Vehicle component comprising a radar sensor and a gradient index lens

Abstract

The invention relates to a vehicle component (1) for a vehicle (2), the vehicle component (1) comprising: - a radar sensor (10) having a field of view (FOV) and configured to transmit radar waves (R1) in a range (Δ1) of wavelengths (λ) into the field of view (FOV); and - a lens (11) arranged opposite the radar sensor (10); - characterized in that the lens (11) is a gradient-index lens and comprises a base layer (12) and a layer (13) forming a pattern (130) of sub-wavelength structured dielectric elements, wherein a repetition period of the pattern (130) is smaller than a quarter of a wavelength (λ) of the range (Δ1), and in that the layer (13) of the pattern (130) has a local refractive index (n1) calculated as a function of a local density (τ r ) of the pattern (130) in the layer (13).

Description

Technical Field

[0001] This invention relates to vehicle components. It is particularly applicable to motor vehicles, but not in a limiting way. Background Technology

[0002] Vehicle components known to those skilled in the art include:

[0003] - A radar sensor having a field of view and configured to transmit radar waves within a wavelength range into the field of view; and

[0004] - A lens, which is positioned facing the radar sensor.

[0005] This vehicle component is placed at the front or rear of the vehicle to meet the need for detecting objects in the vehicle's external environment using radar sensors. The lens is curved to fit the radar sensor's field of view. Specifically, the radar sensor's field of view can be magnified or reduced. For example, it can reduce the radar sensor's field of view to increase its range, or magnify the radar sensor's field of view to achieve wider detection of objects on the sides of the vehicle. Therefore, the lens can adjust the radar sensor's field of view according to the manufacturer's requirements.

[0006] One drawback of existing technology is that such curved lenses are space-consuming, bulky, and expensive. Furthermore, the lens material absorbs some of the radar waves transmitted by the radar sensor, which reduces the sensor's detection performance. This, in turn, reduces the radar sensor's detection range. Consequently, detection errors may occur, or objects may be present in the environment outside the vehicle but not detected. Summary of the Invention

[0007] In this context, the present invention aims to provide a vehicle component that allows for the resolution of the aforementioned defects.

[0008] Therefore, the present invention provides a vehicle component for a vehicle, the vehicle component comprising:

[0009] - A radar sensor having a field of view and configured to transmit radar waves within a wavelength range into the field of view; and

[0010] - A lens, which is positioned facing the radar sensor;

[0011] The lens is characterized in that it is a gradient index lens and includes a bottom layer and a layer forming a pattern of a subwavelength structured dielectric element, the repetition period of the pattern being less than one-quarter of the wavelength of the range, and the patterned layer is characterized in that the local refractive index is calculated based on the local density of the pattern in the layer according to the local refractive index.

[0012] According to a non-limiting embodiment, the vehicle component may also include one or more additional patterns selected from the following, either alone or in any technically possible combination.

[0013] According to a non-limiting embodiment, the radar sensor is a radar sensor that employs millimeter waves, ultra-high frequency waves, or microwaves.

[0014] According to a non-limiting embodiment, the radar waves are transmitted in a frequency band contained between 100 MHz and 5 GHz.

[0015] According to a non-limiting embodiment, the repetition period of the pattern is less than one-tenth of the wavelength.

[0016] According to a non-limiting embodiment, the lens is composed of unit cells, each unit cell comprising a pattern, and the local density of the pattern in the layer at a given point of the lens is equal to a weighted average of an obtained fill factor, the weighted average of which is for each unit cell on the lens at a given value located at a distance from the point in question less than an order of magnitude of one wavelength in the wavelength range used.

[0017] According to a non-limiting embodiment, the fill factor of each unit cell is equal to the volume of material in the unit cell divided by the product of the repetition period of the pattern and the maximum height in the pattern of the unit cell.

[0018] According to a non-limiting embodiment, the local density is equal to the product of the width and length of the pattern divided by the repetition period of the pattern. This is effective for cubic or rectangular patterns.

[0019] According to a non-limiting embodiment, the local refractive index consists of two effective refractive indices, which depend on the local density, the dielectric constant of the pattern, and the dielectric constant of air.

[0020] According to a non-limiting embodiment, the pattern is a segment of a cylindrical prism, a rectangular prism, a conical prism, a cubic prism, or a toroidal surface.

[0021] According to a non-limiting embodiment, the pattern has a size of less than 0.4 mm.

