Vehicle assembly comprising radar sensor and layered array

Abstract

A vehicle comprises: a radar sensor (10); and a layer arrangement (11) arranged facing the radar sensor and configured to perform an illumination function, the layer arrangement (11) comprising: a first subassembly (S1) of at least one layer (110) that is reflective in the visible range, each layer (110) having a primary refractive index (n10) and a primary thickness (e10); and a second subassembly (S2) of at least one layer (112) that is transparent in the visible range, each layer (112) having a secondary refractive index (n20), the primary refractive index (n10) being high with respect to the secondary refractive index (n20). and the total thickness (e1) of the first subassembly (S1) of the layer (110) is dimensioned such that there is a phase shift of π modulo 2π between the waves (R11) of the radar wave (R1) incident on the outer surface (S1.1) of the first subassembly (S1) and the waves (R12) reflected by the interface (J12) between the first subassembly (S1) and the second subassembly (S2) as they leave the first subassembly.

Description

[Technical Field]

[0001] This invention relates to a vehicle assembly. The invention is applicable to, but is not limited to, an automatic vehicle. [Background technology]

[0002] A vehicle assembly known to those skilled in the art is - A radar sensor configured to transmit radar waves, - A layer array positioned facing the radar sensor, which includes a reflective layer having a higher refractive index for radar waves compared to other layers in the layer array.

[0003] The layered arrangement forms an illuminated logo. Therefore, the radar sensor is positioned behind the illuminated logo, fulfilling the requirement for detecting objects in the external environment of the vehicle.

[0004] One disadvantage of this prior art is that when radar waves are transmitted by the radar sensor, the radar waves propagate through the layer array and are reflected by the layer array. This specifically generates three reflected waves, one of which is reflected by the outer surface of the layer array, and the other two are reflected within the layer array. The three reflected waves are called primary reflected waves and return to the radar sensor. This interferes with the propagation of the radar waves. This reduces the signal-to-noise ratio of the radar sensor, thereby causing disturbances in detection by the radar sensor. The radar sensor loses its detection range. As a result, this can lead to detection errors or non-detection of objects, even when the object is present in the environment outside the vehicle. [Overview of the project] [Problems that the invention aims to solve]

[0005] In this context, the present invention aims to propose a vehicle assembly that can overcome the aforementioned disadvantages. [Means for solving the problem]

[0006] For this purpose, the present invention proposes a vehicle assembly for a vehicle, the vehicle assembly being, - A radar sensor configured to transmit radar waves within a certain range of wavelengths, - A layer array positioned facing the radar sensor and configured to perform an illumination function, the layer array comprising: a first subassembly of at least one layer that is reflective in the visible region, each layer having a primary refractive index and a primary thickness; and a second subassembly of at least one layer that is transparent in the visible region, each layer having a secondary refractive index, wherein the primary refractive index is higher than the secondary refractive index in the radar region; and Equipped with, - The total thickness of the layer of the first subassembly is dimensioned such that there is a phase shift of π modulo 2π between radar waves incident on the outer surface of the first subassembly and waves reflected by the interface between the first subassembly and the second subassembly as they exit the first subassembly. According to a non-limiting embodiment, the vehicle assembly may further include one or more additional features selected from the following, either alone or in any technically possible combination:

[0007] According to one non-limiting embodiment, the total thickness of the layer of the second subassembly is dimensioned such that there is a phase shift of π modulo 2π between the radar waves incident on the outer surface of the first subassembly and the waves reflected by the outer surface of the second subassembly as they exit the first subassembly.

[0008] According to one non-limiting embodiment, the total thickness of the layers of the second subassembly is dimensioned by changing the thickness of only one of the layers of the second subassembly.

[0009] According to one non-limiting embodiment, each layer of the first sub-assembly has a refractive index that differs from the refractive index of another adjacent layer of the first sub-assembly by less than 0.1 in the radar region.

[0010] According to one non-limiting embodiment, each layer of the second sub-assembly has a refractive index that differs from the refractive index of another adjacent layer of the second sub-assembly by less than 0.1 in the radar region.

[0011] According to one non-limiting embodiment, each layer of the second sub-assembly has a refractive index that differs from the refractive index of the layer of the first sub-assembly by more than 0.1 in the radar region.

[0012] According to one non-limiting embodiment, the vehicle assembly includes at least one light source configured to emit visible light that enters the layer arrangement through an edge of one of the layers of the second sub-assembly of the layer arrangement.

[0013] According to one non-limiting embodiment, the at least one layer that is reflective in the visible region is composed of titanium particles.

[0014] According to one non-limiting embodiment, the layer arrangement forms an illuminated logo or an illuminated front-end grill, or forms part of a headlamp.

[0015] According to one non-limiting embodiment, the radar sensor is a millimeter-wave or ultra-high-frequency or microwave radar sensor.

[0016] According to one non-limiting embodiment, the radar wave is transmitted in a frequency band between 100 MHz and 5 GHz.

[0017] According to one non-limiting embodiment, the lighting function is a lighting and / or signaling function.

[0018] According to one non-limiting embodiment, the second subassembly of the layer is - An exit layer that forms an outer exit lens in a layered arrangement, - Protective layer and It is equipped with.

[0019] According to one non-limiting embodiment, the first subassembly of the layer is a diffuse reflective white subassembly.

[0020] According to one non-limiting embodiment, the total thickness of the first subassembly is determined for an incident angle equal to arctan(d1 / (2e4)), where e4 is the distance between the radar sensor and the layer array, and d1 is the distance between the transmitting antenna and the receiving antenna of the radar sensor.

