FR3049071A1 - SELECTIVE REFLECTIVE OPTICAL COMPONENT DISPLAY DEVICE AND OPTICAL DEFLECTION AND FOCUSING ELEMENTS FOR A VEHICLE - Google Patents

Abstract

A display device (DA) equips a vehicle and includes a source (SI) generating a real image, and an optical component (CO) producing behind its rear face (FR), a virtual image of the real image for a passenger located in front of its front (FV). This optical component (CO) comprises a first optical element (E1) inducing a deflection and a focusing of the photons passing therethrough, adapted to the production of the virtual image, a second optical element (E2) selectively reflecting towards the passenger the photons having wavelengths belonging to a wavelength band used by the source (S1) while transmitting photons of wavelengths not belonging to this band by transmission, and a third optical element (E3) inducing deflection and defocus photons therethrough, to be compensated by the first optical element (E1) during the crossing of the latter (E1).

Description

The invention relates to display devices that equip certain vehicles, generally of terrestrial type.

The term "display device" is used here to mean both "head-up-displays" and "augmented reality" type devices. These two types of display device usually include a source generating real images, and a reflective plate placed above the dashboard of the vehicle and directed towards a passenger (usually the driver). This reflective blade can be a specific element (called "combine" in English) or a part of the windshield of the vehicle. Furthermore, this reflecting plate comprises a so-called "front" face which is oriented towards the driver and a so-called "rear" face opposite to the front face. The front panel is intended to reflect the actual images, which are generated by the source, towards the eyes of the driver. Because of the respective positions of the source, the transparent blade and the eyes of the driver, the latter thus observes a virtual image of each real image which is placed at a distance from the rear face of the transparent blade. This optical illusion allows the driver to believe that the information is displayed (or projected) in front of the vehicle.

In the case of a head-up display device, the driver sees each virtual image in a narrow field, typically 6 ° by 3 °, at a distance from his eyes equal to about 180 cm, which imposes efforts of accommodation and convergence.

In the case of an augmented reality device, the driver sees each virtual image in a larger field, typically 8 ° by 10 °, at a distance from his eyes between about 15 m and infinity. The driver thus has the impression that the virtual image floats in the same plane as that of the taxiway that his vehicle is taking, which avoids him having to make efforts of accommodation and convergence, and therefore he allows driving without visual fatigue and in complete safety.

With an augmented reality device it is now difficult to obtain a magnification and a field of vision larger than those proposed without this becoming unacceptable in terms of space in a vehicle dashboard. Indeed, the increase in magnification and field of view requires the use of optical elements in "free space" (such as mirrors and lenses) intended, for example, to cause a folding of the optical path.

One could certainly imagine using augmented reality devices called indirect, that is to say, in addition to a screen on which is displayed a scene filmed with superimposed pictograms or symbols that are not in the same plane. However, the observation of what is displayed on the screen requires a driver accommodation effort that is not compatible with ergonomic driving. In addition, the placement of the screen in the field of view of the driver poses a real problem considering that this screen must offer a transmission greater than 70% over the entire visible spectrum. The invention is therefore particularly intended to improve the situation.

It proposes for this purpose a display device, intended to equip a vehicle, and comprising a source, capable of generating at least one real image, and an optical component, capable of producing, at a distance from a rear face that it includes, a virtual image (of this real image) generated for a passenger who is located opposite a front face that he understands.

This display device is characterized in that its optical component comprises in order from its front face to its rear face: a first optical element capable of inducing a deflection and a focusing of the photons which pass through it, adapted to the production of the virtual image; a second optical element that is capable of selectively reflecting photons having wavelengths belonging to at least one band of wavelengths used by the source while passing photons through transmission; having wavelengths not belonging to this band, and - a third optical element which is capable of inducing a deflection and a defocusing of the photons which pass therethrough intended to be compensated by the first optical element during the crossing of this latest.

This gives a very compact display device, small, without additional screen and in which the display field and the magnification can be chosen according to the needs by acting on the characteristics of the first and third optical elements of its optical component.

