Lighting device for a vehicle, configured to project an image onto the ground
The vehicle lighting device addresses low luminous efficacy by using a collimating optic, meta-lens matrix, and folding optic to project images onto the ground with minimal light loss, enhancing efficiency and effectiveness.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- VALEO VISION SA
- Filing Date
- 2025-12-01
- Publication Date
- 2026-06-11
Smart Images
Figure EP2025085014_11062026_PF_FP_ABST
Abstract
Description
Vehicle lighting device configured to project an image onto the ground
[0001] The present invention relates to a lighting device for vehicles. It finds a particular, but not limiting, application in motor vehicles.
[0002] In the field of motor vehicles, a lighting device known to those skilled in the art comprises: - a monochromatic light source configured to emit light at a given wavelength forming a light beam, - a conventional light collimator configured to collimate the light, - a mask or slide with opaque and transparent areas, the latter being crossed by the collimated light to form the image, - a projection lens disposed downstream of the mask / slide and configured to project the image onto the ground.
[0003] One drawback of this state of the art is that the lighting device has low luminous efficacy. Indeed, between the emitted light and the light exiting the lighting device, there is a loss of more than 50%.
[0004] In this context, the present invention aims to provide a lighting device that solves the aforementioned problem.
[0005] To this end, the invention proposes a vehicle lighting device configured to project an image onto the ground, said lighting device comprising: - an array of monochromatic light sources configured to emit light at a given wavelength, said light forming a light beam;characterized in that said lighting device further comprises: - a collimating optic disposed opposite said matrix of light sources and configured to collimate said light and form a first collimated light beam composed of a plurality of collimated light sub-beams, - a meta-lens matrix comprising a plurality of meta-lenses and disposed opposite the collimating optic, each meta-lens being configured to orient a collimated light sub-beam along a propagation direction to obtain a part of a second collimated light beam forming said image, said meta-lens matrix being configured to project said image onto a plane parallel to said matrix, and - a folding optic disposed opposite the meta-lens matrix and configured to deflect the second collimated light beam along an orientation direction so as to project said image onto the ground.
[0006] Thus, as we will see in detail below, the light source array illuminates the collimating optics with monochromatic, uncollimated light. The collimating optics collimate this monochromatic, uncollimated light, which then illuminates the metal lens array. The collimated light is transmitted through the metal lens array, which operates at the monochromatic wavelength of the emitted light. This light is then projected onto the ground with high luminous efficiency using the refracting optics.
[0007] According to non-limiting embodiments, the vehicle lighting device may further comprise one or more additional features taken alone or in all technically possible combinations, from among the following.
[0008] According to a non-limiting embodiment, the collimating optic is a meta-lens or a matrix of meta-lenses configured to collimate light at a given wavelength, and whose diameter is adapted to that of the light beam.
[0009] According to a non-limiting embodiment, the collimating optics includes at least one lens or is an array comprising a plurality of groups of microlenses, each group being configured to collimate said light and create a collimated subbeam forming a part of said first collimated light beam.
[0010] According to a non-limiting embodiment, a group of microlenses is formed of a single microlens or two microlenses.
[0011] According to a non-limiting embodiment, each meta-lens of the array is arranged opposite each group of micro-lenses and is configured to orient the collimated sub-beam of said group along a propagation direction so as to form a part of said image.
[0012] According to a non-limiting embodiment, the meta-lenses have a size equal to a first step defined between two adjacent micro-lenses of two different adjacent groups.
[0013] According to a non-limiting embodiment, said metal lenses have a surface area less than or equal to 1 mm² 2 .
[0014] According to a non-limiting embodiment, said collimation optics has a thickness between 2mm and 3mm.
[0015] According to a non-limiting embodiment, the meta-lenses comprise nano-pillars defined by a radius, a height, and a second pitch between two nano-pillars.
[0016] According to a non-limiting embodiment, the folding optics is a diffraction grating or a microlens array.
[0017] According to a non-limiting embodiment, the folding optic has a thickness between 1mm and 3mm.
[0018] According to a non-limiting embodiment, the diffraction grating comprises a plurality of patterns distributed according to a periodicity T= λ / n*sinθ, with λ being said wavelength of the light emitted by the matrix of light sources, n a refractive index of light of the diffractive grating, and θ an angle of orientation.
[0019] According to a non-limiting embodiment, the patterns have a height close to said wavelength.
[0020] According to a non-limiting embodiment, said nano-pillars have different radii and the same height.
[0021] According to a non-limiting embodiment, the light source matrix comprises a plurality of light sources.
[0022] According to a non-limiting embodiment, the light sources can be activated independently of each other.
[0023] According to a non-limiting embodiment, the height of the diffraction grating patterns is approximately equal to 500nm.
[0024] According to a non-limiting embodiment, the wavelength is between 590nm and 610nm.
[0025] According to a non-limiting embodiment, said nano-pillars are made of Silicon Nitride.
[0026] In addition, a vehicle is proposed that includes a lighting device according to any of the preceding characteristics, said lighting device being located outside the vehicle.
