Spatial light modulator for holographic image projection device

Abstract

The present invention relates to a spatial light modulator (32) intended to be illuminated by coherent light sources to project a holographic image, said spatial light modulator (32) comprising: - a substrate (321) on which at least one waveguide array is formed; - an encapsulating layer (323) placed on said substrate and enveloping said waveguides; and - a plurality of nanoresonators placed on the encapsulating layer directly above at least one intersection of two waveguides (322) of said at least one waveguide array, each nanoresonator (324) being optically activatable and being formed of two nanoparticle chains, each nanoparticle chain being aligned along a longitudinal direction of one of the two waveguides, each nanoresonator defining a pixel of said holographic image. Figure for the abstract: Figure 6

Description

Title of the invention: Spatial light modulator for holographic image projection device technical field

[0001] The present invention is in the general field of dynamic holography, applicable to holographic image projection devices such as 3D displays or augmented reality systems embedded in vehicles, in particular autonomous vehicles. Technological background

[0002] Holography is a method for reconstructing a 3D (three-dimensional) image based on interference patterns (commonly called holograms) and diffraction phenomena to reconstruct in 3D a wavefront emitted from an object towards an observer. The use of holography for the reconstruction and visualization of 3D images is a viable solution because it does not cause headaches or other discomfort that can be caused by other 3D technologies.

[0003] Augmented reality, or AR, which is increasingly found in the automotive field, is a technological evolution of Head-Up Display (HUD) systems. Essentially, an HUD system comprises a Picture Generation Unit (PGU) that generates an image. The HUD system also includes an optical system made up of several mirrors, possibly adjustable, and adapted so that an observer sees the image in an area located beyond the windshield at a projection distance (approximately 2 meters in front of the driver) and at a certain angle α relative to the horizontal. An HUD system can display, for example, speed information, pictograms, or vehicle information in the driver's field of vision while the vehicle is being driven.

[0004] Augmented reality in the automotive field takes the form of one or more virtual images projected at a distance of approximately 7 meters in front of the windshield (or even more). Virtual reality images can be superimposed on images from a VTH system to, for example, highlight road features, virtually illuminate a GPS track, etc. Figure 1 illustrates an example of superimposing an image from a VTH system (part 1) with an image from an AR system (part 2).

[0005] Current AR systems adapted for the automotive field are based on the integration of several image generation units (or a single unit divided into two) and two optical paths implemented by refractive optics mirrors: one for the propagation of an image from a VTH system and the other for the propagation of an image from an AR system.

[0006] The main drawback of current systems is their size: AR systems based entirely on conventional optics have minimum volumes approaching 20 liters, while VTH systems have a volume of around 5 liters. Current VTH and AR systems are difficult to integrate without reducing their size.

[0007] 3D displays for the automotive sector are a trend in the vehicles of the future, both for integration into the cockpit (instrument cluster, central screen) and for integration as a conversational assistant. Human-Machine Interfaces would then be more intuitive because interaction with 3D interfaces is more intuitive compared to interaction with conventional 2D interfaces.

[0008] Existing 3D displays are based on autostereoscopy (with or without eye tracking) which produces a different image for the left and right eye of an observer or include multilayer displays which are equipped with several LCD panels to produce several image planes at different depths.

[0009] Autostereoscopic 3D displays suffer from conflict "Vergence / accommodation" means that the observer focuses on the screen, but the 3D content pops out in front of it. The 3D experience can be degraded or even "rejected" by the observer. As for multi-layered systems, they only allow display on several discrete planes in depth or pop-out.

[0010] Spatial light modulators, commonly called SLMs (from the English "Spatial Light Modulator"), can also be used as a holographic image display for an AR system or as a 3D display.

[0011] The modulation mechanism of a spatial light modulator relies on a method that modifies the properties of the modulation material and the way in which the spatial field of an incident light beam is modified. Various processes, including mechanical, electro-optical, thermo-optical, and magneto-optical effects, can be used to modify the properties of the modulation material of a spatial light modulator that interacts with incident light and transforms its spatial field distribution. One of the most commonly used modulation mechanisms today is the electro-optical spatial light modulator containing liquid crystals as the modulation material (LC-SLM). These LC-SLM modulators are based on a liquid crystal pixel array which, through modulation of The phase of coherent light generates a hologram at any given moment to produce 2D or 3D video at the output of an optical system. Current silicon / liquid crystal technologies for this type of modulator now allow for pixel sizes of 1 to 4 µm and image resolutions up to 4160 x 2464 pixels.

[0012] State-of-the-art AR systems that use spatial light modulators do not have sufficient resolution to allow the democratization of "dynamic" holography, i.e., holography controlled by a control unit, particularly in the automotive field.

[0013] Indeed, on the one hand, the field of view of a holographic image, due to the diffraction angle of the hologram, is linked to the size of a modulator pixel, and the number and size of pixels play a role in the resolution of the holographic image. Furthermore, the product of the image size and the field of view is proportional to the number of pixels in the modulator. Thus, to obtain a hologram of 1012 pixels, which would allow for a satisfactory resolution of a holographic image, a field of view of 60° and an image size of 50 cm are necessary. However, current modulators only allow fields of view of approximately 20°, which results in insufficient resolution of the holographic images.

[0014] It is necessary to provide spatial light modulators that provide high-resolution holographic images and fields of view beyond those currently produced by spatial light modulators. Summary of the present invention

[0015] An object of the present invention is to increase the resolution of spatial light modulators.

[0016] Another object of the present invention is to improve holographic image projection devices.

