FR3137438A1 - LIGHT MODULE WITH LED DISPLAY OPTIMIZED FOR AUTOMOTIVE APPLICATION - Google Patents

Abstract

LIGHT MODULE WITH LED DISPLAY OPTIMIZED FOR AUTOMOTIVE APPLICATION The invention relates to a light module for a motor vehicle, comprising an optical projection device (12) with a focus, an entrance face and an exit face; an imager (10) forming a matrix of light sources, arranged between the focus and the entrance face so that the optical projection device (12) can project an enlarged image of said imager (10); in which the imager (10) has a width l and a height h, the entry face and/or the exit face have a width L and a height H, where L>l, H>h, and L-l> H-h, so that the light module has a horizontal field of view greater than a vertical field of view, when said light module is oriented in the mounting position on the motor vehicle. (Figure to be published with the abstract: Figure 4)

Description

LIGHT MODULE WITH LED DISPLAY OPTIMIZED FOR AUTOMOTIVE APPLICATION

The invention relates to the field of light signaling for motor vehicles.

In the field of light signaling for motor vehicles, it is currently known to display light pictograms by means of various light imagers, such as in particular liquid crystal screens requiring backlighting or even optical electromechanical microsystems, commonly referred to as MEMS (acronym of “micro electro mechanic system”), also requiring a light source. These light imagers, potentially very efficient, are however expensive and oversized from a resolution point of view for the display of pictograms, usually of a simple and easily recognizable shape, on and in particular at the rear of a motor vehicle.

The published patent document FR 3 077 117 A1 relates to a light signaling module for a motor vehicle, comprising a liquid crystal imager.

The published patent document WO 2011/092121 A1 relates to a light signal module for a motor vehicle, comprising a surface light source of the OLED type (acronym for “organic light-emitting diode”) and a projection lens. A pictogram display does not seem planned.

The published patent document FR 3 048 059 A1 relates to a light signaling module for a motor vehicle, comprising a matrix of light sources and a projection lens. A pictogram display does not seem planned.

The published patent document US 4,740,780 relates to a head-up display device, comprising a matrix type light source, in this case a matrix of 64 by 64 light points of the electroluminescence diode type, and a converging lens, the light matrix being arranged between the focus and the entrance face of the lens so as to project an enlarged image of the light matrix. However, this device is specifically designed for a head-up display intended to be placed in a dashboard in order to project light images towards the windshield.

The invention aims to overcome at least one of the problems of the aforementioned state of the art. More particularly, the invention aims to propose a light module for a motor vehicle, capable of projecting light images containing in particular pictograms and which is economical from a manufacturing cost and/or use cost point of view.

The subject of the invention is a light module for a motor vehicle, comprising an optical projection device with a focus, an entry face and an exit face; an imager forming a matrix of light sources, arranged between the focus and the entrance face so that the optical device can project an enlarged image of said imager; remarkable in that the imager has a width l and a height h, the entry face and/or the exit face have a width L and a height H, where L>l, H>h, and L-l>H-h , so that the light module has a horizontal field of view greater than a vertical field of view, when said light module is oriented in the mounting position on the motor vehicle.

By imager forming a matrix of light sources is meant a matrix of light sources whose light sources can be controlled individually or in groups, so as to selectively form different light images. The light sources may in particular be electroluminescence diodes (LED for “Light Emitting Diode”), in particular of the “miniLED” type whose dimension is between 100 and 300µm, or of the “MicroLED” type whose dimension is less than 100µm. The light sources can be arranged on a printed circuit board (PCB) or a monolithic type where the light sources are epitaxied on a substrate. The imager can also be a display, in particular of the “MicroLED” type on a “CMOS” type semiconductor, an acronym for “Complementary Metal Oxide Semiconductor”.

By field of view we mean a field in which the image of the imager can be observed by an observer located on the side of the projection.

According to an advantageous embodiment of the invention, L-l>n∙(H-h), where n=2, preferably n=3, more preferably n=5.

According to an advantageous embodiment of the invention, the imager comprises a center in a vertical direction and the optical projection device comprises an optical axis, said center being offset vertically, preferably downwards, relative to said optical axis, when the module light is oriented in the mounting position.

According to an advantageous embodiment of the invention, a projection of the imager on the entry face, along an optical axis of the projection device, is completely included in said entry face, when the light module is oriented in the position disassembly.

According to an advantageous embodiment of the invention, the imager is arranged between the focus and the entrance face so as to obtain an enlargement rate of the projected image of between 1.5 and 2.5.