[0027] The invention and its various applications will be better understood by reading the following description and examining the accompanying figures:
[0028] Laillustrate very schematically a lighting device for a vehicle according to a non-limiting embodiment of the invention, said lighting device comprising a matrix of light sources, collimation optics, a matrix of metal lenses, and a diffraction grating;
[0029] Laillustrate very schematically a first non-limiting embodiment of the light source matrix of the lighting device of the;
[0030] Laillustre a first non-limiting embodiment variant of a second non-limiting embodiment of the light source matrix of the lighting device of the;
[0031] Laillustrate very schematically a first non-limiting embodiment of the collimation optics of the luminous device of the;
[0032] Laillustre a first non-limiting embodiment variant of a second non-limiting embodiment of the collimation optics of the luminous device of the;
[0033] Laillustre une seconde variant de embodiment non limiting d'un seconde mode de embodiment de la collimation du dispositif lumineux de la;
[0034] Laest is a representation of a meta-lens of the luminous device according to a non-limiting embodiment, the meta-lens comprising a substrate and nano-pillars;
[0035] Laillustre an enlarged view of a plurality of nano-pillars of the meta-lens according to a non-limiting embodiment,
[0036] Laillustre shows a highly magnified view of a single nano-pillar of the meta-lens with a portion of the substrate,
[0037] The illustration of the nano-pillars of the meta-lens and the propagation direction of the collimated sub-beams produced by the collimation optics of the luminous device when they pass through said nano-pillars,
[0038] Laillustre a first curve indicating a phase variation as a function of the radius of a nano-pillar of a meta-lens of the luminous device of the,
[0039] Laillustre a second curve showing a variation in light transmission as a function of the radius of a nano-pillar of a meta-lens of the luminous device of the,
[0040] The diagram schematically illustrates a projection by the metal-lens matrix of the luminous device of an image onto a plane parallel to a substrate of said metal-lens matrix, said image comprising illuminated areas and shadow areas,
[0041] The diagram schematically illustrates a projection of the image onto the ground by the ground-projecting optics of the lighting device.
[0042] This schematically illustrates a first, non-limiting embodiment of the optical system for lowering the lighting device onto the ground.
[0043] Laillustrate schematically a second, non-limiting embodiment of the optical system for lowering the lighting device onto the ground,
[0044] The diagram schematically illustrates a vehicle comprising a lighting device, said lighting device being located outside the vehicle at the level of an exterior rearview mirror.
[0045] The diagram schematically illustrates a vehicle comprising a lighting device, said lighting device being located outside the vehicle, at the level of a lower door.
[0046] Identical elements, whether structural or functional, appearing on different figures retain the same references unless otherwise specified.
[0047] The vehicle lighting device 1 according to the invention is described with reference to figures 1 to 14.
[0048] In a non-limiting embodiment, the lighting device 1 is a lighting device of a vehicle 2 (illustrated in Figure 14). In a non-limiting embodiment, the vehicle 2 is a motor vehicle. A motor vehicle is defined as any type of motorized vehicle. This embodiment is taken as a non-limiting example in the following description. In the following description, the vehicle 2 is thus also referred to as motor vehicle 2. In a non-limiting variant of the embodiment, the vehicle 2 is a combustion engine, electric, or hybrid vehicle.
[0049] In the following description, the terms depth and thickness will be used interchangeably. Depth is understood along a longitudinal axis AA' (illustrated in the figure) which runs through the entire light device 1.
[0050] As will be seen below, since the light device 1 is relatively shallow, it is configured to be located outside the vehicle 2, i.e., outside the passenger compartment. In a first, non-limiting embodiment illustrated in Figure 1, it is positioned at the level of an exterior rearview mirror 20 of the vehicle 2, either right or left. In a second, non-limiting embodiment illustrated in Figure 1, it is positioned at the bottom of a door 21 of the vehicle 2. In a third, non-limiting embodiment not shown, it is positioned on the lower body of the vehicle 2.
[0051] The lighting device 1 is configured to project an image Im onto the ground 4 (illustrated in figures 1, 13 and 14) on which the vehicle 2 is located. In a non-limiting embodiment, the image Im allows for the production of static or dynamic signage on the ground 4 around the vehicle 2. In other words, the lighting device 1 is configured to project an image Im onto the ground 4, said image Im being a static image or an animated image.
[0052] In non-limiting examples, the production of static or dynamic illuminated signage around vehicle 2 is: - a welcome scenario function. The welcome scenario function may include dynamic signage around vehicle 2, also called "dynamic carpet projection," in which an animated image is projected. The animated image is thus formed from several images (Im). - static signage, also called "static carpet projection," in which a fixed, i.e., static, image (Im) is projected.
[0053] As illustrated on the figure, the light device 1 comprises: - a matrix 10 of light sources 100, - a collimation optic 11, - a matrix 12 of metal lenses 121, and - a folding optic 13.
[0054] The elements of the lighting device 1 are described in detail below.
[0055] The matrix 10 of 100 light sources is described in detail below. It is illustrated in Figures 2a and 2b. It is also called the first matrix 11.
[0056] As illustrated in these figures, the matrix 10 of light sources 100 is configured to emit light R. The matrix 10 comprises at least one light source 100. In the non-limiting example shown in Figure 1, it comprises a single light source 100. In a non-limiting embodiment, the matrix 10 comprises a plurality of light sources 100. In a non-limiting variant of the embodiment shown in Figure 1, the matrix 10 comprises three light sources 100 to obtain white light R. In the case of multiple light sources 100, the light sources 100 emit light R with the same wavelength λ or with different wavelengths λ.
[0057] The emitted light R forms an incoming light beam Fx, also called a light beam Fx or simply beam Fx.
[0058] At least one light source 100 is a monochromatic light source. The light R emitted from such a light source 100 consists only of light rays of a single wavelength λ, also called wavelength λ; that is, it consists only of light rays having a specific color. Because the light source 10 is monochromatic, the light beam Fx is monochromatic.