[0017] According to a first aspect, the present invention relates to a spatial light modulator intended to be illuminated by coherent light sources to project a holographic image, said spatial light modulator comprising: - a substrate on which at least one array of waveguides is formed; - a coating layer placed on said substrate and enveloping said waveguides; and - a plurality of nanoresonators placed on the coating layer directly above at least one intersection of two waveguides of one of said at least one waveguide lattice, each nanoresonator being optically activatable and being formed of two nanoparticle chains, each nanoparticle chain being aligned along a longitudinal direction of one of the two waveguides, each nanoresonator (324) defining a pixel of said holographic image.

[0018] Placing a plurality of optically activatable nanoresonators on the coating layer significantly increases the number of nanoresonators per waveguide intersection of the waveguide lattice. Since each nanoresonator can be optically activated independently of the others, each nanoresonator can correspond to a pixel of the holographic image. Thus, increasing the number of nanoresonators in the spatial light modulator increases the number of pixels and therefore the resolution of the projected holographic image without increasing the size of the optical component of a holographic image projection device such as an AR or VTH system or a 3D display.

[0019] On the other hand, integrating such a spatial light modulator into a current AR system makes it possible to improve the resolution of the projected holographic images without the need for additional refractive optical elements. Their integration can also lead to a reduction in the size of the optical component of such a system because the space required for enlarging the projected image is less.

[0020] Moreover, the use of holographic technology for the 3D image display provides greater comfort for observation compared to other 3D technologies.

[0021] Thus, the present invention makes it possible to obtain spatial light modulators having pixel sizes smaller than 500nm, whereas the pixel size of current spatial modulators is on the order of 1 to 4 pm.

[0022] According to a variant of the spatial light modulator, a chain of nanoparticles is composed of a phase-change material deposited between two layers of a plasmonic material.

[0023] According to one variant of the spatial light modulator, the plasmonic material is gold or silver.

[0024] According to an additional variant of the spatial light modulator, the phase-change material is Vanadium Dioxide (VO2), a germanium-antimony-tellurium alloy (GeSbTe) or Antimony Trisulfide (SbS3).

[0025] According to a variant of the spatial light modulator, each nanoresonator is optically activated from light waves of wavelengths equal to activation wavelength values ​​from a set of activation wavelengths.

[0026] Nanoresonators placed directly above the same intersection and having nanoparticle chains of different lengths are then activated independently when light waves passing through the intersection have wavelengths equal to the lengths of the nanoparticle chains of these nanoresonators.

[0027] According to another variant of the spatial light modulator, the coating layer is composed of hydrogenosilsesquioxanes (HSQ).

[0028] Such a material has an optical index close to that of the substrate.

[0029] According to a second aspect, the present invention relates to a method for generating a holographic image implemented by a spatial light modulator according to the first aspect of the present invention, said method comprising the following steps for activating a nanoresonator of the spatial light modulator defining a pixel of a holographic image, said nanoresonator being placed directly above an intersection of a first waveguide and a second waveguide of the waveguide lattice of the spatial light modulator; - reception of initial data representative of a first activation wavelength of a first chain of nanoparticles of the nanoresonator and of a second activation wavelength of a second chain of nanoparticles of the nanoresonator; - emission of a first light wave with a wavelength equal to the first activation wavelength by a coherent light source associated with the first waveguide, said first light wave propagating along a longitudinal direction of the first waveguide to activate the first chain of nanoparticles of the nanoresonator aligned along the longitudinal direction of the first waveguide (322); and - emission (55) of a second light wave of wavelength equal to the second activation wavelength by a coherent light source associated with the second waveguide (3222), said second light wave propagating along a longitudinal direction of the second waveguide to activate the second chain of nanoparticles (324b) of the nanoresonator (324) aligned along the longitudinal direction of the second waveguide (322).

[0030] Pixel addressing is thus achieved by the nanoparticle chains. Each pixel of the image corresponds to a nanoresonator which can be optically activated by the propagation of light waves of specific wavelengths.

[0031] The image resolution is improved by increasing the density of nanoresonators, this increase in density being obtained by placing several nanoresonators on the same intersection thanks to the coating layer and by independent activation via a light wave of determined wavelength for each chain of nanoparticles of each nanoresonator.

[0032] According to a third aspect, the present invention relates to a holographic image projection device comprising at least one spatial light modulator according to the first aspect of the present invention.

[0033] According to one variant, the device further comprises means for implementing a method according to the second aspect of the present invention.

[0034] According to a fourth aspect, the present invention relates to a vehicle comprising at least one holographic image projection device according to the third aspect of the present invention. Brief description of the figures

[0035] Other features and advantages of the present invention will become apparent from the description of the specific and non-limiting embodiments of the present invention below, with reference to the attached Figures 1 to 10, in which:

[0036] [Fig-1] schematically illustrates the projection of images by an augmented reality system and a Head Up system of a vehicle, according to the prior art;

[0037] [Fig.2] schematically illustrates the projection of images in a vehicle 10, according to a particular and non-limiting embodiment of the present invention;

[0038] [Fig.3] schematically illustrates the field of vision associated with a driving position of the vehicle 10, according to a particular and non-limiting embodiment of the present invention;

[0039] [Fig.4] schematically illustrates a holographic image projection device for a vehicle 10, according to a particular and non-limiting embodiment of the present invention.

