FR3010772A1 - LIGHT EMITTING DEVICE FOR MOTOR VEHICLE PROJECTOR - Google Patents

Abstract

The subject of the invention is a device for emitting an output light beam along an optical axis (2) and with a cut-off profile, in particular for a motor vehicle, said device comprising: a light source (1); an optical element (3) for propagation of light rays, formed of a single solid piece and comprising: an input portion (10) through which rays coming from the light source are introduced into the optical element (3) ( 1), and an output portion (30) through which the output light beam is projected, - a beam intercept surface (23) configured to form the cutoff profile, the intercept surface is a wall of the optical element (3) located in an intermediate portion (20) of the optical element (3) between the input portion (10) and the output portion (30) along the optical axis (2).

Description

The present invention relates, in particular, to a light-emitting device. A preferred application relates to the automotive industry for the production of signaling and / or lighting devices, in particular vehicle headlights. In the latter area, we know lighting modules or projectors, among which are traditionally found low beam, or codes, range on the road around 70 meters, which are used primarily at night and whose beam distribution light is such that it does not dazzle the driver of a crossover vehicle. Typically, this beam has a cut in the upper part with a horizontal portion, preferably about 0.57 degrees below the horizon, so as not to illuminate the area in which should be the driver of a vehicle coming in the opposite direction The publication EP-A1-1 357 334 is part of this technology by forming a lighting module which produces a beam cutoff, by means of a light source, a reflector rays from the source and a folder allowing, by reflection, generating a cutoff profile. Downstream of the folder, the rays are projected via an exit lens. This anteriority has a relatively complex structure because of the path followed by the rays until the output of the module path defined by specific reflection surfaces employing reflective coatings. The invention solves all or part of the disadvantages of current techniques. One aspect of embodiments of the invention is a light-emitting device for generating a light beam with a cut-off profile, the device comprising: - a light source, - an optical element for propagation of light rays, formed of one solid piece and comprising: an input portion through which are introduced into the optical element rays coming from the light source, and an output portion through which the output light beam is projected, - a surface of It is advantageous for the intercepting surface to be a wall of the optical element located in an intermediate portion of the optical element between the input portion and the following output portion. the optical axis.

A potential advantage of the invention is not to make absolutely absolutely necessary reflection phases on reflective coatings as is the case of EPA1-1 357 334. Indeed, the propagation of the rays in the optical element is based on the principle of the formation of dioptres so as to ensure internal reflections. This propagation in a single medium is also favorable to the optical efficiency relative to the typical technical solutions for which the rays often cross multiple interfaces. The optical element, yet in one piece, further provides functions hitherto performed by a plurality of members and in particular a reflector, a folder and an output lens. It is easily understood that the invention significantly streamlines the configuration of the device. Moreover, being a monobloc optical element, any alignment problem is avoided. In addition, preferably, the light source is placed relatively to the optical element so that its mean radius is directed along the optical axis.

Thanks to this aspect of the invention, the rays of the source are originally directed substantially along the optical axis. The optical element may thus preferably have a relatively elongated shape within which the rays evolve from the outset along the longitudinal dimension of the optical element. The state of the art, as in the case of EP-A1-1357334, encourages the formation of a beam coming from the source as it is directed towards a reflector (generally elliptical), which induced that a portion of the rays of the source initially take a direction substantially opposite to the direction of propagation to the output face of the device causing losses. The invention overcomes this prejudice with a source oriented so that its mean radius is along the optical axis.

Advantageously, the source emits light in the form of a cone having an axis, the overall direction of emission of the source being given by this axis. In another optional situation of the invention, the interception surface is arranged to reflect towards the output portion, in particular by total internal reflection, the light rays reaching it. According to one possible aspect of the invention, the interception surface forms a diopter between a medium constituted by the optical element and an external medium of refractive index different from that of the optical element. The difference in indices between the optical element and another medium such as air is preferably exploited so that the implementation of mirror surface of the conventional folding type is suppressed at this level, the interception surface functioning as a diopter.

