Device for measuring, by means of an electromagnetic jet, the thickness of a product identified during manufacture

Abstract

The invention relates to a measuring device (100) which implements a process for inspecting a product identified during the manufacture thereof, characterized in that the measuring device uses an electromagnetic jet to measure the thickness. The invention also relates to a process for inspecting an identified product which is implemented by the disclosed measuring device (100). The invention further relates to a system for measuring the thickness of a product identified during manufacture, which system comprises the disclosed measuring device (100) and a communication network which manages the data incoming to the system from the measuring device (100). The communication network incorporates one or more communication servers each comprising one or more processors that are capable of executing programmed instructions stored in a memory in order to implement the steps of the disclosed inspection process.

Description

[0001] Description

[0002] Electromagnetic jet thickness measurement device for an identified product during manufacturing

[0003] Technical Field

[0004] The invention relates to a device for measuring the thickness of an identified product during manufacturing. More particularly, the invention relates to a thickness measurement device using an electromagnetic jet with a sub-metric spatial resolution for industrial applications.

[0005] Context

[0006] In industrial sectors, the measurement and characterization of materials are routinely performed in manufacturing and quality control 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.

[0007] Several technologies have already been tested or developed to determine the thickness of a material (either material to be removed or material intended for inclusion in a product during manufacturing). For example, there are magnetic sensors that use eddy currents, but these do not provide a precise distance measurement 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 sensor size), and therefore the system cannot handle objects with significant curvature.

[0008] Ultrasonic measurements also exist, which require a coupling to perform the measurement. Data interpretation is often difficult, and accuracy can be low.

[0009] In addition, there is thermography which requires direct heating (e.g., by an infrared lamp) or indirect heating (e.g., by induction) of the product being measured, which implies a significant consumption of energy.

[0010] There are also traditional wave sensors whose thickness is measured using terahertz waves (for example, as disclosed in the Applicant's patent FR3117210). Other optical-based technologies have been systematically ruled out since they have little or no penetration into opaque materials.

[0011] Among the measurement methods commonly used to characterize material properties are waveguide and free-space techniques in the microwave range. While these methods are reliable and efficient, they have drawbacks: waveguide measurements are destructive, and free-space measurements require a large, often flat, sample. Furthermore, the long-established "traditional" systems that implement these methods have characteristics directly dependent on the wavelength used, including:

[0012] A spatial resolution power dependent on the diffraction limit defined by the Rayleigh criterion, i.e. approximately X / 2.

[0013] The ability to discriminate and characterize (e.g., thickness) materials depends on the frequency band used: the wider the frequency band, the more precise the characterization.

[0014] Restricted penetration into materials, induced by the dispersion of emission power on the wavefront.

[0015] 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 the wave 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.

[0016] Referring to Figure 1 (which corresponds to Figure 1 of Ghaddar 1), an electromagnetic beam 10 is designed to study the electromagnetic response of a simple material consisting of a substrate with a ground plane on its back face. The electromagnetic response of multilayer systems with different refractive indices can be treated analytically using Maxwell's equations (Maxwell's equations are known to describe the propagation of electromagnetic waves in any type of medium). As an example, the electromagnetic beam 10 includes a horn antenna (or "antenna") 10a made of 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 with a predetermined height h and a predetermined radius R at the antenna outlet. The cylindrical tip 10b forms a transitional section at the antenna inlet, minimizing reflections due to the change in medium (air / PTFE).

[0017] 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 wavefront traveling through the air has a faster propagation speed than the portion of the wavefront traveling through the PTFE. The wavefront at the exit of the horn antenna has a concave shape, and the wavefront becomes convex at the tip after passing through it (this deformation is explained by the difference in propagation speed between the air and the PTFE). Subsequently, the refraction of the wavefront into the air amplifies the convexity of the wavefront, resulting in a more intense spot 5 mm from the tip. 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.

