Lighting module for vehicle headlamp, reflector for such a modul and headlamp comprising this modul

The invention relates to a headlight module for vehicle automobile comprising a light source having a planar surface, immersed in a volume of transparent material having an index of refraction greater than 1, and a reflector having a focus located at a point the source.

The invention relates more particularly, but not exclusively, a Such a module whose light source is a diode electroluminescent, hereinafter abbreviated as "LED", the surface Transmission is protected by a hemispherical volume, generally in an transparent polymer.

The invention aims especially to provide a projector module light that provides a light beam with cutoff, or having an offset of maximum illumination vertically, with a reduced number of components while maintaining a good luminous efficiency.

In particular, is desired to obtain a beam with cutoff, or pseudo-cleavage low for a road feature or to complement DRL (fire daytime), especially with LEDs called "Luxeon" kind of lambertian. 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 longitudinal as small as possible, in particular lower than headlamps fitted with elliptical reflectors and lenses.

According to a first aspect of the invention, a projector module light of the kind defined above is such that the point of the source light located in the focus of the reflector is selected such that the rays light emitted by this point are deflected by refraction outgoing volume transparent to pass through the air, and that the reflector is constructed so these light rays deflected after reflection on the reflector, become substantially parallel to a predetermined direction.

According to another aspect, the light of the kind defined projector module above includes a light source immersed in a volume hemispherical transparent material and is such that the point of the source light reflector located in the home is separated from the center of the volume hemispherical, and the reflector comprises / consists of a surface stigmatic the points of the source and a line segment located in front or behind the reflector surface.

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 light source located at the focus of the reflector is separated from the center of hemispheric volume, the reflector being constructed so that substituent at the point of the light source a ground point of the planar base of the hemispherical volume and by illuminating this frosted developed by a laser beam, obtained with the optical system consisting of / comprising the volume hemispherical reflector and a beam to infinity consisting of a segment horizontal, or a point.

Preferably, the light source is an LED (abbreviation to designate a light emitting diode) immersed in a volume hemispherical transparent material having a flat base side tour opposite 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 interrupter is obtained. With the focal point located at a point near the upper edge (or before) the source light is obtained a cutoff beam above a horizontal line, including a road or DRL function (that is to say that the light located above the cut in these cases). With the focus located in a point adjacent the lower edge (or rear) of the light source is obtained a beam to break below a horizontal line (that is to say in this case, the light is in the cut, as in the case of a fire crossing).

The wave surface of the light rays after reflection on the reflector is advantageously a cylindrical surface admitting an axis on which rely 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 in the home, and refracted coming out of a transparent material volume surrounding the home, become parallel after reflection in a direction predetermined.

The invention also relates to a headlight for a vehicle motor having at least one module as defined above. The projector can have multiple modules individually giving different characteristics of beams to produce a global beam satisfactory.

The invention consists, apart from the provisions disclosed above, in a number of other provisions which will be more explicitly discussed below in connection with the embodiments described with reference to the accompanying drawings, but are in no way limiting. In these drawings:<sl><li>1 is an explanatory diagram in vertical section of a reflector form of a paraboloid with a flat source orthogonal to the optical axis.</li><li>Fig.2 is a sectional diagram through a vertical plane of a module headlight of the invention.</li><li>Fig.3 is a partial schematic view, with parts cut away, according to arrow III in Fig.2.</li><li>4 is a schematic vertical section through a projector function route according to the invention.</li><li>Fig.5 is a schematic perspective view of a module according to Fig.4.</li><li>6 illustrates a network of curves obtained on a screen isoluxes orthogonal to the optical axis of Fig.4 module.</li><li>7 is a network of isolux curves obtained with a module giving a wide beam and code</li><li>8 shows, similarly to Fig.7, the isoluxes a code beam focused.</li></sl>

Fig.1 is a diagram to facilitate understanding of the description which follows. Fig.1 on a reflector 1, consisting of a paraboloid, 2 admits a home located on the optical axis 3. A planar light source 4 is arranged in a plane orthogonal to the axis 3 and passing through the focus 2. The board lower than the source 4 is located in the hearth 2. The light rays such as 5a issued by the lower edge of the source 4 from the home and are reflected 5b in parallel to the optical axis. By cons, rays such as 6a from the upper edge 7 of the source 4 are reflected 6b following a direction inclined downwardly with respect to the horizontal. It is the same for all points of the source 4 located above the hearth 2.

The light beam thus obtained has a cut-off line horizontal and the area illuminated by the reflected rays such as 6b is located below this cut line.

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

The source 4 1 is a theoretical plane emitting light source directly into the air which bathes the whole of the reflector 1 and the source.

2 illustrates a concrete realization of a planar light source constituted by an LED 8 at high luminance which consists of a thin planar phosphor layer 9 constituting the light source itself and a volume 10 of transparent material overlying and protecting layer 9. Generally, the volume 10 is centered hemispherical on the center O of the emitting layer 9, which may be square or rectangular. The basis of the volume 10 is flat, consists of a great circle and the layer 9 is immersed in the volume 10 at its flat base. The index refraction of the material of the volume 10 is greater than 1, that is to say greater than the air refractive index that bathes all the elements.

