holographic blade head-up display

Abstract

The invention relates to a head-up display (10) for a motor vehicle, comprising a housing (40), an image-forming device (20) housed inside the housing and adapted to generate a raw image, and an image feedback system attached to the housing. According to the invention, the image feedback system comprises a holographic plate (30) that completely closes a window (41) formed in the housing, which is arranged to receive the raw image generated by the image-forming device and is adapted to magnify said raw image. Figure for the abstract: Fig. 1

Description

Title of the invention: Holographic blade head-up display Technical field of the invention

[0001] The present invention relates generally to driving assistance devices for motor vehicles.

[0002] It relates more particularly to a head-up display for a motor vehicle, which comprises: - a housing, - an image formation device housed inside the casing and adapted to generate a raw image, and - an image transmission system attached to the housing. State of the art

[0003] In order to make driving a motor vehicle easier and safer, it is desirable to avoid the driver being forced to take his eyes off the road he is driving on when he wants to look at the dashboard, for example to see the speed at which he is driving or the direction he must take to get to his destination.

[0004] For this purpose, it is known to use a head-up display, adapted to project basic information (vehicle speed, direction to follow, ...) at the driver's eye level when the latter observes the road.

[0005] Such a display generally includes an image formation device and an image feedback system which makes it possible to reflect the light beam emitted by the image formation device towards a partially reflective plate (commonly called a "combiner") located in the driver's field of vision.

[0006] Such a display further comprises a housing which contains the image formation device and the image transmission system. This housing is designed to be mounted inside the vehicle's passenger compartment, more specifically in the vehicle's dashboard, i.e., under the windshield.

[0007] To allow the passage of light from the image-forming device to the partially reflective blade located outside the housing, the latter has a main window.

[0008] To prevent objects from falling into the case or dust from entering the case, which could damage one of the display components, this main window is generally closed by a protective glass.

[0009] The major drawback of this protective glass is that, since it is positioned close to the windshield, it is likely to reflect external light, particularly sunlight, and to refract this light into the interior of the housing. It can then happen that this light interferes with the readability of the information projected by the head-up display, or even that it bothers the driver of the vehicle.

[0010] It is also known to use the windshield itself as a partially reflective blade. Since the surface area offered by this windshield is very large, it is then conceivable to implement an augmented reality function allowing elements superimposed on the environment to be displayed in the driver's field of vision, in a position that depends precisely on this environment.

[0011] The difficulty lies in the fact that the field of vision within which the information must be displayed is very large. The image transmission system must therefore include a large magnifying mirror to cover the desired area of ​​the windshield. The size of the protective glass must also be increased, which makes the aforementioned brightness problems even more pronounced.

[0012] Furthermore, these large components generate significant bulk, particularly because the mirror must be angled relative to the protective glass. Consequently, the housing containing these components occupies a large volume that is difficult to integrate into the vehicle's interior during the vehicle's design phase.

[0013] Finally, it proves difficult to produce mirrors capable of achieving the desired magnification at limited costs, without generating optical aberrations unpleasant for the driver. Presentation of the invention

[0014] In order to remedy the aforementioned drawbacks of the prior art, the present invention proposes to replace the mirror and the protective glass with a single element ensuring their different functions.

[0015] More particularly, the invention proposes a head-up display as defined in the introduction, in which the image transmission system includes a holographic blade which completely closes a window made in the housing, which is arranged to directly receive the raw image generated by the image formation device and which is adapted to enlarge this raw image.

[0016] Thus, thanks to the invention, the holographic plate alone performs several functions, thereby reducing the size of the display. The use of a holographic plate that magnifies images also allows for a reduction in the size of the casing. Finally, the manufacturing cost of such a holographic plate is lower than that of a high-quality concave mirror.

[0017] Other advantageous and non-limiting features of the head-up display according to the invention, taken individually or in all technically possible combinations, are as follows:

[0018] - the reflecting system is adapted to reflect the light beam from the device image formation towards the windshield of the motor vehicle; - said holographic blade is the only component of the transmission system which is adapted to magnify said raw image; - the image transmission system consists solely of said holographic blade, the light beam from the image formation device being directed directly towards said holographic blade and the light beam from said holographic blade being directed directly towards the windshield of the motor vehicle; - the holographic blade has a function of deflecting the light beam that passes through it; - the holographic blade has a function of distorting the light beam that passes through it, said distortion being associated with a shape of motor vehicle windshield; - the holographic plate is formed by an inert plate; - the holographic blade is formed by a flat plate; - the image formation device includes at least one monochromatic light source.