[0018] It is understood that the cylindrical tip 10b of the electromagnetic beam 10 is not limited to the geometry shown in Figure 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 an equivalent to the cylindrical tip 10a. Thus, it is appreciated that there is good agreement between the response of a material detected by an electromagnetic beam like the one shown in Figure 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: Strong penetration into carbonaceous materials compared to conventional methods;

[0019] Increased spatial accuracy (X / 10 minimum instead of X / 2 with conventional systems);

[0020] A very localized and homogeneous focus;

[0021] Excellent detection and discrimination of materials; and the ability to characterize metallic oxidation.

[0022] The electromagnetic jet concept has recently seen increasing advancements due to its applications in detection and imaging, ranging from the optical domain to microwave frequencies. 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 allows for tracking transverse and longitudinal curvatures (e.g., along the edges of inspected products) more closely in their evolution. Furthermore, the disclosed invention achieves the same measurement certainty while meeting requirements such as reasonable deployment costs, multi-material detection, and enhanced detectability.

[0023] Summary of the invention

[0024] The invention relates to a thickness measuring device that forms part of a system implementing an inspection process for an identified product during its manufacture, characterized in that the measuring device comprises: an electromagnetic beam device including 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 including a cylindrical tip having a predetermined height and a predetermined radius at the antenna's exit; and a means for generating signals in a predetermined frequency band, the emitted frequency band of which is chosen according to the properties of the identified product. The measuring device is configured to implement the following steps of the inspection process:

[0025] - a first step in which the system measurement device uses at least one method among: a spectroscopy method in the frequency domain - cavity resonance or a spectroscopy method in the time domain - cavity resonance followed by a step of calculating a fast Fourier transform;

[0026] - a second stage in which the reference spectrum is divided by a reference spectrum;

[0027] - a third step performing an Inverse Fourier Transform before specific signal processing to denoise the data from the Inverse Fourier Transform, so that the specific signal processing is carried out in the time domain;

[0028] - a fourth signal processing step including a thickness calculation according to the following expression: cAt

[0029] Ci = 2n tei represents the thickness of a layer i; c represents the speed of light;

[0030] At represents the propagation delay between two diopters representing an input interface and an output interface of layer i; and m represents the real part of the refractive index of the material of layer i; and a final step of calculating a fast Fourier transform done on the signal obtained after the specific processing of the third step; so that, at the end of the inspection process, the processed frequency transfer function is obtained.

[0031] In one embodiment of the measuring device of the invention, the electromagnetic jet is made of polytetrafluoroethylene (PTFE).

[0032] In one embodiment of the measuring device of the invention, the measuring device further comprises a robot having a measuring device supported by a pivoting elongated arm, the measuring device extending from the elongated arm to a free end which allows the installation of the electromagnetic jet; so that the attachment of the electromagnetic jet device is made 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.

[0033] In one embodiment of the measuring device of the invention, the means for generating signals comprises a synthesizer disposed at the free end of the measuring device. In one embodiment of the measuring device of the invention, the frequency band emitted by the means for generating signals is between 20 and 40 GHz inclusive.

[0034] 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 / l 0 to X / 100.

[0035] 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) comprising an analysis application execution module configured to perform data processing, the processor(s) of which are configured to execute programmed instructions stored in memory which, when executed by the processor(s), cause them to implement the first, second, third, and fourth signal processing steps and the final calculation step.

[0036] In one embodiment of the measurement system of the invention, the measurement system further comprises a vector network analyzer (VNA).

[0037] The invention further relates to a process for inspecting a product during production, the inspection process being 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 or a time domain spectroscopy - cavity resonance (TDS-CR) method followed by a step of calculating a fast Fourier transform (FFT); a second step in which the reference spectrum is divided by a reference spectrum, a third step performing an Inverse Fourier Transform (iFFT) before specific signal processing to denoise data from the Inverse Fourier Transform (iFFT), so that the specific signal processing is carried out in the time domain;a fourth signal processing step including a thickness calculation according to the following expression: cAt;

[0038] Ci = 2n t

[0039] Where: ei represents the thickness of a layer i; c represents the speed of light;

[0040] At represents the propagation delay between two diopters representing an input interface and an output interface of layer i; and m represents the real part of the refractive index of the material of layer i; and a final step involving the calculation of a Fast Fourier Transform (FFT) made on the signal obtained after the specific processing of the third step; so that, at the end of the inspection process, the processed frequency transfer function is obtained.

