Backlighting device for a head-up display system

Abstract

Title: Backlighting device for a head-up display system The invention relates to a backlighting device (8) for a head-up display system (2), said device comprising: - at least one matrix (18) of light sources, configured to emit light beams (20); - at least one optical component (22) comprising: o a light entry face (24) having a concave shape of concavity directed towards the light sources (19), this light entry face being placed opposite at least one of the light sources; and o a side wall (26) configured to reflect the light beams having penetrated into the optical component via the light entry face in such a way that these reflected beams are directed towards a light exit face (30) of said component. The side wall being flared from the light entry face towards the light exit face. Figure for abstract: Fig. 1

Description

Title of the invention: Backlighting device for a head-up display system

[0001] The invention relates to a backlighting device for a head-up display system, in particular of a vehicle, in particular of a motor vehicle.

[0002] The vehicle can be land, sea or air.

[0003] A head-up display system is known, in particular for a vehicle, adapted to project, at the height of a field of vision ("eye box" in English), for example of a driver of the vehicle, visual information (or an image) such as information necessary for driving (e.g. speed of the vehicle, direction to follow, etc.) and / or safety information (e.g. engine malfunction, presence of an obstacle on the road, etc.).

[0004] Thus, this head-up display system prevents the driver from being forced to look away from the road he is traveling.

[0005] However, the conventional head-up display system suffers, in particular for direct reflection and non-magnification systems, from a low light power efficiency, thus resulting in a loss of brightness of the visual information, due to the fact that a large portion of light beams emitted by the head-up display system is lost in directions other than those corresponding to the field of vision. In other words, in order to compensate for this loss of brightness, it is necessary to emit the light beams with a high light power for the conventional head-up display system (hence, the low light power efficiency).

[0006] In this context, there is a need to address these problems mentioned above.

[0007] The invention aims in particular to improve the directivity of the light beams emitted by the backlighting device.

[0008] The invention thus relates to a backlighting device for a head-up display system, in particular of a vehicle, said device comprising: - at least one matrix of light sources, in particular at least one matrix of a plurality of light-emitting diodes, configured to emit light beams; and - at least one optical component comprising: • a light entry face having a concave shape with concavity directed towards the light sources, this light entry face being placed opposite at least one of the light sources; and • a side wall configured to reflect the light beams having entered the optical component through the light entry face in such a way that these reflected beams are directed towards a light exit face of said component; and the side wall being flared from the light entry face to the light exit face.

[0009] By means of the arrangement of the light entry face, the side wall and the light exit face of the optical component, it is possible to obtain better directivity of the light beams towards a field of vision of the driver. In particular, the fact that the side wall is flared from the light entry face towards the light exit face makes it possible to bend the reflected beams towards the light exit face with better directivity.

[0010] Furthermore, it should be noted that the light output face of the optical component can be adapted to obtain an additional optical function, without there being an additional part. This thus makes it possible to simplify the design and assembly of the backlight device.

[0011] In addition, this better directivity of the light beams makes it possible to increase their brightness, at a given light power, by a factor of 2 to 6, in comparison with a conventional, non-directional backlighting device.

[0012] Furthermore, this backlighting device is compatible with intelligent backlighting technology, for example “local dimming” type backlighting technology.

[0013] According to one aspect of the invention, the backlighting device comprises a plurality of matrices of light sources configured to be controlled individually, so as to each form an individual illumination zone, this illumination zone being intended to illuminate one or more optical components so as to form a plurality of light beam emission assemblies.

[0014] According to one aspect of the invention, each light source is configured to be controlled individually.

[0015] Thus, the backlighting device is compatible with intelligent backlighting technology, making it possible to turn on or off only some of the light sources, or only some of the light source matrices, for example a “local dimming” type backlighting technology allowing very marked contrast.

[0016] According to one aspect of the invention, the light entry face further has the shape of a substantially spherical cap.

[0017] According to one aspect of the invention, the light entry face further has a substantially hemispherical cap shape.

[0018] According to one aspect of the invention, the radius of curvature of the substantially spherical or hemispherical cap is between 0.1 and 10 mm, advantageously between 1 and 3 mm.

[0019] According to one aspect of the invention, the side wall is a frustoconical surface.

[0020] According to one aspect of the invention, the optical component(s) are made of a single block of matter.

[0021] Alternatively, the optical component(s) are made from a plurality of blocks of material, in particular of the same material.

