FR3086730A1 - LIGHT MODULE FOR A MOTOR VEHICLE, AND LIGHTING AND / OR SIGNALING DEVICE PROVIDED WITH SUCH A MODULE - Google Patents

Abstract

The invention relates to a light module for a vehicle comprising a light source (21), a pixelated and digital imaging system, and an optical input device (22) interposed along the path of the rays emanating from the source (21). , between the source (21) and the pixelated and digital imaging system for transmitting a transmitted part, of rays from the source (21) to the pixelated and digital imaging system, it comprises a prism (26), comprising first, second and third faces (26a, 26b, 26c) and configured to: - transmit rays between the first and third faces (26a, 26c) from the transmitted part to the impact surface (24); - forming rays reflected by reflection of rays returned by the impact surface (24), by total internal reflection on the first face (26a); - returning reflected rays via the second face (26b). A solid interface is arranged between a window associated with the imaging system and one face of the prism, with a selected optical index.

Description

"Light module for a motor vehicle, and lighting and / or signaling device provided with such a module"

The present invention relates in particular to a light module for a motor vehicle, and to a lighting and / or signaling device provided with such a module.

A preferred application relates to the automotive industry, for vehicle equipment, in particular for the production of devices capable of emitting light beams, also called lighting and / or signaling functions, which generally meet regulations. For example, the invention can allow the production of a light beam, preferably highly resolved, of pixelated type, in particular for signaling and / or participation in lighting functions at the front of a vehicle. It can be used to display pictograms or variable patterns on an outgoing light projection surface.

Signaling and / or lighting lights for motor vehicles are light devices which include one or more light sources and lens which closes the light. In a simplified manner, the light source emits light rays to form a light beam which is directed towards the ice in order to produce an illuminating surface which transmits light outside the vehicle. These functions must meet regulations in terms of light intensity and visibility angles in particular. The known lighting and signaling modules have hitherto been designed to emit, for example:

- a dipped beam, directed downwards, also sometimes called a code beam and used in the presence of other vehicles on the road;

- a main beam without cutoff, and characterized by maximum illumination in the center line of the vehicle;

- a light beam for foggy weather, characterized by a flat cut-off and a large illumination width;

- a signaling beam for city traffic, also called city lamp.

Recently, technologies have been developed which make it possible to produce a pixelated or segmented high definition beam, with a definition of at least 1000 segments, in particular by means of micro or nano electromechanical devices called respectively MEMS or NEMS. Because of the great flexibility in shape and pattern of beams they allow and because their price tends to decrease, these systems tend to be implemented for increasingly important functions, in particular in projectors in front of vehicles. FIG. 1 gives an example of setting up a pixelated and digital imaging system in the form of a micro-mirror matrix 13 in a beam projection module. A light source 11 generates light rays in the direction of an optical device 12 making it possible to generate a beam which will impact a reflection face 14 of a matrix with micro mirrors 13. According to the inclination of the mirrors, controlled, the light is either returned to the projection device 15, or returned to a dead zone so as not to participate in active illumination.

In certain cases, this supposes a significant output illumination and in particular sufficient to comply with regulatory conditions of light flux. Achieving significant illumination is however difficult with regard to the layout illustrated in FIG. 1. It is easily understood that the magnification of the lens used for the input device 12 or its approximation to the matrix of micro mirrors 13 quickly poses a problem of interference with the lens used as a projection device 15. In the example shown, the beam envelope delimited by the rays a1, a2 is at the limit of interfering with the edge of the projection device 15; similarly, the rays b1, b2 returned by the matrix 13 are transmitted by the device 15 in rays c1, c2 at the limit of interfering with the input device 12. In view of this limitation, the patent document WO 2017 / 143371 A1 discloses a headlamp for a motor vehicle comprising a matrix of micro mirrors and provided with a pair of light sources with light-emitting diodes each associated with a lens for focusing a light beam on the reflection surface of the matrix of micro mirrors. This duplication of sources obviously increases the luminous flux leaving the projector. However, it inevitably increases the cost and the bulk.

The present invention aims to remedy at least in part the drawbacks of current techniques.