[0041] 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: n = n' + in" where: n' represents the real part of the complex refractive index related to the propagation speed of Fonde; and n'' represents the imaginary part of the complex refractive index related to the absorption of Fonde; and a step to determine the behavior of Fonde through the materials it passes through, in which the angle of refracted Fonde is governed by the following expression: ni sin6i = n2 sin O3 where: ni represents the refractive index of a first substrate; and n2 represents the refractive index of a second substrate;

[0042] - 9i is an angle of incidence of the incident wave, 62 is an angle of reflection of the reflected wave and 63 is an angle of refraction of the refracted wave.

[0043] 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:

[0044] Where: ei represents the thickness of layer i; c represents the speed of light;

[0045] Af represents the frequency difference between two successive resonances; and m represents the real part of the refractive index of the material in layer i.

[0046] In one embodiment of the inspection process of the invention, each resonance of the two successive resonances is an exact resonance.

[0047] When the wavelength of the wave penetrating layer i is a submultiple of the thickness ei of layer i, the wave enters into exact resonance with layer i or substrate.

[0048] 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.

[0049] Other aspects of the invention will become evident from the following detailed description.

[0050] Brief description of the drawings

[0051] The nature and various advantages of the invention will become more evident upon reading the detailed description that follows, together with the accompanying drawings, on which the same reference numbers designate identical parts throughout, and in which: [Fig 1] Figure 1 represents an embodiment of an electromagnetic jet employed by the invention.

[0052] [Fig 2] Figure 2 represents a schematic view demonstrating a link between A / and At.

[0053] [Fig 3] Figure 3 represents a schematic view of an electromagnetic wave and the relationship between its frequency and the round-trip propagation time.

[0054] [Fig 4] Figure 4 represents an embodiment of a measuring device of the invention which implements a process for inspecting the product(s) identified during manufacturing.

[0055] [Fig 5A], [Fig 5B], [Fig 5C] Figures 5A, 5B, 5C represent a comparison of the spatial resolution obtained during detection according to different examples of a horn antenna.

[0056] [Fig 6] Figure 6 represents a schematic view of a simulation in which the plane background is focused at the output of the device.

[0057] [Fig 7] Figure 7 represents a flow diagram of an inspection process implemented by the measuring device of the invention.

[0058] [Fig 8] [Fig 9] Figure 8 and Figure 9 represent diopters representing interfaces between two layers of a substrate.

[0059] [Fig 10] Figure 10 represents frequency resonance points that are strongly correlated with substrate thicknesses.

[0060] [Fig H] Figure 11 represents a ratio between the refractive indices of the substrates.

[0061] Detailed description

[0062] To understand the measurement system of the invention and the use of the electromagnetic jet, it is helpful to introduce the basic theoretical framework. 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 (s), the electrical conductivity ( <J), la perméabilité magnétique (p) et les pertes magnétiques (p”). La conductivité électrique et la perte magnétique caractérisent la capacité d’un milieu à absorber l’énergie électrique et magnétique d’une onde se propageant dans ce milieu (voir Gazave, Julien, « Contribution à la mise en œuvre de moyens de simulation numérique pour l’étude de la vulnérabilité des systèmes électriques soumis à l’environnement radiatif et électromagnétique du Laser Mégajoule », Thèse N° 70-2007, Université de Limoges (2007)).

