HEAD-UP DISPLAY DEVICE

Abstract

The present invention relates to a head-up display device (10) comprising: a. a transparent carrier (20) comprising an inlet optical interface (30) and an outlet optical interface (32), b. a reflector element (22) arranged on one portion of the outer face (30E) of the inlet optical interface (30), c. a source (24) for projecting information, which source is capable of emitting, in the direction of the reflector element (22), a light beam polarised according to a main polarisation and referred to as the incident beam (FI), the incident beam (FI) arriving at the reflector element (22) at an incidence angle and defining, with the reflector element (22), an incidence plane, the main polarisation being a polarisation contained within the incidence plane, referred to as P-polarisation, the reflector element (22) having a greater reflectivity, over a range of incidence angles comprising the incidence angle, for P-polarised light than for rectilinear polarisation light perpendicular to the incidence plane, which is referred to as S-polarisation.

Description

[0001] DESCRIPTION

[0002] TITLE: Head-up display device

[0003] The present invention relates to a head-up display device. The present invention also relates to a vehicle comprising such a head-up display device.

[0004] A head-up display device typically comprises an information projection source capable of generating a light beam toward a transparent support. The transparent support comprises an input diopter and an output diopter. The reflection of the light beam on each of the diopters creates two virtual images: a useful image obtained by reflection on the input diopter and a parasitic image obtained by reflection on the output diopter. The parasitic image, also called a "ghost" (from the English translated into French as "phantom") affects the visibility of the useful image.

[0005] To limit the impact of the parasitic image and enhance the brightness of the useful image, it is known to apply a semi-reflective treatment to the entrance diopter so as to increase the reflection on this diopter and thus reduce the quantity of light transmitted to the exit diopter. An anti-reflective treatment can, in addition, be applied to the exit diopter to limit reflections on it. Such a technique is however not applicable when the transparent support is a windshield. Indeed, an anti-reflective treatment applied to the outer face of a windshield would not be resistant to environmental conditions (bad weather, solar radiation, windshield wiper blade).

[0006] Another known variation consists, instead of anti-reflective treatment, of tinting the transparent support so as to absorb the light transmitted towards the exit diopter. However, for legal reasons, this technique is not applicable when the transparent support is a windshield.

[0007] Another very common solution is to create a prism (in English "wedge") at the level of the structure of the transparent support. This prismatic effect makes it possible to superimpose the reflection created by the entrance diopter on the reflection created by the exit diopter. However, in the case of windshields, the combination of windshield (angle of inclination, curvature) and head-up display device requires manufacturing a specific windshield for each vehicle model. The manufacture of the windshield is therefore complicated.

[0008] There is therefore a need for a head-up display device that makes it possible to limit the ghost effect relating to the parasitic image without complicating the manufacture of the transparent support, and which is compatible with all types of transparent supports, including the windshield of a vehicle. To this end, the present description relates to a head-up display device comprising:

[0009] - a transparent support comprising an entrance diopter and an exit diopter, each diopter having an external face and an internal face opposite the external face,

[0010] - a reflector element arranged on at least part of the external face of the entrance diopter, an information projection source capable of emitting, in the direction of the reflector element, a light beam polarized according to a main polarization, called the incident beam, the incident beam arriving on the reflector element with an angle of incidence and defining with the reflector element a plane of incidence, the main polarization being a polarization contained in the plane of incidence, called P polarization, the reflector element having greater reflectivity, over a range of angles of incidence including the angle of incidence, for light of P polarization than for light of rectilinear polarization perpendicular to the plane of incidence, called S polarization.

[0011] According to other advantageous aspects, the device comprises one or more of the following characteristics, taken individually or in all technically possible combinations:

[0012] - the reflecting element has a greater reflectivity, over the range of angles of incidence, for light of polarization P than for light of different polarization;

[0013] - the reflectivity of the reflecting element for light of polarization P, over the range of angles of incidence, is greater than or equal to 10 percent, preferably greater than or equal to 15 percent, advantageously greater than or equal to 20 percent, even more advantageously greater than or equal to 40 percent;

[0014] -the reflectivity of the reflector element for light of polarization other than a P polarization, over the range of angles of incidence, is less than or equal to 10 percent, preferably less than or equal to 5 percent;

