Optical system comprising a projection surface capable of reflecting at least one predefined wavelength towards a user

Abstract

The invention relates to an optical projection system (1) comprising a laser emitter (3) configured to emit at least one light beam (Fx) and a projection surface (2) that comprises, arranged successively in a direction of propagation of the at least one light beam (Fx): a protective layer (6), a scattering layer (7), an optical filter (8) configured to reflect at least one predefined wavelength of the at least one light beam (Fx) and an absorbent layer (9) configured to absorb at least one wavelength not reflected by the at least one filter (8).

Description

Optical system comprising a projection surface capable of reflecting at least one predefined wavelength towards a user

[0001] The invention relates to an optical system comprising a laser emitter and a projection surface capable of reflecting at least one predefined wavelength of at least one light beam towards a user. The invention also relates to a projection surface for an optical system according to the invention. The invention further extends to a vehicle equipped with the optical system and / or the projection surface according to the invention. Finally, the invention relates to a method of using the optical system.

[0002] Laser light sources typically emit a directional beam of light, offering greater efficiency than LED light sources. However, the high brightness of laser light sources makes them susceptible to eye damage if viewed directly, thus rendering them dangerous if used improperly or unsafely.

[0003] This drawback results in the integration of laser light sources, particularly in the automotive sector, being regulated and limited. For example, the power of laser light sources integrated into vehicle interior information display systems is significantly restricted. Consequently, the level of contrast and detail achievable with such laser light sources is reduced, making them unsuitable for projecting information onto projection surfaces, especially in bright daylight.

[0004] Indeed, sunlight can reach up to 100,000 lux per day across the entire solar spectrum. For information projected onto a vehicle's projection surface to be visible, its brightness must be greater than the natural or ambient light of the surface onto which it is projected. Natural light typically depends on both the amount of ambient light and the reflectance of the projection surface. The ratio between the brightness of the projected information and the natural light of the projection surface is called the luminance contrast ratio, or LCR. Projected information is generally considered visible when the luminance contrast ratio is greater than or equal to 1.5, meaning that the projected information is 50% brighter than the surface onto which it is projected.

[0005] The invention falls within this context and aims to offer an alternative to known optical systems allowing optimization of the contrast of information projected onto a projection surface while ensuring safe use of laser light sources, particularly for integration into a motor vehicle.

[0006] To this end, the invention relates to an optical projection system comprising a projection surface and a laser emitter configured to emit at least one light beam towards the projection surface, said projection surface comprising successively, according to a direction of propagation of at least one light beam: - a protective layer, in particular transparent or translucent; - a diffusing layer, in particular translucent and / or opalescent; - an optical filter, comprising at least one layer, configured to reflect at least one predefined wavelength of at least one light beam; and - an absorbing layer configured to absorb at least one wavelength not reflected by the filter.

[0007] Optionally, the optical system further includes an oscillating mirror device configured to reflect at least one light beam emitted by the laser emitter towards the projection surface.

[0008] Specifically: - the filter is configured to reflect at least one beam of light when it has an angle of incidence between 20 and 70°, or even between 30 and 60°; and / or - the filter is an optical filter selected from a Notch filter or a Rugate filter.

[0009] According to examples of implementation, the protective layer: - is made of a plastic material and / or containing silica; and / or - measures 10 to 100 µm in thickness.

[0010] According to embodiment examples, the diffusing layer comprises a plastic material, such as polycarbonate and / or polymethyl methacrylate, in which diffusing microstructures are arranged.

[0011] Optionally: - the diffusing microstructures are microbeads of air and / or glass, in particular with dimensions less than or equal to 100 µm, for example between 1 and 70 µm; and / or - the diffusing layer measures from 100 to 3000 µm in thickness.

[0012] For example, the absorbent layer is made from a material selected from wood, leather and / or fabric.

[0013] Optionally but preferably, the laser emitter includes a plurality of RGB type laser light sources combining red(s), green(s) and blue(s) laser light sources to project at least one light beam.

