EP1564481A1 - Lighting module for vehicle headlamp, reflector for such a modul and headlamp comprising this modul - Google Patents

Abstract

The module has a light source including a plane surface (9) provided in a transparent volume (10). A reflector (12) has a focal point in a point source (17) of the source. The point source is selected, such that light rays emitted by the point source are deviated by refraction at the output of the volume. The reflector is arranged, such that the deviated rays, after reflection on the reflector, becomes parallel to a preset direction. An independent claim is also included for a light projector including a module.

Description

The invention relates to a light projector module for a vehicle automobile having a light source having a flat surface, immersed in a volume of transparent material having a refraction greater than 1, and a reflector having a focus at a point from the source.

The invention relates more particularly, but not exclusively, to a such module whose light source is constituted by a diode electroluminescent, hereinafter referred to by the abbreviation "led", whose surface transmitter is protected by a hemispherical volume, usually in one transparent polymer.

The invention aims, above all, to provide a projector module light source which makes it possible to obtain a light beam with cut-off, or presenting maximum illumination offset vertically, with a reduced number of components while maintaining a good light output.

In particular, it is desired to obtain a cut-off or pseudo-cut beam for a road function or for a DRL supplement (fire diurnal), especially with LEDs called "luxuryon", Lambertian type. In such LEDs, the luminescent material forming the light source is located in a plane.

It is also desirable that the module has a footprint as small as possible, in particular lower than that of projectors comprising elliptical reflectors and lenses.

According to a first aspect of the invention, a projector module luminous of the kind defined previously is such that the point of the source the focal point of the reflector is chosen in such a way that the radii light emitted by this point are deflected by refraction while leaving the volume transparent to pass through the air, and that the reflector is constructed in such a way that these light rays deviated, after reflection on the reflector, become substantially parallel to a predetermined direction.

In another aspect, the light projector module of the kind defined previously has a light source immersed in a volume hemispherical transparent material and is such that the point of the source light at the focus of the reflector is moved away from the center of the volume hemispherical, and the reflector comprises / consists of a surface stigmatic between the point of the source and a straight segment ahead or behind the surface of the reflector.

According to yet another aspect, the light source is immersed in a hemispherical volume of transparent material and the module is such that the point of the light source at the focus of the reflector is removed from the center of the hemispherical volume, the reflector being constructed in such a way that substituting at the point of the light source a frosted point of the plane base of the hemispherical volume and by illuminating this point frosted by a laser beam, one obtains with the optical system constituted by / including the volume hemispheric and the reflector a beam to infinity constituted by a segment horizontal, or by a point.

Preferably, the light source is a led (English abbreviation to designate a light-emitting diode) immersed in a volume hemispherical transparent material having a flat base turned to the side opposite to the reflector.

The focus of the reflector may be located at a point near an edge of the light source so that a light beam cut is obtained. With the focus located at a point near the upper edge (or front) of the source bright, we get a cut-off beam above a horizontal line, especially for a road or DRL function (that is to say, the light is found above the cut in these cases). With the focus in one next to the lower (or rear) edge of the light source we obtain a cut-off beam below a horizontal line (that is, in In this case, the light is under the cut, as in the case of a fire. intersection).

The wavelength of the light rays after reflection on the reflector is advantageously a cylindrical surface admitting an axis on which they rely on reflected light rays.

The invention also relates to a reflector for such a module characterized in that its surface is such that light rays from a point located at the focus, and refracted out of a volume of transparent material surrounding the focus, become reflective parallel to a direction predetermined.

The invention also relates to a vehicle light projector car having at least one module as defined above. The The projector may have several modules that individually bundles of different characteristics to produce a global beam satisfactory.

Fig.1 est un schéma explicatif, en coupe verticale d'un réflecteur en forme de paraboloïde avec une source plane orthogonale à l'axe optique.

Fig.2 est un schéma en coupe par un plan vertical d'un module de projecteur lumineux selon l'invention.

Fig.3 est une vue schématique partielle, avec parties coupées, suivant la flèche III de Fig.2.

Fig.4 est une coupe verticale schématique d'un projecteur pour fonction route selon l'invention.

Fig.5 est une vue schématique en perspective d'un module selon Fig.4.

