device 100 of the invention. It is understood that a system incorporating the measuring device 100 can implement the process in any physical environment without prior knowledge of the products to be inspected.

[0047] As used herein, the term “process” or “method” may include one or more steps performed by at least one computer system comprising one or more processors to execute instructions that perform the steps. Unless otherwise indicated On the contrary, any sequence of steps is given as an example and does not limit the processes described to any particular sequence.

[0048] By initiating an embodiment of the inspection process, the process includes a first step (see "Step 1" in [Fig. 7]) in which the measuring device 100 employs a frequency domain spectroscopy - cavity resonance (FDS-CR) method and / or a time domain spectroscopy - cavity resonance (TDS-CR) method. Each method is an additive treatment to the conventional FDS or TDS method, which uses standing waves to measure thickness. This approach is therefore based on the frequency domain, unlike conventional FDS and TDS methods, which use the time domain.Using the frequency domain increases the accuracy, dispersion, and stability of the measurement compared to the time domain approach, while having a restricted frequency band with a fine frequency step.

[0049] The first step of the inspection process includes a step of calculating a fast Fourier transform (or "FFT"). This calculation makes it possible to preserve the essential characteristics of the spectra while reducing the volume of calculations to be performed.

[0050] It is observed that when working with conventional TDS or FDS, the process for determining the thickness of a product remains the same, whether the sample or product to be inspected is single-layer or multi-layer. The resulting time transfer function of the FDS or TDS (output from a signal processing step of an inspection process implemented by the measuring device 100) (see Step 4 of [Fig. 7]) makes it possible to obtain the majority of the data necessary for calculating thickness in a metric quantity.

[0051] Referring again to [Fig. 7] and further to Figures 8 and 9, in the time domain, a diopter represents an interface between two layers 1 and 2. During the signal processing stage of an inspection process implemented by the measuring device, each interface (or diopter) (1, 2, 3) generates Gaussians which are discriminated in the form of the center of the Gaussians (or "peaks") (see peaks 1, 2, 3 in [Fig. 9]). Various techniques can be used to improve the detection of the Gaussians representing the diopters. This step also allows for improvement of the signal-to-noise ratio through various techniques (including, but not limited to, filtering, windowing, deconvolution, likelihood algorithms, and artificial intelligence on time series).

[0052] This approach is relevant in the case of a thickness measurement system with a conventional THz measuring machine whose frequency band is very wide (for example, 110-170 GHz or 220-330 GHz) and the measurement step is large (by (e.g., 151 measurements on this band). In contrast, electromagnetic jet technology allows the use of a vector network analyzer (or "VNA") with an extremely fine frequency step (around 1000 measurements on the band) to compensate for the narrow frequency band used (around 20-40 GHz).

[0053] During the use of the frequency domain in the first stage of the inspection process, the phenomenon of standing waves (and, more specifically, the constructive and destructive resonances that occur in a substrate during a frequency scan) allows for maximum utilization of the VNA capabilities (in fine frequency scanning) while minimizing the impact of the narrow usable frequency band with the electromagnetic beam (22-40 GHz). This data is supported by the SI reflection coefficient obtained from the analysis of the quadrupole (samples / substrate) using the VNA. This method uses the same basic principles as Fabry-Perrot interferometers. When the thickness of a substrate is precisely a fraction of a wavelength, the wave resonates with the substrate, and the resonance becomes destructive.During the frequency sweep at the measurement point, the wave penetrates the material and is reflected at each interface (or "diopter").

[0054] The inspection process includes a second step (see "Step 2" in [Fig. 7]) in which the reference spectrum is divided. Referring to [Fig. 10], if the wavelength is a submultiple of the thickness, the wave resonates exactly with the substrate, and the wave's return signal is at its minimum (low point). If the wavelength is not a submultiple of the thickness but a fraction thereof, the wave resonates constructively or destructively. Thus, the low points of the curve are the resonance points that correspond to the different frequencies where the wavelength in the substrate is "synchronized" with the substrate thickness.

[0055] It is difficult to directly use the frequency domain data from the second stage of the inspection process: they are noisy, thus requiring appropriate signal processing. Therefore, the inspection process includes a third stage (see "Step 3" in [Fig. 7]) of performing an Inverse Fourier Transform (or "iFFT") before specific signal processing (e.g., filtering, windowing, etc.). In this way, the desired signal processing is carried out, for practical reasons, in the time domain. Once the signal has been "cleaned up," it is necessary to return to the frequency domain to take full advantage of this method.

[0056] The inspection process includes a fourth step (see "Step 4" in [Fig. 7]) of signal processing of an inspection process implemented by the measuring device 100. This step includes a thickness calculation that is very similar to that of the time domain. However, this calculation involves a difference frequency A / instead of a time difference A / . The thickness of a layer is calculated as follows: [Math 2] "_: ei~ - ej represents the thickness of layer i; - c represents the speed of light; - At represents the time delay between two interfaces (where θ is the input interface and θ is the output interface of the layer); and - n; represents the real part of the refractive index of the material in layer i.