[0014] Optionally, the optical system further includes an optical projection device, disposed downstream of the mirror device oscillating in a direction of propagation of at least one light beam, said device comprising at least one projection lens and / or at least one mirror.

[0015] The invention also extends to a projection surface for an optical projection system according to the invention, comprising: - a protective layer, in particular transparent or translucent; - a diffusing layer, in particular translucent and / or opalescent; - a filter, comprising at least one layer, configured to reflect at least one predefined wavelength of at least one light beam; and - an absorbing layer configured to absorb at least one wavelength not reflected by the filter.

[0016] The invention also relates to a vehicle comprising an optical projection system and / or a projection surface according to the invention, in which the projection surface is included in a dashboard, a foot holding a windshield and / or a steering wheel of the vehicle.

[0017] The invention also relates to a method of projecting a light beam by means of an optical system according to the invention in an environment in which sunlight and / or ambient light is projected or diffused, the method comprising: - the projection of at least one light beam towards the projection surface; and - the diffusion of at least a part of the at least one light beam by means of the diffusing layer; - the reflection of at least one predefined wavelength of the at least one light beam towards a user by means of at least one filter; - the absorption of at least one predefined wavelength, distinct from the at least one reflected wavelength, by means of the absorbing layer, said absorbed wavelength being in particular emitted by sunlight and / or ambient light.

[0018] Further details, features and advantages will become clearer upon reading the detailed description given below, which is indicative and not exhaustive, in relation to the various implementation examples illustrated in the following figures:

[0019] This is a general schematic representation of an optical system according to the invention.

[0020] Laest is a general schematic representation of a vehicle comprising the optical system according to the invention and of which an optical surface is a dashboard.

[0021] This is a schematic representation of an embodiment in which the optical surface includes a Notch filter.

[0022] This is a graph illustrating an evolution of the reflectivity of the filter shown at different wavelengths of the visible light spectrum.

[0023] This is a graph illustrating an evolution of the reflectivity of the filter shown at different wavelengths of the visible light spectrum.

[0024] This is a schematic representation of the reflection of part of a light beam by the filter illustrated in the figure.

[0025] This is a schematic representation of an embodiment in which the optical surface includes a Rugate filter.

[0026] This is a graph illustrating an evolution of the reflectivity of the filter shown at different wavelengths of the visible light spectrum.

[0027] Figures 1a to 6 schematically illustrate examples of embodiments of an optical system 1 according to the invention. In particular, the optical system 1 can be included in a motor vehicle 10. According to one non-limiting embodiment, the optical system 1 is included in an information display system located in the passenger compartment of the vehicle 10, such as a head-up display system or a display system projecting information onto a projection surface 2 contained within a stand framing the windshield of the vehicle 10, a projection screen, the dashboard of the passenger compartment, or the steering wheel.

[0028] By convention in the description below, the terms "first" or "second" are intended to distinguish similar elements and not to define a hierarchy among those elements. Similarly, the terms "upstream" and "downstream" refer to the direction of propagation of a given light beam.

[0029] In general, the optical system 1 according to the invention comprises a laser emitter 3 configured to emit at least one light beam Fx, an oscillating mirror device 4, and at least one projection surface 2 according to the invention. The following description refers to a single projection surface 2; however, it is understood that the optical system 2 may comprise a plurality of projection surfaces 2 according to the invention.

[0030] Optionally, as further detailed below, the optical system 1 further includes an optical device 5 disposed downstream of the oscillating mirror device 4 in a direction of propagation of at least one light beam Fx.