[0022] Alternatively, the optical component(s) are made from a plurality of blocks of material, each block being made from a different material.

[0023] According to one aspect of the invention, the optical component is made by molding a transparent material, in particular transparent polymer, for example polymethyl methacrylate (PMMA) or polycarbonate (PC).

[0024] Alternatively, the optical component is made of at least two different materials with different refractive indices, so as to combine the lens effects.

[0025] According to one aspect of the invention, the matrix of light sources is placed on a printed circuit (or a “printed circuit board” (PCB) according to English terminology).

[0026] Alternatively, the matrix of light sources is placed on a lithographed glass.

[0027] According to one aspect of the invention, the focus of the backlighting device is at distance from the center of the radius of curvature of the light entry face.

[0028] Thus, the fact that the focus is slightly offset from the center of the radius of the curvature makes it possible to spread the field of vision in both directions, namely in length and width, while maintaining the brightness of the light beams.

[0029] The distance between the focus and the center of the radius of the curvature of the light entry face is of the order of millimeters.

[0030] According to one aspect of the invention, the matrix of light sources comprises at least one LED, one MiniLED, one MicroLED, or the combination thereof.

[0031] According to one of the aspects of the invention, the matrix of light sources comprises the light sources spaced apart with a distance p (also called a pitch p) less than or equal to 20 mm, preferably between 2 and 10 mm, more particularly between 5 and 8 mm so as to optimally cover the display surface.

[0032] According to one aspect of the invention, the optical component is arranged to ensure total reflection of the light beams along the side wall in a manner that all light beams entering the light input face are directed towards the output face of said component.

[0033] According to one aspect of the invention, the side wall is inclined relative to the light source in such a way that the light beams are reflected totally towards the exit face. For example, the side wall is inclined so that the angle of incidence of the light beams relative to the normal is substantially 45°. Of course, this angle of incidence can vary according to the refractive index of the material of the optical component.

[0034] According to one aspect of the invention, the surface of the side wall is covered with a reflective deposit to ensure total reflection.

[0035] According to one aspect of the invention, the backlighting device further comprises a light diffuser arranged to spread light beams coming from the optical component(s), so that a field of vision is visible to a driver and / or to one or more passengers of the vehicle.

[0036] According to one aspect of the invention, the light diffuser is arranged to spread the field of vision of the light beams in an elliptical manner. The term "elliptical" is understood to mean when the light beams are slightly diffusing in height and largely diffusing in width. The height is defined in a direction perpendicular to the main plane of the matrix of light sources, while the width is defined in a direction parallel to the main plane of the matrix of light sources.

[0037] According to one aspect of the invention, the light diffuser comprises a diffusion film configured to spread the light beams.

[0038] Thus, the diffusion film makes it possible to obtain a homogeneous field of vision with an overlap of light beams between them, so as to obtain a homogeneous brightness over the entire field of vision. In other words, one avoids having an inhomogeneous field of vision, for example brighter in the center and less bright at the edges of the field of vision.

[0039] According to one aspect of the invention, the light diffuser comprises at least one groove, in particular in the form of a prism having a symmetrical shape, configured to spread the light beams.

[0040] According to one aspect of the invention, the light diffuser comprises a plurality of grooves, in particular in the form of a prism having a symmetrical shape, configured to spread the light beams.

[0041] According to one aspect of the invention, the light diffuser comprises the grooves which are placed opposite the exit of the optical component.

[0042] According to one aspect of the invention, the light diffuser may comprise both a plurality of grooves and a diffusion film.

[0043] According to one aspect of the invention, the grooves are inclined at an angle relative to the normal of the output face, the angle advantageously being between 0 and 45°, preferably between 0 and 30°. Thus, the visibility zone of the image is wider within the field of vision.

[0044] Alternatively, the light diffuser is configured to spread the light beams so that they are visible only to the driver of the vehicle. When the field of vision is at a predetermined distance from the light diffuser, the width of the field of vision is such that the field of vision is visible only to the driver.

[0045] Alternatively, the light diffuser is configured to spread the light beams so that they are visible to both the driver and the passenger(s) of the vehicle. For example, when the field of vision is at a predetermined distance from the light diffuser, the width of the field of vision is such that the field of vision is visible to both the driver and the passenger(s) of the vehicle.

[0046] According to one aspect of the invention, the number of grooves is between 10 and 100.

[0047] According to one aspect of the invention, the grooves are spaced apart, in particular by inter-groove pitches, so as to avoid the moiré effect.

