WO2025027204A1 - Lighting device for a motor vehicle configured to provide a high beam function and/or a low beam function - Google Patents

Abstract

The invention relates to a lighting device (2) for a motor vehicle (1), the lighting device being configured to provide a high beam function and/or a low beam function, the lighting device (2) being characterised in that it comprises: · a plurality of light sources (4a, 4b, 4c) configured to each produce a monochromatic light beam (F); · an optical device (14) arranged facing the plurality of light sources (4a, 4b, 4c) such that the light beams (F) pass through the optical device (14), the optical device (14) comprising a plurality of metalenses (15a, 15b, 15c) configured to respectively modify at least one property of the wavefront of each light beam (F) so as to orient it in a propagation direction.

Description

Luminous device for a motor vehicle configured to provide a high beam function and/or a low beam function.

The present invention relates to a lighting device for a motor vehicle, the lighting device being configured to provide a high beam function and/or a low beam function, i.e. to project at least one lighting zone in front of a motor vehicle for visibility functions while allowing an improvement in the aerodynamic performance of the motor vehicle. The invention also relates to a motor vehicle equipped with such a lighting device.

Driving in reduced visibility, whether due to weather conditions or low light, poses two major challenges for the driver: seeing where they are going and being seen by other road users.

Motor vehicles therefore include lighting devices generally placed on the front of a vehicle. These lighting devices include main beam headlights and dipped beam headlights. Main beam headlights are brighter and project a symmetrical beam to illuminate the road over a longer distance. Dipped beam headlights project an asymmetrical beam that illuminates the road over a shorter distance. Dipped beam headlights are intended for example for city driving; main beam headlights are intended for dark roads without urban lighting.

The lighting devices known from the prior art are generally heavy and bulky, both for the main beam and for the dipped beam. Furthermore, the lighting devices known from the prior art are generally mounted on a front face of the motor vehicle, which contributes to poor aerodynamic performance which leads to higher energy consumption and increased CO2 emissions. Finally, the lighting devices known from the prior art limit the style of the motor vehicle.

Presentation of the invention

The objective of the present invention is to provide a lighting device for vehicles which overcomes at least one of the above drawbacks, and improves the lighting devices known from the prior art.

In particular, the lighting device according to the invention aims to be light, compact and suitable for ensuring the functions of a main beam and/or a dipped beam while improving the aerodynamics of the motor vehicle to reduce its energy consumption and its CO2 emissions rate.

Thus, a first object of the invention is a lighting device which is simple to manufacture and capable of projecting lighting zones at the front of the motor vehicle with high luminous efficiency.

A second object of the invention is a more compact and lighter lighting device, easily integrated into a motor vehicle.

• une pluralité de sources lumineuses configurées pour produire chacune un faisceau lumineux monochromatique ;
• un dispositif optique juxtaposé à la pluralité de sources lumineuses de sorte que les faisceaux lumineux traversent le dispositif optique, ledit dispositif optique comportant une pluralité de méta-lentilles configurées pour modifier respectivement au moins une propriété du front d’onde de chaque faisceau lumineux de sorte à l’orienter dans une direction de propagation.

The invention relates to a lighting device for a motor vehicle, the lighting device being configured to provide a high beam function and/or a low beam function, the lighting device being characterized in that it comprises:

• a plurality of light sources each configured to produce a monochromatic light beam;
• an optical device juxtaposed with the plurality of light sources so that the light beams pass through the optical device, said optical device comprising a plurality of meta-lenses configured to respectively modify at least one property of the wavefront of each light beam so as to orient it in a direction of propagation.

Thus, thanks to the meta-lenses, the lighting device according to the invention is very compact, which allows said lighting device to be integrated in locations different from those conventionally used, such as in a non-limiting example on the side of the motor vehicle rather than at the front.

According to non-limiting embodiments, said light device may further comprise one or more additional characteristics taken alone or in all technically possible combinations, among the following.

According to a non-limiting embodiment, the light device comprises at least three light sources and at least three meta-lenses.

According to a non-limiting embodiment, the light device comprises a first light source configured to emit a monochromatic light of red color having a wavelength between 620 nm and 700 nm, a second light source configured to emit a monochromatic light of green color having a wavelength between 490 nm and 570 nm, and a third light source configured to emit a monochromatic light of blue color having a wavelength between 450 nm and 490 nm.

According to a non-limiting embodiment, each meta-lens is adapted to the wavelength of the light source with which it is associated.

According to a non-limiting embodiment, said lighting device comprises at least one set of light sources juxtaposed next to each other and at least one stack of meta-lenses arranged opposite said set such that the light beams from the plurality of light sources pass through said at least one stack and each light source being configured to emit light of a different color from the other light sources of said at least one set, and the meta-lenses being designed to be tuned to different wavelengths.

According to a non-limiting embodiment, said lighting device comprises two sets of light sources juxtaposed next to each other and two stacks of meta-lenses arranged respectively opposite the two sets of light sources.

According to a non-limiting embodiment, the lighting device comprises at least one set of light sources juxtaposed next to each other and a set of meta-lenses juxtaposed next to each other so that the light beam produced by each light source passes through the meta-lens with which said light source is associated.

According to a non-limiting embodiment, said light device comprises at least three sets of light sources juxtaposed next to each other and at least three sets of corresponding meta-lenses juxtaposed next to each other, each set of light sources being configured to emit monochromatic light of a different color from the other sets.

According to a non-limiting embodiment, said light device comprises at least three sets of light sources juxtaposed next to each other and at least three sets of corresponding meta-lenses juxtaposed next to each other, each light source of each set being configured to emit a monochromatic light of a different color from the other light sources of the same set.

According to a non-limiting embodiment, each meta-lens comprises a nanostructure comprising an arrangement of nanopillars on its surface.

According to a non-limiting embodiment, the nanopillars of the nanostructure specific to each meta-lens have the same height.

According to a non-limiting embodiment, the height of the nanopillars is specific to each meta-lens.