Optionally, the input portion has a face through which the rays coming from the source penetrate, this face having a cavity shape so as to produce an optical element whose focus receives the source. In this case, an advantageous possibility is that the cavity has a first convex surface portion in the direction of the focal point where the source is located, for example symmetrical of revolution along the optical axis; the first surface portion is surrounded by a second portion of concave orientation surface, possibly of revolution along the optical axis. The profile of the second surface portion may be shaped so as to obtain a homogeneous distribution of the light rays at the output of the optical element. For example, the second surface portion may have, in a vertical plane containing the optical axis, a profile having a point of inflection. According to an additional possibility, the intermediate portion comprises a recessed area at which the intercepting surface is located. Thus, a relief shape, directly resulting from the manufacture of the optical element, creates the interception surface. The intercepting surface can thus be located on one of the sections of this recessed area. Other characteristics, optional and not imitative, are set out below, being noted that they can be implemented separately or in any combination between them: the input portion comprises a collector configured to direct light rays of the light source introduced into the optical element towards a focusing zone located on the intercepting surface. Optionally, this zone may comprise or consist of a focal point or two or a multitude of focal points, or a line of focal points.

The collector is configured to reflect rays from the light source, in particular by total reflection, to the focusing zone. The collector wall has an elliptical profile. The recessed area has a ridge. the focus area is on the ridge. the peak is located at the optical axis. the ridge has a line in a horizontal plane. the line comprises a first section and a second section connected by a turn and offset along the optical axis. the interception surface comprises a first portion followed by a second portion along the optical axis, the first portion and the second portion having different inclinations relative to the optical axis.

The first part is configured to intercept rays coming from a part of the input portion located on the same side, in a vertical plane containing the optical axis, as the intercepting surface and in that the second part is configured to intercept rays from a portion of the input portion located on an opposite side, in a vertical plane containing the optical axis, at the intercept surface. the second part is parallel to the optical axis. the second portion includes a first edge located at the junction between the first portion and the second portion, a first portion of the focus area being located on the first edge. the second portion includes a second edge opposite the first edge, a second portion of the focus area being located on the second edge. the optical element has an outer surface contained in a circular cylindrical envelope axis coinciding with the optical axis. the optical element has an outer surface contained in a torus portion shaped envelope directed on an angular sector in a horizontal plane containing the optical axis. The hollow zone is located below the optical axis along the vertical.

The optical element is made of a transparent material. The optical element has a refractive index greater than or equal to 2 and may comprise PMMA (polymethyl methacrylate) or a polycarbonate PPC (carbonate polypropylene). It can be obtained by injection.

The peak zone is located at the optical axis. The light source comprises one or more light-emitting diodes. The optical element comprises a longitudinal axis coincides with the optical axis the input portion, the output portion and the intermediate portion sharing this axis. Another aspect of the embodiments of the invention relates to a lighting system comprising a first device and a second device, the two devices being configured for projecting parallel output beams, advantageously towards the front of a vehicle. .

Another object of the invention is a vehicle equipped with at least one device of the invention and / or at least one system as indicated above.

Other characteristics, objects and advantages of the present invention will appear on reading the detailed description which follows, and with reference to the appended drawings given as non-limiting examples and in which: FIG. 1 shows in section along a plane vertical passing through the optical axis an embodiment of the invention. Figure 2 continues this example with the schematization of the propagation of some light rays. Figure 3 illustrates in perspective a first form of the optical element and the figure is a similar view for another form of the optical element.

FIG. 5 shows, in the form of FIG. 3, advantageous focusing of rays. FIG. 6 illustrates another possible focusing, associated with the shape of FIG. 4. FIG. 7 schematizes rays participating in the output beam in the optical element form of FIG. 3. FIG. 8 schematises beams participating in the beam Fig. 9 shows a principle of interception of rays from an upper part of the optical element on an interception surface according to an embodiment of the invention. invention and Figure 10 reveals interception for rays from a lower part. Figure 11 is a possible variant of the input portion of the optical element. Fig. 12 is an isolux curve diagram showing an example of cutoff obtained. The terms "vertical" and "horizontal" are used in the present description to designate directions, including beam-cutting directions, in an orientation perpendicular to the horizon plane for the term "vertical", and in a parallel orientation. in terms 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 here considered as a minor variation around the two preferred directions.

The term "bottom" or lower part generally means a part of an element of the invention located, in a vertical plane, below the optical axis. The term "top" or "top" refers to a portion of an element of the invention located, in a vertical plane, above the optical axis.

