EP4260128A1

EP4260128A1 - Head-up display and folding mirror in such a display, method and mould for manufacturing such a display

Info

Publication number: EP4260128A1
Application number: EP21836411.5A
Authority: EP
Inventors: Armand Divine; François GRANDCLERC; Pierre Mermillod; Alexis Kleckner; Arnaud HUSSON
Original assignee: Valeo Comfort and Driving Assistance SAS
Current assignee: Valeo Comfort and Driving Assistance SAS
Priority date: 2020-12-09
Filing date: 2021-12-09
Publication date: 2023-10-18
Also published as: WO2022122875A1; FR3119029A1

Abstract

Disclosed is a head-up display (10) for displaying a virtual image (6) to an individual (4), comprising: - an image generation unit (7) capable of emitting a source light beam (9); and - an optical projection system (11) capable of forming, from the source of light beam (9), the virtual image in a field of vision of the individual, the optical projection system comprising: - a folding mirror (12) having a first surface, the first surface being a curved reflection surface facing the image generation unit in order to reflect the source light beam; and - an optical element (13) having a first surface and a second surface, the first surface being a curved, at least partially reflecting, optical surface turned towards the folding mirror in order to intercept the reflected light beam (14). The first surface of the folding mirror and the first or second surface of the optical element at least partially superimpose.

Description

DESCRIPTION

Title of the invention: Head-up display and folding mirror in such a display, process and mold for manufacturing such a display

Technical field to which the invention relates

The present invention generally relates to the field of the projection of information or images.

It relates more particularly to a head-up display intended to display a virtual image to an individual.

It also relates to a folding mirror integrated in such a head-up display.

Finally, it concerns a method for producing a head-up display as well as a mold designed for producing such a head-up display.

The invention applies in a particularly advantageous manner in driving assistance systems for motor vehicles.

Technology background

Vehicles equipped with a head-up display (“head-up display” or HUD in English) intended to display a virtual image to an individual are known, the head-up display comprising: an image generation unit adapted emitting a source light beam; and a projection optical system adapted to form, from the source light beam, the virtual image in a field of vision of the individual, the projection optical system comprising: a folding mirror having a first surface and a second surface , the first surface being a curved reflection surface facing the image generating unit to reflect the source light beam; and an optical element having a first surface and a second surface, the first surface being a curved optical surface, at least partially reflecting, and facing the folding mirror to intercept the reflected light beam.

This head-up display can be either a head-up display "on the windscreen" or a head-up display "to be combined". In the first case, the projection of the virtual image to the occupant of the vehicle is ultimately carried out by optical reflection on the windshield of the vehicle (in fact on its internal sheet).

In this particular case, the optical element of the projection system can be a "power mirror", with a non-planar first surface and treated with a highly reflective coating (silvering or other).

In the second case, the optical element is the combiner of the head-up display, i.e. a partially transparent blade which directly forms the virtual image to be displayed and through which the individual can see. this image.

In practice, the shape (geometry or surface equation) of the first surface of the optical element is determined according to: the size of the desired virtual image and the projection distance from the individual; the internal optical design of the head-up display (geometry of the folding mirror and of the image generation unit); and/or the geometry and inclination of the windshield of the vehicle (for the case on the windshield only).

This notably makes it possible to guarantee good image quality of the virtual image projected to the occupant.

Advantageously, the optical element is a “freeform” type optical part with a first reflecting surface whose geometry is defined by an equation, for example a multi-polynomial equation in powers of x and of y (% and y being the coordinates of a point on the first surface, with X and Y the axes of the optical element).

Generally, the folding mirror is used optically to reduce the overall size of the head-up display, when the projection distances are large (case of augmented reality or virtual reality head-up displays, for example).

This folding mirror can have a first flat surface which then has no optical power and no impact on the optical quality of the virtual image projected by the optical projection system.

However, and as is the case here, the folding mirror can advantageously have a slightly curved first surface so that it is possible to further reduce the overall size of the head-up display. Of moreover, thanks to the curved reflective surface of the folding mirror, it is also possible to improve the image quality of the head-up display, in particular to reduce the residual optical aberrations.