According to a non-limiting embodiment, the nanopillars of the same meta-lens have the same height and have different diameters from each other, and are repeated periodically.

According to a non-limiting embodiment, the nanopillars have a cylindrical shape and the diameter of the nanopillars is between 100 nm and 320 nm.

The invention also relates to a motor vehicle comprising at least one lighting device according to any one of the preceding characteristics.

According to a non-limiting embodiment, said at least one lighting device is arranged on a side face of the motor vehicle.

Presentation of figures

These objects, characteristics and advantages of the present invention will be explained in detail in the following description of different particular embodiments made without limitation in relation to the attached figures among which:

There is a schematic view of a motor vehicle equipped with a lighting device configured to provide the functions of a high beam and a low beam.

There is a schematic view of a light device according to a first non-limiting variant embodiment of a first non-limiting embodiment of the invention, the light device comprising three light sources and an optical device comprising a stack of three meta-lenses.

There is a schematic view of a light device according to a second non-limiting variant embodiment of a first non-limiting embodiment of the invention, the light device comprising two sets of three light sources and an optical device comprising two stacks of three meta-lenses.

There is a schematic view of a light device according to a first non-limiting variant embodiment of a second non-limiting embodiment of the invention, the light device comprising three sets of three light sources and an optical device comprising three sets of three meta-lenses side by side.

There is a schematic view of a light device according to a second non-limiting variant embodiment of a second non-limiting embodiment of the invention, the light device comprising at least one set of three light sources and an optical device comprising at least one set of three side-by-side meta-lenses.

There is a schematic view of a lighting device comprising three sets of three light sources of the and three sets of three meta-lenses of the .

There is a schematic perspective view of a detail of a nanostructure of a meta-lens of the optical device of one of figures 2a to 3c according to a non-limiting embodiment.

There is another schematic view of a detail of a nanostructure of a meta-lens of the .

There is a schematic view of a motor vehicle equipped with a lighting device of one of Figures 2a to 3c.

There illustrates a non-limiting embodiment of a lighting beam of a dipped beam headlight emitted by the lighting device of one of figures 2a to 3c.

There illustrates a non-limiting embodiment of a lighting beam of a high beam emitted by the lighting device of one of figures 2a to 3c.

There illustrates a greatly enlarged view of a non-limiting embodiment of a single nanopillar of a meta-lens of the optical device of one of Figures 2a to 3c with a portion of a substrate.

There illustrates an enlarged view of a non-limiting embodiment of a plurality of nanopillars of a meta-lens of the optical device of one of Figures 2a to 3c.

There illustrates a first curve indicating a phase variation as a function of the radius of a nano-pillar of a meta-lens of the optical device of one of figures 2a to 3c.

There illustrates a second curve indicating a variation of light transmission as a function of the radius of a nano-pillar of a meta-lens of the optical device of one of figures 2a to 3c.

There schematically illustrates the light beams emitted by light sources of the light device of one of figures 2a to 3c which pass through meta-lenses to arrive at the same location.

Detailed description

An embodiment of a motor vehicle 1 according to the invention is described below with reference to FIGS. 1 to 12. Throughout the description, the motor vehicle 1 is a motor vehicle of any type, in particular a passenger vehicle, a utility vehicle, a truck or even a bus. The motor vehicle 1 is equipped with a lighting device 2 configured to provide the functions of a high beam and a low beam.

Examples of the beam shape for dipped beam and main beam are schematically illustrated in the . On this , high beam and dipped beam are distinguished from each other by the illuminated area, the shape of the light beam and the lighting intensity. Thus, the shape of the light beam (called in English "Low Beam") for low beam is wider than the shape of the light beam (called in English "High Beam") for high beam, while high beam makes it possible to illuminate the road in front of the vehicle further than dipped beam. The shape of the light beam for low beam has a cut-off, while that for high beam it does not have a cut-off.

Figures 7a and 7b respectively illustrate in non-limiting examples the shape of a lighting beam of a dipped beam headlight (referenced LB), and the shape of a lighting beam of a main beam headlight (referenced HB).

The light device 2 has an optical axis AA’ illustrated in Figures 2a to 3c.

In non-limiting embodiments, the light device 2 is arranged at the front of the vehicle 1, on one of the sides of the motor vehicle 1, at the bottom of the windshield of the motor vehicle 1, or at the bottom of the hood of the motor vehicle 1.

In a non-limiting variant embodiment illustrated in the , the light device 2 is arranged on one of the sides of the vehicle 1, in particular on a side face of the motor vehicle 1. In a non-limiting example, it is arranged on the outside in the wing which may include a protuberance for this purpose to hide it from an outside observer. In a non-limiting example, the light device 2 is arranged in an area located between an external rearview mirror and a front wheel.

The lighting device 2 comprises a plurality of light sources 4.

The lighting device 2 comprises at least two light sources 4.

In a non-limiting embodiment illustrated in FIGS. 2a to 3c, it comprises at least three separate light sources 4a, 4b, 4c. This makes it possible to obtain the brightness required according to the regulations in force for high beams and dipped beams.

This non-limiting embodiment is taken as a non-limiting example in the remainder of the description.

As illustrated in FIGS. 2a to 3c, the light sources 4a, 4b, 4c may be connected to a printed circuit board 6. It will be noted that the three light sources 4a, 4b, 4c are arranged on the same printed circuit board 6 or on different printed circuit boards but arranged on the same plane to be at the same level or on different planes to be at different levels.

The printed circuit board 6 may be held by a support 7 possibly comprising a heat sink.

A light source 4 is configured to produce a light beam F. The light beam F is a monochromatic light beam F.

In a non-limiting embodiment, the light source 4 is a light-emitting diode or a laser diode.

By light-emitting diode is meant any type of light-emitting diode, whether in non-limiting examples LEDs (“Light Emitting Diode” in English), OLEDs (“Organic LED” in English), AMOLEDs (“Active-Matrix-Organic LED” in English), or FOLEDs (“Flexible OLED” in English). The light from such a light source 4 in the absence of a wavelength converter only comprises rays of a single wavelength, that is to say that it only comprises light rays having a specific color.

