VEHICLE ARRANGEMENT WITH A RADAR SENSOR AND A LIGHT-EMPLOYING SIGNAL MODULE

Description

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

[0002] Increasingly, radar sensors are being used to detect objects in a vehicle's surroundings, estimate their angular position, and consequently trigger functions such as automatic emergency braking, cruise control, or blind spot detection. These radar sensors are typically mounted behind the vehicle's bumper.

[0003] One drawback of this prior art is that integration behind the bumper reduces the performance of radar sensors due to the metallic paint layer applied to the bumper and the bumper's curved shape. This results in inaccurate estimation of an object's angular position.

[0004] Document DE102011115829A1 discloses a radar and a light module performing a signaling function according to the prior art.

[0005] In this context, the present invention aims to provide a vehicle assembly that solves the aforementioned problem.

[0006] To this end, the invention proposes a vehicle assembly, said vehicle assembly comprising: a radar sensor configured to emit radar waves over a range of wavelengths, and a light module configured to perform a signaling function, said light module comprising a sub-layer and a pattern layer, said pattern layer forming a sub-wavelength structured dielectric element with a pattern repetition period that is less than one-quarter of a wavelength of said range, and characterized in that the total thickness of said light module is equal to m times a wavelength of said range, all divided by twice the equivalent refractive index of said sub-layer and of said pattern layer times the cosine of a refracted angle corresponding to an angle of incidence of the radar waves, with m an integer.

[0007] According to non-limiting embodiments, the vehicle assembly may further comprise one or more additional features taken alone or in all technically possible combinations, from among the following.

[0008] According to a non-limiting embodiment, said radar sensor is a millimeter wave or microwave or microwave radar sensor.

[0009] According to a non-limiting embodiment, said radar waves are emitted on a frequency band between 100MHz and 5GHz.

[0010] According to a non-limiting embodiment, said pattern repetition period is less than one tenth of said radar wave wavelength.

[0011] According to a non-limiting embodiment, said motifs are cylindrical, rectangular, pyramidal, cubic prisms, or portions of tori.

[0012] According to a non-limiting embodiment, a motif includes dimensions less than 0.4mm.

[0013] According to a non-limiting embodiment, said total thickness is formed by the height of said patterns and by the thickness of said underlayer.

[0014] According to a non-limiting embodiment, if the angle of incidence is equal to zero then the total thickness is equal to said wavelength divided by twice the equivalent refractive index.

[0015] According to a non-limiting embodiment, the total thickness is defined with an angle of incidence equal to arctan(d1 / (2e4)), with e4 the distance between said radar sensor and said light module and d1 the distance between a transmitting antenna and receiving antennas of said radar sensor.

[0016] According to a non-limiting embodiment, said light module further comprises a reflective layer and the total thickness of said light module is equal to m times a wavelength of said range divided by twice the equivalent refractive index of said sub-layer, of said pattern layer and of said reflective layer times the cosine of a refracted angle corresponding to an angle of incidence of radar waves, with m an integer.

[0017] According to a non-limiting embodiment, the equivalent refractive index is calculated for an angle of incidence of radar waves equal to the center of a field of view of said radar sensor.

[0018] According to a non-limiting embodiment, said light module is a daytime running light module, or a turn signal, or a reflector, or a raised brake light.

[0019] A light module is further proposed, disposed opposite a radar sensor configured to emit radar waves over a range of wavelengths, said light module being configured to perform a signaling function and comprising a sub-layer and a pattern layer, said pattern layer forming a sub-wavelength structured dielectric element with a pattern repetition period which is less than one-quarter of a wavelength of said range, and characterized in that the total thickness of said light module is equal to m times said wavelength, all divided by twice the equivalent refractive index of said sub-layer and said pattern layer times the cosine of a refracted angle corresponding to an angle of incidence of the radar waves, with m an integer.

[0020] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures: [ Fig. 1 ] is a schematic view of a vehicle assembly, said vehicle assembly comprising a radar sensor and a light module, according to a non-limiting embodiment of the invention, [ Fig. 2 ] is a schematic view of a radar wave emitted by the radar sensor of the figure 1 which is partially reflected on said luminous module of the figure 1 , according to a non-limiting embodiment, [ Fig. 3 ] is a schematic view of the light module of the figure 1 said light module comprising a sub-layer and a pattern layer, according to a non-limiting embodiment, [ Fig. 4 ] is a perspective view of a local area of ​​the patterns in the pattern layer of the light module of the figure 3 , according to a non-limiting embodiment, [ Fig. 5 ] is a schematic view of a radar wave emitted by the radar sensor of the figure 1 which is reflected on the said luminous module of the figure 1 said luminous module comprising an additional layer which is a reflective layer, according to a non-limiting embodiment.

