Head-up display device

Abstract

The invention relates to a head-up display device comprising an image generation unit (10) configured to produce a light beam, an optical system configured to transmit the light beam towards a partially reflective plate (16), and a control unit. The optical system comprises a mirror (6) which is movable between at least a first position, in which the light beam is transmitted towards the partially reflective plate (16) in a first direction, and a second position, in which the light beam is transmitted towards the partially reflective plate (16) in a second direction that is different from the first direction. The control unit is configured to control the image generation unit (10) to modulate the light beam in accordance with a first image when the movable mirror (6) is in the first position, and to modulate the light beam in accordance with a second image that is different from the first image when the movable mirror (6) is in the second position.

Description

[0001] Description

[0002] Title of the invention: Head-up display device

[0003] Technical field of the invention

[0004] The present invention relates to the technical field of head-up displays. It relates in particular to a head-up display device.

[0005] State of the art

[0006] We have already tried to give an illusion of depth to virtual images produced by a head-up display device.

[0007] The proposed solutions use either autostereoscopic screens, as in the article "Automotive augmented reality 3D head-up display based on light-field rendering with eye-tracking" (J. Lee et al., in Optics Express Vol. 28, No. 20, pp. 29788-29804, 2020), or holographic techniques, as in the article “Realizing automotive holographic head up displays”, by J. Christmas and N. Collings, SID Symp. Dig. Tech. 47(1), 1017-1020 (2016).

[0008] Solutions using autostereoscopic displays do not achieve sufficient resolution and quality of the virtual image. Solutions using holography, on the other hand, introduce artifacts into the virtual image, require significant space, and are expensive.

[0009] Presentation of the invention

[0010] In this context, a head-up display device is proposed comprising an image generation unit configured to produce a light beam, an optical system configured to transmit the light beam towards a partially reflective blade, and a control unit, characterized in that the optical system comprises a movable mirror between at least a first position, in which the light beam is transmitted towards the partially reflective blade in a first direction, and a second position, in which the light beam is transmitted towards the partially reflective blade in a second direction distinct from the first direction, and in that the control unit is configured to command the image generation unit to modulate the light beam according to a first image when the movable mirror is in the first position.and to modulate the light beam according to a second image distinct from the first image when the moving mirror is in the second position. Such a head-up display device can thus transmit light beams corresponding to two distinct images in two different directions, allowing each eye of the user to view a particular image and thus producing an impression of depth through stereoscopic effect.

[0011] For example, we can predict that the exit pupil of the optical assembly formed by the optical system and the partially reflecting plate corresponds to a first part of an ocular region when the movable mirror is in the first position, and to a second part of the ocular region, distinct from the first part, when the movable mirror is in the second position. We can then predict in this case that one of the user's eyes will be located at the level of the first part and that the user's second eye will be located at the level of the second part.

[0012] The optical system is configured, for example, to transmit a main ray of the light beam towards a first point located on the partially reflective blade when the movable mirror is in the first position, the first point where the main ray of the light beam is reflected towards a first positioning region of a user's eye, and to transmit the main ray of the light beam towards a second point located on the partially reflective blade when the movable mirror is in the second position, the second point where the main ray of the light beam is reflected towards a second positioning region of the user's other eye.

[0013] In some embodiments, particularly when the head-up display is fitted to a vehicle, the first point and the second point may be horizontally offset from each other.

[0014] The optical system can be configured so that the light beam transmitted towards the partially reflective plate sweeps across an area on the partially reflective plate that includes the first point and the second point during the movement of the moving mirror over a period of time shorter than the duration of retinal persistence.

[0015] According to one possible embodiment, the head-up display device may include an eye-tracking system configured to locate the first region and the second region; the control unit may then be configured to command the image generation unit to turn off the light beam when the movable mirror is in a set of positions distinct from the first and second positions.