Fig.6 illustre un réseau de courbes isolux obtenues sur un écran orthogonal à l'axe optique du module de Fig.4.

Fig.7 est un réseau des courbes isolux obtenues avec un module donnant un faisceau code large et

Fig.8 montre, semblablement à Fig.7, les isolux d'un faisceau code focalisé.

The invention consists, apart from the arrangements described above, in a certain number of other arrangements which will be more explicitly discussed hereinafter with regard to exemplary embodiments described with reference to the appended drawings, but which are not in no way limiting. On these drawings:

Fig.1 is an explanatory diagram, in vertical section of a paraboloid-shaped reflector with a plane source orthogonal to the optical axis.

Fig.2 is a sectional diagram through a vertical plane of a light projector module according to the invention.

Fig.3 is a partial schematic view, with cut parts, along the arrow III of Fig.2.

Fig.4 is a schematic vertical sectional view of a road function projector according to the invention.

Fig.5 is a schematic perspective view of a module according to Fig.4.

FIG. 6 illustrates a network of isolux curves obtained on a screen orthogonal to the optical axis of the module of FIG.

FIG. 7 is a network of isolux curves obtained with a module giving a wide code beam and

Fig.8 shows, similarly to Fig.7, the isolux of a beam focused code.

Fig.1 is a diagram intended to facilitate the understanding of the description which follows. In Fig.1 a reflector 1, constituted by a paraboloid, admits a focus 2 located on the optical axis 3. A plane light source 4 is disposed in a plane orthogonal to the axis 3 and passing through the focus 2. The edge Source 4 is located at focus 2. Light rays such as 5a emitted by the lower edge of source 4 come from the focus and are reflected in 5b parallel to the optical axis. On the other hand, rays such as 6a from the upper edge 7 of the source 4 are reflected at 6b according to a direction inclined downward from the horizontal. It is the same for all points of source 4 located above fireplace 2.

The light beam thus obtained has a cutoff line horizontal and the area lit by reflected rays such as 6b is below of this cutoff line.

The surface of the dish 1 is optically characterized by the fact that it transforms a spherical wave surface into a plane wave surface.

The source 4 of FIG. 1 is a theoretical light source emitting directly in the air that bathes the entire reflector 1 and the source.

FIG. 2 illustrates a concrete embodiment of a plane light source consisting of a high luminance led 8 which consists of a thin flat layer of luminescent material 9, constituting the light source proper and of a volume 10 of transparent material covering and protecting layer 9. Generally, volume 10 is hemispherical centered on the center O of the emitting layer 9, which may be square or rectangular. The base of the volume 10 is flat, constituted by a large circle and the layer 9 is immersed in the volume 10 at its flat base. The index of refraction of the material of volume 10 is greater than 1, that is, greater than the refractive index of the air in which all the elements are immersed.

The focus of a reflector 12 whose surface is different from that of a dish, is located on a point 11 of the source separated from the center O. This point 11 can be located on the lower edge of layer 9 which, according to the representation of Fig.2, lies in a vertical plane. A light ray such 13i emitted by point 11, meets the hemispherical surface of volume 10 at an angle of incidence that is not zero and the radius 13i out of the volume 10 in the air by being deflected by refraction to give the radius 13r. Another radius 14i, 14r from point 11 has been shown.

In the case where the focus of the reflector is located in the center O of the surface 9, the light rays from this point O are orthogonal to the surface hemispherical volume (zero angle of incidence) and exit without being deflected. But such an arrangement does not make it possible to obtain a light beam with cut.

According to the invention, the reflector 12 is constructed in such a way that the refracted rays 13r, 14r become rays 13e, 14e parallel to a determined direction Δ after reflection on the reflector 12. The direction Δ corresponds to the optical axis.

The surface of the reflector 12 is thus constructed to transform the source 11, immersed in the transparent hemispherical volume, in one a cylindrical wave surface source admitting as the axis of the wave surface a line A (FIG. 2) orthogonal to the optical axis Δ.

The line A is located at a distance D from the center O of the source. This distance D is a characteristic of the optical system, as is the angle α between the optical axis Δ and the horizontal direction OZ.