[0022] According to a non-limiting embodiment, the lens has a total thickness formed by the height of the pattern and the thickness of the bottom layer, the dimension of which is set such that it is equal to the product of m and the wavelength divided by twice the product of the equivalent refractive index of the pattern layer and the bottom layer and the cosine of the refraction angle corresponding to the incident angle of the radar wave, where m is an integer.

[0023] According to a non-limiting embodiment, if the incident angle is zero, then the total thickness is equal to the wavelength divided by twice the equivalent refractive index.

[0024] According to a non-limiting embodiment, the total thickness is defined by using an incident angle equal to arctan(d1 / (2e4)), where e4 is the distance between the radar sensor and the lens, and d1 is the distance between the transmitting antenna and the receiving antenna of the radar sensor.

[0025] A lens is also provided, configured to adapt to the field of view of a radar sensor of a vehicle, the radar sensor being configured to transmit radar waves, the lens being positioned facing the radar sensor, characterized in that:

[0026] - The lens is a gradient index lens and includes a base layer and a layer forming a pattern of a subwavelength structured dielectric element, the repetition period of which is less than one-quarter of the wavelength range of the radar wave transmitted, and the patterned layer having a local refractive index calculated based on the local density of the pattern in the layer. Attached Figure Description

[0027] A better understanding of the invention and its various applications will be gained by reading the following description and studying the accompanying drawings:

[0028] [ Figure 1 [Illustration] is a schematic diagram of a vehicle component according to a non-limiting embodiment of the present invention, the vehicle component including a radar sensor and a lens;

[0029] [ Figure 2 [This is based on a non-limiting embodiment.] Figure 1 The radar sensors of the vehicle components transmit and are Figure 1 A schematic diagram of radar waves partially reflected by the lens of a vehicle component.

[0030] [ Figure 3 [This is based on a non-limiting embodiment] Figure 1 A schematic diagram of a lens for a vehicle component, the lens comprising a base layer and a patterned layer;

[0031] [ Figure 4 This is a non-limiting embodiment of the present invention. Figure 3 A perspective view of a local area of ​​the pattern of the lens layer.

[0032] Unless otherwise stated, elements that are structurally or functionally consistent and appear in more than one figure are indicated by the same reference numerals in all the figures in which they appear. Detailed Implementation

[0033] refer to Figures 1 to 4 The present invention describes a vehicle component 1 for a vehicle 2. This vehicle component 1 is also referred to as vehicle system 1. In one non-limiting embodiment, the vehicle 2 is a motor vehicle. A motor vehicle refers to any type of motor vehicle. Throughout the remainder of this specification, this embodiment is considered a non-limiting example. Therefore, in the remainder of this specification, the vehicle 2 is also referred to as motor vehicle 2. In one non-limiting embodiment, the vehicle component 1 is placed behind a sign integrated into the grille of the motor vehicle 2 or integrated into a body portion located at the rear of the motor vehicle 2. In another non-limiting embodiment, the vehicle component 1 is placed within a lighting device or a signal transmitting device.

[0034] like Figure 1 The vehicle component 1, also known as vehicle device 1, as illustrated, includes:

[0035] - Radar sensor 10 having a field of view (FOV) and configured to transmit radar wave R1 (also referred to as primary radar wave R1) into the field of view FOV; and - lens 11 positioned facing the radar sensor 10.

[0036] These components are described below.

[0037] The radar sensor 10 is described below. For example... Figure 1As illustrated, the radar sensor 10 is positioned facing the lens 11. In a non-limiting embodiment, the radar sensor 10 is a millimeter-wave (waves between 24 GHz and 300 GHz) or ultra-high frequency (waves between 300 MHz and 81 GHz) or microwave (waves between 1 GHz and 300 GHz) radar sensor. In a non-limiting variation of the embodiment, the radar sensor 10 operates at a radar frequency between 76 GHz and 81 GHz. The radar wave R1 is transmitted within a wavelength range Δ1 of λ. In a non-limiting embodiment, the radar wave R1 is transmitted in a frequency band between 100 MHz and 5 GHz. Therefore, in a non-limiting example, if the sensor operates at a radar frequency of 77 GHz, i.e., a wavelength λ of 3.95 mm and a frequency band of 1 GHz, then the radar sensor 10 will operate in a frequency band from 76.5 GHz to 77.5 GHz. Therefore, the radar wave R1 will be transmitted in a frequency range of 76.5 GHz to 77.5 GHz, i.e., a wavelength range Δ1 of λ from 3.87 mm to 3.92 mm. Therefore, in another non-limiting example, if radar sensor 10 operates at a radar frequency of 78.5 GHz and a frequency band of 5 GHz, then radar sensor 10 will operate in a frequency band from 76 GHz to 81 GHz. Therefore, radar wave R1 will be transmitted in the frequency range of 76 GHz to 81 GHz, i.e., the wavelength λ ranges from 3.701 mm to 3.945 mm.