Thus, the three light sources 4a, 4b, 4c of FIGS. 2a to 3c are configured to respectively produce three monochromatic light beams F having wavelengths λa, λb, λc distinct from each other and therefore different colors from each other. It will be noted that to lighten the figures and the description, the light beams of the different light sources 4a, 4b, 4c are referenced F.

• une première source lumineuse 4a configurée pour émettre une lumière monochromatique de couleur rouge ayant une longueur d’onde λ_a comprise entre 620 nm (nanomètres) et 700 nm,
• une deuxième source lumineuse 4b configurée pour émettre une lumière monochromatique de couleur verte ayant une longueur d’onde λ_b comprise entre 490 nm et 570 nm,
• une troisième source lumineuse 4c configurée pour émettre une lumière monochromatique de couleur bleue ayant une longueur d’onde λ_c comprise entre 450 nm et 490 nm.

In a non-limiting exemplary embodiment, the lighting device 2 comprises:

• a first light source 4a configured to emit a monochromatic light of red color having a wavelength λ _a between 620 nm (nanometers) and 700 nm,
• a second light source 4b configured to emit a monochromatic light of green color having a wavelength λ _b between 490 nm and 570 nm,
• a third light source 4c configured to emit a monochromatic light of blue color having a wavelength λ _c between 450 nm and 490 nm.

Thus, each of the three light sources 4a, 4b, 4c is configured to emit a monochromatic light having a wavelength λ different from the other two light sources 4a, 4b, 4c so as to produce a white light.

This produces a white light beam which is composed of the three light beams F, and complies with the regulations in force for main beam and dipped beam headlights.

The light device 2 also comprises an optical device 14 juxtaposed with the three light sources 4 so that each light beam F produced respectively by them passes through the optical device 14, it is thus arranged opposite the three light sources 4.

The optical device 14 comprises a plurality of meta-lenses 15.

The optical device 14 comprises at least two meta-lenses 15.

In a non-limiting embodiment, the optical device 14 comprises three meta-lenses 15a, 15b, 15c configured to modify at least one optical property of the wavefront of the light beam F produced by each of the three light sources 4a, 4b, 4c.

A meta-lens 15 is described below. The description of the meta-lens 15 applies to each meta-lens 15a, 15b, 15c of FIGS. 2a to 3c.

In general, the meta-lens 15 has the advantage of being flat, extremely thin, very light and compact, which greatly facilitates its integration into lighting devices in general. This also makes it possible to miniaturize the lighting device 2. For example, an individual meta-lens 15 can cover an area of between 4mm² and 100mm².

The meta-lens 15 may have an elliptical shape, in particular a circular shape, or a polygonal shape, in particular a quadrilateral shape. According to a non-limiting embodiment, the meta-lens 15 may have a square or rectangular shape or even a diamond shape.

The meta-lens 15 of the optical device 14 generally comprises a nanostructure 16 (illustrated in the ) configured to modify the shape of the wavefront of the light beam F produced by the light source 4 and passing through the optical device 14, and more particularly to modify the amplitude and therefore the intensity and/or the phase and therefore the direction of propagation of the light beam F.

In the context of a stack s’, the meta-lenses 15a, 15b, 15c of the optical device 14 generally comprise a nanostructure 16 specific to each meta-lens 15a, 15b, 15c and configured to modify the shape of the wavefront of the light beams F produced by the light sources 4a, 4b, 4c and passing through the optical device 14, and more particularly to modify the amplitude and therefore the intensity and/or the phase and therefore the direction of propagation of the light beam F. For the sake of simplification, the same reference 16 will be used in the description for each of the nanostructures of each of the meta-lenses 15a, 15b, 15c.

In a non-limiting embodiment, an individual meta-lens 15 (substrate 160 and nanopillars 17 included described later) comprises a diameter between 2 mm (millimeters) and 4 mm.

It should be noted that the fabrication and calculation of the nanostructure 16 of the meta-lens 15 is simpler with a monochromatic light source 4.

These nanopillars 17 are generally manufactured by nanostructuring, that is, by electron beam lithography or by nanoimprint lithography in thin layers and arranged in the form of quasi-periodic networks.

These nano-sized nanopillars 17 may comprise dielectric materials with a high refractive index, for example a refractive index greater than two.

The nanostructure 16 of the meta-lens 15 generally comprises an arrangement of nanopillars 17 on the surface.

More particularly, the nanostructure 16 may comprise a quasi-periodic network of nanopillars 17 on the surface. By “quasi-periodic” is meant here that the nanopillars within the nanostructure 16 are placed at more or less regular intervals from each other and that they are repeated periodically, and that they are of different sizes (their diameter varies here). We will speak of a periodic network if their sizes are equal. As a non-limiting example, the nanopillars 17 of a nanostructure 16 may be placed at intervals of between 300 nm and 500 nm. In a non-limiting example, they are placed with an interval of 400 nm. In other words, the centers of two neighboring nanopillars 17 are 400 nm apart.

The nanopillars 17 are for example placed on a transparent substrate 160. The material of the transparent substrate 160 is chosen to provide suitable structural support and to allow a majority of the light passing through it to pass through. Such material substrates include for example fused silica, borosilicate glass or even glasses based on rare earth oxides.

As illustrated in the , in one embodiment, the substrate 160 has a first refractive index n1 and the nanopillars 17 have a second refractive index n2. The first refractive index n1 of the substrate is lower than the second refractive index n2 of the nanopillars 17. These refractive indices n1 and n2 also have an influence on the light beam F which passes through the nanopillars 17 of the nanostructure 16 of the meta-lens 15 and therefore make it possible to modify at least one of the optical properties of the wavefront.