[0040] [Fig.5] schematically illustrates a control unit configured to provide the information necessary for the generation of one or more holographic images to a spatial light modulator, according to a particular and non-limiting embodiment of the present invention;

[0041] [Fig.6] schematically illustrates a cross-sectional view of a spatial light modulator according to a particular and non-limiting embodiment of the present invention;

[0042] [Fig.7] schematically illustrates a cross-sectional view of a nanoresonator of a spatial light modulator according to a particular and non-limiting embodiment of the present invention;

[0043] [Fig.8] schematically illustrates a spatial light modulator according to a particular and non-limiting embodiment of the present invention;

[0044] [Fig.9] schematically illustrates the addressing of pixels of a holographic image by the spatial light modulator of [Fig.8] according to a particular and non-limiting embodiment of the present invention; and

[0045] [Fig. 10] illustrates a flowchart of the different stages of a process for generating a holographic image, according to a particular embodiment of the present invention. Description of examples of achievements

[0046] A spatial light modulator, a method and device for generating a holographic image will now be described in what follows with joint reference to Figures 1 to 10. The same elements are identified with the same reference signs throughout the description that follows.

[0047] The terms "first," "second" (or "firsts," "seconds"), etc., are used in this document by arbitrary convention to allow for the identification and distinction of different elements (such as operations, means, etc.) implemented in the embodiments described below. Such elements may be distinct or correspond to a single element, depending on the embodiment.

[0048] According to a particular and non-limiting embodiment, the present invention relates to a very high resolution spatial light modulator which, once illuminated by coherent light sources (laser), can be integrated as a 3D holographic screen for a 3D display application or inserted into an augmented reality system, known as an AR system, for example for the automotive industry.

[0049] The spatial light modulator comprises: - a substrate on which at least one waveguide lattice is formed; - a coating layer placed on said substrate and enveloping said waveguides; and - a plurality of nanoresonators placed on the coating layer directly above at least one intersection of two waveguides of said at least one waveguide lattice, each nanoresonator being optically activatable and being formed of two nanoparticle chains, each nanoparticle chain being aligned along a longitudinal direction of one of the two waveguides, each nanoresonator defining a pixel of said holographic image.

[0050] Each of the nanoresonators then defines a pixel of the holographic image.

[0051] Fig. 2 schematically illustrates the projection of images in a vehicle 10, according to a particular and non-limiting embodiment of the present invention.

[0052] Fig. 2 presents a view of the interior of a vehicle 10, in particular of the front part of the passenger compartment of the vehicle 10 including in particular the steering wheel, the dashboard, and the windscreen 100 of the vehicle 10.

[0053] Vehicle 10 corresponds, for example, to a vehicle with an internal combustion engine, with electric motor(s), or even a hybrid vehicle with an internal combustion engine and one or more electric motors. Vehicle 1 thus corresponds, for example, to a land vehicle, for example a car, a truck, a bus.

[0054] The vehicle 10 carries, for example, a set of sensors configured to obtain data on the environment of the vehicle 10, this data, or part thereof, being used in particular for the autonomous driving of the vehicle 10. This sensor or these sensors correspond, for example, to sensors of one or more object detection systems in the environment of the vehicle 10, the data obtained from this sensor or these sensors making it possible, for example, to detect objects in the environment of the vehicle 10, for example in front of the vehicle 10. This sensor or these sensors Object detection systems are, for example, associated with or included in one or more driver assistance systems, known as ADAS (Advanced Driver-Assistance System).

[0055] The sensor(s) associated with these object detection systems correspond, for example, to one or more of the following sensors: - one or more millimeter-wave radars arranged on the vehicle 10, for example at the front, at the rear, on each front / rear corner of the vehicle; each radar is adapted to emit electromagnetic waves and to receive the echoes of these waves reflected by one or more objects, in order to detect obstacles and their distances from the vehicle; and / or - one or more LIDAR(s) (Light Detection and Ranging), a LIDAR sensor corresponding to an optoelectronic system composed of a laser emitter, a receiver including a light collector (to collect the portion of the light emitted by the emitter and reflected by any object located in the path of the light rays emitted by the emitter) and a photodetector that transforms the collected light into an electrical signal; a LIDAR sensor thus makes it possible to detect the presence of objects located in the emitted light beam and to measure the distance between the sensor and each detected object; and / or - one or more cameras (with or without a depth sensor) for acquiring one or more images of the environment around the vehicle within the field of vision of the camera(s).

[0056] The vehicle 10 also carries, for example, a navigation system, which uses, for example, geolocation information provided by a satellite positioning system such as the GPS (Global Positioning System) or the Galileo system. This geolocation information is combined with mapping data, particularly road data, to display the route on a map obtained from the mapping data.

[0057] Vehicle 10 advantageously incorporates a holographic image projection device.

[0058] The holographic image projection device includes, for example, one or more projectors integrated, for example, into the dashboard. Such a holographic image or graphic content projection device corresponds, for example, to a 3D display or an AR or VTH system, which allows virtual objects to be superimposed into the field of vision of a driver of vehicle 10, for example, onto the windshield 100 of vehicle 10, so as to overlay the virtual objects onto the real road scene. The projection of the holographic image is, for example, controlled by one or more computers of the vehicle's embedded system 10, for example by the computer of the infotainment system, called the IVI computer (from the English "In-Vehicle Infotainment" or in French "Info-divertissement étoilé") of the vehicle 10.

[0059] The holographic image is advantageously displayed on a surface 101 by projecting the image data in the form of a light beam emitted by a spatial light modulator 32. The surface 101 corresponds, for example, to an opaque strip arranged on the dashboard of the vehicle 10, for example above and behind the steering wheel with respect to a viewpoint corresponding to the viewpoint from which the driver of the vehicle 10 is supposed to look at the road ahead when driving the vehicle 10.