[0021] The present invention further proposes a layer array positioned facing a radar sensor, wherein the radar sensor is configured to transmit radar waves of a certain range of wavelengths, and the layer array is configured to perform an illumination function, comprising: a first subassembly of at least one layer reflective in the visible region, each layer having a primary refractive index and a primary thickness; and a second subassembly of at least one layer transparent in the visible region, each layer having a secondary refractive index, wherein the primary refractive index is high relative to the secondary refractive index in the radar region. - The total thickness of the first subassembly of the layer is sized such that there is a phase shift of π modulo 2π between the radar waves incident on the outer surface of the first subassembly and the waves reflected by the interface between the first subassembly and the second subassembly as they exit the first subassembly.

[0022] The present invention and its various applications will be better understood by reading the following description and examining the attached figures. [Brief explanation of the drawing]

[0023] [Figure 1] This is a schematic diagram of a vehicle assembly according to one non-limiting embodiment of the present invention, wherein the vehicle assembly comprises a radar sensor and a layer array, and the layer array comprises a first subassembly of a layer and a second subassembly of a layer. [Figure 2] Figure 1 is a front view of a vehicle assembly according to one non-limiting embodiment, the vehicle assembly further includes a light decoupling relief according to one non-limiting embodiment. [Figure 3] This is a schematic diagram of radar waves transmitted by a radar sensor in the vehicle assembly of Figure 1 or Figure 2, according to one non-limiting embodiment, the radar waves generate reflected waves that are reflected from one face of the layer array of the vehicle assembly of Figure 1 or Figure 2 and within the layer array. [Figure 4] This is a schematic diagram of radar waves transmitted by a radar sensor of the vehicle assembly in Figure 1 or Figure 2, according to one non-limiting embodiment, where the radar waves generate reflected waves that are reflected by two faces of the layered array of the vehicle assembly in Figure 1 or Figure 2. [Figure 5] Figure 1 or 2 is a schematic diagram of the layers of a layer arrangement of a vehicle assembly according to one non-limiting embodiment, the layer arrangement comprising a first subassembly of layers and a second subassembly of layers. [Figure 6] The first graph of results shows two reflectance curves related to radar waves from the radar sensor in Figure 1 when, according to one non-limiting embodiment, a second subassembly of the layer array in Figure 1 is optimized to minimize the reflected waves in Figure 3. [Figure 7] The first graph of results shows two reflectance curves related to radar waves from the radar sensor in Figure 1, in one non-limiting embodiment, where a second subassembly of the layer array in Figure 1 is optimized to minimize the reflected waves in Figure 3, and a first subassembly of the layers of the layer array in Figure 1 is optimized to minimize the reflected waves in Figure 4. [Modes for carrying out the invention]

[0024] Elements that have the same structure or function and appear in several figures shall use the same reference numerals unless otherwise specified.

[0025] A vehicle assembly 1 of a vehicle 2 according to the present invention will be described with reference to Figures 1 to 7. The vehicle assembly 1 is also called the vehicle system 1. In one non-limiting embodiment, the vehicle 2 is an automatic vehicle. The term automatic vehicle means any type of engine-powered vehicle. This embodiment is given as a non-limiting example for the remainder of the description. Thus, for the remainder of the description, the vehicle 2 is also called the automatic vehicle 2. In one non-limiting embodiment, the vehicle assembly 1 is positioned in the grille of the automatic vehicle 2. In another non-limiting embodiment, the vehicle assembly 1 may be incorporated into a body portion located at the rear of the automatic vehicle 2.

[0026] As shown in Figure 1, the vehicle assembly 1 is also called the vehicle device 1. - A radar sensor 10 configured to transmit radar waves R1, - Layer array 11 arranged facing the radar sensor 10 and It is equipped with.

[0027] These elements are explained below.

[0028] The radar sensor 10 is described below. As shown in Figure 1, the radar sensor 10 is positioned facing the layer array 11. In one non-limiting embodiment, the radar sensor 10 is a millimeter-wave (between 24 GHz and 300 GHz) or ultra-high frequency (between 300 MHz and 81 GHz) or microwave (between 1 GHz and 300 GHz) radar sensor. In one non-limiting variation, the radar sensor 10 operates at radar frequencies between 76 GHz and 81 GHz. The radar wave R1 is transmitted in the wavelength range Δ1 of λ. In one non-limiting embodiment, the radar wave R1 is transmitted in the frequency band between 100 MHz and 5 GHz. In one non-limiting example, if the radar sensor 10 operates at a radar frequency of 77 GHz, i.e., in the frequency band of 1 GHz at a wavelength λ of 3.95 mm, then the radar sensor 10 operates in the frequency band of 76.5 GHz to 77.5 GHz. Therefore, the radar wave R1 will be transmitted in the frequency range of 76.5 GHz to 77.5 GHz, that is, in the wavelength range Δ1 of 3.87 mm to 3.92 mm. In another non-limiting example, if the radar sensor 10 operates in the 5 GHz frequency band at a radar frequency of 78.5 GHz, then the radar sensor 10 will operate in the frequency band of 76 GHz to 81 GHz. Therefore, the radar wave R1 will be transmitted in the frequency range of 76 GHz to 81 GHz, that is, in the wavelength range Δ1 of 3.701 mm to 3.945 mm.

[0029] As shown in Figures 3 and 4, the transmitted radar wave R1 strikes the layer array 11 at an incident angle θ. In one non-limiting embodiment, the incident angle θ is between 0° and ±30°. Thus, the radar sensor 10 has 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 Ox of the vehicle, also called the vehicle axis Ox. 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 vehicle axis Ox, and the incident angle θ of the radar wave R1 to the layer array 11 remains close to 0° (in which case the vehicle assembly 1 is positioned at approximately 45° with respect to the vehicle axis Ox).

[0030] The radar sensor 10 is configured to scan the environment outside the automatic vehicle 2 by transmitting radar waves R1. Therefore, as shown in Figure 1, the radar sensor 10, - At least one transmitting antenna 100 configured to transmit radar wave R1, also called primary radar wave R1, - At least two receiving antennas 101 configured to receive radar waves R2, also called secondary radar waves R2 or return radar waves R2, It is equipped with.

