FR3044107A1 - HEAD-UP DISPLAY EQUIPPED WITH A WAVE GUIDE - Google Patents

Abstract

The invention relates to a head-up display for a motor vehicle, comprising an image generation device and a combiner (20) arranged to receive the light beam emitted by the image generation device and to project the images generated. in the field of vision of the driver of the motor vehicle. According to the invention, the display comprises a waveguide in which there is provided a pattern (22) and at least one light source (30) adapted to illuminate the pattern.

Description

Head-up display equipped with a waveguide

Technical field to which the invention relates

The present invention generally relates to devices for assisting the driving of motor vehicles.

It relates more particularly to a head-up display for a motor vehicle, comprising an image generation device and a combiner arranged to receive the light beam emitted by the image generation device and to project the images into the field of view. vision of the driver of the motor vehicle.

Technological background

To facilitate and make safer driving a motor vehicle, we want to prevent the driver is forced to look away from the road he takes.

For this, it is known to use a head-up display, adapted to project basic information (speed of the vehicle, direction to follow, ...) and safety information (engine malfunction, presence of obstacles,. ..) at the driver's eye level.

Two types of head-up displays are particularly known.

The displays of the first type use an image forming device comprising a diffuser and a scanning unit designed to generate a light beam scanning an entrance face of the diffuser. The light beam at the output of the diffuser thus forms an image, which can then be projected into the field of vision of the driver of the vehicle by means of a combiner.

The displays of the second type use a screen that generates an image, which is then projected into the field of view of the driver, here also by means of a combiner.

In both cases, the combiner makes it possible for the driver to perceive the elementary and safety information in superposition of the view he has of the road.

Such a head-up display however has a major disadvantage, namely that in case of failure of the image generation device, it is no longer able to project any information, including security information.

Object of the invention

In order to overcome the aforementioned drawback of the state of the art, the present invention proposes a head-up display as defined in the introduction, comprising: a waveguide which has two main faces and a lateral edge and in which a pattern is provided, and - at least one light source adapted to illuminate the pattern by the side edge of the waveguide so that light emerges from one of the two main faces of the waveguide. wave.

The pattern is then likely to illuminate when illuminated by the light source, so that it can display information. It remains invisible when the light source is off, so it does not interfere with the driver's vision.

The technology employed is not dependent on the operation of the image generation device and is based on simple components, so that it has high reliability. Therefore, its use for displaying security information is well suited. Its implementation is also inexpensive.

The technology employed furthermore makes it possible, when the waveguide is visibly installed by the passengers of the vehicle, to display information in a visible manner not only for the driver, but also for these passengers. Therefore, the display provides greater safety as passengers can warn the driver of the imminence of a danger when the motive illuminates at a time when the driver has diverted his eyes from the road.

The technology employed finally makes it possible to place the waveguide on the optical path of the head-up display, without modifying the architecture of the latter, which makes its installation rather difficult since it does not require modifying the displays. head-high existing. Other advantageous and non-limiting features of the head-up display according to the invention are the following: each light source comprises a light-emitting diode; said pattern is etched in the waveguide, at a distance from the lateral edge of the waveguide; said pattern is formed by microstructures provided in the waveguide and forming an optical element for guiding the light; said pattern is formed by diffractive optical elements provided in the waveguide; each diffractive optical element is adapted to be actively controlled; the combiner comprises a semi-reflecting transparent plate, which forms the waveguide; the combiner has a display area which receives the light beam emitted by the image generating device, and each pattern is located outside this display area; the image generation device comprises a screen and the waveguide is placed against the screen or at a reduced distance therefrom; - The distance between the waveguide and the screen is less than 2 centimeters.

Detailed description of an example of realization

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

In the accompanying drawings: - Figure 1 is a schematic view of a first embodiment of a head-up display according to the invention; FIG. 2 is a schematic view of a second embodiment of a head-up display according to the invention; FIG. 3 is a schematic view of a combiner that can be used in either of the two embodiments of the head-up display shown in FIGS. 1 and 2; FIG. 4 is a schematic view of an image generation unit that can be used in the head-up display of FIG. 1; and FIG. 5 is a schematic view of an alternative embodiment of the image generation unit of FIG. 4.

In Figures 1 and 2, there are shown two embodiments of a head-up display 10 for equipping a vehicle, for example a motor vehicle.

In these two embodiments, the head-up display 10 comprises an image generation unit 11 driven by a computer (not represented), and an optical projection assembly 12.