[0015] - the range of angles of incidence extends over at least 20 degrees, preferably at least 40 degrees, advantageously at least 60 degrees;

[0016] - the range of incidence angles includes a Brewster angle relative to the entrance diopter;

[0017] - the information projection source is configured to emit the incident beam with an angle of incidence chosen so that the portion of the incident beam transmitted by the reflector element arrives at the output diopter with an angle substantially equal to the Brewster angle relative to the output diopter;

[0018] - the reflective element comprises a stack of dielectric layers;

[0019] - the transparent support is a windshield of a vehicle, the reflective element being advantageously arranged over the entire external face of the entrance diopter.

[0020] The present description also relates to a vehicle comprising a head-up display device as described previously.

[0021] Other features and advantages of the invention will become apparent upon reading the following description of embodiments of the invention, given by way of example only, and with reference to the drawings which are:

[0022] - [Fig 1 ] figure 1 , a schematic representation of an example of a head-up display device, and

[0023] - [Fig 2] Figure 2, a schematic representation seen in perspective of an example of the interior of a vehicle comprising the head-up display device of Figure 1.

[0024] A head-up display device 10 is illustrated in Figures 1 and 2.

[0025] As illustrated in Figure 2, the device 10 is adapted to be integrated into a vehicle 12. The vehicle is, for example, a land, air or naval vehicle. The land vehicle is, for example, a motor vehicle (Figure 2) or a railway vehicle.

[0026] The device 10 is capable of displaying information in the field of vision of the driver 14 of the vehicle 12. The information is, for example, provided by on-board instruments of the vehicle 12. For example, the information relates to a speed indicator of the vehicle 12, to the energy consumption of the vehicle 12, to alarms relating to the malfunction of certain components of the vehicle 12 or to navigation information (mapping, positions, directions).

[0027] The device 10 comprises a transparent support 20, a reflective element 22 and an information projection source 24.

[0028] The transparent support 20 comprises an inlet diopter 30 and an outlet diopter 32. The inlet diopter 30 has an external face 30E and an internal face 30I opposite the external face 30E. The outlet diopter 32 has an external face 32E and an internal face 32I opposite the external face 32E. The external face 30E, 32E of each diopter 30, 32 is a face oriented towards the outside of said diopter 30, 32, that is to say towards the external environment (the air). The internal face 30I, 32I of each diopter 30, 32 is oriented towards the inside of said diopter 30, 32. The transparent support 20 comprises at least one layer of a transparent material between the input diopter 30 and the output diopter 32. The transparent material is, for example, glass or plastic.

[0029] In an exemplary implementation, the transparent support 20 comprises several layers of transparent materials, possibly different, between the entry diopter 30 and the exit diopter 32. The materials of said layers are, for example, glass, ethylene vinyl acetate (EVA), or polyvinyl butyral (PVB).

[0030] In particular, in the example illustrated by FIG. 1, the transparent support 20 comprises a first layer 34 of glass, a second layer 36 of PVB and a third layer 38 of glass. In this example, it is considered that the indices of the materials of the different layers are substantially identical, and do not induce additional parasitic reflections at the interfaces.

[0031] The transparent support 20 is, for example, a blade also called a “combiner”. Alternatively, the transparent support 20 is a windshield, such as the windshield of the vehicle 12 in which the device 10 is integrated.

[0032] The reflective element 22, also called a reflective polarizer, is an element arranged on at least a portion of the external face 30E of the entrance diopter 30. By the term "arranged", it is understood that the reflective element 22 is applied (therefore in contact) to the external face 30E of the entrance diopter 30, and adheres to this face (possibly by a fixing means). The reflective element 22 is, thus, integral with the external face 30E of the entrance diopter 30. The reflective element 22 is, for example, a coating or treatment (for example obtained by physical deposition or chemical deposition) or a film (for example laminated or held by electrostatic effect).

[0033] When the transparent support 20 is a windshield of a vehicle, the reflective element 22 is advantageously arranged over the entire external face 30E of the entrance diopter 30. This makes it possible to make the reflective element 22 invisible to the user (no patch effect).