[0038] like Figure 2 As illustrated, the transmitted radar wave R1 strikes lens 11 at an incident angle θ. In one non-limiting embodiment, the incident angle θ is contained between 0° and + / -30°. Therefore, the field of view (FOV) varies between -30° and +30°. The center of the FOV forms a 0° angle relative to the longitudinal axis of the vehicle (also referred to as the vehicle axis). In another non-limiting embodiment, the FOV varies between -90° and +45°. The center of the FOV forms a -45° angle relative to the vehicle axis, and the incident angle θ of the radar wave R1 on lens 11 remains close to 0° (thus, vehicle assembly 1 is positioned at approximately 45° to the vehicle axis).

[0039] Radar sensor 10 is configured to scan the external environment of the motor vehicle 2 by means of the transmission of radar waves R1. Figure 1 As illustrated, the radar sensor 10 therefore includes:

[0040] - At least one transmitting antenna 100, which is configured to transmit radar wave R1, also referred to as primary radar wave R1;

[0041] - At least two receiving antennas 101 are configured to receive radar waves R2, also referred to as secondary radar waves R2 or return radar waves R2.

[0042] The radar sensor 10 also includes at least one transmitter 103 and at least one receiver 104, the at least one transmitter 103 being configured to generate a primary radar wave R1, and the at least one receiver 104 being configured to process and return a received secondary radar wave R2. In a non-limiting embodiment, a single electronic component may be used for both transmission and reception functions. Thus, one or more transceivers will be present. The transmitter 103 generates the primary radar wave R1, which is subsequently transmitted by the transmitting antenna 100 and reflected from the object 3 (here, a pedestrian in the non-limiting example illustrated) in the environment outside the motor vehicle 2. The reflected radar waves are the waves that are transmitted back to the radar sensor 10. These are the secondary radar waves R2 received by the receiving antenna 101. These are radar waves that are transmitted again in the direction of the radar sensor 10. In a non-limiting embodiment, the primary radar wave R1 and the secondary radar wave R2 are radio frequency waves. In a non-limiting embodiment, the radar sensor 10 includes multiple transmitters 103 and multiple receivers 104.

[0043] A transmitting antenna 100 (also referred to as antenna 100) is configured to transmit a primary radar wave R1 generated by a transmitter 103. A receiving antenna 101 (also referred to as antenna 101) is configured to receive a secondary radar wave R2 and transmit it to a receiver 104, which then processes the secondary radar wave R2. A phase shift exists between the secondary radar waves R2 received by the receiving antenna 101, which allows the determination of the angular position of an object 3 relative to a motor vehicle 2, located in an environment outside the motor vehicle 2. In a non-limiting embodiment, antennas 100 and 101 are patch antennas or slot antennas.

[0044] In one non-limiting embodiment, antennas 100, 101, transmitter 103, and receiver 104 are placed on a printed circuit board 105. In one non-limiting embodiment, the printed circuit board is a rigid printed circuit board (also referred to as a printed circuit board assembly or PCBA) or a flexible printed circuit board (also referred to as a flexible board).

[0045] The radar sensor 10 also includes an electronic control unit 106 configured to control the transmitter 103 and the receiver 104. Since such radar sensors are known to those skilled in the art, they will not be described in detail here.

[0046] Lens 11 is described below. Lens 11 is a gradient index lens. In other words, lens 11 is planar and has an equivalent refractive index n on the wavelength λ scale within the wavelength range Δ1. eq Since the refractive index n1 (of layer 13) is variable, while the refractive index n2 (of bottom layer 12) is constant, the lens 11 is variable on the scale of the wavelength λ.

[0047] The equivalent refractive index n is changed accordingly by means of the density and size of pattern 130 (described below). eq The lens 11 allows it to be adapted to the field of view (FV) of the vehicle assembly 1. This results in a vehicle assembly 1 having a different field of view (FV) than that of the radar sensor 10. Therefore, it is particularly possible to use the long-range radar sensor 10 (with a reduced field of view) to obtain a wide field of view (FV), or to use the short-range radar sensor 10 (with an enlarged field of view (FV)) to obtain a reduced field of view (FV), depending on the manufacturer's requirements. The lens 11 is positioned between the radar sensor 10 and the exterior of the vehicle 2.