The present invention relates, in one aspect, to a light module for a motor vehicle configured to produce an output beam, comprising a light source comprising at least one light-emitting diode, a pixelated and digital imaging system, and an optical input device. interposed, along the path of the light rays coming from the light source between the light source and the pixelated and digital imaging system so as to transmit at least a part, called transmitted part, of the light rays coming from the light source towards a surface impact of the pixelated and digital imaging system.

Advantageously, it comprises a prism, comprising a first face, a second face and a third face, and configured for:

- transmit between the first face and the third face at least part of the light rays from the part transmitted to the impact surface;

- forming rays reflected by reflection of at least a portion of light rays returned by the impact surface, by total internal reflection on the first face;

- return at least part of the rays reflected to a projection area via the second face.

In addition, a pane is arranged between the impact surface and the third face, and a solid interface joins the third face and one face of the pane arranged opposite the third face.

According to an advantageous possibility, the interface material, that of the glass and that of the prism have the same optical index, or optical indices not differing by more than 10% from each other. Under these conditions, we suppress, or very strongly limit, parasitic reflections due to Fresnel's laws, which is all the more favorable to the efficiency of the module.

Thus, the light rays are deflected during their journey from the light source to the projection device at least partly through the prism. The function of the prism comprises, upstream of the imaging system, a transmission of light rays from the source and, downstream of the imaging system, a total internal reflection making it possible to effect an angular modification of the rays, advantageously strong , so as to return the rays coming out of the prism towards the projection device. The prism allows large angular variations in the direction of the beams between the beam upstream of the imaging system and the beam downstream of the latter.

It is thus easy to adjust the position and the angle of the optical device located at the input, without being hampered by considerations of space relative to the optical projection device, contrary to the state of the art illustrated in FIG. advantageously bring the optical input device closer to the imaging system and / or increase its diameter (the increase in illumination is directly linked to the increase in the diameter of a lens). In doing so, the light efficiency of the beam impacting the imaging system is higher, which makes it possible, despite the use of a light-emitting diode source, to obtain satisfactory illumination at the output.

Furthermore, the assembly of the glass on the third face of the prism by the solid interface, for example glue, ensures continuity of transmission of light rays between these two parts. Thanks to this, possible phenomena of reflection in a solid / air / solid interface are avoided; however, such untimely reflections could produce a re-emission of parasitic light rays and their projection onto the road at the same time as the desired effective beam, which would limit the potential for application of pixelated beams in the automotive field in particular, especially in which relates to applications to anti-glare road beams. While the imaging device and the optical elements are currently considered as complementary but distinct organs of a light module, the present invention combats this prejudice and associates them more intimately, by assembling a window of the imaging device and a face. of a prism without interstitial air space. The presence of the interface also makes it easier to adjust the variations of optical index on the path of light rays, while that of air is currently automatically encountered. According to a preferred aspect, close or identical optical indices are selected, as will appear below.

According to another aspect, the present invention also relates to a lighting and / or signaling device for a motor vehicle equipped with at least one light module. This device can comprise at least one additional module comprising at least one of an additional module configured to produce a basic beam of low beam and an additional module configured to produce a basic beam of high beam.

Advantageously, the pixelated beam can be an effective complement to another beam, or even several. In particular, in a preferred case, the device comprises an additional module configured to produce a basic beam of low beam and an additional module configured to produce a basic beam of high beam and in which the output beam of the module overlaps in part of both the main beam and / or the main beam of the dipped beam.

The present invention also relates to a vehicle equipped with at least one module and / or a device according to the present invention.

Preferably, the interface is a polymerized optical adhesive.

Optionally, the maximum thickness of the adhesive interface is less than 1 mm, or even 0.5 mm.

In a preferred case, the third face and the face of the glass are parallel. Thus, the thickness of the interface is constant.

According to a particularly advantageous embodiment, the module is such that the second face and the third face are carried by two planes perpendicular to each other.

In addition, it preferably comprises an optical device for projecting the output beam at least partially receiving the at least part of the returned rays.

Advantageously, the optical projection device has an optical axis perpendicular to the second face.

Optionally, the optical projection device has an optical axis forming an obtuse angle with a mean direction of the transmitted part. This possibility is very useful for limiting the size and gives great freedom in lens size for the optical input device.

In a non-limiting case, the third face is parallel to the impact surface. Advantageously and preferably, the third face has an anti-reflective coating. This avoids the ghost image phenomena that strong reflections from mirrors on the third side can produce.

