LIGHTING MODULE FOR MOTOR VEHICLE HEADLIGHTS

Description

Technical field of the invention

[0001] The present invention relates to a lighting module for a headlight of a motor vehicle, the lighting module comprising a matrix of micro-mirrors. The invention also relates to a headlight for a motor vehicle comprising such a lighting module. The invention also relates to a motor vehicle comprising such a headlight or such a lighting module. State of the art

[0002] For lighting motor vehicles, the use of lighting modules comprising a light source and a micro-mirror matrix is ​​known. A micro-mirror matrix is ​​an electromechanical microsystem comprising a multitude of micro-mirrors which are all movable around the same axis and which can take at least two distinct orientations. In its first orientation, a micro-mirror transmits a light beam out of the lighting module, into a lighting field. In its second orientation, the light beam is deflected out of the lighting field and is absorbed by a structure of the lighting module. The orientation of each micro-mirror can be controlled individually by the effect of an electrostatic force. The lighting module comprises a control circuit connected to an electronic control unit. The electronic control unit emits a control current to each of the micro-mirrors to define their orientation.

[0003] Such projectors allow complex images to be composed and projected in front of the vehicle. They are therefore used to perform various functions such as, for example, the projection of information useful for the safety of pedestrians located in the direct vicinity of the vehicle, or for example, a road lighting function to avoid dazzling other motorists.

[0004] During operation, such a lighting module can become very hot. Excessive heating can lead to malfunction or even destruction of the micromirror array or its control circuit. Heat sinks and fans are known to be used to cool the micromirror array. However, these cooling methods are bulky and insufficiently efficient to keep the lighting module below a damaging temperature.

[0005] Document WO 2017 / 147632 A1 discloses a lighting module for an automobile headlight according to the preamble of claim 1. Subject of the invention

[0006] The aim of the invention is to provide a lighting module which overcomes the above drawbacks and improves the lighting modules known from the prior art. In particular, the invention makes it possible to produce a lighting module which is compact, simple to implement and which limits the heating of the micro-mirror matrix or its control circuit.

[0007] The invention relates to a lighting module for a headlight of a motor vehicle, the lighting module comprising a light source and a matrix of micro-mirrors, comprising a mask interposed between the light source and the matrix of micro-mirrors, the mask comprising an opening allowing light rays to pass from the light source and oriented towards the matrix of micro-mirrors, the mask comprising an opaque part blocking light rays from the light source and not oriented towards the matrix of micro-mirrors, and the matrix of micro-mirrors extending along a first plane and the mask extending along a second plane, the first plane and the second plane being substantially parallel, the opening of the mask being positioned substantially directly above the matrix of micro-mirrors, characterized in that the micro-mirrors are individually movable between an active orientation and an inactive orientation,the micro-mirrors reflecting light rays from the light source through the opening of the mask when they are in their active orientation, the micro-mirrors reflecting light rays from the light source against the opaque part of the mask when they are in their inactive orientation, and in that the opaque part of the mask comprises an extra thickness, the micro-mirrors reflecting light rays from the light source against said extra thickness when they are in their inactive orientation.,

[0008] The lighting module may include a chip supporting the micromirror array, the chip including an exposed surface positioned around the micromirror array and not intended to reflect light rays out of the lighting module, the opaque portion of the mask blocking light rays from the light source and directed toward the exposed surface.

[0009] The aperture may have a shape homothetic to a shape of the micromirror array.

[0010] The opening may have a substantially rectangular shape, with a width of the opening being between 4mm and 10mm, or even between 6mm and 8mm, and a length of the opening being between 5mm and 15mm, or even between 8mm and 12mm.

[0011] The area of ​​the aperture may be greater than or equal to the area of ​​the micromirror array, or greater than or equal to twice the area of ​​the micromirror array, and / or the area of ​​the aperture may be less than or equal to four times the area of ​​the micromirror array, or less than or equal to three times the area of ​​the micromirror array.

[0012] The lighting module may include a light collimator interposed between the light source and the mask, a light beam from the collimator illuminating the opening of the mask.

