Vehicle component comprising a radar sensor and a layer arrangement forming a logo

Abstract

The invention relates to a vehicle component for a vehicle, the vehicle component comprising: - a radar sensor configured to emit radar waves in a range of wavelengths; and - a layer arrangement arranged opposite the radar sensor, the layer arrangement comprising a first subset of layers and a second subset of layers, the first subset of layers being configured to perform an optical function, each layer having a refractive index and a thickness, the second subset of layers being configured to provide protection for the first subset of layers, each layer having a refractive index and a thickness; - the vehicle component being characterized in that the total thickness of the second subset of layers is dimensioned such that the total thickness of the layer arrangement is equal to m times the wavelength of the range, divided by the product of twice the equivalent refractive index of the first subset of layers and the second subset of layers and the cosine of the refractive angle corresponding to the angle of incidence of the radar waves, wherein m is an integer.

Description

TECHNICAL FIELD

[0001] The present invention relates to a vehicle assembly. It has a particular, but not limiting, application in motor vehicles. BACKGROUND

[0002] A vehicle assembly, comprising, in a manner known to those skilled in the art:

[0003] - a radar sensor configured to emit radar waves; and

[0004] - a layer arrangement arranged facing the radar sensor.

[0005] The layer arrangement forms a luminous logo. Thus, the radar sensor is arranged behind the luminous logo and meets the requirement of detecting objects in the external environment of the vehicle.

[0006] The drawback of this prior art is that, when a radar wave is emitted by the radar sensor, it propagates to the layer arrangement and is reflected on the layer arrangement. This produces two reflected waves, one of which has been reflected on the outside of the layer arrangement and the other of which has been reflected inside the layer arrangement. These two reflected waves are the reflected waves called first-order reflected waves that return to the radar sensor. This impedes the propagation of the radar wave. This reduces the signal-to-noise ratio of the radar sensor and thus causes interference with respect to the detection by the radar sensor. The radar sensor loses the detection range. This can therefore lead to a detection error or error, or lack of detection of the object, even when the object is present in the external environment of the vehicle. SUMMARY

[0007] In this context, the aim of the present invention is to propose a vehicle assembly that allows the aforementioned drawbacks to be resolved.

[0008] To this end, the present invention proposes a vehicle assembly for a vehicle, the vehicle assembly comprising:

[0009] - a radar sensor configured to emit radar waves in a range of wavelengths; and

[0010] - a layer arrangement arranged facing the radar sensor, the layer arrangement comprising a first subset of layers and a second subset of layers, the first subset of layers being configured to perform an optical function and each layer having a refractive index and a thickness, the second subset of layers being configured to provide protection for the first subset of layers and each layer having a refractive index and a thickness;

[0011] - characterized in that the total thickness of the second subset of layers is dimensioned so that the total thickness of the arrangement of layers is equal to m times the wavelength of the range, divided by the double of the equivalent refractive index of the first subset of layers and of the second subset of layers and the cosine of the refraction angle corresponding to the incidence angle of the radar wave, where m is an integer.

[0012] According to non-limiting embodiments, the vehicle component can additionally comprise one or more additional features selected from the following, alone or in any technically possible combination.

[0013] According to one non-limiting embodiment, the radar sensor is a millimeter wave or ultra-high frequency wave or microwave radar sensor.

[0014] According to one non-limiting embodiment, the radar wave is emitted within a frequency band ranging between 100 MHz and 5 GHz.

[0015] According to one non-limiting embodiment, if the incidence angle is equal to zero, the total thickness of the second subset of layers is dimensioned so that the total thickness of the arrangement of layers is equal to the wavelength divided by the double of the equivalent refractive index of the first subset of layers and of the second subset of layers.

[0016] According to one non-limiting embodiment, the total thickness is defined with an incidence angle equal to arctan(d1 / (2e4)), where e4 is the distance between the radar sensor and the arrangement of layers and d1 is the distance between the transmitter antenna and the receiver antenna of the radar sensor.

[0017] According to one non-limiting embodiment, the second subset of layers comprises an output layer and a protective layer. The protective layer is an anti-UV and / or anti-scratch layer.

[0018] According to one non-limiting embodiment, the output layer has a refractive index with a difference from the equivalent refractive index of the first subset of layers less than 0.1.

[0019] According to one non-limiting embodiment, the output layer has a refractive index with a difference from the equivalent refractive index of the first subset of layers less than 0.05.