In one embodiment, the prism is made of a material whose Abbe number is greater than or equal to 50.

Advantageously, the prism is in PM MA or in Crown glass.

Optionally, a pane is arranged between the impact surface and the third face.

According to an example, a first face of the glass is located opposite the impact surface and comprises an anti-reflective coating. This avoids the phenomenon of ghost images that can produce strong reflections in return from the mirrors on the glass.

Advantageously, the anti-reflective coating is configured to reflect less than 4%, preferably less than 2% of the light rays in the visible range.

Preferably, the mean direction of the transmitted part forms, with a normal to the first face, an angle between -20 ° and + 20 °.

Preferably, the distance between the impact surface and the third face is less than or equal to 2 mm, and preferably less than or equal to 1 mm.

In one embodiment, the pixelated and digital imaging system includes an array of micro-mirrors.

Optionally, the output beam is configured to project at least one pictogram pattern.

In a preferred embodiment, the module is configured to project a light beam into the front of a motor vehicle.

Other characteristics and advantages of the present invention will be better understood with the aid of the exemplary description and of the drawings among which:

- Figure 1 shows a diagram of a projection of a pixelated beam according to the state of the art;

- Figure 2 shows an embodiment of the invention.

Unless otherwise specified, technical characteristics described in detail for a given embodiment may be combined with technical characteristics described in the context of other embodiments described by way of example and not limitation.

In the characteristics set out below, the terms relating to verticality, horizontality and transversality, or their equivalents, are understood in relation to the position in which the lighting module is intended to be mounted in a vehicle . The terms “vertical” and “horizontal” are used in the present description to designate directions, in an orientation perpendicular to the plane of the horizon for the term “vertical”, and in an orientation parallel to the plane of the horizon for the term "horizontal". They are to be considered in the operating conditions of the device in a vehicle. The use of these words does not mean that slight variations around the vertical and horizontal directions are excluded from the invention.

For example, an inclination relative to these directions of the order of + or - 10 ° is considered here as a minor variation around the two preferred directions.

The device of the invention incorporates at least one module making it possible to generate a pixelated type beam, but also preferably ensures the projection of at least one other beam, by means of at least one other module. The device of the invention can therefore be complex and combine several modules which can also optionally share components.

In the context of the invention, the expression “passing beam” is understood to mean a beam used during the presence of crossed and / or followed vehicles and / or other elements (individuals, obstacles, etc.) on or near the roadway. . This beam has a descending mean direction. It can possibly be characterized by an absence of light above a plane inclined by 1% downwards on the side of the traffic in the other direction, and by another plane inclined by 15 degrees compared to the previous of the side of traffic in the same direction, these two plans defining a cut in accordance with European regulations. The purpose of this top down cutoff is to avoid dazzling other users present in the road scene extending in front of the vehicle or on the side of the road. The passing beam, formerly from a simple headlamp, has undergone changes, the passing function being able to be coupled with other lighting characteristics which are still considered as passing beam functions within the meaning of the present invention .

This includes the following functions:

- AFS beam (abbreviation for "Advanced Frontlighting System" in English), which notably offers other types of beams. These include the so-called BL (Bending Light in English for cornering light) function, which can be broken down into a so-called DBL (Dynamic Bending Light in English for mobile cornering light) function and a so-called FBL (Fixed Bending) function. Light in English for fixed bend lighting);

- beam says Town Light in English, for city lighting. This function widens a low beam type beam while slightly reducing its range;

- bundle known as Motorway Light in English, for highway lighting, performs the highway function. This function ensures an increase in the range of a low beam by concentrating the luminous flux of the low beam at the level of the optical axis of the headlamp device considered;

- beam says Overhead Light in English, for portal light. This function modifies a typical low beam so that signaling gantries above the road are satisfactorily lit by the low beam;

- beam known as AWL (Adverse Weather Light in English, for bad weather light).

The function of the basic driving beam is to illuminate the scene in front of the vehicle over a wide area, but also over a considerable distance, typically around 200 meters. This light beam, by its lighting function, is mainly located above the horizon line. It may have a slightly ascending optical axis of illumination, for example.

The device can also be used to train other lighting functions via or outside of those described above.