[0059] In a non-limiting embodiment, the light source 100 emits monochromatic orange light with a wavelength λ between 590 nm (nanometers) and 610 nm. Note that a wavelength λ of 590 nm corresponds to amber-colored light.
[0060] In other non-limiting embodiments, the light source 10 emits monochromatic light of the following colors: - red with a wavelength λ between 620 nm and 700 nm. - cyan with a wavelength λ between 490 nm and 500 nm, - blue with a wavelength λ between 450 nm and 490 nm, - green with a wavelength between 490 nm and 570 nm, - yellow with a wavelength between 570 nm and 590 nm, - magenta with a wavelength between 400 nm and 410 nm.
[0061] These different colors make it possible to obtain the color white by mixing the colors blue, red and green, or even cyan, magenta, and yellow when the matrix 10 includes at least three light sources 100.
[0062] In a non-limiting embodiment, said at least one light source 100 is a light-emitting diode or a laser diode.
[0063] In one non-limiting embodiment, the light source 100 is a semiconductor light source. In other non-limiting embodiments, the semiconductor light source is a light-emitting diode (LED) or a laser diode. The term "light-emitting diode" includes any type of LED, including, but not limited to, LEDs (Light Emitting Diodes), OLEDs (Organic LEDs), AMOLEDs (Active-Matrix Organic LEDs), and FOLEDs (Flexible OLEDs). In another non-limiting embodiment, the light source 10 is a laser light source. Note that some laser light sources are not semiconductor light sources.
[0064] In a non-limiting embodiment, when the matrix 10 comprises a plurality of light sources 100, the light sources 100 can be activated independently of one another. Thus, to produce static light signage, in a non-limiting embodiment, the light sources 100 corresponding to each meta-lens 121 (described later) can be switched on (activated) or switched off (deactivated) simultaneously. Conversely, to produce dynamic light signage, in a non-limiting embodiment, the light sources 100 corresponding to each meta-lens 121 can be switched on (activated) or switched off (deactivated) sequentially to form an animated image.
[0065] In a preferred embodiment not shown, the collimating optics is a meta-lens or a matrix of meta-lenses configured to collimate light (R) at a wavelength (λ), and whose diameter is adapted to that of the light beam.
[0066] Each collimating meta-lens is manufactured with the same material and structures as the 12-metal-lens array. The difference lies in the distribution of the nano-pillars. This distribution depends on the type of source, LASER or LED. For a LASER source: the distribution of nano-pillar diameters follows phase polynomials in X and Y, due to the different divergences along the parallel and perpendicular beam directions. For an LED source, the distribution of nano-pillar diameters follows a rotationally symmetrical phase profile.
[0067] The collimation optic 11 is now described in detail below. It is illustrated in figures 1 and 3a to 3c.
[0068] As illustrated in the figure, the collimation optic 11 is positioned opposite the matrix 10 of light sources 100 and upstream of the matrix 12 of metal lenses 121. It is thus positioned between the matrix 10 of light sources 100 and the matrix 12 of metal lenses 121.
[0069] The collimating optics 11 are configured to collimate the light R emitted by the array 10 of light sources 100, thus forming a first collimated light beam Fx'. Indeed, the incident light Fx arriving at the collimating optics 11 is not collimated, but divergent. Collimating the incident beam Fx allows for the generation of a first collimated light beam Fx' with a phase profile adapted to the array 12 of metal lenses 121.
[0070] In a first non-limiting embodiment illustrated in the figure, the collimating optics 11 includes at least one lens 110. Said at least one lens 110 is designed to perform the collimating function of the light R. It is thus designed to collimate this light R so as to create several collimated light subbeams f (otherwise called collimated subbeams f) illustrated in the figure and forming the first collimated light beam Fx'.
[0071] The size of at least one lens 110 is greater than 1 mm. In a non-limiting embodiment, the collimation optics 11 comprise a lens 110 with a size on the order of several millimeters. In another non-limiting embodiment, the collimation optics 11 comprise two lenses 110. In this non-limiting embodiment, the thickness of the collimation optics 11 is thus between 2 mm and 3 mm.
[0072] In a second, non-limiting embodiment illustrated in Figure 3c, the collimation optics 11 is a matrix comprising a plurality of groups p of microlenses 111, otherwise called the second matrix 11, or simply matrix 11. In this case, the collimation optics is a matrix known by the acronym MLA for "Matrix Lens Array." A microlens 111 is sub-millimeter in size (from 1 mm and below). In a non-limiting example, the matrix 11 comprises several dozen microlenses 11. This allows for a thin luminous device 1.
[0073] In a non-limiting embodiment, two adjacent microlenses 111 from two different adjacent groups p are spaced by a first step ps equal to the size of a microlens 111. In a non-limiting embodiment, the first step ps is between 50 microns and 1 mm. In this non-limiting embodiment, the second array 11 thus has a thickness between 2 mm and 3 mm. The microlens array 111 is therefore very thin. This allows for a thin luminous device 1.
[0074] Each group p of microlenses 111 is configured to receive the light R emitted by the first array 10 of light sources 100. In the case of a plurality of light sources 100, in a non-limiting embodiment, a light source 100 is associated with one or more groups p of microlenses 111. In a non-limiting variant of the embodiment, a light source 100 is associated with only one group p of microlenses 111.