[0057] During this fourth step, to obtain the thickness calculation of a product to be inspected, its refractive index, which is a dimensionless value, must be obtained. In an absorbing medium, the refractive index is represented as a complex number: [Math 3] n = n'+m" where: n' represents the real part of the complex refractive index related to the wave propagation speed; and - n” represents the imaginary part of the complex refractive index related to the absorption of the wave.

[0058] The refractive index also allows us to determine the behavior of the wave through the materials it passes through, thanks to Snell's law. Referring to [Fig. 1 1], a substrate Medium 1 is defined by the refractive index nB and a substrate Medium 2 is defined by the refractive index n2. The reflected wave has the same angle as the incident wave, i.e., 0i=02. Thus, the angle of the refracted wave is governed by the following expression: [Math 4] ni sindj = n2 sind3.

[0059] It should be noted that if the incident wave is at the normal (vertical) to the Medium 2, it will be reflected on this same normal (and therefore will return to the same point). This is the most favorable case for thickness measurement. The system incorporating the measuring device 100 therefore uses a position at the normal to the product to be measured.

[0060] If the materials composing the layers of the products are previously characterized (i.e., the complex refractive index of the layers is known), the calculation remains simple and requires only a reflection measurement. It is therefore possible to determine the refractive index of the products for a given frequency band by creating charts on calibrated materials and using the thickness measurement equation adapted for determining the refractive index:

[0061] [Math.5] ni = 2^f Or : - e; represents the thickness of layer i; - c represents the speed of light; - Af represents the frequency difference between two successive resonances; and - n; represents the refractive index of the material of layer i.

[0062] The inspection process includes a final step (see "Step 5" in [Fig. 7]) in which a Fast Fourier Transform (or "FFT") calculation step is repeated on the cleaned signal. At the end of the inspection process (i.e., the "Output" in [Fig. 7]), the processed frequency transfer function is obtained.

[0063] With electromagnetic beaming, the frequency band is limited. However, it is possible to perform a large number of measurement points, and the signal can be cleaned up. In this way, the wave is modified to create an extremely high resolution region that distinguishes the details of the material from a substrate, thus enabling more precise material separation and / or characterization. By performing more measurement points, it becomes possible to detect and clean up the "peaks" to return to the time domain.

[0064] To properly manage the handling of the measuring device 100 (for example, the handling of the robot and the positioning of the electromagnetic jet 106 as shown in [Fig. 4]), the products being inspected must be identified. Thus, the detection data could refer to a plurality of representative recordings of the product positions tracked over time. For example, the detection data could include one or more positions from recordings of the positions of a reference point on a part of an inspected product over time or at defined time intervals; sensor data taken over time; a video stream that has been processed using a computer vision technique; and / or data indicating the operating status of the measuring device 100 over time.In some cases, the detection data may include representative data of one or more continuous movements of the measuring device 100 before it stops to inspect one or more products during an inspection process. The detection system could therefore be configured to generate the movement data of the measuring device 100.

[0065] To implement the computer-based inspection process, an industrial system incorporating the measuring device 100 may include a communication network (or "network") that manages the data entering the system from various sources (for example, from at least one measuring device 100). The network The communication system incorporates one or more communication servers (or "servers"), each comprising one or more processors operationally connected to memory. The memory is configured to store an application for analyzing data representative of the analyzed products. The processor(s) include an application execution module that performs data processing; the processor(s) are capable of executing programmed instructions stored in memory to implement the steps of the inspection process.

[0066] The input data of an industrial system incorporating the measuring device 100 may include general information concerning the inspected product. General information includes stored data concerning the identification of the analyzed product (including, without limitation, its production origin, its production date, the materials incorporated in its production, and its geometric parameters).

[0067] The inspection process may incorporate a machine learning method based on data obtained from the inspected product. The algorithm used analyzes the product to position and operate the measuring device 100. It is understood that such a process may be part of an existing manufacturing process. One or more neural networks (e.g., one or more CNNs) may be trained with ground truth data generated using sensor data representative of the movement of the measuring device 100, including the positioning of the measuring device 102 and the electromagnetic jet 106.

[0068] The industrial system incorporating the measuring device 100 of the invention (and / or an installation incorporating this system) may include pre-programmed management information. For example, an inspection process setting may be associated with the parameters of typical physical environments in which the system operates. In embodiments of the invention, the measuring device 100 (and / or an industrial system incorporating this device) may receive voice commands or other audio data representing, for example, an inspection start or stop. A request may be made that includes a request for the current status of an ongoing inspection cycle. A generated response may be represented audibly, visually, tactilely (for example, using a haptic interface), and / or virtually and / or augmented.This response, along with the corresponding data, can be recorded in a neural network.

[0069] For all embodiments of the system of the invention, a monitoring system could be implemented. At least part of the monitoring system can be provided in a portable device such as a mobile network device (for example, a mobile phone, a laptop computer, or one or more connected portable devices). to the network (including "augmented reality" and / or "virtual reality" devices), wearable clothing / jewelry connected to the network and / or any combinations and / or all equivalents). It is conceivable that detection and comparison steps could be carried out iteratively.