[0021] Identical elements, whether structural or functional, appearing on different figures retain the same references unless otherwise specified.

[0022] The vehicle assembly 1 of a vehicle 2 according to the invention is described with reference to figures 1 à 5 Vehicle assembly 1 is also referred to as vehicle system 1. In a non-limiting embodiment, vehicle 2 is a motor vehicle. A motor vehicle is defined as any type of motorized vehicle. This embodiment is taken as a non-limiting example in the following description. In the following description, vehicle 2 is thus also referred to as motor vehicle 2. In a non-limiting embodiment, vehicle assembly 1 is arranged in a lighting or signaling device of the front or rear of motor vehicle 2.

[0023] As illustrated on the figure 1 The vehicle lighting system 2 includes: a radar sensor 10 having a field of view FOV and configured to emit radar waves R1 in said field of view FOV, over a range Δ1 of wavelengths λ, a light module 13 configured to perform a signaling function f1, otherwise called function f1. It is thus otherwise called signaling light module 13.

[0024] Vehicle assembly 1 further includes an exit window 12. The exit window 12 may or may not be part of the light module 13.

[0025] The radar sensor 10 is described below. As illustrated on the figure 1 The radar sensor 10 is positioned opposite the light module 13. In a non-limiting embodiment, the radar sensor 10 is a millimeter-wave radar sensor (between 24 GHz and 300 GHz), a microwave radar sensor (between 300 MHz and 81 GHz), or a microwave radar sensor (between 1 GHz and 300 GHz). In a non-limiting variant, the radar sensor 10 operates at a radar frequency between 76 GHz and 81 GHz. In a non-limiting embodiment, the radar waves R1 are emitted over a frequency band between 100 MHz and 5 GHz. Thus, in a non-limiting example, if the sensor operates at a radar frequency of 77 GHz, corresponding to a wavelength λ of 3.95 mm, with a frequency band of 1 GHz, the radar sensor 10 will operate over a frequency band from 76.5 GHz to 77.5 GHz. The R1 radar waves will thus be emitted on the frequency range 76.5GHz to 77.5GHz, i.e. a Δ1 range of wavelengths λ from 3.87mm to 3.92mm.Thus, in another non-limiting example, if radar sensor 10 operates at a radar frequency of 78.5 GHz with a frequency band of 5 GHz, radar sensor 10 will operate on a frequency band from 76 GHz to 81 GHz. The radar waves R1 will therefore be emitted on the frequency range of 76 GHz to 81 GHz, i.e., a range Δ1 of wavelengths λ from 3.701 mm to 3.945 mm.

[0026] As illustrated on the figure 2 The emitted radar waves R1 arrive at an angle of incidence θ on the light module 13. In a non-limiting embodiment, the angle of incidence θ is between 0° and ±30°. The field of view (FOV) thus varies between -30° and +30°. The center of the FOV is at an angle of 0° with respect to the longitudinal axis of the vehicle, also known as the vehicle axis. In another non-limiting embodiment, the FOV thus varies between -90° and +45°. The center of the FOV is at an angle of -45° with respect to the vehicle axis, and the angle of incidence θ of the radar waves R1 on the light module 13 remains close to 0° (the vehicle assembly 1 being then positioned at approximately 45° to the vehicle axis).

[0027] The radar sensor 10 is configured to scan the external environment of the motor vehicle 2, through the emission of radar waves R1. As illustrated on the figure 1 The radar sensor 10 thus comprises: at least one transmitting antenna 100 configured to transmit R1 radar waves, otherwise called primary R1 radar waves, at least two receiving antennas 101 configured to receive R2 radar waves, otherwise called secondary R2 radar waves, or R2 return radar waves.