[0020] According to one non-limiting embodiment, each layer of the first subset has a refractive index with a difference from the refractive index of the adjacent layer less than 0.1.

[0021] According to one non-limiting embodiment, each layer of the first subset has a refractive index with a difference from the refractive index of the adjacent layer less than 0.05.

[0022] According to one non-limiting embodiment, the first subset of layers comprises:

[0023] - a film layer;

[0024] - a scattering layer;

[0025] - a reflecting layer; and

[0026] - an opaque layer.

[0027] According to one non-limiting embodiment, said arrangement of layers forms a non-luminous logo.

[0028] According to one non-limiting embodiment, said arrangement of layers forms a luminous logo.

[0029] According to one non-limiting embodiment, said first subset of layers further comprises an optical layer.

[0030] According to one non-limiting embodiment, said first subset of layers further comprises:

[0031] - a further opaque layer;

[0032] - a further reflecting layer.

[0033] According to one non-limiting embodiment, said first subset of layers further comprises a protective layer.

[0034] There is also proposed an arrangement of layers facing a radar sensor arrangement configured to emit radar waves in a range of wavelengths, said arrangement of layers comprising a first subset of layers and a second subset of layers, said first subset of layers being configured to perform an optical function and each layer having a refractive index and a thickness, said second subset of layers being configured to provide protection to said first subset of layers and each layer having a refractive index and a thickness;

[0035] - characterized in that the total thickness of said second subset of layers is dimensioned such that said total thickness of said arrangement of layers is equal to m times the wavelength of said range, divided by the product of twice the equivalent refractive index of said first subset of layers and said second subset of layers and the cosine of the refraction angle corresponding to the angle of incidence of the radar waves, where m is an integer. BRIEF DESCRIPTION OF DRAWINGS

[0036] The present application, together with its various applications, will be better understood by reading the following description, taken in conjunction with the accompanying drawings, in which:

[0037] Figure 1 is a schematic view of a vehicle assembly according to one non-limiting embodiment of the present application, wherein said vehicle assembly comprises a radar sensor and an arrangement of layers;

[0038] Figure 2 is a schematic view of a radar wave emitted by the radar sensor of the vehicle assembly of Figure 1 Figure 1 ​partly reflect on a layer arrangement of vehicle components of the vehicle 2;

[0039] Figure 3 is according to one non-limiting embodiment Figure 1 schematic representation of layers of a layer arrangement of vehicle components of the vehicle 2, wherein the layer arrangement comprises a first subset of layers and a second subset of layers.

[0040] Unless otherwise indicated, structurally or functionally identical elements appearing in the various drawings are designated using the same reference signs. DETAILED DESCRIPTION

[0041] Reference is made to Figures 1 to 3 A vehicle component 1 of a vehicle 2 according to the present application is described. The vehicle component 1 is also referred to as vehicle system 1. In one non-limiting embodiment, the vehicle 2 is a motor vehicle. A motor vehicle is understood to mean any type of motor vehicle. Throughout the remainder of the specification, this embodiment is considered a non-limiting example. Throughout the remainder of the specification, the vehicle 2 is also referred to as motor vehicle 2. In one non-limiting embodiment, the vehicle component 1 is provided in a grille of the motor vehicle 2. In another non-limiting embodiment, the vehicle component 1 can be integrated into a body part located at a rear portion of the motor vehicle 2.

[0042] As Figure 1 illustrated in

[0043] - a radar sensor 10 configured to emit radar waves R1; and

[0044] - a layer arrangement 11 provided facing the radar sensor 10.

[0045] These elements are described hereinafter.