The meta-lens 15 is configured to receive a light beam F from a light source 4 and modify its propagation phase φ so that the light beam F is oriented in a given propagation direction P (illustrated in the ). In the following description, the propagation phase φ is otherwise called phase φ.

In general, the nanopillars 17 may have sections of different sizes from each other. Indeed, the shape and size of the section of a nanopillar 17 of the nanostructure 16 has an impact on the propagation speed of the light beam F which passes through said nanopillar 17, thus modifying at least one of the optical properties of the wavefront of said light beam F which passes through the optical device 14.

The nanopillars 17 may in particular have a cylindrical shape; in this case, they may comprise a base bs (illustrated in the ) of circular shape. The diameter may vary from one nanopillar 17 to another. An example of an arrangement of nanopillars 17 of cylindrical shape with a determined height and different diameters is illustrated in the . The nanopillars 17 thus have a different size (via their diameter). Alternatively, the shape of the base bs could be different from a circular shape, for example a polygonal base, in particular square or rectangular, or even an oblong or elliptical base.

Furthermore, these nanopillars 17 can have the same height h (illustrated in the ) configured to modify the phase of the light beam F produced by the light source 4. For a monochromatic light having a given wavelength λ, the ideal height of the nanopillars 17 can be determined to obtain the highest possible transmission rate.

Thus, the transmission rate through the optical device 14 comprising a meta-lens 15 with a monochromatic light beam F is for example greater than 75% and in particular greater than 80%, or even higher.

Thus, more than 80% of the light emitted by the light source 4 can be used to illuminate the road in front of the motor vehicle 1.

The height h of the nanopillars 17 allows the phase to be controlled between 0 and 2π.

In a non-limiting embodiment, the light source 4 can be configured to emit a light beam with a wavelength λ equal to 590 nm. In this non-limiting example, the refractive index n1 of the material used for the substrate 160 is equal to 1.52 while the refractive index n2 for the nanopillars is equal to 2.36. Still in this non-limiting example, the height h of the nanopillars 17 is 600 nm and the diameter of the nanopillars 17 can be between 50 nm and 150 nm.

The distribution of the nanopillars 17 within the nanostructure 16 of the meta-lens 15 can be optimized to contribute to a change in the propagation direction P (illustrated in the ) of the light beam F. In other words, the distribution of the nanopillars 17 within the nanostructure 16 can be specifically configured to influence the propagation direction P of the light beam F in order to modify the orientation of the light beam F at the exit of the meta-lens 15.

More generally, in a non-limiting embodiment, a meta-lens 15 comprises a quasi-periodic array of nanopillars 17 having different diameters (namely different radii r) so as to influence the speed of propagation of light through the nanopillars 17 so as to modify at least one of the optical properties of the wavefront of the light beam F which passes through the meta-lens 15. Indeed, for two nanopillars 17 having the same height h and different diameters, the nanopillar 17 having a larger diameter will slow down the propagation of the light which passes through it more than the nanopillar with a smaller diameter.

This makes it possible in particular to direct the light beam F at the exit of the lighting device 2.

Furthermore, in the case of a quasi-periodic array, the arrangement of the nanopillars 17, namely the distribution of their radii r, in the nanostructure 16 of the meta-lens 15 can be configured so that the latter has a structure, suitable for projecting a light image with fixed contours onto a surface at a certain distance, called the regulatory distance, for example usually at 25 meters. In the remainder of the description, the light image is otherwise called an image.

Thus, the orientation of the light beams F by the nanostructures 16 of the different meta-lenses 15 makes it possible to obtain light images projected onto a surface at a certain regulatory distance, the light images forming a lighting beam for the high beam function or the low beam function.

To verify that the lighting beam is regulatory, the projection on this surface located at this regulatory distance, perpendicular to the optical axis AA’, is checked by measuring the luminous intensity of the lighting beam at certain so-called regulatory points which must not exceed certain regulatory limits; and by verifying the shape of the lighting beam formed by the projected images.

If the projection is correct, this corresponds to having a beam of light that illuminates the road at a certain distance.

In the context of a high beam, as is known to those skilled in the art, the lighting beam has an elliptical shape.

In the context of a European type dipped beam headlight for right-hand driving, as is known to those skilled in the art, the lighting beam has a semi-elliptical shape with a cut-off having a first portion above which there is no light, and a second portion above which there is light.

In the context of an American type dipped beam headlight, as is known to those skilled in the art, the lighting beam has a semi-elliptical shape with a cut-off above which there is no light.

Thus, unlike a dipped beam light, a main beam light corresponds to a set of light images without a contrast line which is the cut-off.

If one does not wish to illuminate above the contrast line, the light beams F from the light sources 4 are oriented below this contrast line by means of the meta-lenses 15.

It should be noted that to produce a lighting beam for a dipped beam, one or more sets of light sources 4 are used.

To create a lighting beam for a high beam, either a complete dedicated lighting beam is created, or a high beam lighting beam is created that is said to complement the dipped beam lighting beam.

For the complete dedicated lighting beam, another set or sets of 4 light sources are used.

For the additional lighting beam, the 4 light sources dedicated to the dipped beam are used, and 4 additional dedicated light sources to complete the lighting beam of the dipped beam and thus form the lighting beam of the main beam. This allows for less energy consumption and a smaller surface area for the 4 light sources compared to the solution of a complete main beam lighting beam.

The light beams F oriented by each meta-lens 15 will be oriented towards the surface at the regulatory distance to form the illumination beam. Thus, each nanostructure 16 of each meta-lens 15 of the optical device 14 will be designed for a specific orientation of a light beam F so that all of the light images at the output of the meta-lenses 15 form the desired regulatory illumination beam.

The nanopillars 17 are described in more detail below.

• un rayon r (illustré sur les figures 8 et 9),
• une hauteur h (illustrée sur les figures 8 et 9),
• un pas ps’ (illustré sur la ) entre deux nanopiliers 17. Le pas ps’ représente la fréquence de répétition des nanopiliers 17,
• une matière avec un indice de réfraction n2 (illustré sur la ),
• une base bs (illustrée sur la ).

