EP3662318A1

EP3662318A1 - Image-generating unit and head-up display equipped with such an image-generating unit

Info

Publication number: EP3662318A1
Application number: EP18750153.1A
Authority: EP
Inventors: Pierre Mermillod; Antoine-Camille PETRUCCI; François GRANDCLERC
Original assignee: Valeo Comfort and Driving Assistance SAS
Current assignee: Valeo Comfort and Driving Assistance SAS
Priority date: 2017-07-31
Filing date: 2018-07-31
Publication date: 2020-06-10
Also published as: FR3069655B1; WO2019025470A1; FR3069655A1

Abstract

The invention relates to an image-generating unit (10) comprising: a screen (12), by means of which an image to be displayed is generated; and a back-lighting device (11) including at least one light source (110) and an optical system (113, 114) that is configured to, from the light emitted by the source, produce a light beam (F) for lighting the screen. According to the invention, the image-generating unit furthermore comprises adjusting means (13) for modifying the orientation of the lighting light beam with respect to the screen, said adjusting means leaving said source stationary with respect to said optical system. The invention also relates to a head-up display equipped with such an image-generating unit.

Description

Imaqe generation unit and head-up display provided with such an image generation unit

TECHNICAL FIELD TO WHICH THE INVENTION REFERS

The present invention relates to an image generation unit, used in particular in a head-up display for a vehicle.

It relates more particularly to an image generation unit comprising:

a screen, at the level of which an image to be displayed is generated, and

a backlighting device comprising at least one light source and an optical system configured, from the light emitted by the source, to produce a light beam for illuminating the screen.

The invention also relates to a head-up display comprising such an image generation unit.

The invention applies particularly advantageously in the case where it is desired to adjust the position of an eye zone, at the level of which a user must place his eye in order to be able to visualize the image produced by the generating unit. picture.

BACKGROUND

For the driver of a motor vehicle, it is particularly comfortable to be able to display information relating to the operation of the vehicle, relating to a traffic lane facing the vehicle, or the like, without having to look away from this lane. circulation.

It is known for this purpose to equip the vehicle with a so-called head-up display comprising:

An image generation unit as described above, and

an optical projection system, for projecting the light beam coming from the screen of this image generation unit into a partially transparent plate disposed in front of the driver's eyes (made for example by means of the windshield of the vehicle), so as to form, by reflection by said blade, a virtual image of the screen.

The virtual image, comprising the information to be displayed, is then superimposed visually on the environment facing the vehicle.

In order for the driver to actually visualize this virtual image, his eyes must be located in an area of space, called here zone ocular, reached, at the output of the display, by at least a portion of the light beam emitted by the screen of the image generation unit (this ocular zone corresponds for example to the exit pupil of the display) .

In order for the display to be used by conductors of different sizes, it is desirable to equip it with a system making it possible to modify the position of this ocular zone.

For an image generation unit, in which the optical system of the backlighting device is made by means of a strongly convergent lens, also called a condenser, it is then known to move the light source with respect to the condenser by means of 'a motor.

But changing the internal arrangement of the backlight device also changes the uniformity and quality of the light beam for illuminating the screen.

OBJECT OF THE INVENTION

In this context, the present invention provides an image generation unit as defined in the introduction, further comprising adjustment means for changing the orientation of the illumination light beam with respect to the screen, said adjusting means leaving said source fixed with respect to said optical system.

These adjustment means make it possible to modify the angle of incidence formed between a mean direction of propagation of the illuminating light beam and a direction normal to this screen. Changing this angle of incidence has the effect of changing the average direction of the light beam emerging from the screen. When the image generation unit is installed in a head-up display, this then makes it possible to adjust the position of the ocular zone, reached at the output of the display by this light beam.

Moreover, the fact of leaving said fixed source with respect to said optical system makes it possible, during such an adjustment, for the light beam intended to illuminate the screen to retain the same characteristics, in particular a given level of illumination homogeneity. .

The adjustment means mentioned above may for example comprise a pivot link allowing a rotation of the entire backlight device relative to the screen.

The adjustment means may also comprise a prism arranged in the path of the illumination light beam, between the backlight device and the screen, the prism being rotatably mounted relative to the screen about an axis of rotation.