[0060] The holographic image advantageously comprises a set of graphic objects, each representing a parameter or operating state of the vehicle 10. By way of example, the set of graphic objects represents parameters or operating states of the vehicle 10 corresponding to all or part of the following information, according to all possible combinations: - information representative of instantaneous speed; and / or - information representing the rotation of a drive shaft (also called tachometer information); and / or - information representing a distance traveled; and / or - information representing a fuel level or the battery charge level in the case of an electric vehicle; and / or - information representative of the temperature of an engine coolant; and / or - at least one piece of information representative of a warning indicator (for example, battery charge indicator, engine oil pressure indicator, engine oil or coolant temperature indicator, brake failure indicator, etc.), corresponding, for example, to a pictogram that appears or changes color in the event of a warning; and / or - at least one piece of information representative of a warning indicator (for example, engine oil level indicator, airbag indicator (also called inflatable cushion), brake pad wear indicator, etc.), corresponding for example to a pictogram that appears or changes color when a warning is given; and / or - at least one piece of information representative of an indicator for the operation of an on-board system (positioning light indicator, dipped or main beam indicator, hazard warning light indicator, rear window defogger indicator, etc.), corresponding for example to a pictogram that appears or changes color when the on-board system is activated.

[0061] The set of graphic objects can also represent contextual or environmental information of the vehicle 10, corresponding to all or part of the following information, according to all possible combinations: - representative mapping information of the environment of vehicle 10, for example obtained from a navigation system embedded in the vehicle or from a navigation system installed on a mobile communication device (for example a smartphone connected wirelessly to vehicle 10, or more specifically to the vehicle's embedded system 10 including the computer(s) responsible for controlling the projection of the first and second images; and / or - representative vehicle navigation information, for example a route to be followed by the vehicle, the vehicle's current position, the vehicle's instantaneous speed, the speed limit applicable to the section of road on which the vehicle is traveling 10; this information is obtained, for example, from the vehicle's on-board navigation system or from the navigation system installed on a mobile communication device; and / or - information representative of an object detected in the environment, for example the presence of a vehicle preceding vehicle 10, the presence of a pedestrian or an animal on the road in front of vehicle 10, the presence of a road sign, the presence of a stationary object on the road, the presence of a tunnel entrance, etc.; this information is obtained, for example, from one or more object detection sensors on board the vehicle 10 and, for example, associated with one or more AD AS systems of the vehicle 10; according to a variant, this information is received from another vehicle or from the infrastructure connected to the vehicle 10 in wireless communication according to a vehicle-to-everything (V2X) communication mode comprising vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I) and / or vehicle-to-pedestrian (V2P) communication modes; and / or . - information representative of an event detected in the environment, for example, information about a disruption on the road, such as an accident, a traffic jam, or information about specific weather conditions that may disrupt traffic (snow, fog, rain, ice); this information is obtained, for example, from one or more object detection sensors on board vehicle 10 and, for example, associated with one or more ADAS systems of vehicle 10; according to one variant, this information is received from another vehicle or from the infrastructure connected to vehicle 10 via wireless communication using a vehicle-to-everything (V2X) communication mode comprising communication modes vehicle to vehicle V2V, vehicle to infrastructure V2I and / or vehicle to pedestrian V2P; according to another variant, this information is received from one or more servers in the "cloud" (or "nuage" in French) via a 4G or 5G type cellular wireless network.

[0062] Of course, the list of information displayed via the holographic image is given by way of example and is not limited to the examples above.

[0063] Fig. 3 schematically illustrates a field of vision associated with a driving position of the vehicle 10, according to a particular and non-limiting embodiment of the present invention.

[0064] Figure 3 illustrates the front part of the vehicle 10 from a top view. The field of vision 210 is associated with a viewpoint 21 which corresponds to the viewpoint from which a driver is supposed to look at the road ahead when driving the vehicle 10. This viewpoint 21 is, for example, positioned in the middle of the driver's seat (front left in the direction of travel of the vehicle 10 according to the particular example in Figure 3), at the location of the driver's head if the driver is seated in the driver's seat. The viewpoint 21 is, for example, positioned in the center of a headrest resting on the driver's seat when the seat is equipped with such a headrest.

[0065] The field of vision 210 extends for example around a main vision axis 211, and covers an area between an upper vertical limit (forming for example an angle of 15° with the axis 211 from the viewpoint 21), a lower vertical limit (forming for example an angle of 15° with the axis 211 from the viewpoint 21), a right lateral limit (forming for example an angle of 20 or 25° with the axis 211 from the viewpoint 21) and a left lateral limit (forming for example an angle of 25 or 30° with the axis 211 from the viewpoint 21).

[0066] A graphic object 2100 corresponding to an element of the holographic image is advantageously projected or displayed within the field of vision 210, to ensure that the driver is looking at the road or the environment in front of the vehicle 10 according to this field of vision 210.

[0067] The graphic object 2100 depends, for example, on the type of information projected onto the surface 101. The graphic object 2100 corresponds, for example, to a representation of a warning sign, a vehicle (e.g., a car), a pedestrian, or an arrow indicating the direction to follow. The graphic object 2100 is, for example, semi-transparent to allow the driver to see the road environment through it.

[0068] When the purpose of projecting the holographic image is to alert the driver of vehicle 10 to a potential danger, the graphic object is, for example, displayed at the location of an object detected in front of vehicle 10, to attract the driver's attention. conductor on this detected object. The graphic object 2100 corresponds to a virtual element added by overlaying or superimposing this virtual element onto an element of the real world.