[0075] A group p is thus configured to collimate this light R in such a way as to create a collimated light subbeam f (also called a collimated subbeam f) illustrated in the figure. Each collimated subbeam f thus constitutes a substantially plane wave with respect to the associated metal lens 121 (described later). Thus, the first collimated light beam Fx' is formed by the set of collimated subbeams f.
[0076] In a non-limiting embodiment, the microlenses 111 are arranged in rows and columns to form a matrix 11. In a first non-limiting embodiment variant, a common core of an injected part allows for a single transparent substrate to be used to fabricate all the microlenses 111. In a second non-limiting embodiment variant, the microlenses 111 are bonded together to form the second matrix 11.
[0077] In a first non-limiting embodiment variant illustrated on the, each group p is formed of a single micro-lens 111. The MLA matrix is thus a so-called simple matrix.
[0078] In a second, non-limiting embodiment illustrated in Figure 1, a group p of microlenses 111 is formed from two microlenses 111. Thus, a group p forms a pair (or couple) of microlenses 111. The MLA matrix is therefore a so-called double matrix. A pair p (or couple p) comprises an input microlens 111 and an output microlens 111. In a non-limiting embodiment, each microlens 111 of the pair p has a side length between 0.5 and 2 mm, and therefore a surface area between 0.25 mm² and 4 mm². In a non-limiting embodiment, the pair p has a side length of 1 mm². 2 of surface. Thus, in a non-limiting embodiment, a micro-lens 111 has a side between 0.5 and 2mm.
[0079] The 12-metallens matrix 121 is now described in detail below. It is illustrated in Figures 1 and 4 to 7. It is also called the third matrix 12 or simply matrix 12.
[0080] The matrix 12 of meta-lenses 121 comprises a plurality of meta-lenses 121 and is disposed between the collimation optic 11 and the folding optic 13. It is thus disposed downstream of the collimation optic 11 opposite it, and upstream of the folding optic 13 opposite it as well.
[0081] Each meta-lens 121 receives one or more light sub-beams f of the same wavelength λ and thus each meta-lens 121 is adapted to this given wavelength λ.
[0082] In a non-limiting embodiment, the array 12 of metal lenses 121 has a thickness between 1 mm and 2 mm. The array 12 is thus very thin. It should be noted that the size of the array 12 (width-height) corresponds to the size of the collimation optics 11 when the latter comprises microlenses 111. This avoids light loss.
[0083] Each meta-lens 121 is configured to orient a portion of the first collimated light beam Fx' along a propagation direction P (illustrated in Figure 1) so as to form a portion of the image Im and project it onto a plane PL (illustrated in Figure 2) parallel to the matrix 12 of meta-lenses 121. This results in a second collimated light beam Fx'', illustrated in Figure 1, which forms the image Im. Thus, an image Im is formed from each collimated sub-beam(s) f oriented by each meta-lens 121. It is composed of one or more patterns. In the non-limiting example in Figure 1, the image Im is composed of three geometric patterns.
[0084] In a non-limiting embodiment, the meta-lenses 121 are arranged in rows and columns to form the matrix 12. In a first non-limiting embodiment, the meta-lenses 111 are arranged on a common substrate, namely, there is a common substrate with different sets of nano-pillars 121.2 (described later). In a second non-limiting embodiment, the meta-lenses 121 are bonded to an additional common transparent substrate, namely, each set of nano-pillars 121.2 and their substrate 121.1 (described later) is bonded to the additional transparent substrate.
[0085] In the case where the collimating optic 11 is a matrix 11 of micro-lenses 111, each meta-lens 121 of the third matrix 12 is arranged opposite each group p of micro-lenses 111 of the second matrix 11 and is configured to: - orient the collimated sub-beam f of said group p along a propagation direction P so as to form a part of the image Im to be projected.
[0086] In a first, non-limiting embodiment, a meta-lens 121 is configured to produce an image Im composed of all or part of a monochrome pattern. Thus, to produce static monochrome illuminated signage, in a non-limiting example, a single meta-lens 121 forms the pattern of the image Im for said static illuminated signage if the corresponding light source 100 is sufficiently powerful to obtain the desired brightness.
[0087] In a second, non-limiting embodiment, a plurality of metal lenses 121 are configured to produce an image Im composed of one or more monochrome, white, or polychrome patterns. Thus, to produce static monochrome, white, or polychrome illuminated signage, in a non-limiting example, several metal lenses 121 can produce the same pattern of the image Im for said static illuminated signage, the patterns overlapping each other.
[0088] In a third, non-limiting embodiment, a plurality of meta-lenses 121 is configured to produce a dynamic monochrome image composed of several patterns.
[0089] In a fourth, non-limiting embodiment, a plurality of meta-lenses 121 is configured to produce a dynamic polychrome or white image composed of several patterns.
[0090] In this third and fourth non-limiting embodiment, each meta-lens 121 forms a pattern that can be superimposed on other patterns formed by other meta-lenses 121 and replace one another to create an animated image. Thus, in a non-limiting example, to produce dynamic illuminated signage, several meta-lenses 121 can respectively produce several images Im of the animated image for said dynamic illuminated signage. Since the light sources 100 corresponding to each meta-lens 121 can be of different colors, a pattern of different colors, or of white, can thus be obtained.
[0091] In a non-limiting embodiment, a metal lens 121 has a surface area less than or equal to 1 mm² 2If the surface area is larger, it requires excessive computing power to define the optimal distribution of the nano-pillars 121.2 of the metal lens 121. Thus, thanks to these small dimensions, a better manufacturing yield is achieved, resulting in a less expensive lighting device 1. Indeed, since the scrap rate depends on the surface area, smaller metal lenses 121 produce less waste.