The display device according to the invention may comprise other characteristics that can be taken separately or in combination, and in particular: the first optical element may comprise a first structure defining at least one prism capable of inducing its deflection and a second structure defining at least one lens capable of inducing its focusing, and the third optical element may comprise a third structure defining at least one prism capable of inducing its deflection and a fourth structure defining at least one lens capable of inducing its defocusing, the first element optically compensating the third optical element from the point of view of focusing and deflection; the first structure can define a multiplicity of prism portions placed one after the other, the second structure can define a multiplicity of different lens portions and placed one after the other, the third structure can define a multiplicity portions of prism placed one after the other, complementary to the first structure, and the fourth structure can define a plurality of different lens portions and placed one after the other, complementary to the second structure; Each multiplicity of prism portions can define a so-called "Fresnel prism" profile, and each multiplicity of lens portions can define a Fresnel lens profile; its optical component can be oriented with respect to the source and the passenger so as to induce an "off-axis" reflection of the real image; the second optical element may comprise a set of optical thin layers (or multilayers); the second optical element may comprise an array of structures having at least one dimension less than the wavelengths of the wavelength band; structures of the network of structures can be dielectric. In this case, the second optical element may also comprise a waveguide defining with the network of structures a resonant network; alternatively, the structures of the network of structures may be metallic and capable of inducing plasmonic waves. In this case, the second optical element may also and possibly include a dielectric waveguide; the first and third optical elements may comprise resonant nanoparticles, forming so-called meta-surface surfaces; its optical component can be a part of a vehicle windshield. The invention also proposes a vehicle, possibly of automobile type, and comprising at least one display device of the type of that presented above. Other features and advantages of the invention will appear on examining the detailed description below, and the accompanying drawings, in which: - Figure 1 illustrates schematically and functionally, in a sectional view in a plane constructed to from longitudinal and vertical directions of a motor vehicle, a part of an example of the dashboard of this motor vehicle, equipped with an exemplary embodiment of a display device according to the invention, - Figure 2 schematically illustrates , in a sectional view in a plane constructed from said longitudinal and vertical directions, an optical component of a display device according to the invention; - Figure 3 schematically illustrates in sectional view in a constructed plane from said longitudinal and vertical directions, a first exemplary embodiment of a first optical element of an optical component of a device 4 illustrates schematically, in a sectional view in a plane constructed from said longitudinal and vertical directions, a first embodiment of a third optical element of an optical component. a display device according to the invention, whose action is adapted to be compensated by that of a first optical element of the type shown in FIG. 3; FIG. 5 schematically illustrates, in a view of cutting in a plane constructed from said longitudinal and vertical directions, a second exemplary embodiment of a first optical element of an optical component of a display device according to the invention, and - Figure 6 illustrates schematically, in a sectional view in a plane constructed from said longitudinal and vertical directions, a second embodiment of a third optical element of a optical component of a display device according to the invention, the action of which is adapted to be compensated by that of a first optical element of the type illustrated in FIG. 5. The object of the invention is in particular to propose a display device DA head-up type and intended to equip a vehicle.

In what follows, it is considered, by way of non-limiting example, that the vehicle is automotive type. This is for example a car, a commercial vehicle, a coach or a truck. But the invention is not limited to this type of vehicle. It concerns indeed any type of land vehicle, maritime (or fluvial), or air, able to circulate.

FIG. 1 shows schematically and functionally an exemplary embodiment of a display device DA according to the invention. In this example, the display device DA is secured to a PDB dashboard of the vehicle, located in the vicinity of the windshield PB of the latter. But this is not obligatory. Indeed, the display device DA could be partially secured to the windshield PB and partly to a vehicle equipment located under or in the PDB dashboard.

As illustrated, a display device DA according to the invention comprises at least one image source S1 and an optical component CO.