Consequently, it is necessary to use two types of tools (injection or forming moulds) which are different to manufacture, on the one hand, a folding mirror and, on the other hand, an optical element, each having a well-defined curved optical surface.

This generates a complexity of industrial implementation as well as additional manufacturing costs.

Object of the invention

In order to remedy the aforementioned drawback of the state of the art, the present invention proposes a head-up display whose production is simplified.

More particularly, the invention proposes a head-up display as defined in the introduction, in which said first surface of the folding mirror and said first or second surface of the optical element overlap at least partially.

Thus, thanks to the particular optical design of the head-up display of the invention, it is possible to use only one manufacturing tool (for example a mold) to produce the folding mirror and the optical element. The cost of producing such a display is therefore reduced and its implementation is simpler.

In addition, by distributing the optical power of the projection optical system between the folding mirror and the power optical element, it is possible to greatly improve the optical quality of the head-up display.

It will also be noted that the invention can also be implemented with two or more folding mirrors.

In a particular embodiment, said optical element is larger than said folding mirror. In other words, said folding mirror is smaller than said optical element.

Advantageously, said first surface of the folding mirror overlaps completely with at least part of said first or second surface of the optical element.

In this way, it is possible to have a common shape for the optical components of the projection optical system and possibly adapt the cutting and/or the reflective treatment of the components. The invention also proposes a folding mirror in a head-up display as defined above.

According to the invention, said first surface of the folding mirror and said first surface or said second surface of the optical element overlap at least partially.

In a particular embodiment, said folding mirror is smaller than said optical element.

Advantageously, in combination or not with the previous particular embodiment, said first surface of the folding mirror is completely superimposed with at least part of said first or second surface of the optical element.

The invention also proposes a method for producing a head-up display intended to display a virtual image to an individual, said method comprising: a) a step of manufacturing a folding mirror having a first surface and a second surface, said first surface being a curved reflection surface; b) a step of manufacturing an optical element having a first surface and a second surface, said first surface being a curved optical surface, at least partially reflecting; and c) a step of placing said folding mirror manufactured in step a) and said optical element manufactured in step b) in said head-up display.

According to the invention, said first surface of the folding mirror manufactured in step a) and said first or second surface of the optical element manufactured in step b) overlap at least partially.

In a preferred embodiment of this method of production, said folding mirror manufactured in step a) is smaller than said optical element manufactured in step b), and said first surface of the folding mirror completely overlaps with at least part of said first or second surface of the optical element.

The invention finally relates to a mold for producing a head-up display using such a method.

According to the invention, the mold is adapted to receive borders for the manufacturing said folding mirror in step a) or manufacturing said optical element in step b).

Detailed description of an example of realization

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. The invention is not limited to the embodiments illustrated in the drawings. Therefore, it should be understood that when the features mentioned in the claims are followed by reference signs, these signs are included only for the purpose of improving the intelligibility of the claims and in no way limit the scope of the claims.

On the attached drawings:

[Fig. 1] is an overview of a head-up display according to a first embodiment of the invention mounted in a motor vehicle;

[Fig. 2] is a comparative view of the folding mirror and the optical element of the projection optical system of the head-up display of Figure 1;

[Fig. 3] is an example of a cutting diagram of the folding mirror and the optical element of FIG. 2;

[Fig. 4] is an overall view of a head-up display according to a second embodiment of the invention mounted in a motor vehicle;

[Fig. 5] is a comparative view of the folding mirror and the optical element of the projection optical system of the head-up display of figure 4.

As a preamble, it will be noted that the identical or corresponding elements of the different embodiments will be identified as far as possible by the same reference signs, and will not be described each time.

In Figure 1, there is shown a vehicle 1, here a motor vehicle, in which is mounted a head-up display 10 (hereinafter more simply referred to as "display") according to a first embodiment, in which the display 10 is a head-up display “on the windscreen”.

In operation, the display 10 of FIG. 1 displays information in the form of virtual images 6 in the field of vision of an individual 4 located inside the vehicle 1. Here, in FIG. schematically individual 4 in the form of one of his eyes.

This individual 4 observes, through the windshield 3 of the vehicle 1, the virtual images 6 which are visible in a direction of observation 5, outside of the vehicle 1 , here at the level of the bonnet 2 of the vehicle 1 . In practice, the images 6 are formed at an image distance from the individual 4 which is generally between 1.5 and 15 meters, preferably between 5 and 10 meters.