[0028] The radar sensor 10 further comprises at least one transmitter 103 configured to generate the primary radar waves R1 and at least one receiver 104 configured to process the secondary radar waves R2 received in return. In a non-limiting embodiment, a single electronic component can be used for both transmission and reception functions. This results in one or more transmitter / receivers, referred to as "transceivers" in English. The transmitter 103 generates primary radar waves R1, which are subsequently emitted by the transmitting antenna 100. When these waves encounter an object 3 (here, a pedestrian in the illustrated non-limiting example) in the external environment of the motor vehicle 2, they are reflected by said object 3. The reflected radar waves are transmitted back to the radar sensor 10. These are the secondary radar waves R2 received by the receiving antennas 101.These are radar waves retransmitted towards the radar sensor 10. In a non-limiting embodiment, the primary radar waves R1 and the secondary radar waves R2 are radio frequency waves. In a non-limiting embodiment, the radar sensor 10 comprises a plurality of transmitters 103 and a plurality of receivers 104.

[0029] The transmitting antenna 100, also called antenna 100, is configured to transmit the primary radar waves R1 generated by the transmitter 103. The receiving antennas 101, also called antennas 101, are configured to receive the secondary radar waves R2 and transmit them to the receiver 104, which then processes them. There is a phase shift between the secondary radar waves R2 received by the receiving antennas 101, which allows the angular position of object 3 relative to the motor vehicle 2 to be deduced. Object 3 is located in the external environment of the motor vehicle 2. In non-limiting embodiments, the antennas 100 and 101 are patch antennas or slot antennas.

[0030] In a non-limiting embodiment, the antennas 100, 101, the transmitter 103 and the receiver 104 are arranged on a printed circuit board 105. In a non-limiting embodiment, the printed circuit board is a rigid printed circuit board, also called a PCBA (Printed Circuit Board Assembly), or a flexible printed circuit board, also called a Flexboard.

[0031] The radar sensor 10 further includes an electronic control unit 106 configured to control the transmitter 103 and the receiver 104. A radar sensor being known to a person skilled in the art, it is not described in more detail here.

[0032] The light module 13 is described below. The light module 13 is configured to perform a signaling function f1. In non-limiting embodiments, said light module 13 is a daytime running light module, or a flashing light, or a reflector, or a high-mounted brake light.

[0033] The light module 13 has an equivalent refractive index neq on the wavelength scale λ of the wavelength range Δ1. It should be noted that n1 can vary due to the optical design of the signaling function f1 (i.e., of layer 15 described below, also called optical layer 15), which means that the equivalent refractive index neq is variable. This must be taken into account in the calculation of the thickness e0 described later.

[0034] As illustrated on the figures 2 et 3 The light module 13 comprises a sublayer 14 and a layer 15 of patterns 150. The sublayer 14 is configured to support the pattern 15 of patterns 150. It is positioned directly opposite the radar sensor 10. It has a refractive index n2. In non-limiting embodiments, the sublayer 14 is made of a plastic, glass, or ceramic material. In one non-limiting example, the plastic is polycarbonate. The pattern 15 of patterns 150 forms a structured sub-wavelength dielectric element. It has a refractive index n1 that depends on the patterns 150 and their spacing, also called the local refractive index n1. The patterns 150 are defined during the optical design to perform the signaling function f1. In non-limiting embodiments, the motifs 150 are used for decoupling light in a visible light guide, or for shaping the beam of light emitted by the light module 13.The patterns 150 are defined to comply with the regulations governing the light beam of the light module 13 and its aesthetic appearance when function f1 is activated. The optical design is therefore imposed without taking into account the presence or absence of the radar sensor 10, specifically to avoid creating multiple versions of the optical layer 15.

[0035] In non-limiting embodiments, the dielectric element is made of a plastic, glass, or ceramic material. In one non-limiting example, the plastic is polycarbonate. It should be noted that a dielectric material is non-conductive and therefore allows radar waves R1 to pass through it, unlike a conductive material. When the radar waves R1 are emitted by the radar sensor 10, they thus first encounter the sublayer 14, then the pattern layer 15, and finally the output glass 12.

[0036] By structured, we mean that layer 15 comprises the 150 motifs, also called structures. By sub-wavelength, we mean that the structured dielectric material is on a scale smaller than the wavelengths λ of the said range Δ1. The fact that the 150 motifs of layer 15 are sub-wavelength allows this layer 15 to be modeled as a variable-index layer. Otherwise, layer 15 would have to be considered a diffractive optical element.