The nanopillars 17 are defined by parameters including:

• a radius r (illustrated in figures 8 and 9),
• a height h (illustrated in figures 8 and 9),
• a ps' step (illustrated on the ) between two nanopillars 17. The step ps' represents the repetition frequency of the nanopillars 17,
• a material with a refractive index n2 (shown in the ),
• a bs base (illustrated on the ).

Note that the step ps' is defined between the two longitudinal axes (illustrated in broken lines on the ) of two adjacent nanopillars 17. In a non-limiting embodiment illustrated in the , the nanopillars 17 have a circular base bs.

In a non-limiting embodiment, the nanopillars 17 are made of silicon nitride siN. This material is easy to work with and pollutes less in terms of dust compared to other materials that can be used for the nanopillars 17 such as, in non-limiting examples, titanium dioxide (TiO2) or hafnium oxide (HfO2).

In a non-limiting exemplary embodiment, on a substrate 160 with a thickness E=5 millimeters, a 70 nanometer layer of siN can be deposited and the siN layer etched to obtain the nanopillars 17.

The nanopillars 17 of each meta-lens 15 make it possible to modify the propagation phase φ of a light beam F passing through them. In other words, they add a phase delay. The result is that the light beam F is deflected, giving it a desired propagation direction P.

All the light beams F thus deflected make it possible to form a lighting beam for a regulatory main beam or dipped beam.

It should be noted that the regulatory distance depends on the phase shift introduced by the nanopillars 17. Thus, the light is redirected towards the surface at the regulatory distance. The deflected light beams F are transmitted with a very good light transmission rate. There is thus very little loss of light.

To adjust the propagation direction P, the phase shift within a light beam F is spatially controlled, which amounts to controlling the gradient of the phase change φ of the light beams F. This is done using nanopillars 17.

For this purpose, in a non-limiting embodiment illustrated in the , the nanopillars 17 have different radii r and the same height h. For reasons of readability of the figure, only one height h has been referenced and only one radius r has been referenced.

It should be noted that the smaller the radius r, the less material a nanopillar 17 contains, which has the consequence of changing the phase φ to a minimum, which amounts to having a small phase delay. On the contrary, when the radius r is larger, the more material a nanopillar 17 contains, which has the consequence of changing the phase φ more significantly, which amounts to having a larger phase delay.

As illustrated in the , the nanopillars 17 have a radius r that increases from left to right. Each nanopillar 17 will cause a different phase delay φ compared to its neighbor. The larger the radius r, the greater the phase delay φ. The radius r thus acts on the phase φ of the light beam F. The radii r being smaller on the left, the phase delays on the left are smaller and the light will be less delayed on the left than on the right.

As a reminder, light propagates perpendicular to the wavefront. Classically, on the same line of the wavefront there is 0 phase delay. As can be seen in the , the input wavefront Fo at the input of the meta-lens 15 (also called the incident wavefront Fo) is plane and perpendicular to the substrate 160 of the meta-lens 15.

Each nanopillar 17 introduces a phase delay φ different from its neighbor, because they all have a different diameter, this differential phase delay φ then causes a deformation of the wavefront.

As can be seen on the , the emerging wave front Fo' is deformed which therefore causes a deviation of the emerging light beam F after the meta-lens 15.

Thus, at the exit of a meta-lens 15, the light which always propagates perpendicular to the wave front, here the emerging wave front Fo’ which is inclined, will be oriented according to a given propagation direction P. Consequently, we obtain an orientation of the light according to a propagation direction P which has changed thanks to the phase shift of the light.

It will be noted that the emerging wavefront Fo’ has been delayed in a progressive and linear manner. Each nanopillar 17 is configured to achieve a phase change φ of the linearly evolving light, namely a linear phase shift. This makes it possible to obtain a planar emerging wavefront Fo’. It will be noted that a phase shift between 0 and 2π is equivalent. It is therefore not necessary to create a linear phase shift all along the input wavefront Fo to obtain a continuous deviation. A phase shift between 0 and 2π can be achieved as many times as necessary. Thus, a linear phase shift between 0 and 10π is equivalent to five linear phase shifts between 0 and 2π.

Note that the phase φ is modulated between 0 and 2π. Note that with a phase φ = 0, there is no delay. With φ = π, there is a delay of λ/2. From the point of view of the meta-lens 15, as soon as we have φ = 2π, we return to a radius r of a nanopillar 17 corresponding to 0, and therefore to the same nanopillar 17 to avoid having too large differences between the radii r. Thus, the meta-lens 15 comprises several sets of nanopillars 17 defined so as to obtain a phase shift of the light with a phase modulated between 0 and 2π.

The height h of the nanopillars 17 allows to control the phase φ between 0 and 2π for a given wavelength λ. With the right height h defined, all phase changes can be made between 0 and 2π.

As explained previously, the radius r allows to control the phase φ of the light beam Fx.

The other parameters, namely the height h, the pitch ps’, the material of the nanopillars 17, are defined to maximize the transmission rate of light through the nanopillars 17. Maximizing the transmission rate means minimizing the absorption of light by the material of the nanopillar 17. Thus, these other parameters are determined to have a minimal absorption over the range where the radius r is varied to have a phase shift (also called phase difference) between 0 and 2π.

By calculation, for a nanopillar 17 we set a given height h and a given pitch ps’, and its material which is in a non-limiting example Silicon Nitride siN whose refractive index n2=2.04. In a non-limiting example, h=1.35μm and ps’=0.450μm. Working at a constant height h makes it easier to manufacture the nanopillars 17. With a constant height h, the design of the nanopillars 17 must be adapted to have a phase shift between 0 and 2π and at the same time have the highest possible light transmission to conserve a maximum of light.