[0013] The lighting module may include at least one heat dissipation means, including a fan and / or a heat sink. The mask may support a heat dissipation means, including a fan and / or a heat sink.

[0014] The invention also relates to a projector comprising a lighting module as defined previously.

[0015] The invention also relates to a motor vehicle comprising a lighting module as defined previously or a projector as defined previously. Summary description of the drawings

[0016] These objects, characteristics and advantages of the present invention will be explained in detail in the following description of a particular embodiment made without limitation in relation to the attached figures among which: There Figure 1is a schematic view of a motor vehicle according to one embodiment of the invention. The Figure 2 is an isometric view of a projector according to one embodiment of the invention. The Figure 3 is a first partial isometric view of a lighting module equipped with a matrix of micro-mirrors. The Figure 4 is a second partial isometric view of the lighting module. The Figure 5 is an isometric view of a mask according to one embodiment of the invention. The Figure 6 is a view of a chip comprising an array of micro-mirrors. The Figure 7 is a schematic view of the lighting module, with micromirrors in an active orientation. figure 8 is a schematic view of the lighting module with micromirrors in an inactive orientation. Description of preferred embodiments of the invention

[0017] There Figure 1illustrates a motor vehicle 1 equipped with a headlight 2 according to an embodiment of the invention. The vehicle can be of any type, for example it can be a private vehicle, a utility vehicle or a truck. The headlight 2 is arranged at the front of the vehicle but could also be fitted to the rear of the vehicle. The headlight makes it possible to illuminate the road, to be seen by other motorists and / or to project images onto the ground providing information to the driver or his environment.

[0018] There Figure 2 illustrates the projector 2. The projector 2 comprises a housing 3 containing a lighting module 10 provided with a matrix of micro-mirrors 21 as well as holes 4, 5 for other lighting devices. The lighting module 10 can perform different lighting functions of the projector such as for example producing a position light, a dipped beam, a main beam, a fog light or even a turn signal.

[0019] THE Figures 3 and 4 illustrate more precisely the lighting module 10 provided with the micro-mirror matrix 21. The lighting module 10 comprises a light source 11, in this case a light-emitting diode, a collimator 12 and a projection optical system 13. The light source 11 and the collimator 12 are arranged so that light rays from the light source pass through the collimator 12 and are then directed towards the micro-mirror matrix 21. The light rays can then be reflected by the micro-mirror matrix 21 and pass through the projection optical system 13. The collimator 12 and the projection optical system 13 may comprise one or more optical lenses. A protective housing 14, visible only on the Figure 2 , can be fixed on the lighting module to protect it. This protective housing is perforated at the level of the projection optical system 13 to let the light rays out.

[0020] As shown in the Figure 4 , a first optical axis A1 can be defined passing through the center of the optical projection system 13, that is to say passing through the center of the optical lens(es) that compose it. Similarly, a second optical axis A2 can be defined passing through the center of the collimator, that is to say passing through the center of the optical lens(es) that compose it. The first optical axis A1 and the second optical axis A2 define the path of a light ray passing through the center of the collimator and through the center of the optical projection system 13. The angle B1 formed between the axis A1 and the axis A2 can be approximately equal to 24° or to any other value allowing an adequate arrangement of the collimator and the projection optics in the lighting module.

[0021] Furthermore, the lighting module 10 comprises heat dissipation means. These heat dissipation means are in particular a fan 15, a first heat sink 16 positioned in a rear part of the lighting module, opposite the projection optical system 13 and the collimator 12, and a second heat sink 17 positioned around the collimator 12.