[0063] 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 Δt for the wave to propagate back and forth within a substrate (i.e., a "medium"), Figure 2 illustrates this relationship between A / and A / . Figure 2 depicts the penetration of an electromagnetic wave (or "EM wave") onto the upper surface of a substrate at time t, the arrival of EM waves at the lower surface at time t + Δt / 2, and the return of EM waves to the upper surface at time t + A / . The interference observed in the reflection spectrum corresponds to the result of the superposition of incident waves and waves that have returned to the upper surface after being reflected from the lower surface.Based on this, 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). where the signal F(m) is the Fonde EM reflection coefficient measured by frequency sweep (m represents the Fonde EM frequency pulsation).

[0064] 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.

[0065] Referring again to the figures, in which the same numbers identify identical elements, Figure 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 300 (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.

[0066] 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 installation of an electromagnetic jet device 106. The electromagnetic jet device 106, being of the type shown in Figure 1, comprises a horn antenna 106a and a cylindrical tip 106b, both made of PTFE. The electromagnetic jet 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 device 106 can be attached to the measuring peripheral 102 by screwing on an adapter.It is understood that the electromagnetic jet device 106 can be attached to the measuring device 102 by one or more known fastening methods (including, but not limited to, welding, bonding, and equivalent methods). Thus, the robot facilitates the inspection of a variety of products without interrupting the rotation and / or spinning of the electromagnetic jet device 106.

[0067] 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 an individual 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).

[0068] It is understood that the configuration of measuring device 100 is given by way of example. For example, measuring device 100 may include a fixed robot installed in a manufacturing facility, attached, for example, to a support from which the robot extends (e.g., 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 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 (e.g., one or more integrated motors) or by non-integrated means of motion (e.g., 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. Referring again to Figure 4, the measuring device 100 further includes a means for generating signals in a predetermined frequency band. For example, the measuring device 100 includes a synthesizer 108 located at the free end 102a of the measuring peripheral 102. It is understood that the frequency band emitted by the synthesizer 108 is chosen according to the products intended for inspection. In one embodiment, the chosen frequency band is between 20 and 40 GHz. The use of the electromagnetic jet device 106 allows for precise control of the width and length of a plane wave pocket through the design of a dielectric disruptor.Thus, the narrow width of the electromagnetic jet emitted by the electromagnetic jet device 106 (given the diameter of the cylindrical nozzle 106b) allows the measurement to be focused on a very small area. This property enables 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, resulting in homogeneous spatial resolution over a distance of only a few wavelengths. The combination of these characteristics, along with the refractive properties of the electromagnetic jet, promotes the concentration of the plane wave intensity within the useful area. Once past the useful area, the wave diverges again as 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.

[0069] Incorporating the electromagnetic jet allows the detection limit to be lowered below the conventional diffraction limit (which is 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 method of comparison between different systems must be found. In this case, known methods are available that are associated with the full width at half maximum (FWHM) of the main lobe of the Airy disk generated by the analyzed system.

[0070] To perform an inter-system comparison independently of wavelength (or operating frequency), a dimensionless ratio called d / X is used, where d is the FWHM width and Φ is the wavelength. By comparing different conventional systems, particularly the empty horn antenna shown in Figure 5A and the horn antenna equipped with a Fresnel lens shown in Figure 5B, with the example of the electromagnetic jet device 106 represented by the horn antenna with the cylindrical tip shown in Figure 5C, it is observed that the electromagnetic jet allows performance well below the equivalent characteristics compared to the conventional diffraction limit (as shown below in Table 1).

[0071] [Table 1]

[0072] The electromagnetic jet has a variable resolution depending on the contrast of the materials from l0 to X / lOO.

[0073] As one might expect, the electromagnetic jet offers the possibility of utilizing 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. Electromagnetic jet characterization is performed within the jet's useful region; currently, it is restricted to the plane wave region. Referring to Figure 6, a simulation is shown in which the plane wave is highly localized in a focused area at the perturbator's output (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 region forms the basis of all electromagnetic jet-based measurements.Thus, characterization is understood as the determination of one or more properties of a material or complex structure of different kinds (for example, a multilayer product).