[0034] The reflector element 22 is an element capable of reflecting an incident light beam Fi having a given range of wavelengths, as a function of the angle of incidence ©j of the incident beam Fi on the reflector element 22 and the polarization of said incident beam Fi.

[0035] The given range of wavelengths of the incident beam Fi belongs, for example, to the visible range (380 nanometers to 700 nanometers).

[0036] The angle of incidence ©i of the incident beam Fi is the angle between the axis of the beam and the normal N to the reflector element 22 at the point of incidence Pi of the incident beam Fi on the reflector element 22. The axis of the incident beam Fi and the normal N to the reflector element 22 at the point of incidence Pi define a plane of incidence. In the example illustrated by FIG. 1, the plane of incidence is the plane of the figure. In particular, the reflector element 22 is capable of, on the one hand, reflecting at least a portion of the incident beam Fi to form a useful virtual image observable from an observation window (corresponding to a useful beam Fu) and, on the other hand, transmitting at least another portion of the incident beam Fi towards the exit diopter 32.The output diopter 32 is, where appropriate, capable of reflecting part of the beam transmitted by the reflector element 22 to form a parasitic virtual image observable from the observation window (corresponding to a parasitic beam F. P ).

[0037] In the following, a linear polarization contained in the plane of incidence is also called P polarization, and a linear polarization perpendicular to the plane of incidence is also called S polarization.

[0038] The reflector element 22 is optimized to reflect light of P polarization. The reflector element 22 thus has a greater reflectivity, over a given range of angles of incidence and over the given range of wavelengths, for light of P polarization than for light of different polarization (S polarization, circular, elliptical).

[0039] Advantageously, the reflectivity of the reflector element 22 for a light of polarization P, over the range of angles of incidence and over the given range of wavelengths, is chosen so as to be compatible with the transparency criteria imposed on motor vehicle windshields (so that the reflector element 22 remains transparent and does not alter the driver's perception), while being sufficiently high so that the "ghost" effect is negligible. To this end, the reflector element 22 is, for example, such that the signal-to-noise ratio between the useful beam and the parasitic beam is less than or equal to 3 percent, preferably less than or equal to 1 percent, advantageously less than or equal to 0.5 percent.

[0040] Preferably, the reflectivity of the reflector element 22 for light of polarization P, over the given range of angles of incidence and over the given range of wavelengths, is greater than or equal to 10 percent, preferably greater than or equal to 15 percent, advantageously greater than or equal to 20 percent, advantageously greater than or equal to 40 percent.

[0041] Advantageously, the reflectivity of the reflector element 22 for light of polarization other than a P polarization, over the range of angles of incidence and over the given range of wavelengths, is less than or equal to 10 percent, preferably less than or equal to 5 percent. Advantageously, the range of angles of incidence extends over at least 20 degrees, preferably at least 40 degrees, advantageously at least 60 degrees.

[0042] Preferably, the range of angles of incidence 0i includes the Brewster angle between the external medium (air) and the support transparent to the entrance diopter (typically 56° for an air-glass interface). The reflector element 22 is in fact configured to make the effect of the Brewster angle non-existent, that is to say that the polarization P does not cancel at the Brewster angle. It is recalled that the Brewster angle is the angle of incidence of an incident beam on a diopter for which the beam is not reflected on this diopter if it is of polarization P.

[0043] The reflective element 22 comprises, for example, a stack of dielectric layers.

[0044] The reflector element 22 is, for example, a polarizer having a specific reflectivity for P-polarized light, as described in patent application WO 96 / 19347 A.

[0045] In particular, the reflective element 22 comprises, for example, a multilayer polymer film comprising layers of a crystalline or semi-crystalline naphthalene dicarboxylic acid polyester, for example, a 2,6-polyethylene naphthalate ("PEN") or a copolymer derived from ethylene glycol, naphthalene dicarboxylic acid and certain other acids such as terephthalate ("co-PEN"), with a positive optical coefficient of strain, i.e., upon stretching, its refractive index in the direction of stretching increases, having an average thickness of not more than 0.5 microns; and layers of a second selected polymer, for example, a polyethylene terephthalate ("PET") or a co-PEN, having an average thickness of not more than 0.5 microns.