In both cases, the structure of the image generation unit is advantageously simple and compact. In particular, it is more compact than in the case of an orientation adjustment of the illumination light beam produced by means of a pivoting plane mirror.

Other nonlimiting and advantageous features of the image generation unit according to the invention, taken individually or in any technically possible combination, are as follows:

the axis of rotation of the prism is parallel to a ridge of the prism;

a distance separating the prism from the screen is less than a predetermined maximum deviation;

the illuminating light beam extends transversely over a given width, and said maximum deviation is equal to said width;

said maximum deviation is less than half said width;

- The optical system of the backlight device comprises a reflector by means of which is produced the light beam of illumination;

- the lighting beam is collimated;

- the screen is a liquid crystal display;

the screen comprises an active zone for the generation of the image, and said given width on which the illumination light beam extends transversely is less than one dimension of the active zone of the screen.

The invention also provides a head-up display comprising an image generation unit as described above.

It can be provided that the head-up display further comprises an optical projection system, for projecting the light beam coming from the screen of the image generation unit towards a partially transparent blade, so as to form, by reflection by said blade, a virtual image of the screen.

It can also be provided that the screen of the image generation unit is fixed relative to the projection optical system, even when the average direction of the illumination light beam is changed relative to the screen.

As the screen is fixed, a change in the average direction of the illumination light beam makes it possible, in the display, to adjust the position of the aforementioned ocular zone, while maintaining the virtual image (of the screen) fixed in the environment viewed through the blade.

It is optionally provided that the projection optical system is corrected by at least one optical aberration (such as geometric aberration), said correction being optimized for a given position of the screen with respect to the optical system. In this case, maintaining the fixed screen at this given position also makes it possible to maintain an optimal formation quality of the virtual image, even when the average direction of the illumination light beam is adjusted.

DETAILED DESCRIPTION OF AN EXEMPLARY EMBODIMENT

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 shows schematically a head-up display comprising an image generation unit which implements the teachings of the invention; and

- Figure 2 shows schematically, in more detail, the image generation unit of Figure 1;

- Figure 3 schematically shows an image generation unit according to another embodiment; and

- Figure 4 schematically shows an image generation unit according to yet another embodiment.

Figure 1 shows schematically a display 1 head high, intended to equip a vehicle, for example a motor vehicle, a train, a boat such as a barge, a tram or a bus.

The display 1 comprises an image generation unit for generating an image to be displayed.

Three embodiments of such an image generation unit 10; 10 '; 10 "are described herein with reference to FIGS. 2, 3 and 4, respectively.

The identical or corresponding elements of these different embodiments will be identified as far as possible by the same reference signs, and will not be described each time.

Whatever the embodiment considered, the generation unit 10; 10 '; 10 "comprises a screen 12, electrically controllable to generate the image to be displayed This screen 12 is for example made by means of a liquid crystal screen.

The display 1 also comprises, here, a projection optical system, for projecting the light beam F 'which emerges from the screen 12 to a partially transparent strip 2. The blade 2 then reflects at least part of this light beam to the eyes of a user of the display, here to the eyes of the driver of the vehicle.

The projection optical system here comprises a folding mirror 3 and a concave mirror 4, arranged in the optical path of the light beam F ', between the screen 1 1 and the partially transparent plate 2.

The partially transparent blade is formed here by the windshield of the vehicle (which bears the reference 2 in Figure 1). Alternatively, it could however be achieved by means of a dedicated component, called combiner, disposed between the windshield of the vehicle and the eyes of the driver.

The optical projection system forms, with the blade 2, a virtual image of the screen 12. This virtual image is formed relative to the blade 2, the opposite of the user.

As the blade 2 is partially transparent, it allows the user to visualize an environment, for example a road environment, through the blade. The virtual image is visually superimposed on this environment, so that the user can view it without distracting from the environment.

The display 1 may comprise, downstream of the screen 12, one or more optional optical components (not shown), such as a protection window or a polarizing filter.

Moreover, the projection optical system could comprise a different number of mirrors, or optical components. In particular, the projection optical system could comprise a single mirror.