According to an advantageous embodiment of the invention, the optical projection device has a horizontal optical power Ph and a vertical optical power Pv, where Ph<Pv, when the light module is oriented in the mounting position.

By optical power, we mean the vergence of the optical projection device, corresponding to the inverse of the focal length.

According to an advantageous embodiment of the invention, the optical projection device has a horizontal magnification Gh and a vertical magnification Gv, where Gh≠Gv, preferably Gh<Gv, when the light module is oriented in the mounting position.

By magnification we mean a ratio of size of an object to its image through the optical projection device, the size being in this case considered perpendicular to the optical axis of the optical projection device. For example, if the image is twice as large as the object, the magnification is two.

According to an advantageous embodiment of the invention, the optical projection device is a lens, preferably comprising an anti-reflection treatment on the entry face and/or on the exit face.

According to an advantageous embodiment of the invention, the lens extends horizontally over at least 80% of the width L with a constant cross section.

The invention also relates to a light device comprising a housing, a glass for closing the housing, and a light module housed in the housing, in which the light module is according to the invention, the optical projection device being a lens formed directly on an interior face of the closing window.

The measures of the invention are advantageous in that they make it possible to enlarge the imager while optimizing the luminance in the horizontal and vertical fields of view required for a light signaling device on a motor vehicle.

is a view from the top of a motor vehicle, illustrating the horizontal field of view that a rear light must provide;

is a side view of a motor vehicle, illustrating the vertical field of view that the rear light must provide;

is a schematic side representation of a light module according to a first embodiment of the invention.

is a rear view of the imager and light module lens of the .

is a schematic side view of two variants of the light module of the , corresponding to different growth rates.

is a schematic side representation of another variant of the light module of the .

is a perspective representation of a light module according to a second embodiment of the invention.

is a perspective representation of a glass of a light device according to the invention, on which the projection lens is directly formed.

detailed description

In the description which follows, the notions “horizontal(s)”, “vertical(e)(s)”, “lower(e)(s)” and “superior(e)(s)” are to be understand when the light module is oriented in a normal and operational position such as on the motor vehicle for which it is intended. This orientation corresponds to that in Figures 1 to 8. Note that the width is measured horizontally and the height vertically.

There is a representation, seen from above, of a motor vehicle 2 equipped with a light device forming a rear light 4, in this case a left rear light, capable of being observed and correctly perceived by following motorists located at the rear. In this case, the vehicle 4 moves on a central traffic lane while the two following motor vehicles each move on a traffic lane located laterally to the so-called central traffic lane. Each of the two motorists located respectively in each of the following motor vehicles, whether they are the driver of a vehicle with left-hand drive or right-hand drive, must be able to correctly perceive the light signal of the rear light 4 from a certain distance. The rear light 4 has an optical axis 6 which is parallel to the longitudinal axis of the vehicle 2. It can be observed that the field of view of the rear light 4 extends horizontally on either side of the optical axis 6, and symmetrically. The field of view thus extends horizontally by approximately +/- α relative to the optical axis 6, in this case by +/- 40° relative to said axis. This is a minimum desirable field of view, particularly in line with the regulations relating to motor vehicles. It is notably greater than the horizontal extension of the photometric grids defined by this regulation, which is generally +/- 20°.

There is a representation, in side view, of vehicle 4 of the . We can observe the presence of a following motorist, which may correspond to one of the two following motor vehicles of the . The following vehicle could also move on the same lane as the motor vehicle 2 equipped with the light device of the present presentation. Depending on the height at which the following motorist is, in particular depending on the type of vehicle, and the distance at which he is, he must be able to correctly perceive the light signal from the rear light 4. It can be observed that the field of view of the rear light 4 extends vertically on either side of the optical axis 6, and asymmetrically, namely from +β upwards and -γ downwards. This asymmetry is linked to the fact that the possible vertical position range for the following motorist is not centered on the optical axis 6 of the rear light, but rather shifted upwards. In this case, the field of view extends vertically from -γ=10° to +β=20° relative to optical axis 6. This vertical field of view is - moreover - consistent with the regulations relating to motor vehicles when the mounting height of the signaling system is relatively low. Indeed, the vertical extension of the photometric grids defined by this regulation is generally +/- 10°

The above illustrates the regulatory constraints of a lighting device, in this case a rear light, of a motor vehicle and makes it possible to explain the meaning and interest of the measures of the invention.

There is a schematic side view of a light module according to the invention, which can then be integrated into the rear light 4 of the motor vehicle 2 illustrated in Figures 1 and 2.