[0048] like Figure 2 and Figure 3 As illustrated, lens 11 includes a base layer 12 and a layer 13 of pattern 130. The base layer 12 is configured to hold the layer 13 of pattern 130. The base layer 12 has a refractive index n2. In a non-limiting embodiment, the base layer 12 is made of plastic, glass, or ceramic. In one non-limiting example, the plastic is polycarbonate. The layer 13 of pattern 130 forms a subwavelength structured dielectric element. The layer 13 of pattern 130 has a refractive index n1 that depends on the pattern 130 and the spacing of the pattern 130, also referred to as the local refractive index n1. In a non-limiting embodiment, the dielectric element is made of plastic, glass, or ceramic. In one non-limiting example, the plastic is polycarbonate. It will be recalled that dielectrics are non-conductive and therefore, unlike conductors, allow radar waves R1 to pass through.

[0049] “Structured” means that layer 13 includes patterns 130, which are also referred to as structures. “Subwavelength” means that the structured dielectric is smaller than the wavelength λ of the range Δ1 on a scale smaller than the wavelength λ. The fact that the pattern 130 of layer 13 is subwavelength allows layer 13 to be modeled as a variable exponent layer. In the opposite case, layer 13 would have to be considered as a diffractive optical element.

[0050] like Figure 4 As shown in the diagram, Figure 4This is a view of a partial region Z1 of pattern 130 in layer 13, pattern 130 having dimensions a1 (width), a2 (width), and h1 (height). In a non-limiting embodiment, pattern 130 is a cylindrical prism (also referred to as a cylindrical prism), or a rectangular prism (also referred to as a rectangular prism), or a pyramidal prism (also referred to as a pyramidal prism), or a cubic prism (also referred to as a square prism)—in Figure 4 The middle figure illustrates the latter case—or even a ring-shaped segment. Pattern 130 can also have any other parallelepiped shape. In a non-limiting embodiment, pattern 130 has dimensions a1, a2 of less than 0.4 mm. This value is very small compared to the wavelength λ of the range Δ1. For example, for a frequency of 77 GHz, the wavelength λ of the range Δ1 is 4 mm; in this case, the values ​​of a1, a2 are approximately equal to λ / 10.

[0051] like Figure 4 As illustrated, lens 11 is composed of unit cells 132, each unit cell including a pattern 130 and an inflatable segment surrounding the pattern 130. In a non-limiting embodiment variation (not shown), the pattern 130 is continuous (adjacent) on the boundary surface between layer 13 and bottom layer 12. This non-limiting variation is applicable to patterns 130 with segments of conical or annular shape. Unit cells 132 are defined by the repetition period Λ of structure 130, which is also referred to as the repetition period Λ of pattern 130 or even the grating period Λ, where Λ = Λ1 x Λ2. Λ1 is the grating in the first direction Ax (e.g., ...). Figure 4 The period of the grating (as shown in the diagram), and Λ2 is the period of the grating in the second direction Ay (as shown in the diagram). Figure 4 The period (as illustrated). Ax and Ay are arbitrary directions that are not parallel to each other. In one non-limiting embodiment, the second direction Ay is perpendicular to the first direction Ax. In another non-limiting example, the unit cell 132 is a square, hexagon, parallelogram, or any other shape that allows the boundary surface between layer 13 and bottom layer 12 to be periodically tiled. A third direction perpendicular to the first direction Ax and the second direction Ay will be denoted as Az, and these directions together form the reference frame Ax, Ay, Az.

[0052] In a first non-limiting embodiment, the subwavelength structured dielectric element forming layer 13 is a periodic subwavelength structured dielectric element. The dimensions a1, a2 of pattern 130 vary along layer 13 to change the refractive index of lens 1, while Λ1 and Λ2 remain constant. In other words, pattern 130 in the first direction Ax (e.g., ...) Figure 4 As shown in the figure, they are spaced evenly apart on the second direction Ay (as shown in the figure) which is perpendicular to the first direction Ax. Figure 4As illustrated, the spacing is consistent. In other words, layer 13 has a consistent spacing 131x between patterns 130 in the first direction Ax and a consistent spacing 131y in the second direction Ay (as shown in the figure). Figure 4 (As illustrated), or in other words, there is an equal proportion of air in pattern 130.