[0016] According to another embodiment, the first and second regions are respectively intended for positioning one and the other eye of the user in the usual operating configuration (for example, when the user is seated in the driver's seat of a vehicle). The position of the first and second regions can then be adjusted, for example, simultaneously by tilting the concave mirror mentioned later (which amounts to moving the entire ocular region).

[0017] The moving mirror is, for example, configured to perform a rotational movement. In this case (particularly when the moving mirror is polyhedral, as explained later), a rotational speed greater than 1 revolution per second can be expected, for example, between 2 revolutions per second and 20 revolutions per second.

[0018] In one possible embodiment, the movable mirror can have a plurality of (flat) facets. All of these facets can then surround the axis of rotation of the movable mirror. Furthermore, the movable mirror can, in this case, have between 4 and 12 facets.

[0019] In some embodiments, the center of rotation of the moving mirror and the virtual image produced are conjugated by the optical assembly formed by the optical system and the partially reflecting plate.

[0020] This can be the case, in particular, when the image generation unit is of the laser scanning type.

[0021] According to other possible embodiments, the image generation unit includes a diffuser from which the light beam emerges.

[0022] We can then predict that the diffuser and the virtual image produced are conjugated by the optical assembly formed by the optical system and the partially reflective blade.

[0023] In other embodiments, the image generation unit includes a liquid crystal display configured to produce the light beam.

[0024] In the embodiments described below, the optical system further includes a mirror (for example, concave) interposed in the optical path of the light beam between the movable mirror and the partially reflecting blade. 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.

[0025] Detailed description of the invention

[0026] Furthermore, various other features of the invention become apparent from the attached description made with reference to the drawings which illustrate non-limiting embodiments of the invention and where:

[0027] [Fig. 1] represents, in side view, the main elements of an example of a head-up display device according to the invention;

[0028] [Fig. 2] is a schematic, top-view representation of the head-up display device of Figure 1 when a movable mirror is in a first position;

[0029] [Fig. 3] is a schematic, top-view representation of the head-up display device of Figure 1 when the movable mirror is in a second position;

[0030] [Fig. 4] represents the positioning of a light beam at the level of an ocular region when the movable mirror is in the first position;

[0031] [Fig. 5] represents the positioning of a light beam at the level of the ocular region when the movable mirror is in the second position; and

[0032] [Fig. 6] schematically represents the head-up display device of Figure 1 with a particular embodiment of an image generation unit.

[0033] Figure 1 shows an example of a head-up display device according to the invention. Such a head-up display device can be mounted in a vehicle (for example, a motor vehicle).

[0034] The head-up display device in Figure 1 includes a control unit 2, an optical system 4 and an image generation unit 10.

[0035] The image generation unit 10 and the optical system 4 (and here the control unit 2) are housed (precisely: enclosed) in a casing 12.

[0036] The optical system 4 includes a movable mirror 6 and, here, a concave mirror 8. As can be seen in particular in figures 2 and 3 (see also figure 6), the movable mirror 6 here includes a plurality of planar facets 62. In the example described, the movable mirror 6 is polyhedral in shape and has two main polygonal faces (essentially horizontal in the position of use of the head-up display device in the vehicle), each planar facet 62 connecting one side of the polygon delimiting one main face and a corresponding side of the polygon delimiting the other main face.

[0037] In other words, the flat facets 62 extend over the periphery of the movable mirror 6, here over the entire perimeter of the movable mirror 6 (the set of flat facets 62 thus forming the edge of the polyhedral movable mirror 6).

[0038] The polyhedral movable mirror used can include, for example, between 4 and 12 facets 62 (the polygons delimiting the principal faces including, in other words, between 4 and 12 sides).

[0039] Alternatively, another type of moving mirror can be used, such as a galvanometer (mirror-type) or a scanning mirror. 1 (according to the Anglo-Saxon term).

[0040] The image generation unit 10 is configured to produce a light beam L which is transmitted by the optical system 4 through a window 14 provided in the housing 12 and towards a partially reflective blade 16, where the light beam is reflected towards an eye of the user (here the driver of the vehicle), as explained in more detail later.