[0092] Furthermore, in a non-limiting embodiment, when the collimating optics 11 comprise a plurality of groups p of microlenses 111, a meta-lens 121 of the matrix 12 is associated with a group p of microlenses 111. Thus, there are as many meta-lenses 121 as there are groups p of microlenses 111. Moreover, in this case, in a non-limiting embodiment, the meta-lenses 121 have a size equal to the first step ps defined between two adjacent microlenses 111 of two different adjacent groups p. This allows the surface of the corresponding collimated light subbeam f to be intercepted.
[0093] In other non-limiting embodiments, we may have several meta-lenses 121 associated with a group p of micro-lenses 111 or conversely several groups p of micro-lenses 111 associated with a single meta-lens 121.
[0094] Each meta-lens 121 is configured to receive a collimated light sub-beam f and modify its propagation phase φ so that it is oriented in a given propagation direction P (illustrated in the figure). In the remainder of the description, the propagation phase φ is otherwise referred to as phase φ.
[0095] As illustrated in the figure, a meta-lens 121 comprises: - a substrate 121.1, and - a plurality of nano-pillars 121.2.
[0096] The substrate 121.1 has a thickness E and a length L. In a non-limiting embodiment, the substrate 121.1 is made of glass.
[0097] The substrate 121.1 has a first refractive index n1 (also more simply called the refractive index n1), and the nanopillars 121.2 have a second refractive index n2 (also more simply called the refractive index n2). The first refractive index n1 of the substrate 121.1 is lower than the second refractive index n2 of the nanopillars 121.2. The first refractive index n1 is kept as low as possible to avoid light loss at the entrance to the substrate 121.1 due to partial glass reflections. Each metal lens 121 has a light refractive index n2 for the nanopillars 121.2. The second refractive index n2 is kept as high as possible to ensure the luminous efficiency of the metal lens 121.
[0098] In a non-limiting embodiment, the second refractive index n2 is greater than 2. This allows for optimum light transmission with light arriving perpendicularly on the matrix 12 of metal lenses.
[0099] Thus, in non-limiting examples, from certain materials of the 121.2 nano-pillars, we can have the following values: - n2 = 2.1 for λ = 631nm (red), - n2 = 2.47 for λ = 450nm (blue), - n2 = 2.38 for λ = 550nm (green), - n2 = 2.35 for λ = 621nm (red) and 632nm (super red), - n2 = 2.37 for λ = 580nm (yellow).
[0100] In a non-limiting embodiment, all the meta-lenses 121 of the matrix 12 have the same refractive index n2, or different refractive indices n2.
[0101] In the case of a first matrix 10 comprising a plurality of light sources 100, in a first non-limiting embodiment, all the light sources 100 emit light R over the same wavelength range λ. In a second non-limiting embodiment, the light sources 100 each emit light R over different wavelength ranges λ. In a third non-limiting embodiment, some light sources 100 emit light R over the same wavelength range λ, and other light sources 100 emit light R over different wavelength ranges λ.
[0102] Since the 100 light sources can be activated independently, using different wavelengths λ allows for the creation of an overall light beam Fx''' (also simply called the light beam Fx''') of different colors depending on the activation, or white. The overall light beam Fx''' is illustrated in Figure 1 and is the emerging beam at the output of the light device 1.
[0103] The nano-pillars 121.2 are arranged on the substrate 121.1. They are defined by parameters including: - a radius r (illustrated in figures 5 and 6), - a height h (illustrated in figures 5 and 6), - a second step ps' between two nano-pillars 121.2. The second step ps' (illustrated in the) represents the repetition frequency of the nano-pillars 121.2, - a material with the second refractive index n2 (illustrated in the) which is the refractive index of the metal-lens 121, - a base bs (illustrated in the).
[0104] Note that the second step ps' is defined between the two longitudinal axes (illustrated with dashed lines in Figure 1) of two adjacent nano-pillars 121.2. In a non-limiting embodiment illustrated in Figure 1, the nano-pillars 121.2 have a disk-shaped base bs.
[0105] In a non-limiting embodiment, the 121.2 nanopillars are made of Silicon Nitride (SiN). This material is easy to work with and produces less dust compared to other materials that can be used for 121.2 nanopillars, such as, but not limited to, Titanium Dioxide (TiO2), Hafnium Oxide (HfO2), or Gallium Nitride (GaN). For SiN, n2 = 2.0454, for TiO2, n2 = 2.6142, and for GaN, n2 = 2.3982 at a wavelength λ of 590 nm.
[0106] In a non-limiting embodiment example, on a substrate 121.1 of thickness E=5 millimeters, a 70 nanometer layer of SiN can be deposited and the SiN layer etched to obtain the nano-pillars 121.2.
[0107] The nano-pillars 121.2 of each meta-lens 121 modify the propagation phase φ of a collimated sub-beam f passing through them. In other words, they add a phase delay. The result is that the collimated sub-beam f is deflected, giving it a desired propagation direction P (illustrated in the figure) so as to obtain a portion of the second collimated light beam Fx'. The set of collimated sub-beams f thus deflected forms the second collimated light beam Fx'', also called the resulting light beam Fx''.
[0108] To adjust the propagation direction P, the phase shift within a collimated light subbeam f is spatially controlled, which amounts to controlling the phase change gradient φ of the collimated light subbeams f. This is done using nano-pillars 121.2.