[0046] In another example, the reflective element 22 comprises a multilayer polymer film comprising layers of a crystalline or semi-crystalline polyester, e.g., PET, having an average thickness of no more than 0.5 microns; and layers of a second selected polymer, e.g., polyester or polystyrene, having an average thickness of no more than 0.5 microns; wherein said film has been stretched in at least one direction to at least twice the unstretched dimension of that direction.

[0047] In an exemplary implementation, the reflective element 22 also has at least one coating providing additional optical and / or mechanical properties. The coating is, for example, thermal protection, a neutralizing colorimetric treatment or an anti-scratch or anti-fog coating.

[0048] Additionally or alternatively, the reflector element 22 is configured so as to, over the range of angles of incidence, reflect each of a P-polarized light and an S-polarized light with a high reflectivity (typically greater than or equal to 50%) in the infrared range (at least near infrared: 700 pm to 1 pm). This makes it possible in particular to reject more solar radiation.

[0049] The information projection source 24 is capable of emitting an incident light beam onto the reflector element 22. The incident beam Fi carries information which is, for example, as described previously.

[0050] The incident beam Fi emitted by the information projection source 24 is a beam polarized according to a specific polarization, called the main polarization.

[0051] The main polarization is a rectilinear polarization contained in the plane of incidence, called P polarization. The main polarization is thus different from an S polarization, a circular polarization or an elliptical polarization.

[0052] The wavelengths of the incident beam Fi are in the wavelength range given for the reflector element 22, typically in the visible.

[0053] The information projection source 24 is configured so that the incident beam Fi arrives at the reflector element 22 with an angle of incidence ©i included in the range of angles of incidence defined previously for the reflector element 22.

[0054] Advantageously, the information projection source 24 is configured to send the incident beam Fi onto the reflector element 22 with an angle of incidence ©i such that the beam transmitted by the reflector element 22 arrives at the output diopter 32 with an angle substantially equal to the Brewster angle between the middle of the transparent support 20 and the external medium (air) (typically 33° for a glass-air interface), or in an angle range extending over 10 degrees around said Brewster angle. The incident beam being of polarization P, this makes it possible to completely eliminate the parasitic reflection on the output diopter 32.

[0055] The operation of the head-up display device 10 will now be described.

[0056] Initially, the information projection source 24 sends an incident light beam polarized according to the main polarization towards the reflector element 22. The incident beam Fi is in the given wavelength range, typically in the visible. The incident beam Fi arrives at the reflector element 22 with an angle of incidence ©i relative to a normal N to the reflector element 22 at the point of incidence Pi.

[0057] The reflector element 22 then reflects at least a portion of the incident beam Fi to form a useful virtual image observable from an observation window. The incident beam Fi being of polarization P and the angle of incidence ©i of the beam on the reflector element 22 being included in the range of angles of incidence, the quantity of reflected incident beam Fi is maximized compared to an incident beam Fi of polarization S, and more generally of polarization different from P. The reflector element 22 also transmits at least another portion of the incident beam Fi towards the output diopter 32.

[0058] Depending on the angle of incidence ©i, the output diopter 32 reflects or does not reflect a part of the beam, transmitted by the reflector element 22 and the input diopter 30, to form a parasitic virtual image observable from the observation window.

[0059] When this is the case, the amount of light reflected on the exit diopter 32 is however relatively small. For example, for a main polarization of type P, the amount of light reflected on the exit diopter 32 is typically of the order of 1 to 2 percent for an angle of incidence ©i of 65 degrees. On the other hand, if the main polarization were of type S, the amount of light reflected on the exit diopter 32 would rather be of the order of 20 percent for an angle of incidence ©i of 65 degrees.

[0060] Furthermore, for an angle of incidence chosen so that the beam transmitted by the reflector element 22 arrives at the exit diopter 32 with an angle substantially equal to the Brewster angle between the middle of the transparent support 20 and the external environment (air), the quantity of light reflected on the exit diopter 32 is zero or almost zero (no parasitic reflection).

[0061] Thus, the head-up display device 10 makes it possible to superimpose information useful for driving in a driver's field of vision.

[0062] The combination of a reflector element 22, optimized to reflect light of polarization P, and an information projection source 24 emitting a light beam polarized according to polarization P, makes it possible to increase the quantity of useful light reflected compared to the quantity of stray light reflected.