[0031] The radar sensor 10 further comprises at least one transmitter 103 configured to generate a primary radar wave R1 and at least one receiver 104 configured to process a secondary radar wave R2 that is received back. In one non-limiting embodiment, a single electronic component may be used for both the transmitting and receiving functions. Thus, one or more transceivers will be present. The transmitter 103 generates a primary radar wave R1, which is subsequently transmitted by the transmitting antenna 100, and when the primary radar wave R1 encounters an object 3 (here, a pedestrian in the non-limiting example shown) in the environment outside the automatic vehicle 2, the object 3 is reflected. The radar wave thus reflected is the wave transmitted back to the radar sensor 10. The reflected radar wave is the secondary radar wave R2, which is received by the antenna 101. The reflected radar wave is the radar wave transmitted back to the radar sensor 10. In one non-limiting embodiment, the primary radar wave R1 and the secondary radar wave R2 are high frequencies. In one non-limiting embodiment, the radar sensor 10 comprises a plurality of transmitters 103 and a plurality of receivers 104.

[0032] A transmitting antenna 100, also called antenna 100, is configured to transmit a primary radar wave R1 generated by a transmitter 103. A receiving antenna 101, also called antenna 101, receives a secondary radar wave R2 and transmits the secondary radar wave R2 to a receiver 104, which is configured to then process the secondary radar wave R2. There is a phase shift between the secondary radar waves R2 received by the receiving antenna 101, which allows for the estimation of the angular position of an object 3 relative to the automatic vehicle 2, where the object 3 is located in the environment outside the automatic vehicle 2. In non-limiting embodiments, antennas 100, 101 are patch antennas or slot antennas.

[0033] In one non-limiting embodiment, antennas 100, 101, transmitter 103, and receiver 104 are arranged on a printed circuit board 105. In one non-limiting embodiment, the printed circuit board is a printed circuit board assembly (PCBA) or a flexible printed circuit board (flexboard).

[0034] The radar sensor 10 further comprises an electronic control unit 106 configured to control a transmitter 103 and a receiver 104. Such radar sensors are known to those skilled in the art and will not be described in further detail here.

[0035] The layer arrangement 11 is described below. As shown in Figure 1 or Figures 3-5, the layer arrangement 11 is - A first subassembly S1 comprising at least one layer 110 that is reflective in the visible region, - At least one second subassembly S2 of layer 112 and It is equipped with.

[0036] The layer array 11 is configured to perform an illumination function. The first subassembly S1 and the second subassembly S2 work together to perform the illumination function. In one non-limiting embodiment, the illumination function is a lighting and / or signal transmission function. It is a so-called adjustable illumination function.

[0037] Please note that Figure 1 is a schematic diagram, and therefore only the two layers 110 and the two layers 112 are shown in Figure 1. For the remainder of this explanation, the first subassembly S1 of layer 110 will also be called the first subassembly S1, and the second subassembly S2 of layer 112 will also be called the second subassembly S2.

[0038] In non-limiting embodiments, the layer array 11 forms an illuminated logo or an illuminated front-end grille or forms part of a headlamp. In these cases, the vehicle assembly 1 comprises one or more light sources 12. Thus, the logo or front-end grille or the isolated relief structure 13 (described later) is illuminated by multiple light sources 12. Thus, in one non-limiting embodiment, the vehicle assembly 1 comprises at least one light source 12 configured to emit visible light Lx, also called light, which enters the layer array 11 through its edges. In the non-limiting example shown in Figure 2, the light source 12 is positioned around the layer array 11 at the same height as the layer 112 of a second subassembly S2. In this non-limiting example, the array 11 forms part of a headlamp 5 further comprising a lighting module 50 having one or more light sources (not shown).

[0039] The light source 12 generates a light ray (not shown), producing light Lx, which is injected into the transparent layer 112 and reflected by at least one of the layers 110. Note that one of the transparent layers 112 is configured to function as a light guide for the light Lx, while the other layer 112 is a styling or protective layer (for corrosion protection in one non-limiting example).

[0040] In one non-limiting embodiment, the light source 12 is a semiconductor light source. In one non-limiting embodiment, the semiconductor light source forms part of a light-emitting diode. In non-limiting examples, light-emitting diode means any type of light-emitting diode, whether or not it is an LED, OLED (organic LED), AMOLED (active-matrix organic LED), or even FOLED (flexible OLED). In another non-limiting embodiment, the light source 12 is a light bulb having a filament.

[0041] As shown in Figure 1, the first subassembly S1 of layer 110 is positioned facing the radar sensor 10, while the second subassembly S2 of layer 112 is adjacent to the first subassembly S1 of layer 110 and is positioned facing the outside of the automatic vehicle 2.

[0042] In a first non-limiting embodiment, the first subassembly S1 is a diffuse reflective subassembly, i.e., at least one layer 110 is diffuse and reflective, and the second subassembly S2 is transparent in the visible region, i.e., layer 112 is transparent to visible light.

[0043] In a second non-limiting embodiment, the first subassembly S1 is a visible-transparent subassembly having a light-separating relief structure 13, i.e., at least one layer 110 is transparent to visible light and comprises the light-separating relief structure 13, and the second subassembly S2 is transparent to visible light, i.e., layer 112 is transparent to visible light.

[0044] The light separation relief structure 13 is configured to separate the light Lx generated by the light source 12. The relief 130 of the light separation relief structure 13 is a local modification of the relief of the surface on which it is located, i.e., in this case, one of the reliefs of the layer 110 facing the radar sensor 10.