[0053] In another non-limiting embodiment (e.g.) Figure 3 As illustrated, the subwavelength structured dielectric elements forming layer 13 are not periodic. Λ1 and Λ2 vary along layer 13 to change the refractive index of lens 1, while the dimensions a1 and a2 of pattern 130 remain constant. Layer 13 includes variable spacings 131x and 131y between patterns 130, or in other words, different proportions of air exist between patterns 130. Λ1 and Λ2, as well as the dimensions a1 and a2 of pattern 130, can also be varied to change the refractive index of lens 1.

[0054] "Subwavelength" refers to a grating period Λ1, Λ2 that is less than one-quarter of a wavelength λ within the range Δ1 of the wavelength λ. In a non-limiting example, the wavelength λ under discussion is the shortest wavelength within the range Δ1. Therefore, Λ1 < λ / 4 and Λ2 < λ / 4. In a non-limiting embodiment, the grating periods Λ1, Λ2 are less than one-tenth of the wavelength λ. Therefore, Λ1 < λ / 10 and Λ2 < λ / 10. It will be noted that this wavelength λ is selected from the range Δ1 and will be the wavelength used in the equations below.

[0055] like Figure 2 As illustrated, when radar wave R1 is transmitted by radar sensor 10, it travels to lens 11, which has a thickness e0. Radar wave R1 strikes lens 11 at an incident angle θ corresponding to the refraction angle r. Radar wave R1 is reflected from lens 11, generating two reflected waves, one of which, R11, is reflected from the outer surface of the bottom layer 12 of lens 11, and the other is reflected from inside lens 11. The two reflected waves R11 and R12 are referred to as first-order (1st order) reflected waves that return to radar sensor 10. These are parasitic reflections. When the incident angle θ is not 0°, the corresponding refraction angle r is also not 0°. The phase difference between the two reflected waves R11 and R12... (also known as phase shift) )equal:

[0056] [Mathematical Expression 1]

[0057]

[0058] in:

[0059] -n eq-δ is the equivalent refractive index of the bottom layer 12 and the bottom layer 13; -δ is the path of the reflected wave R12 through the material, which is equal to 2e0 / cos(r);

[0060] -nδ / λ is the phase shift caused by the travel through the material;

[0061] -π is the phase shift caused by internal reflections in layer 13 of the bottom layer 12 and pattern 130;

[0062] -((2e0tan(r)sin(θ)) / λ) is the phase shift in air caused by the separation between the reflection point Pt1 of the reflected wave R11 and the exit point Pt2 of the reflected wave R12.

[0063] When sin(θ) = n eq When we multiply by sin(r), we get the following:

[0064] [Mathematical Expression 2]

[0065]

[0066] Right now:

[0067] [Mathematical Expression 3]

[0068]

[0069] Regardless of the value of the refraction angle r.

[0070] Assuming the reflected waves R11 and R12 return along the direction of radar sensor 10, they will cause interference to radar sensor 10, or in other words, lead to a decrease in the signal-to-noise ratio. To eliminate this interference, the total thickness e0 of lens 11 will be limited such that the reflected waves R11 and R12 are out of phase, thereby creating destructive interference. To achieve destructive interference, the phase difference between the two reflected waves R11 and R12... It must be equal to π modulo 2π. Therefore, it is necessary to... Where m is a natural number. Therefore, we obtain the following:

[0071] [Mathematical Expression 4]

[0072]

[0073] Right now:

[0074] e0=mλ / (2n eq cos(r)).

[0075] It should be noted that regardless of the value of angle r, the equation e0 = mλ / (2n) should be applied. eqcos(r)). Therefore, the total thickness e0 is set such that it is equal to m multiplied by the wavelength λ, divided by the equivalent refractive index neq of layer 13 and bottom layer 12 of pattern 130 multiplied by twice the cosine of the refraction angle r corresponding to the incident angle θ of radar wave R1, where m is an integer. Therefore, based on the equivalent refractive index neq... eq The total thickness e0 can be determined by using the wavelength λ used within the operating frequency range of radar sensor 10, such that the reflected waves R11 and R12 cancel each other out. In a non-limiting embodiment, the wavelength used is the wavelength located in the middle of the permissible range Δ1.

[0076] When the angle of incidence is 0, the ideal total thickness e0 is defined; and m equals 1. When θ = 0, then r = 0. Therefore, for m = 1, the ideal total thickness e0 of lens 11 is e0 = λ(2n eq When r = 0°, then cos(r) = 1.