The light module 8 comprises an imager 10 forming a matrix 10.1 of light sources, preferably of the electroluminescence diode (LED) type. It is therefore a generally planar and matrix imager in which each pixel is luminous. Each of the light sources or pixels can be electrically powered individually, in particular so as to produce a light image stylized as a pictogram, a symbol or even text. It is understood, however, that the imager 10 can also form more basic light images such as a rectangle or a square, in particular to provide one or more classic light signaling functions such as a stop function, direction indicators, lantern, fog light, light reversing, etc. The light module also includes an optical projection device which is in this case embodied by a lens 12. The latter conventionally comprises an entry face 12.1, an exit face 12.2 and a focus 12.3. This is a converging lens which can notably be of the plano-convex, biconvex or even meniscus-shaped type. The imager 10 is located between the focus 12.3 and the entry face 12.1 of the lens 12, in this case at a distance from said focus 12.3 and said entry face 12.1, so that the lens 12 can project an enlarged image of the imager 10. The virtual enlarged image 10' is represented at focus 12.3.

The positioning of the imager 10 between the entry face 12.1 of the lens 12, in this case at a distance from said focus 12.3 and said entry face 12.1, is advantageous in that it makes it possible to project a light image with a given luminance while reducing the size, cost and electrical consumption of the imager 10 in comparison with a situation where the projection lens would be absent and the imager would have the size of the desired light image. Indeed, it is easy to understand that the fact of enlarging the light image by means of the optical projection device, being in this case a lens 12, makes it possible to reduce the size and cost of the imager. The gain in energy efficiency is explained in that the size of the light image formed through the lens is larger than the image of the imager, and in that the luminance of the light image, which is precisely the visible light flux emitted by a surface element of the image in a given direction, per unit of surface and per unit of solid angle, is unchanged during optical enlargement by the lens 12. More precisely, the luminance of the image is equal to the luminance of the imager itself, excluding light losses when passing through the optical device, such as for example the Fresnel reflection factors at the interfaces, and the absorption of the or materials making up the optical device. In other words, only these losses are likely to reduce the luminance of the image. The entry face 12.1 of the lens being more extensive than the imager 10, but also more extensive than the light image of the imager, no ray coming from the edge of the imager is obscured by the edge of the lens so that the image is seen entirely by an observer - without vignetting. Thus, the electrical power consumed by the imager is much lower than the power consumed by a larger imager, having the size of the desired light image, and without a projection lens. It is understood, however, that what has just been described applies for a luminance in directions close to that of the optical axis, that is to say in the horizontal and vertical fields of view as described below. before in relation to Figures 1 and 2.

There is a rear view of the imager and the optical projection device of the light module of the , following the direction of the optical axis.

There illustrates an asymmetry between the imager and the optical projection device, being in this case a projection lens, making it possible to optimize the luminance of the light image in the horizontal and vertical fields of view described above in relation to Figures 1 and 2.

We observe in fact that the projection lens 12 is extended more horizontally than vertically with respect to the imager 10. The reason is to be able to capture more horizontally diverging light rays and thus ensure sufficient luminance in the larger horizontal field of view. than the vertical field of view.

To the , the imager 10 and the projection lens 12 are rectangular, it being understood that other shapes are possible. The imager 10 has a width l and a height h, and the projection lens, at least its entry face and/or its exit face, has a width L and a height H. Each of the width L and the height H of the projection lens 12 is greater than the width l and the height h of the imager 10, respectively. However, in accordance with the above, the width L is greater than the width l than the height H is greater than the height h, namely Ll>Hh. More particularly, this asymmetry can be expressed by the relation Ll>n∙(Hh), where n is greater than or equal to 1, more particularly greater than or equal to 2, preferably 3, and/or less than or equal to 5.

Always at the , it can be observed that the imager 10 can be decentered vertically, in this case downwards, relative to the optical projection device, being in this case a projection lens 12. This vertical decentering downwards can be explained by the asymmetry of the vertical field of view, as illustrated in , namely where β>γ. The vertical decentering towards the bottom of the imager 10 makes it possible to collect more rays diverging upwards and thus to ensure sufficient luminance upwards following the angle β at the . Also, the center of the imager is imaged in a direction which connects the center of the imager to the optical center of the projection lens 12 (namely its zone of maximum thickness). Thus the center is imaged upwards and the overall image is located on an angular field more upwards than downwards, relative to a horizontal axis.

