Light device for projecting an image onto the ground

Abstract

Light device for projecting an image onto the ground. Light device (2) for a motor vehicle (1), the light device (2) being configured to project an image around the vehicle (1), the light device (2) being characterized in that it comprises: at least one light source (4) configured to produce a monochromatic light beam (F); at least one optical device (14) juxtaposed to the light source (4) such that the light beam (F) produced by the light source (4) passes through the optical device (14), said optical device (14) comprising at least one metal lens (15) configured to modify at least one optical property of the wavefront of the light beam (F). Figure for the abstract: Fig. 2

Description

Title of the invention: Luminous device for projecting an image on the ground

[0001] The present invention relates to a lighting device for a motor vehicle, the lighting device being configured to project an image comprising a pattern on the ground around the vehicle. The invention also relates to a motor vehicle equipped with such a lighting device.

[0002] Certain motor vehicles are equipped with a lighting device configured to project an image onto the ground around the vehicle, for example at the front of the vehicle or on the sides of the vehicle, in particular at the doors to provide information facilitating or guiding the exit of a passenger from said vehicle, in particular when the ambient light is relatively low. These images may include patterns such as arrows, lines or pictograms. Such lighting devices may also aim to display information useful to other road users. These lighting devices thus make it possible to communicate the intentions of the driver of the motor vehicle to other road users and in particular to pedestrians. Publication EP3401161A2 discloses such a lighting device.

[0003] There are also digital dynamic projection systems such as micro-mirror matrices (called “DMD” in English for “digital micromirror device”), microelectromechanical systems (called “MEMS” in English for “microelectromechanical Systems”), microLEDs, liquid crystal screens or even LCOS video projectors.

[0004] The light devices known from the state of the art are generally complex to manufacture and use. In addition, these light devices are generally heavy and bulky, which complicates their integration within a motor vehicle. Furthermore, these light devices often use a mask to form an image on the ground around the vehicle, but such a mask limits the transmitted light power, which results in limited light intensity.

[0005] Furthermore, certain lighting devices known from the state of the art comprise relatively fragile components which may be damaged, fail or even break if they are exposed to these shocks or if the motor vehicle is used in a rough environment (damaged, dusty, dirty road or other). The vibrations generated then prove very problematic because they bring significant limitations when projecting images.

[0006] In addition, these lighting devices are bulky. Their discreet integration into a vehicle, without altering its aesthetic appearance, is therefore difficult to achieve. Presentation of the invention

[0007] The aim of the invention is to provide a lighting device which overcomes the above drawbacks and improves the lighting devices known from the prior art.

[0008] Thus, a first object of the invention is a light device which is simple to manufacture and capable of projecting reliably and with high luminous efficiency at least one image comprising a pattern.

[0009] A second object of the invention is a more compact, more robust and lighter lighting device, easily integrated into a motor vehicle.

[0010] A third object of the invention is a light device which is not affected by possible shocks and / or vibrations generated by the use of the motor vehicle in which said light device is integrated. Summary of the invention

[0011] The invention relates to a light device for a motor vehicle, the light device being configured to project an image around the vehicle, the light device being characterized in that it comprises at least one light source configured to produce a monochromatic light beam and at least one optical device juxtaposed with the light source so that the light beam produced by the light source passes through the optical device, said optical device comprising at least one meta-lens configured to modify at least one property of the wavefront of the light beam.

[0012] According to a particular embodiment, the meta-lens of the optical device comprises at least one nanostructure configured to modify the amplitude and / or the phase of the light beam produced by the light source and passing through the optical device.

[0013] According to a particular embodiment, the nanostructure comprises a transparent substrate with an arrangement of nanopillars on the surface and the nanopillars all have the same height.

[0014] According to a particular embodiment, the nanopillars have sections of different sizes from each other.

[0015] According to a particular embodiment, the nanopillars have a cylindrical shape and they comprise a circular base.

[0016] According to a particular embodiment, the diameter of the nanopillars is between 50 nm and 150 nm.

[0017] According to a particular embodiment, the light device comprises a multitude of light sources and a multitude of meta-lenses, and each monochromatic light source is associated with a meta-lens which is specific to it.

[0018] According to a particular embodiment, the multitude of meta-lenses is arranged in rows and columns on the optical device so as to form a matrix, and the multitude of light sources is also arranged in rows and columns so as to form a matrix such that each light beam produced by one of the monochromatic light sources passes through the meta-lens with which said light source is associated.

[0019] According to a particular embodiment, the optical device further comprises at least one liquid crystal layer extending against the at least one meta-lens and a voltage source configured to apply an electric field to the liquid crystal layer to form at least one variable focal length lens thanks to the phase change of the liquid crystals.