[0048] According to one aspect of the invention, the grooves are regularly spaced apart, with inter-groove pitches of between 50 pm and 5 mm, preferably between 100 pm and 2 mm, so as to avoid the moiré effect.

[0049] According to one aspect of the invention, a ratio between the height h and the diameter d is between 1 and 10, preferably between 3 and 5. The height h is defined between the light entry face and the light exit face of the optical component. The diameter d is defined as the maximum distance separating the ends of the light entry face.

[0050] According to one aspect of the invention, the prisms can be asymmetrical in order to deflect the illumination indicator towards a specific direction, in particular in order to better distribute the illumination in the passenger compartment.

[0051] The invention also relates to a head-up display system, in particular for a vehicle, said head-up display system comprising: - a screen having controllable optical transmission; and - a backlighting device according to the invention.

[0052] According to one aspect of the invention, the screen comprises an input face and an output face, and having, between the input face and the output face of the screen, a controllable optical transmission.

[0053] According to one aspect of the invention, the screen is a liquid crystal display (LCD), for example of the TFT type (according to the English acronym for “Thin-Film Transistors”).

[0054] According to one aspect of the invention, the liquid crystal screen has dimensions of between 1 and 50 inches, i.e. between 2.54 cm and 127 cm, advantageously between 10 and 30 inches, i.e. between 25.4 cm and 76.2 cm.

[0055] According to one aspect of the invention, the backlighting device comprises a so-called "redirection" film configured to turn the illumination indicator towards a specific direction.

[0056] The invention also relates to a vehicle comprising: - a head-up display system as defined above; and - a passenger compartment comprising a windshield provided on one of its external or internal faces with a coating or a mirror configured to compensate for the suppression of a polarization of the light beams, in particular a p polarization of these light beams, by an object or a reflective surface located between the light beams and the field of vision.

[0057] For example, the presence of the coating or the mirror makes it possible to reflect all of the light beams, regardless of the polarization of these light beams.

[0058] According to one aspect of the invention, the mirror is partially reflective.

[0059] This increases the ergonomics of the visual information perceived by the driver or (the passenger(s)). In other words, the reflection of stray light beams that the driver (or the passenger(s)) would perceive if the mirror were entirely reflective is avoided.

[0060] According to one aspect of the invention, the coating or mirror is transparent or opaque. Thus, it is possible to modulate the light contrast of the light beams in order to increase or decrease the visibility of the visual information or the image(s) perceived in the field of vision.

[0061] For example, the transparent coating or the transparent mirror is chosen when the need for brightness is greater (i.e., greater than 10,000 cd / m2), while the opaque coating or the opaque mirror is chosen for the need for less brightness (i.e., between 500 / m2 and 1,000 cd / m2).

[0062] According to one aspect of the invention, the position of the coating or mirror on the external face, on the internal face of the vehicle windshield, or on a complementary part close to the vehicle windshield, can be adapted depending on whether the coating or mirror is sensitive or not to environmental conditions. For example, if the coating or mirror is sensitive to humidity, the coating or mirror is positioned on the internal face of the windshield. The external face is understood to mean the face located outside the passenger compartment of the vehicle. The internal face is the face opposite the external face, and located inside the passenger compartment of the vehicle.

[0063] According to one aspect of the invention, the coating or mirror can be produced by depositing a metal, for example by depositing a metal comprising chromium.

[0064] According to one aspect of the invention, the coating or the mirror can be produced by the deposition of at least one dielectric layer.

[0065] According to one aspect of the invention, the head-up display system further comprises a polarization recycling plate configured to guide at least one polarization of the light beams in one direction. Advantageously, the polarization recycling plate is arranged between the screen and the backlighting device.

[0066] The invention also relates to a method for displaying visual information, said method comprising the following steps: - project, using the display system as defined above, light beams towards the screen having controllable optical transmission; and - reflect the visual information having passed through the screen onto the windscreen in such a way as to form a field of vision visible to a driver or to one or more passengers of the vehicle.

[0067] Alternatively, the method for displaying visual information comprises the following step: - reflect the visual information that has passed through the screen onto the windshield in such a way as to form a field of vision visible only to a driver.