As indicated above, one aspect of the invention relates to a module allowing the generation of an output beam of the pixelated type, that is to say processed by a pixelated and digital imaging system offering great flexibility, by imaging system control, in terms of beam patterns actually projected. The terms “pixelated and digital imaging system”, “pixelated ray imaging system” or their equivalents have for definition a system emitting a light beam, said light beam being formed of a plurality of light sub-beams , each light sub-beam being able to be controlled independently of the other light sub-beams. These systems can for example be micro-mirror arrays 23 as shown, liquid crystal devices, a digital light processing technology (DLP) in Anglo-Saxon terms. Micro-mirror arrays are also called, in English terms, "Digital Micro mirror Device" (DMD).

Each independently controllable sub-beam forms a pixelated ray. The control of the micro-mirror arrays is carried out by control electronics. Each micro-mirror preferably has two operating positions. A so-called active position corresponds to an orientation of the micromirrors allowing reflection towards an output diopter of an incident light beam.

A so-called passive position corresponds to an orientation of the micro-mirrors allowing reflection towards an absorbing surface of an incident light beam, that is to say towards a direction different from that of the output diopter. In general, this type of imaging system is implemented in mechanical micro-electronic systems known under the term MEMS, which also includes in the present application the so-called NEMS nanosystems.

In a manner known per se, a light source 21 is used to illuminate an impact surface 24 of the pixelated imaging system, for example the reflective face of the micro-mirrors of a matrix of micro-mirrors 23, and the rays treated by the pixelated imaging system are returned to be projected, generally via an optical output element such as a projector glass or a projection lens. In general, the present invention can use light sources of the light-emitting diode type also commonly called LEDs. It can possibly be organic LED (s). In particular, these LEDs can be provided with at least one chip capable of emitting light of advantageously adjustable intensity according to the lighting and / or signaling function to be performed. Furthermore, the term light source is understood here to mean a set of at least one elementary source such as an LED capable of producing a flux leading to generate at the output of the module of the invention at least one light beam. In an advantageous mode, the output face of the source is of rectangular section, which is typical for LED chips. Without limitation, the light source 21 is configured to produce a light flux greater than 3000 Im and for example of the order of 4000 Im.

We understand all the interest of pixelated beams in the automotive field and the multiplication of the functionalities that they allow. However, their integration in vehicles concomitantly with the projection systems of other beams is still largely unexplored and induces strong bulk constraints.

FIG. 2 shows an exemplary embodiment of the present invention which allows relative placement of the light source and of the improved optical input device relative to the prior art.

From upstream to downstream following the path of the light rays, there is the presence of a light source 21, which may be of the type previously indicated. Preferably, the light source 21 is configured to emit in a half-space from an emissive area of rectangular shape. At least a part of the rays emitted by the source 21 is optically treated by an optical device 22. The latter may comprise one or more lenses of more or less complex shape.

In FIG. 2, the optical device 22 takes the form of a lens having an inlet face 22a making it possible to admit the light rays coming from the source 21 and an outlet face 22b ensuring projection towards the rest of the module . At the output of the optical device 17, at least one part referenced “a” called the transmitted part of the treated rays is intended to impact the surface of the pixelated and digital imaging system, here a matrix of micro-mirrors 23. However, according to Invention, the light rays first enter through a prism 26, via a first face 26a of the latter.

Preferably, the first face 26a forms an acute angle with the mean direction of the transmitted part "a" of the light rays coming from the source 21. More preferably, the mean direction and normal to the first face 26a forms an angle between -20 ° and + 20 °. Preferably, the angle formed between the first face 26a and the third face 26c is between 40 and 50 °.

In general, it is desirable to use for the prism 26 a transparent material and advantageously having a high Abbe number, preferably greater than or equal to 50. It may be Crown glass or alternatively polymethacrylate. methyl (PMMA).

The light rays entering the prism 26, referenced “a” in FIG. 2, are directed towards a third face 26c of the prism 26 facing which the imaging system is located, which is, in the example shown, a matrix micro-mirrors

23. Advantageously, the impact surface 24 (corresponding to the exposed surface of the micro-mirrors) is parallel to the third face 26c, the latter preferably being planar. The impact surface 24 is protected by a window 27, a first face 27a of which is situated opposite the impact surface 24. A second face 27b of the window 27 is situated opposite the third face 26c. The second face 27b and the third face 26c are spaced from each other so that a space exists between them, a space which is filled by the interface 30 so that there is no space residual air between the interface 30 and the faces 26c, 27, on the path of the light rays.