There is a schematic side view of two variants of the light module of the , corresponding to different growth rates.

At the top of the , we can observe, in comparison with the , that the imager 10 is closer to the focus 12.3 of the projection lens 12 than to the entrance face 12.1 of said projection lens 12, having the consequence of increasing the magnification rate between the imager 10 and its 10' virtual image. The magnification rate can thus be greater than 2 since the distance between the focus 12.3 and the imager 10 is less than the distance between the imager 10 and the entrance face 12.1 of the projection lens. A particularly high magnification rate, for example above 3, can be interesting but has the limitation that the visual field, in which the projected image is visible, is reduced angularly.

Down the , we can observe the opposite from the top of the , namely a magnification rate less than 2 since the imager 10 is closer to the entrance face 12.1 of the projection lens than to the focus 12.3. A low magnification rate limits the constraints on the angular extension of the visual field in which the projected image is visible, but reduces the economic advantage of reducing the size of the imager.

The growth rate of the light module of the invention is advantageously between 1.5 and 3, corresponding to a compromise between reduction in manufacturing and use costs and optical performance.

There is a schematic side representation of the light module of the illustrating the downward decentering of the imager relative to the projection lens, as shown in .

We can in fact observe a downward shift between the optical axis 6 of the light module, corresponding to the optical axis of the projection lens, and the central axis 10.3 of the imager 10. As already mentioned in relation to there , this downward shift makes it possible to optimize the luminance of the projected image in the asymmetrical vertical field of view, namely extended more upwards than downwards.

It should be noted that independently of the downward decentering mentioned above, the projection lens 12 can be truncated at its lower edge, taking into account the smaller downward extent of the field of view. Indeed, the imager 10 can be vertically centered with the projection lens, while the latter can be truncated in its lower part and thus present an apparent centering being in reality rather a vertical offset resulting from the truncated lower edge of the lens projection. Such an arrangement allows more upwardly diverging rays to be exploited for luminance in the upper part of the vertical field of view.

There is a perspective representation of a light module according to a second embodiment of the invention. The reference numbers of the first embodiment are used to designate the identical or corresponding elements of the second embodiment, these numbers being however increased by 100. Reference is also made to the description of these elements in the context of the first mode of achievement.

The light module 108 of the differs from that of the first embodiment in that the projection lens 112 extends horizontally with a constant section over a major part of this horizontal extent. This means that the projection lens 112 in question has zero or at least very low horizontal optical power Ph. The horizontal magnification Gh is then close to 1. The projected image therefore has a size close to that of the object, in the direction considered. The notion of optical power corresponds to the vergence or even the inverse of the focal length, that is to say the distance between the optical projection device, in this case the projection lens, and the focus. The magnification is a ratio of the size of a focal object to its image through the optical projection device, the size being in this case considered perpendicular to the optical axis of the optical projection device. The imager 110 also extends and similarly horizontally along the projection lens 112. The vertical optical power Pv and/or the vertical magnification Gv of the projection lens 112 thus makes it possible to ensure vertical magnification of the image projected while no horizontal magnification takes place or a significantly smaller horizontal magnification takes place.

It is interesting to provide Pv greater than Ph and/or Gv greater than Gh, particularly when the light device and therefore the optical projection device is significantly more extended horizontally than vertically. In such a configuration, a Ph or Gh value close to Pv or Gv, respectively, would require a complex optical projection device, such as for example a particularly thick lens, and therefore not only bulky but also expensive.

The light module of the can be interesting for displaying pictograms in text form or at least a line of characters or signs.

There is a perspective representation of a closing glass of a housing (not shown) intended to receive a light module according to the invention, in particular according to the two embodiments described above, on which the projection lens is directly trained.

The glass 14 or 114 forms in a manner known and conventional in itself a transparent or translucent wall intended to be fixed along its periphery to the housing (not shown) intended to receive a light module according to the invention, in particular for protection purposes. said light module from bad weather and other attacks from the outside world. It is preferably made of plastic material, such as for example polycarbonate (PC) or polymethyl methacrylate (PMMA), and for example produced by injection molding. It comprises an exterior face, intended to be outside the housing, and an interior face, intended to be inside said housing. It can be observed that the projection lens 12 or 112 is in contact with the interior face of the glass 14 or 114. The projection lens 12 or 112 is advantageously made of plastic material, such as for example polycarbonate (PC) or polymethacrylate methyl (PMMA), and for example produced by injection molding. For this purpose, one of the glass 14 or 114 and the projection lens 12 or 112 is initially produced by injection of plastic material into a mold according to a first configuration, and then the other of the glass 14 or 114 and of the projection lens 12 or 112 is produced by injection of plastic material in the same mold but in a second configuration. The first configuration forms a volume corresponding to that of the glass 14 or 114 and the projection lens 12 or 112 which is initially formed, while the second configuration forms a larger volume corresponding to that of the glass 14 and the lens projection 12 or 112. The glass 14 or 114 and the projection lens are then co-molded. It is understood, however, that other methods or variations to the method described above are possible. For example, the mold may include a single cavity having the shape of the projection lens 12 or 112 combined with the shape of the lens 14 or 114.