[0069] The movement of the graphic object 2100 follows, for example, the movement of an object detected in front of the vehicle 10, the movement of the detected object corresponding, for example, to the displacement of the detected object, if applicable, relative to the displacement of the vehicle 10. According to a variant, the graphic object 2100 is initially displayed in a first position before following the movement of the detected object.

[0070] Figure 4 schematically illustrates a holo image projection device. graphic for a vehicle 10, according to a particular and non-limiting embodiment of the present invention.

[0071] The holographic image projection device 3 includes a control unit 31 configured for processing data received from sensors of the vehicle 10 and / or systems embedded in the vehicle 10 and / or remote devices connected to the vehicle 10. The control unit 31 is advantageously configured to provide information necessary for the generation of one or more holographic images from the received data.

[0072] The holographic image projection device 3 includes a spatial light modulator 32 ([Fig.6]) configured to generate a light beam representative of a holographic image from information from the control unit 31.

[0073] The holographic image projection device 3 includes at least one coherent light source (for example laser) 34 formed, for example, of an RGB laser diode (from the English "Red, Green, Blue", in French Rouge, Vert Bleu).

[0074] According to a particular and non-limiting embodiment, the coherent light sources are adapted to emit near-infrared light waves (700nm to 1000nm).

[0075] The holographic image projection device 3 also includes a reflective device 33 associated with the spatial light modulator 32. The reflective device 33 is configured to direct the light beam emitted by the spatial light modulator 32 towards the surface 101 for displaying the holographic image in the field of vision from the viewpoint 21.

[0076] According to one variant, the holographic image projection device 3 does not include such reflective device(s), the spatial light modulator 32 then being arranged to project the light beam directly onto the surface 101.

[0077] According to an optional embodiment, the holographic image projection device 3 further comprises optical means (for example an arrangement of optical lenses not shown) configured to focus the holographic image in the image plane.

[0078] The holographic image projection device 3 is configured for example to carry out the operations described opposite Figures 6, 7, 8 and 9 and / or the steps of the process described opposite [Fig. 10].

[0079] Fig. 5 schematically illustrates a control unit 31 configured to provide information necessary for the generation of one or more holographic images to the spatial light modulator 32, according to a particular and non-limiting embodiment of the present invention.

[0080] The control unit 31 corresponds for example to a device embedded in the vehicle 10, for example a computer.

[0081] The control unit 31 is, for example, configured to carry out all or part of the operations described with reference to Figures 6, 7, 8, and 9 and / or the steps of the process described with reference to [Fig. 10]. Examples of such a control unit 31 include, but are not limited to, embedded electronic equipment such as a vehicle's on-board computer, or an electronic control unit such as an ECU (Electronic Control Unit). The elements of the control unit 31, individually or in combination, may be integrated into a single integrated circuit, into several integrated circuits, and / or into discrete components. The control unit 31 may be implemented in the form of electronic circuits or software (or computer) modules, or a combination of electronic circuits and software modules.

[0082] The control unit 31 comprises one (or more) processor(s) 40 configured to execute instructions for carrying out the steps of the process and / or for executing instructions from the software embedded in the control unit 31. The processor 40 may include integrated memory, an input / output interface, and various circuits known to those skilled in the art. The control unit 31 further comprises at least one memory 41, for example, volatile and / or non-volatile memory, and / or includes a memory storage device that may include volatile and / or non-volatile memory, such as EEPROM, ROM, PROM, RAM, DRAM, SRAM, flash, magnetic disk, or optical disk.

[0083] The computer code of the embedded software(s), including the instructions to be loaded and executed by the processor, is for example stored on memory 4L

[0084] According to various particular embodiments, the control unit 31 is coupled in communication with other similar devices or systems and / or with communication devices, for example a TCU (Telematic Control Unit), for example via a communication bus or through dedicated input / output ports.

[0085] According to a particular and non-limiting embodiment, Control Unit 31 includes a block 42 of interface elements for communicating with external devices, such as a remote server or the cloud, and other nodes in the ad hoc network. The interface elements in block 42 include one or more of the following interfaces: - RF radio frequency interface, for example of type Bluetooth® or Wi-Fi®, LTE (from the English "Long-Term Evolution" or in French "Evolution à long terme"), LTE-Advanced (or in French LTE-avancé); - USB interface (from the English "Universal Serial Bus" or "Universal Serial Bus" in French); - HDMI interface (from the English "High Definition Multimedia Interface", or "High Definition Multimedia Interface" in French); - LIN interface (from the English "Local Interconnect Network", or in French "Réseau interconnecté local").

[0086] According to another particular embodiment, the control unit 31 includes a communication interface 43 which allows communication to be established with other devices (such as other computers of the embedded system) via a communication channel 430. The communication interface 43 corresponds, for example, to a transmitter configured to transmit and receive information and / or data via the communication channel 430. The communication interface 43 corresponds, for example, to a wired network of the CAN (Controller Area Network) type, CAN FD (Controller Area Network Flexible Data-Rate) type, FlexRay (standardized by ISO 17458) or Ethernet (standardized by ISO / IEC 802-3).

[0087] According to a further particular embodiment, the control unit 31 can provide output signals to one or more external devices, such as a display screen 440, one or more loudspeakers 450 and / or other peripherals 460 (for example the spatial light modulator 32) via output interfaces 44, 45 and 46 respectively. According to a variant, one or more of the external devices is integrated into the control unit 31.

[0088] Figure 6 schematically illustrates a cross-sectional view of the spatial light modulator 32 according to a particular, non-limiting embodiment of the present invention.