In order for the user to be able to visualize the aforementioned virtual image, one of his eyes 5 must be located at an area of the space, called eye zone ZO (or eye box, literal translation of the word "eyebox""used in English), reached, after reflection by the blade 2, by the light beam F 'from the screen 12. This eye area is sometimes referred to as the Anglo-Saxon eye-box. The light beam F 'coming from the screen 12 has, immediately at the output of this screen, a mean direction of propagation x ₀ . This mean direction of propagation x ₀ corresponds to the direction of the main light ray emerging from the screen 12, or, otherwise formulated, to the mean direction defined by the radiation indicator at the output of the screen 12.

The image generation unit 10; 10 '; 10 ", which will be described in detail below, is configured to allow adjustment of this mean propagation direction x ₀ (or, otherwise formulated, a setting of the orientation of the light beam F 'coming out of the screen). this direction makes it possible to move the ocular zone ZO, and to bring it thus vis-à-vis one of the eyes of the user.

Thanks to this adjustment possibility, users of different sizes are able to view the virtual image produced by the display (with appropriate adjustment). This setting also makes the display compatible with different height settings of the driver's seat.

In each of the embodiments described herein, the image generation unit 10; 10 '; 10 "is more precisely configured to allow this adjustment of the orientation of the light beam F 'coming out of the screen 12, while leaving this screen 12 fixed with respect to the projection optical system (in terms of position as well as orientation).

As the screen is fixed relative to the projection optical system, the virtual image of the screen is formed in the same position, in the environment facing the vehicle, regardless of the position setting of the eye area.

This arrangement is particularly interesting when, as here, the display 1 is configured to operate in a so-called augmented reality mode in which the elements to be displayed, for example a light line for underlining or materializing a running lane border, must superimpose on given elements of the environment viewed through the blade 2.

Moreover, the concave mirror 4 of the projection optical system is corrected here with at least one optical aberration, such as a geometric aberration. This correction is optimized for a given position and orientation of the screen 12. It is therefore particularly interesting, in terms of the quality of formation of the virtual image, that, as here, the screen remains positioned at this position. given and retains said given orientation. With respect to what has been described above, it could alternatively be envisaged that the projection optical system be omitted, the image generation unit then being oriented so as to directly direct the light beam coming from the screen towards the partially transparent blade made by means of a combiner. In the context of this variant, it can then be provided that, when the orientation of the light beam coming out of the screen is changed, the screen nevertheless remains fixed (in terms of position as well as orientation) with respect to to the combiner.

The different embodiments of the image generation unit 10; 10 '; 10 "of the display 1 which has just been presented can now be described in more detail with reference to FIGS. 2 to 4.

In each of these embodiments, the image generation unit 10; 10 '; 10 "comprises, in addition to the screen 12 mentioned above, a backlighting device 1 1 comprising:

at least one source of light, here several, and

an optical system configured, from the light emitted by these sources 1 10, to produce a lighting light beam F of the screen 12.

The light sources 1 10 are made here by means of light-emitting diodes. The optical system comprises a reflector 1 13, and, optionally, a diffuser 1 14.

The reflector comprises reflecting lateral walls shaped, by reflection, to direct the light emitted by the sources 1 10 in the same direction x given. The reflector thus makes it possible to collimate the light emitted by the sources 1 10.

The diffuser 11, made for example by means of a film having a smooth face and an opposite grained face, diffuses the light that it receives into a cone of diffusion of reduced angular aperture, for example less than 30 degrees. Alternatively, one could use a non-conical diffusion, but more important in one direction than in the other, for example a diffusion 20 ° x 40 ° (diffusion in a solid angle of width 20 ° in a first direction and width 40 ° in a second direction perpendicular to the first direction).

As the reflector 1 13 produces a parallel beam of light rays, and the diffusion cone of the diffuser 1 14 is not very open, the illumination light beam F finally delivered by the backlighting device 1 1 is generally collimated, c 'i.e. formed of substantially light rays parallel to each other.

Moreover, the reflective walls of the reflector 1 13 are shaped here so that the illumination light beam F has the most uniform light intensity possible (in a section of this beam). The diffuser 1 14 further improves the homogeneity of the light intensity within this beam.

The backlight device 1 1 also comprises a printed circuit board 1 1 1 for mounting and power supply sources 1 10, and means for discharging the thermal energy released by these sources 1 10, such only cooling fins 1 12.

