EP2199662A1 - Improved lighting module for automotive vehicle - Google Patents

Abstract

The module (1) has a light source (S) i.e. LED, placed in a concave reflector (2). A lens (3) is placed in front of the reflector and the source. The reflector is associated to a beam folder (4). A front edge (5) of the folder is formed by a flat curve with variable curvature, where a curvature in a point (M) is a continuous function of lateral coordinate (x) of the point. The reflector transforms a wave surface of the source into a wave surface restored to the curve. The lens provides an infinity image from the point for all rays contained in a plane perpendicular to the edge at given point.

Description

The invention relates to a lighting module for a motor vehicle headlamp, giving a cut-off light beam, of the kind comprising a concave reflector, at least one light source arranged in the concavity of the reflector to illuminate, in particular at least one upwards, and a lens situated in front of the reflector and the light source, the reflector being associated with a folder, in particular a horizontal folder, the upper surface of which is reflective for folding the beam coming from the reflector, said folder having an edge of clean front end to form the cut in the lighting beam.

By the term "folding" is meant a substantially flat and reflective plate.

A lighting module of the kind defined above is known from the patent EP-A-1 610 057 . Such a module makes it possible to obtain a very wide illumination beam with a clean cut across the entire width of the beam. This kind of module is well suited for lighting systems combining several modules with different optical axes and curvatures. A fog lamp generally uses two or three of these modules to give a light beam with a satisfactory distribution of illumination over the entire angular extent of the beam, in particular towards the angular limits of the beam.

It is however desirable to reduce the number of modules to be used to obtain a satisfactory beam, in particular fog.

The object of the invention is, above all, to propose a module of the kind defined previously which makes it possible to obtain a beam in which the distribution of the light is improved in order to increase the illumination of the angular extreme zones, in particular those located at about ± 35 ° C. ° on either side of the optical axis, without reducing the illumination of the central zone located substantially between + 10 ° and -10 ° on either side of the optical axis.

The invention also aims to provide a sufficiently improved lighting module to constitute alone a fog lamp meeting the requirements imposed.

• le réflecteur est déterminé pour transformer la surface d'onde provenant de la source en une surface d'onde se ramenant à la courbe à courbure variable du bord avant de la plieuse,
• et en ce que la lentille est déterminée pour donner d'un point (notamment tout point) du bord avant de la plieuse, pour tous les rayons contenus dans le plan perpendiculaire au bord avant de ladite plieuse au point considéré, une image à l'infini, notamment dans une direction inclinée par rapport au plan de la plieuse d'un angle fonction continue de la distance de ce point à l'axe optique (ou coordonnée latérale de ce point).

According to the invention, a lighting module of the kind defined above is such that the front edge of the folder is formed by a planar curve with variable curvature, the curvature at a point being a continuous function of the distance from this point to the optical axis, or lateral coordinate of this point,

• the reflector is determined to transform the wave surface from the source into a wave surface that is reduced to the curve with variable curvature of the front edge of the folder,
• and in that the lens is determined to give a point (especially any point) of the front edge of the folder, for all the rays contained in the plane perpendicular to the front edge of said folder at the point considered, an image at the infinite, especially in a direction inclined relative to the plane of the folder of a continuous function angle of the distance from this point to the optical axis (or lateral coordinate of this point).

The curvature of the front edge of the folder has, in particular, at least a maximum angularly located between the optical axis of the module and an angular limit of the beam. Preferably, the curvature of the front edge of the folder has a maximum on each side of the optical axis. Usually, the front edge of the folder is symmetrical with respect to this optical axis.

Preferably, the curvature of the front edge of the folder has a secondary maximum located on or substantially on the optical axis.

Generally, the wave surface coming from the source is comparable to a spherical wave surface,

The maximum curvature of the front edge of the folder is selected so that the illumination of the extreme angular zones of the beam, in particular in directions greater than or equal to ± 35 ° on either side of the optical axis, is reinforced, without reducing the illumination of the central area.

The surface of the reflector is such that light rays coming from the source and falling at points situated on the intersection of this surface and a normal vertical plane at the front edge of the folder, but separated from the source, are reflected in this vertical plane so as to converge at a point located at the intersection of the vertical plane and the edge of the folder.

Advantageously, the lighting module is provided so that the illumination in the central zone between -10 ° and + 10 ° on either side of the optical axis is maintained with respect to a basic module whose folder would have a circular front edge of radius equal to the mean radius of curvature of the front edge, while the areas located at -35 ° and + 35 ° on either side of the optical axis, and corresponding to lines listed 9 -1 and 9-2 according to the R19-3 standard, have a higher illumination than that obtained with said basic module.

Advantageously, the cut-off beam obtained is flat-cut, in particular being chosen between an anti-fog beam and a flat-cut code beam portion.