By a single piece for the formation of the optical element is meant that the latter is a one-piece assembly without changing the medium during the propagation of the rays within it. The element can be obtained from the outset in a single block, for example by injection of polymer material, or be derived from the assembly of several components.

The term "parallel" or the concept of axes includes here in particular with manufacturing or mounting tolerances, substantially parallel directions or substantially coinciding axes within this framework. The cuts produced by the device of the invention may furthermore have any orientation in space.

The cut-off profile preferably refers to the formation of an output beam that is not uniformly distributed around the optical axis due to the presence of a zone of least light exposure, this zone being substantially delimited by a cut-off profile. which may be formed by at least two, and in particular three line segments forming an angle between them or have a more complex shape in turns such as the cut known as "kink". Furthermore, the invention may associate additional devices for projecting other beams alternately or in addition to the beam produced by the light emitting device described in more detail below. The case shown in the various figures is particularly suitable for installation in a projector at the front of a motor vehicle. The device of the invention comprises a light source 1 advantageously configured to emit light rays with a mean direction oriented along an axis coincident with an optical axis 2 of the device and of the optical element 3. The light source 1 may consist of one or more sources, and more particularly one or more light-emitting diodes (LEDs). In the case of a plurality of LEDs, it is advantageous to position them in the same plane. The LEDs emitting substantially in a half-space limited by their layout plan, the average direction of emission is typically perpendicular to the plane of the LED. In the case of the invention, the direction of the optical axis 2 of the device is chosen for this direction. This direction may be horizontal.

In the case of the example shown, the light source 1 consists of a single LED. The light source 1 cooperates with an optical element 3, several variant shapes of which are given in the figures.

In general, the optical element 3 comprises firstly an input portion 10. The latter includes a face 11 through which the rays coming from the source 1 enter. The face 11 has a cavity shape so as to producing an optical member whose focus receives the source 1. The cavity has a surface portion 11b, convex towards the home where the source 1 is located and advantageously symmetrical of revolution along the optical axis. The surface 11b is surrounded by a surface 11a, also of revolution along the optical axis 2 and concave orientation. The surface 11a is preferably spherical of center coincides with the home where the source 1 is located. Entering the input portion 10 by the face 11 thus defined, the rays then propagate in the portion 10. They are maintained in the element optical reflection of the peripheral wall of the portion 10. At this level, it plays on a dioptric function of the wall 12 to operate a redirection of the rays to a further downstream portion of the optical element 3. In this sense, this part of the input portion 10 forms a collector 15. FIG. 2 illustrates reflected rays 4 coming from the wall 12 of the collector 14.

Some spokes 4 are from a lower part of the collector, others from an upper part. It will be explained later that the invention, in a particular embodiment, treats differently these rays 4. The spokes 4 are directed towards an intermediate portion 20 where a cut occurs, before exiting through an output portion 30. As a preferred, the collector 14 is configured to focus the reflected rays 4 as in the case of Figure 2, to a focus location also here called place secondary foci. The wall 12 is constructed as a consequence of the desired focus. The intermediate portion 20 advantageously extends along the optical axis 2 as the input portion 10. It nevertheless has a geometrical rupture zone revealed by the hollow zone 21 by visible in Figures 1 and 2 for example. This zone 21 forms a cavity relief in the direction of the core of the optical element 3, towards the optical axis 2. FIGS. 1 to 10 give examples of specific shapes of hollow zone 21. Generally, it can be acting, in vertical sectional view, a notch defined by the edges of a dihedron forming an angle whose apex is directed towards the inside of the intermediate zone 20 and constitutes a ridge 22 (it is not necessary that crest 22 is one-dimensional). The peak portion 22 of the zone 21 is the portion of the space where the light rays interfere with the recessed area. This interference part forms the interception surface allowing the creation of a cutoff profile. The interception surface is at the interface with the environment surrounding the optical element 3, such as air, so that a diopter is produced at this level. In a first embodiment, the interception surface comprises a single border forming the peak 22, at the top of the hollow zone 21. This corresponds to the variants of FIGS. 3 to 8 on which a linear peak is noted along the width of the optical element (that is, the dimension perpendicular to the optical axis in a horizontal plane). The linear peak may be rectilinear or curved (as in Figure 4 in particular) or be the combination of linear forms. For example, FIG. 3 shows a ridge in two sections 22a, 22b which may be straight segments or curves, the two sections being joined, for example substantially to half the width of the optical element 3, by a turn 22c. The turn and the two sections may extend in a horizontal plane. This case is particularly suitable for the formation of a kink-type bend profile. In the embodiment shown in FIGS. 2, 9 and 10, the interception surface is more complex and comprises at least two parts, namely a portion 27 followed by a portion 28 in the direction of the optical axis 2. It will be understood that these portions 27, 28 make it possible to define two borders 29a, 29b which may be distinct privileged places of cut formation. The portion 28 can be oriented parallel to the optical axis 2. With this configuration, it is advantageous to produce a differentiated focusing of the reflected rays 4 according to whether they come from an upper part 13 or a lower part 14 The following is the principle of this focusing in a general case and then in the case of the crest configuration 22 with two edges 29a, 29b. The rays coming from the source 1 are advantageously directed by the input portion 10 so as to converge towards a place of secondary foci 26 located on the interception surface. The place of foci 26 is shown in phantom in Figure 5 which reveals a shape that can take this place. The concentration of rays can be done in a quasi-punctual zone in this case, which implies that the collector concentrates the reflected rays 4 at a point or a small zone of space around a midpoint whatever the place of reflection on the wall 12.