[0070] The terms "at least one" and "one or more" are used interchangeably. The ranges presented as being "between a and b" encompass the values ​​"a" and "b".

[0071] Although particular embodiments of the disclosed apparatus have been illustrated and described, it will be understood that various changes, additions, and modifications can be made without departing from the spirit or scope of this disclosure. Therefore, no limitations should be imposed on the scope of the invention described except those set forth in the appended claims.

Claims

Demands

1. A thickness measuring device (100) that is part of a system that implements a process for inspecting an identified product during its manufacture, characterized in that the measuring device (100) comprises: - an electromagnetic jet (106) including a horn antenna (106a) that extends along a predetermined height (H) defined between a predetermined minimum diameter (d) and a predetermined maximum diameter (D), the horn antenna (106a) being extended by a cylinder including a cylindrical tip (106b) having a predetermined height (A) and a predetermined radius (R) at the exit of the antenna; and - a means of generating signals in a predetermined frequency band, the emitted frequency band of which is chosen according to the properties of the identified product.

2. The measuring device (100) of claim 1, wherein the electromagnetic jet (106) is made of polytetrafluoroethylene (PTFE).

3. The measuring device (100) of claim 1 or claim 2, further comprising a robot having a measuring device (102) supported by a pivoting extended arm (104), the measuring device (102) extending from the extended arm (104) to a free end (102a) which allows the installation of the electromagnetic jet (106); such that the attachment of the electromagnetic jet (106) is made in such a way as to allow its rotation relative to the free end (102a) and also to allow its spinning around a predefined axis of rotation during the inspection process.

4. The measuring device (100) of claim 3, wherein the means for generating signals comprises a synthesizer (108) disposed at the free end (102a) of the measuring device (102).

5. The measuring device (100) of any one of claims 1 to 4, wherein the frequency band emitted by the means for generating signals is between 20 and 40 GHz inclusive.

6. The measuring device (100) of any one of claims 1 to 5, wherein the electromagnetic jet has a resolution that varies depending on the contrast of the materials from X / 10 to / . / 100.

7. A thickness measurement system for an identified product during manufacturing, characterized in that the system comprises: - the measuring device (100) of any one of claims 1 to 6; and - a communication network that manages the data entering the system from the measuring device (100), the communication network incorporating one or more communication servers, each comprising one or more processors operationally connected to a memory configured to store an application for analyzing data representative of the identified products to be inspected, the processor(s) comprising an analysis application execution module that performs the data processing, the processor(s) of which are capable of executing programmed instructions stored in memory to implement the steps of the inspection process.

8. The measurement system of claim 7, further comprising a vector network analyzer (VNA).

9. A process for inspecting a product during production, the inspection process implemented by the system of claim 7 or claim 8, characterized in that the inspection process comprises the following steps: - a first step in which the measuring device (100) of the system employs at least one method from among: a frequency-domain spectroscopy-cavity resonance (FDS-CR) method and a time-domain spectroscopy-cavity resonance (TDS-CR) method, this step comprising a step for calculating a fast Fourier transform (FFT); - a second step in which the reference spectrum is divided, such that: - either the wavelength is a submultiple of the thickness, the wave enters into exact resonance with the substrate, and the reflected signal of the wave is at its minimum;and - or the wavelength is not a submultiple of the thickness but a fraction thereof, the wave enters constructive or destructive resonance; - a third step performing an Inverse Fourier Transform (iFFT) before specific signal processing, so that the signal processing is carried out in the time domain; - a fourth signal processing step including a thickness calculation according to the following expression: [Math 2] ei~ 2^ - ej represents the thickness of a layer i; - c represents the speed of light; - At represents the propagation delay between two diopters representing an input interface and an output interface of layer i; and - n; represents the real part of the refractive index of the material of layer i; - and a final step of calculating a Fast Fourier Transform (FFT) on the cleaned signal; so that, at the end of the inspection process, the processed frequency transfer function is obtained.

10. The inspection process of claim 9, wherein the fourth step of the inspection process comprises: - a step to obtain the refractive index of the identified product, where the refractive index is represented according to the following expression: [Math 3] n = n'+zn' where: n' represents the real part of the complex refractive index related to the wave propagation speed; and - n” represents the imaginary part of the complex refractive index related to the wave absorption; - and a step of determining the behavior of the wave through the materials it passes through, wherein the angle of the refracted wave is governed by the following expression: [Math 4] ni sinj = n 2 sin 05; where: - ni represents the refractive index of a first substrate; and - n2 represents the refractive index of a second substrate.

11. The inspection process of claim 10, wherein the fourth step of the inspection process further comprises a step for determining the refractive index of the identified products for a given frequency band according to the following expression: [Math 5] n- = Where: 2e;At - ej represents the thickness of layer i; - c represents the speed of light; - Af represents the frequency difference between two successive resonances; and - n; represents the real part of the refractive index of the material of layer i.

12. The inspection process of any one of claims 9 to 11, wherein, during the fourth stage of the inspection process, each interface (1,2,3) in the time domain generates Gaussians which are discriminated in the form of the center of the Gaussians.

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