[0068] Other characteristics, details and advantages of the invention will emerge more clearly on reading the description which follows on the one hand, and several exemplary embodiments given for informational and non-limiting purposes with reference to the appended schematic drawings on the other hand, in which:

[0069] [Fig.l] [Fig.l] is a schematic representation, in profile, of a head-up display system according to the invention;

[0070] [Fig.2] [Fig.2] is a schematic representation, in profile, of a system head-up display according to another embodiment variant;

[0071] [Fig.3] [Fig.3] is a schematic representation, in perspective, of a vehicle according to an alternative embodiment;

[0072] [Fig.4] [Fig.4] is a schematic representation, in perspective, of a vehicle according to another embodiment variant.

[0073] The features, variants and different embodiments of the invention may be combined with each other, in various combinations, provided that they are not incompatible or mutually exclusive. In particular, variants of the invention may be imagined comprising only a selection of features described below in isolation from the other features described, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0074] Figures 1 and 2 show a head-up display system of the invention.

[0075] The head-up display system 2 comprises: - a liquid crystal display 4 (from the English Liquid Crystal Display or LCD), for example of the TFT type (according to the English acronym for “Thin-Film Transistors”, or thin-film transistors), having a controllable optical transmission 6; and - a backlighting device 8 of a vehicle 10.

[0076] The screen 4 comprises an input face 12 and an output face 14, and having, between the input face 12 and the output face 14 of the screen 4, a controllable optical transmission 6.

[0077] The liquid crystal screen 4 has dimensions between 1 and 50 inches, that is to say between 2.54 cm and 127 cm, advantageously between 10 and 30 inches, that is to say between 25.4 cm and 76.2 cm.

[0078] The head-up display system 2 further comprises a polarization recycling plate 16 configured to guide at least one polarization of the light beams 20 in a direction, as seen in [Fig. 2]. The polarization recycling plate 16 is arranged between the liquid crystal screen 4 and the backlighting device 8.

[0079] The backlighting device 8 comprises: - a matrix 18 of light sources 19, in particular a matrix of a plurality of light-emitting diodes 19, configured to emit light beams 20; and - three optical components 22 each comprising (in [Fig.2], only one optical component 22 is shown for the sake of clarity): • a light entry face 24 having a substantially hemispherical and concave cap shape with a concavity directed towards the light sources 18, this light entry face 24 being placed opposite the light sources 19; and • a side wall 26 configured to reflect the light beams 20 having entered the optical components 22 via the light entry face 24 in such a way that these reflected beams 20 are directed towards a light exit face 30 of said components; and the side wall 26 being a frustoconical surface, and this wall being flared from the light entry face 24 towards the light exit face 30.

[0080] Thanks to the arrangement of the light entry face 24, the side wall 26 and the light exit face 30 of the optical components 22, it is possible to obtain a better directivity of the light beams 20 towards a field of vision 32 of the driver 34. In particular, the fact that the side wall 26 is flared from the light entry face 24 towards the light exit face 30 makes it possible to bend the reflected beams 20 towards the light exit face 30 with better directivity.

[0081] Furthermore, it should be noted that the light output face 30 of the optical components 22 can be adapted to obtain an additional optical function, without there being an additional part. This thus makes it possible to simplify the design and assembly of the backlighting device 8.

[0082] In addition, this better directivity of the light beams 20 makes it possible to increase their brightness, at a given light power, by a factor of 2 to 6, in comparison with a conventional, non-directional backlighting device.

[0083] Furthermore, this backlighting device 8 is compatible with intelligent backlighting technology, for example “local dimming” type backlighting technology.

[0084] The matrix of light sources is placed on a printed circuit 21 (or a “printed circuit board” (PCB) according to English terminology).

[0085] The radius of curvature of the concave and substantially hemispherical cap of the light entry face 24 is between 0.1 and 10 mm, advantageously between 1 and 3 mm.

[0086] The optical components 22 are made from a single block of material, and molded from a transparent material, in particular transparent polymer, for example polymethyl methacrylate (PMMA) or polycarbonate (PC).

[0087] The matrix 18 of light sources 19 comprises the light sources 19 spaced apart with a distance p (also called a pitch p) less than or equal to 20 mm, preferably between 2 and 10 mm, more particularly between 5 and 8 mm so as to optimally cover the display surface.

[0088] Each light source 19 is configured to be controlled individually.

[0089] Thus, the backlighting device 8 is compatible with an intelligent backlighting technology, making it possible to turn on or off only some of the light sources 19, or only some of the matrices 18 of light sources 19, for example a backlighting technology of the “local dimming” type allowing a very marked color contrast between dark colors and light colors, in particular with a very deep black color.