Remarkably, the image generation unit 10; 10 '; 10 "comprises adjustment means for modifying the orientation of the illumination light beam F with respect to the screen 12, these adjustment means leaving the sources 1 10 fixed with respect to the optical system of the backlighting device.

The mean direction x, of the illumination light beam F, the orientation of which is modified by the adjustment means, is the average direction presented by this light beam immediately upstream of the screen 12 (that is to say just before the screen 12, from the point of view of the direction of propagation of this light beam). The adjustment means thus allow a modification of the angle of incidence i ₂ formed between the mean direction x, of the illumination light beam F, and a direction normal to the screen 12.

However, the average direction xo of the light beam F 'coming out of the screen 12 depends directly on the average direction x, the illumination light beam F incident on this screen. Here, these two directions x, and x ₀ are even identical (the liquid crystal screen does not deviate the light beam passing through it).

The adjustment means of the image generation unit 10; 10 '; 10 "thus make it possible to modify the mean direction x ₀ of the light beam F coming out of the screen 12, and thus to modify the position of the ocular zone ZO with respect to the display 1.

Since the sources 1 10 remain fixed with respect to the optical system of the backlighting device 1 1, during such an adjustment, the illumination light beam F advantageously retains the same characteristics, in particular its level of homogeneity. lighting, which has been optimized here thanks to shape of the reflector 1 13.

It will also be noted that the image generation unit 10; 10 '; 10 "actually makes it possible to modify the orientation of the average direction x ₀ of the light beam F 'which leaves the screen 12, while keeping the screen 12 fixed with respect to the display 1 (which, as explained above , is particularly interesting in practice).

In the first embodiment of the image generation unit 10, shown in FIG. 2, the adjustment means of the image generation unit 10 comprise a prism 13 disposed in the path of the light beam of FIG. illumination F, between the backlighting device 1 1 and the screen 12.

The prism 13 deflects the illuminating beam of illumination F. Thus,

the mean direction x of the illumination light beam F at the exit of the prism 13 (which corresponds to the mean direction of this beam at the input of the screen 12), and

the mean direction x of the illumination light beam F at the input of the prism 13 (which corresponds to the average direction of this beam at the output of the backlighting device 1 1)

form between them a deflection angle D.

The prism 13 is rotatably mounted relative to the screen 12 about an axis of rotation z. It has an inlet face 131 and an outlet face 132 defining between them a stop 133. The axis of rotation z of the prism is parallel to this stop 133 (that is to say parallel to the generatrix of the prism).

A rotation of the prism 13 around its axis of rotation z modifies the angle of incidence formed between the mean direction x of the illumination light beam F incident on the prism 13, and a direction normal to the entry face 131 of the prism.

However, the deflection angle D introduced by the prism 13 depends on this angle of incidence.

A rotation of the prism 13 around its axis of rotation z (shown schematically by the arrow FI of FIG. 2) thus makes it possible to modify the deflection angle D, and thus to adjust the mean direction x, of the light beam of FIG. F lighting incident on screen 12.

The prism 13 is formed for example of a transparent plastic material, to reduce its cost, its weight and its fragility compared to a glass prism. Here, the prism is more precisely formed of a material of the polymethyl methacrylate (PMMA) type, whose refractive index n is equal, on average over all wavelengths of the visible, to about 1, 5 . Alternatively, it could be a transparent polycarbonate, or a cyclic olefin polymer or copolymer (such as Zeonex). An antireflection treatment may be applied on the entry face 131 and the exit face 132 of the prism 13, so that the introduction of the prism into the path of the illumination light beam only induces a minimal power loss for this beam.

The aperture angle a of the prism 13, formed between its input faces 131 and exit 132, may for example be between 8 degrees and 30 degrees. It is here equal to 24 degrees.

The manner in which the different angular positions that the prism 13 can be determined is presented now.

It is desired that the rotation of the prism makes it possible to move the ocular zone ZO over a given distance, upwards or downwards, with respect to a reference position of this ocular zone. This distance d is here equal to 6 centimeters, to allow the position of the ocular zone to be adapted to a wide range of users having different sizes.

To obtain this range of displacement of the ocular zone, it is necessary to be able to vary the angle β, formed between a reference direction x _re t and the mean direction x ₀ of the light beam F 'coming out of the screen 12, between two extreme angles + max and - max (this angle β is here equal to the angle of incidence i ₂ of the illumination light beam F on the screen 12).