It will be considered in the remainder of the description that the individual 4 is here the driver of the vehicle 1 . Alternatively, it could be a front or rear passenger of the vehicle.

The projected images can include, for example, information relating to vehicle 1 (speed, engine speed, fuel level, distance from other vehicles, etc.), its environment (presence of pedestrians, road signs, etc.) , or even instructions as to the route to be followed by the vehicle 1 (in association with an on-board navigation system for example).

As represented in FIG. 1, the display 10 according to the invention comprises an image generation unit 7 and an optical projection system 11 .

The image generation unit 7 emits a light beam 9 (in FIG. 1, only a primary light ray, or main light ray, is represented) in the direction of the projection optical system 11 of the display 10. This light beam 9 is representative of a light scene, including the images to be displayed to the occupant 4 of the vehicle 1 .

In the particular embodiment illustrated in FIG. 1, the image generation unit 7 here comprises a screen module 8 of the TFT-LCD type (hereinafter referred to as “screen” 8) which is a type of thin-film transistor liquid crystal display (“TFT-LCD” stands for “Thin-Film Transistors-Liquid Crystal Display” in English). The screen 8 is for example backlit by a light source (generally referred to as a "backlight" according to English terminology and not shown here).

The screen 8 forms a display surface, generally substantially planar, of the image generation unit 7 on which said light scene is displayed, this light scene therefore corresponding to the emission of the light beam 9.

The image generation unit 7 is generally connected to a control module (not shown) of the screen 8, this control module receiving signals from the on-board computer (not shown) of the vehicle 1 and driving the screen 8 accordingly to display the light scene on this one.

In other words, when the screen 8 is driven by the control module, the image generation unit 7 generates a light beam 9 representing the scene to be projected in the field of vision of the driver 4.

As a variant, the image generation unit could comprise a laser module of the “laser-scan” type. In this case, the light scene is then produced on a diffuser whose surface is scanned by a fine laser beam which generally comes from an illumination system comprising scanning optics (including for example galvanometric mirrors and one or more lenses) and one or more laser diodes (e.g. red, green, blue diodes).

As a further variant, the image generation unit may comprise a projection module of the DLP (Digital Light Processing) type.

As seen previously, the display 10 comprises a projection optical system 11 (see FIG. 1) which allows the formation, from the source light beam 9, of the virtual image 6 in a field of vision of the individual 4 installed in the passenger compartment of vehicle 1 (here in the driver's position).

This projection optical system 11 comprises a folding mirror 12 and an optical element 13. The folding mirror 12 intercepts the source light beam 9 and reflects it into a reflected light beam 14 towards the optical element 13.

In the first embodiment shown in Figure 1, where the display 10 is a head-up display on the windshield, the optical element 13 of the projection optical system 1 1 is a power mirror 13 (see optical representation diagram in Figure 1) which reflects the light beam 14 to the windshield 3 of the vehicle 1 (see beam 15 leaving the display 10 in Figure 1).

The light beam 14 is reflected by the power mirror 13 (more precisely by its reflective surface 18, see FIG. 2) into an image light beam 15 which is then itself reflected by the windshield 3 (in fact by the sheet inside the windshield 3 if it is a conventional laminated windshield) up to the driver 4 of the vehicle 1. This image light beam 15 is finally oriented along the direction of observation 5 (direction of gaze of the individual 4), the image 6 of the projected light scene then being a virtual image formed generally above the bonnet 2 of the vehicle 1 .

As shown in Figure 2, the folding mirror 12 has a first surface 16 and a second surface 17.

The first surface 16 of the folding mirror 12 is a reflection surface: this means that it is on this first surface 16 that the source light beam 9 is reflected (see optical diagram of FIG. 1) in the direction of the mirror of power 13. This first surface 16 of the folding mirror 12 therefore faces the image generation unit 7 of the display 10 to reflect the source light beam 9.

In general, the first surface 16 of the folding mirror 12 is a curved reflection surface (/.e. nonplanar) whose radius of curvature can be positive or negative. In the case shown in Figure 2, the folding mirror 12 is here convex. However, in other embodiments, depending on the different optical or mechanical constraints of the projection optical system 11 of the display 10, the folding mirror could be concave.