[0077] In a non-limiting embodiment, lens 11 has a total thickness e0 that is contained between 0.8 and 1.2 times the ideal total thickness e0. This range of values ​​takes into account the possible emission angles of radar sensor 10. The possible values ​​of the incident angle θ are defined in the technical specifications of radar sensor 10, meaning that the possible values ​​of the incident angle θ are within the field of view (FOV) of radar sensor 10. In a non-limiting example, the incident angle θ is contained between 0° and + / - 30°. The value range of 0.8 to 1.2 allows for consideration of manufacturing tolerances for the total thickness e0.

[0078] It should be noted that there exists an incident angle θ at which the reflected radar waves R11 and R12 cause maximum interference to the receiving antenna 101 of the radar sensor 10. This incident angle θ is called the critical incident angle 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 antenna 101; and e4 is the distance between the radar sensor 10 and the lens 11, as shown below. Figure 2 As illustrated. It will be noted that, in the non-limiting example, the midpoint of the receiving antenna 101 is considered when calculating d1.

[0079] Therefore, depending on the value of the local refractive index n1 and the wavelength λ used within the operating frequency range of the radar sensor 10 (between 76 GHz and 81 GHz in a given non-limiting example), the total thickness e0 that must be present to allow the reflected waves R11 and R12, on the order of 1, to cancel each other out can be determined. The reflected radar waves R11 and R12 are reflected from the lens 11 in a finite area. Therefore, the receiving antenna 101 sees less noise, resulting in a better signal-to-noise ratio.

[0080] Lens 11 has a total thickness e0 formed by the height h1 of pattern 130 and the thickness e2 of bottom layer 12. To determine the size of the total thickness e0, the height h1 or thickness e2 of pattern 130 is adjusted such that for a given r, e0 = mλ / (2n) eq cos(r)). In a non-limiting embodiment, the given r corresponds to the critical incident angle θ.

[0081] Equivalent refractive index n eq equal:

[0082] [Mathematical Expression 5]

[0083]

[0084] Where n1 is the local refractive index of layer 13 of pattern 130; n2 is the refractive index of the bottom layer 12; e1 is the height h1 of pattern 130; and e2 is the thickness of the bottom layer 12. It will be noted that n1 depends on the location of the local region Z1 of pattern 130 on layer 13 where the calculation is performed. Therefore, the equivalent refractive index n eq It depends on the location of the local region Z1 on layer 13.

[0085] It will be noted that layer 13 of pattern 130 has a local density τ according to the pattern 130 described in layer 13. r The calculated local refractive index n1. The local density τ at a point on lens 11. r The fill factor τ of each cell 132 located at a distance from the point in question less than an order of magnitude of one wavelength from the wavelength λ of the wavelength range Δ1 used is the fill factor τ. r132 The weighted average. Local refractive index n1 (also known as effective refractive index n) eff (Constituted by two effective refractive indices n) effTE and n effTM Composition, these two effective refractive indices n effTE and n effTM Depends on the polarization of the incident wave (i.e., the primary radar wave R1) and can be expressed as the local density τ r (also known as the fill factor τ) r The density τ is a function of τ, representing the percentage of material occupied by the high refractive index n1 medium (i.e., pattern 130 here) relative to the low refractive index n0 medium (i.e., air here). It will be noted that the local density τ... r This represents the percentage of material occupied by a medium with a high refractive index n1 in a region of size having a wavelength λ that is on the order of one wavelength from the wavelength range Δ1 used. Therefore:

[0086] [Mathematical Expression 6]

[0087]

[0088] [Mathematical Expression 7]

[0089]

[0090] The term TE indicates the polarization of the incident wave (i.e., the radar wave R1 striking the lens 11) perpendicular to the plane of the substrate (i.e., the bottom layer 12); TM indicates the polarization of the wave parallel to the plane of the substrate; ε max The dielectric constant represents the medium with the highest refractive index (i.e., pattern 130); and ε min This represents the dielectric constant of the medium with the lowest refractive index (i.e., air in this case). In another non-limiting embodiment, air can be replaced by a plastic with a very low refractive index.

[0091] It will be noted that when the incident wave (here, the radar wave R1) is irradiating the structured dielectric element (i.e., lens 11) and has a wavelength λ (λ>>Λ1, and λ>>Λ2) that is much larger than the repetition periods Λ1 and Λ2 of structure 130, this is a problem of the propagation mechanism known as the static limit.