For the fixed height h and the fixed step ps’, we establish the curves of light transmission as a function of the radius r, and of phase shift as a function of the radius r. The curves in Figures 10 and 11 illustrate the phase shift and the light transmission for the best compromise for the chosen constant height h and this for a given wavelength λ. It should be noted that this compromise changes if the wavelength λ changes.

On the , in a non-limiting example, for a height h=1.35µm (micrometers), we can thus observe the phase variation φ in radians (on the ordinate) between 0 and 9 as a function of the radius r (on the abscissa) of the nano-pillars 17 which varies between 0.04 and 0.15 μm, for a given wavelength λ, here for λ=590nm in the non-limiting example illustrated.

On the , in a non-limiting example, for a height h=1.35 µm, we can thus observe a variation in light transmission Tx (on the ordinate) between 0 and 1 as a function of the radius r (on the abscissa) of the nanopillars 17 which varies between 0.04 and 0.15 μm, for the given wavelength λ, here 590 nm. At the value 0 for the transmission, the light does not pass. At the value 1, for the transmission all the light passes.

With these two curves, we can therefore search and find what is the height h and the radius r of the nanopillars 17 which makes it possible to obtain a phase shift control dynamic while maximizing the transmission of light by the nanopillars 17, and remaining manufacturable. We can thus find the values of all the parameters of a nanopillar 17 to obtain the phase shift (or phase difference) and possible transmission values, and in particular a transmission rate close to 1 for a given wavelength λ. It should be noted that if the results are not satisfactory, the procedure can be repeated by setting another value for the height h.

A first non-limiting embodiment of a light device 2 is illustrated in FIGS. 2a and 2b. A second non-limiting embodiment of a light device 2 is illustrated in FIGS. 3a to 3c.

As illustrated in Figures 2a to 3c, the three meta-lenses 15a, 15b, 15c are arranged at a distance d from said at least one light source 4a, 4b, 4c, d being between 2 and 3 mm in a non-limiting embodiment.

Each meta-lens 15a, 15b, 15c thus comprises a nanostructure 16 which is specific to it. The nanopillars 17 of the nanostructure 16 specific to each meta-lens 15a, 15b, 15c have the same height h and the height h of the nanopillars 17 is specific to each meta-lens 15a, 15b, 15c.

The optical properties of a meta-lens 15a, 15b, 15c are mainly defined by the wavelength of the monochromatic light source 4a, 4b, 4c used, by the refractive index(es) n1 and n2 of the materials used for the substrate 160 and for the nanopillars 17, by the dimensions of the nanopillars 17 and by the distribution of said nanopillars 17 within the nanostructure 16 specific to each meta-lens 15a, 15b, 15c. In other words, the density of material in the nanostructure 16 of each meta-lens 15a, 15b, 15c defines the effect that the meta-lens 15a, 15b, 15c has on the light beam F passing through it.

As illustrated in Figures 2a and 2b, according to the first non-limiting embodiment of the light device 2, the light device 2 comprises at least one set g of three light sources 4a, 4b, 4c juxtaposed next to each other (in other words side by side), and at least one stack s' of three meta-lenses 15a, 15b, 15c arranged opposite said set g, each light source 4a, 4b, 4c being configured to emit light of a different color from the other light sources 4a, 4b, 4c of said at least one set g.

The light beams F of said at least one set g of three light sources 4a, 4b, 4c pass through the entire stack s’ of meta-lenses 15a, 15b, 15c.

Thus, in a non-limiting example, three light sources 4a, 4b, 4c are configured to respectively emit a monochromatic light of red color R (λa=620nm in a non-limiting example), of green color V (λb=550nm), and of blue color B (λc=450nm in a non-limiting example) so as to obtain a white color. Thus, we have a set g called RGB.

The three meta-lenses 15a, 15b, 15c are designed to be tuned respectively with different wavelengths λa, λb, λc. In a non-limiting example, they are tuned respectively to the wavelengths λa (red), λb (green), λc (blue).
It will be noted that stacking the meta-lenses 15a, 15b, 15c on top of each other does not greatly increase the volume in thickness of the light device 2, the meta-lenses 15a, 15b, 15c being very thin.

At the third meta-lens 15c of the stack s’, all the colors are mixed. Thus, at the output of the stack s’, we obtain the color white.

Note that the colors blue, green and red can be replaced by the colors yellow, magenta and cyan to obtain the color white.

According to a first non-limiting variant embodiment illustrated in the , the light device 2 comprises a single set g of three light sources 4a, 4b, 4c and a single stack s' of three meta-lenses 15a, 15b, 15c.

According to a second non-limiting variant embodiment illustrated in the , the lighting device 2 comprises two sets g1, g2 of three light sources 4a, 4b, 4c and two stacks s1', s2' of three respectively corresponding meta-lenses 15a, 15b, 15c. This second non-limiting embodiment variant makes it possible to produce a lighting beam for a main beam and a dipped beam.

For simplification, on the , we use the same references 4a, 4b, 4c for the two sets g1, g2 of three light sources and for the two stacks s1', s2' of three meta-lenses 15a, 15b, 15c.

It should be noted that the stacked arrangement makes it possible to do without a separation wall (which are physical walls) because each meta-lens 15a, 15b, 15c only processes light having the wavelength λ to which it is tuned. Thus, the meta-lens 15a will only process red light, the meta-lens 15b will only process green light, and the meta-lens 15c will only process blue light. Thus, the light beams F from each light source 4a, 4b, 4c do not mix with another light beam F if the meta-lens 15 has been designed to have very precise selectivity on the desired wavelength λ. This avoids a stray light phenomenon called “light cross talk”.

Furthermore, since white light is obtained at the third meta-lens 15c of the stack, there is no effect of colored edges of the lighting beam, even when the vehicle 1 is near a wall.

In a second non-limiting embodiment illustrated in FIGS. 3a to 3c, the light device 2 comprises at least one set g of light sources 4 juxtaposed next to each other and at least one set g' of corresponding meta-lenses 15 juxtaposed next to each other. Each set g comprises at least two light sources 4, and each set g comprises at least two meta-lenses 15.