The place of the secondary foci can still be formed according to a line of focus as in Figure 6 where the dashed lines reveal a place 26 of curvilinear shape. In this situation, all the rays emitted from a point of the source 1 and contained in a vertical plane passing through this point focus at a point of the place of foci 26 and the rays emitted by the point of the source and contained in a non-vertical plane passing through this point are reflected in parallel directions to each other. Thus, at the place of hearths, the shape of intercepting surface and the focus adopted determine the cutoff. FIG. 12 gives an example of isolux curves obtained by virtue of the invention for a projection at a predetermined distance; the cutoff zone is identified at the mark 5. When the ridge forms a surface of interception 23 with two borders 29a, 29b, the focus is advantageously different depending on the case. If the reflected rays come from the lower part 14 of the collector 15, the wall 12 (in association with the input face 11) is preferentially configured so as to converge the rays 4 to a first set of foci of the place of secondary foci 26, this assembly being represented in FIG. 2 by the bottom focus 24. If the reflected rays come from the upper part 13 of the collector 15, the wall 12 (in association with the input face 11) is preferably configured so as to make converging the radii 4 towards a second set of foci of the locus of secondary foci 26, this assembly being represented in FIG. 2 by the high focus 25. It should be noted that FIGS. 9 and 10 respectively diagrammatically show the focusing of high radii 4 and low radii , with two variants of peak 22 according to the dimensions of the second part 28. According to one possibility, the length, along the optical axis, of the second part is smaller when source 1 is smaller. Without limitation, this length can be of the order of 2 to 4 cm, preferably 3 cm. The angle of the portion 27 may be in particular between 0 and 45 ° with respect to the direction of the optical axis 2. The rays which are not intercepted by the intercepting surface 23 are propagated towards the exit portion 30 of the optical element 3. The latter portion acts as a projection lens and delivers the output beam through an exit face at the mark 31 in FIG. 1. FIG. 1 illustrates a convex section of the face 31 along a vertical plane passing through the Optical axis 2. The ray output is for example illustrated in two variants in FIGS. 7 and 8. The examples shown give two variants of overall shape for the optical element. In the case of FIGS. 3, 5 and 7, the section of the element, in a vertical plane perpendicular to the optical axis 2, is substantially circular, except on specific zones such as the hollow zone. on the other hand, the optical element 3 is elongated so that it fits into a cylindrical envelope of axis directed along the optical axis. In the case of Figures 4, 6 and 8, the section shown in Figure 1 is at least in the intermediate portion 20 and / or the output portion 30, reproduced by rotation about an axis perpendicular to the optical axis and advantageously vertical. The section of the optical element 3, in a plane perpendicular to that of Figure 1 then comprises a portion in the form of an angular sector for example between +/- 10 ° (ie 20 °, for example centered on the optical axis 2) and +/- 70 ° (ie 140 °, for example centered on the optical axis 2); the beam will be all the wider as this angle will be high. The zone of the optical element in question thus has a shape of envelope of the toroidal type, in particular at the level of the output portion 30. FIG. 11 provides an alternative to the surface form 11 shown in FIG. 1 and 2 in particular. Part 11a is modified so as to distribute differently the energy of the beam emitted by the source 1. In the case illustrated, the portion 11a comprises a convex portion towards the source 1 extending from the portion 11b. The convex zone is followed by a concave zone. It is understood that the surface variations (concavity, convexity) modify the inclination of rays entering the inlet portion 10 so that the wall 12 of the collector 15 is not uniformly impacted by the rays of the source. The invention is not limited to the previously described embodiments but extends to all embodiments in accordance with his spirit.