[0019] The invention also proposes a motor vehicle comprising a passenger compartment which is closed at the front by a windshield and which internally houses a dashboard, and a head-up display as mentioned above, housed in the dashboard.

[0020] Preferably, the holographic blade deflects the light beam directly from the image formation device towards the windshield.

[0021] Of course, the various features, variants, and embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. Detailed description of the invention

[0022] The following description with regard to the attached drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be carried out.

[0023] On the attached drawings:

[0024] [Fig. 1] is a view representing, in section and side, a head-up display according to the invention, placed in the passenger compartment of a motor vehicle.

[0025] In [Fig. 1], a head-up display 10 intended to be fitted to any motor vehicle (car, truck...) is shown.

[0026] Such a motor vehicle classically comprises a chassis and a body which delimit a passenger compartment 70 for the driver and for the passengers of the vehicle.

[0027] This passenger compartment 70 is closed at the front by a windshield 50 through which the driver can observe the road. It houses various elements, including seats and a dashboard 60.

[0028] The head-up display 10 is here designed to be fixed to the dashboard 60 and to emerge from the latter through an opening 61 located opposite the windscreen 50 of the vehicle.

[0029] This head-up display 10 includes a housing 40 which houses a computer 80 and an image formation device 20 controlled by the computer 80. An image transmission system is also attached to this housing 40.

[0030] The housing 40 comprises external walls that define an internal space. It includes means for attaching it to the vehicle's dashboard 60, and means for securing the image formation device 20, the computer 80, and the image transmission system. These means may, for example, be screws or any other suitable means.

[0031] As shown in [Fig.1], the image formation device 20 comprises a light source 21 and an image generation system 22.

[0032] The light source 21 comprises at least one monochromatic source. By monochromatic, it is understood that it emits in a very narrow frequency band, preferably as narrow as possible. Here, the monochromatic source preferably emits a laser beam.

[0033] The light source 21 preferably comprises two (or even three) monochromatic sources emitting at distinct frequencies. It can thus be provided that one of these monochromatic sources emits in the green while another emits in the red (the possible third monochromatic source emitting in the blue).

[0034] If the light source 21 comprises exactly two monochromatic sources, the colours used will allow green, yellow and red information to be displayed in the driver's field of vision.

[0035] If the light source 21 comprises exactly three monochromatic sources, the colors used will allow information of all possible colors, as well as white information, to be displayed in the driver's field of vision.

[0036] The respective light beams of the monochromatic sources are preferably combined (for example using dichroic mirrors) in order to form a polychromatic light beam (here laser) emitted at the output of the light source 21.

[0037] The image generation system 22 can be of the "light modulation" type or of the "emissive" type.

[0038] If it is of the "light-modulating" type, it could include a liquid crystal display (LCD for "Liquid Crystal Display") with thin-film transistors (TFT for "Thin-Film Transistor"), controlled by the computer. However, preferably, it will instead include an array of micromirrors that can be oriented independently of each other (this is commonly referred to as DMD or DLP technology).

[0039] Here, the image generation system 22 will be considered to be of the "emissive" type and to include a diffuser 24 on which the images are formed and a scanning unit 23 controlled by the computer so as to deflect the laser beam in variable directions to scan the rear face of the diffuser 24. The scanning unit 24 may thus, for example, include at least one movable mirror, for example in the form of a microelectromechanical system (or MEMS for "MicroElectroMechanical System").

[0040] Whatever its type, the image formation device 20 allows, under the control of the computer, the generation of raw images including information useful for driving the vehicle, which the image transmission system will be able to project into the driver's field of vision when the latter's gaze is turned towards the road.

[0041] As shown in [Fig.1], the image transmission system, which is more specifically the subject of the present invention, is more specifically designed to project a virtual image Img into the driver's field of vision, at a distance from the driver that is greater than that separating the driver from the windshield 50 (so that the driver's eyes do not have to perform accommodation work to clearly perceive the road and the projected information).