The source SI is arranged to generate at least one real image. In the nonlimiting example illustrated in FIG. 1, the source SI is permanently installed inside the PDB dashboard, in the vicinity of an opening OV which is defined in its upper face (oriented towards the passenger compartment). It will be understood that this opening OV is intended to let the light rays (or photons) representative of the real images and which are generated by the source S1, so that they can reach the optical component CO.

Among the many information that can be part of a real image generated by the source SI, there may be mentioned the current time, the speed of the vehicle, the number of kilometers since the last reset of the daily odometer, the autonomy of the vehicle in terms of fuel quantity or kilometers, location and / or navigation information (guidance, for example by satellites), a warning sign detected by vehicle observation means, a detected obstacle by means of observation of the vehicle but difficult to observe by the driver of the vehicle, ground markings detected by vehicle observation means and possibly difficult to observe by the driver of the vehicle, the maximum speed allowed on the traffic lane used , the speed selected on the speed limitation or speed control device, an che indicating a channel to double, a warning a car panel from the rear, or a message from a vehicle computer (e.g., radio volume or incoming call).

The source SI can be in any form known to those skilled in the art, and especially in the form of a segmented or matrix liquid crystal display (or LCD), or a projector (to LEDs or laser (s) or TFT or OLEDs. It must be powerful enough to provide sufficient contrast to the outside light. This source SI emits photons having wavelengths belonging to at least one wavelength band of the visible range and corresponding to the wavelength range of the photons reflected by a second optical element E2, to which reference will be made later. .

The optical component CO is placed above the upper face of the PDB dashboard, here in the vicinity of the OV opening.

It will be noted that in the example shown in non-limiting manner in FIG. 1, the optical component CO is a different element of the windshield PB. But in an alternative embodiment the optical component CO could be a selected part of the windshield PB.

When the optical component CO is a different element of the windshield PB, as illustrated, it may optionally be secured to a support which is coupled to a mechanical or electrical actuator arranged to retract it, when it is not used, in a dedicated housing of the PDB dashboard, whose access is possibly controlled by a door. This protects it from dust, light radiation and shocks.

On the other hand, when the optical component CO is a different element of the windshield PB, as illustrated, it must have a transparency greater than a threshold (for example equal to 70%). In this case, it comprises at least one support plate PS 'made of a transparent material, for example a polycarbonate (or PC), glass, PVB ("polyvinyl butyral" -poly (vinyl butyral)) or TiO2 (titanium dioxide).

Whether it is an insert or a selected part of the windshield PB, the optical component CO comprises a so-called "front" face FV which is directed towards a PA passenger of the vehicle (for example the driver ), and a face called "back" FR opposite its front face FV.

Moreover, this optical component CO is able to produce, at a distance from its rear face FR, a virtual image IV of each real image that is generated by the source S1. It will be understood that each virtual image IV is produced for the passenger PA which is located opposite the front face FV of the optical component CO.

According to the invention, and as illustrated in FIGS. 1 and 2, the optical component CO comprises, in order from its front face FV towards its rear face FR, a first optical element E1, a second optical element E2 and a third optical element E3 .

The second optical element E2 is capable of selectively reflecting toward the aforementioned passenger AP photons having wavelengths belonging to at least one wavelength band used by the source S1 (to generate its actual images), while leaving transmit photons having wavelengths that do not belong to this (reflection) band. In other words, the second optical element E2 is intended to reflect selectively towards the passenger AP at least some wavelengths corresponding to the colors of the real images which are generated by the source S1, and preferably all these colors, and to be transparent in both directions of crossing (and therefore in transmission) for all other wavelengths not belonging to each reflection band. This is particularly advantageous since it makes it possible to reflect almost completely the photons coming from the source S1 and thus to use a source SI less powerful than those which are currently used, and consequently to save in terms of energy, energy and energy. clutter and cost.

The first optical element E1 may, for example, be secured to the second optical element E2, and is capable of inducing a deflection and focusing photons that pass through adapted to the production of a virtual image IV. This bonding can, for example, be done by bonding (possibly molecular).