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

In the case where the focus of the reflector is located at the center O of the surface 9, the light rays from the point O are orthogonal to the surface hemispherical volume 10 (zero angle of incidence) and out without being deflected. But such a provision does not provide a light beam with cut.

According to the invention, the reflector 12 is constructed so that the refracted rays 13r, 14r become 13th-ray 14th parallel to a Δ direction determined after reflection on the reflector 12. The management Δ corresponds to the optical axis.

The reflector surface 12 is thus built to convert the source point 11, immersed in transparent hemispherical volume 10, in a source cylindrical wave surface having as its axis the wavefront a straight 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 well as the angle α Δ between the optical axis and the horizontal direction OZ.

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

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

The normal vector to the plane source 9 may be inclined to the horizontal.

As shown in Fig.3, rays deflected by refraction as 15r, 16r from the point 11 and located in a plane different from that of Fig.2, are reflected along the ray 15e, 16e which intersect at right angles the axis A of the cylindrical wavefront.

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

Alternatively, A could be right behind the surface reflector 12 which case the segment is virtual; Section 12 of the reflector by a plane orthogonal to the straight line A would be more "open" as in the case previous, short of hyperbole (that would be a hyperbole that the absence of the portion of a sphere 10.).

By placing the focus of the reflector 12 on the lower edge 11 of the source 9, there is provided a higher cut-off light beam, such code or anti-fog.

To realize a beam with lower cut-off, in particular for based road or DRL function, the source 9 is arranged (see Figure 4) in such so that the focus of the reflector is located on the upper edge 17 of the source or in the vicinity of this edge. According to Fig. 4, which corresponds to a vertical section a module for a drive function, the plane of the source is switched to 9 forwardly relative to the vertical direction. It is the same for the reflector 12. 18r radius from the point 17 is reflected along a ray 18th parallel to the optical horizontal axis. A ray as 19r from a point Source 9 located below the point 17 is reflected along a ray 19 directed upwards and lighting above the 18th ray. The cut is thus conducted in low beam.

Fig.5. Fig.4 is a perspective view of the projector module with reflector 12 whose upper part is inclined forwardly.

6 is an example network of isolux curves (that is to say constant illumination) obtained with a projector according Fig.4 road, on a remote screen determined by 25 meters, the projector orthogonal to the axis optical. The curves correspond to illuminations less and less strong center outward. The straight line H corresponds to the intersection of the screen with the horizontal plane passing through the optical axis, and the right corresponds to V the intersection of the screen with the vertical plane passing through the optical axis. The right and left limits ± 40% correspond to the intersections with the display 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 respect the limits indicated 20% - 40% in the vertical plane.

From Fig.6 it appears that the "road" is essentially beam located above the H line and is substantially evenly distributed on either side of the line V. isolux the maximum illuminance is located within the network and is substantially tangent to the line H, but being located above this line.

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

To shift the maximum illumination down, just move the focus of the reflector 12 at a point source 9 situated lower than the edge top 17. If the focus of the reflector 12 is in the center of the source, 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 metering the extended downwardly of the beam projector road.

Fig.7 montre les courbes isolux d'un faisceau code « large » avec cut above the line H, obtained when the focus of the reflector 12 is located on the lower edge of the spring 9. Fig.7 beam is obtained with xf = 0, yf = -0.5 mm, α = - π / 4 and D = 75 mm. The distance D is relatively low, thereby horizontally spreading the dipped beam.

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

The beams of Fig. 7 and 8 may also suit of lights fog horizontal cut.

A projector code should give a beam with a cut horizontal on one side of the vertical line V and a cut along a line inclined from the point of intersection of the lines V and H and amount on the side where is carried traffic (right for most European countries). The angle of inclination is 15 °.

To produce such a beam, one can use several modules according to the invention some of which will reflectors turned 15 ° on the horizontal for ensuring the upstream cut-off line.

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

The properties of a reflector 12 according to the invention can be tested as follows. From the knowledge of the LED used, you can recover the hemispherical volume corresponding to this LED or reconstruct in a transparent material having the same refractive index.

It dépolit the lower face, or flat base of the hemispherical volume in a point corresponding to a peak of the emitting source, or in the home of reflector if it is shifted.

then installing this hemispheric volume in the optical system with frosted item placed in the home, the base of the hemispherical volume being correctly oriented. frosted spot is illuminated with a laser beam and observe the beam to infinity given by the reflector.

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

Search parameters include D and yf can be done by identification from a limited number of probed points on the surface of the based.

The headlight module according to the invention is particularly simple since it basically consists of a reflector and an LED. he provides a cutoff beam without light loss due to presence of a cache. Compared to a single paraboloid focused or defocused, minimizing the maximum distance / low is obtained (or top) of the beam.

It should be noted that the volume of transparent material which covers the LED has been described as essentially hemispherical.

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