WO2022090232A1

WO2022090232A1 - Head-up display with holographic slide

Info

Publication number: WO2022090232A1
Application number: PCT/EP2021/079692
Authority: WO
Inventors: Thomas Avisse; Soukaina CHAKIR; Stephane Gache; Pierre Mermillod; François GRANDCLERC
Original assignee: Valeo Comfort And Driving Assistance
Priority date: 2020-10-26
Filing date: 2021-10-26
Publication date: 2022-05-05
Also published as: EP4232855A1; FR3117222A1

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 designed to generate a raw image, and an image-returning system fixed to the housing. According to the invention, the image-returning system comprises a holographic slide (30) that completely closes off a window (41) formed in the housing, which is arranged to receive the raw image generated by the image-forming device and which is designed to magnify said raw image.

Description

DESCRIPTION

INTENTION TITLE: HOLOGRAPHIC BLADE HEAD-UP DISPLAY

TECHNICAL FIELD OF THE INVENTION

The present invention generally relates to motor vehicle driving assistance devices.

[0002] It relates more particularly to a head-up display for a motor vehicle, which comprises:

- a housing,

- an image forming device housed inside the case and adapted to generate a raw image, and

- an image return system fixed to the case.

STATE OF THE ART

[0003] In order to make driving a motor vehicle easier and safer, it is desired to prevent the driver from being forced to look away from the road he is taking when he wishes to look at the dashboard, for example to see how fast it is going or which direction it needs to take to get to its destination.

[0004] For this, it is known to use a head-up display, suitable for projecting basic information (vehicle speed, direction to follow, etc.) at the level of the driver's eyes when the latter observes the road. .

[0005] Such a display generally comprises an image-forming device and an image-returning system which makes it possible to reflect the light beam emitted by the image-forming device towards a partially reflecting plate (commonly referred to as a "combiner" >) located in the driver's field of vision.

[0006] Such a display further comprises a housing which houses the image-forming device and the image-returning system. This box is designed to be placed in the passenger compartment of the vehicle, more precisely in the dashboard of the vehicle, that is to say under the windshield.

[0007] To allow the passage of light from the image-forming device to the partially reflecting blade which is located outside the housing, the latter has a main window. [0008] To prevent objects from falling into the casing or dust entering the interior of the casing, which could damage one of the components of the display, this main window is generally closed by a glass protection.

[0009] The major drawback of this protective glass is that, since it is positioned close to the windshield, it is likely to reflect outside light, in particular sunlight, as well as to refract this light at the inside the case. It may then happen that this light disturbs 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, as a partially reflecting strip, the windshield itself. The surface offered by this windshield being very large, it is then possible to implement an augmented reality function making it possible to display in the driver's field of vision elements superimposed on the environment, in a position which depends precisely on this environment.

[001 1] The difficulty is that the field of vision in which the information must be displayed is very large. The image return system must then include a large magnifying mirror to cover the desired surface of the windshield. The size of the protective glass must also be increased, which makes the above-mentioned luminosity problems even more significant.

[0012] Furthermore, these large-sized elements generate significant space, in particular because the mirror must be inclined with respect to the protective glass. As a result, the box that houses these elements occupies a large volume that is difficult to fit into the passenger compartment of the vehicle during the design of the latter.

[0013]Finally, it proves difficult to produce mirrors able to achieve the desired magnification at limited costs, without generating unpleasant optical aberrations for the driver.

PRESENTATION OF THE INVENTION

[0014] In order to remedy the aforementioned drawbacks of the state of the art, the present invention proposes to replace the mirror and the protective glass with a single element providing their various functions. [0015] More particularly, according to the invention, a head-up display as defined in the introduction is proposed, in which the image-returning system comprises a holographic blade which completely closes a window formed in the housing, which is arranged to directly receive the raw image generated by the image forming device and which is adapted to enlarge this raw image. [0016] Thus, thanks to the invention, the holographic blade alone performs several functions, which makes it possible to reduce the size of the display. The use of a holographic plate which has an image magnification function further makes it possible to reduce the size of the case. Finally, the manufacturing cost of such a holographic plate turns out to be lower than that of a well-made concave mirror.

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

- the return system is adapted to return the light beam from the image-forming device to the windshield of the motor vehicle;

- said holographic blade is the only component of the return system which is suitable for magnifying said raw image;

- the image return system is formed solely from said holographic blade, the light beam from the image forming device being oriented directly towards said holographic blade and the light beam from said holographic blade being oriented directly towards the visor motor vehicle breeze;

- the holographic blade has a function of deflecting the light beam passing through it;

- the holographic blade has a function of distorting the light beam passing through it, said distortion being associated with a shape of a motor vehicle windscreen;

- the holographic blade is formed by an inert plate;

- the holographic blade is formed by a flat plate;

- the image-forming device comprises at least one monochromatic light source.