The distance between the PA passenger's eyes and the virtual image IV is chosen according to the needs (head-up display or augmented reality), and depends on the deflection and focusing provided by the first optical element E1.

It is important to note that the photons which define a real image generated by the source S1 first traverse the first optical element E1 in order to reach the second optical element E2, and thus undergo a first deflection and a first focusing, then after having been reflected by the second optical element E2, they cross the first optical element E1 a second time in order to (spread) towards the eyes of the passenger PA, and thus undergo a second deflection and a second focusing.

The third optical element E3 may, for example, be secured to the second optical element E2, and is capable of inducing a deflection and a defocusing of the photons which pass therethrough intended to be compensated by the first optical element E1 during the crossing of the latter. (E1).

It is important to note that the deflection and defocusing, which the photons undergo, which go from the outside of the vehicle towards the front face FV of the optical component CO, during the crossing of the third optical element E3, are chosen so to aim at a preferentially total compensation of the deflection and the focusing induced by the crossing of the first optical element E1. Therefore, the respective arrangements of the first E1 and third E3 optical elements are jointly determined so that each virtual image IV appears to be displayed at a predetermined distance from the passenger AP, and that part of each actual image observed by the passenger PA at through the optical component CO is generally neither deformed nor displaced.

Different arrangements can be chosen for the first E1 and third E3 optical elements. Some of them are described below with reference to Figures 2 to 6, by way of non-limiting examples.

In the illustrated examples, the first optical element E1 comprises first S1 and second S2 structures, and the third optical element E3 comprises third S3 and fourth S4 structures.

The first structure S1 defines at least one prism which is capable of inducing the deflection to be provided by the first optical element E1. The second structure S2 defines at least one lens that is capable of inducing the focus that the first optical element E1 must provide. For example, and as illustrated without limitation in FIGS. 2, 3 and 5, the first optical element E1 may comprise a support plate PS1 that is transparent at all the wavelengths of the visible range and that comprises a rear face solidly attached to the second element. E2 optical and a front face which is fixedly secured to the first structure S1. In this case, the second structure S2 is fixedly secured to the front face of the first structure S1.

Prism S1 allows to add a degree of freedom in the orientation and positioning of the source SI, and therefore in the positioning of each virtual image IV.

The third structure S3 defines at least one prism which is capable of inducing the deflection to be ensured by the third optical element E3. The fourth structure S4 defines at least one lens that is capable of inducing the defocusing that the third optical element E3 must provide.

For example, and as illustrated nonlimitingly in FIGS. 2, 4 and 6, the third optical element E3 may comprise a PS2 support plate that is transparent at all wavelengths of the visible range and comprises a rear face to which is fixedly secured. the third structure S3, and a front face secured to a rear face of a support plate PS 'transparent to all wavelengths of the visible range and also having a front face to which the second optical element E2 is fixedly secured; . In this case, the fourth structure S4 is fixedly secured to the rear face of the third structure S3. By way of example, the support plates PS ', PS1 and PS2 may, for example, be made of polycarbonate (or PC), glass, PVB, or TiO 2.

Different arrangements can be chosen for the first S1, second S2, third S3 and fourth S4 structures. Two of them are described below with reference to Figures 3 to 6, by way of non-limiting examples.

In the first example illustrated in FIG. 3, the first structure S1 defines a prism and the second structure S2 defines a lens.

In the first example illustrated in FIG. 4, the third structure S3 defines a prism and the fourth structure S4 defines a lens. These third S3 and fourth S4 structures are intended to cooperate with the first S1 and second S2 structures illustrated in Figure 3.

In the second example illustrated in FIG. 5, the first structure S1 defines a multiplicity of prism portions PP1j (here j = 1 to 6) placed one after the other, and the second structure S2 defines a multiplicity of portions of lens PL1j different and placed one after the other, complementary to the first structure S1.