Advantageously, the distance separating the impact surface 24 and the third face 26c is limited and can for example be less than 2 mm or even 1 mm, and preferably 0.5 mm. The presence of the window 27 can be used to adjust this spacing without the risk of damaging the impact surface 24.

Thus, the window 27 and the prism 26 are joined by means of an interface 30. The latter may also be the place for adjusting the overall thickness of the light transmission leaving the prism towards the surface of impact 24. More specifically, the interface 30 is located in contact and between the second face 27 b of the window 27 and the third face 26 c of the prism 26. Advantageously, the third face 26c and the second face 27b are parallel, if although the thickness of the interface 30 is continuous. Here, thickness is understood to mean the dimension of the interface 30 directed perpendicular to the faces considered.

One aspect of the interface 30 is to completely fill, with a solid medium, the space between the prism and the glass. For this purpose, a contact of the interface 30 on each of the faces 26c and 27b is sufficient, even without adhesion on these faces. However, the interface can also provide a mechanical joining effect so that it forms a coherent whole with at least one of the prism and the glass.

Preferably, the interface 30 is produced thanks to a layer, preferably a single layer, of a transparent material, in particular an optical adhesive. In terms of method, one can have a film of liquid adhesive precursor of the interface on one of the second face 27b is the third face 26c, then attach the other of these faces to the film thus deposited, and crosslink glue. One can in particular use a glue polymerized under a light in the ultraviolet. For example, the adhesive can be sensitive to ultraviolet in a range between 320 and 380 nanometers in wavelength. Cross-linking by annealing is also possible.

Note that the interface 30 forms a solid portion. By solid is meant a state of matter which is neither gaseous nor liquid, which does not exclude that the interface 30 is made of a soft material, for example of elastomer or in the form of a paste.

The interface 30 creates a solid continuity between the prism 26 and the window 27. In order to make this continuity all the more effective from an optical point of view, it is advantageous for the optical index of the interface 30 to be identical or similar to the optical index of at least one of the material of the pane 27 and the material of the prism 26. For example, it is possible to use a prism and a pane of Crown glass, in particular of index 1, 52, or even a poly (methyl methacrylate) prism (PMMA) having an optical index of 1.49 and a glass pane 27 made of glass (in particular Crown glass of index 1.52). The material of the adhesive interface 30 is then chosen to be identical or similar to these indices. For example, the optical glue sold by the company Norland Products Incoporated under the reference "Norland Optical adhesive 83H" can give satisfaction, with an index of 1.56. "Similar" means optical indices which are not more than 10% apart in size and / or which are not more than 0.15 optical index apart. Preferably the indices of the prism, of the window and of the interface are all three within a range of 0.15 in index value and / or 10%. However, we can admit a wider interval, in particular in the case where it is the optical index of the interface which has an intermediate value between the indices of the prism and the glass (this case is, in general, preferred if the indices are different). In this case, the optical indices of the glass and of the prism may be such that they are not distant, each more than 10%, and / or more than 0.15, from the value of the index of the interface.

In the illustrated embodiment, it is also sought to eliminate, or at least to limit, the parasitic effects which a reflection on the first face 27a of the glass could produce of the rays having reached the impact surface 24 and having been think about it. To this end, it is advantageous to provide the window 27 with an anti-reflective coating 28 which may be of common design and in particular be configured to produce a reflection of a maximum of 4%, or even a maximum of 2% in the visible spectrum. . Preferably, the anti-reflection is chosen with a maximum reflection of 1% in the visible spectrum.

Preferably, the impact surface 24 defined by the set of micro-mirrors is of rectangular shape. It preferably extends in a plane perpendicular to a plane carrying the second face 26b of the prism 26 and / or parallel to the optical axis of the projection device 25.

Depending on the orientation of the mirrors, the rays are reflected, either so as to participate in the projected beam, or so as to be inactive. This is how the configuration of the pixelated beam can be controlled at will. In the case shown, the active rays "c" are directed so as to re-enter the prism 26 through the third face 26c. This ray path is configured so that the active rays "c" reach the first face 26a again. However, this time, the angle of the rays relative to the first face 26a is such that a total internal reflection occurs in the prism 26 so as to form reflected rays "d" which are directed towards the second face 26b of the prism 26.