[0020] According to a particular embodiment, the optical device comprises a projection lens configured to shape the light beam and to direct said light beam towards the ground.

[0021] The invention also relates to a motor vehicle equipped with such a lighting device. Presentation of figures

[0022] 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:

[0023] [Fig.l] is a schematic view of a motor vehicle equipped with a lighting device according to the state of the art.

[0024] [Fig. 2] is a schematic view of a motor vehicle equipped with a lighting device according to one embodiment of the invention.

[0025] [Fig. 3] is a schematic view of an optical device according to a preferred embodiment of the invention.

[0026] [Fig.4] is a schematic perspective view of a detail of a nanostructure of a meta-lens.

[0027] [Fig.5] is a schematic perspective view of a meta-lens associated with a variable focal length lens.

[0028] [Fig. 6] is a schematic view of a motor vehicle equipped with a lighting device according to one embodiment of the invention. Detailed description

[0029] An embodiment of a motor vehicle 1' according to the state of the art is described below with reference to [Fig.l].

[0030] The vehicle 1' illustrated schematically in [Fig.l] comprises a lighting device 2' according to an embodiment known from the state of the art. The lighting device 2' is configured to project an image onto the ground 3', at the front of the vehicle 1. It is specified that the front designates the side of the vehicle 1' towards which it is heading in a straight line, in forward motion.

[0031] In this embodiment known from the state of the art, the light device 2' comprises at least one light source 4', capable of producing a light beam F', and a mask 5' positioned on the path of the light beam F'. The at least one light source 4' is a monochromatic light source. The light from such a light source 4' only comprises rays of a single wavelength; that is to say, it only comprises light rays having a specific color.

[0032] The surface of the mask 5' comprises opaque zones 8' and transparent zones 9', these transparent zones 9' generally have a shape suitable for the projection of an image comprising a pattern. The mask 5' therefore makes it possible to modify the light beam F' coming from the light source 4' so as to project an image comprising a pattern onto the ground 3' in front of a vehicle 1'. An optical element 11', such as a projection lens, may be provided downstream of the mask 5', in order to shape and direct the light beam F' towards the ground 3'. In this way, the light rays incident at the transparent zone 9' of the mask 5 pass through the mask 5' and are then guided towards the ground 3' by the optical element 11'.

[0033] This embodiment known from the state of the art has several drawbacks. In particular, the transparent zone(s) are generally positioned at the edge of the mask 5', leaving a central zone of the mask 5' unused, except for the part of the mask 5' mechanically connected to an actuation means 12' which makes it possible to rotate the mask around an axis of rotation. It is therefore necessary to find a compromise between the number of transparent zones 9' suitable for the projection of an image and the size of said transparent zones 9'.

[0034] Furthermore, the actuating means 12' and / or its mechanical connection with the mask 5' may be subject to shocks or vibrations during use of the motor vehicle 1', which may cause a disturbance in the position of the mask 5'. Such a disturbance of the mask 5' may result in a faulty projection of the images onto the ground 3', which may inconvenience the driver of the vehicle 1'.

[0035] Furthermore, the order of projection of the images onto the ground 3' depends on the arrangement of the transparent areas 9' on the mask 5'. More particularly, only images adjacent to each other on the mask 5' can be projected consecutively onto the ground. In other words, arranging transparent areas 9' with patterns and / or contours on the edge of the mask 5' greatly limits the options for the order of projection of said images onto the ground 3'.

[0036] An embodiment of a motor vehicle 1 according to the invention is described below with reference to [Fig. 2]. Throughout the description, the vehicle The vehicle can be of any type, including a passenger vehicle, a utility vehicle, a truck or even a bus. This embodiment aims to provide a solution to the problems identified with the known embodiment of the prior art by remedying the drawbacks described above and by proposing an improved lighting device 2.

[0037] According to one embodiment of the invention, a light device 2 according to the invention comprises at least one light source 4, for example a light-emitting diode or a set of light-emitting diodes, capable of producing a monochromatic light beam F. The light source 4 can be connected to a printed circuit board 6. The printed circuit board 6 can be held by a support 7 possibly comprising a heat sink.

[0038] The at least one light source 4 is configured to produce a monochromatic light beam F. As explained previously, a monochrome light only comprises rays of a single color, that is to say that it only comprises light rays having a specific wavelength or a wavelength included in a precise interval.