[0109] To this end, in a non-limiting embodiment illustrated in Figure 1, the 121.2 nanopillars have different radii r and the same height h. For the sake of clarity, only one height ha and one radius ra are referenced. It should be noted that the smaller the radius r, the less material a 121.2 nanopillar contains, which results in a minimal change in the phase φ, leading to a small phase delay. Conversely, when the radius r is larger, the more material a 121.2 nanopillar contains, resulting in a more significant change in the phase φ, leading to a larger phase delay.
[0110] As illustrated in Figure 1, the 111.2 nano-pillars have a radius r that increases from left to right. Each 121.2 nano-pillar will induce a different phase delay φ compared to its neighbor. The larger the radius r, the greater the phase delay φ. The radius r thus affects the phase φ of the collimated light sub-beam f. Since the r radii are 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. Note that the greater the delay, the more the wavefront is distorted and the more the resulting light beam Fx'' is deflected.
[0111] As a reminder, light propagates perpendicularly to the wavefront. Typically, there is zero phase delay along the same line of the wavefront. As can be seen in the figure, the incoming wavefront Fo at the entrance of the meta-lens 121 (also called the incident wavefront Fo) is plane and perpendicular to the substrate 121.1 of the meta-lens 121.
[0112] Each nano-pillar 121.2 introduces a phase delay φ different from its neighbor, because they all have a different diameter, this differential phase delay then causes a deformation of the wavefront.
[0113] As can be seen on the figure, the emerging wavefront Fo' is distorted, which therefore causes a deviation of the emerging light beam Fx'', which is the resulting deflected light beam.
[0114] Thus, upon exiting a metal lens 111, the light, which always propagates perpendicularly to the wavefront (here, the emerging wavefront Fo', which is inclined), will be oriented along a given propagation direction P. Consequently, the light is oriented along a propagation direction P that has changed due to the phase shift of the light.
[0115] Note that the emerging wavefront Fo' has been delayed progressively and linearly. Each nano-pillar 121.2 is configured to induce a linearly evolving phase shift φ of the light, i.e., a linear phase shift. This results in a planar emerging wavefront Fo'. A phase shift between 0 and 2π is equivalent. Therefore, it is not necessary to create a linear phase shift along the entire length of the input wavefront Fo to obtain a continuous deflection. A phase shift between 0 and 2π can be performed as many times as needed. Thus, a linear phase shift between 0 and 10π is equivalent to five linear phase shifts between 0 and 2π.
[0116] 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 perspective of the 121 meta-lens, as soon as φ = 2π, we return to a radius r of a 121.2 nano-pillar corresponding to 0, and therefore to the same 121.2 nano-pillar to avoid excessively large differences between the radii r. Thus, the 121 meta-lens comprises several sets of 121.2 nano-pillars defined in such a way as to obtain a phase shift of the light with a phase modulated between 0 and 2π.
[0117] The height h of the 121.2 nano-pillars allows control of the phase φ between 0 and 2π for a given wavelength λ. With the correct height h defined, all phase changes between 0 and 2π can be performed.
[0118] As explained previously, the radius r allows control of the phase φ of the light beam Fx.
[0119] The other parameters, namely the height h, the second step ps', and the material of the 121.2 nano-pillars, are defined to maximize the light transmission rate through the 121.2 nano-pillars. Maximizing the transmission rate means minimizing the absorption of light by the material of the 121.2 nano-pillar. Thus, these other parameters are determined to obtain minimum absorption over the range where the radius r is varied to obtain a phase shift (also called phase difference) between 0 and 2π.
[0120] By calculation, for a 111.2 nanopillar, a given height h and a given pitch ps are fixed, along with its material, which is, for example, Silicon Nitride (SiN) with a refractive index n2 = 2.0454. In the illustrated example (not limiting), h = 1.35 μm and ps = 0.450 μm. Working with a constant height h facilitates the fabrication of 111.2 nanopillars. With a constant height h, the design of the 111.2 nanopillars must be adapted to achieve a phase shift between 0 and 2π while simultaneously maximizing light transmission to retain as much light as possible.
[0121] For a fixed height h and a fixed step size ps, we establish the light transmission curves as a function of the radius r, and the phase shift curves as a function of the radius r. Curves 8 and 9 illustrate the phase shift and light transmission for the best compromise for the chosen constant height h and for a given wavelength λ. Note that this compromise changes if the wavelength λ changes.
[0122] 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 ordinates) between 0 and 9 as a function of the radius r (on the abscissas) of the nano-pillars 111.2 which varies between 0.04 and 0.15 μm, for a given wavelength λ, here for λ=590nm in the illustrated non-limiting example.
[0123] In a non-limiting example, for a height h = 1.35 µm, we can observe a variation in light transmission Tx (on the y-axis) between 0 and 1 as a function of the radius r (on the x-axis) of the 111.2 nanopillars, which varies between 0.04 and 0.15 μm, for the given wavelength λ, here 590 nm. At a value of 0, no light passes through. At a value of 1, all light passes through.
[0124] Using these two curves, we can determine the height h and radius r of the 121.2 nanopillars that provide dynamic phase shift control while maximizing light transmission through the nanopillars, all while maintaining manufacturability. We can thus find the values of all the parameters of a 121.2 nanopillar to obtain the possible phase shift (or phase difference) and transmission values, and in particular a transmission rate close to 1 for a given wavelength λ. Note that if the results are not satisfactory, the procedure can be repeated by setting a different value for the height h.