[0046] The radar sensor 10 is described hereinafter. As Figure 1As illustrated in the middle, the radar sensor 10 is arranged facing the layer arrangement 11. In one non-limiting embodiment, the radar sensor 10 is a millimeter wave (between 24 GHz and 300 GHz) or ultra-high frequency wave (between 300 MHz and 81 GHz) or microwave (between 1 GHz and 300 GHz) radar sensor. In one non-limiting alternative embodiment, the radar sensor 10 operates at a radar frequency in the range between 76 GHz and 81 GHz. Radar waves R1 are emitted within a range Δ1 of wavelengths λ. In one non-limiting embodiment, the radar waves R1 are emitted within a frequency band in the range between 100 MHz and 5 GHz. Thus, in one non-limiting example, if the sensor operates at a radar frequency of 77 GHz (i.e. a wavelength λ of 3.95 mm) with a frequency band of 1 GHz, the radar sensor 10 will operate within a frequency band of 76.5 GHz to 775 GHz. Thus, the radar waves R1 will be emitted within a frequency range of 76.5 GHz to 77.5 GHz (i.e. a range Δ1 of wavelengths λ of 3.87 mm to 392 mm). Thus, in another non-limiting example, if the radar sensor 10 operates at a radar frequency of 78.5 GHz with a frequency band of 5 GHz, the radar sensor 10 will operate within a frequency band of 76 GHz to 81 GHz. Thus, the radar waves R1 will be emitted within a frequency range of 76 GHz to 81 GHz (i.e. a range Δ1 of wavelengths λ of 3.701 mm to 3.945 mm).

[0047] As Figure 2 As illustrated in the middle, the emitted radar waves R1 arrive on the layer arrangement 11 with an angle of incidence θ. In one non-limiting embodiment, the angle of incidence θ is within a range between 0° and + / - 30°. Thus, the radar sensor 10 comprises a field of view FOV that varies between -30° and +30°. The center of the field of view FOV is at an angle of 0° with respect to the longitudinal axis of the vehicle (also referred to as the axis of the vehicle). In another non-limiting embodiment, the field of view FOV varies between -90° and +45°. The center of the field of view FOV is at an angle of -45° with respect to the axis of the vehicle and the angle of incidence θ of the radar waves R1 on the layer arrangement 11 remains close to 0° (with the vehicle component 1 then being positioned at about 45° with respect to the axis of the vehicle).

[0048] The radar sensor 10 is configured to scan the external environment of the motor vehicle 2 by means of the emission of radar waves R1. As Figure 1 As illustrated in the middle, the radar sensor 10 thus comprises:

[0049] - at least one transmitter antenna 100 configured to emit radar waves R1 (also referred to as primary radar waves R1);

[0050] - at least two receiver antennas 101 configured to receive radar waves R2 (also referred to as secondary radar waves R2 or returned radar waves R2).

[0051] The radar sensor 10 further comprises at least one transmitter 103 configured to generate primary radar waves R1 and at least one receiver 104 configured to process received returned secondary radar waves R2. In one non-limiting embodiment, a single electronic element can be used for both (transmitting and receiving) functions. There will thus be one or more transceivers. The transmitter 103 generates primary radar waves R1 which are then transmitted by the transmitter antenna 100, which waves are reflected on objects 3 in the external environment of the motor vehicle 2 (in this case, in the illustrated non-limiting example, a pedestrian) when they encounter them. The radar waves thus reflected are waves which are transmitted back to the radar sensor 10. These are the secondary radar waves R2 which are received by the receiver antennas 101. These are the radar waves which are retransmitted towards the radar sensor 10. In one non-limiting embodiment, the primary radar waves R1 and the secondary radar waves R2 are radiofrequency waves. In one non-limiting embodiment, the radar sensor 10 comprises a plurality of transmitters 103 and a plurality of receivers 104.

[0052] The transmitter antenna 100 (also referred to as antenna 100) is configured to transmit the primary radar waves R1 generated by the transmitter 103. The receiver antennas 101 (also referred to as antennas 101) are configured to receive the secondary radar waves R2 and send them to the receiver 104, which then processes them. There is a phase shift between the secondary radar waves R2 received by the receiver antennas 101, which allows the angular position of the objects 3 located in the external environment of the motor vehicle 2 to be derived therefrom, with respect to the motor vehicle 2. In non-limiting embodiments, the antennas 100, 101 are patch antennas or slot antennas.

[0053] In one non-limiting embodiment, the antennas 100, 101, the transmitter 103 and the receiver 104 are arranged on a printed circuit board 105. In one non-limiting embodiment, the printed circuit board is a rigid printed circuit board (also referred to as printed circuit board assembly (PCBA)) or a flexible printed circuit board (also referred to as "Flexboard").

[0054] The radar sensor 10 further comprises an electronic control unit 106 configured to control the transmitter 103 and the receiver 104. Since radar sensors are known to the person skilled in the art, they are not described in greater detail herein.

[0055] The layer arrangement 11 is described below. As Figure 1 or Figure 3As illustrated in

[0056] - a first subset S1 of layers 110, said first subset of layers being configured to perform an optical function; and

[0057] - a second subset S2 of layers 112, said second subset of layers being configured to provide protection to said first set S1 of layers 110.