[0045] It should be noted that if layer 110 is a diffuse reflective white layer, light Lx does not propagate through this layer 110 but is sent directly to the outside of the automatic vehicle 2 by the light separation relief structure 13. The light separation relief structure 13 is positioned to send light Lx along the vehicle axis Ox of the automatic vehicle 2, thereby enabling it to perform an illumination function. In a non-limiting embodiment, the light separation relief structure 13 is a plurality of - Minidiscs, also known as microlenses, obtained by laser shock, and / or - Microcones, and / or - Micro-cone prism, and / or - Mini prism, and / or - Embossing It is equipped with.

[0046] Therefore, the relief 130 is a minidisk and / or microcone, and / or microcone prism and / or miniprism and / or embossing. Such surfaces are often described as diffusing surfaces or microlensing surfaces.

[0047] The first subassembly S1 of the layers is configured to direct light Lx generated by the light source 12 toward the outside of the automatic vehicle 2. Each layer 110 of the first subassembly S1 has a primary refractive index n10, also called refractive index n10, and a primary thickness e10, also called thickness e10. The first subassembly S1 has a total thickness e1, which is made up of all thicknesses e10. Each layer 110 has a refractive index n10 that is very close to the refractive index n10 of another adjacent layer 110, and is also called continuous. In one non-limiting embodiment, each layer 110 has a refractive index n10 that differs from the refractive index n10 of an adjacent layer 110 of the first subassembly S1 by less than 0.1. This threshold further allows internal reflected waves between the layers 110 of the first subassembly S1 to be ignored. In one non-limiting variation of this non-limiting embodiment, the difference is less than 0.05.

[0048] The second subassembly S2 of the layer is configured to propagate visible light Lx within the layer 112, thereby enabling increased efficiency of the illumination function. Each layer 112 of the second subassembly S2 has a secondary refractive index n20, also called refractive index n20, and a secondary thickness e20, also called thickness e20. The second subassembly S2 has a total thickness e2, which is comprised of all thicknesses e20. Each layer 112 has a refractive index n20 that is very close to the refractive index n20 of the adjacent layer 112, and is also called continuous. In one non-limiting embodiment, each layer 112 has a refractive index n20 that differs from the refractive index n20 of the adjacent layer 112 of the second subassembly S2 by less than 0.1. This threshold further allows internal reflections between the layers 112 of the second subassembly S2 to be ignored. In the non-limiting example shown, the second subassembly S2 comprises two layers 112a and 112b, namely, layer 112a acting as an optical guide for light Lx, and layer 112b being a protective layer. The exit layer 112a has a secondary refractive index n20a that differs from the secondary refractive index n20b of the adjacent protective layer 112b by less than 0.1 in the radar region. In one non-limiting variation of this non-limiting embodiment, the difference is less than 0.05. In the non-limiting example shown, the secondary refractive index n20a is equal to 1.6 and the secondary refractive index n20b is equal to 1.62.

[0049] Therefore, the layer arrangement 11 has a total thickness e0 = e1 + e2, as shown in Figure 5.

[0050] The primary refractive index n10 is higher than the secondary refractive index n20 in the radar region. "Higher" means that layer 110 and layer 112 cannot be considered equivalent layers. In one non-limiting embodiment, therefore each layer 112 of the second subassembly S2 has a refractive index n20 that differs from the refractive index n10 of layer 110 of the first subassembly S1 by more than 0.1. Thus, there is a refractive index difference of more than 0.1 in the radar region.

[0051] In one non-limiting embodiment shown in Figure 5, the first subassembly S1 of layer 110 comprises a single layer 110. In one non-limiting embodiment, layer 110 is a layer of white reflective material. Thus, the first subassembly S1 of layer 110 is a diffuse reflective white layer. This allows for maximizing the efficiency of the light source 12, otherwise half of the visible light Lx would be lost. In one non-limiting variation, the material is composed of titanium TiO2 particles. In one non-limiting example, it is a plastic with titanium oxide dopant. Note that the more titanium oxide doping there is, the greater the optical reflectivity of the material, and therefore the higher the refractive index in the radar region. In one non-limiting embodiment, the doped plastic is PC (polycarbonate). Titanium doping is, - Unlike paint coatings, it uses a well-controlled process that allows for uniform distribution on large parts such as front-end grilles. - And, unlike paint coatings, it allows for changing the reflectivity, thereby enabling control of the refractive index. It has the advantage of the titanium oxide-doped plastic layer 110 contributing to the performance of the illumination function. Furthermore, it should be noted that titanium allows for the protection of the titanium-doped plastic. Layer 110 is transparent to radar waves R1, R2 but not to visible light Lx; that is, visible light Lx is largely reflected by layer 110 (particularly by the interface J12 described below), so layer 110 allows radar waves R1 to pass through but not visible light Lx. In one non-limiting embodiment, its thickness e10 is several millimeters. In one non-limiting embodiment, the primary refractive index n10 of this layer 110 is equal to 2. It should be noted that the higher the concentration of titanium TiO2 particles, the higher the reflectivity of layer 110 and the higher the primary refractive index n10. This non-limiting embodiment of a single layer 110 is provided as a non-limiting example for the remainder of the description.

[0052] In one non-limiting embodiment shown in Figure 5, the second subassembly S2 of layer 112 is - An exit layer 112a that forms the outer exit lens of the layer array 11, - A protective layer 112b that prevents yellowing of the plastic of the outer exit lens 112a by blocking ultraviolet light, It is equipped with.

[0053] In one non-limiting embodiment, the protective layer 112b may also be a scratch-resistant layer. In one non-limiting embodiment, the exit layer 112a is made of PC. It is a layer that is transparent to both radar waves R1, R2 and visible light Lx. In one non-limiting embodiment, the protective layer 112b has a thickness e20b of substantially 50 micrometers. In one non-limiting embodiment, the protective layer 112b is a deposit of protective varnish.