[0039] Advantageously, the light source 4 may have sufficient power to project an image onto the ground 3 in front of the vehicle 1 that is visible even in broad daylight. It is specified that the front designates the side of the vehicle 1' towards which it is heading in a straight line, when moving forward. The image may for example be projected a few centimeters or a few tens of meters in front of the vehicle 1. The lighting device 2 may be, for example, arranged at the front of the vehicle 1, at the level of a grille and / or at the level of projectors intended to illuminate the road and make the vehicle 1 clearly visible to other road users.

[0040] The light device 2 also comprises at least one optical device 14 juxtaposed with the light source 4 so that the light beam F produced by the light source 4 passes through the optical device 14. In addition, the optical device 14 comprises at least one meta-lens 15 configured to modify at least one optical property of the wavefront of the light beam F produced by the light source 4.

[0041] Thus, the transmission rate through an 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. This gives a brighter image and / or it is possible to use a lower power light source and / or one that consumes less energy.

[0042] The at least one 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 particular embodiment, the at least one meta-lens 15 may have a square or rectangular shape. According to a preferred embodiment illustrated in [Fig. 3], the meta-lens(es) 15 may have a diamond shape. Such shapes, in particular the diamond shape as illustrated in [Fig. 3], may allow a compact matrix arrangement of several meta-lenses 15.

[0043] The meta-lens 15 of the optical device 14 generally comprises a nanostructure 16 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.

[0044] The nanostructure 16 of the meta-lens 15 may comprise an arrangement of nanopillars 17 on its surface. These nanopillars 17 are generally manufactured by nanostructuring, i.e. by electron beam lithography or by nanoimprint lithography in thin layers and arranged in the form of periodic networks. These nanopillars 17 are of nanometric size and may comprise dielectric materials with a high refractive index, for example a refractive index greater than two.

[0045] More particularly, the nanostructure 16 may comprise a periodic array of nanopillars 17. By “periodic” is meant here that the nanopillars within the nanostructure 16 are placed at more or less regular intervals from one another. For example, the nanopillars 17 of a nanostructure 16 may be placed at intervals of between 300 nm and 500 nm with a preference for an interval of 400 nm. In other words, in a preferred embodiment of a meta-lens 15, the centers of two neighboring nanopillars 17 are 400 nm apart.

[0046] The optical properties of a meta-lens 15 are mainly defined by the wavelength of the monochromatic light source 4 used, by the refractive index(es) of the materials used for the nanopillars 17, by the dimensions of the nanopillars 17 and by their distribution within the nanostructure 16. In other words, the density of material in the nanostructure 16 of the meta-lens 15 defines the effect that the meta-lens 15 has on the light beam F which passes through it.

[0047] The nanopillars 17 are for example placed on a transparent substrate. The material of the transparent substrate 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. Generally, the material of the substrate has a first refractive index n1 which is lower than a second refractive index n2 of the nanopillars 17.

[0048] Generally speaking, 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 can have an impact on the propagation speed of the light beam F which passes through said nanopillar 17, thus modifying the optical properties of the wavefront of said light beam F which passes through the optical device 14.

[0049] The nanopillars 17 may in particular have a cylindrical shape; in this case, they may comprise a circular-shaped base, as illustrated in [Fig. 4]. The diameter may vary from one nanopillar 17 to another. Alternatively, the shape of the base could be different from a circular shape, for example a polygonal base, in particular square or rectangular.

[0050] Furthermore, these nanopillars 17 can have the same height configured to modify the phase of the light beam F produced by the light source 4. For monochromatic light having a given wavelength, the ideal height of the nanopillars 17 can be determined to obtain the highest possible transmission rate.

[0051] 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 direction of propagation of the light beam. In other words, the distribution of the nanopillars 17 within the nanostructure 16 can be specifically configured to influence the direction of propagation of the light beam F in order to modify the orientation of the light beam at the exit of the meta-lens 15.

[0052] More generally, a meta-lens 15 comprises a quasi-periodic array of nanopillars 17 having different diameters so as to influence the speed of propagation of light through the nanopillars 17 so as to modify the 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 and different diameters, the nanopillar 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 orient the light beam F at the output of the light device 2 so as to distort the plane wave towards one or more sharp images with detailed contours on the ground 3 around the vehicle 100.

[0053] In one embodiment, the nanostructure 16 of the meta-lens 15 comprises on its surface an arrangement of nanopillars 17 all having the same specific height, this nanostructure 16 of the meta-lens 17 makes it possible to introduce a phase shift of the light beam F with a specific wavelength which passes through the optical device 14, thus modifying the phase of the wavefront of said light beam F. The height of the nanopillars 17 makes it possible to control the phase between 0 and 2ir. An example of an arrangement of nanopillars 17 of cylindrical shape with a determined height and different diameters is illustrated in [Fig.4].