[0041] The partially reflective blade 16 is here the vehicle's windshield; however, it could alternatively be a dedicated blade (sometimes called a "combination blade"). 1 ') .

[0042] Different types of image generation units can be used, as also explained later.

[0043] As can be seen in Figure 1, the light beam L is reflected, within the optical system 4, by the movable mirror 6 (here specifically by a facet 62 of the movable mirror 6).

[0044] In the example described, the light beam L (received from the image generation unit 10) is reflected by the movable mirror 6 (here by the relevant facet 62 of the movable mirror 6) towards the concave mirror 8, where the light beam is reflected towards the partially reflecting plate 16. As already indicated, after reflection on the concave mirror 8, the light beam passes through the window 14 before reaching the partially reflecting plate 16. In practice, the shape of the reflective surface of the concave mirror 8 can be optimized to reduce possible geometric aberrations.

[0045] The movable mirror 6 is driven in rotation around an axis of rotation X (here perpendicular to the main faces of the movable mirror 6 and / or essentially vertical in the position of use of the head-up display device in the vehicle) by a drive system (not shown) including for example an electric motor.

[0046] The rotation axis X passes through the center of the aforementioned polygonal principal faces. Thus, the facets 62 of the movable mirror 6 are arranged around the rotation axis X such that, during the rotation of the movable mirror 6, the different facets 62 of the movable mirror 6 successively pass in front of the image generation unit 10, i.e., successively receive the light beam L. In other words, in the case described here of a polyhedral movable mirror 6, the rotation of the movable mirror 6 is continuous (i.e., uninterrupted, for example at constant speed, throughout the operation of the head-up display device).

[0047] Furthermore, when each facet 62 passes in front of the image generation unit 10, its orientation (i.e. for example the direction normal to the facet 62 concerned) changes due to the rotational movement of the movable mirror 6 so that the light beam reflected by the facet 62 sweeps across a set of directions.

[0048] Figures 2 and 3 show the path of a principal ray (or "chief ray" according to the Anglo-Saxon term) of the light beam L respectively in a first position of the movable mirror 6 and in a second position of the movable mirror 6.

[0049] In the first position of the movable mirror 6 (represented in figure 2), the main ray of the light beam is transmitted (after reflection on the facet 62 concerned and here after reflection on the concave mirror 8) in a first direction, precisely in the direction of a first point P1 of the partially reflective plate 16, where the main ray of the light beam is reflected in the direction of a first region where a first eye 01 of the user is located.

[0050] In the second position of the movable mirror 6 (represented in figure 3), the main ray of the light beam is transmitted (after reflection on the same facet 62 and here after reflection on the concave mirror 8) in a second direction, precisely in the direction of a second point P2 of the partially reflective plate 16, where the main ray of the light beam is reflected in the direction of a second region where the second eye 02 of the user is located.

[0051] As can be seen in Figures 2 and 3 (which are top views), in the case described here where the user is the driver of the vehicle (seated in a driver's seat and in driving position), the first point P1 and the second point P2 are horizontally offset from each other.

[0052] Thanks to the movement of the movable mirror 6 between its two positions illustrated respectively in figures 2 and 3 (and thus to the resulting change in orientation of the light beam), the exit pupil of the optical assembly formed by the optical system 4 and the partially reflective plate 16 moves between a first part TT1 (corresponding to the first eye 01) of the ocular region R (or "eyebox" according to the commonly used Anglo-Saxon terminology) when the movable mirror 6 is in the first position and to a second part TT2 (corresponding to the second eye 02) of the ocular region R, distinct from the first part TT1, when the movable mirror 6 is in the second position (see figures 4 and 5 and the explanations given below).