In practice, the first surface 16 comprises a special optical coating giving it a desired spectral reflectivity for a given wavelength range. For example, if the folding mirror 12 is made of glass, the first surface 16 can be covered with a layer of conventional silvering (reflectivity greater than 90% in the visible range) or else with a dielectric multi-layer treatment. According to one possible embodiment, the first surface 16 can form a cold mirror, that is to say have a high reflectivity (for example greater than 90%) for a range of wavelengths located in the visible and a coefficient high transmission (for example greater than 50%) for another wavelength range (located for example in the infrared).

In the case of a “tri-chromatic” screen 8, that is to say formed of pixels of three different colors (typically red, green and blue), the source light beam 9 then having a light spectrum comprising three “ peaks” more or less wide and intense around three different lengths, the reflective coating covering the first surface 16 of the folding mirror 12 is then optimized to reflect sufficiently in each band of wavelengths associated with each of these peaks.

The same applies when the image generation unit comprises a laser module of the laser-scan type. In this case, the relevant wavelength bands are those of the emission from the laser diodes of the laser module.

The second surface 17 of the folding mirror 12 is here also curve, with a curvature of the same sign as the first reflection surface 16 (in a variant, the curvature could be of the opposite sign). This second surface 17 may or may not be covered by a coating.

As shown in Figure 2, the power mirror 13 of the projection optical system 1 1 also comprises a first surface 18 and a second surface 19, which are here both curved (/.e. non-planar).

The first surface 18 of the power mirror 13 is an optical surface, that is to say a surface which is optically active. As shown in Figure 1, it is turned towards the folding mirror 12 to intercept the reflected light beam 14 from the folding mirror 12.

This first surface 18 is at least partially reflective. Preferably here, when the optical element 13 is a power mirror (see FIG. 1), the first surface 18 comprises a special optical treatment causing this optical surface to have a high spectral reflectivity, for example greater than 85%, better still greater at 90%, for example equal to 92%.

According to the invention, and as clearly shown in FIG. 2, the first surface 16 of the folding mirror 12 and the second surface 19 of the optical element 13 overlap at least partially.

In other words, one could say that the first surface 16 of the folding mirror s and the second surface 19 of the power mirror s are substantially identical, that is to say that their representative equations (the locus of the points belonging to the geometric surface) are similar or almost similar, on the portion of surface that they have in common.

In practice, the shapes (/.e. the geometries) of the first surface 16 (reflection surface) of the folding mirror s and of the first surface 18 (optical surface) of the optical element 13 can be designed and calculated by optical simulation depending on: the different optical parameters: size (width and height) and projection distance of the virtual image (eye-image distance), size and position of the image generation unit, curvature of the windshield , etc... ; and mechanical constraints: maximum size of the display 10, position and inclination of the windshield 3, average position of the individual 4 in the passenger compartment, position of the eyebox, etc.

Preferably, a folding mirror 12 and a freeform type 13 power mirror. This means that the surface equation of the first surfaces 16, 18 of the two mirrors 12, 13 is not a simple sphere (spherical mirrors) but can be written very simply in the form of a polynomial surface (aspherical) in % and y, possibly added a "conical" term, of revolution or not. In other embodiments, the surface equations can be written using Zernike or even Chebyshev polynomials.

In other embodiments of the invention, it may be the first surface of the folding mirror and the first surface of the optical element which overlap at least partially.

In other embodiments, the first surface of the folding mirror and the first or second surface of the optical element (power mirror) could overlap entirely, i.e. on all their surfaces.

As shown in Figure 2, in the embodiment shown here, the folding mirror 12 is smaller than the optical element 13 of the projection optical system 1 1. Alternatively, it could of course be larger or of the same dimensions.

In FIG. 3 there is shown a top view of the optical element 13 and of the folding mirror s (dashed lines in FIG. 3), showing the respective possible dimensions of these two mirrors. In this figure, we note that the two mirrors 12, 13 here each have a rectangular shape, with lengths L1, L2 and heights H1, H2 respectively. These shapes are not limiting, and the mirrors could alternatively be circular, or square, or polygonal or even elliptical in shape, for example. Similarly, as a further variant, the respective shapes of the two mirrors could be different from each other, with a square folding mirror and a rectangular power mirror for example.