In the first embodiment illustrated in FIG. 1, the image generation unit 11 comprises a screen 11A, here a liquid crystal display (or LCD for "Liquid Crystal Display") with thin-film transistors (or TFT for "Thin-Film TransistoF). It also includes here a backlight device 11C located at the rear of the screen 11A and a protective glass 11B located at the front of the screen 11A.

In the second embodiment illustrated in FIG. 2, the image generation unit 11 comprises a diffuser 16 and a scanning unit which generates a light beam of variable direction so as to be able to scan the rear face of the diffuser 16. The scanning unit more specifically comprises a beam forming module 14 and a movable mirror 15, for example made in the form of an electromechanical microsystem (or MEMS for "MicroElectroMechanical System").

The beam forming module 14 typically comprises three monochromatic light sources, such as laser sources, whose respective (monochromatic) light beams are combined (for example using dichroic mirrors) to form the polychromatic light beam ( here laser) emitted at the output of the beam forming module 14. This light beam generated by the beam forming module 14 is directed towards the moving mirror 15, whose orientation is controlled by a control module so that the reflected light beam (by the movable mirror 15) sweeps the rear face of the diffuser 16.

In these two embodiments, the image generation unit 11 makes it possible, under the control of the computer, to generate an image that the projection optical assembly 12 will be able to project into the driver's field of vision when the the latter is turned towards the road.

In the two embodiments shown in FIGS. 1 and 2, the projection optical assembly 12 is more precisely designed to project a virtual image Img into the field of vision of the driver of the vehicle, at a distance from the driver that is greater than that separating the driver from the windshield 1 (so that the work of accommodation that the eyes of the driver must make to move from the road to projected information is reduced). For this purpose, the optical projection unit 12 comprises an optical return system 13 and a combiner 20 placed in the field of vision of the driver of the vehicle.

The optical return system 13, which here comprises only a folding mirror, makes it possible to fold the optical path and to return the image generated by the image generation unit 11 to the combiner 20.

The combiner 20 makes it possible to reflect this image in such a way that it appears to the driver as if it were displayed at a great distance from the latter.

Here, this combiner 20 is preferably arranged in the passenger compartment of the motor vehicle, between the windshield 1 of the vehicle and the eyes of the driver. Alternatively, the combiner could be formed by the windshield itself.

As shown in FIG. 3, the combiner 20 comprises a transparent plate 21 mounted in a support 29.

The transparent plate 21 forms a semi-reflective plate. Here, it is in practice an injected piece of polycarbonate, which is curved so as to enlarge the size of the image produced by the image generation unit 11 to present a virtual image Img (seen by the driver) of large size.

This transparent plate 21 has been treated to present on the front face a semi-reflective coating and to present on the rear face an anti-reflection coating.

In this way, the combiner 20 can reflect the image formed by the image generation unit 11.

Here, and it is precisely the object of the present invention, the head-up display 10 comprises additional technical means, which allow the driver to display information other than that formed by the image generation unit 11. .

Thus, according to a particularly advantageous characteristic of the invention, the head-up display 10 comprises, on the one hand, a waveguide in which is provided a pattern visible from the front of the waveguide, and, on the other hand, at least one light source adapted to illuminate the pattern by the side of the waveguide.

It is recalled in this regard that a waveguide is an element which serves to guide light waves by keeping them confined by the total reflection properties of light at a separation surface of two backgrounds of indices. different.

Here, this waveguide is in the form of a transparent plate, perfectly flat or slightly curved. It thus has two main faces front and rear, and a side edge.

The light source is then turned towards the lateral edge of this waveguide, so as to illuminate the interior thereof. The front of the waveguide is furthermore defined as being situated on the side of one of the two main faces of the transparent plate.

As will be described in more detail later in this discussion, this waveguide may be integrated in the combiner 20 (the case of Figure 3) or it may be placed against the screen 11A (Figure 4).

In the remainder of this disclosure, the term "pattern" will be used to designate any element integrated in the waveguide so as to allow information to be displayed in the driver's field of vision. Such a pattern may for example be in the form of the symbol of a warning light (battery indicator, fuel, oil pressure, brake, ...). Alternatively, it may be in the form of a sign, or a message.

The pattern is formed in the waveguide, so as to form a pointwise obstacle to the passage of light, which allows a part of the light to emerge through one of the main faces of the waveguide, in a given direction (forward). The shape of each pattern is then provided to show, on one of the main faces of the waveguide, a particular information. As it appears in FIGS. 3 and 4, the pattern 22; 42 is in the form of a danger sign. Alternatively, it may of course have a different shape.