In the second example illustrated in FIG. 6, the third structure S3 defines a multiplicity of prism portions PP2j (here j = 1 to 6) placed one after the other, and the fourth structure S4 defines a multiplicity of portions of PL2j lens different and placed one after the other, complementary to the second structure S2. By way of illustrative and therefore non-limiting example, each multiplicity of prism portions PP1j, PP2j can define a so-called Fresnel prism profile, and each multiplicity of lens portions PL1j, PL2j can define a so-called Fresnel lens profile, as illustrated in Figures 5 and 6. The Fresnel profile is advantageous because it allows in particular to have a less thick optical element (and therefore less heavy and less expensive).

It should be noted that the optical component CO may, for example, constitute a flat, micro and / or nano-structured plate and comprise resonant nanoparticles, forming a so-called meta-surface, and making it possible to ensure not only its selective reflection function. wavelength but also deflection / focusing.

As a variant, the first optical element E1 may, for example, be flat, micro and / or nano-structured and comprise resonant nanoparticles, forming a so-called meta-surface, and making it possible to perform its deflection and focusing functions.

Also as a variant, the third optical element E3 may, for example, be flat, micro and / or nano-structured and comprise resonant nanoparticles, forming a so-called meta-surface, and making it possible to perform its deflection and defocusing functions. .

Also for example, the first S1 and third S3 structures may define flat, micro and / or nano-structured prisms and having resonant nanoparticles, forming so-called meta-surface surfaces, instead of defining Fresnel prisms.

Also for example, the second S2 and fourth S4 structures may define flat, micro and / or nano-structured lenses and having resonant nanoparticles, forming so-called meta-surface surfaces, instead of defining Fresnel lenses.

It will also be noted, as illustrated without limitation in FIG. 1, that if the application requires it, the orientation of the optical component CO with respect to the source S1 and the passenger PA may be arbitrary (especially off-axis). The deflection elements integrated into the first optical element E1 have the role of directing to the passenger AP the rays coming from the virtual image IV.

Different arrangements can be chosen for the second optical element E2. One of them is described below, by way of non-limiting example.

In this example, the second optical element E2 comprises an array of structures having at least one dimension less than the wavelengths of the reflection band, and thus called "sub-wavelength". Note that these structures may optionally have a substructure of structures in two directions and having at least one dimension less than the wavelengths of the reflection band. By way of example, at least one of their dimensions can be between about ten nanometers and a few hundred nanometers.

Such structures offer macroscopic reflection properties, specular or not, and centered on one or more bands of visible wavelengths used for display.

For example, these subwavelength structures of the network of structures may be dielectric. Thus, they may, for example, be made of glass, in T1O2, in Nb20s, or in S13N4, with a refractive index ranging from 1 to 3. In this case, the second optical element E2 may also comprise a waveguide defining with the network of structures a resonant network.

For a certain incident wave, coming from the source SI and having an angle of incidence a, a wavelength and a polarization defined, there is a diffraction order of the resonant network which excites a specific mode of the network of sub-structures. wave length. This results in a peak in reflection or transmission of the incident light. The corresponding spectral width can be configured by varying the depth of the subwavelength structure network, the difference between the refractive indices of the materials, and the harmonic of the structure network corresponding to the diffraction order used. , or on the field of the eigen mode excited in the network of structures. When a single eigenmode is excited, typically in oblique incidence, the angular width varies as the spectral width.

It will be noted that such a resonant network may possibly be periodic. It can be defined by electronic lithography (or nano-printing (or "nano-imprint")) and etching. Alternatively, it can be defined by a method of self-organization of particles in a polymer.

In a variant, the sub-wavelength structures of the network of structures may be metallic and capable of inducing plasmonic waves. Thus, they may, for example, be nanoparticles of gold, silver, copper or aluminum, and may be in the form of son, spheres, or cylinders elliptical base. In this case, the second optical element E2 can also and possibly include a dielectric waveguide.