[0058] It is noted that, as Figure 1 is a schematic illustration, only two layers 110 are shown in Figure 1 . In the remainder of the description, the first subset S1 of layers 110 is also referred to as the first subset S1 and the second subset S2 of layers 112 is also referred to as the second subset S2. In a non-limiting embodiment, the layer arrangement 11 forms a light-emitting logo or a non-light-emitting logo. In the case of a light-emitting logo, the vehicle component 1 comprises one or more light sources 12. In the remainder of the description, the non-limiting embodiment of a light-emitting logo is taken as an example.

[0059] Indeed, as Figure 3 illustrated in, in one non-limiting embodiment, the logo is light-emitting by two light sources 12. In the illustrated non-limiting example, the light sources 12 are disposed on the sides of the first subset S1 of layers 110. The optical device 12’ with total reflection allows the light emitted by the light sources 12 to be injected inside the layer 110c described hereafter. In one non-limiting embodiment, the light sources 12 are semiconductor light sources. In one non-limiting embodiment, the semiconductor light sources form part of a light-emitting diode. A light-emitting diode is understood to mean any type of light-emitting diode, whether in the non-limiting examples of LED, OLED (organic LED), AMOLED (active matrix organic LED) or even in the non-limiting example of FOLED (flexible OLED). In another non-limiting embodiment, the light sources 12 are light bulbs with a filament.

[0060] As illustrated in Figure 1 , the first subset S1 of layers 110 is disposed facing the radar sensor 10, while the second subset S2 of layers 112 is disposed adjacent to the first subset S1 of layers 110 and facing the outside of the motor vehicle 2.

[0061] As illustrated in Figure 3 , each layer 110 of the first subset S1 has a refractive index n10 and a thickness e10. The first subset S1 has a total thickness e1 consisting of all the thicknesses e10. Each layer 112 of the second subset S2 has a refractive index n20 and a thickness e20. The second subset S2 comprises a total thickness e2 consisting of all the thicknesses e20. Thus, the layer arrangement 11 comprises a total thickness e0 = e1 + e2.

[0062] In one non-limiting embodiment, the first subset SI of layers 110 comprises an optical layer 110c. The optical layer 110c faces the radar sensor 10. The optical layer 110c allows the emission of light rays from the light source 12. The optical layer 110c is a layer that is transparent to both radar waves R1, R2 and visible light. In a non-limiting embodiment, the optical layer 110c can be a light guide or a lens with prisms.

[0063] As Figure 3 illustrated in FIG. 1 1, in one non-limiting embodiment, the first subset SI of layers 110 comprises the following successive layers 110:

[0064] - an optical layer 110c;

[0065] - a film layer 110d;

[0066] - a scattering layer 110e;

[0067] - a reflective layer 110f;

[0068] - an opaque layer 110g.

[0069] All layers 110 except the reflective layer 110f are dielectric layers, which makes them transparent to radar waves R1, R2. The reflective layer 110f is more absorptive but very thin, which also allows radar waves R1 to pass through the reflective layer 110f. In one non-limiting embodiment, the reflective layer 110f is made of indium. In a non-limiting embodiment, the dielectric layers are formed of plastic, glass or ceramic material. In one non-limiting example, the plastic is polycarbonate (PC). As a reminder, unlike conductive materials, dielectric materials are not electrically conductive and thus allow radar waves R1 to pass through.

[0070] In this non-limiting embodiment, the optical layer 110c acts as a support for the film layer 110d. The film layer 110d is arranged between the optical layer 110c and the reflective layer 110f. In a non-limiting example, the film layer 110d is made of PC-IML (polycarbonate in-mold label).

[0071] The scattering layer 110e is arranged between the film layer 110d and the opaque layer 110g. The scattering layer 110e allows the creation of an auxiliary source located in the vicinity of said scattering layer 110e. This thus allows the design of the light-emitting logo to be perceived at the location of said scattering layer 110e. In one non-limiting embodiment, the scattering layer 110e is arranged to face an opening 111 formed in the opaque layer 110g. The opening 111 allows the design of the logo to be created.

[0072] The opaque layer 110g is arranged to face the second set S2 of layers 112. The opaque layer 110g allows well-defined areas to be masked and illuminated. It allows a pattern to be created for the light-emitting logo.