[0031] The laser emitter 3 is configured to emit at least one light beam Fx towards the oscillating mirror device 4. Optionally, but preferably, the laser emitter 3 includes a plurality of laser light sources. For example, these sources include red, green, and / or blue laser light sources. If the laser emitter 3 includes at least one red laser light source, one green laser light source, and one blue laser light source, then the laser emitter 3 is an "RGB laser emitter," capable of emitting a light beam Fx of the desired color. Each laser light source in the laser emitter 3 emits a primary light beam Fx, and these primary light beams are combined to form at least one light beam Fx, also referred to as the combined light beam Fx. This at least one light beam Fx is then directed towards a reflective surface of the oscillating mirror device 4.In particular, the different laser light sources are controlled independently of each other.

[0032] Note that, in the description below, we will distinguish at least one light beam Fx from sunlight Lsx and ambient light Lax, corresponding to a brightness resulting from elements external to the vehicle and / or external to the optical system 1, such as public lighting or lights of vehicles circulating in the road infrastructure.

[0033] The oscillating mirror device 4 is configured to reflect at least one light beam Fx emitted by the laser emitter 3 towards the projection surface 2. This at least one light beam Fx forms a light spot on the oscillating mirror device 4, which is reflected back to the projection surface 2 to project an image Ix or information onto it. Optionally, the at least one light beam Fx reflected by the oscillating mirror device 4 first passes through the optical device 5 before reaching the projection surface 2, said optical device 5 being interposed between the oscillating mirror device 4 and the projection surface 2.

[0034] The oscillating mirror device 4 includes, in a conventional manner, a movable scanning mirror that reflects at least one light beam Fx according to the angle of rotation at which it is positioned. The scanning mirror can be of any known type and can be driven using conventional drive methods. For example, the oscillating mirror device 4 includes a mechanical device for oscillating the mirror through a plurality of different angular orientations.

[0035] According to an alternative not shown, at least one light beam Fx can be directly projected, by the laser emitter 3, towards the projection surface 2.

[0036] For example, the oscillating mirror device 4 is of the MEMS type, from the English "Micro Electro Mechanical Systems," meaning "micro-electromechanical system," allowing the orientation of at least one incident light beam along a plurality of angular orientations over time. According to a classic, non-limiting, and undetailed embodiment, the oscillating mirror device 4 is configured to implement a sequential two-dimensional scan along lines to form an image Ix on the projection surface 2, also known as a "raster scan." Alternatively, the oscillating mirror device 4 is configured to implement a "vector" or "Lissajous" type scan.

[0037] When the optical system 1 includes a projection optical device 5, this device is positioned downstream of the oscillating mirror device 4 in a direction of propagation of at least one light beam Fx. Optionally, the optical system 1 is configured so that the at least one light beam Fx is collimated when it reaches the projection surface 2. Alternatively, the at least one light beam Fx is not collimated so that it is configured to converge at a defined distance, in particular within the projection surface 2.

[0038] As is known, the optical device 5, not detailed, may include at least one projection lens and / or at least one mirror, for example a plurality of mirrors of which at least one is a reflecting mirror configured to direct at least one light beam Fx towards the projection surface 2.

[0039] The projection surface 2 generally comprises, successively according to the direction of propagation of at least one light beam Fx, at least one protective layer 6, in particular transparent, a diffusing layer 7, a filter 8 comprising at least one layer and configured to reflect at least part of the at least one light beam Fx, and an absorbing layer 9 configured to absorb at least one wavelength of light not reflected by the filter, for example, light emitted by sunlight Lsx and / or ambient light Lax. In other words, the projection surface 2 comprises a stack of a plurality of layers. It should be noted that the following description, relating to the projection surface 2 included in the optical system 1 and / or the vehicle 10, also extends to the projection surface 2 as such, intended for an optical system 1 and / or a vehicle 10 according to the invention.

[0040] The protective layer 6 is configured to provide protection, or resistance, to the projection surface 2 against shocks or impacts. It comprises an outer face 61 of the projection surface 2, configured to be oriented towards the laser emitter 3 within the vehicle 10 or the optical system 1 and to be as close as possible to said laser emitter 3.