The point where the focus of the reflector is located can be defined by three coordinates xf, yf, zf in an orthonormal coordinate system whose two axes are OY, OZ according to Fig.2. The third axis OX not shown passes the point O and is perpendicular to the plane OYZ.

The family of reflector surfaces such as 12 is thus characterized optically, and mathematically.

The vector normal to the plane source 9 can be tilted on the horizontal.

As visible in FIG. 3, refracted rays such as 15r, 16r from point 11 and located in a plane different from that of Fig.2, are reflected on radii 15e, 16e which cut at a right angle the axis A of the cylindrical wave surface.

The surface of the reflector 12 is stigmatic between the immersed point 11 in a transparent sphere portion having a refractive index greater than 1, not centered on this point 11, and a segment of line A located in front of the surface 12 according to the direction of propagation of the light.

Alternatively, the line A could be behind the surface of the reflector 12 in which case the segment would be virtual; the section of the reflector 12 an orthogonal plane to the line A would be more "open" than in the case previous, without going to a hyperbole (it would be a hyperbole that in the absence of the sphere portion 10.).

By placing the focus of the reflector 12 on the lower edge 11 of the source 9, an upper-cut light beam, of the code or anti-fog.

To achieve a beam with lower cutoff, especially for a function or DRL function, the source 9 is arranged (see FIG. so that the focus of the reflector is located on the upper edge 17 of the source or near this edge. According to FIG. 4, which corresponds to a vertical section of a module for a route function, the plane of the source 9 is switched to forward with respect to the vertical direction. It's the same for the reflector 12. A ray 18r from point 17 is reflected along a radius 18e parallel to the horizontal optical axis. A ray such as 19r from a point of the source 9 located lower than the point 17 is reflected according to a 19th ray directed up and illuminating above the 18th ray. The cut is thus carried out at the bottom of the beam.

Fig.5. shows in perspective the projector module of Fig.4 with the reflector 12 whose upper part is inclined towards the front.

Fig.6 is an example of a network of isolux curves (i.e. constant illumination) obtained with a road searchlight according to FIG. remote screen determined, here 25 meters, the projector, orthogonal to the axis optical. The curves correspond to less and less illuminations strong from the center to the outside. The line H corresponds to the intersection of the screen with the horizontal plane passing through the optical axis, and the line V corresponds to the intersection of the screen with the vertical plane passing through the optical axis. The right and left limits ± 40% correspond to intersections with the screen of light rays from the source and forming with the optical axis, in the horizontal plane, an angle whose tangent is ± 0.4. The same explanation the limits indicated 20% and - 40% in the vertical plane.

According to Fig.6 it appears that the beam "road" is essentially located above the H line and is virtually equally distributed of the line V. The isolux corresponding to the maximum illumination is located within the network and is substantially tangent to line H, but being located above this line.

The isolux network of Fig.6 is obtained with a reflector 12 whose focus is located practically on the upper edge of the light source, with the parameters xf = 0, yf = + 0.5 mm, α = π / 4 and D = + 1000 mm.

To shift the maximum illumination downwards, simply move the focus of the reflector 12 at a point of the source 9 located lower than the edge 17. If the focus of the reflector 12 is located in the center of the source, the Isolux network has a maximum centered on the point of intersection of lines H and V. In addition, the surface 12 becomes that of a paraboloid of revolution and the output beam is a parallel beam, the distance D becoming infinite.

It is thus possible to measure the extent to the bottom of the beam of the road searchlight.

Fig.7 shows the isolux curves of a "wide" code beam with cut above the line H, obtained when the focus of the reflector 12 is located on the lower edge of the source 9. The beam of Fig.7 is obtained with xf = 0, yf = -0.5 mm, α = - π / 4 and D = + 75 mm. The distance D is relatively low, which spreads the beam horizontally.

Fig.8 shows the isolux of a less focused beam focused code horizontally as the beam of Fig.7, but still located essentially below the horizontal line H. The beam of FIG. 8 is obtained with xf = 0, yf = -0.5 mm, α = - π / 4 and D = - 1000 mm. The image of a point of the source is virtually infinite.

The beams of Figs. 7 and 8 may also be suitable for fires fog with horizontal cut.