[0054] By way of example, and according to a preferred embodiment, the light source 4 can be configured to emit a light beam with a wavelength equal to 590nm. In this embodiment, the light device is for example a flashing light, that is to say a signal light, controllable by the driver of the vehicle, and intended to indicate an intention to turn right or left.

[0055] In this particular example, the refractive index n1 of the material used for the substrate is equal to 1.52 while the refractive index n2 for the nanopillars is equal to 2.36. Still in this particular example, the height of the nanopillars 17 is 600 nm and the diameter of the nanopillars 17 can be between 50 nm and 150 nm.

[0056] Furthermore, the arrangement of the nanopillars 17 in the nanostructure 16 of the meta-lens 15 may be configured so that the latter has a structure suitable for projecting an image comprising a pattern onto the ground 3 in front of the vehicle 1. The geometric pattern of the projected image preferably has a simple geometric shape. It may, for example, be an arrow indicating a direction, a pictogram or a set of shapes and / or bands and / or lines.

[0057] According to a preferred embodiment, the light device 2 comprises a multitude of light sources 4 and a multitude of meta-lenses 15. In this preferred embodiment, the light device 2 therefore 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 light sources 4 may be identical to each other or different from each other. In the latter case, each light source 4 may for example have a different wavelength, and be associated with a meta-lens 15 designed for this type of monochromatic wavelength source, to thus emit a dynamic and unique optical waveform.

[0058] In this same embodiment, the multitude of meta-lenses 15 is arranged in rows and columns within the optical device 14 so as to form a matrix, as illustrated in Figures 2 and 3. In this same embodiment, the multitude of light sources 4 is also arranged in rows and columns so as to form a matrix, as illustrated in [Fig.2]. 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. Thus, each meta-lens 15 is passed through by the light beam F produced specifically by the light source 4 with which the meta-lens 15 is associated.

[0059] Such a matrix arrangement of the light sources 4 and the meta-lenses 15 associated with said light sources 4 may prove to be more compact than the arrangement of the images on the edge of a mask 5' known from the state of the art. In other words, such a matrix arrangement of certain components of the light device 2 may contribute to the overall compactness of said light device 2.

[0060] Furthermore, the optical device 14 which serves as a support for the at least one meta-lens 15 can be held in a fixed position, unlike the rotating mask 5' of the state of the art. This makes it possible to ensure better stability of the lighting device 2 as a whole. In addition, the optical device 14 which serves as a support for the at least one meta-lens 15 does not need to be set in motion, unlike the rotating mask 5' of the state of the art. In this way, the lighting device 2 according to the invention does away with the presence of a motor.

[0061] Advantageously, a light device 2 according to the invention comprising an optical device 14 which serves as a support for at least one meta-lens 15 is less subject to vibrations than a rotating mask 5' of the state of the art. Such a light device 2 can therefore prove to be more robust and project images for which the risk of a blurred display under the effect of vibrations is much lower compared to a light device 2' known from the state of the art.

[0062] The lighting device 2 is also more compact than the lighting device 2' known from the state of the art. It can therefore be integrated more easily and more discreetly anywhere in a motor vehicle. The lighting device can thus be positioned in positions allowing optimal projection angles to be achieved. This makes it possible to achieve better uniformity of the light intensity of the pattern projected onto the ground.

[0063] Advantageously, the light sources 4 can be switched on and / or off in the desired order, which has the consequence that the light beams F from said light sources 4 pass through the meta-lenses 15 with which they are associated in the order of activations and deactivations of the light sources 4. Thus, the order does not depend on the arrangement of the meta-lenses 15 within the optical device 14, which can offer more diversity and / or simplicity in the change of image projected on the ground 3 around the motor vehicle. It is in particular possible to switch on several light sources 4 at the same time and therefore to simultaneously project several light zones on the ground 3 around the motor vehicle 1, which makes it possible to compose a great diversity of patterns and to project a dynamic animation.

[0064] According to a particular embodiment illustrated in [Fig.5], a liquid crystal layer 18 and a voltage source 19 adapted to control an electric field passing through the liquid crystal layer 18 can be associated with the meta-lens 15 to form a variable focal length lens thanks to the phase change of the liquid crystals 18. This variable focal length lens is arranged on the path of the light beam F produced by the at least one light source 4. The liquid crystal layer 18 comprises a set of liquid crystals whose orientation can be controlled by means of the electric field applied to it. Such a variable focal length lens therefore makes it possible to adapt the focal length f1, f2 as a function of the location of the light device 2 relative to the ground 3 around the motor vehicle 100 onto which the light zone(s) are projected. Advantageously, each meta-lens 15 of the matrix described above can be associated with an individually controllable liquid crystal layer 18. Thus, the light device 2 can produce a plurality of light beams, each light beam having its own focal length.