[0037] As illustrated on the figure 4 which is a view of a local area Z1 of the 150 patterns of layer 15, the 150 patterns have dimensions a1 (width), a2 (width), h1 (height). In non-limiting embodiments, the 150 patterns are cylindrical prisms (also called cylindrical pillars), or rectangular prisms (also called rectangular pillars), or pyramidal prisms (also called pyramidal pillars), or cubic prisms (also called square pillars), the latter case being illustrated in the figure 4 , or even portions of tori. They can also have any other parallelepiped shape. In a non-limiting embodiment, a motif 150 comprises dimensions a1, a2 less than 0.4 mm. This value is very small compared to the wavelengths λ of said range Δ1. For example, the wavelength λ is 4 mm for a frequency of 77 GHz; in this case, the value of a1, a2 is approximately equal to λ / 10.

[0038] As illustrated on the figures 3 And 4The layer 15 of motifs 150 is composed of unit cells 152, each comprising a motif 150 and an air portion surrounding said motif 150. In a non-limiting embodiment illustrated in the figure 3 The 150 motifs are contiguous (adjacent) on the boundary surface between layer 15 and sublayer 14. This non-limiting variant is applicable to 150 motifs in the shape of pyramids or portions of tori. A unit cell 152 is defined by the repetition period A of the 150 structures, also called the repetition period A of the 150 motifs or the lattice period A, with A = A1 x A2. A1 is the lattice period along a first direction Ax (illustrated on the figure 4 ), and A2 is the period of the network along a second direction Ay (illustrated on the figure 4 Ax and Ay are arbitrary, non-parallel directions. In a non-limiting embodiment, the second direction Ay is perpendicular to the first direction Ax. In another non-limiting example, the unit cell 152 is a square, a hexagon, a parallelogram, or any other shape that allows the boundary surface between layer 15 and sublayer 14 to be tiled periodically. We will denote Az as a third direction perpendicular to the first direction Ax and the second direction Ay, the whole forming a coordinate system Ax, Ay, Az.

[0039] In a first, non-limiting embodiment, the sub-wavelength structured dielectric element, layer 15, has a constant refractive index n1. It is a sub-wavelength structured periodic dielectric element. The dimensions a1, a2 of the motifs 150 remain constant, and A1 and A2 are also constant. In other words, the motifs 150 are spaced identically from each other along the first direction Ax and are spaced identically along the second direction Ay. That is to say, layer 15 comprises identical spacings 151x along the first direction Ax, and identical spacings 151y along the second direction Ay (illustrated in the figure 4 ) between the 150 patterns, namely there is the same proportion of air between the 150 patterns.

[0040] In a second, non-limiting embodiment, the sub-wavelength structured dielectric element, layer 15, has a variable refractive index n1. In a first, non-limiting embodiment, it is a sub-wavelength structured dielectric element with periodic cells. The dimensions a1, a2 of the motifs 150 change along layer 15, thus varying the refractive index n1 of layer 15, while A1 and A2 remain constant. In a second, non-limiting embodiment, it is a sub-wavelength structured dielectric element with non-periodic cells. A1 and A2 change along layer 15 to vary the refractive index n1 of layer 15, while the dimensions a1, a2 of the motifs 150 may remain constant. Layer 15 includes variable spacings 151x, 151y between patterns 150, namely there are different proportions of air between patterns 150.Thus, in this second non-limiting embodiment variant, A1 and A2 and also the dimensions a1, a2 of the motifs 150 can be varied to vary the refractive index of the layer 15. In a non-limiting example, for motifs 150 in portions of tori, the radii of curvature are variable between the motifs 150. In another non-limiting example, for motifs 150 in the shape of a truncated pyramid, it is the height of truncation that varies.

[0041] By sub-wavelength, we mean that the period of the grating A1, A2 is less than one-quarter of a wavelength in the range Δ1 of wavelengths λ. In a non-limiting example, the wavelength λ considered is the smallest wavelength in the range Δ1. Thus, Λ1 < λ / 4 and Λ2 < λ / 4. In another non-limiting embodiment, the period of the grating A1, A2 is less than one-tenth of the wavelength λ. Thus, A1 < λ / 10 and Λ2 < λ / 10. Note that this wavelength λ is chosen from the range Δ1 and will be used for the formulas below.