In the embodiment shown in Figures 2 and 3, the first surface 16 of the folding mirror 12 overlaps completely with at least part of the second surface 19 of the optical element 13 (see dashes in Figure 3).

The process for producing the head-up display 10 of FIG. 1 will be described later and in more detail with reference to FIG.

In FIG. 4, the vehicle 1 has been shown, this time equipped with a head-up display 10 according to a second embodiment, in which the display 10 is a head-up display “to be combined”.

In this type of head-up display 10, the virtual image 6 is not formed after reflection on the windshield 3 of the vehicle 1 but is projected directly by the optical projection system 11 (not referenced in the figure 4), that is to say thanks to the folding mirror 12 and the optical element 13.

Thus, this optical element 13 is generally called "combiner". Indeed, it makes it possible to combine (i.e. superimpose) the landscape or the luminous scene which is usually seen by the individual 4 looking through the windshield 3 of the vehicle 1 with the virtual image 6 projected by the display 10.

The individual 4 then observes through the optical element 13 and the windshield 3 of the vehicle 1, the images 6 which are formed in the direction of observation 5, outside the vehicle 1, here at the level of the bonnet 2 of vehicle 1 .

As shown in Figures 4 and 5, the folding mirror 12 is here identical and also formed of a convex mirror. It comprises a blade having a first surface 16 and a second surface 17, these two surfaces being curved. The first surface 16 is a reflective optical surface (see Figure 5) on which an optical coating is applied to give it appropriate reflective optical properties depending on the application. As before, the folding mirror s is oriented so that the first surface 16 more or less faces the image generating unit 7 and the screen 8 to reflect the source light beam 9.

The only truly different device in this second embodiment of Figure 4 (compared to the display of Figure 1) is the optical element 13 which, instead of being optically equivalent to a mirror (case of the first mode embodiment, see Figures 1 and 2) here is a partially reflective and partially transparent blade.

More specifically, and as clearly shown in Figure 5, the optical element 13 is here formed of a thin curved blade, typically between 1 and 10 millimeters, preferably between 2 and 5 millimeters, having a first surface 18 and a second surface 19. The first surface 18 is therefore a curved optical surface facing the folding mirror 12 to intercept the reflected light beam 14 (see FIG. 4).

In addition, the first surface 18 is the partially reflective surface (see dashes near the first surface 18 in Figure 5) of the blade 13. The first surface 18 is for example covered with a partially reflective coating (see dashes near the first surface 18 in Figure 5). This reflective coating here comprises a thin layer of silver or aluminum (typically a few tens of nanometers) deposited on the first surface 18 (possibly by means of a primer layer) then covered with a coating (silicon or titanium coating) to prevent its oxidation.

Advantageously, the second surface 19 is - for its part - covered with an anti-reflection treatment (AR) intended to reduce the parasitic reflections on the rear face of the blade 13 (these parasitic reflections can create "ghost" images in the luminous scene to be projected to the individual 4).

Still advantageously, the reflective coating of the first reflective surface 18 and the AR treatment of the second surface 19 are adapted according to the spectral content of the source light beam 9 emitted by the screen 8 in the direction of the optical projection system 11.

In practice, the partially reflecting coating of the first surface 18 of the blade 13 is such that the average reflectivity over the range of wavelengths of the source light beam 9 is between 40 and 60%, preferably between 45 and 55% , for example around 50%. This first surface 18 is therefore also partially transparent.

Similarly, the anti-reflective treatment of the second surface 19 of the blade 13 is such that the average reflectivity over the range of wavelengths of the source light beam 9 is less than 10%, preferably less than 5%, better less than 2%, for example less than or equal to 1% in the band of wavelengths from 380 to 780 nm.

According to the invention, and as shown in Figure 5, the first surface 16 of the folding mirror 12 and the second surface 19 of the blade 13 overlap at least partially, and even totally here where the folding mirror 12 and the optical element 13 are of the same size.