[0090] The optical components 22 are arranged to ensure total reflection of the light beams 20 along the side wall 26 so that all the light beams 20 entering the light entry face 24 are directed towards the exit face 30 of said components. The side wall 26 is inclined relative to the light sources 18 in such a way that the light beams 20 are totally reflected towards the exit face 30. For example, the side wall 26 is inclined so that the angle of incidence of the light beams 20 relative to the normal 29 is substantially 45°. Of course, this angle of incidence can vary according to the refractive index of the material of the optical components 22.

[0091] Referring in particular to Figures 1 and 2, the backlighting device 8 further comprises: - a light diffuser 36 arranged to spread light beams 20 coming from the optical components 22, so that a field of vision 32 is visible to a driver 34 and / or to one or more passengers 38 of the vehicle 10.

[0092] It can be seen in particular in [Fig. 2] that the light diffuser 36 is arranged to spread the field of vision 32 of the light beams 20 in an elliptical manner. The term “elliptical” is understood to mean that the light beams 20 are slightly diffusing in height and largely diffusing in width. The height is defined in a direction perpendicular to the main plane of the matrix 18 of light sources 19, while the width is defined in a direction parallel to the main plane of the matrix 18 of light sources 19.

[0093] Alternatively, the light diffuser 36 is configured to spread the light beams 20 so that they are visible to the driver 34 of the vehicle 10 only. When the field of vision 32 is at a predetermined distance from the light diffuser 36, the width of the field of vision 32 is such that the field of vision 32 is visible only to the driver 34.

[0094] Alternatively, the light diffuser 36 is configured to spread the light beams 20 so that they are visible to both the driver 34 and the passenger(s) 38 of the vehicle 10. For example, when the field of vision 32 is at a predetermined distance from the light diffuser 36, the width of the field of vision 32 is such that the field of vision 32 is visible to both the driver 34 and the passenger(s) 38 of the vehicle 10.

[0095] With particular reference to [Fig. 1], the light diffuser 36 comprises a plurality of grooves 42 in the form of a prism having a symmetrical shape, which are placed opposite the output 30 of the optical components 22.

[0096] The number of grooves 42 is between 10 and 100. The grooves 42 are regularly spaced apart, with inter-groove pitches between 50 pm and 5 mm, preferably between 100 pm and 2 mm, so as to avoid the moiré effect.

[0097] The grooves 42 are inclined at an angle relative to the normal 49 of the outlet face 30, the angle advantageously being between 0 and 45°, preferably between 0 and 30°. Thus, the area of ​​visibility of the image is wider within the field of vision 32.

[0098] With particular reference to [Fig.2], the light diffuser 36 comprises a diffusion film 50 configured to spread the light beams 20 so that the latter are visible to the driver 34, and / or the passenger(s) 38 of the vehicle 10.

[0099] Thus, the diffusion film 50 makes it possible to obtain a homogeneous field of vision 32 with an overlap of light beams 20 between them, so as to obtain a homogeneous brightness over the entire field of vision 32. In other words, one avoids having an inhomogeneous field of vision 32, for example brighter in the center and less bright at the edges of the field of vision 32.

[0100] In an alternative example not shown, the light diffuser 36 may comprise both a plurality of grooves 42, in the form of prisms having a symmetrical shape and the diffusion film 50. The light diffuser 36 thus comprises a network of prisms. In a variant of the invention, the prisms may each have an asymmetrical shape.

[0101] As can be seen in particular in [Fig.2], a ratio between the height h and the diameter d is between 1 and 10, preferably between 3 and 5. The height h is defined between the light entry face 24 and the light exit face 30 of the optical component(s) 22. The diameter d is defined as the maximum distance separating the ends of the light entry face 24.

[0102] Figures 3 and 4 show a vehicle 10 comprising: - a head-up display system 2; and - a passenger compartment 60 comprising a windshield 62 provided on one of its external 64 or internal 66 faces, with a coating 70 or a mirror 70 configured to compensate for the suppression of a polarization of the light beams 20, in particular a p polarization of these light beams 20, by an object or a reflective surface located between the light beams 20 and the field of vision 32. A driver 34, or one or more passengers 38 are located behind the field of vision 32.

[0103] For example, the presence of the coating 70 or the mirror 70 makes it possible to reflect all of the light beams 20, independently of the polarization of these light beams 20.