[0042] As illustrated on the figure 2 When a radar wave R1 is emitted by the radar sensor 10, it travels to the light module 13, which has a thickness e0. The radar wave R1 arrives at the light module 13 at an angle of incidence θ, corresponding to a refracted angle r. The radar wave R1 is reflected by the light module 13 and generates two reflected waves, one of which, R11, is reflected off the outer surface of the sublayer 14 of the light module 13, and the other inside the light module 13. The two reflected waves, R11 and R12, are first-order reflected waves that return to the radar sensor 10. These are spurious reflections. When the angle of incidence θ is not 0°, the corresponding refracted angle r is also not 0°. The phase difference Δϕ, also called the phase shift Δϕ, between these two reflected waves R11 and R12 is equal to: Δφ = n eq δ λ + π − 2 e 0 tan r sin θ λ

[0043] With : n eq , the equivalent refractive index for sub-layer 14 and layer 15, δ the path of the reflected wave R12 in the material equal to 2e0 / cos(r), nδ / λ the phase shift due to the path in the material, π the phase shift due to internal reflection in sub-layer 14 and layer 15 of motifs 150, - - ((2e0 tan(r) sin(θ)) / λ) 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.

[0044] Since sin(θ) = n eq . sin(r), we obtain: − 2 e 0 tan r sin θ λ = − 2 e 0 n eq sin r 2 λcos r

[0045] Either : Δφ = π + 2 n eq e 0 λcos r 1 − sin r 2 = π + 2 n eq e 0 cos r λ and this is true regardless of the value of the refracted angle r.

[0046] As the reflected waves R11 and R12 return towards the radar sensor 10, they cause disturbances on the radar sensor 10, namely an attenuation of the signal-to-noise ratio. In order to eliminate these disturbances, the total thickness e0 of the light module 13 will be defined such that the reflected waves R11 and R12 are out of phase to create destructive interference. To obtain destructive interference, the phase difference Δϕ between the two reflected waves R11 and R12 must be equal to π modulo 2π. Thus, we have Δϕ = (2m+1)*π, where m is a natural number. We therefore obtain: 2 m + 1 π = π + 2 n eq e 0 cos r λ

[0047] Let: Let e0 = m λ / (2n eq cos (r)).

[0048] It should be noted that the equation e0 = m λ / (2n eq cos (r)) is applied regardless of the value of the angle r. Thus, this total thickness e0 is dimensioned so that it is equal to m times the wavelength λ, divided by twice the equivalent refractive index n eq of the pattern layer 15 and the sublayer 14, times the cosine of a refracted angle r corresponding to the angle of incidence θ of the radar waves R1, where m is an integer. Therefore, from the equivalent refractive index n eq and the wavelength λ used over the operating frequency range of the radar sensor 10, the total thickness e0 can be determined such that the reflected waves R11 and R12 cancel each other out. In a non-limiting embodiment, the wavelength λ used is that which lies in the middle of the allowed range Δ1.

[0049] An ideal total thickness e0 is defined when the angle of incidence θ is equal to 0; and m is equal to 1. When θ = 0, r = 0. Consequently, for m=1, the ideal total thickness e0 of the light module 13 is therefore e0 = λ / (2n eq). When r = 0°, that is, cos(r) = 1.

[0050] In a non-limiting embodiment, the light module 13 has a total thickness e0 that is between 0.8 and 1.2 times the ideal total thickness e0. This range of values ​​takes into account the possible emission angles of the radar sensor 10. It should be noted that the values ​​of the angle of incidence θ are within the possible emission angles of the radar sensor 10. The possible values ​​of the angle of incidence θ are defined in the technical specifications of the radar sensor 10, meaning that the possible values ​​of the angle of incidence θ are within the field of view of the radar sensor 10. In a non-limiting example, the angle of incidence θ is between 0° and ±30°. This range of 0.8 to 1.2 allows for the manufacturing tolerances of the total thickness e0.

[0051] It should be noted that there is a value for the angle of incidence θ for which the reflected radar waves R11 and R12 cause maximum disturbance to the receiving antennas 101 of the radar sensor 10. This angle of incidence θ is called the critical angle of incidence θ. In a non-limiting embodiment, this value is equal to θ = arctan(d1 / (2e4)), where d1 is the distance between the transmitting antenna 100 and the receiving antennas 101, and e4 is the distance between the radar sensor 10 and the light module 13 as illustrated in the figure 2 Note that in a non-limiting example, the midpoint of the receiving antennas 101 is taken to calculate d1.

[0052] Thus, depending on the value of the local refractive index n1 and the wavelength λ used over the operating frequency range of the radar sensor 10 (between 76 GHz and 81 GHz in the non-limiting example), the value of the total thickness e0 can be determined so that the first-order reflected waves R11 and R12 cancel each other out. The reflected radar waves R11 and R12 are reflected by the light module 13 within a limited area.