When the network of structures is excited by a light wave whose wavelength depends on the geometric characteristics of its metal nanoparticles (form factor, length, volume), refractive indices of the surrounding environments and the material chosen for the metal nanoparticles , plasmonic resonances are created. Circular-based spherical or cylindrical nanoparticles have the same resonance wavelength regardless of the polarization, while metallic wires offer resonance only for a given polarization. Moreover, nanoparticles of ellipsoidal shape, or any other anisotropic form, have a different resonant wavelength depending on the direction of polarization of the incident light. Outside the resonance wavelength, the network of metal nanoparticles interacts much less with the incident light, which allows it to remain globally transparent.

It will be noted that such a plasmonic network may be possibly periodic. It can be defined by electronic lithography (or nano-printing (or "nano-imprint")), filing and "lift-off". Alternatively, it can be defined by a method of self-organization of particles in a polymer.

In an alternative embodiment, the second optical element E2 could comprise a set of thin optical layers (or multilayers).

The small thickness of the various constituents of the optical component CO makes it possible to limit the deformation of the images passing through the display device DA (and thus induces a very weak effect of magnification). Moreover, this small thickness makes it possible to operate in direct augmented reality with a gain in compactness.

In addition, when the optical component CO is a different element of the windshield PB, it can be advantageously manufactured in large quantities, which reduces the cost of the display devices.

Claims (10)

A display device (DA) for a vehicle, said device (DA) comprising a source (S1) capable of generating at least one real image, and an optical component (CO) capable of producing, at a distance from a rear face (FR) that it comprises, a virtual image of said real image generated for a passenger located opposite a front face (FV) that it comprises, characterized in that said optical component (CO) comprises by order from said front face (FV) to said rear face (FR) i) a first optical element (E1) capable of inducing a deflection and a focusing of the photons which pass therethrough, adapted to the production of said virtual image, ii) a second optical element (E2) able to reflect selectively towards said passenger photons having wavelengths belonging to at least one wavelength band used by said source (SI) while allowing photons having lengths to pass through by transmission of wave not belonging to said band, and iii) a third optical element (E3) capable of inducing a deflection and defocusing of the photons which pass therethrough intended to be compensated by said first optical element (E1) during the crossing of this last (E1). 2. Device according to claim 1, characterized in that said first optical element (E1) comprises a first structure (S1) defining at least one prism adapted to induce its deflection and a second structure (S2) defining at least one lens specific to inducing its focusing, and said third optical element (E3) comprises a third structure (S3) defining at least one prism capable of inducing its deflection and a fourth structure (S4) defining at least one lens capable of inducing its defocusing, said first element optical device (E1) compensating for said third optical element (E3) from the point of view of focusing and deflection. 3. Device according to claim 2, characterized in that said first structure (S1) defines a multiplicity of prism portions placed one after the other, said second structure (S2) defines a plurality of different lens portions and placed one after the other, complementary to said first structure (S1), said third structure (S3) defines a multiplicity of prism portions placed one after the other, and said fourth structure (S4) defines a multiplicity of different lens portions and placed one after the other complementary to said second structure (S2). 4. Device according to one of claims 1 to 3, characterized in that said optical component (CO) is oriented relative to said source (SI) and said passenger (PA) so as to induce a so-called "off" type reflection. axis "of said real image. 5. Device according to one of claims 1 to 4, characterized in that said second optical element (E2) comprises a set of thin optical layers. 6. Device according to one of claims 1 to 4, characterized in that said second optical element (E2) comprises an array of structures having at least one dimension less than the wavelengths of said band. 7. Device according to claim 6, characterized in that said structures of the network of structures are dielectric, and in that said second optical element (E2) also comprises a waveguide defining with said network of structures a resonant network. 8. Device according to claim 6, characterized in that said structures of the network of structures are metallic and adapted to induce plasmonic waves. 9. Device according to one of claims 1 to 8, characterized in that said optical component (CO) is a part of a windshield (PB) vehicle. 10. Vehicle, characterized in that it comprises at least one display device (DA) according to one of the preceding claims.