[0018] 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.

[0019] Preferably, the holographic blade deflects the light beam directly from the image-forming device towards the windshield.

Of course, the different characteristics, variants and embodiments of the invention can be associated with each other in various combinations insofar as they are not incompatible or exclusive of each other.

DETAILED DESCRIPTION OF THE INVENTION

The following description with reference to the accompanying drawings, given by way of non-limiting examples, will make it clear what the invention consists of and how it can be implemented.

[0022] In the accompanying drawings:

[0023] [Fig. 1] is a view representing, in section and from the side, a head-up display according to the invention, placed in the passenger compartment of a motor vehicle.

In Figure 1, there is shown a head-up display 10 intended to equip any motor vehicle (car, truck ...).

[0025] Such a motor vehicle conventionally comprises a chassis and a body which delimit a passenger compartment 70 for the driver and for the passengers of the vehicle.

This cabin 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 60 dashboard.

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 windshield 50 of the vehicle.

This head-up display 10 comprises a box 40 which houses a computer 80 and an image forming device 20 controlled by the computer 80. An image return system is also attached to this box 40.

The housing 40 has outer walls which define between them an interior space. It comprises means for securing to the dashboard 60 of the vehicle, and means for fixing the image-forming device 20, the computer 80 and the image-returning system. It can for example be screwing means or any other suitable means.

As shown in Figure 1, the image forming device 20 comprises a light source 21 and an image generation system 22.

[0031] The light source 21 comprises at least one monochromatic source. By monochromatic, we mean that it emits in a very small frequency band, preferably as small as possible. Here, the monochromatic source preferably emits a laser beam.

The light source 21 preferably comprises two (or even three) monochromatic sources emitting at distinct frequencies. One can thus provide that one of these monochromatic sources emits in the green while the other of these monochromatic sources emits in the red (the possible third monochromatic source emitting in the blue).

If the light source 21 comprises exactly two monochromatic sources, the colors used will make it possible to display green, yellow and red information in the driver's field of vision.

If the light source 21 comprises exactly three monochromatic sources, the colors used will make it possible to display in the driver's field of vision information of all possible colors, as well as white information.

The respective light beams of the monochromatic sources are preferentially 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 .

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

If it is of the "light modulation" type, it could include a liquid crystal display (or LCD for "Liquid Crystal Display") with thin-film transistors (or TFT for "Thin-Film Transistor") , controlled by the computer. However, preferably, it will instead comprise a matrix of micro-mirrors that can be oriented independently of each other (one then commonly speaks of DMD or DLP technology).

It will be considered here that the image generation system 22 is of the "emissive" type and that it comprises 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 comprise at least one movable mirror, for example in the form of a micro electromechanical system (or MEMS for "MicroElectroMechanical System" ).

Whatever its type, the image forming device 20 makes it possible, under the control of the computer, to generate raw images comprising information useful for driving the vehicle, which the image return system will be able to project into the driver's field of vision when the driver's gaze is turned towards the road.

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

This image return system comprises a holographic blade 30.

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

It is designed to directly receive the raw image emitted by the image forming device 20. By "directly", we mean that no optical component is located between the image forming device 20 and this holographic blade 30.

[0044] The holographic blade 30 has an interference pattern which makes it possible to restore a holographic image when it is illuminated by the light beam from the image-forming device 20.

It is more specifically provided to distort the raw image displayed by the image forming device 20 in a particular way. It has different “functions” for this purpose.

The first of these functions is a raw image magnification function.

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

In this way, the width of the light beam arriving on the windshield 50 is large, which not only makes it possible to display more information in the driver's field of vision, but which above all makes it possible to implement a augmented reality function making it possible to display elements superimposed on the environment in the driver's field of vision, in a position which precisely depends on this 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 about to cross the road, so as to draw the driver's attention to the latter. .

It will 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.

[0050] Moreover, preferably, the image return system is composed exclusively of a single element, namely this holographic blade 30, which makes it possible to reduce its bulk and its cost.

Preferably, the holographic plate 30 also has a function of deflecting the light beam passing through it.

In other words, if we consider, on the one hand, the mean axis of the light beam which is emitted by the image-forming device 20 and which arrives at this blade, and, on the other hand , the axis of the light beam which emerges from the holographic blade 30, it can be seen that these two axes are inclined relative to each other.

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

In the case considered here, the angle of deflection of the light beam is chosen so that it takes a direction distinct from that of the parasitic light

[0055] Thanks to this deviation 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 deviation possibly being adjusted so as to that the light beam coming out of the head-up display 10 is oriented towards the desired area of the windshield 50 of the motor vehicle.