Claims (19)

REVENDICATIONS1. Device for emitting a light beam along an optical axis (2) and with a cutoff profile, in particular for a motor vehicle, said device comprising: - a light source (1), - an optical element (3) for propagation of light light rays, formed of a single solid piece and comprising: an input portion (10) through which rays coming from the light source (1) are introduced into the optical element (3), and an output portion ( 30) through which the output light beam is projected, - a beam intercept surface (23) configured to form the cutoff profile, characterized in that the interception surface (23) is a wall of the element optical element (3) located in an intermediate portion (20) of the optical element (3) between the input portion (10) and the output portion (30) along the optical axis (2). 2. Device according to the preceding claim, characterized in that the light source (1) is placed relatively to the optical element (3) so that its overall direction of emission is directed along the optical axis (2). 3. Device according to one of the preceding claims, characterized in that the interception surface is arranged to reflect towards the output portion, in particular by total internal reflection, the light rays reaching it. 4. Device according to the preceding claim wherein the interception surface (23) forms a diopter between a medium consisting of the optical element (3) and an external medium of refractive index different from that of the optical element ( 3). 5. Device according to one of the preceding claims, characterized in that the input portion comprises a face through which penetrate the rays from the source, this face having a cavity shape so as to achieve an optical member whose focus receives the source. 6. Device according to one of the preceding claims wherein the input portion (10) comprises a collector (15) configured to direct light rays of the light source introduced into the optical element to a focusing zone located on the interceptor surface (23). 7. Device according to the preceding claim, characterized in that the collector (15) is configured to reflect rays from the light source (1), in particular by total internal reflection on a wall of the collector (15), to the zone of focusing. 8. Device according to one of the preceding claims wherein the intermediate portion (20) comprises a recessed area (21) at which is located the intercept surface (23). 9. Device according to the preceding claim in combination with one of claims 6 or 7, characterized in that the recessed area has a peak (22), the focusing area being located on the ridge (22). 10. Device according to the preceding claim wherein the peak (22) is located at the optical axis (2). 11. Device according to the preceding claim wherein the ridge (22) has a line located in a horizontal plane. 12. Device according to the preceding claim wherein the line comprises a first section (22a) and a second section connected (22b) by a bend (22c) and offset along the optical axis (2). 13. Device according to claim 8 wherein the interception surface (23) comprises a first portion (27) followed by a second portion (28) along the optical axis (2), the first portion (27) and the second portion (28) having different inclinations relative to the optical axis (2). 14. Device according to the preceding claim, characterized in that the first portion is configured to intercept rays coming from a portion of the input portion (10) located on the same side, in a vertical plane containing the axis. optical (2), that the intercepting surface (23) and that the second portion is configured to intercept rays coming from a portion of the input portion (10) located on an opposite side, in a vertical plane containing the optical axis (2) at the intercept surface (23). 15. Device according to the preceding claim wherein the second portion (28) is parallel to the optical axis (2). 16. Device according to one of claims 13 to 15 in combination with one of claims 6 or 7, wherein the second portion (28) comprises a first edge (29a) located at the junction between the first portion (27). and the second portion (28), a first portion of the focus area being located on the first edge. 17. Device according to the preceding claim, wherein the second portion comprises a second edge (29b), opposite the first edge (29a), a second portion of the focusing zone being located on the second edge. 18. Device according to one of the preceding claims wherein the optical element (3) has an outer surface contained in a circular cylindrical casing axis coinciding with the optical axis (2). 19. Device according to one of the preceding claims wherein the optical element (3) has an outer surface contained in a torus portion shaped envelope directed on an angular sector in a horizontal plane containing the optical axis (2). .