[0073] When the logo is observed from the outside, the reflective layer 110f allows to provide a metallic appearance under visible light. The reflective layer 110f can extend under the entire opaque layer 110g.

[0074] As Figure 3 illustrated in FIG. 1 1 1, in one non-limiting embodiment, the first subset S1 of layers 1 10 further comprises:

[0075] - a further opaque layer 1 10a;

[0076] - a further reflective layer 1 10b.

[0077] The further opaque layer 1 10a, when present, is arranged facing the radar sensor 10 and adjacent to the further reflective layer 1 10b. It prevents light leaks behind the illuminated logo that can be seen from the outside of the motor vehicle 2. It absorbs light coming from the light source 12.

[0078] The further reflective layer 1 10b, when present, is arranged between the opaque layer 1 10a and the optical layer 1 10c. In one non-limiting embodiment, the further reflective layer 1 10b is a white paint. It allows the light rays emitted by the light source 12 to be reflected towards the center of the layer arrangement 1 1.

[0079] As Figure 3 illustrated in FIG. 1 1 1, in one non-limiting embodiment, the first subset S1 of layers 1 10 further comprises a protective layer 1 10h for preventing oxidation of the other layers 1 10, in particular of the reflective layer 1 10f. The protective layer 1 10h is arranged between the opaque layer 1 10g and the second set S2 of layers 1 12.

[0080] In one non-limiting embodiment, the second subset S2 of layers 1 12 comprises an output layer 1 12a forming an output outer lens of the illuminated logo and a protective layer 1 12b preventing yellowing of the plastic of the output outer lens 1 12a in particular and also of the protective layer 1 10h by blocking ultraviolet rays. In one non-limiting embodiment, the protective layer 1 12b can also be an anti-scratch layer. In one non-limiting embodiment, the output layer 1 12a is made of PC. This is a layer that is transparent to both radar waves R1, R2 and visible light. In one non-limiting embodiment, the protective layer 1 12b has a thickness e20b of 50 microns. In one non-limiting embodiment, the protective layer 1 12b is a deposited layer of protective varnish.

[0081] It should be noted that when the layers 1 10 each have a refractive index n10 very close, in other words adjacent, to the refractive index n10 of another adjacent layer 1 10, the set of layers 1 10 of the first subset S1 can be considered equivalent to a layer having an equivalent refractive index n eq1of the total thickness e2of the single equivalent layer. Thus, in one non-limiting embodiment, each layer 112 has an index n20that differs from the index n20of the adjacent layer 112 by less than 0.1. This threshold also allows the internally reflected waves between the layers 112 of the second subset S2 to be rendered negligible. In other words, the difference between the index n20a of the output layer 112a and the index n20b of the protective layer 112b adjacent thereto is less than 0.1. In one non-limiting alternative embodiment of this non-limiting embodiment, the difference is less than 0.05.

[0082] Similarly, it should be noted that when the layers 112 each have an index n20very close to, in other words adjacent to, the index n20of another adjacent layer 112, the set of layers 112 of the second subset S2 can be considered equivalent to a single equivalent layer having an equivalent index n eq2 of the total thickness e2of the single equivalent layer. Thus, in one non-limiting embodiment, each layer 112 has an index n20that differs from the index n20of the adjacent layer 112 by less than 0.1. This threshold also allows the internally reflected waves between the layers 112 of the second subset S2 to be rendered negligible. In other words, the difference between the index n20a of the output layer 112a and the index n20b of the protective layer 112b adjacent thereto is less than 0.1. In one non-limiting alternative embodiment of this non-limiting embodiment, the difference is less than 0.05.

[0083] The first subset S1 has an equivalent index n eq1 . To calculate the equivalent index n eq1 , it is calculated step by step. Thus, the equivalent index n eqa of the two first adjacent layers 110a, 110b is first calculated, i.e.:

[0084] [mathematical function 1]

[0085]

[0086] Thus, the two layers 110a and 110b are replaced by a single layer having a total thickness e a = e10a+ e10b (same as the two layers). The equivalent index n eqa is then calculated between this obtained layer of equivalent index n eq1 and the next adjacent layer, in this case 110c, and so on.

[0087] Thus, the first subset S1 has an equivalent index n eq1 which is equal to:

[0088] [mathematical function 2]

[0089]

[0090] where e e is the total thickness of the layers 110a to 110g and n eqeis the equivalent refractive index of the layers 110a to 110g.