[0042] This image transmission system includes a holographic blade 30.

[0043] This holographic blade 30 is designed to be traversed by the light beam from the image formation device 20. We therefore speak of a transmission hologram.

[0044] It is designed to receive directly the raw image emitted by the image-forming device 20. By "directly", it is meant that no optical component is located between the image-forming device 20 and this holographic plate 30.

[0045] The holographic blade 30 has an interference pattern which makes it possible to reproduce a holographic image when it is illuminated by the light beam from the image formation device 20.

[0046] More specifically, it is designed to distort the raw image displayed by the image formation device 20 in a particular way. It has various "functions" for this purpose.

[0047] The first of these functions is a function for enlarging the raw image.

[0048] Thus, the maximum apex angle of the cone formed by the light beam from the image formation device 20 is less than the maximum apex angle of the cone formed by the virtual image.

[0049] In this way, the width of the light beam reaching the windshield 50 is large, which not only allows more information to be displayed in the driver's field of vision, but also, and more importantly, enables the implementation of an augmented reality function that displays elements superimposed on the environment within the driver's field of vision, in a position that depends precisely on that environment. For example, it is possible to display a flashing red triangle in the driver's field of vision at the level of a pedestrian preparing to cross the road, so as to draw the driver's attention to the pedestrian.

[0050] It should be noted here that the holographic blade 30 is preferably the only component of the head-up display 10 to ensure such a function of magnification of the raw image.

[0051] Moreover, preferably, the image transmission system is composed exclusively of a single element, namely this holographic blade 30, which makes it possible to reduce its size and cost.

[0052] Preferably, the holographic blade 30 also has a function of deflecting the light beam that passes through it.

[0053] In other words, if we consider, on the one hand, the average axis of the light beam which is emitted by the image formation device 20 and which arrives on this plate, and, on the other hand, the axis of the light beam which comes out of the holographic plate 30, we find that these two axes are inclined with respect to each other.

[0054] This holographic blade 30 is thus arranged with respect to the image formation device 20 so as to directly receive the raw image generated by this image formation device 20, to enlarge it and deflect it (by transmission) in a particular direction.

[0055] In the case considered here, the angle of deviation of the light beam is chosen so that it takes a direction distinct from that of the stray lights

[0056] Thanks to this deflection function, the designer of the motor vehicle also has more latitude to install the head-up display 10 in the passenger compartment 70 of the vehicle, the angle of deflection being able to be adjusted so that the light beam coming out of the head-up display 10 is directed towards the desired area of ​​the windshield 50 of the motor vehicle.

[0057] The third function of the holographic blade 30 is a function of distorting the light beam that passes through it.

[0058] Indeed, the windshield has a very particular curvature, which is not the same from one model of motor vehicle to another. This curvature also varies from one point to another on the windshield.

[0059] The distortion function then makes it possible to compensate for this curvature so that the virtual image Img seen by the driver is as free as possible from geometric aberration.

[0060] The distortion predicted in the interference pattern of the holographic blade 30 is therefore variable from one model of the motor vehicle to another, since it will be specific to the windshield model fitted to the vehicle in which the head-up display 10 will be installed,

[0061] In practice, the holographic blade 30 is presented here in the form of a flat, translucent and inert plate.

[0062] It is obtained, for example, by exposure. As an example, it can be formed of a photopolymer layer coated with a sand-cured protective layer allowing the interference pattern printed on the photopolymer layer to be sealed.

[0063] This impression can for example be obtained using a two-way interferometer, in one of the channels of which a flat mirror serving as a reference is placed, and in the other of the channels of which a convex mirror is placed.

[0064] This convex mirror must then have the three aforementioned functions of magnification, deviation and distortion (by having a suitable shape and being oriented with a desired inclination in the second channel of the interferometer).

[0065] Of course, the interference pattern could be obtained in another way, for example by calculations and by photo-printing.

[0066] As shown in [Fig.1], the holographic plate 30 and the windscreen 50 make it possible to reflect the light beam towards the driver, so as to display the virtual image Img in the driver's field of vision.