[0089] The spatial light modulator 32 is intended to be illuminated by coherent light sources 34 to project a holographic image. These coherent light sources 34 are controlled (activated / deactivated) by information from the control unit 31 to generate and project a holographic image. The holographic image corresponds to a set of pixels very often organized in the form of lattice, with each pixel associated with information, for example grey levels coded on 8, 10 or 12 bits for each colour channel of a given colour space, for example RGB.

[0090] The holographic image is for example generated to graphically represent information on the operating state of the vehicle 10 or on the context or environment in which the vehicle 10 is operating. This information is for example received from sensors and / or systems embedded in the vehicle and measuring control parameters of the vehicle 10.

[0091] The holographic image from the spatial light modulator 32 is projected in the form of a light beam onto the surface 101 by the reflecting device 33 ( [Fig.4]).

[0092] Of course, the generation and projection are not limited to a single image but extend to the generation and projection of a sequence of images, for example at an image frequency equal to, for example, 24, 30 or 60 images per second.

[0093] The spatial light modulator 32 comprises a substrate 321, for example in silica (S;O2), on which is formed at least one lattice of waveguides 322.

[0094] By waveguide lattice 322, it is necessary to understand an assembly of waveguides arranged to form at least one intersection between two waveguides 322.

[0095] For example, the width of each waveguide 322 is on the order of 500 nm and the spacing between the waveguides is on the order of 500 nm, or even 300 nm, i.e. a distance dl corresponding to a center distance of the guides between 800 nm and 1 pm.

[0096] According to a particular and non-limiting embodiment, the waveguides are formed from silicon (Si) or Silicon Nitride (Si3N4).

[0097] According to a particular non-limiting embodiment, the waveguides of a lattice are structured to form a geometric pattern.

[0098] According to a particular embodiment, a waveguide lattice forms a triangular or hexagonal waveguide pattern.

[0099] The spatial light modulator 32 also includes a coating layer 323 placed on the substrate 321 and enveloping the waveguides 322.

[0100] According to a particular, non-limiting embodiment, this coating layer 323 is composed of hydrogen silsesquioxanes (HSQ). This resin, once annealed, makes it possible to obtain a material whose optical index is very close to that of the substrate 321.

[0101] The spatial light modulator 32 also includes nanoresonators 324 which are positioned above at least one intersection of two waveguides 322 of a waveguide lattice, each nanoresonator 324 being optically activatable and being formed of two chains of nanoparticles 324a, 324b ([Fig. 9]), each chain of nanoparticles 324a, 324b being aligned along a longitudinal direction of one of the two waveguides, each nanoresonator 324 defining a pixel of said holographic image.

[0102] The thickness of the coating layer 323 between a waveguide 322 and a nanoresonator 324 is for example between 30 and 100nm, such a thickness thus allows a light wave traveling through a waveguide 322 to activate a chain of nanoparticles 324a, 324b of a nanoresonator 324 placed above this waveguide 322.

[0103] The number of nanoresonators 324 at each intersection of waveguides 322 varies between 0 and n, n, representing the maximum number of nanoresonators 324 present above the same intersection].

[0104] According to a particular and non-limiting embodiment example, a thickness e of the coating layer 323 between a waveguide 322 and a nanoresonator 324 is between 30 and 100nm.

[0105] Figure 7 schematically illustrates a cross-sectional view of a nanoresonator 324 according to a particular, non-limiting embodiment of the present invention. Each chain of nanoparticles 324a, 324b of the nanoresonator 324 is composed of a phase-change material 3242 deposited between two layers of a plasmonic material 3241, 3243. The layer 3243 is in contact with the coating layer 323.

[0106] According to a particular and non-limiting embodiment, the plasmonic material is gold or silver.

[0107] According to a particular and non-limiting embodiment, the phase-change material is Vanadium Dioxide (VO2), a germanium-antimony-tellurium alloy (GeSbTe) or Antimony Trisulfide (SbS3).

[0108] According to a particular and non-limiting embodiment, each nanoresonator is optically activated from light waves of wavelengths equal to activation wavelengths of a set of activation wavelengths.

[0109] The activation lengths are defined by the lengths L of the lower layer 3243 of the nanoparticle chains. Thus, to activate a nanoresonator 324, the first nanoparticle chain 324a of this nanoresonator 324 must be illuminated by a first light wave with an activation wavelength equal to the first length Li of the first nanoparticle chain 324a, and the second nanoparticle chain 324b of this nanoresonator 324 must be illuminated by a second light wave with an activation wavelength equal to the second length L2 of the nanoparticle chain 324b. The first Li and second L2 lengths of the first 324a and second 324b nanoparticle chains of the same nanoresonator 324 are equal or different depending on the application.

[0110] Thus, any chain of nanoparticles oriented along the longitudinal direction of a waveguide 322 and placed on this waveguide is activated when this waveguide 322 is traversed by a light wave whose wavelength corresponds to the activation wavelength associated with the length L of this chain of nanoparticles.

[0111] The maximum number nj of nanoresonators 324 placed directly above an intersection j is for example defined by the surface occupied on the coating layer 323 by a nanoresonator 324, the minimum distance between two nanoresonators 324 and the surface available on the coating layer 323 directly above the intersection j.

[0112] The maximum number of nanoresonators 324 placed directly above an intersection j is, according to another example, defined by the number of distinct lengths L included in the set of lengths L so as not to simultaneously activate two nanoresonators 324 placed directly above the same intersection j.