[0041] Optionally, but preferably, protective layer 6 is transparent. Alternatively, protective layer 6 is translucent and has a transmission index of 70% or higher. In some embodiments, protective layer 6 is made of a plastic material, such as polyurethane or polycarbonate, and / or a material containing silica.

[0042] Note that the description below describes a projection surface 2 comprising a single protective layer 6. It is understood however that said projection surface 2 may comprise a plurality of superimposed protective layers 6.

[0043] Optionally, but preferably, the protective layer 6 is at least partially smooth, or substantially smooth. In particular, the outer face 61 is smooth or substantially smooth. Alternatively, the protective layer 6 is at least smooth in areas dedicated to the projection of information and / or images Ix. In particular, the protective layer 6 is 10 to 100 µm thick, for example, 50 µm thick. The thickness of said layer is measured here along a direction orthogonal to the projection surface 2, between the outer face 61 and an inner face 62 of the protective layer 6, opposite the outer layer.

[0044] The diffusing layer 7 is positioned in contact with the protective layer 6. Specifically, the diffusing layer 7 is translucent and / or opalescent. For example, it has a transmission index of 40% or less. Optionally, the diffusing layer 7 has a transmission index between 30% and 90%, or even between 40% and 85%. The diffusing layer 7 functions as a diffuser, meaning it is designed to disperse or scatter at least a portion of the light beam Fx.

[0045] Preferably, the diffusing layer 7 comprises a substrate made of plastic material, such as polycarbonate and / or polymethyl methacrylate, also known by the abbreviation PMMA, or silicone, in which diffusing microstructures 71 are arranged. In particular, said diffusing microstructures 71 each have a symmetrical geometry. Preferably, said diffusing microstructures 71 are spherical. According to an alternative not detailed, said diffusing microstructures 71 are prisms. The diffusing microstructures 71 are, in particular, less than or equal to 100 µm in size, for example, with dimensions ranging from 1 to 70 µm.

[0046] Optionally, but preferably, the diffusing microstructures 71 are air and / or glass microbeads. In particular, they have dimensions, i.e., diameter, less than or equal to 100 µm, for example, dimensions between 1 and 70 µm.

[0047] These diffusing microstructures 71 can thus contribute to giving the diffusing layer 7 its translucent and / or opalescent appearance. This principle is based on Mie theory, also known as Mie scattering, and ensures at least partial backscattering of sunlight Lsx and / or ambient light Lax. Furthermore, the diffusing microstructures 71 allow for the scattering, that is, the splitting, of at least one beam of light Fx propagating through the projection surface 2 towards the filter 8. The substrate of the diffusing layer 7 can therefore be transparent, or nearly transparent, or translucent. In particular, the distribution of the diffusing microstructures 71 within the diffusing layer 7 is homogeneous or nearly homogeneous.

[0048] Advantageously, the diffusing layer 7 is also capable of diffusing at least part of the light beam Fx reflected by the filter 8, as further described below and as illustrated in figures 2 and 5.

[0049] In particular, the diffusing layer 7 measures from 100 µm to 3000 µm in thickness, or even from 400 to 2000 µm in thickness. The thickness of said layer is measured here along the direction orthogonal to the projection surface 2, between a first face 72, facing the protective layer 6 and a second face 73, opposite the first face 72, and facing the filter 8. In particular, the thickness of the diffusing layer 7 is homogeneous or substantially homogeneous.

[0050] The filter 8 is configured to reflect at least one predefined wavelength, specifically at least one predefined range of wavelengths, from at least one light beam within the visible spectrum towards a user. In particular, the filter 8 is configured to reflect at least one predefined wavelength, specifically at least one predefined range of wavelengths, from at least one light beam Fx when it has an angle of incidence between 20° and 70°, or even between 30° and 60°. The angle of incidence is defined here as the angle of the at least one light beam Fx entering a primary face of the filter 8, facing the diffusing layer 7, i.e., at the exit of the diffusing layer 7. In other words, such an angle of incidence, measured at the filter 8, depends at least on the position of the laser emitter 3 and the scattering angle generated by the diffusing layer 7.This principle advantageously limits the amount of sunlight Lsx and / or ambient light Lax reflected towards a user, thereby optimizing the contrast between the brightness of the projected information or image Ix and the natural or ambient brightness of the projection surface. "Natural brightness" here refers to the amount of ambient lighting and the reflectance of the projection surface, i.e., the luminance of the surface illuminated by sunlight Lsx or any light source other than the laser emitter 3.