[0067] The light beam is therefore reflected back towards the driver's face, onto a surface (commonly called "eye box") which encompasses both of the driver's eyes.

[0068] This surface, measured in the plane in which a driver's eyes are generally (on average) located, has an overall rectangular shape with large dimensions, greater than 90 mm by 90 mm, here equal to 120 mm by 120 mm or 120 mm by 140 mm. In this way, regardless of the position of the driver's face in this plane (shifted upwards, downwards, to the right or to the left), the driver will perceive the information displayed by the head-up display 10.

[0069] In this regard, it should be noted that the use of a holographic plate 30 eliminates the constraints of alignment. Indeed, since the information stored in the holographic plate 30 is a Fourier transform, the information is repeated across the entire holographic plate 30, so that the driver will see the driving assistance information in essentially the same way regardless of the position of their eyes on the aforementioned surface. The holographic plate 30 also allows for precise control of dynamic distortion, that is to say, the distortion of the image perceived varies when the driver moves their head up and down or from side to side (due in particular to the fact that the curvature of the windshield varies from one point to another).

[0070] Here, as shown in [Fig. 1], the holographic plate is directly attached to the housing. More precisely, it is fixed in a window 41 made in the wall of the housing facing the windshield 50. It is fixed there in such a way as to close it completely, in a manner that is dustproof to particles larger than one millimeter in diameter.

[0071] It is here fixed in the plane of this window 41, but it could alternatively be fixed against the inner face or against the outer face of the housing 40.

[0072] The present invention is in no way limited to the embodiment described and represented, but a person skilled in the art will be able to make any variation in accordance with the invention.

[0073] By way of example, it would be possible to use a partially reflective blade (commonly called a "combiner") to reflect the light beam coming out of the head-up display 10 into the driver's field of vision.

[0074] According to another variant of the invention, it could be envisaged that the holographic blade has only one or two functions (the magnification function being here the only one considered essential).

Claims

Demands

1. A head-up display (10) for a motor vehicle, comprising: - a housing (40), - an image-forming device (20) housed inside the housing (40) and adapted to generate a raw image, the image-forming device (20) comprising a light source (21) and an image generation system (22), and - an image transmission system attached to the housing (40), the image transmission system comprising a holographic plate (30) that completely closes a window (41) formed in the housing (40), the holographic plate (30) is designed to be traversed by the light beam from the image-forming device (20), forming a transmission hologram, characterized in that the holographic plate (30) is arranged to directly receive the raw image generated by the image-forming device (20) and is adapted to magnify said raw image, the image transmission system is composed exclusively of a only element,namely this holographic blade 30.,

2. Head-up display (10) according to the preceding claim, wherein, the reflection system being adapted to reflect the light beam from the image-forming device (20) back to the windscreen (50) of the motor vehicle, said holographic blade (30) is the only component of the reflection system which is adapted to magnify said raw image.

3. Head-up display (10) according to any one of the preceding claims, wherein the image feedback system is formed solely of said holographic blade (30), the light beam from the image-forming device (20) being directed directly towards said holographic blade (30) and the light beam from said holographic blade (30) being directed directly towards the windscreen (50) of the motor vehicle.

4. Head-up display (10) according to any one of the preceding claims, wherein the holographic blade (30) has a function of deflecting the light beam that passes through it.

5. Head-up display (10) according to any one of the preceding claims, wherein the holographic blade (30) has a distortion function of the light beam which passes through it, said distortion being associated with a windshield shape (50) of a motor vehicle.

6. Head-up display (10) according to any one of the preceding claims, wherein the holographic blade (30) is formed by an inert plate.

7. Head-up display (10) according to any one of the preceding claims, wherein the holographic blade (30) is formed by a flat plate.

8. Head-up display (10) according to any one of the preceding claims, wherein the image-forming device (20) comprises at least one monochromatic light source.

9. Motor vehicle comprising a passenger compartment (70) closed at the front by a windscreen (50) and which internally houses a dashboard (60), characterized in that it comprises a head-up display (10) conforming to one of the preceding claims, housed in the dashboard (60).

10. Motor vehicle according to the preceding claim, wherein the holographic blade (30) deflects the light beam directly from the image-forming device (20) towards the windshield.

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