[0091] The equivalent refractive index n of the second subset S2 eq2 is equal to:

[0092] [mathematical function 3]

[0093]

[0094] The equivalent refractive index n of the first subset S1 and of the second subset S2 is thus obtained eq0 :

[0095] [mathematical function 4]

[0096]

[0097] It should be noted that the refractive index n can be calculated from the dielectric constant of the layers. Since this calculation is known to the person skilled in the art, it is not described herein.

[0098] As illustrated in Figure 2 Fig. 1, when a radar wave R1 is emitted by the radar sensor 10, the radar wave R1 propagates upwards to the layer arrangement 11 having an equivalent refractive index n eq0 and a total thickness e0.

[0099] The radar wave R1 is reflected on the layer arrangement 11 and generates two reflected waves, one of which R11 has been reflected on the outside of the first subset S1, while the other has been reflected inside the layer arrangement 11. The two reflected waves R11 and R12 are reflected waves that return to the radar sensor 10 (referred to as first-order reflected waves). These are stray light reflections. When the angle of incidence θ is different from 0°, the corresponding angle of refraction r is also different from 0°.

[0100] The phase difference (also referred to as phase shift ) between these two reflected waves R11 and R12 is equal to:

[0101] [mathematical 5]

[0102]

[0103] where:

[0104] -n eq is the total equivalent refractive index of the first subset S1 and of the second subset S2;

[0105] - δ is the path of the reflected wave R12 in the material, equal to 2e0 / cos(r);

[0106] - nδ / λ is the phase shift due to the path through the material;

[0107] - n is the phase shift due to internal reflections in the first subset S1 and in the second subset S2;

[0108] - ((2e0tan(r)sin(0)) / l) is the phase shift in air due to the difference between the reflection point Pt1 of the reflected wave R11 and the emergence point Pt2 of the reflected wave R12.

[0109] Since sin(0) = n eq0 x sin(r), the following is obtained:

[0110] [mathematical function 6]

[0111]

[0112] That is:

[0113] [mathematical function 7]

[0114]

[0115] And this is true regardless of the value of the refraction angle r.

[0116] Since the reflected waves R11 and R12 return towards the radar sensor 10, they cause disturbances on the radar sensor 10, i.e. they cause a degradation of the signal-to-noise ratio. In order to eliminate these disturbances, the total thickness e0of the layer arrangement 11 will be defined so that the reflected waves R11 and R12 are out of phase to produce destructive interference. In order to obtain destructive interference, the phase difference between the two reflected waves R11 and R12 must be equal to n modulo 2n. Therefore, e0= m l / (2n cos(r), where m is a natural integer. Thus, the following is obtained:

[0117] [mathematical function 8]

[0118]

[0119] That is:

[0120] Let e0= m l / (2n eq 0cos(r)).

[0121] It should be noted that the equation e0= m l / (2n eq cos(r)) applies regardless of the value of the angle r. Therefore, the size of this total thickness e0is determined so that it is equal to m times the wavelength l of the range D1, divided by twice the equivalent refractive index n eq0 of the first subset S1 of layers 110 and of the second subset S2 of layers 112 and the cosine of the refraction angle r corresponding to the incidence angle 0 of the radar wave R1, where m is an integer. Thus, according to the total equivalent refractive index neq0 and the wavelength l used in the operating frequency range of the radar sensor 10, it is possible to determine the total thickness e0 of the layer arrangement 11 so that said reflected waves R11 and R12 cancel each other out. In one non-limiting embodiment, the chosen wavelength l is the one that is in the middle of said range D1.

[0122] The ideal total thickness e0 is defined when the incidence angle is equal to 0 and m is equal to 1. When 0 = 0, r = 0. Thus, for m = 1, the ideal total thickness e0 of the layer arrangement 11 is thus e0 = l / (2n eq ) with n

[0123] The layer arrangement 11 has a total thickness e0 formed by the total thickness e1 of the first subset S1 of layers 110 and by the total thickness e2 of the second subset S2 of layers 112. Since it is preferable to avoid adjusting the total thickness e1 to avoid modifying the optical performance of the luminous badge, the total thickness e2 will be adjusted in order to obtain the ideal e0 = l / (2n eq0 ) at 0 = 0, or e0 = m l / (2n eq0 cos(r)) at 0 ≠ 0. Adjusting the total thickness e2 does not change the optical performance of the luminous badge. It should be noted that, in the case of a non-luminous badge, it is also possible to adjust the total thickness e1, in particular by modifying the thickness e10d of the film layer 110d.