[0054] As shown in Figures 3 to 5, when radar wave R1 is transmitted by radar sensor 10, radar wave R1 travels to layer array 11. Radar wave R1 is reflected by layer array 11, resulting in four reflected waves R11, R12, R13, and R14, i.e., - R11, the wave reflected by the outer surface S1.1 of the first subassembly S1, - R12, within the layer array 11, the wave reflected by the interface J12 between the first subassembly S1 and the second subassembly S2, - R13 (shown in Figure 5(a)), within the layer array 11, the wave reflected by the interface J22 between the two layers 112a and 112b of the second subassembly, - R14, wave reflected from the outer surface S2.1 of the second subassembly S2. This will cause it to occur.

[0055] It should be noted that the reflected waves R12, R13, and R14 include incident portions that pass through layers 110 for R12, 110 and 112a for R13, and 110, 112a, and 112b for R14 before reflection.

[0056] In other words, there are waves reflected by each refractive surface defined between two different adjacent layers. The four reflected waves R11-R14 are called primary reflected waves and return to the radar sensor 10. These are parasitic reflections that disrupt the radar wave R1. The radar wave R1' is the radar wave leaving the layer array 11 and is shown in Figures 3 and 4. Due to these parasitic reflections, the radar wave R1 is attenuated significantly compared to the radar wave R1 entering the layer array 11. Consequently, the efficiency of the radar sensor 10 decreases. To overcome this problem, the thickness e1 and then e2 are successively optimized, as can be seen below.

[0057] The reflection intensity differs for each reflected wave. In the non-limiting example shown, the difference in refractive index between n20a and n20b is extremely small, and therefore Fresnel reflection can be ignored, so the reflection intensity of R13 is negligible. Its reflection intensity is less than 0.5% for radar wave R1, but the reflection intensities of reflected waves R11, R12, and R14 vary between 3% and 8% in one non-limiting example. Reflected wave R13 has little effect on the transmission of radar wave R1, but reflected waves R11, R12, and R14 disturb radar wave R1.

[0058] When the first subassembly of layer 110 comprises multiple layers 110, if each layer 110 has a refractive index n10 that is very close to the refractive index n10 of another adjacent layer 110, in other words, if they are continuous, then all the layers 110 of the first subassembly S1 have an equivalent refractive index n eq1 It should be noted that this can be considered equivalent to a single equivalent layer of total thickness e1 having (as shown in Figures 1, 3, and 4). Recall that in a given non-limiting example, the refractive index difference is less than 0.1.

[0059] When each layer 112 has a refractive index n20 that is very close to the refractive index n20 of another adjacent layer 112, in other words, when they are continuous, then all of the layers 112 of the second subassembly S2 have an equivalent refractive index n eq2It should be noted that this can be considered equivalent to a single equivalent layer of total thickness e2 having (as shown in Figures 1, 3, and 4). Recall that in a given non-limiting example, the refractive index difference is less than 0.1.

[0060] It should be noted that these two secondary refractive indices n20a and n20b are quite far from the primary refractive index n10 in terms of their values. There is a large leap in refractive index. Therefore, this is not true except when layer 110 has a thickness e10 that is significantly smaller than the radar wave R1 and negligible compared to the thickness e2 of layer 112. Significantly smaller means e10 = λ / 10.

[0061] In addition, since n10 is significantly larger than n20, an equivalent refractive index cannot exist between the two subassemblies S1 and S2.

[0062] Note that while an equivalent refractive index may exist if n10 is very close to or equal to n20, this is not the case here. Due to the large jump in refractive index between n10 and n20, it is not possible for an equivalent refractive index to exist between the first subassembly S1 and the second subassembly S2, nor is it possible to optimize the thickness e0.

[0063] Conversely, as shown in Figures 1, 3, and 4, the second subassembly S2 has an equivalent refractive index n equal to the following: eq2 It holds.

number

[0064] The same principle applies to the first subassembly S1 if it includes multiple layers 110 having very similar refractive indices n10. eq1 It will have the following properties. Note that the refractive index n can be calculated from the dielectric constant of the layer. This calculation is known to those skilled in the art and will not be explained here.

[0065] Equivalent refractive index n eq2 In the calculation, the reflected wave R13, which has a very low reflectance and can therefore be ignored, is no longer taken into consideration. Thus, as shown in Figure 5(b), the reflected waves R11, R12, and R13 continue to interfere with the radar sensor 10. Thus, the radar wave R1 is reflected by the layer array 11, generating three reflected waves R11, R12, and R13 with high reflectances, i.e., most of their energy returns to the radar sensor 10. In this case, the reflectance values ​​are equal to the following:

number

[0066] The minimum reflection intensity value I(M) is obtained when the different layers of the two subassemblies S1 and S2 are optimized, resulting in them separately causing a phase shift of π modulo 2π, and consequently, destructive interference exists between terms R11 and R14, and between R11 and R12. Therefore, in order to minimize the parasitic waves R11, R12, and R14, R11 and R12 must be in opposite phases to create destructive interference, and R11 and R14 must also be in opposite phases to create destructive interference. In this way, the maximum reflection, i.e., the interference phenomenon by R11 and R14, is optimized. It should be noted that although terms R12 and R14 remain in constructive phase, this has significantly less influence than the sum of the other two terms, since terms R12 and R14 have lower intensities than terms R11 and R14 and terms R11 and R12.

[0067] For this purpose, in order to reduce parasitic waves and improve the transmission of radar wave R1, layer 112 of the second subassembly S2 can be considered an equivalent layer when the refractive index difference between different layers 112 is small, so this equivalent layer is sized to have a phase shift of π modulo 2π between R11 and R14. Conversely, if there is a large refractive index difference between two consecutive layers, they cannot be considered equivalent layers. This is the case with layer 110 and the equivalent layer formed by layers 112a and 112b. In this case, each non-equivalent layer must be optimized separately to reduce parasitic waves and improve the transmission of radar wave R1. In this case, each non-equivalent layer must cause a phase shift of π modulo 2π.