[0053] When the moving mirror is a galvanometer or a scanning mirror as described above, the single reflective surface of the moving mirror oscillates between a first position, in which the main ray of the light beam is transmitted in the direction of the first point P1, and a second position, in which the main ray of the light beam is transmitted in the direction of the second point P2.

[0054] In some embodiments, the control unit 2 can control the movement of the movable mirror 6 and determine, via the control law, the position of the movable mirror 6.

[0055] In other embodiments, a sensor (not shown) connected to the control unit 2 measures the position of the movable mirror 6.

[0056] In both cases, the control unit 2 is thus able to control the image generation unit 10 according to the position of the moving mirror 6.

[0057] Specifically, the control unit 2 commands the image generation unit 10 to modulate the light beam according to a first image when the movable mirror 6 is in the first position mentioned above (in which the main ray of the light beam is transmitted in the direction of the first point P1 and reaches, after reflection at the level of this first point P1, the first eye 01), and to modulate the light beam according to a second image distinct from the first image when the movable mirror 6 is in the second position mentioned above (in which the main ray of the light beam is transmitted in the direction of the second point P2 and reaches, after reflection at the level of this second point P2, the second eye 02).

[0058] Thus, the control unit 2 can control the viewing of this first image by the first eye 01 and the viewing of this second image by the second eye 02, which allows the user to have an impression of depth by stereoscopic effect.

[0059] When, for example, we want to display 30 three-dimensional views (each corresponding to two stereoscopic images) per second using a movable mirror with 6 flat facets (i.e., hexagonal main faces), the movable mirror 6 is then rotating around the X axis at a speed of 5 revolutions per second.

[0060] In another embodiment where we want to display 30 three-dimensional views per second with a movable mirror having 12 flat facets (dodecagonal principal faces), the movable mirror 6 is rotating around the X axis at a speed of 2.5 revolutions per second.

[0061] In general, in the described embodiment where the movable mirror 6 is polyhedral and has a plurality of planar facets 62, the rotation speed of the movable mirror 6 is between 2 revolutions per second and 20 revolutions per second (and is therefore greater than 1 revolution per second).

[0062] In the example described here, during the passage of a given facet 62 in front of the image generation unit 10 and over a period of time less than the duration of retinal persistence, the light beam transmitted towards the partially reflective plate 16 sweeps, on this partially reflective plate 16, a zone Z including the first point P1 and the second point P2.

[0063] Figures 4 and 5 represent the positioning of the light beam (or, in other words, of the output pupil of the head-up display device) at the level of the eye region R respectively when the movable mirror 6 is in the first position (shown in figure 2) and in the second position (shown in figure 3). In practice, the position of the eye region R can be adjusted (in particular vertically, for example by tilting the concave mirror 8) so as to correspond to the intended position of the user's eyes 01, 02 (here when the user is seated in the driver's seat of the vehicle).

[0064] In order to foresee a possible movement of the user's eyes 01, 02 within the ocular region R, the control unit 2 can be designed to control the image generation unit 10 so as to modulate the light beam according to the first image for as long as the light beam reaches a first half D1 of the ocular region R (i.e. as long as the exit pupil is located in this first half D1 of the ocular region R), and so as to modulate the light beam according to the second image for as long as the light beam reaches the second half D2 of the ocular region R (i.e. as long as the exit pupil is located in this second half D2 of the ocular region R) (the first half D1 and the second half D2 being horizontally juxtaposed).

[0065] According to one possible variant, the head-up display device may include an eye-tracking system configured to locate the first region mentioned above (region where the first eye 01 is located) and the second region mentioned above (region where the second eye 02 is located).

[0066] In this case, the control unit 1 can further command the image generation unit 10 to turn off the light beam, during the scanning of the Z area, when the movable mirror 6 is in a set of positions distinct from the first position and the second position.