• le bord avant de la plieuse est formé par une courbe plane, notamment dans un plan horizontal, à courbure variable, la courbure en un point étant une fonction continue (sans saut de courbure) de la coordonnée latérale de ce point,
• le réflecteur présente une forme choisie de manière à ce qu'un rayon issu du centre de la source lumineuse et réfléchi par le réflecteur coupe le bord avant de la plieuse en étant contenu dans un plan normal à ce bord passant par ce point d'intersection,
• et la lentille est agencée pour donner d'un point du bord de la plieuse une image à l'infini dans le plan perpendiculaire au bord avant de la plieuse au point d'intersection.

The invention also relates to a lighting module for a motor vehicle headlamp, giving a cut-off light beam, comprising a concave reflector, at least one light source arranged in particular in the concavity of the reflector to illuminate, especially at least towards the high, and a lens located in front of the reflector and the light source, the reflector being associated with a folder, in particular horizontal, whose upper face is reflective for folding the beam from the reflector, said folder having a front end edge adapted to form the cut in the illumination beam, characterized in that:

• the front edge of the folder is formed by a plane curve, in particular in a horizontal plane, with variable curvature, the curvature at a point being a continuous function (without bending of curvature) of the lateral coordinate of this point,
• the reflector has a shape chosen so that a ray coming from the center of the light source and reflected by the reflector intersects the front edge of the folder being contained in a plane normal to this edge passing through this point of intersection ,
• and the lens is arranged to give a point of the edge of the folder an image at infinity in the plane perpendicular to the front edge of the folder at the point of intersection.

The invention also relates to a projector comprising at least one module as defined above.

The invention consists, apart from the arrangements set out above, in a number of other arrangements which will be more explicitly discussed below with respect to an embodiment described with reference to the accompanying drawings, but which is in no way limiting.

• Fig. 1 est une vue schématique simplifiée en perspective d'un module selon une première variante de l'invention.
• Fig. 2 est un schéma en perspective sous un autre angle, avec partie coupée ou arrachée, à plus grande échelle, d'une coupe verticale du module selon la figure précédente, avec représentation de rayons lumineux.
• Fig.3 est un schéma d'une coupe partielle de la lentille selon les figures précédentes pour le calcul.
• Fig. 4 est une vue schématique de dessus, à plus grande échelle, du bord avant de la plieuse du module selon les figures précédentes.
• Fig.5 est un diagramme représentant la variation du rayon de courbure de la plieuse du module selon les figures précédentes avec en abscisse la distance latérale à l'axe optique et en ordonnée le rayon de courbure en un point de la courbe, et
• Fig. 6 est un schéma de la distribution lumineuse, sur un écran, du faisceau produit par le module du module selon les figures précédentes de l'invention.
• Fig.7 à 9 se rapportent à une seconde variante de l'invention
• En se reportant à Fig.1 des dessins, on peut voir un module d'éclairage 1 pour projecteur de véhicule automobile, schématiquement représenté, ce module étant propre à donner un faisceau lumineux à coupure. Le module 1 comporte un réflecteur concave 2, au moins une source lumineuse S disposée dans la concavité du réflecteur pour éclairer au moins vers le haut, et une lentille 3 située en avant de la source S et du réflecteur 2, selon le sens de propagation du faisceau lumineux. Le réflecteur 2 est associé à une plieuse 4, constituée par une plaque plane réfléchissante, horizontale comme représenté sur Fig. 1. La plieuse 4, dont au moins la face supérieure est réfléchissante, comporte un bord d'extrémité avant 5 propre à former la coupure dans le faisceau d'éclairage. Lorsque la plieuse 4 est horizontale, la coupure du faisceau est horizontale et la zone éclairée est située au-dessous d'une ligne horizontale. En inclinant le plan de la plieuse 4 autour de l'axe optique horizontal du module, on peut incliner la ligne de coupure du faisceau.

On these drawings:

• Fig. 1 is a simplified schematic perspective view of a module according to a first variant of the invention.
• Fig. 2 is a diagram in perspective from another angle, with part cut or torn off, on a larger scale, of a vertical section of the module according to the previous figure, with representation of light rays.
• Fig.3 is a diagram of a partial section of the lens according to the preceding figures for the calculation.
• Fig. 4 is a schematic view from above, on a larger scale, of the front edge of the bender of the module according to the preceding figures.
• Fig.5 is a diagram representing the variation of the radius of curvature of the folder of the module according to the preceding figures with the abscissa the lateral distance to the optical axis and the ordinate the radius of curvature at one point of the curve, and
• Fig. 6 is a diagram of the light distribution, on a screen, of the beam produced by the module of the module according to the preceding figures of the invention.
• Fig.7 to 9 relate to a second variant of the invention
• Referring to Fig.1 drawings, we can see a lighting module 1 for motor vehicle headlamp, schematically shown, this module being adapted to give a light beam cut. The module 1 comprises a concave reflector 2, at least one light source S arranged in the concavity of the reflector to illuminate at least upwards, and a lens 3 located in front of the source S and the reflector 2, in the direction of propagation of the light beam. The reflector 2 is associated with a folder 4, consisting of a flat reflecting plate, horizontal as shown on Fig. 1 . The folder 4, of which at least the upper face is reflective, has a front end edge 5 suitable for forming the cut in the lighting beam. When the folder 4 is horizontal, the cutting of the beam is horizontal and the illuminated area is located below a horizontal line. By tilting the plane of the bender 4 around the horizontal optical axis of the module, it is possible to tilt the cut-off line of the beam.