Generally speaking, the projection lens may have an anti-reflection coating on the exit face and/or on the entry face. The anti-reflection coating on the exit face is particularly advantageous in that it reduces the luminance of the external light reflected towards an observer and thus avoids a reduction in contrast between the light image of the imager and the reflected external light . The application of such an anti-reflective coating is also advantageous on the glass, particularly on the exterior side, for the same reasons as for the projection lens. When the projection lens is formed directly on the inner face of the glass, as shown in , it is understood that the anti-reflective coating is then applied to the exterior face of the glass and/or to the entrance face of the projection lens. The anti-reflective coating mentioned above is in itself well known to those skilled in the art.

Also generally speaking, the optical projection device can have a horizontal optical power Ph and a vertical optical power Pv greater than the horizontal optical power Ph. Similarly, the optical projection device can have a horizontal magnification Gh and a vertical magnification Gv greater than the horizontal optical power Ph. at horizontal magnification Gh. Optical power and/or magnification may vary in directions perpendicular to the optical axis.

Claims (10)

Light module (8; 108) for a motor vehicle (2), comprising:
- an optical projection device (12; 112) with a focus (12.3; 112.3), an entry face (12.1; 112.1) and an exit face (12.2; 112.2);
- an imager (10; 110) forming a matrix (10.1) of light sources (10.2), arranged between the focus (12.3; 112.3) and the entrance face (12.1; 112.1) so that the optical device of projection (12; 112) can project an enlarged image of said imager (10; 110);
characterized in that
the imager (10; 110) has a width l and a height h, the entry face (12.1; 112.1) and/or the exit face (12.2; 112.2) has a width L and a height H, where L >l, H>h, and Ll>Hh, so that the light module (8; 108) has a horizontal field of view greater than a vertical field of view, when said light module is oriented in the mounting position on the motor vehicle (2). Light module (8; 1108) according to claim 1, in which L-l>n∙(H-h), where n=2, preferably n=3, more preferably n=5. Light module (8; 108) according to one of claims 1 and 2, in which the imager (10; 110) comprises a center in a vertical direction and the optical projection device (12; 112) comprises an optical axis ( 6; 106), said center being offset downwards relative to said optical axis (6; 106), when the light module (8; 108) is oriented in the mounting position. Light module (8; 108) according to one of claims 1 to 3, in which a horizontal projection of the imager (10; 110) on the input face (12.1; 112.1) is completely included in said face. input, when the light module (8; 108) is oriented in the mounting position. Light module (8; 108) according to one of claims 1 to 4, in which the imager (10; 110) is arranged between the focus (12.3; 112.3) and the entrance face (12.1; 112.1) so to obtain an enlargement rate of the projected image of between 1.5 and 2.5. Light module (8; 108) according to one of claims 1 to 5, in which the optical projection device (12; 112) has a horizontal optical power Ph and a vertical optical power Pv, where Ph≠Pv, preferably Ph< Pv, when the light module (8; 108) is oriented in the mounting position. Light module (8; 108) according to one of claims 1 to 6, in which the optical projection device (12; 112) has a horizontal magnification Gh and a vertical magnification Gv, where Gh≠Gv, preferably Gh<Gv, when the light module (8; 108) is oriented in the mounting position. Light module (8; 108) according to one of claims 1 to 7, in which the optical projection device (12; 112) is a lens, preferably comprising an anti-reflection treatment on the entrance face (12.1; 112.1 ) and/or on the exit face (12.2; 112.2). Light module (108) according to claim 8, in which the lens (112) extends horizontally over at least 80% of the width L with a constant cross section. Lighting device comprising a housing, a closing glass (14; 114) of the housing and a light module (8; 108) housed in the housing, in which the light module (8; 108) is according to one of claims 1 to 9, and, the optical projection device being a lens (12; 112) formed directly on an interior face of the closing glass (14; 114).