Pattern 22; 42 provided in the waveguide can be obtained in different ways. As a first example, it may be provided to engrave point by point or silkscreen pattern 22; 42 on the surface of the waveguide. As shown in Figure 3, the risk is then that the side of the pattern 22 located closest to the light source 30 is brighter than the rest of the pattern 22, which at best will be unsightly, and at worst will not allow the driver to perceive the whole pattern 22.

It will then be possible to refine the etching or screen printing on the side of the light source, so as to obtain a uniform illumination of the pattern seen by the driver. As a second example, the pattern 22 may be formed by microstructures provided inside the waveguide. These microstructures will then form an "optical element light guide" (or "LOE" of the English "Light-Guide Optical Element"). As a third example, a diffractive optical element DOE ("diffractive optical element") may be used. It will be possible in particular to create a structure using the principle of the Bragg grating, that is to say a structure in which alternate layers of two different refractive index materials. Thanks to this structure, it will be possible to actively control this diffractive optical element DOE, so as to display patterns of different shapes.

Whatever the method used, controlling the light source will illuminate or make invisible the pattern provided in the waveguide.

As briefly mentioned above, it will be possible to consider integrating the waveguide with the head-up display 10 in two different ways.

The first way, illustrated in FIG. 4, will be to place the waveguide 40 in support against or at a reduced distance from the screen 11A, so that the image of the pattern is projected into the driver's field of vision. via the projection optical assembly 12.

For example, it is possible to provide that the waveguide acts as a protective glass 11B.

In the event that a protective glass 11 B is used, the waveguide 40 may instead be placed against this protective glass 11 B. It will be noted here that the use of such a protective glass 11B is not mandatory, since the whole is placed in a cavity that already protects it.

Thus, it will be possible to place the waveguide opposite the screen 11A with respect to the protective glass 11 B, so that its installation does not require any modification of the architecture of the head-display. high 10.

As shown in Figure 4, the waveguide 40 may instead be placed between the screen 11A and the protective glass 11 B, to be located closer to the screen 11A and be protected by the protective glass 11 B.

The pattern 42 will then be located on the side of the waveguide 40, but away from the edge of the waveguide.

The light source 30 will be located on the edge of the waveguide 40. The advantage of the technical solution illustrated in this FIG. 4 is that it modifies little the architecture of the existing head-up displays. Its only drawback is that the configuration of the display being designed to project generated images to the exact position of the screen 11A, the slight difference between the screen 11A and the waveguide 40 will cause a very slight blur on the image of the pattern seen by the driver. For this reason, the distance between the screen 11A and the waveguide 40 will preferably be less than 2 centimeters.

As shown in Figure 3, the second way is to use the transparent plate 21 of the combiner 20 as a waveguide. This technical solution can be used regardless of the embodiment of the head-up display 10 (Figure 1 or 2).

In this technical solution illustrated in FIG. 3, the pattern 22 will then be located in the transparent plate 21 of the combiner 20 and the light source 30 will be located on the edge of the combiner 20.

As shown in FIG. 3, the transparent plate 21 of the combiner 20 has a central zone Z1 through which the driver can observe the virtual image Img1, and a peripheral zone Z2 that is never illuminated by the generation unit. 11. Each pattern 22 is then more precisely located in this peripheral zone Z2, so that it can not be illuminated by the image generation unit 11 and therefore can not light up. by mistake. Here, there is provided a single pattern 22 but may provide a plurality of patterns distributed in the peripheral zone Z2.

As a variant, provision could however be made to place one or more patterns 22 in the central zone Z1 of the combiner 20.

Moreover, as shown in FIG. 3, here there is provided a single light source fixed to the combiner 20, formed by a light-emitting diode 30 adapted to emit light towards the pattern 22.

Note that this light source can be integrated in the support 29 of the combiner 20, which forms here a clamp for holding the transparent plate 21 by its lower edge. In this way, the light source will illuminate the pattern 22 from below. Alternatively, the light sources could be placed at a distance from the combiner 20, for example on the dashboard of the vehicle.

We can now describe a possible use of the head-up display 10 shown in the figures.

In all the embodiments of the invention, the image generation unit 11 is controlled in a conventional manner by the computer, so as to enable the driver to perceive elementary information such as the speed of the vehicle, the direction to follow, the state of the lighthouses ....

The light source 30 is however controlled by the computer to display a security information.

Here, this safety information will be the possible presence of an obstacle. This safety information will be obtained by the computer through detection means equipping the vehicle, such as for example cameras.