[0125] The set of collimated sub-beams f thus deviated form a sharp projected image Im at approximately a certain distance d on the plane PL (illustrated in the figure) parallel to the substrate of the metal lenses 121 as illustrated in the figure. In a non-limiting embodiment, the distance d is between 30 cm and 2 m.
[0126] It should be noted that the distance d depends on the phase shift introduced by the nano-pillars 121.2. Thus, the light R is redirected towards the areas to be illuminated. The other areas are not illuminated and appear dark. The deflected collimated sub-beams f are transmitted with a very high light transmission rate, between 80% and 90%. There is therefore very little light loss. The remaining 20% to 10% of the light is lost because it is reflected by the substrate of the nano-pillars 121.2 of the metal-lenses 121.
[0127] As illustrated in Figure 1, the image Im comprises illuminated areas z1 towards which the light has been redirected, and shaded areas z2 (within the illuminated areas z1 in the non-limiting example shown and between the illuminated areas z1) towards which the light has not been redirected. The illuminated areas z1 are areas of light concentration.
[0128] Note that the black frame surrounding the illuminated areas z1 is only present to highlight the illuminated areas z1 on the.
[0129] To obtain the illuminated areas z1, for a fixed height h and a fixed second step ps', we play on the radius r of the nano-pillars 121.2 to obtain a maximum of light transmission and we redirect the light beams F towards the areas to be illuminated as described previously.
[0130] The matrix 12 of meta-lenses 121 is arranged at approximately 10 èmemillimeters of collimation optics 11. This allows for an ultra-thin luminous device 1.
[0131] Thus, while the metal lenses 121 allow the projection of the image Im, the folding optics 13 allow the folding of the image Im onto the ground 4.
[0132] The folding optic 13 is now described in detail below. It is illustrated in figures 1, 12 and 13.
[0133] The folding optic 13 is positioned opposite the metal-lens matrix 121, downstream of it. It is positioned approximately 10 ème millimeters of the matrix 12 of 121 metal lenses. This allows for an ultra-thin 1-light device.
[0134] The folding optic 13 is adapted to the monochromatic light R emitted by the light source 10. It directs the second collimated light beam Fx'' along a particular direction, called the orientation direction O'.
[0135] As illustrated in Figure 1, the folding optic 13 is configured to deflect the second collimated light beam Fx'' along an orientation direction O' so as to project the image Im formed by this second collimated light beam Fx'' onto the ground 4. The light beam emerging from the folding optic 13 is the overall light beam Fx'''. In Figure 4, one can observe the image Im shown as a non-limiting example of the image that has been projected onto the ground 4.
[0136] In a first non-limiting embodiment illustrated on the, the folding optic 13 is a diffraction grating referenced 13.
[0137] The diffraction grating 13 comprises a plurality of patterns 130 distributed according to a periodicity T = λ / n*sinθ, where λ is the wavelength of the light R emitted by at least one light source 100, n is the refractive index of the light in the medium of the diffractive grating 13, and θ is an orientation angle. In this case, with a plurality of light sources 100, they emit light with the same wavelength λ.
[0138] In a non-limiting embodiment, the orientation angle θ is between 30° and 60°. In a non-limiting variant, when the light device 1 is positioned at the level of a rearview mirror 20 of the vehicle 2, the orientation angle θ is approximately 60°. Thus, the projected image Im is projected downwards. In another non-limiting variant, when the light device 1 is positioned at the bottom of a door 21, the orientation angle is between 30° and 45°. Thus, the projected image Im is projected at an angle so that the image on the ground 4 is in front of the opening left by the open door 21 and not under the door 21 of the vehicle 2.
[0139] In a non-limiting embodiment, the motifs 130 have a height h' close to said wavelength λ. In a non-limiting embodiment, the height h' is approximately equal to 500 nm. In a non-limiting variant of the embodiment, the height h' is equal to 556 nm for a wavelength λ of 590 nm, for a refractive index of light n = 1.5 and for an orientation angle θ = 45°.
[0140] Thus, the diffraction grating 13 behaves like a prism which is a function of: - the monochromatic light R, - the refractive index of light n of the material of the diffraction grating 13, - the calculation of periodicity of the patterns 130.
[0141] In non-limiting embodiments, the material is glass, PMMA, or PC.
[0142] In a non-limiting embodiment, said diffraction grating 13 has a thickness of approximately 2 mm. Thus, the advantage of the diffraction grating 13 is that it is thin and therefore less bulky than a conventional projection lens.
[0143] In a second, non-limiting embodiment illustrated in Figure 1, the folding optic 13 is a Fresnel lens. In this non-limiting embodiment, the Fresnel lens has a thickness between 1 mm and 3 mm. In this case, with a plurality of light sources 100, these sources emit light with the same wavelength λ or with different wavelengths λ.
[0144] Thus, due to the very thin thickness of the various elements of the lighting device 1 and their close proximity to one another, a very thin lighting device 1 is obtained. Indeed, the collimation optics 11 (lenses or MLA), the matrix 12 of meta-lenses 120, and the refracting optics 13 (diffraction grating or MLA) together have a thickness E approximately equal to 6 mm. And by adding the light source 10, the assembly has a thickness E' less than or equal to 15 mm.
[0145] Of course, the description of the invention is not limited to the embodiments and the scope described above. Thus, in other, non-limiting embodiments, the base bs of the nano-pillars 111.2 is oblong or elliptical in shape. Thus, in another, non-limiting embodiment, the nano-pillars 111.2 have the same radius r but different heights h.