The light device 2 comprises as many meta-lenses 15 as light sources 4 and each light source 4 is associated with a meta-lens 15 which is specific to it.

The multitude of meta-lenses 15 and the multitude of light sources 4 are arranged relative to each other so that each light beam F produced by one of the light sources 4 passes through the meta-lens 15 with which said light source 4 is associated.

As illustrated in the , in a first non-limiting variant embodiment of this second non-limiting embodiment, the light device 2 comprises at least three sets ga, gb, gc of three light sources 4 juxtaposed next to each other (i.e. side by side) and at least three sets g'a, g'b, g'c of three corresponding meta-lenses 15a, 15b, 15c juxtaposed next to each other.

The three sets ga, gb, gc are arranged next to each other.

Each set ga, gb, gc of light sources 4a, 4b, 4c is configured to emit monochromatic light of a different color from the other sets ga, gb, gc. In other words, each light source 4 of each set g emits the same monochromatic light as the other two light sources 4 of the same set g.

In a non-limiting example, the three light sources respectively denoted 3x4a, 3x4b, 3x4c of each set ga, gb, gc are respectively configured to emit a monochromatic light of red color R (λa=620nm in a non-limiting example), of green color V (λb=550nm in a non-limiting example), and of blue color B (λc=450nm in a non-limiting example) so as to obtain a white color.

Thus, the first set ga comprises three light sources 4a configured to emit a monochromatic light of red color, the second set gb comprises three light sources 4b configured to emit a monochromatic light of green color, and the third set gc comprises three light sources 4c configured to emit a monochromatic light of blue color.

Thus, the three meta-lenses denoted 3x15a, 3x15b, 3x15c respectively associated with the three sets ga, gb, gc of light sources 4 are designed respectively for the three different wavelengths λa, λb, λc, in other words they are tuned to these three wavelengths λa, λb, λc.

As illustrated in the , in a second non-limiting variant embodiment of this second non-limiting embodiment, the light device 2 comprises at least one set g of three light sources 4a, 4b, 4c juxtaposed next to each other and at least one set g' of three corresponding meta-lenses 15a, 15b, 15c juxtaposed next to each other. Each light source 4a, 4b, 4c of the set g is configured to emit a monochromatic light of a different color from the other light sources 4a, 4b, 4c of the same set g.

Thus, the three light sources 4a, 4b, 4c of the same set g are configured to respectively emit a monochromatic light of red color R (λa=620nm in a non-limiting example), of green color V (λb=550nm), and of blue color B (λc=450nm in a non-limiting example) so as to obtain a white color.

Thus, the three meta-lenses 15a, 15b, 15c are designed for the three different wavelengths λa, λb, λc respectively, in other words they are tuned to these three wavelengths λa, λb, λc.

There illustrates the lighting device 2 which comprises at least three sets g1, g2, g3 of three light sources 4a, 4b, 4c juxtaposed next to each other and at least three sets g'1, g'2, g'3 of three corresponding meta-lenses 15a, 15b, 15c juxtaposed next to each other.

Each light source 4a, 4b, 4c of each set g1, g2, g3 is configured to emit a monochromatic light of a different color from the other light sources 4 of the same set g1, g2, g3.

Thus, the first set g1 comprises three light sources 4a, 4b, 4c configured to respectively emit a monochromatic light of red color R (λa=620nm in a non-limiting example), of green color V (λb=550nm), and of blue color B (λc=450nm in a non-limiting example) so as to obtain a white color. The same applies to the second set g2 and the third set g3.

Thus, the first set g1’ comprises three meta-lenses 15a, 15b, 15c designed for the three different wavelengths λa, λb, λc respectively. The same applies to the second set g’2 and the third set g’3.

This second non-limiting variant embodiment makes it possible to have a white image at a closer distance from the exit of the meta-lenses 15 compared to the first non-limiting variant embodiment.

It should be noted that the use of a white light source is not possible because it has a continuous spectrum of wavelengths which is difficult to separate into three different wavelengths to match them to the meta-lenses 15a, 15b, 15c.

In a non-limiting embodiment, in the case of several light sources 4, the lighting device 2 comprises a collimator per light source 4. This prevents a light beam F from a light source 4 from mixing with another light beam F from another light source 4. This avoids a phenomenon called “light cross talk”. Consequently, this avoids a blurred lighting beam.

This applies to the first non-limiting embodiment in stacking to avoid the overflow of one color onto the other before entering the stack of meta-lenses 15 if the selectivity of the meta-lens 15 on the desired wavelength λ is not precise enough. This also applies to the second non-limiting embodiment side by side to avoid colored stray light. For example, it is prevented that a light beam F of red color for example reaches a meta-lens 15 tuned to the green color. If there is no collimator, it is necessary to provide separation walls, if possible absorbent.

When the meta-lenses 15a, 15b, 15c are arranged side by side according to the first non-limiting embodiment of 3a, 3b and 3c, the light beams F of the three light sources 4a, 4b, 4c are oriented towards the same location R as illustrated in the to superimpose them and obtain white light. This is obtained by a different linear phase shift for each light beam F of the associated light sources 4,a, 4b, 4c, linear phase shift obtained thanks to the nanopillars 17 as described previously. This location R must be at the regulatory distance, for example 25 meters. On the only three light sources 4a, 4b, 4c and three corresponding meta-lenses 15a, 15b, 15c are illustrated, but the also applies for sets g and g' of 3a by replacing the three light sources 4a, 4b, 4c of the by the three sets ga, gb, gc of the and replacing the three meta-lenses 15a, 15b, 15c with the three sets g'a, g'b, g'c of the . There also applies to the sets g, g' of the 3c, the illustrating a set g1, g2, g3 of the , and a set g'1, g'2, g'3 of the .

The light beams F of the three light sources 4 will mix so as to obtain white light for the lighting beam of the main beam or the dipped beam. The white light is obtained at a certain distance from the vehicle 1, which is the regulatory distance for the main beam or the dipped beam.