Moreover here, the second surface 17 of the folding mirror 12 and the first surface 18 of the blade 13 are also superimposed over their entire extent. In other words, if we disregard the different treatments deposited on the first 16, 18 and on the second surfaces 17,19, it can be said that the folding mirror s and the optical element 13 are identical and completely overlap. In other embodiments, the folding mirror and the optical element can have different dimensions (width, height and thickness) and shapes to satisfy particular optical and/or mechanical constraints. Thus, the folding mirror can be smaller or larger than the optical element, and the first surface of the folding mirror can overlap completely with at least part of the first or second surface of the blade.

The invention also relates to a method of making a head-up display such as those shown in Figures 1 and 4.

This process firstly involves two manufacturing steps.

During a step a) of manufacture, the folding mirror 12 is manufactured as described above (see FIGS. 2 and 5), that is to say with a first surface 16 and a second surface 17.

During another step b) of manufacture, the optical element 13 is manufactured as described above (see FIGS. 2 and 5), that is to say with a first surface 18 and a second surface 19.

In a preferred embodiment, the folding mirror 12 and the optical element 13 are made of transparent plastic material, for example polycarbonate, polymethyl methacrylate (PMMA), polyurethane (PU) or cyclo copolymers. -olefins (COC). In this case, they can be manufactured hot using an injection molding process or else a reaction injection molding process (“Reactive Injection Molding” or RIM).

This type of manufacture in plastic material requires the use of an injection mold having a cavity having two internal surfaces whose shapes are adjusted very precisely to be complementary respectively to the first and second surfaces of the folding mirror 12 and of the optical element 13 to be manufactured.

According to the invention, the first surface 16 of the folding mirror 12 manufactured in step a) and the first 18 or second surface 19 of the optical element 13 manufactured in step b) overlap at least partially.

To this end, the injection mold for the production of the head-up display 10 according to this method is adapted to receive edges for the manufacture of the folding mirror s or the manufacture of the optical element 13, according to their dimensions. respective. Preferably, the folding mirror 12 manufactured in step a) is smaller than the optical element 13 manufactured in step b); and the first surface 16 of the folding mirror s overlaps completely with at least part of the first 18 or second surface 19 of the optical element 13.

Thanks to the edges in the injection mould, it is possible to inject into the forming cavity only the useful part (or at least the useful part plus a few margins to then make the desired cuts) to consume less plastic material and thus reducing manufacturing costs.

For example, if we consider the case of Figure 3 in which the optical element 13 (power mirror) is larger than the folding mirror 12, then we can first use the injection mold to fabricate the power mirror 13 which is larger and then insert borders into the mold cavity to fabricate the folding mirror 12 which is smaller.

In another embodiment, where the dimensions of the folding mirror and of the optical element are relatively close, one can imagine making two plastic parts which are then cut to order to the respective dimensions of the folding mirror and the optical element.

Injection molding being a process carried out at high temperature, the shape of the first 16, 18 and the second 17, 19 surfaces of the folding mirror 12 and of the optical element 13 change when they cool after demolding to reach the temperature ambient (typically between 20° and 25°).

Thus, provision can be made for the internal surfaces of the cavity of the injection mold to be slightly different from the first and second surfaces of the folding mirror 12 and of the optical element in order to precisely take account of the variations in shape with temperature.

After forming and cutting, the first surface 16 of the folding mirror 12 and the first surface 18 of the optical element 13 respectively are treated so that they are respectively a reflective surface and an at least partially reflective optical surface.

During a step c) of the production method, the folding mirror 12 manufactured in step a) and the optical element 13 manufactured in step b) are placed in the head-up display 10 of Figure 1 or Figure 4.

In other embodiments, the folding mirror and the element optics can be made of mineral glass, for example a silica-based glass (“soda lime” glass) or else a borosilicate glass (N-BK7 glass from the Schott company, for example). In this case, they can be made by forming from a flat blade of glass (as can be the two sheets of the windshield) which, when heated to high temperature, softens and collapses on a mold of adjusted shape. .

This forming mold can advantageously be designed for manufacturing the folding mirror and the optical element. Such a forming mold comprises for example a “skeleton” of which a particular surface has the same shape as the first or second surface of the folding mirror or of the optical element.