[0051] The filter 8 comprises at least one layer configured to reflect at least one predefined wavelength, in particular at least one predefined range of wavelength values, from at least one light beam Fx or a plurality of predefined ranges of wavelength values. In particular, as detailed below, the filter 8 comprises a plurality of layers forming a layer stack, such stacking being considered along the direction of propagation of the at least one light beam Fx.

[0052] According to alternative implementations, the 8 filter is an optical 8 filter selected from either an 8 Notch filter or an 8 Rugate filter.

[0053] This illustrates an example of an 8-notch filter, also known as a "quarter wave stack." This 8-notch filter comprises a stack of multiple layers, specifically layers made of dielectric materials. In particular, the 8-notch filter includes an alternation of at least one low-refractive-index layer and at least one high-refractive-index layer, forming a pair of layers, each layer having a specific thickness. Specifically, at least one layer has a thickness equal to one-quarter of a selected wavelength λK. The 8-notch filter is configured such that the multiple layers exhibit multiple interference conditions, for example, interference conditions existing at λ, λ / 3, λ / 4, and / or λ / 5.

[0054] In particular, within the filter 8 and / or a pair of layers considered, at least one low refractive index layer is made of silicon dioxide, or silica, with the formula SiO2, for example, whose refractive index is on the order of 1.46, while at least one high refractive index layer is made of titanium dioxide, with the formula TiO2, whose refractive index is, for example, on the order of 2.64. In particular, said layers are arranged so that a high refractive index layer is placed in contact with the diffusing layer 7.

[0055] In the example illustrated in the figure, the initial reflection of part of the at least one light beam Fx by a first layer 81, with a high refractive index, changes the phase of a first reflected wavelength of the at least one light beam Fx by 180° when the refractive index of the air, or in this case of the diffusing layer 7, is strictly less than one refractive index of the first layer 81. Part of the at least one light beam Fx that is refracted is reflected on a second layer 82, with a low refractive index, and does not undergo a phase change since the refractive index of the second layer 82 is strictly less than the refractive index of the first layer 81.Conversely, the portion of the at least one light beam Fx thus refracted by the second layer 82 travels an additional distance through the first layer 81, corresponding in particular to half a wavelength in the case of layers with a thickness equal to λ / 4 of the selected wavelength, which changes its phase by 180 degrees. It therefore interferes constructively with the first reflected wavelength. At the interface between the second layer 82 and a third layer 83, with a high refractive index, a portion of the at least one refracted light beam Fx travels the entire wavelength but undergoes a phase change upon reflection, which means that it again interferes constructively. This principle is repeated for a defined number of stacked layers.

[0056] Thus, by considering these reflections and refractions iteratively, the filter interferes constructively with the parts of at least one reflected light beam Fx, maximizing their reflection at specific wavelengths. For example, the filter 8 can exhibit a plurality of interference conditions existing, without limitation, at values ​​equal to λ, λ / 3, λ / 4 and / or λ / 5, the wavelength λ being selected such that said interference values ​​correspond to at least one wavelength emitted by the laser emitter 3. Apart from the interference values ​​thus fixed, the filter 8 exhibits a high transmittance so as to allow the propagation of at least a part of the at least one light beam Fx, of sunlight Lsx and / or of ambient light Lax towards the absorbing layer 9. For example, the filter 8 has a transmittance strictly greater than the transmittance of the diffusing layer 7.In particular, filter 8 has a transmittance greater than or equal to 60%.