Given the optical lever arm between the screen 12 of the image generation unit 10 and the eye zone ZO, which here measures approximately 1 meter, these extreme angles + max and - max are here + 4 degrees and - 4 degrees.

Two extreme angular positions of the prism 13 are then determined, so that:

in one of these extreme angular positions, the illumination light beam F comes out of the prism with a mean direction x, forming an angle

+ max with reference direction x _ref , and

in the other of these extreme angular positions, the illumination light beam F comes out of the prism with a mean direction x, making an angle - max with the reference direction x _ref . Here, these two extreme angular positions of the prism correspond to an angle of incidence, respectively equal to 0 degrees, and 20 degrees. A rotation amplitude of the 20 degree prism is therefore necessary here to obtain the desired displacement amplitude of the ocular zone Z0 (here 60 mm).

It can be provided that the prism 13 is movable continuously, in rotation about its axis of rotation z, between these two extreme angular positions. It can also be expected that it can occupy a number of discrete angular positions, for example the number of 20, between these two extreme angular positions.

As the illumination light beam F coming from the backlighting device 11 is collimated, the various light rays of this beam are incident on the prism 13 substantially with the same angle of incidence H, and are thus deflected by the prism of the same deviation angle D.

Moreover, because the prism 13 is slightly spaced from the screen 12, a change in the x direction of the illumination light beam F coming out of the prism 13 causes a slight displacement of the area of the screen 12 illuminated by this beam.

To minimize this displacement, provision is made here to arrange the screen at a distance e the prism less than a maximum deviation e _ma x predetermined.

This distance e is for example equal to the distance separating the prism from the screen where they are closest to each other.

For example, the maximum deviation e _ma x may be equal to a transverse width l_F presented by the illumination light beam F. Given the moderate values of the extreme angles + max and - max, the (lateral) displacement of the the screen 12 illuminated by this beam remains negligible compared to the extent of this illuminated area. To further reduce this displacement, it can however be expected that this maximum gap e _ma x is equal to half the transverse width L _F of the light beam.

It can also be provided that the screen is disposed downstream of the prism without an optical component intermediate between the prism and the screen, which allows positioning of the prism 13 as close to the screen 12 (so as not to overload FIG. this figure is not represented on the scale, and the distance separating the prism 13 from the screen 12 is exaggerated in relation to the reality).

Even if the lateral displacement of the illumination light beam F by 12 is thus reduced, the backlighting device 1 1 is such that, here, the transverse width L _F on which this light beam extends (in the plane of the screen) is less than one dimension L ₂ of an active area of the screen.

This active area of the screen corresponds to the region of this screen at any point from which it is possible to generate an image. This is the area occupied by the pixels of the screen (electrically controllable). The dimension L- | ₂ of this active zone, greater than the transverse width L _F of the beam, corresponds to the width of this active zone, in the plane of the screen 12, perpendicular to the axis of rotation z of the prism.

Since this active zone is wider than the area of the screen 12 illuminated by the illumination light beam F, it is possible here to generate an image at this illuminated zone, even when this illuminated zone is moving relative to the screen because of the orientation adjustment of the illumination light beam.

Moreover, as the illumination light beam is wide, it is mainly at the periphery of this light beam that the chromatic dispersion introduced by the prism 13 modifies the chromatic properties of the beam. To overcome these chromatic changes, one can for example diaphragm the light beam of illumination by an opening of suitable size to eliminate a given peripheral area light beam. This opening may be located in the image generation unit 10 itself, or downstream of it, in the display 1.

In the second embodiment of the image generation unit 10 ', shown in FIG. 3, the means for adjusting the orientation of the illumination light beam F comprise a pivot connection allowing rotation of the assembly. of the backlighting device 1 1 relative to the screen 12, rather than the prism described above (this prism is then omitted).

In this second embodiment, the image generation unit 10 'is configured to allow an amplitude of rotation of the backlighting device 1 1 of plus or minus max, that is to say, plus or minus 4 degrees ( the extreme angle max has been defined above) about the axis of rotation z 'defined by this pivot connection.