However, at a closer distance to vehicle 1, the light beams F do not yet mix or do not mix completely. We can then observe colored edges on the lighting beam which will then not be regulatory. We can see these colored edges, in particular when vehicle 1 parks near a wall and the lighting beam is then projected onto this wall.

Of course, the description of the invention is not limited to the embodiments described above and to the field described above.

Thus, the invention described has in particular the following advantages.

It is thus possible to arrange such a lighting device 2 in unusual locations, while making it possible to illuminate an area at the front of the motor vehicle 1 to provide a high beam function or a low beam function.

Thus, the lighting device 2 according to the invention is configured to provide the functions of a main beam and a dipped beam while improving the aerodynamics of the motor vehicle to reduce its energy consumption and its CO2 emissions rate.

The lighting device 2 according to the invention is more compact, lighter and more robust and can be easily integrated into a motor vehicle 1. In particular, the lighting device 2 is very compact along an axial distance along its optical axis AA’.

Such a miniaturized lighting device 2 according to the invention is configured to simply project lighting zones at the front of the vehicle 1 for high beam functions or a low beam function.

Such a miniaturized lighting device 2 according to the invention contributes significantly to a reduction in the weight of the motor vehicle 1 in which it is integrated and can also allow a more aerodynamic design of said vehicle to reduce its energy consumption and its CO2 emissions rate.

Claims (13)

Lighting device (2) for a motor vehicle (1), the lighting device (2) being configured to provide a high beam function and/or a low beam function, the lighting device (2) being characterized in that it comprises:

• a plurality of light sources (4a, 4b, 4c) configured to each produce a monochromatic light beam (F);
• an optical device (14) arranged facing the plurality of light sources (4a, 4b, 4c) so that the light beams (F) pass through the optical device (14), said optical device (14) comprising a plurality of meta-lenses (15a, 15b, 15c) configured to respectively modify at least one property of the wavefront of each light beam (F) so as to orient it in a propagation direction (P).

Luminous device (2) according to claim 1, characterized in that the luminous device (2) comprises at least three light sources (4a, 4b, 4c) and at least three meta-lenses (15a, 15b, 15c). Luminous device (2) according to claim 2, characterized in that it comprises a first light source (4a) configured to emit a monochromatic light of red color having a wavelength between 620 nm and 700 nm, a second light source (4b) configured to emit a monochromatic light of green color having a wavelength between 490 nm and 570 nm, and a third light source (4c) configured to emit a monochromatic light of blue color having a wavelength between 450 nm and 490 nm. Illumination device (2) according to any one of the preceding claims 1 to 3, characterized in that said illumination device (2) comprises at least one set (g) of light sources (4a, 4b, 4c) juxtaposed next to each other and at least one stack (s') of meta-lenses (15a, 15b, 15c) arranged opposite said set (g) so that the light beams (F) of the plurality of light sources (4a, 4b, 4c) pass through said at least one stack (s') and that each light source (4a, 4b, 4c) is configured to emit light of a different color from the other light sources (4a, 4b, 4c) of said at least one set (g), and the meta-lenses (15a, 15b, 15c) are designed to be tuned to wavelengths (λa, λb, λc) different. Luminous device (2) according to claim 4, characterized in that said luminous device (2) comprises two sets (g1, g2) of light sources (4a, 4b, 4c) juxtaposed next to each other and two stacks (s1', s2') of meta-lenses (15a, 15b, 15c) arranged respectively opposite the two sets (g) (g1, g2) of light sources (4a, 4b, 4c). Luminous device (2) according to any one of the preceding claims 1 to 3, characterized in that the luminous device (2) comprises at least one set (g) of light sources (4a, 4b, 4c) juxtaposed next to each other and a set (g) of meta-lenses (15a, 15b, 15c) juxtaposed next to each other so that the light beam (F) produced by each light source (4a, 4b, 4c) passes through the meta-lens (15a, 15b, 15c) with which said light source (4) is associated. Luminous device (2) according to claim 6, characterized in that said luminous device (2) comprises at least three sets (ga, gb, gc) of light sources (4a, 4b, 4c) juxtaposed next to each other and at least three sets (g'a, g'b, g'c) of corresponding meta-lenses (15a, 15b, 15c) juxtaposed next to each other, each set (ga, gb, gc) of light sources (4a, 4b, 4c) being configured to emit a monochromatic light of a different color from the other sets (ga, gb, gc). Luminous device (2) according to claim 6, characterized in that said luminous device (2) comprises at least three sets (g1, g2, g3) of light sources (4a, 4b, 4c) juxtaposed next to each other and at least three sets (g'1, g'2, g'3) of corresponding meta-lenses (15a, 15b, 15c) juxtaposed next to each other, each light source (4a, 4b, 4c) of each set (g1, g2, g3) being configured to emit a monochromatic light of a different color from the other light sources (4a, 4b, 4c) of the same set (g1, g2, g3). Luminous device (2) according to any one of the preceding claims, characterized in that each meta-lens (15a, 15b, 15c) comprises a nanostructure (16) comprising an arrangement of nanopillars (17) on the surface and in that the nanopillars (17) of the nanostructure (16) specific to each meta-lens (15a, 15b, 15c) have the same height (h) and in that the height (h) of the nanopillars (17) is specific to each meta-lens (15). Luminous device (2) according to claim 9, characterized in that the nanopillars (17) of the same meta-lens (15a, 15b, 15c) have the same height (h) and have different diameters from each other, and are repeated periodically. Luminous device (2) according to claim 9 or claim 10, characterized in that the nanopillars (17) have a cylindrical shape and in that the diameter of the nanopillars (17) is between 100 nm and 320 nm. Motor vehicle (1) characterized in that it comprises at least one lighting device (2) according to one of the preceding claims. Motor vehicle according to the preceding claim, characterized in that said at least one light device (2) is arranged on a side face (3) of the motor vehicle (1).