[0022] The micro-mirror array 21 is a micro-electromechanical system comprising a multitude of flat micro-mirrors which are all independently movable around a single axis. The micro-mirrors can take two distinct orientations of 24°. The orientation of each micro-mirror can be controlled individually by the effect of an electrostatic force. Each micro-mirror can be square in shape with a side length of approximately 7 µm. The micro-mirrors can be spaced approximately 0.5 µm apart from each other. The micro-mirror array has a rectangular shape with a width of approximately 3.5 mm and a length of approximately 7 mm and can comprise several hundred micro-mirrors across the width and several hundred micro-mirrors across the length. The micro-mirror array 21 is integrated into a larger chip 20 illustrated in the Figure 6. The chip 20 also has a rectangular shape and may have a width of approximately 22 mm and a length of approximately 32 mm. The chip comprises the micro-mirror array in its center and a connection interface 22 on an outer periphery. An apparent surface 23 extends between the micro-mirror array 21 and the connection interface 22. Only the micro-mirror array 21 is intended to reflect the light from the light source. The apparent surface 23 does not comprise micro-mirrors. The chip 20 and in particular the micro-mirror array are particularly sensitive to temperature. To ensure correct operation, the temperature of the chip and the micro-mirror array must not exceed a threshold temperature, for example a temperature of 68°C.

[0023] According to a first orientation, called active orientation, a micro-mirror reflects a light ray coming from the light source 11 towards the optical projection system 13. That is to say the light ray passes through the optical projection system 13 and emerges from the projector to illuminate the road or the environment of the vehicle. According to a second orientation, called inactive orientation, a micro-mirror reflects a light ray coming from the light source 11 elsewhere than towards the optical projection system 13. That is to say the light ray does not pass through the optical projection system 13 and is not used for a lighting function.

[0024] The lighting module also comprises a printed circuit 18 on which the chip 20 supporting the micro-mirror array 21 is fixed. The printed circuit, the chip and the micro-mirror array extend along planes parallel to each other and perpendicular to the first optical axis A1. The printed circuit 18 comprises electronic drivers for controlling the micro-mirror array. The electronic control unit issues a command defining which micro-mirrors are oriented according to the first orientation and which micro-mirrors are oriented according to the second orientation. The command is issued to the micro-mirror array via the printed circuit and the chip. Thus, each micro-mirror defines a pixel of a complex image: the micro-mirror array can thus be used not only to obtain standardized lighting but also to project complex images.

[0025] The lighting module comprises a mask 30 interposed between the light source and the micro-mirror matrix. According to the embodiment shown, the mask is even interposed between the collimator 12 and the micro-mirror matrix 21. The mask comprises an opening 31 allowing light rays from the light source to pass and directed towards the micro-mirror matrix. The mask comprises an opaque part 32 blocking light rays from the light source and not directed towards the micro-mirror matrix, i.e. directed elsewhere than towards the micro-mirror matrix. By "blocking", it is understood that the light rays can be absorbed or reflected by the opaque part. A light ray that would be directed towards the printed circuit 18 or towards the chip 20 around the micro-mirror matrix, in particular towards the visible surface 23, would thus be blocked by the opaque part 32 of the mask.The path of a light ray reflected by the mask does not encounter the micromirror array, the chip to which the micromirror array is attached, or the printed circuit board on which the chip is attached. Preferably, the light rays reflected by the mask do not enter the projection optical system 13 but are directed toward a non-functional area of ​​the lighting module where they will eventually be absorbed. Alternatively, the opaque portion could be translucent or transparent and deflect (rather than block) the light rays so that they do not strike the micromirror array, the chip, or the printed circuit board.

[0026] The 30 mask, particularly visible on the figures 3 And 5, extends along a plane substantially parallel to the plane of the micro-mirror array, the chip and the printed circuit. The mask may be a generally rectangular-shaped plate of a size close to that of the printed circuit. A length of the mask may be, for example, of the order of 100 mm and a width of the mask may be of the order of 65 mm. The opening 31 of the mask is also rectangular in shape and has a length of the order of 10 mm and a width of the order of 7 mm. The ratio of the surface area of ​​the opening 31 to the surface area of ​​the micro-mirror array 21 is therefore approximately 2.8 or 2.9. The opening 31 is larger than the micro-mirror array 21 but smaller than the chip 20. The opening of the mask is positioned substantially directly above the micro-mirror array, on the path of the light rays coming from the collimator 12 and directed towards the micro-mirror array.The size of the opening is sufficient so that on the one hand the entire matrix of micro-mirrors can be illuminated by the light source and on the other hand so that all the light rays reflected by micro-mirrors in active orientation can exit through this same opening 31.