[0104] The light beams 20 may be p-polarized (“parallel” in German), i.e. the direction of polarization of the light beams is parallel to its plane of incidence. Alternatively, the light beams may be s-polarized (“senkrecht” in German), i.e. the direction of polarization of the light beams is orthogonal to its plane of incidence. Of course, the light beams may be both p- and s-polarized.

[0105] The mirror 70 is partially reflective.

[0106] Thus, the ergonomics of the visual information perceived by the driver 34 or (the passenger(s) 38) are increased. In other words, the reflection of stray light beams that the driver 34 (or the passenger(s) 38) would perceive if the mirror 70 were entirely reflective is avoided.

[0107] The coating 70 or the mirror 70 is transparent or opaque. Thus, it is possible to modulate the light contrast of the light beams 20 in order to increase or decrease the visibility of the visual information or the image(s) perceived in the field of vision 32.

[0108] For example, the transparent coating 70 or the transparent mirror 70 is chosen when the need for brightness is greater (i.e., greater than 10000 cd / m2), while the opaque coating 70 or the opaque mirror 70 is chosen for the need for less brightness (i.e., between 500 / m2 and 1000 cd / m2).

[0109] As can be seen in particular in [Fig. 3] or 4, the position of the coating 70 or the mirror 70 on the external face 66 ([Fig. 3]) or on the internal face 64 ([Fig. 4]) of the windshield 62 of the vehicle 10 can be adapted depending on whether the coating 70 or the mirror 70 is sensitive or not to environmental conditions. For example, if the coating 70 or the mirror 70 is sensitive to humidity, the coating 70 or the mirror 70 is positioned on the internal face 66 of the windshield 62. The external face 64 is understood to mean the face located outside the passenger compartment 60 of the vehicle 10. The internal face 66 is the face opposite the external face 64, and located inside the passenger compartment 60 of the vehicle 10.

[0110] The coating 70 or the mirror 70 may be produced by the deposition of a metal, for example by the deposition of a metal comprising chromium.

Claims

Claims

1. Backlighting device (8) for a head-up display system (2), in particular of a vehicle (10), said device comprising: - at least one matrix (18) of light sources (19), in particular at least one matrix of a plurality of light-emitting diodes, configured to emit light beams (20); - at least one optical component (22) comprising: • a light entry face (24) having a concave shape of concavity directed towards the light sources (19), this light entry face (24) being placed opposite at least one of the light sources (19); and • a side wall (26) configured to reflect the light beams (20) having penetrated into the optical component (22) via the light entry face (24) in such a way that these reflected beams (20) are directed towards a light exit face (30) of said component;and the side wall (26) being flared from the light inlet face (24) towards the light outlet face (30).;

2. Backlighting device (8) according to claim 1, comprising a plurality of matrices (18) of light sources (19) configured to be controlled individually, so as to each form an individual illumination zone, this illumination zone being intended to illuminate one or more optical components (22) so as to form a plurality of light beam emission assemblies (20).

3. A backlighting device (8) according to claim 1 or 2, wherein the optical component(s) (22) are made from a single block of material.

4. A backlighting device (8) according to any preceding claim, wherein the focus of the backlighting device (8) is spaced from the center of the radius of the curvature of the light entry face (24).

5. A backlighting device (8) according to any preceding claim, further comprising a light diffuser (36) arranged to spread light beams (20) coming from the optical component(s) (22), such that a field of vision (32) is visible to a driver (34) and / or to one or more passengers (38) of the vehicle (10).

6. A backlighting device (8) according to claim 5, wherein the light diffuser (36) comprises a diffusion film (50) configured to spread the light beams (20).

7. Backlighting device (8) according to claim 5 or 6, wherein the light diffuser (36) comprises at least one groove (42), in particular in the form of a prism having a symmetrical shape, configured to spread the light beams (20).

8. Backlighting device (8) according to one of claims 5 to 7, wherein the light diffuser (36) is configured to spread the light beams (20) so that they are visible to the driver of the vehicle only.

9. Head-up display system (2), in particular of a vehicle (10), said head-up display system (2) comprising: - a screen (4) having a controllable optical transmission (6); and - a backlighting device according to one of claims 1 to 8.

10. Vehicle (10) comprising: - a head-up display system (2) according to claim 9; and - a passenger compartment (60) comprising a windshield (62) provided on one of its external (64) or internal (66) faces, with a coating (70) or a mirror (70) configured to compensate for the suppression of a polarization of the light beams (20), in particular a p polarization of these light beams (20), by an object or a reflective surface located between the light beams (20) and the field of vision (32).

Images