[0074] It is understood that frequency domain spectroscopy (FDS) and time domain spectroscopy (TDS) are used in all areas of electromagnetic spectroscopy. Therefore, these methods are also applicable to electromagnetic beam spectroscopy. The FDS method, with its extended measurement time, is suitable for thick layers. The TDS method, with its rapid measurement time, is suitable for thin layers.

[0075] With reference to Figure 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 300 incorporating the measuring device 100 can implement the process in any physical environment without prior knowledge of the products to be inspected.

[0076] As used here, the term “process” or “procedure” 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 specified, any sequence of steps is given as an example and does not restrict the processes described to any particular sequence.

[0077] By initiating an implementation of the inspection process, the process includes a first step (see "Step 1" in Figure 7) in which the measuring device 100 employs either a frequency domain spectroscopy-cavity resonance (FDS-CR) 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.

[0078] The first step in the inspection process involves calculating a Fast Fourier Transform (FFT). This calculation preserves the essential characteristics of the spectra while reducing the amount of computation required. When implementing the FDS-CR method, this Fast Fourier Transform calculation step is not necessary.

[0079] In the case of implementing the TDS-CR method, the calculation of a fast Fourier transform is required. It is observed that when working with conventional TDS or FDS, the process of determining the thickness of a product remains the same, regardless of whether the sample or product to be inspected is single-layer or multi-layer. The resulting time transfer function of the FDS or TDS (from a signal processing step of an inspection process implemented by measuring device 100) (see Step 4 of Figure 7) provides most of the data necessary for calculating thickness in metric units.

[0080] Referring again to Figure 7 and further to Figures 8 and 9, in the time domain, a diopter represents an interface between two layers 11 and 12. During the signal processing stage of an inspection process implemented by the measurement device, each interface (or diopter) (1, 2, 3) generates Gaussians that are discriminated as the center of the Gaussians (or "peaks") (see peaks 1, 2, 3 in Figure 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).

[0081] This approach is relevant for a thickness measurement system using a conventional THz measuring machine with a very wide frequency band (e.g., 110–170 GHz or 220–330 GHz) and a large measurement step (e.g., 151 measurements in 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 in the band) to compensate for the narrow frequency band used (around 20–40 GHz).

[0082] 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 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 SI1 reflection coefficient obtained from the quadrupole (samples / substrate) analysis 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 scan at the measurement point, the wave penetrates the material and is reflected at each interface (or "diopter").The inspection process includes a second step (see "Step 2" in Figure 7) in which the reference spectrum is divided. More specifically, the spectrum resulting from Step 1 is divided by the reference spectrum representative of a calibration spectrum of the device 100 in order to account for measurement errors inherent to the device 100, generated, for example, by the attenuation of connector signals or interference generated by the environment of the device 100.

[0083] Referring to Figure 10, if the wavelength is a submultiple of the thickness, Fonde resonates exactly with the substrate, and the wave's return signal is at its minimum (low point). If the Fonde wavelength is not a submultiple of the thickness but a fraction of it, Fonde 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; Fonde is stationary.

[0084] It is difficult to directly use the frequency-domain data from the second stage of the inspection process: it is noisy and therefore requires appropriate signal processing. Thus, the inspection process includes a third stage (see "Stage 3" in Figure 7) of performing an Inverse Fourier Transform (or "iFFT") before specific signal processing to denoise the iFFT data (e.g., by filtering, windowing, etc.). More precisely, the specific signal processing includes denoising (e.g., by filtering, windowing, etc.) the iFFT data. In this way, the desired signal processing is carried out for practical reasons in the time domain. More precisely, the desired signal processing includes the iFFT and the specific signal processing.Once the signal has been "cleaned" or denoised, it is necessary to return to the frequency domain to take full advantage of this method.