[0092] For example Figure 4 The illustrated two-dimensional structure 130, the effective refractive index n of the 2D structure eff2D It can be approximated as being on the order of zero by the quadratic average of the effective refractive indices of the two polarizations TM and TE in one dimension, which corresponds to the static limit. In this particular case, the fill factor τ of the unit cell 132 is... r132 for:

[0093] [Mathematical Expression 8]

[0094]

[0095] and:

[0096] [Mathematical Expression 8]

[0097]

[0098] In a more general case, for any shape of pattern 130, where Λ1 and Λ2 are arbitrary, and having a rectangular base of unit cells 132, the fill factor τ of unit cells 132 is... r132 Will be:

[0099] [Mathematical Expression 9]

[0100]

[0101] This corresponds to the material volume (V) in unit cell 132. 132The ratio of the volume of the empty boundary (Λ1Λ2hmax) to the maximum height of the pattern 130 in the unit cell 132 (i.e., the highest height in the pattern 130), and

[0102] [Mathematical Expression 10]

[0103]

[0104] Where (X132, Y132, 0) are the coordinates of the corner C1 of unit cell 132, and M(X, Y, Z) = 1 if the coordinate point (X, Y, Z) is in the material; and M(X, Y, Z) = 0 if the coordinate point (X, Y, Z) is in the air. It will be noted that when in the material, the point is located within the pattern 130 of unit cell 132, and when in the air, the point may potentially be located inside the pattern 130 (because in a non-limiting example, the pattern 130 may actually contain pores). It will be noted that in Figure 4 In the unrestricted example, hmax = h1, as described above.

[0105] It will be noted that the material volume V 132 This equation is valid for any unit cell 132 on a rectangular base, regardless of the shape of the pattern 130 within that unit cell 132. Therefore, because Λ1 and Λ2 can vary from one unit cell 132 to another, and because the maximum height hmax can vary from one pattern 130 to another, each unit cell 132 can contain different material volumes and thus have different fill factors τ. r132 To obtain the fill factor τ of the entire layer 13 of the pattern 130 at a given point on lens 11. r Calculate the fill factor τ of each cell 132 on lens 11 at a given value that is less than an order of magnitude of one wavelength in the wavelength λ of the wavelength range Δ1 used. r132 The weighted average. This limitation applies to all points of lens 11. In a non-limiting embodiment, these points belong to the surface of the bottom layer 12 at coordinate Z=0. Therefore:

[0106] [Mathematical Expression 11]

[0107]

[0108] Where n represents any one of the unit cells 132 on the lens 11 at a given value that is less than the order of one wavelength in the wavelength λ of the wavelength range Δ1 used.

[0109] It will be noted that a low-cost injection molding manufacturing technique was used to produce lens 11. Specifically, the base layer 12 and the layer 13 of pattern 130 are made of the same material and are injection molded simultaneously, which significantly reduces manufacturing costs. Additive manufacturing technology (also known as 3D printing) can also be used in the manufacturing process.

[0110] Of course, 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 includes more than one transmitting antenna 100 and more than two receiving antennas 101.

[0111] Therefore, the described invention has the following particular advantages:

[0112] -The range of radar sensor 10 can be maintained without reducing its size;

[0113] - The volume of vehicle component 1 can be reduced by replacing the curved lens with a flat lens;

[0114] - The cost and weight of vehicle component 1 can be reduced by replacing curved lenses with flat lenses;

[0115] - By replacing the curved lens with a flat lens, the absorption of some radar waves R1 transmitted by the radar sensor 10 can be significantly reduced;

[0116] - This allows the field of view of the radar sensor 10 to be adapted to the manufacturer's needs, much like a curved lens;

[0117] - It can suppress reflected waves R11 and R12 of the order of 1 reflected in the direction of radar sensor 10. Therefore, the signal-to-noise ratio of radar sensor 10 is no longer low.