[0057] In particular, filter 8 is configured to form interference at at least one wavelength corresponding to a wavelength emitted by laser emitter 3. In other words, filter 8 is configured to exhibit the highest reflectivity for at least one wavelength value emitted by laser emitter 3, in particular for a plurality of wavelength values ​​emitted by laser emitter 3.

[0058] For example, as illustrated in Figure 3b, optionally but preferably, filter 8 is configured to interfere constructively by reflection with at least one light beam Fx at specific wavelengths corresponding to the wavelengths of at least one red laser light source, at least one green laser light source, and at least one blue laser light source in the case of a 3-RGB laser emitter. In particular, at least one red laser light source emits a light signal at a wavelength between 630 and 660 nm, while at least one blue laser light source emits a light signal at a wavelength between 440 and 460 nm, and at least one green laser light source emits a light signal at a wavelength between 510 and 540 nm.

[0059] Note that, in the, at least one light beam Fx is represented, for illustrative purposes and in a non-limiting manner, as comprising a plurality of distinct wavelengths, here illustrated by distinct dotted lines, corresponding to specific wavelengths emitted by red, blue and green laser light sources.

[0060] The projection surface 2, particularly the filter 8, is thus capable of maximizing the reflection of at least one light beam Fx at wavelengths corresponding to the wavelengths of the laser emitter 3, thereby intensifying specific colors of at least one final image Ix projected onto the projection surface 2 and increasing their contrast relative to sunlight Lsx and / or ambient brightness Lax. Conversely, wavelengths distinct from those emitted by the laser emitter 3 are at least partially transmitted to the absorbing layer 9. The luminance contrast ratio (LCR) of the image Ix, or the information projected onto the projection surface 2, is thus increased and optimized compared to conventional projection surfaces 2 of the prior art.

[0061] Figure 8 illustrates an example of the realization of a Rugate filter, also known as a gradient-index filter. This filter comprises a stack of multiple layers, including layers made of dielectric materials or layers coated with a dielectric coating. Specifically, each layer is configured to reflect at least one selected wavelength. In particular, the filter is configured so that the plurality of layers is capable of reflecting at least one wavelength corresponding to a wavelength emitted by the laser emitter. This principle is achieved by a periodic and continuous change in the refractive index of each layer, or coating covering each layer, with the refractive index varying continuously in at least a portion of the filter.

[0062] For example, as illustrated in Figure 1, optionally but preferably, filter 8 is configured to reflect specific wavelengths corresponding to wavelengths of at least one red laser light source, at least one green laser light source, and at least one blue laser light source in the case of a 3-RGB laser emitter. For example, at least one red laser light source emits a light signal at a wavelength between 630 and 660 nm, while at least one blue laser light source emits a light signal at a wavelength between 440 and 460 nm, and at least one green laser light source emits a light signal at a wavelength between 510 and 540 nm.

[0063] Specifically, in the example illustrated in Figure 1, the filter 8 comprises a first layer 81' configured to reflect at least one specific wavelength corresponding to a wavelength emitted by at least one red laser light source. The first layer 81' is in contact with the diffusing layer 7. The filter 8 also comprises a second layer 82' configured to reflect at least one specific wavelength corresponding to a wavelength emitted by at least one blue laser light source. The second layer 82' is in contact with the first layer 81' such that the first layer 81' is interposed between the diffusing layer 7 and the second layer 82'. Finally, the filter 8 comprises a third layer 83' configured to reflect at least one specific wavelength corresponding to a wavelength emitted by at least one green laser light source.The third layer 83' is arranged in contact with the absorbing layer 9. Note that, in the, at least one light beam Fx is represented, for illustrative purposes and in a non-limiting manner, as comprising a plurality of distinct wavelengths, here illustrated by distinct dotted lines, corresponding to specific wavelengths emitted by red, blue and green laser light sources.