[0085] The inspection process includes a fourth step (see "Step 4" in Figure 7) for 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 frequency difference A / instead of a time difference At. The thickness of a layer is calculated as follows: cAt C i = 2n t

[0086] Where: ei represents the thickness of layer i; c represents the speed of light;

[0087] At represents the time delay between two diopters (being the input interface and the output interface of the layer); and m represents the real part of the refractive index of the material of layer i.

[0088] During this fourth step, to calculate the thickness 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: n = n' + in" 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.

[0089] 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 Figure 11, a substrate Medium 1 is defined by the refractive index ni, 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., θi = θ2. Thus, the angle of the refracted wave is governed by the following expression: ni sin θi = n2 sin θ3.

[0090] More specifically, 0i is an angle of incidence of the incident wave, 02 is an angle of reflection of the reflected wave and 03 is an angle of refraction of the refracted wave.

[0091] It should be noted that if the incident wave is perpendicular (vertical) to Medium 2, it will be reflected along this same normal (and therefore return to the same point). This is the most favorable case for thickness measurement. System 300, incorporating measuring device 100, therefore uses a position perpendicular to the product being measured.

[0092] If the materials composing the product layers are previously characterized (i.e., the complex refractive index of the layers is known), the calculation remains simple and only requires 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.

[0093] Where: ei represents the thickness of layer i; c represents the speed of light;

[0094] Af represents the frequency difference between two successive resonances; and m represents the refractive index of the material in layer i, more precisely the real part of the refractive index of the material in layer i.

[0095] The inspection process includes a final step (see "Step 5" in Figure 7) in which a Fast Fourier Transform (FFT) calculation is repeated on the cleaned or denoised signal obtained after the specific processing of the third step. At the end of the inspection process (i.e., the "Output" in Figure 7), the processed frequency transfer function is obtained.

[0096] With electromagnetic beam technology, the frequency band is limited. However, it is possible to perform a large number of measurement points and clean up the signal. In this way, Fonde is modified to create an extremely high-resolution region that distinguishes the details of a substrate's material, enabling more precise material separation and / or characterization. By performing more measurement points, it becomes possible to detect and clean up "peaks" and return to the time domain.

[0097] To effectively manage the handling of the measuring device 100 (for example, the robot's manipulation and the positioning of the electromagnetic jet device 106 as shown in Figure 4), the products being inspected must be identified. Therefore, 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 portion of an inspected product over time or at defined time intervals; sensor data acquired over time; a video stream processed using computer vision; 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 movement data for the measuring device 100.

[0098] To implement the computer-based inspection process, an industrial system 300 incorporating the measuring device 100 may include a communication network 302 (Figure 4) (or "network") that manages incoming data to the system from various sources (for example, from at least one measuring device 100). The communication network incorporates one or more communication servers 302 (or "servers"), each comprising one or more processors 303 operationally connected to a memory 304. The memory 304 is configured to store an analysis application for data representative of the analyzed products. The processor(s) 303 include an analysis application execution module 305 that performs data processing, and the processor(s) are capable of executing programmed instructions 306 stored in memory to implement the steps of the inspection process.

[0099] The input data of an industrial system incorporating the measuring device 100 may include general information about the inspected product. General information includes stored data concerning the identification of the analyzed product (including, without limitation, its production origin, production date, materials incorporated in its production, and geometric parameters).

[0100] 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 peripheral 102 and the electromagnetic jet device 106. 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 can 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) can receive voice commands or other audio data representing, for example, an inspection start or stop. A request can be made that includes a request for the current status of an ongoing inspection cycle. A generated response can 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 stored in a neural network.

[0101] 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 (e.g., a mobile phone, a laptop computer, one or more portable network-connected devices (including augmented reality and / or virtual reality devices), network-connected wearable clothing / jewelry, and / or any combination thereof). It is conceivable that detection and comparison steps could be performed iteratively.

[0102] The terms "at least one" and "one or more" are used interchangeably. Ranges presented as being "between a and b" encompass the values ​​"a" and "b".