[0068] The method by which destructive interference is achieved between R11 and R12 will be described next. As will be discussed later, the thickness e1 is optimized for this purpose.

[0069] The total thickness e1 of the first subassembly S1 of layer 110 is sized such that there is a phase shift of π modulo 2π between R11 and R12. In other words, the total thickness e1 of the first subassembly S1 of layer 110 is sized such that there is a phase shift of π modulo 2π between wave R11 of the radar wave R1 incident on the outer surface S1.1 of the first subassembly S1 and wave R12 reflected by the interface J12 between the first subassembly S1 and the second subassembly S2 as they exit the first subassembly S1.

[0070] If the angle of incidence θ is different from 0°, the corresponding angle of refraction r is also different from 0°.

[0071] The phase difference Δφ, also called the phase shift Δφ, between these two reflected waves R11 and R12 is equal to the following:

number

[0072] sin(θ)=n eq1 Since it is ×sin(r), the following is obtained.

number

number

[0073] Considering that the reflected waves R11 and R12 return to the radar sensor 10, they cause disturbances in the radar sensor 10, i.e., attenuation of the signal-to-noise ratio. To eliminate these disturbances, the total thickness e1 of the first subassembly S1 is 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, Δφ = (2m + 1) * π, where m is a natural integer. Hence, we obtain:

number

[0074] Note that for any value of the angle r, the formula e1 = mλ / (2n eq1 cos(r)) is applicable. Thus, this total thickness e1 is equal to m times the wavelength λ of the range Δ1, and the whole is divided by multiplying by the cosine of the refraction angle r corresponding to the incident angle θ of the radar wave R1 by twice the equivalent refractive index n eq1 of 2, where m is an integer. Thus, from the equivalent refractive index n eq1 and the wavelength λ used in the operating frequency range of the radar sensor 10, the total thickness e1 of the first sub-assembly S1 can be determined such that the reflected waves R11 and R12 cancel each other out. In one non-limiting embodiment, the selected wavelength λ is located at the center of the range Δ1.

[0075] The ideal total thickness e1 is defined when the incident angle is equal to 0 and m is equal to 1. When θ = 0, r = 0. As a result, for m = 1, the ideal total thickness e1 of the first sub-assembly S1 is, therefore, when r = 0°, i.e., cos(r) = 1, e1 = λ / (2n eq1 ). In other words, here, in a non-limiting example of a single layer, e1 = λ / (2n10).

[0076] Thus, the total thickness e1 is adapted to obtain the ideal total thickness e1 = λ / (2n eq1 ) when θ = 0, or to obtain e1 = mλ / (2n eq1 cos(r)) when θ ≠ 0.

[0077] In one non-limiting embodiment, the first subassembly S1 of the layer has a total thickness e1 between 0.8 and 1.2 times the ideal total thickness e1. This range of values ​​takes into account the possible emission angles of the radar sensor 10. The possible values ​​of the incident angle θ are defined in the technical specifications of the radar sensor 10, which means that the possible values ​​of the incident angle θ are the field of view of the radar sensor 10. In one non-limiting example, the incident angle θ is between 0° and ±30°. This range of values ​​from 0.8 to 1.2 allows for taking into account manufacturing tolerances for the total thickness e0. In a given non-limiting example, it should be noted that the thickness e10 of the layer 110 of the white reflective material composed of titanium TiO2 particles is easy to control with respect to the industrial process involved.

[0078] It should be noted that there exists an incidence angle θ such that the reflected radar waves R11 and R12 cause the greatest disturbance in the receiving antenna 101 of the radar sensor 10. This incidence angle θ is called the 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 transmitting antenna 100 and the receiving antenna 101, and e4 is the distance between the radar sensor 10 and the layer array 11, as shown in Figure 3. Thus, in one non-limiting embodiment, the value of the total thickness e1 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 receiving antenna 101 is used to calculate d1.

[0079] Therefore, the total equivalent refractive index n eq1 Depending on the value of and the wavelength λ used in the operating frequency range of the radar sensor 10 (between 76 GHz and 81 GHz in a given non-limiting example), it is possible to determine the value of the total thickness e1 such that the primary reflected waves R11 and R12 cancel each other out. Thus, the receiving antenna 101 experiences less noise, and a better signal-to-noise ratio is achieved.

[0080] Due to the optimization of thickness e1, and because layers 110 and 112 are parallel to each other, the paths of the radar wave R1 and the reflected wave R14 within thickness e1 are the same, and therefore, the radar wave R1 and the reflected wave R14 strike interfaces S1.1 and J1.2, respectively, at the same angle of incidence. Furthermore, there is therefore a phase shift equal to π modulo 2π between the incident portion of the reflected wave R14 passing through the first subassembly S1 (i.e., layer 110) on the outward path and the portion of the reflected wave R14 passing through the first subassembly (i.e., layer 110) on the return path. Therefore, these two portions cancel each other out. Subsequently, it is sufficient that there is destructive interference between the reflected waves R11 and R14 in the second subassembly S2. The method by which destructive interference is achieved between R11 and R14 will be described next. For this purpose, as will be described later, thickness e2 is optimized (after thickness e1 has been optimized).

[0081] The total thickness e2 of the second subassembly S2 of layer 112 is dimensioned such that there is a phase shift of π modulo 2π between R11 and R14. In other words, the total thickness e2 of the second subassembly S2 of layer 112 is dimensioned such that there is a phase shift of π modulo 2π between wave R11 of the radar wave R1 incident on the outer surface S1.1 of the first subassembly S1 and wave R14 reflected by the outer surface S2.1 of the second subassembly S2 as they exit the first subassembly S1.