[0027] The light beam exiting the collimator has a substantially circular cross-section until it reaches the opening 31. Advantageously, the collimator is defined so that the circular cross-section of the light beam at the mask corresponds to a circle circumscribed by the rectangle of the opening 31. Beyond the opening 31 the light beam has a rectangular cross-section. The mask therefore has a function of shaping the light beam. The image projected by the lighting module has a rectangular shape and its proportions are substantially identical to those of the micro-mirror matrix.

[0028] Advantageously, the opening 31 has a shape homothetic to that of the micro-mirror matrix 21. That is to say that the rectangle drawn by the opening 31 and the rectangle drawn by the micro-mirror matrix 21 are oriented in the same way and have substantially identical proportions. In the event that the micro-mirror matrix would have a different shape, for example circular or polygonal, the shape of the opening would therefore be adapted accordingly. Advantageously, the angle B1 defining an angle of incidence of the light rays on the mask can be taken into account to adapt the proportions of the opening of the mask. Thus the opening 31 of the mask is defined so that the light beam downstream of this opening (that is to say beyond this opening) illuminates the entirety and only the entirety of the micro-mirror matrix 21.In order to take into account the geometric tolerances of the lighting module, the light beam will be able to illuminate a slightly larger surface than that of the micro-mirror matrix.

[0029] The mask 30 is fixed against the printed circuit by means of spacers 33 making it possible to define a regular spacing between the printed circuit and the mask. The space between the mask and the printed circuit can be between 5 mm and 10 mm. The mask also serves as a support for fixing the optical projection system 13, the collimator 12, the second heat sink 19 and the fan 17. For this purpose, the mask comprises different fixing holes 34 through which pass fixing screws for the optical projection system 13, the collimator 12 and the second heat sink 19. It is specified that these fixing holes 34 are distinguished from said opening in that they are not intended to allow light to pass through but fixing screws. The mask also comprises appendages 35 making it possible to fix the housing 14 and the entire lighting module 10 within the projector 2.

[0030] On the one hand, the micro-mirrors reflect the light rays from the light source through the opening of the mask when they are in their active orientation. On the other hand, the micro-mirrors reflect the light rays from the light source against the opaque part of the mask when they are in their inactive orientation. The light rays are either absorbed by the mask or reflected by the mask and therefore confined in the space separating the mask from the printed circuit. Near the opening, the mask comprises an excess thickness 36 shown schematically on the figures 7 and 8. The excess thickness 36 is positioned on the path of the light rays when they are reflected by micro-mirrors in inactive orientation. The mask can be made for example of plastic or aluminum so as to conduct the heat towards the heat dissipation means. The mask 30 is therefore likely to heat up but it is also efficiently cooled because the fan 15 and the second heat sink 17 are fixed directly against the mask. In addition, the mask is made of a material that is resistant to temperature and / or has good heat conduction properties. The spacers 33 make it possible to keep the hot mask at a controlled distance from the chip 20 and the printed circuit 18.

[0031] There Figure 7 illustrates the operation of the lighting module. The light source emits a light ray which passes through the collimator (shown schematically by a single optical lens on the Figure 7). The light ray then passes through the aperture and is reflected by at least one micro-mirror in active orientation. The light ray passes back through the aperture and re-enters the optical system (schematized by a single optical lens on the Figure 7 ). The light ray emerges from the optical system substantially parallel to the first optical axis A1.

[0032] There figure 8 illustrates the operation of the lighting module. The light source emits a light ray which passes through the collimator (shown schematically by a single optical lens on the Figure 7 ). The light ray then passes through the opening and is reflected by a micro-mirror in the inactive orientation. The light ray encounters the opaque part of the mask, in particular the extra thickness 36. The light ray is absorbed by the mask and is converted into heat. The heat is removed from the mask by means of the heat dissipation means, in particular the fan 15 and the heat sink 17.