[0064] Similar to what was described previously with reference to the Notch filter 8, the Rugate filter 8 is capable of maximizing the reflection of at least one light beam Fx at wavelengths corresponding to the wavelengths of the laser emitter 3, thereby intensifying specific colors of at least one image Ix, or of the information, projected onto the projection surface 2 and increasing their contrast relative to sunlight Lsx and / or ambient light Lax. Conversely, wavelengths distinct from those emitted by the laser emitter 3 are at least partially transmitted to the absorbing layer 9. The luminance contrast ratio of the image Ix or the information projected onto the projection surface 2 is thus increased and optimized.

[0065] The absorbing layer 9 is configured to absorb a wavelength not reflected by the filter 8 and / or at least part of the sunlight Lsx and / or ambient light Lax reaching the projection surface 2 and passing through the various layers described above, i.e. passing through the protective layer 6, the diffusing layer 7 and the filter 8. The projection surface 2 thus makes it possible to absorb at least part of the sunlight Lsx and / or ambient light Lax, whose sources are for example external to the vehicle 10, in order to prevent their perception by the user, in particular so as to absorb at least a wavelength not reflected by the filter 8.

[0066] The absorbent layer 9 can be made from any standard material used in vehicle interior fittings 10, including any standard material used in vehicle dashboards 10. For example, the absorbent layer 9 can be made from a material selected from wood, leather, plastic, and / or fabric. Specifically, the absorbent layer 9 can be made in any color, for example, black, gray, white, woodgrain, or another finish. This absorption is made possible by the presence of pigments within the absorbent layer 9.

[0067] The invention also extends to a method of projecting a light beam Fx onto the projection surface 2 in an optical system 1 according to the invention. In other words, said method can also be considered a method of operating the optical system 1 according to the invention or a method of operating the vehicle 10 comprising said optical system 1. It is understood that the preceding description, relating to the optical system 1 and the vehicle 10, applies mutatis mutandis to the method according to the invention and vice versa.

[0068] The method includes the emission of at least one light beam Fx through the laser emitter and towards the oscillating mirror device 4, said oscillating mirror device being configured to reflect the at least one light beam Fx towards the projection surface 2. In particular, such projection is carried out in an environment in which sunlight and / or ambient light Lax is projected or diffused.

[0069] The method includes, when the laser emitter 3 emits at least one light beam Fx, the scattering of at least a part of the at least one light beam Fx through the scattering layer 7. The scattering layer 7 is thus configured to scatter at least a part of the at least one light beam Fx towards the filter 8. Also, advantageously, the scattering layer 7 is configured to perform the backscattering of at least a part of the sunlight Lsx and / or ambient light Lax, i.e. backwards, towards the protective layer 6 relative to the direction of propagation of the light and not forwards, i.e. towards the filter 8 as described above.

[0070] The method then includes reflecting at least a portion of the at least one light beam Fx, in particular at least one predefined wavelength of the at least one light beam Fx, through the filter 8, as described previously. Optionally, but preferably, the method includes reflecting a plurality of wavelengths of the at least one light beam Fx through the filter 8, in particular wavelengths corresponding to the wavelengths emitted by the laser emitter 3, particularly by an RGB laser emitter 3.Optionally, but preferably, the process includes maximizing, or increasing, the reflection of at least one light beam Fx at wavelengths corresponding to the wavelengths emitted by the laser emitter 3, in particular so as to intensify specific colors of the at least one final image Ix projected onto the projection surface 2 and so as to increase their contrast with respect to sunlight Lsx or ambient light. Conversely, wavelengths distinct from those emitted by the laser emitter 3 are at least partially transmitted to the absorbing layer 9.

[0071] Advantageously, the process also includes the diffusion, via the diffusing layer 7, of at least a part of the light beam Fx reflected by the filter 8.

[0072] The process finally includes the absorption of at least one predefined wavelength, distinct from at least one reflected wavelength, via the absorbing layer 9.