[0146] Thus, the described invention offers the following advantages: - by replacing a mask / slide with conventional projection optics (focused lens comprising several lenses) with a matrix 12 of metal lenses 121, it makes it possible to obtain a very compact lighting device 1, particularly in depth compared to the prior art, which has a depth of approximately 3 to 4 cm; - by replacing a conventional collimator with collimation optics that are an MLA, the depth of the lighting device 1 is further reduced; - it allows for a lighting device 1 that is easily integrated into a vehicle: the lighting device 1 can be positioned in unusual locations within the vehicle 2.- It allows for a miniaturized lighting device 1 which significantly contributes to reducing the weight of the vehicle 2 in which it is integrated and can also enable a more aerodynamic vehicle design to lower its energy consumption and CO2 emissions; - It allows for the creation of an image Im with complex lighting patterns that can be individually controlled by light; - It allows an external observer to see no difference when the lighting device 1 is on or off, meaning that neither the style nor the appearance of the vehicle is altered by the activation of the lighting device 1. Indeed, the lighting device 1 is small and flat; - Thus, thanks to the lighting device 1 according to the invention, it is no longer necessary to use optical masks to create patterns to be projected onto the ground, for example.- It allows for very good luminous efficiency since it uses all, or at least almost all, of the light R emitted by the matrix 10 of light sources 100 for the projection of an image Im, unlike the prior art; this results in between 80% and 90% light transmission for a wavelength λ of 590nm. - It allows for a luminous device 1 that heats up less since it does not block the light: there is no light absorption as in the case of the prior art: an image Im is thus created without loss of light. Thus, the luminous device 1 requires less energy than that of the prior art. - It allows for easy obtaining of a white or colored image. - It allows for better luminous efficiency than a luminous device comprising a light source and a conventional collimator.an MLA with a mask (which would replace the slide and the classic projection optics) forming the patterns of the image Im to be projected, since there is no mask and therefore no light loss in a mask.
Claims
Light device (1) for vehicle (2) configured to project an image (Im) onto the ground (4), said light device (1) comprising: - an array (10) of monochromatic light sources (100) configured to emit light (R) at a given wavelength (λ), said light (R) forming a light beam (Fx); characterized in that said light device (1) further comprises: - a collimation optic (11) disposed opposite said array (10) of light sources (100) and configured to collimate said light (R) and form a first collimated light beam (Fx') composed of a plurality of collimated light sub-beams (f), - an array (12) of metal lenses (121) comprising a plurality of metal lenses (121) and disposed opposite the collimation optic (11),each meta-lens (121) being configured to orient a collimated light sub-beam (f) along a propagation direction (P) to obtain a portion of a second collimated light beam (Fx'') forming said image (Im), said matrix (12) of meta-lenses (121) being configured to project said image (Im) onto a plane (PL) parallel to said matrix (12), and a refracting optic (13) disposed opposite the matrix (12) of meta-lenses (121) and configured to deflect the second collimated light beam (Fx'') along an orientation direction (O') so as to project said image (I) onto the ground (4). Light device (1) according to claim 1, characterized in that the collimation optics (11) comprises a meta-lens or a matrix of meta-lenses configured to collimate the light (R) at a given wavelength (λ), and whose diameter is adapted to that of the light beam. Light device (1) according to claim 1, characterized in that the collimating optics (11) comprises at least one lens (110) or is an array comprising a plurality of groups (p) of microlenses (111), each group (p) being configured to collimate said light (R) and create a collimated subbeam (f) forming a part of said first collimated light beam (Fx'). Light device (1) according to claim 2, characterized in that a group (p) of micro-lenses (111) is formed of a single micro-lens (111) or of two micro-lenses (111). Light device (1) according to claim 2 or claim 3, characterized in that each meta-lens (121) of the matrix (12) is arranged opposite each group (p) of micro-lenses (111) and is configured to orient the collimated sub-beam (f) of said group (p) along a propagation direction (P) so as to form a part of said image (I). Light device (1) according to any one of claims 2 to 4, characterized in that the meta-lenses (121) have a size equal to a first step (ps) defined between two adjacent micro-lenses (111) of two different adjacent groups (p). A lighting device (1) according to any one of the preceding claims, characterized in that said metal lenses (121) have a surface area less than or equal to 1 mm² 2 . Light device (1) according to any one of the preceding claims, characterized in that said collimation optic (11) has a thickness between 2mm and 3mm. Light device (1) according to any one of the preceding claims, characterized in that the metal lenses (121) comprise nano-pillars (121.2) defined by a radius (r), a height (h) and a second pitch (ps') between two nano-pillars (121.2). Light device (1) according to any one of the preceding claims, characterized in that the folding optics (13) is a diffraction grating or a microlens array (131). Light device (1) according to any one of the preceding claims, characterized in that the folding optic (13) has a thickness between 1mm and 3mm. Light device (1) according to claim 9 or claim 10, characterized in that the diffraction grating (13) comprises a plurality of patterns (130) distributed according to a periodicity T= λ / n*sinθ, with λ said wavelength of the light (R) emitted by the matrix (10) of light sources (100), n a refractive index of light of the diffractive grating (13), and θ an angle of orientation. Light device (1) according to the preceding claim, characterized in that the motifs (130) have a height (h') close to said wavelength (λ). Vehicle (2) comprising a lighting device (1) according to any one of the preceding claims, said lighting device (1) being disposed outside the vehicle (2).