[0067] Thus, the image generation unit 10 effectively produces a light beam only when the movable mirror 6 is in the first position (or in a set of positions close to the first position), where the light beam is modulated according to the first image and reaches the first eye 01, and when the movable mirror 6 is in the second position (or in a set of positions close to the second position), where the light beam is modulated according to the second image and reaches the second eye 02, which makes it possible to limit the average electrical power consumed by the image generation unit 10.

[0068] In the various cases considered above, it is also possible to limit the opening of the exit pupil of the optical assembly formed by the optical system 4 and the partially reflective plate 16 by means of a diaphragm placed immediately downstream of the image generation unit or by providing, on the movable mirror 6, a reflective surface (here each facet 62) of suitable size.

[0069] According to one conceivable embodiment, the image generation unit 10 is a liquid crystal display, for example of the TFT type (for "Thin Film Transistor", i.e., with thin film transistors).

[0070] We can then predict that the screen of the image generation unit 10 and the virtual image produced (at a given instant) are conjugated by the optical assembly formed by the optical system 10 and the partially reflective plate 16.

[0071] According to another conceivable embodiment, schematically represented in Figure 6, the image generation unit 10 is of the laser scanning type (or "laserscan" according to the commonly used Anglo-Saxon term) and includes a beam forming module 102, a scanning unit 140 and an output optical component 106.

[0072] The optical output component 106 has a general plate shape and includes a front face 107 through which the beam L produced by the image generation unit 10 emerges and a rear face 108 opposite the front face 107.

[0073] As described above, the front face 107 here faces the movable mirror 6.

[0074] The beamforming module 102 typically comprises three monochromatic light sources, such as laser sources, whose respective (monochromatic) light beams are combined (e.g., using dichroic mirrors) to form a polychromatic light beam P (here laser) emitted from the beamforming module 102.

[0075] The scanning unit 104, made for example in the form of a microelectromechanical system (or MEMS for "MicroElectroMechanical System"), includes a movable mirror 105 arranged to receive the polychromatic light beam P produced by the beam forming module 102.

[0076] The scanning unit 104 is configured to vary the orientation of the movable mirror 105 (for example under the control of the control unit 2) so that the polychromatic light beam reflected by the movable mirror 105 sweeps across the rear face 108 of the output optical component 106.

[0077] During the scanning of the rear face 108 of the output optical component 106 by the polychromatic light beam (reflected by the movable mirror 105), the control unit 2 varies the respective light intensities of the monochromatic light sources so that the polychromatic light beam P has the color that is desired to be given to the point on the rear face 108 which receives the polychromatic light beam reflected at that instant (i.e. the color of the pixel corresponding to that point in the image to be displayed).

[0078] Thus, the light beam L produced (at the output of the front face 107 of the output optical component 106) during a scan period of the rear face 108 is modulated according to the image to be displayed (for the eye 01, 02 which receives the light beam according to the position of the movable mirror 6 at that instant), under control of the control unit 2. The scan period of the rear face 108 is significantly less than the duration of retinal persistence (since, as explained above, two distinct images, requiring two scan periods of the rear face 108 are displayed during the duration of retinal persistence) so that the user simultaneously perceives the different beams produced at the output throughout the scan of the rear face 108.

[0079] According to a first possible embodiment, the optical output component 106 is an exit pupil expander. 1' according to the commonly used Anglo-Saxon term), produced by means of a diffractive element.

[0080] When the beam incident on the rear face (or inlet face) 108 is collimated (here due to the use of laser sources as indicated above), the light beam L emerging from the front face (or outlet face) 107 of such an outlet pupil enlarger 106 is also collimated (but of dimensions greater than the beam incident on the rear face 108).

[0081] In this case, it is possible to foresee that the center of rotation X of the movable mirror 6 and the virtual image produced by the head-up display device are conjugated by the optical assembly formed by the optical system 4 and the partially reflective blade 16. Thus, the virtual image produced when the movable mirror 6 is in the first position (virtual image corresponding to the first image mentioned above), and the virtual image produced when the movable mirror 6 is in the second position (virtual image corresponding to the second image mentioned above) are located precisely in the same place, which improves the sharpness for the user of the three-dimensional object displayed (by combining the first image and the second image by stereoscopic effect, as explained above).According to a second possible embodiment, the output optical component 106 is a diffuser, made for example by means of a diffusing plate or a microlens array (or "microlens array" according to the Anglo-Saxon term).