Then, in the absence of obstacles, the computer can control the extinction of the light source 30. In this way, the pattern 22 will remain invisible and will not interfere with the driving of the vehicle.

In the presence of an obstacle, the computer can control the ignition of the light source 30, which will cause the instantaneous illumination of the pattern 22. Thus, the attention of the driver (and possibly that of the passengers of the vehicle if the guide waveform is formed by the combiner 20) will be drawn to this obstacle, which will allow the driver to react more quickly.

Note that in case of failure of the image generation unit 11, the security information may continue to be displayed, since the operation of the light source 30 is independent of that of this generation unit. images 11.

The present invention is not limited to the embodiments described and shown, but the skilled person will be able to make any variant within his mind.

Thus, each pattern can be used to display information different from that described above. For example, a pattern may be used to signal a malfunction of the engine (overheating, ...), or a mechanical malfunction (problem of suspension, tire inflation, ...), or a malfunction of the system electric (ABS problem, problem of the image generation unit 11 ...).

FIG. 5 shows an alternative embodiment of the image generation unit 11 illustrated in FIG. 4. In this variant, the waveguide 40 has a size and / or a position such that protrudes from the screen 11 A. Its portion 41 which protrudes from the screen 11A has at least one second pattern 43 adapted to be illuminated by a light source 30.

More specifically here, as shown in Figure 5, the waveguide has a size such that it overflows the screen 11A on one side thereof. This waveguide has, on the part 41 which overflows the screen, a second pattern 43 which represents the symbol of the engagement of the parking brake of the vehicle. It is equipped with a second electroluminescent diode which makes it possible to illuminate this second pattern 43, independently of the illumination of the first pattern 42.

In this variant illustrated in FIG. 5, the projection optical assembly 12 must be provided in such a way that the image of this second pattern 43 can be projected into the driver's field of view, which may require a modification of the existing head-high display architecture. More precisely, this may necessitate enlarging the optical elements (folding mirror and combiner). However, this does not affect the shape of the main faces of these new optical elements, which reduces the design work. The major advantage of the solution illustrated in FIG. 5 is to provide in the waveguide a zone which makes it possible to display a large amount of information remotely from the information displayed by the screen 11A, so that this information does not occur. never overlap.

According to another variant of the image generation unit not shown in the figures, it could have been planned to place the waveguide next to the screen 11A and not at the front of the latter. The advantage of this solution is that the waveguide can be placed in such a way that the pattern is displayed without any blur in the driver's field of vision. The disadvantage of this solution is that here again, the position of the waveguide may require modifying the architecture of existing head-up displays so that the image of the pattern can be visible by the driver of the vehicle.

Claims (10)

Head-up display (10) for a motor vehicle, comprising an image generation device (11) and a combiner (20) arranged to receive the light beam emitted by the image generation device (11) and projecting the images generated into the field of vision of the driver of the motor vehicle, characterized in that it comprises: a waveguide (21; 40) which has two main faces and a lateral edge, and in which is provided a pattern (22; 42; 43), and - at least one light source (30) adapted to illuminate the pattern (22; 42; 43) by the lateral edge of the waveguide (21; 40) of such so that the light exits through one of the two main faces of the waveguide (21; 40). The head-up display (10) of claim 1, wherein each light source (30) comprises a light-emitting diode. The head-up display (10) according to one of claims 1 and 2, wherein said pattern (22; 42; 43) is etched in the waveguide (21; 40), away from the side edge of the waveguide (21; 40). The head-up display (10) according to one of claims 1 and 2, wherein said pattern (22; 42; 43) is formed by microstructures provided in the waveguide (21; 40) and forming a optical light guiding element (LOE). The head-up display (10) according to one of claims 1 and 2, wherein said pattern (22; 42; 43) is formed by diffractive optical elements (DOE) provided in the waveguide (21; 40). The head-up display (10) according to claim 5, wherein each diffractive optical element (DOE) is adapted to be actively controlled. 7. Head-up display (10) according to one of claims 1 to 6, wherein the combiner (20) comprises a semi-reflective transparent plate (21), which constitutes said waveguide. A head-up display (10) according to claim 7, wherein the combiner (20) has a display area (Z1) which receives the light beam emitted by the image generating device (11), and in which wherein each pattern (22) is located outside this display area (Z1). The head-up display (10) according to one of claims 1 to 6, wherein the image generation device (11) comprises a screen (11A) and the waveguide (40) is placed against the screen (11 A) or at a reduced distance therefrom. The head-up display (10) according to claim 9, wherein the distance between the waveguide (40) and the screen (11A) is less than 2 centimeters.