[0113] Placing a plurality of nanoresonators 324 at each intersection of waveguides 322 increases the number of nanoresonators 324 in each longitudinal direction of the waveguide 322. Thus, for the same waveguide width 322 and the same distance separating two waveguides 322, the resolution of an image is increased compared to a solution using a single nanoresonator 324 at each intersection of waveguides 322. A maximum number of nanoresonators 324 can vary at the intersections of a waveguide lattice to create a holographic image comprising spatial regions with different resolutions. Alternatively, the same number of nanoresonators 324 are placed directly above each intersection of a waveguide lattice.

[0114] Figure 8 illustrates a particular, non-limiting embodiment of a spatial light modulator 32 comprising a lattice of four waveguides 322 forming a matrix comprising four intersections. Four nanoresonators 324 are positioned directly above each intersection, each near a corner of a surface of the coating layer 323 corresponding to an intersection. Each nanoresonator 324 corresponds to a pixel of a holographic image.

[0115] The spatial light modulator 32 according to the present invention is not limited to the example given in [Fig.8]. Indeed, the spatial light modulator may comprise more than one waveguide lattice, more than four waveguides 322 per lattice, any number of nanoresonators 324 per intersection without departing from the scope of the present invention.

[0116] Placing four nanoresonators 324 at each intersection of waveguides 322 doubles the number of nanoresonators 324 in each direction of waveguide 322. Thus, for the same waveguide width 322 and the same distance separating two waveguides 322, the resolution of an image is multiplied by 4 compared to a solution offering a single nanoresonator 324 per intersection. intersection of waveguides 322.

[0117] For example, nanoparticles have a size of 100 to 250 nm. The spatial light modulator 32 makes it possible to obtain pixel sizes less than 500nm leading to fields of view of more than 60° and very high holographic image resolutions, much higher than those of current holographic images.

[0118] A process for generating a holographic image is advantageously implemented by a spatial light modulator 32.

[0119] The generation of a holographic image includes the activation of nanoresonators 324 of the spatial light modulator 32. Each activated nanoresonator 324 corresponds to a luminous pixel of the holographic image. A nanoresonator 324 is placed directly above an intersection of a first waveguide 322i and a second waveguide 3222 of a waveguide lattice of the spatial light modulator 32 ([Fig.9]).

[0120] In a first operation, first data are received. The first data are representative of a first activation wavelength of a first chain of nanoparticles 324a of a nanoresonator 324 and of a second activation wavelength of a second chain of nanoparticles 324b of the nanoresonator 324.

[0121] According to a particular embodiment, the first and second light waves are near-infrared waves.

[0122] In a second operation, a first light wave with a wavelength equal to the first activation wavelength is emitted by a coherent light source associated with the first waveguide 322b, the first light wave propagating along a longitudinal direction of the first waveguide 322i to activate the nanoparticle chain 324a of the nanoresonator 324 aligned along the longitudinal direction of the first waveguide 322b

[0123] In a third operation, a second light wave with a wavelength equal to the second activation wavelength is emitted by a coherent light source associated with the second waveguide 3222, the second light wave propagating along a longitudinal direction of the second waveguide 3222 to activate the nanoparticle chain 324b of the nanoresonator 324 aligned along the longitudinal direction of the second waveguide 3222.

[0124] The first and second emitted light waves propagate respectively along the longitudinal direction of the first and second waveguides 322i and 3222 and interact with chains of nanoparticles aligned along the longitudinal directions of these waveguides. Only the nanoparticle chains aligned along the waveguides 322i and 3222 whose lengths correspond to the (activation) wavelengths of the emitted light waves are then activated (or excited) and They then behave like light concentrators on a sub-wavelength scale. The nanoresonator 324 corresponding to the activated nanoparticle chains is then said to be activated, that is to say, it concentrates enough light energy to form an illuminated pixel of the holographic image.

[0125] Each pixel of a holographic image can thus be illuminated. The propagation of two light waves of specific wavelengths makes it possible to address each pixel of the holographic image. This principle of individual pixel addressing is controlled by the wavelength values ​​of the light waves emitted along longitudinal directions of the waveguides 322, that is to say, by wavelength values ​​that correspond to the resonances of chains of nanoparticles 324a, 324b forming nanoresonators 324 placed directly above the intersections of the waveguide lattice.

[0126] [Fig.9] schematically illustrates pixel addressing of a holographic image by the spatial light modulator of [Fig.8] according to a particular and non-limiting embodiment of the present invention.

[0127] Pixel addressing is implemented here by referencing the two columns xl and x2 and the two rows yl and y2 of the matrix formed by the four intersections of the four waveguides of the waveguide lattice. Eight coherent light sources ^1.2, Âh.3, ^1.4, ^2.1, ^2.2, A-2.3 and ^<2.4 are associated with the y1 and y2 lines and eight coherent light sources -^1.2, Ad.3, Al.4, ^y2.2> A>2.3 and 2V2.4 are associated with the columns XL and x2.

[0128] Consider a pixel (white circle in Figure 9) corresponding to the intersection between column xl and row y2. The pixel is activated when the coherent light source An.2 of row y2 and the coherent light source A>2.2 of column xl simultaneously emit light waves whose 'activation' wavelengths correspond to the lengths of the nanoparticle chains of the nanoresonator corresponding to the pixel.

[0129] It can be noted that according to this example, pixel addressing is illustrated with a single waveguide lattice, but pixel addressing can also be implemented for several superimposed waveguide lattices.