[0053] It should be noted that when the light module 13 has a variable equivalent refractive index neq, in a non-limiting embodiment, the thickness e0 is adjusted locally on the area of ​​the light module 13 where the equivalent refractive index neq is variable. In this case, the thickness e0 is variable along the surface of the light module 13. Conversely, when the light module 13 has a constant equivalent refractive index neq, the thickness e0 is adjusted for the entire surface of the light module 13. Consequently, the thickness e0 is constant along the surface of the light module 13.

[0054] The light module 13 comprises a total thickness e0 formed by the height h1 of the patterns 150 and the thickness e2 of the sub-layer 14. To dimension the total thickness e0, the thickness e2 of the sub-layer 14 is adjusted so that e0 = m λ / (2n eq cos (r)) for a given r. In this way, the patterns 150 imposed by the optical design are not modified. In a non-limiting embodiment, the given r corresponds to the critical angle of incidence θ.

[0055] As a result, the 101 receiving antennas see less noise. This leads to a better signal-to-noise ratio.

[0056] The equivalent refractive index neq is equal to: n eq = n 1 n 2 e 1 + e 2 n 2 e 1 + n 1 e 2 = n 1 n 2 1 + e 2 e 1 n 2 + n 1 e 2 e 1

[0057] With n1 the local refractive index of the layer 15 of motifs 150, n2 the refractive index of the sublayer 14, e1 equal to the height h1 of motifs 150, and e2 the thickness of the sublayer 14. When the light module 13 has a graded index, it should be noted that n1 is a function of the position of the local zone Z1 of motifs 150 on the layer 15 where the calculation is performed. Thus, the equivalent refractive index neq is a function of the position of the local zone Z1 on the layer 15. When the light module 13 does not have a graded index, the calculation can be performed at any location on the layer 15 of motifs 150, that is to say, at any zone Z1.

[0058] It should be noted that the layer 15 of motifs 150 has a local refractive index n1 which is calculated as a function of the local density τ r of said motifs 150 in the layer 15. The local density τ r at a point of the light module 13 is the weighted average of the filling factor τ r152 of each cell 152 located at a distance from the point considered less than a given value on the order of one of the wavelengths λ of the range Δ1 of wavelengths used.The local refractive index n1, also called the effective refractive index neff, is composed of two effective refractive indices neffTE and neffTM, which depend on the polarization of the incident wave, namely the primary radar wave R1, and which can be expressed as a function of the local density τr, also called the filling factor τr, which represents the portion of matter occupied by the medium with a high refractive index n1, in this case the 150 motifs, as opposed to the medium with a low refractive index n0, in this case air. Note that the local density τr represents the portion of matter occupied by the medium with a high refractive index n1 over an area with a dimension on the order of one of the wavelengths λ of the range Δ1 of wavelengths used. Thus we have: n effTE = ε effTE = τ r ε max + 1 − τ r ε min n effTM = ε effTM = 1 τ r ε max + 1 − τ r ε min

[0059] With the term TE denoting the polarization of the incident wave, namely the radar wave R1 arriving at the light module 13, perpendicular to the plane of the substrate, namely the sublayer 14, TM the polarization parallel to the plane of the substrate, and εmax the permittivity of the medium with the highest refractive index, namely the motifs 150, and εmin for the one with the lowest refractive index, namely air. In another non-limiting embodiment, air can be replaced by a plastic material with a very low refractive index.

[0060] It should be noted that when the incident wave, here the radar wave R1, illuminates the structured dielectric element, namely layer 15, and has a wavelength λ (of said range Δ1) much greater than the repetition period A1, A2 of the structures 150 (λ>>Λ1, and λ>>Λ2), this is a propagation regime called static limit.

[0061] For two-dimensional structures such as those illustrated on the figure 4 The effective refractive index neff2D of a 2D structure can be approximated by taking the root mean square of the effective refractive indices according to the two polarizations TM and TE in one dimension to order 0, which corresponds to the static limit. The filling factor τr152 of a unit cell 152 is, in this particular case: τ r 152 = a 1 . a 2 Λ 1 . Λ 2

[0062] And we have: n eff 2 D = 1 2 n effTE 2 + n effTM 2 1 2

[0063] In the more general case, for any pattern shape 150 where A1, A2 are arbitrary, with a basic rectangular unit cell 152, the filling factor τ r152 for a unit cell 152 will be: τ r 152 = V 152 Λ 1 . Λ 2 . hmax