[0063] In particular, for a P polarization, the percentage of reflected stray light is low compared to the percentage of reflected useful light, which makes the "ghost" effect relatively negligible. Moreover, for specifically chosen angles of incidence ©i, the percentage of reflected stray light is almost zero, or even nil.

[0064] P polarization also has the advantage of being compatible with polarized sun lenses. Such lenses are traditionally configured to transmit only P-polarized light and reject other types of polarization.

[0065] In addition, the addition of a reflective element 22 on the transparent support 20 is simple to implement since this does not involve modifying the structure of the support 20, nor the internal layer(s) of the support 20. The reflective element 22 has in particular the same configuration regardless of the structure of the transparent support 20 (angle of inclination, curvature), which is not the case with prism (wedge) solutions of the state of the art. Thus, the manufacture of the transparent support 20 is not complicated and the device 10 is adaptable to all types of transparent supports, both combiners and windshields.

[0066] Those skilled in the art will understand that the embodiments described above are capable of being combined with each other when such combinations are compatible.

[0067] The embodiments described are also adaptable with a prismatic structure. In this addition, the output diopter 32 is inclined relative to the input diopter 30 (“wedge”) so as to superimpose the parasitic virtual image on the useful virtual image. Such an addition makes it possible to further limit the “ghost” effect because the parasitic image, already greatly attenuated by the specific configuration of the device 10, is further superimposed on the useful image.

Claims

DEMANDS 1. Head-up display device (10) comprising: a. a transparent support (20) comprising an input diopter (30) and an output diopter (32), each diopter (30, 32) having an outer face (30E, 32E) and an inner face (30I, 32I) opposite the outer face (30E, 32E), b. a reflector element (22) disposed on at least a part of the outer face (30E) of the input diopter (30), c.an information projection source (24) capable of emitting, in the direction of the reflector element (22), a light beam polarized according to a principal polarization, called incident beam (Fi), the incident beam (Fi) arriving on the reflector element (22) with an angle of incidence (Oi) and defining with the reflector element (22) a plane of incidence, the principal polarization being a polarization contained in the plane of incidence, called P polarization, the reflector element (22) having a greater reflectivity, over a range of angles of incidence including the angle of incidence (Oi), for a light of P polarization than for a light of rectilinear polarization perpendicular to the plane of incidence, called S polarization.

2. Device (10) according to claim 1, wherein the reflector element (22) has a greater reflectivity, over the range of angles of incidence, for a light of polarization P than for a light of different polarization.

3. Device (10) according to claim 1 or 2, wherein the reflectivity of the reflector element (22) for a light of polarization P, over the range of angles of incidence, is greater than or equal to 10 percent, preferably greater than or equal to 15 percent, advantageously greater than or equal to 20 percent, even more advantageously greater than or equal to 40 percent.

4. Device (10) according to any one of claims 1 to 3, wherein the reflectivity of the reflector element (22) for light of polarization other than a P polarization, over the range of angles of incidence, is less than or equal to 10 percent, preferably less than or equal to 5 percent.

5. Device (10) according to any one of claims 1 to 4, wherein the range of angles of incidence extends over at least 20 degrees, preferably at least 40 degrees, advantageously at least 60 degrees.

6. Device (10) according to any one of claims 1 to 5, wherein the range of angles of incidence includes a Brewster angle relative to the entrance diopter (30).

7. Device (10) according to any one of claims 1 to 6, wherein the information projection source (24) is configured to emit the incident beam (Fi) with an angle of incidence (0i) chosen such that the portion of the incident beam transmitted by the reflector element (22) arrives at the output diopter (32) with an angle substantially equal to the Brewster angle relative to the output diopter (32).

8. Device (10) according to any one of claims 1 to 7, wherein the reflecting element (22) comprises a stack of dielectric layers.

9. Device (10) according to any one of claims 1 to 8, wherein the transparent support (20) is a windscreen of a vehicle, the reflector element (22) being advantageously arranged on the entire external face (30E) of the entrance diopter (30).

10. Vehicle (12) comprising a display device (10) according to any one of claims 1 to 9.