The third function of the holographic blade 30 is a function of distortion of the light beam passing through it.

[0057] Indeed, the windshield has a very particular curvature, which is not the same from one motor vehicle model to another. This curvature also varies from one point of the windshield to another.

The distortion function then makes it possible to compensate for this curvature so that the virtual image Img seen by the driver is as far as possible devoid of geometric aberration.

The distortion provided in the interference figure of the holographic blade 30 is then variable from one model of the motor vehicle to another, since it will be specific to the model of windshield fitted to the vehicle in which it will be installed. the head-up display 10,

In practice, the holographic blade 30 appears here in the form of a translucent and inert flat plate.

[0061] It is for example obtained by insolation. By way of example, it may be formed of a photopolymer layer coated with a hardenable protective layer making it possible to seal the interference figure printed on the photopolymer layer.

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

[0063] This convex mirror will then have to present the three aforementioned functions of magnification, deviation and distortion (by having a suitable shape and by being oriented with a desired inclination in the second channel of the interferometer).

Of course, the interference figure could be obtained otherwise, for example by calculations and by photo-printing.

As shown in Figure 1, the holographic plate 30 and the windshield 50 allow the light beam to be returned to the driver, so as to display the virtual image Img in the driver's field of vision.

[0066] The light beam is therefore returned to the driver's face, on a surface (commonly referred to as an "eye box") which encompasses the driver's two eyes. This surface, measured in the plane in which the eyes of a driver are generally located (on average), has the overall shape of a rectangle of 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, whatever 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.

On this subject, it will be noted that the use of a holographic blade 30 makes it possible to overcome alignment constraints. Indeed, since the information stored in the holographic blade 30 is a Fourier transform, the information is repeated over the whole of the holographic blade 30 so that the driver will see the assistance information in substantially the same way. driving regardless of the position of his eyes in the aforementioned area. The holographic blade 30 also makes it possible to properly control the dynamic distortion, that is to say the fact that the distortion of the perceived image varies when the driver moves his head from top to bottom or from right to left (due in particular to that the curvature of the windshield varies from point to point).

[0069] Here, as shown in Figure 1, the holographic plate is directly attached to the case. It is here more precisely fixed in a window 41 made in the wall of the case which faces the windshield 50. It is fixed there so as to close it completely, in a dust-tight manner of more than one millimeter in diameter.

[0070] It is here fixed in the plane of this window 41, but it could alternatively be fixed against the internal face or against the external face of the housing 40.

The present invention is in no way limited to the embodiment described and represented, but those skilled in the art will know how to make any variant in accordance with the invention.

[0072] For example, it would be possible to use a partially reflecting plate (commonly called a “combiner”) to reflect the light beam that comes out of the head-up display 10 into the driver's field of vision.

According to another variant of the invention, provision could be made for the holographic blade to have only one or two functions (the magnification function here being the only one considered essential).

Claims

[Claim 1] Head-up display (10) for a motor vehicle, comprising:

- a box (40),

- an image forming device (20) housed inside the housing (40) and adapted to generate a raw image, and

- an image return system fixed to the housing (40), characterized in that the image return system comprises a holographic blade (30) which completely closes a window (41) formed in the housing (40), which is arranged to directly receive the raw image generated by the image forming device (20) and which is adapted to magnify said raw image.

[Claim 2] Head-up display (10) according to the preceding claim, in which, the return system being adapted to return the light beam coming from the image-forming device (20) towards the windscreen (50) of the motor vehicle, said holographic blade (30) is the only component of the return system which is adapted to magnify said raw image.

[Claim 3] Head-up display (10) according to one of the preceding claims, in which the image return system is formed solely of said holographic plate (30), the light beam issuing from the image-forming device (20) being oriented directly towards said holographic blade (30) and the light beam from said holographic blade (30) being oriented directly towards the windshield (50) of the motor vehicle.

[Claim 4] Head-up display (10) according to one of the preceding claims, in which the holographic blade (30) has a function of deflecting the light beam passing through it.

[Claim 5] Head-up display (10) according to one of the preceding claims, in which the holographic blade (30) has a function of distorting the light beam passing through it, said distortion being associated with a shape of (50) motor vehicle.

[Claim 6] Head-up display (10) according to one of the preceding claims, in which the holographic blade (30) is formed by a inert plate.

[Claim 7] Head-up display (10) according to one of the preceding claims, in which the holographic plate (30) is formed by a flat plate.

[Claim 8] Head-up display (10) according to one of the preceding claims, in which the imaging device (20) comprises at least one monochromatic light source.

[Claim 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) according to one of the preceding claims, housed in the dashboard (60).

[Claim 10] Motor vehicle according to the preceding claim, in which the holographic blade (30) deflects the light beam directly coming from the image-forming device (20) towards the windshield.