[0103] Although specific 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 an inspection process for an identified product during its manufacture, characterized in that the measuring device (100) comprises: an electromagnetic jet device (106) including a horn antenna (106a) extending along a predetermined height (JT) defined between a predetermined minimum diameter (d) and a predetermined maximum diameter (R), 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 antenna outlet; and a means for generating signals (108) in a predetermined frequency band, the emitted frequency band of which is chosen according to the properties of the identified product, the measuring device (100) being configured to implement the following steps of the inspection process: - a first step in which the measuring device (100) of the system employs at least one method among: a frequency domain spectroscopy method - cavity resonance (FDS-CR) or a time domain spectroscopy method - cavity resonance (TDS-CR) followed by a step of calculating a fast Fourier transform (FFT); - a second stage in which the reference spectrum is divided by a reference spectrum; - a third step performing an Inverse Fourier Transform (iFFT) before specific signal processing to denoise data from the Inverse Fourier Transform (iFFT), so that the specific signal processing is carried out in the time domain; - a fourth signal processing step including a thickness calculation according to the following expression: cAt Ci = 2n tei 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 ni 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) done on the signal obtained after the specific processing of the third step; so that, at the end of the inspection process, the processed frequency transfer function is obtained.

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

3. The measuring device (100) according to 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 device (106); such that the attachment of the electromagnetic jet device (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) according to 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) according to 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) according to any one of claims 1 to 5, wherein the electromagnetic jet has a variable resolution depending on the contrast of the materials from X / 10 to X / 100.

7. A system (300) for measuring the thickness of an identified product during manufacturing, characterized in that the system comprises: the measuring device (100) according to any one of claims 1 to 6; and a communication network (301) which manages the data entering the system from the measuring device (100), the communication network (301) incorporating one or more communication servers (302) each comprising one or more processors (303) operationally connected to a memory (304) configured to store an application for analyzing data representative of the identified products to be inspected, the processor(s) (303) comprising an execution module (305) of the analysis application configured to perform data processing, the processor(s) of which are configured to execute programmed instructions (306) stored in the memory which, when executed by the processor(s) cause them to implement the first, second, third, fourth signal processing stage and the final calculation stage.

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

9. A process for inspecting a product during production, the inspection process being implemented by a system according to 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: a frequency domain spectroscopy - cavity resonance (FDS-CR) method or a time domain spectroscopy - cavity resonance (TDS-CR) method followed by a step of calculating a fast Fourier transform (FFT); a second step in which the reference spectrum is divided by a reference spectrum; a third step performing an inverse Fourier transform (iFFT) before specific signal processing to denoise data from the inverse Fourier transform (iFFT), so that the specific signal processing is carried out in the time domain;a fourth signal processing step comprising a thickness calculation according to the following expression:; cAt Ci = 2n t Where: ei 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 m 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) done on the signal obtained after the specific signal processing of the third step; so that, at the end of the inspection process, the processed frequency transfer function is obtained.

10. The inspection process according to claim 9, wherein the fourth stage of the inspection process comprises: a step to obtain the refractive index of the identified product, wherein the refractive index is represented by the following expression: n = n' + in" where: n' represents the real part of the complex refractive index related to the propagation velocity of Fonde; and n" represents the imaginary part of the complex refractive index related to the absorption of Fonde; and a step to determine the behavior of Fonde through the materials it passes through, wherein the angle of refracted Fonde is governed by the following expression: ni sin θ = n2 sin θ where: ni represents the refractive index of a first substrate (11); and n2 represents the refractive index of a second substrate (12) - 9i is an angle of incidence of the incident Fonde, 62 is an angle of reflection of the Fonde reflected and 03 is a refraction angle of the refracted wave.

11. The inspection process according to 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: Where: ei represents the thickness of layer i; c represents the speed of light; Af represents the frequency difference between two successive resonances; and m represents the real part of the refractive index of the material in layer i.

12. The inspection process according to claim 11, wherein each resonance of the two successive resonances is an exact resonance.

13. The inspection process according to any one of claims 9 to 12, 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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