[0065] It is also possible to use a projection lens in order to shape the light beam F and direct it towards the ground 3, as illustrated in [Fig. 6]. Generally speaking, a projection lens is capable of shaping a light beam in a defined spatial field so that said light beam F is projected in accordance with the functions that the lighting device 2 must fulfill. In other words, a projection lens makes it possible to define the shape of the light beam at the end of the lighting device 2. Thus, a projection lens can make it possible to define the width and / or the height of the light beam F, as well as its length, that is to say up to what distance the light beam F can illuminate, and / or its angle of inclination.

[0066] In the case considered here, the angle of inclination is such that an image comprising a pattern is projected onto the ground 3 at the front, at the rear or on at least one of the sides of the motor vehicle 1. In the example illustrated in [Fig. 6], the pattern projected onto the ground 3 at the rear of the motor vehicle 1 comprises a plurality of arrows. Such a light device 2 thus makes it possible to effectively communicate the intentions of the driver of the motor vehicle to other road users and in particular to pedestrians.

[0067] Unlike the known lighting devices of the state of the art, the lighting device 2 does not include any optical mask, nor any means of deflecting the light towards a light well. Thus all, or at least almost all, of the light produced by the light source 4 is projected onto the ground to produce a light image. The lighting device 2 heats up less since it does not block any light rays.

[0068] It is therefore possible to design a more compact and lighter lighting device 2 which can be easily integrated into a motor vehicle 1. Such a lighting device 2 is capable of projecting one or more images comprising a pattern and the position and / or orientation of which can be adapted. Such a lighting device 2 according to the invention is not or only slightly affected by possible shocks and / or vibrations generated by the use of the motor vehicle 1 in which said lighting device 2 is integrated and demonstrates better thermal performance. Thus, a lighting device 2 according to the invention therefore offers a more robust and more reliable alternative than the 2' light devices known from the state of the art.

Claims

Claims

1. Lighting device (2) for a motor vehicle (1), the lighting device (2) being configured to project an image around the vehicle (1), the lighting device (2) being characterized in that it comprises: • at least one light source (4) configured to produce a monochromatic light beam (F); • at least one optical device (14) juxtaposed with the light source (4) so ​​that the light beam (F) produced by the light source (4) passes through the optical device (14), said optical device (14) comprising at least one meta-lens (15) configured to modify at least one property of the wavefront of the light beam (F).

2. Luminous device (2) according to claim 1, characterized in that the meta-lens (15) of the optical device (2) comprises at least one nanostructure (16) configured to modify the amplitude and / or the phase of the light beam (F) produced by the light source (4) and passing through the optical device (14).

3. Luminous device (2) according to the preceding claim, characterized in that the nanostructure (16) comprises a transparent substrate with an arrangement of nanopillars (17) on the surface and in that the nanopillars (17) all have the same height.

4. Luminous device (2) according to the preceding claim, characterized in that the nanopillars (17) have sections of different sizes from each other.

5. Luminous device (2) according to one of claims 3 or 4, characterized in that the nanopillars (17) have a cylindrical shape and in that they comprise a base of circular shape.

6. Luminous device (2) according to the preceding claim, characterized in that the diameter of the nanopillars (17) is between 50 nm and 150 nm.

7. Luminous device (2) according to one of the preceding claims, characterized in that it comprises a multitude of light sources (4) and a multitude of meta-lenses (15), and in that each monochromatic light source (4) is associated with a meta-lens (15) which is specific to it.

8. Luminous device (2) according to the preceding claim, characterized in that the multitude of meta-lenses (15) is arranged in rows and columns on the optical device (14) so ​​as to form a matrix, and in that the multitude of light sources (4) is also arranged in rows and columns so as to form a matrix such that each light beam (F) produced by one of the monochromatic light sources (4) passes through the meta-lens (15) with which said light source (4) is associated.

9. Luminous device (2) according to one of the preceding claims, characterized in that it further comprises at least one layer of liquid crystals (18) extending against the at least one meta-lens (15) and a voltage source (19) configured to apply an electric field to the layer of liquid crystals (18) to form at least one variable focal length lens thanks to the phase change of the liquid crystals (18) and / or in that it comprises a projection lens configured to shape the light beam (F) and to orient said light beam (F) towards the ground.

10. Motor vehicle characterized in that it comprises a light device according to one of the preceding claims.

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