[0082] If the angle of incidence θ is different from 0°, the corresponding angle of refraction r is also different from 0°.

[0083] The phase shift Δφ between the two reflected waves R11 and R14, also known as the phase difference Δφ, is equal to the following:

number

[0084] sin(θ)=n eq2 Since it is ×sin(r), the following is obtained.

number

number

[0085] Considering that the reflected waves R11 and R14 return to the radar sensor 10, they cause disturbances in the radar sensor 10, i.e., attenuation of the signal-to-noise ratio. To eliminate these disturbances, the total thickness e2 of the second subassembly S2 will be defined such that the reflected waves R11 and R14 are out of phase to create destructive interference. To obtain destructive interference, the phase difference Δφ between the two reflected waves R11 and R14 must be equal to π modulo 2π. Thus, Δφ = (2m + 1) * π, where m is a natural integer. Hence, we obtain:

number

[0086] For any value of angle r, the formula e2 = mλ / (2n eq2Note that cos(r) is applied. Therefore, this total thickness e2 is equal to m times the wavelength λ in the range Δ1, and the whole is equal to the equivalent refractive index n of the second subassembly S2 of layer 112. eq2 The dimensions are set so that the result is divided by twice the value multiplied by the cosine of the refraction angle r corresponding to the incident angle θ of the radar wave R1, where m is an integer. Therefore, the equivalent refractive index n eq2 Based on the wavelength λ used in the operating frequency range of the radar sensor 10, the total thickness e2 of the second subassembly S2 can be determined such that the reflected waves R11 and R14 cancel each other out. In one non-limiting embodiment, the selected wavelength λ is located in the middle of the range Δ1.

[0087] The ideal total thickness e2 is defined when the angle of incidence is equal to 0 and m is equal to 1. When θ=0, r=0. Consequently, when m=1, therefore the ideal total thickness e2 of the second subassembly S2 is e2=λ / (2n eq2 ) . When r=0°, it is cos(r)=1.

[0088] Therefore, the total thickness e2 is ideal when θ=0: e2=λ / (2n eq2 ) so as to obtain, or when θ≠0 e2=mλ / (2n eq2 The adjustment will be made to obtain cos(r). Adjusting the total thickness e2 does not change the optical performance of the illuminated logo.

[0089] Therefore, the total thickness e2 of the second subassembly S2 of layer 112 is such that, at an incident angle θ equal to zero, the total thickness e2 is such that the wavelength λ corresponds to the equivalent refractive index n of the second subassembly S2 of layer 112. eq2 The dimensions are set so that they are equal to the result of dividing by twice the value. When the angle of incidence θ is not zero, e² = mλ / (2n eq2 The formula cos(r) is obtained. This formula applies to any value of angle r.

[0090] In one non-limiting embodiment, to optimize e2, the thickness of only one of the layers 112 of the second subassembly S2 is changed. This simplifies the optimization process. In one non-limiting embodiment, the layer into which the light Lx is injected acts as an optical guide for the modified light Lx. It should be noted that, in practice, the thickness e20a of the exit layer 112a will be adjusted. The protective layer 112b is already very thin, so its thickness e20b cannot be adjusted. Thus, in practice, the thickness e20 of only one layer 112, i.e., the layer that is easiest to inject or the layer made of the cheapest material, is adjusted.

[0091] In one non-limiting embodiment, the second subassembly S2 has a total thickness e2 between 0.8 and 1.2 times the ideal total thickness e2. This range of values ​​takes into account the possible emission angles of the radar sensor 10. The possible values ​​of the incident angle θ are defined in the technical specifications of the radar sensor 10, which means that the possible values ​​of the incident angle θ are the field of view of the radar sensor 10. In one non-limiting example, the incident angle θ is between 0° and ±30°. This range of values ​​from 0.8 to 1.2 allows for taking into account the manufacturing tolerance of the total thickness e2.

[0092] It should be noted that there exists an incidence angle θ such that the reflected radar waves R11 and R14 cause the greatest disturbance in the receiving antenna 101 of the radar sensor 10. This incidence angle θ is called the critical angle θ. In one 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 antenna 101, and e4 is the distance between the radar sensor 10 and the layer array 11, as shown in Figure 4. Thus, in one non-limiting embodiment, the value of the total thickness e2 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 receiving antenna 101 is used to calculate d1.

[0093] Therefore, the total equivalent refractive index n eq2Depending on the value of and the wavelength λ used in the operating frequency range of the radar sensor 10 (between 76 GHz and 81 GHz in a given non-limiting example), it is possible to determine the value of the total thickness e2 such that the primary reflected waves R11 and R14 cancel each other out. Thus, the receiving antenna 101 experiences less noise, and a better signal-to-noise ratio is achieved.

[0094] Figure 6 shows a graph of the results after optimizing the second subassembly S2 of the layer array 11 to minimize the effects of reflected waves R11 and R14 on the radar wave R1, but without optimization of the first subassembly S1 of the layer array 11, the effects of reflected waves R11 and R12 on the radar wave R1 still exist. Therefore, R11 and R14 produce destructive interference between them, while R11 and R12 produce constructive interference between them. The incidence angle θ is shown on the x-axis, and the reflected intensity IRL in decibels (dB) is shown on the y-axis. There are two curves C1 and C2 for two incidence angles θ at 76 GHz and 77 GHz, respectively.

[0095] Figure 7 shows a graph of the results after optimizing the second subassembly S2 of the layer array 11 to minimize the influence of reflected waves R11 and R14 on the radar wave R1, and optimizing the first subassembly S1 of the layer array 11 to minimize the influence of reflected waves R11 and R12 on the radar wave R1. Thus, R11 and R14 generate destructive interference between them, and R11 and R12 further generate destructive interference between them. The incident angle θ is shown on the x-axis, and the reflected intensity IRL in decibels (dB) is shown on the y-axis. There are two curves C1 and C2 for two incident angles θ of 76 GHz and 77 GHz, respectively.