[0124] Thus, the total thickness e2 of the second subset of layers 112 is dimensioned so that, for an incidence angle 0 equal to zero, the total thickness e0 of the layer arrangement 11 is equal to said wavelength l divided by twice the equivalent refractive index n eq0 of the first subset S1 of layers 110 and of the second subset S2 of layers 112. If the incidence angle 0 is not equal to zero, one obtains e0 = m l / (2n eq0 cos(r)). This equation applies whatever the value of the refraction angle r. It should be noted that, in practice, the thickness e20a of the output layer 112a will be adjusted. Indeed, since the protective layer 112b is already very thin, its thickness e20b cannot be adjusted.

[0125] In one non-limiting embodiment, the layer arrangement 11 has a total thickness e0 in the range between 0.8 and 1.2 times said ideal total thickness e0. This range of values takes into account possible emission angles of the radar sensor 10. The possible values of the incidence angle 0 are defined in the technical specifications of the radar sensor 10, which means that the possible values of the incidence angle 0 are in the field of view of the radar sensor 10. In one non-limiting example, the incidence angle 0 is in the range between 0° and + / - 30°. The range of values from 0.8 to 1.2 allows manufacturing tolerances of the total thickness e0 to be taken into account.

[0126] It should be noted that the value of the incidence angle θ is comprised in the possible emission angles of the radar sensor 10. The possible values of the incidence angle θ are defined in the technical specifications of the radar sensor 10. It should be noted that there is a value of the incidence angle for which the reflected radar waves R11 and R12 cause the maximum interference of the receiver antenna 101 of the radar sensor 10. This incidence angle θ is called critical incidence angle θ. In one non-limiting embodiment, this value is equal to θ = arctan(d1 / (2e4)), where d1 is the distance between the transmitter antenna 100 and the receiver antenna 101, e4 is the distance between the radar sensor 10 and the layer arrangement 11, as illustrated in Figure 2 Fig. 3. Thus, the value of the total thickness e0 is determined for an incidence angle θ equal to arctan(d1 / (2e4)). It should be noted that in one non-limiting example, the midpoint of the receiver antenna 101 is taken to calculate d1.

[0127] Thus, according to the value of the total equivalent refractive index n eq0 and the value of the wavelength λ used in the operating frequency range of the radar sensor 10 (between 76 GHz and 81 GHz in the non-limiting example used), it is possible to determine the value of the total thickness e0 (more specifically, the value of the total thickness e2 of the second subset s2) so that the first order reflected waves R11 and R12 cancel each other out. Thus, the receiver antenna 101 experiences less noise. A better signal-to-noise ratio is obtained.

[0128] It should be noted that in order to avoid having internal reflected waves between the output layer 112a and the first subset S1 of layers 110, in one non-limiting embodiment, the output layer 112a has a refractive index n20a which differs from the equivalent refractive index neq1 of the first subset S1 of layers 110 by less than 0.1. In one non-limiting alternative embodiment, this difference is less than 0.05.

[0129] Of course, the description of the invention is not limited to the embodiments described above and to the fields described above. Thus, in another non-limiting embodiment, the radar sensor 10 comprises more than one transmitter antenna 100 and more than two receiver antennas 101. Thus, in another non-limiting embodiment, the light source 12 is integrated into the cavity of the layer 110c. Thus, in a non-limiting embodiment of a non-illuminated logo, the first subset S1 does not comprise the layers 110a to 110c and optionally 110d.

[0130] Thus, the described invention has in particular the following advantages:

[0131] - it allows to eliminate the first order reflected waves R11, R12 reflected towards the radar sensor 10. Thus, the signal-to-noise ratio of said radar sensor 10 is no longer low. The emission of the radar waves R1 is improved;

[0132] - it allows to adjust only the total thickness e2 of the second subset S2 (in particular the thickness e20a of the output layer 112a) without having to change the total thickness e1 of the first subset S1, so that the optical performance of the light-emitting badge are not modified.