This axis of rotation z 'is parallel to the screen 12 of the image generation unit 10'. As shown in FIG. 3, this axis of rotation z 'is situated at the level of the screen: it extends in the plane defined by an exit face of this screen. Positioning the axis of rotation z 'of the backlighting device 1 1 at the level of the screen 12 makes it possible to effectively reduce the displacement of the illuminated area of the screen, generated by a change in the orientation of the light beam. F. lighting

As previously, it is possible to provide that the backlighting device 1 1 is disposed as close as possible to the screen 12, and that it is configured so that the lighting light beam extends transversely over a width L _F less than the dimension L- | ₂ above of the active area of the screen 12.

In the third embodiment of the image generation unit 10 ", shown in FIG. 4, the means for adjusting the orientation of the illumination light beam F comprise at the same time:

- The prism 13, rotatable, which was presented above in the description of the first embodiment, and

a pivot connection of axis z ', allowing a rotation of the whole of the backlight device 1 1 relative to the screen 12, as presented above in the description of the second embodiment.

The change in orientation of the illumination light beam F is then obtained by combining a rotation of the premium 13 around its axis of rotation z, and an overall rotation of the backlight device 11 around its axis of rotation. z '. Combining these two rotations makes it possible, for an orientation modification of the given illumination light beam F, to reduce the corresponding rotational amplitudes for the prism and the backlighting device.

Because of these reduced rotational amplitudes, the orientation change of the illumination light beam F can be obtained in a shorter time than when only a pivoting of the prism, or backlighting device is employed.

Thus reducing the time required to change the orientation of the illumination light beam F by a given amount is particularly advantageous, especially in the case of a real-time monitoring of the position of the driver's eyes, that is to say ie when the position of the ocular zone is slaved so as to coincide, at each moment, with the position of the eyes of the driver.

Claims

1. An image generating unit (10; 10 '; 10 ") comprising:

a screen (12) by means of which an image to be displayed is generated, and a backlighting device (1 1) comprising at least one source

(1 10) of light and an optical system (1 13, 1 14) configured, from the light emitted by the source (1 10), to produce a lighting beam (F) of the screen (12)

characterized in that it further comprises adjusting means (13) for changing the orientation of the illuminating light beam (F) relative to the screen (12), said adjusting means (13) leaving said source (1 10) fixed with respect to said optical system (1 13, 1 14).

An image generating unit (10 '; 10 ") according to claim 1, wherein said adjusting means comprises a pivot link (ζ') permitting rotation of the entire backlighting device (11). ) relative to the screen (12).

An image generating unit (10; 10 ") according to one of claims 1 and 2, wherein said adjusting means comprises a prism (13) disposed in the path of the illumination light beam (F), between the backlighting device (1 1) and the screen (12), the prism (13) being rotatably mounted relative to the screen (12) about an axis of rotation (z).

An image generating unit (10; 10 ") according to claim 3, wherein the axis of rotation (z) of the prism (13) is parallel to an edge (133) of the prism.

An image generating unit (10; 10 ") according to one of claims 3 and 4, wherein a distance (e) separating the prism (13) from the screen (12) is less than a maximum deviation predetermined.

An image generation unit (10; 10 '; 10 ") according to one of claims 1 to 5, wherein the optical system of the feedback device illumination (1 1) comprises a reflector (1 13) by means of which the illumination light beam (F) is produced.

An image generating unit (10; 10 '; 10 ") according to one of claims 1 to 6, wherein the illuminating light beam (F) is collimated.

An image generating unit (10; 10 '; 10 ") according to one of claims 1 to 7, wherein the screen (12) is a liquid crystal screen.

An image generation unit (10; 10 '; 10 ") according to one of claims 1 to 8, wherein the screen (12) comprises an active area for generating the image, and wherein the illumination light beam (F) extends transversely over a width (L _F ) smaller than one dimension (L- | ₂ ) of the active area of the screen (12).

Head-up display (1) comprising an image generation unit (10; 10 '; 10 ") according to one of claims 1 to 9.

1 1. A head-up display (1) according to claim 10, further comprising a projection optical system (2, 3) for projecting the light beam (F) from the screen (12) of the image generation unit ( 10; 10 '; 10 ") to a blade (2) partially transparent so as to form, by reflection by said blade (2), a virtual image of said screen (12), and wherein said screen (12) is fixed by relative to the projection optical system (2, 3).