As for the injection mold described above, the particular surface of the skeleton can be adapted so that the reflective surface of the folding mirror or the optical surface of the optical element has the desired shape after cooling to room temperature. The present invention is in no way limited to the embodiment described and represented, but the person skilled in the art will be able to make any variant in accordance with his spirit.

Claims

[Claim 1] Head-up display (10) intended to display a virtual image (6) to an individual (4), said head-up display (10) comprising: an image generation unit (7) adapted to transmit a source light beam (9); and a projection optical system (11) adapted to form, from said source light beam (9), said virtual image (6) in a field of vision of said individual (4), said projection optical system (11) comprising: a folding mirror (12) having a first surface (16) and a second surface (17), said first surface (16) being a curved reflection surface facing said image generating unit (7) for reflecting said source light beam (9); and an optical element (13) having a first surface (18) and a second surface (19), said first surface (18) being a curved optical surface, at least partially reflecting, and facing said folding mirror (12) for intercepting said reflected light beam, characterized in that said first surface (16) of folding mirror (12) and said first (18) or second surface (19) of optical element (13) overlap at least partially.

[Claim 2] A head-up display (10) according to claim 1, wherein said optical element (13) is larger than said folding mirror (12).

[Claim s] A head-up display (10) according to claim 1 or 2, wherein said first surface (16) of the folding mirror (12) completely overlaps with at least a portion of said first (18) or second surface. (19) of the optical element (13).

[Claim 4] Folding mirror (12) in a head-up display (10) intended to display a virtual image (6) to an individual (4), said head-up display (10) comprising: a images (7) adapted to emit a source light beam (9); and a projection optical system (11) adapted to form, from said source light beam (9), said virtual image (6) in a field of vision of said individual (4), said projection optical system (11) comprising: said folding mirror (12) having a first surface (16) and a second surface (17), said first surface (16) being a curved reflecting surface facing said image generating unit (7) for reflecting said beam luminous source (9); and an optical element (13) having a first surface (18) and a second surface (19), said first surface (18) being a curved optical surface, at least partially reflecting, and facing said folding mirror (12) for intercepting said reflected light beam, characterized in that said first surface (16) of folding mirror (12) and said first (18) or second surface (19) of optical element (13) overlap at least partially.

[Claim 5] Folding mirror (12) according to claim 4, said folding mirror (12) being smaller than said optical element (13) of the projection optical system (11).

[Claim s] A folding mirror (12) according to claim 4 or 5, wherein said first surface (16) of the folding mirror (12) completely overlaps with at least part of said first (18) or second surface ( 19) of the optical element (13).

[Claim 7] Method of making a head-up display (10) intended to display a virtual image (6) to an individual (4), said method of manufacturing comprising: a) a step of manufacturing a mirror of folding (12) having a first surface (16) and a second surface (17), said first surface (16) being a curved reflection surface; b) a step of manufacturing an optical element (13) having a first surface (18) and a second surface (19), said first surface (18) being a curved optical surface, at least partially reflecting; and c) a step of positioning said folding mirror (12) made from 18 step a) and said optical element (13) manufactured in step b) in said head-up display (10) comprising: an image generation unit (7) adapted to emit a source light beam (9 ); and a projection optical system (1 1 ) adapted to form, from said source light beam (9), said virtual image (6) in a field of vision of said individual (4), said projection optical system (1 1 ) comprising: said folding mirror (12), said first surface (16) facing said image generating unit (7) to reflect said source light beam (9); and said optical element (13), said first surface (18) facing said folding mirror (12) to intercept said reflected light beam, characterized in that said first surface (16) of the folding mirror (12) fabricated from step a) and said first (18) or second surface (19) of the optical element (13) manufactured in step b) overlap at least partially.

[Claim 8] A method according to claim 7, wherein: said folding mirror (12) fabricated in step a) is smaller than said optical element (13) fabricated in step b); and said first surface (16) of the folding mirror (12) overlaps completely with at least part of said first (18) or second surface (19) of the optical element (13).

[Claim 9] Mold for the production of a head-up display (10) according to the method of claim 7, characterized in that it is adapted to receive borders for the production of said folding mirror (12) at the step a) or the manufacture of said optical element (13) in step b).