The outgoing rays "e" are directed towards a projection device 25, which is or which typically comprises a projection lens. In the illustrated case, it is a convex plane lens, the inlet face 25a is planar and the outlet face 25b is convex. The reference “f” represents an example of projected radius.

Advantageously, the prism 26 is configured, in terms of angle and choice of materials, so that all of the light rays coming from the input device 22 are transmitted to the matrix of micro mirrors 23 and so that all of the light rays reflected by the latter is reflected by the first face 26a. It will be noted that the zone of the first face 26a through which the rays "a" enter the prism 26 and the zone of the first face 26a through which the rays "c" again reach the first face 26a to be reflected, can be overlap.

The invention is not limited to the embodiments described but extends to any embodiment in accordance with its spirit.

REFERENCES

11. Light source

12. Optical device

13. Matrix of micro-mirrors

14. Face of reflection

15. Optical projection device

21. Light source

22. Optical input device

22a. Entrance face

22b. Exit face

23. Matrix of micro-mirrors

24. Impact area

25. Optical projection device

25a. Entrance face

25b. Exit face

26. Prism

26a. First side

26b. Second side

26c. Third side

27. Glass

27a. First side

27b. Second side

28. Anti-reflective coating

29. Optical axis

30. Interface

Claims (16)

1. Light module for a motor vehicle configured to produce an output beam, comprising a light source (21) comprising at least one light-emitting diode, a pixelated and digital imaging system, and an interleaved optical input device (22), along the path of the light rays coming from the light source (21), between the light source (21) and the pixelated and digital imaging system so as to transmit at least a part, called the transmitted part, of the light rays coming from the light source (21) towards an impact surface (24) of the pixelated and digital imaging system, characterized in that it comprises: - a prism (26), comprising a first face (26a), a second face (26b) and a third face (26c), and configured for: o transmit between the first face (26a) and the third face (26c) at least part of the light rays from the part transmitted to the impact surface (24); o forming rays reflected by reflection of at least a portion of light rays returned by the impact surface (24), by total internal reflection on the first face (26a); o returning at least part of the rays reflected towards a projection area via the second face (26b); - a window (27) disposed between the impact surface (24) and the third face (26c), and a solid interface (30) joining the third face (26c) and one face (27b) of the window (27) arranged opposite the third face (26c). and characterized in that the interface material (30), that of the window (27) and that of the prism (26) have the same optical index, or optical indices not differing by more than 10% from each other . 2. Module according to the preceding claim, wherein the interface (30) is a polymerized optical adhesive. 3. Module according to one of the preceding claims, in which the maximum thickness of the interface is less than 1 mm, or even 0.5 mm. 4. Module according to one of the preceding claims, wherein the third face (26c) and the face (27b) of the glass (27) are parallel. 5. Module according to one of the preceding claims, wherein the second face (26b) and the third face (26c) are carried by two planes perpendicular to each other. 6. Module according to one of the preceding claims, further comprising an optical projection device (15) of the output beam receiving at least partially there at least a portion of the returned rays. 7. Module according to the preceding claim, wherein the optical projection device (15) has an optical axis (29) perpendicular to the second face (26b). 8. Module according to one of the two preceding claims, in which the optical projection device (15) has an optical axis (29) forming an obtuse angle with a mean direction of the transmitted part. 9. Module according to one of the preceding claims, in which the prism (26) is made of a material whose Abbe number is greater than or equal to 50. 10. Module according to one of the preceding claims, in which the prism (26) is made of PMMA or Crown glass. 11. Module according to the preceding claim, wherein another face (27a) of the window located opposite the impact surface (24) comprises an anti-reflection coating (28). 12. Module according to one of the preceding claims, in which the mean direction of the transmitted part forms, with a normal to the first face, an angle between -20 ° and + 20 °. 13. Module according to one of the preceding claims, in which the pixelated and digital imaging system comprises an array of micro-mirrors (23). 14. Module according to one of the preceding claims, in which the output beam is configured to project at least one pictogram pattern. 15. Module according to one of the preceding claims, configured to project a light beam at the front of a motor vehicle. 16. Lighting and / or signaling device for a motor vehicle equipped with at least one module according to any one of the preceding claims.