Claims

1. A vehicle assembly (1) for a vehicle (2), the vehicle assembly (1) comprising: - a radar sensor (10) configured to emit radar waves R1 within a range D1 of wavelengths l; and - a layer arrangement (11) arranged facing the radar sensor (10), the layer arrangement comprising a first subset (SI) of layers (110) configured to perform an optical function, each layer (110) having a refractive index n10 and a thickness e10, and a second subset (S2) of layers (112) configured to provide protection for the first subset (SI) of layers (110), each layer (112) having a refractive index n20 and a thickness e20; - characterized in that the total thickness e2 of the second subset (S2) of layers (112) is dimensioned so that the total thickness e0 of the layer arrangement (11) is equal to m times the range Δ1 of wavelengths λ divided by twice the equivalent refractive index n eq0 of the first subset (S1) of layers (110) and the second subset (S2) of layers (112) multiplied by the cosine of the refraction angle r corresponding to the angle of incidence θ of the radar wave R1, where m is an integer.

2. The vehicle component (1) according to claim 1, wherein the radar sensor (10) being a millimeter wave or ultra-high frequency wave or microwave radar sensor.

3. The vehicle component (1) according to claim 2, wherein the radar waves R1 are emitted within a frequency band ranging between 100 MHz and 5 GHz.

4. The vehicle component (1) according to any one of claims 1 to 3, wherein, If said angle of incidence θ is equal to zero, said total thickness e2 of said second subset (S2) of layers (112) is dimensioned so that said total thickness e0 of said layers arrangement (11) is equal to said wavelength λ divided by twice said equivalent refractive index n eq0 of said first subset (S1) of layers (110) and said second subset (S2) of layers (112).

5. The vehicle component (1) according to any one of claims 1 to 3, wherein the total thickness e0 is defined with an angle of incidence 0 equal to arctan (dl / (2e4)), where e4 is a distance between the radar sensor (10) and the layer arrangement (11), and dl is a distance between a transmitter antenna (100) and a receiver antenna (101) of the radar sensor (10).

6. The vehicle assembly (1) according to any one of claims 1 to 3, wherein the second subset (S2) of layers (112) comprises an output layer (112a) and a protection layer (112b).

7. The vehicle component (1) according to claim 6, wherein the output layer (112a) has a refractive index n20a that differs less than 0.1 from the equivalent refractive index n of the first subset (SI) of layers (110). eq1 of the first subset (SI) of layers (110).

8. The vehicle component (1) according to claim 7, wherein the output layer (112a) has a refractive index n20a that differs less than 0.05 from the equivalent refractive index n20 of the first subset (SI) of layers (110). eq1 of the first subset (SI) of layers (110).

9. The vehicle component (1) according to any one of claims 1 to 3, wherein, each layer (110) of the first subset (SI) has a refractive index n10 that differs from the refractive index n10 of an adjacent layer (110) by less than 0.

1.

10. The vehicle component (1) according to claim 9, wherein each layer (110) of the first subset (SI) has a refractive index n10 that differs from the refractive index n10 of an adjacent layer (110) by less than 0.

05.

11. The vehicle assembly (1) according to any one of claims 1 to 3, wherein the first subset (SI) of layers (110) comprises: - a film layer (110d); - a scattering layer (110e); - a reflective layer (110f); and - an opaque layer (110g). the layer arrangement (11) forms a non-luminous logo.

12. The vehicle component (1) according to any one of claims 1 to 3, wherein the layer arrangement (11) forms a luminous logo.

13. The vehicle component (1) according to any one of claims 1 to 3, wherein, 14. The vehicle assembly (1) according to claim 13, wherein the first subset (SI) of layers (110) further comprises an optical layer (110c). ​ 15. A layer arrangement (11) arranged in front of a radar sensor (10), the radar sensor (10) being configured to emit radar waves R1 in a range Δ1 of wavelengths λ, the layer arrangement (11) comprising a first subset (SI) of layers (110) and a second subset (S2) of layers (112), the first subset (SI) of layers (110) being configured to perform an optical function, each layer (110) having a refractive index n10 and a thickness e10, the second subset (S2) of layers (112) being configured to provide protection for the first subset (SI) of layers (110), each layer (112) having a refractive index n20 and a thickness e20; - characterized in that, The total thickness e2 of the second subset (S2) of layers (112) is dimensioned so that the total thickness e0 of the layer arrangement (11) is equal to m times the range Δ1 of wavelengths λ divided by the product of the equivalent refractive index n eq0 of the first subset (S1) of layers (110) and the second subset (S2) of layers (112) and twice the cosine of the refraction angle r corresponding to the angle of incidence θ of the radar wave R1, where m is an integer.

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