[0064] This corresponds to a ratio of the volume of material (V 152) in the unit cell 152 to an encompassing empty volume (A1.A2.hmax), with hmax being the maximum height of the motif 150 in the unit cell 152 (i.e., the highest height in the motif 150), and V 152 = ∫ 0 hmax ∫ X 152 X 152 + Λ 1 ∫ Y 152 Y 152 + Λ 2 M X Y Z dXdYdZ

[0065] With (X 152 , Y 152 , 0), the coordinates of a corner C1 of unit cell 152, and M(X, Y, Z) = 1 if the point with coordinates (X, Y, Z) is in the material and M(X, Y, Z) = 0 if it is not, that is, if the point with coordinates (X, Y, Z) is in the air. Note that when it is in the material, the point lies within pattern 150 of unit cell 152, and when it is in the air, the point may or may not be inside a pattern 150 (a pattern 150 may indeed contain air pockets in a non-limiting example). Note that in the non-limiting example of the figure 4 , hmax = h1 described previously.

[0066] Note that this formula for the volume of material V 152 is valid for any unit cell 152 with a rectangular base, regardless of the shape of the pattern 150 in said unit cell 152. Thus, as A1 and A2 can change from one unit cell 152 to another unit cell 152, as well as the maximum height hmax of one pattern 150 to another pattern 150, each unit cell 152 can have a different volume of material and consequently a different filling factor τ r152. To obtain the filling factor τr of the entire layer 15 of motifs 150 at a given point of the light module 13, a weighted average of the filling factors τr152 of each cell 152 located at a distance from the point in question on the light module 13 less than a given value on the order of one of the wavelengths λ of the range Δ1 of wavelengths used is performed. This definition is valid for all points of the light module 13.In a non-limiting embodiment, the points belong to the surface of the sublayer 14 with coordinate Z=0. We thus have: . τ r = ∑ n Λ 1 n . Λ 2 n . hmax n . τ rn ∑ n Λ 1 n . Λ 2 n . hmax n

[0067] Where n denotes any one of the unit cells 152 located at a distance from the point considered on the light module 13 less than a given value on the order of one of the wavelengths λ of the range Δ1 of wavelengths used.

[0068] In a non-limiting embodiment illustrated on the figure 5The light module 13 further comprises a reflective layer 16 in the visible light range and transparent or weakly absorbing for the radar sensor 10 having a refractive index n3 for radar waves. In this case, the total thickness e0 of said light module 13 is equal to m times a wavelength λ of said range divided by twice the equivalent refractive index n eq of said sublayer 14, of said pattern layer 15 150 and of said reflective layer 16 times the cosine of a refracted angle r corresponding to an angle of incidence θ of the radar waves R1, with m an integer. Thus, the total thickness e0 of said luminous module 13 is equal to said wavelength λ divided by twice the equivalent refractive index n eq of said sub-layer 14, of said pattern layer 150 and of said reflective layer 16 for an angle of incidence θ equal to zero.In calculating the equivalent refractive index neq, this reflective layer 16 is taken into account. The preceding calculations must therefore also consider the refractive index n3. The reflective layer 16 covers the pattern layer 15 150. In non-limiting examples, the reflective layer 16 is a layer of indium or reflective paint that covers the pattern 150.

[0069] Of course, the description of the invention is not limited to the embodiments and scope described above. Thus, in another non-limiting embodiment, the radar sensor 10 comprises more than one transmitting antenna 100 and more than two receiving antennas 101. Thus, in a non-limiting embodiment, the light module 13 may comprise more than three layers. Thus, the calculation of the equivalent refractive index neq will take into account all the layers forming the light module 13. Thus, in a non-limiting embodiment, the vehicle assembly 1 further comprises an additional light module configured to perform a lighting function, including a housing. The additional light module is thus a lighting module. In non-limiting examples, said additional light module is a headlight, a taillight, or a fog light.In this configuration, the signal light module 13 and the radar sensor 10 are integrated into the housing of the lighting light module, and the signal light module 13 is positioned next to the lighting light module. It should be noted that integrating the radar sensor 10 behind the signal light module 13, instead of the lighting light module itself, circumvents manufacturers' requirements to reduce the space behind lighting light modules. Lighting light modules are generally significantly larger lengthwise than signal light modules. Therefore, there is often insufficient space to place the radar sensor 10 behind the lighting light module.