Claims

1. A vehicle component (1) for a vehicle (2), the vehicle component (1) comprising: - A radar sensor (10) having a field of view and configured to transmit radar waves R1 within a wavelength range Δ1 of wavelength λ into the field of view; and - Lens (11), the lens (11) is positioned facing the radar sensor (10); - Characterized by the lens (11) being a gradient exponential lens and comprising a bottom layer (12) and a layer (13) forming a pattern (130) of a subwavelength structured dielectric element, wherein the repetition periods Λ1, Λ2 of the pattern (130) are less than one-quarter of a wavelength λ of the range Δ1, and characterized by the layer (13) of the pattern (130) having a local refractive index n1, based on the local density τ of the pattern (130) in the layer (13). r To calculate the local refractive index n1, The lens (11) has a total thickness e0 formed by the height h1 of the pattern (130) and the thickness e2 of the bottom layer (12), the total thickness e0 being set such that it is equal to the product of m and the wavelength λ divided by the equivalent refractive index n of the layer (13) of the pattern (130) and the bottom layer (12). eq Twice the product of the cosine of the refraction angle r corresponding to the incident angle θ of the radar wave R1, where m is an integer. The total thickness e0 is defined by using the incident angle θ equal to arctan(d1 / (2e4)), where e4 is the distance between the radar sensor (10) and the lens (11), and d1 is the distance between the transmitting antenna (100) and the receiving antenna (101) of the radar sensor (10).

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

3. The vehicle component (1) according to claim 2, wherein, The radar wave R1 is transmitted in a frequency band between 100 MHz and 5 GHz.

4. The vehicle component (1) according to any one of claims 1-2, wherein, The repetition periods Λ1 and Λ2 of the pattern (130) are less than one-tenth of the wavelength λ.

5. The vehicle component (1) according to any one of claims 1-2, wherein, The lens (11) is composed of unit cells (132), each unit cell including a pattern (130), and the local density τ of the pattern (130) in the layer (13) at a given point of the lens (11) is... r Equal to all the fill factors τ obtained r132 The weighted average of all fill factors τ r132 The weighted average is obtained for each unit cell (132) on the lens (11) at a given value located at a distance from the point in question less than the order of one wavelength in the wavelength range Δ1 used.

6. The vehicle component (1) according to claim 5, wherein, The fill factor τ for each unit cell (132) r132 Equal to the material volume V in the unit cell (132) 132 The whole is divided by the product of the repeating periods Λ1 and Λ2 of the pattern (130) and the maximum height hmax in the pattern (130) of the unit cell (132).

7. The vehicle component (1) according to any one of claims 1-2, wherein, The local density τ r The product of the width a1 and length a2 of the pattern (130) is divided by the repeating periods Λ1 and Λ2 of the pattern (130).

8. The vehicle component (1) according to any one of claims 1-2, wherein, The local refractive index n1 depends on the local density τ. r and the dielectric constant ε of the pattern (130) max and the dielectric constant ε of air min The two effective refractive indices n effTE n effTM composition.

9. The vehicle component (1) according to any one of claims 1-2, wherein, The pattern (130) is a segment of a cylindrical prism, or a rectangular prism, or a conical prism, or a cubic prism, or a toroidal surface.

10. The vehicle component (1) according to any one of claims 1-2, wherein, The pattern (130) has dimensions a1 and a2 that are less than 0.4 mm.

11. The vehicle component (1) according to claim 1, wherein, If the incident angle θ is equal to zero, then the total thickness e0 is equal to the wavelength λ divided by the equivalent refractive index n. eq Twice as much.

12. A lens (11) configured to adapt to the field of view of a radar sensor (10) of a vehicle (2), the radar sensor (10) being configured to transmit radar waves R1, the lens (11) being positioned facing the radar sensor (10), characterized in that: - The lens (11) is a gradient index lens and includes a bottom layer (12) and a layer (13) forming a pattern (130) of a subwavelength structured dielectric element, wherein the repetition periods Λ1, Λ2 of the pattern (130) are less than one-quarter of a wavelength λ in the range Δ1 of the wavelength λ of the transmitted radar wave R1, and the layer (13) of the pattern (130) has a local refractive index n1, which is determined by the local density τ of the pattern (130) in the layer (13). r To calculate, The lens (11) has a total thickness e0 formed by the height h1 of the pattern (130) and the thickness e2 of the bottom layer (12), the total thickness e0 being set such that it is equal to the product of m and the wavelength λ divided by the equivalent refractive index n of the layer (13) of the pattern (130) and the bottom layer (12). eq Twice the product of the cosine of the refraction angle r corresponding to the incident angle θ of the radar wave R1, where m is an integer. The total thickness e0 is defined by using the incident angle θ equal to arctan(d1 / (2e4)), where e4 is the distance between the radar sensor (10) and the lens (11), and d1 is the distance between the transmitting antenna (100) and the receiving antenna (101) of the radar sensor (10).

Images