[0096] In the graph in Figure 6, when only the disturbances from reflected waves R11 and R14 are processed, the average reflection intensity (IRL) is -10 dB. However, in the graph in Figure 7, when the disturbances from reflected waves R11 and R12 are processed in addition to the disturbances from reflected waves R11 and R14, the average reflection intensity is -16 dB. Therefore, when the disturbances from reflected waves R11 and R12 and the disturbances from reflected waves R11 and R14 are processed together, there is a gain of 6 dB.

[0097] Naturally, the description of the present invention is not limited to the embodiments and fields described above. Therefore, in another non-limiting embodiment, the radar sensor 10 comprises two or more transmitting antennas 100 and three or more receiving antennas 101. Thus, in one non-limiting embodiment, the thickness e2 may be dimensioned before or in parallel with the thickness e1.

[0098] Therefore, the described invention has the following advantages in particular. - This makes it possible to minimize the primary reflected waves R11, R12, and R14 reflected back towards the radar sensor 10. Thus, the signal-to-noise ratio of the radar sensor 10 is no longer low. The transmission of radar wave R1 is improved. - This makes it possible to minimize reflected waves R11, R12, and R14 by changing the total thickness e1 and total thickness e2, and therefore by changing the diffuse reflective white layer 110 and the transparent layer 112. - This makes it possible to minimize the waves R11 and R12 reflected between two non-equivalent layers having significantly different refractive indices.

Claims

1. A vehicle assembly (1) for a vehicle (2), wherein the vehicle assembly (1) is - A radar sensor (10) configured to transmit radar waves (R1) in the range (Δ1) of wavelength (λ), - A layer array (11) positioned facing the radar sensor (10) and configured to perform an illumination function, wherein the layer array (11) comprises: a first subassembly (S1) of at least one layer (110) that is reflective in the visible region, each layer (110) having a primary refractive index (n10) and a primary thickness (e10); and a second subassembly (S2) of at least one layer (112) that is transparent in the visible region, each layer (112) having a secondary refractive index (n20), wherein the primary refractive index (n10) is higher than the secondary refractive index (n20) in the radar region; - A vehicle assembly (1) characterized in that the total thickness (e1) of the first subassembly (S1) of the layer (110) is sized such that there is a phase shift of π modulo 2π between the waves (R11) reflected by the outer surface (S1.1) of the radar wave (R1) incident on the outer surface (S1.1) of the first subassembly (S1) and the waves (R12) reflected by the interface (J12) between the first subassembly (S1) and the second subassembly (S2) as they exit the first subassembly (S1).

2. The vehicle assembly (1) according to claim 1, wherein the total thickness (e2) of the second subassembly (S2) of the layer (112) is sized such that there is a phase shift of π modulo 2π between the wave (R11) reflected by the outer surface (S1.1) of the first subassembly (S1) and the wave (R14) reflected by the outer surface (S2.1) of the second subassembly (S2) as they exit the first subassembly (S1).

3. The vehicle assembly (1) according to claim 2, wherein the total thickness (e2) of the second subassembly (S2) of the layer (112) is dimensionalized by changing the thickness of only one of the layers (112) of the second subassembly (S2).

4. The vehicle assembly (1) according to any one of claims 1 to 3, wherein each layer (110) of the first subassembly (S1) has a refractive index (n10) that differs from the refractive index (n10) of another adjacent layer (110) of the first subassembly (S1) by less than 0.1 in the radar region.

5. The vehicle assembly (1) according to any one of claims 1 to 3, wherein each layer (112) of the second subassembly (S2) has a refractive index (n20) that differs from the refractive index (n20) of another adjacent layer (112) of the second subassembly (S2) by less than 0.1 in the radar region.

6. The vehicle assembly (1) according to any one of claims 1 to 3, wherein each layer (112) of the second subassembly (S2) has a refractive index (n20) that differs from the refractive index (n10) of the layer (110) of the first subassembly (S1) by more than 0.1 in the radar region.

7. The vehicle assembly (1) according to any one of claims 1 to 3, wherein the vehicle assembly (1) comprises at least one light source (12) configured to emit visible light (Lx) that enters the layer array (11) through one edge of the layer (112) of the second subassembly (S2) of the layer array (11).

8. The vehicle assembly (1) according to any one of claims 1 to 3, wherein the at least one layer (110) that is reflective in the visible region is composed of titanium (TiO2) particles.

9. The vehicle assembly (1) according to any one of claims 1 to 3, wherein the layer arrangement (11) forms an illuminated logo or an illuminated front-end grille, or forms part of a headlamp.

10. A layer array (11) positioned facing a radar sensor (10), wherein the radar sensor (10) is configured to transmit radar waves (R1) in a wavelength range (Δ1) of wavelength (λ), and the layer array (11) is configured to perform an illumination function, comprising: a first subassembly (S1) of at least one layer (110) which is reflective in the visible region, each layer (110) having a primary refractive index (n10) and a primary thickness (e10); and a second subassembly (S2) of at least one layer (112) which is transparent in the visible region, each layer (112) having a secondary refractive index (n20), wherein the primary refractive index (n10) is higher than the secondary refractive index (n20). - A layer arrangement (11) characterized in that the total thickness (e1) of the first subassembly (S1) of the layer (110) is sized such that there is a phase shift of π modulo 2π between the wave (R11) reflected by the outer surface (S1.1) of the radar wave (R1) incident on the outer surface (S1.1) of the first subassembly (S1) and the wave (R12) reflected by the interface between the first subassembly (S1) and the second subassembly (S2) as they exit the first subassembly (S1).

Images