[0070] Thus, the described invention offers the following advantages in particular: By integrating the radar sensor 10 behind the signaling light module 13, instead of the bumper, we avoid reducing the performance of the radar sensor 10, it allows the elimination of the reflected waves R11, R12, of order 1 which are reflected towards the radar sensor 10. The signal to noise ratio of said radar sensor 10 is therefore no longer reduced.

Claims

1. Vehicle assembly (1) for a vehicle (2), said vehicle assembly (1) comprising: - a radar sensor (10) configured to emit radar waves (R1) over a range (Δ1) of wavelengths (A); and - a light module (13) configured to perform a signaling function (f1); said light module (13) comprising a sub-layer (14) and a layer (15) of patterns (150), said layer (15) of patterns (150) forming a sub-wavelength structured dielectric element with a repetition period (Λ1, Λ2) of the patterns (150) that is less than a quarter of a wavelength (λ) of said range (Δ1), and characterized in that the total thickness (e0) of said light module (13) is equal to m times a wavelength (λ) of said range, with the whole being divided by twice the equivalent refractive index (neq) of said sub-layer (14) and of said layer (15) of patterns (150), times the cosine of a refracted angle (r) corresponding to an angle of incidence (θ) of the radar waves (R1), where m is an integer.

2. Vehicle assembly (1) according to Claim 1, wherein said radar sensor (11) is a millimeter wave or a hyperfrequency wave or a microwave radar sensor.

3. Vehicle assembly (1) according to the preceding claim, wherein said radar waves (R1) are emitted over a frequency band ranging between 100 MHz and 5 GHz.

4. Vehicle assembly (1) according to any one of the preceding claims, wherein said repetition period (Λ1, A2) of the patterns (150) is less than one tenth of said wavelength (λ) of the radar waves (R1).

5. Vehicle assembly (1) according to any one of the preceding claims, wherein said features (150) are cylindrical prisms, or rectangular prisms, or pyramidal prisms, or cubic prisms, or segments of tori.

6. Vehicle assembly (1) according to any one of the preceding claims, wherein a pattern (150) has dimensions (a1, a2) of less than 0.4 mm.

7. Vehicle assembly (1) according to any one of the preceding claims, wherein said total thickness (e0) is formed by the height (h1) of said patterns (150) and by the thickness (e2) of said sub-layer (14).

8. Vehicle assembly (1) according to the preceding claim, wherein, if the angle of incidence (θ) is equal to zero, then the total thickness (e0) is equal to said wavelength (A) divided by twice the equivalent refractive index (neq).

9. Vehicle assembly (1) according to any one of the preceding claims, wherein the total thickness (e0) is defined with an angle of incidence (θ) equal to arctan(d1 / (2e4)), with e4 being the distance between said radar sensor (11) and said light module (13) and d1 being the distance between an emitter antenna (100) and receiver antennas (101) of said radar sensor (11).

10. Vehicle assembly (1) according to any one of the preceding claims, wherein said light module (13) further comprises a reflective layer (16) and the total thickness (e0) of said light module (13) is equal to m times a wavelength (λ) of said range, with the whole being divided by twice the equivalent refractive index (neq) of said sub-layer (14), of said layer (15) of patterns (150) and of said reflective layer (16), times the cosine of a refracted angle (r) corresponding to an angle of incidence (θ) of the radar waves (R1), where m is an integer.

11. Vehicle assembly (1) according to any one of the preceding claims, wherein the equivalent refractive index (neq) is computed for an angle of incidence (θ) of the radar waves (R1) equal to the center of a field of view (FOV) of said radar sensor (10).

12. Vehicle assembly (1) according to any one of the preceding claims, wherein said light module (13) is a daylight light module, or an indicator light, or a reflector, or a raised stop light.

13. Light module (13) disposed facing a radar sensor (10) configured to emit radar waves (R1) over a range (Δ1) of wavelengths (λ), said light module (13) being configured to perform a signaling function (f1) and comprising a sub-layer (14) and a layer (15) of patterns (150), said layer (15) of patterns (150) forming a sub-wavelength structured dielectric element with a repetition period (A) of the patterns (150) that is less than a quarter of a wavelength (λ) of said range (Δ1), and characterized in that the total thickness (e0) of said light module (13) is equal to m times said wavelength (λ), with the whole being divided by twice the equivalent refractive index (neq) of said sub-layer (14) and of said layer (15) of patterns (150), times the cosine of a refracted angle (r) corresponding to an angle of incidence (θ) of the radar waves (R1), where m is an integer.