[0033] Naturally, operation of the lighting module with one part of the micro-mirrors in active orientation and the other part of the micro-mirrors in inactive orientation is possible.

[0034] Thanks to the invention, the mask fulfills several functions: first of all, it prevents the light from the light source from unnecessarily heating the micro-mirror matrix and / or the chip and only allows useful light rays to pass through, i.e. those which impact the micro-mirror matrix. The chip 20 and the printed circuit 18 do not absorb any light rays or very few of them, which minimizes their heating. The mask also makes it possible to block the light rays reflected by the micro-mirrors in inactive orientation. Finally, the mask evacuates the heat produced by the absorption of light rays away from the micro-mirror matrix and it forms a support for securing various essential components of the lighting module. The temperature of the chip and / or the micro-mirror matrix can thus be lowered by 10°C to 30°C compared to an identical lighting module without a mask.

Claims

1. Lighting module (10) for a projector (2) of a motor vehicle (1), the lighting module (10) comprising a light source (11) and a matrix of micromirrors (21), comprising a mask (30) disposed between the light source (11) and the matrix of micromirrors (21), the mask comprising an opening (31) allowing light rays coming from the light source (11) to pass and oriented towards the matrix of micromirrors (21), and the mask (30) comprising an opaque part (32) blocking light rays coming from the light source (11) and not oriented toward the matrix of micromirrors (21) and the matrix of micromirrors (21) extends in a first plane and in that the mask (30) extends in a second plane, the first plane and the second plane being substantially parallel, the opening (31) of the mask (30) being positioned substantially in vertical alignment with the matrix of micromirrors (21) reflecting light rays coming from the light source (11) against the opaque part (32) of the mask (30) when they are in their inactive orientation, in that the opaque part (32) of the masque (30) comprises an overthickness (36), the micromirrors reflecting light rays coming from the light source (11) against said overthickness (36) when they are in their inactive orientation.

2. Lighting module (10) according to the preceding claim, characterized in that it comprises a microchip (20) supporting the matrix of micromirrors (21), the microchip (20) comprising an apparent surface (23) positioned around the matrix of micromirrors (21) and not intended to reflect light rays out of the lighting module, the opaque part (32) of the mask (30) blocking light rays coming from the light source (11) and oriented toward the apparent surface (23).

3. Lighting module (10) according to any one of the preceding claims, characterized in that the opening (31) has a shape homothetic to a shape of the matrix of micromirrors (21).

4. Lighting module (10) according to any one of the preceding claims, characterized in that the opening (31) has a substantially rectangular shape, a width of the opening being between 4 mm and 10 mm inclusive, or even between 6 mm and 8 mm inclusive, and a length of the opening being between 5 mm and 15 mm inclusive, or even between 8 mm and 12 mm inclusive.

5. Lighting module (10) according to any one of the preceding claims, characterized in that the area of the opening (31) is greater than or equal to the area of the matrix of micromirrors (21), or even greater than or equal to twice the area of the matrix of micromirrors (21) and / or in that the area of the opening (31) is less than or equal to four times the area of the matrix of micromirrors (21), or even less than or equal to three times the area of the matrix of micromirrors (21).

6. Lighting module (10) according to any one of the preceding claims, characterized in that it comprises a light collimator (12) disposed between the light source (11) and the mask (30), a light beam coming from the collimator (12) illuminating the opening (31) of the mask.

7. Lighting module (10) according to any one of the preceding claims, characterized in that it comprises at least one heat dissipation means, notably a fan (15) and / or a heatsink (17).

8. Lighting module (10) according to the preceding claim, characterized in that the mask (30) supports a heat dissipation means, notably a fan (15) and / or a heatsink (17).

9. Projector (2) comprising a lighting module (10) according to any one of the preceding claims.

10. Motor vehicle, characterized in that it comprises a lighting module according to any one of Claims 1 to 8 or a projector according to the preceding claim.