[0082] In this case, we can predict that the output optical component 106 (here a diffuser) and the virtual image produced by the head-up display device are conjugated by the optical assembly formed by the optical system 4 and the partially reflective blade 16.

Claims

Demands

1. Head-up display device comprising an image generation unit (10) configured to produce a light beam (L), an optical system (4) configured to transmit the light beam towards a partially reflective blade (16), and a control unit (2), characterized in that the optical system (4) comprises a movable mirror (6) between at least a first position, in which the light beam is transmitted towards the partially reflecting plate (16) in a first direction, and a second position, in which the light beam is transmitted towards the partially reflecting plate (16) in a second direction distinct from the first direction, and in that the control unit (2) is configured to control the image generation unit (10) to modulate the light beam according to a first image when the movable mirror (6) is in the first position, and to modulate the light beam according to a second image distinct from the first image when the movable mirror (6) is in the second position.

2. Head-up display device according to claim 1, wherein an exit pupil of the optical assembly formed by the optical system (4) and the partially reflective blade (16) corresponds to a first part (TT1) of an ocular region (R) when the movable mirror (6) is in the first position and to a second part (TT2) of the ocular region (R), distinct from the first part (TT1), when the movable mirror (6) is in the second position.

3. Head-up display device according to claim 1 or 2, wherein the optical system (4) is configured to transmit a main ray of the light beam towards a first point (P1) located on the partially reflective blade (16) when the movable mirror (6) is in the first position, first point (P1) where the main ray of the light beam is reflected towards a first positioning region of one eye (01) of a user, and to transmit the main ray of the light beam towards a second point (P2) located on the partially reflective blade when the movable mirror (6) is in the second position, second point (P2) where the main ray of the light beam is reflected towards a second positioning region of the other eye (02) of the user.

4. Head-up display device according to claim 3, wherein the optical system (4) is configured so that the light beam transmitted towards the partially reflective blade (16) sweeps, on the partially reflective blade (16), an area (Z) including the first point (P1) and the second point (P2) during the movement of the movable mirror (6) over a period of time less than the duration of retinal persistence.

5. Device according to claim 3 or 4, comprising an eye tracking system configured to locate the first region and the second region, wherein the control unit (2) is configured to command the image generation unit (10) to turn off the light beam (L) when the movable mirror (6) is in a set of positions distinct from the first position and the second position.

6. Head-up display device according to any one of claims 1 to 5, wherein the movable mirror (6) is configured to perform a rotational movement.

7. Head-up display device according to claim 6, wherein the movable mirror has a plurality of facets (62).

8. Head-up display device according to claim 6 or 7, wherein the center of rotation of the movable mirror (6) and the virtual image produced are conjugated by the optical assembly formed by the optical system (4) and the partially reflective blade (16).

9. Head-up display device according to any one of claims 1 to 8, wherein the image generation unit (10) is of the laser scanning type.

10. Head-up display device according to claim 9 taken in dependence on any one of claims 1 to 7, wherein the image generation unit includes a diffuser (106) from the output of which the light beam (L) emerges.

11. Head-up display device according to claim 10, wherein the diffuser (106) and the virtual image produced are conjugated by the optical assembly formed by the optical system (4) and the partially reflective blade (16).

12. Device according to any one of claims 1 to 7, wherein the image generation unit (10) comprises a liquid crystal display configured to produce the light beam (L).

13. Device according to any one of claims 1 to 12, characterized in that the optical system (4) comprises a mirror (8) interposed on the optical path of the light beam between the movable mirror (6) and the partially reflecting blade (16).

Images