A code projector must give a beam with a cut horizontally on one side of the vertical line V and a cut along a line tilted from the point of intersection of lines V and H and rising to the side where traffic (right for most European countries). The angle tilt is 15 °.

To achieve such a beam, it is possible to use several modules according to the invention some of which will have reflectors rotated at 15 ° on the horizontal to ensure the rising cut line.

A complete code, road or fog function will thus require several modules, each module comprising an LED. It is possible and desirable to vary the parameters such as D between the different modules for the same function.

The properties of a reflector 12 according to the invention can be verified as follows. From the knowledge of the led used, we can recover the corresponding hemispheric volume of this led or the rebuild in a transparent material having the same refractive index.

The lower face, or flat base of the hemispherical volume, is depolished a point corresponding to an apex of the transmitting source, or the focus of reflector if it is shifted.

This hemispherical volume is then installed in the optical system with the frosted dot in the focus, the base of the hemispherical volume being correctly oriented. We illuminate the point etched with a laser beam and we observe the infinite beam given by the reflector.

With a reflector according to the invention, a segment will be observed horizontal, which can be reduced to one point.

The search parameters including D and yf can be done by identification from a small number of points palpated on the surface of the based.

The light projector module according to the invention is particularly simple since it consists essentially of a reflector and a led. he allows to obtain a cut-off beam, without loss of light related to the presence of a cache. Compared to a simple paraboloid centered or defocused, a minimization of the maximum / low (or high) distance of the beam is obtained.

It should be noted that the volume of transparent material covering the led has has been described essentially as hemispherical.

Other volumes could cover this led, for example a volume conical of revolution.

Claims (10)

Motor vehicle headlamp module comprising a light source having a flat surface (9), immersed in a volume (10) of transparent material having a refractive index greater than 1, and a reflector having a focal point at a point of the source, characterized in that the point (11, 17) of the light source located at the focal point of the reflector (12) is chosen such that the light rays emitted by this point are deflected by refraction while emerging from the transparent volume (10) to pass into the air, and that the reflector (12) is constructed so that these light rays deviated, after reflection on the reflector, become substantially parallel to a predetermined direction. Motor vehicle headlamp module comprising a light source (8) immersed in a hemispherical volume (10) of transparent material having a refractive index greater than 1, and a reflector having a focal point at a point of the source, characterized in that the point of the light source (11, 17) located at the focus of the reflector (12) is spaced from the center of the hemispherical volume (10) and the reflector (12) comprises a stigmatic surface between the point of the source and straight segment (A) located in front of or behind the surface of the reflector. Motor vehicle headlamp module comprising a light source (8) immersed in a hemispherical volume (10) of transparent material having a refractive index greater than 1, and a reflector having a focal point at a point of the source, characterized in that the point (11, 17) of the light source located at the focus of the reflector (12) is spaced from the center of the hemispherical volume (10), the reflector being constructed such that by substituting at the point of the light source a frosted point of the plane base of the hemispherical volume and illuminating this point frosted by a laser beam, one obtains with the optical system comprising the hemispherical volume (10) and the reflector (12) an infinite beam consisting of a horizontal segment , or by a point. Light projector module according to one of the preceding claims, characterized in that the light source is a light-emitting diode immersed in a hemispherical volume (10) of transparent material having a flat base turned away from the reflector. Light projector module according to one of the preceding claims, characterized in that the focal point of the reflector is located at a point (11, 17) adjacent to an edge of the light source (9) so that a light beam at cutoff is obtained. Light projector module according to claim 5, characterized in that the focal point is located at a point (17) adjacent the upper edge (or front) of the light source (9) for a cut-off beam below a line horizontal, especially for a road or DRL function. Light projector module according to claim 5, characterized in that the focal point is located at a point (11) adjacent to the lower (or rear) edge of the light source for a cut-off beam above a horizontal line. Reflector for a light projector module according to one of the preceding claims, characterized in that the surface of the reflector (12) is such that light rays from a point (11,17) located at the focus, and refracted outgoing a volume (10) of transparent material surrounding the focus, become after reflection parallel to a predetermined direction. Motor vehicle headlamp having at least one module according to one of claims 1 to 7. Light projector according to claim 9 characterized in that it comprises several modules individually giving beams of different characteristics to produce a satisfactory overall beam.

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