[0130] According to a particular and non-limiting embodiment, the spatial light modulator 32 implements a so-called hologram function. This function is performed by the nanoresonators 324, which provide phase modulation of the visible incident light background. Indeed, when a pixel is activated, the activation of the nanoparticle chains creates a release of heat that modifies the phase of the material 3242. This modification varies continuously with the optical power, and induces a variation in the index of the phase-change material around these nanoresonators 324. With a controllable index change and a controlled range of "deposited" power, each pixel can induce a phase shift to a wave reflected on its surface with a sub-wavelength continuously varying from 0 to 2ir.

[0131] Figure 10 illustrates a flowchart of the different steps in a method for generating a holographic image, according to a particular and non-limiting embodiment of the present invention. The method is implemented, for example, by the holographic projection device 3 of Figure 3 and enables the activation of a pixel of the holographic image.

[0132] The method of generating a holographic image can be implemented by a spatial light modulator 32.

[0133] The method comprises the following steps for activating a nanoresonator 324 of the spatial light modulator 32 defining a pixel of a holographic image, said nanoresonator being placed directly above an intersection of a first waveguide 322i and a second waveguide 3222 of a waveguide lattice of the spatial light modulator 32:

[0134] In a first step 51, first data are received. The first data are representative of a first activation wavelength of a first chain of nanoparticles 324a of the nanoresonator 324 and of a second activation wavelength of a second chain of nanoparticles 324b of the nanoresonator 324.

[0135] In a second step 52, a first light wave with a wavelength equal to the first activation wavelength is emitted by a coherent light source associated with the first waveguide 322b, the first light wave propagating along a longitudinal direction of the first waveguide 322i to activate the first chain of nanoparticles 324a of the nanoresonator 324 aligned along the longitudinal direction of the first waveguide 322b

[0136] In a third step 53, a second light wave of wavelength equal to the second activation wavelength is emitted by a coherent light source associated with the second waveguide 3222, the second light wave propagating along a longitudinal direction of the second waveguide 3222 to activate the second nanoparticle chain 324b of the nanoresonator 324 aligned along the longitudinal direction of the second waveguide 3222.

[0137] Of course, the present invention is not limited to the embodiments described above but extends to a spatial light modulator that would include secondary elements without departing from the scope of the present invention. The present invention is not limited to the embodiments described above but extends to a method for generating a holographic image implemented by a spatial light modulator which would include secondary stages without going outside the scope of the present invention.

[0138] The present invention also relates to a holographic image projection device comprising at least one spatial light modulator 32.

[0139] According to a particular and non-limiting example of embodiment, holographic image projection device further includes means for implementing the process of [Fig. 10].

[0140] The present invention also relates to a vehicle, for example an automobile or more generally an autonomous land-powered vehicle, comprising at least one holographic image projection device described above.

Claims

Claims

1. Spatial light modulator (32) intended to be illuminated by coherent light sources to project a holographic image, said spatial light modulator (32) comprising: - a substrate (321) on which at least one lattice of waveguides is formed; - a coating layer (323) placed on said substrate and enveloping said waveguides; and - a plurality of nanoresonators placed on the coating layer directly above at least one intersection of two waveguides (322) of one of said at least one waveguide lattice, each nanoresonator (324) being optically activatable and being formed of two chains of nanoparticles (324a, 324b), each chain of nanoparticles (324a, 324b) being aligned along a longitudinal direction of one of the two waveguides, each nanoresonator (324) defining a pixel of said holographic image.

2. The spatial light modulator (32) of claim 1, wherein a chain of nanoparticles (324a, 324b) is composed of a phase change material deposited between two layers of a plasmonic material.

3. The spatial light modulator (32) of claim 2, wherein said plasmonic material is gold or silver.

4. A spatial light modulator (32) according to one of claims 2 to 3, wherein said phase change material is Vanadium dioxide (VO2), a germanium-antimony-tellurium alloy (GeSbTe) or Antimony Trisulfide (SbS3).

5. A spatial light modulator (32) according to one of claims 1 to 4, each nanoresonator is optically activated from light waves of wavelengths equal to activation wavelength values ​​of a set of activation wavelengths.

6. A spatial light modulator (32) according to one of claims 1 to 5, wherein said coating layer (323) is composed of hydrogen silsesquioxanes (HSQ).

7. A method of generating a holographic image implemented by a spatial light modulator (32) according to one of claims 1 to 6, said method comprising the following steps for activating a nanoresonator (324) of the spatial light modulator (32) defining a

8.

9.

10. pixel of a holographic image, said nanoresonator being placed directly above an intersection of a first waveguide (322J and a second waveguide (3222) of a lattice of waveguides of the spatial light modulator (32); - receiving (51) first data representative of a first activation wavelength of a first chain of nanoparticles (324a) of the nanoresonator (324) and of a second activation wavelength of a second chain of nanoparticles (324b) of the nanoresonator (324); - emission (52) of a first light wave of wavelength equal to the first activation wavelength by a coherent light source associated with the first waveguide (322J, said first light wave propagating along a longitudinal direction of the first waveguide (322i) to activate the first chain of nanoparticles (324a) of the nanoresonator (324) aligned along the longitudinal direction of the first waveguide (322i); and - emission (53) of a second light wave of wavelength equal to the second activation wavelength by a coherent light source associated with the second waveguide (3222), said second light wave propagating along a longitudinal direction of the second waveguide (3222) to activate the second chain of nanoparticles (324b) of the nanoresonator (324) aligned along the longitudinal direction of the second waveguide (3222). Holographic image projection device comprising at least one spatial light modulator according to one of claims 1 to 6. Device according to claim 8, which further comprises means for implementing the method according to claim 7. Vehicle comprising at least one holographic image projection device according to claim 8 or 9.

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