[0073] Thus, the present invention proposes an optical system comprising a projection surface that advantageously optimizes the luminance of images, or information, projected via the laser emitter. The invention advantageously increases the ratio between the brightness of the projected information and the natural brightness of the projection surface, also known as the luminance contrast ratio, thereby making it more contrasted and visible to a vehicle user without requiring an increase in the laser emitter's power. The eye safety of users can thus be ensured, while the quality of the information projection in the vehicle can be guaranteed both day and night.

[0074] The present invention cannot, however, be limited to the means and configurations described and illustrated herein and it also extends to any equivalent means or configuration and to any technically operative combination of such means insofar as they ultimately fulfill the functionalities described and illustrated in this document.

Claims

Optical projection system (1) comprising a projection surface (2) and a laser emitter (3) configured to emit at least one light beam (Fx) towards the projection surface (2), said projection surface (2) comprising successively, according to a direction of propagation of the at least one light beam (Fx): - a protective layer (6), in particular transparent or translucent; - a diffusing layer (7), in particular translucent and / or opalescent; - an optical filter (8), comprising at least one layer, configured to reflect at least one predefined wavelength of the at least one light beam (Fx); and - an absorbing layer (9) configured to absorb at least one wavelength not reflected by the filter (8). Optical projection system (1) according to the preceding claim, wherein: - the filter (8) is configured to reflect at least one light beam (Fx) when the beam has an angle of incidence between 20 and 70°, or even between 30 and 60°; and / or - the filter (8) is an optical filter selected from a Notch filter (8) or a Rugate filter (8). Optical projection system (1) according to any one of the preceding claims, wherein the protective layer (6): - is made of a plastic material and / or comprising silica; and / or - measures 10 to 100 µm in thickness. Optical projection system (1) according to any one of the preceding claims, wherein the diffusing layer (7) comprises a plastic material, such as polycarbonate and / or polymethyl methacrylate, in which diffusing microstructures (71) are arranged. Optical projection system (1) according to the preceding claim in which: - the diffusing microstructures are microbeads of air and / or glass, in particular of dimensions less than or equal to 100 µm, for example between 1 and 70 µm; and / or - the diffusing layer (7) measures from 100 to 3000 µm in thickness. Optical projection system (1) according to any one of the preceding claims, wherein the absorbing layer (9) is made of a material selected from wood, leather and / or fabric. Optical projection system (1) according to any one of the preceding claims, wherein the laser emitter (3) comprises a plurality of RGB type laser light sources combining red(s), green(s) and blue(s) laser light sources enabling the projection of at least one light beam (Fx). Projection surface (2) for an optical projection system (1) according to any one of the preceding claims, comprising: - a protective layer (6), in particular transparent or translucent; - a diffusing layer (7), in particular translucent and / or opalescent; - a filter (8), comprising at least one layer, configured to reflect at least one predefined wavelength of at least one light beam (Fx); and - an absorbing layer (9) configured to absorb at least one wavelength not reflected by the filter (8). Vehicle (10) comprising an optical projection system (1) according to any one of claims 1 to 7 and / or a projection surface (2) according to the preceding claim, wherein the projection surface (2) is included in a dashboard, a foot holding a windshield and / or a steering wheel of the vehicle (10). A method for projecting a light beam (Fx) via an optical system (1) according to any one of claims 1 to 7 in an environment in which sunlight (Lsx) and / or ambient light (Lax) is projected or diffused, the method comprising: - the projection of at least one light beam (Fx) towards the projection surface (2); and - the diffusion of at least a part of the at least one light beam (Fx) via the diffusing layer (7); - the reflection of at least one predefined wavelength of the at least one light beam (Fx) towards a user via the at least one filter (8); - the absorption of at least one predefined wavelength, distinct from the at least one reflected wavelength, via the absorbing layer (9), said absorbed wavelength being in particular emitted by sunlight (Lsx) and / or ambient light (Lax).

Images