The light source S is advantageously substantially punctual, in particular formed by a light-emitting diode enveloped by a globe or a hemispherical capsule, this diode having a light-scattering axis substantially orthogonal to the folder 4, and illuminating upwards.

According to the invention, in order to transfer the light beam towards the external angular zones from intermediate angular zones without penalizing the central zone, the front edge of the folder is given the shape of a plane curve with variable curvature. , whose curvature at a point is a continuous function of the distance x, or lateral coordinate, from this point to the optical axis Y, for the point considered.

As visible on Fig. 1, 2 and 4 in the central zone 5a of the edge the curvature is constant on either side of the optical axis; this part 5a corresponds to a circular arc of constant radius, centered on the optical axis Y. The ends of the arc 5a are connected, respectively, to an arc 5b1, 5b2 having a higher curvature. The radius of curvature (inverse of the curvature) of the arcs 5b1, 5b2 is smaller than that of the central part 5a.

A portion 5c1, 5c2 provides the connection between the ends of the zones 5b1, 5b2 with strong curvature with end arcs 5d1, 5d2 convex forward, having a curvature less than or equal to that of the central portion 5a. The intermediate zones 5c1, 5c2 are of variable convexity with respect to the adjacent zones. All of these areas "recedes" with respect to the circle of radius Ra as represented in figure 5 .

Areas with a high curvature 5b1, 5b2 make it possible to spread the beam laterally and to reinforce the illumination in the extreme angular zones, for example at ± 35 ° on either side of the optical axis Y, by decreasing the intensities in the intermediate zones, and without affecting the central part of the beam whose illumination mainly depends on the central zone 5a of the curve. Indeed, the area of the curve corresponding to the angles of the lines 8 according to the figure 6 5b) are small, the angles evolve rapidly with x, because of the strong curvature, so that there is more room for zones 5d, where the angles "more slowly" depending on x.

The central portion of the beam generally corresponds to an angle of ± 10 ° on either side of the optical axis and the angular extent of the central portion 5a of the folder is sufficient to ensure the desired intensity in the range ± 10 °.

It should be noted that if the front edge of the folder was formed by a circular arc, centered on the optical axis, it would be possible by reducing the radius of this arc, and thus increasing the curvature on the entire edge , to improve the illumination of the extreme angular zones, but this improvement would be accompanied by a reduction of the illumination in the central zone ± 10 ° on either side of the optical axis, which the invention allow to avoid.

The figure 4 represents the position of the centers of curvature for the different zones represented in figure 5 . C is the circle of radius Ra. O is the center of curvature for area 5a of radius Ra. 01 is the center of curvature for zone 5d2 of radius Rd. 02 is the center of curvature for the point of minimum radius of curvature (Rb), a point located at the end of zone 5b2. When traversing the zone 5b2 of the zone 5a towards the zone 5c2, the center of curvature of the plane curve 5 moves from 0 to O2. When moving from zone 5c2 in zone 5b2 to zone 5d2, the center of curvature moves from 02 to 01.

Fig. 5 illustrates the variation of the radius of curvature R at a point of the curve 5, as a function of its lateral distance, that is to say its distance x to the optical axis, range on the abscissa. The radius R, carried on the ordinate, corresponds to the inverse of the curvature. It appears that the radius R passes through two minimum values Rb, on either side of the optical axis, corresponding to the points of greatest curvature of parts 5b1, 5b2. The central portion has a radius of curvature Ra constant in the example and the end parts a higher radius of curvature Rd also constant.

The reflector 2 is determined to transform a spherical wave surface from the light source S into a wave surface returning to the curve 5 of the edge of the folder.

Folder edge 5 is a solution of a differential equation involving the radius of curvature R (x) as discussed further, which solution can be found numerically by choosing an arbitrary point of the edge 5. Preferably, the position from the source S being known, we take the point My ( Fig.2 ) of the edge belonging to the optical axis Y of the module, which axis passes through the center of the source; this reduces the choice of the point of passage to that of a simple real parameter, similar to the distance between foci in an ellipsoid.

Thanks to classical numerical methods (eg Runge-Kutta) the position (x, f (x), 0) of a current point M can be calculated with the desired accuracy (with the necessary calculation time). Fig. 2 ) X-axis abscissa, ordinate f (x) along the optical axis Y and zero altitude along the vertical axis Z. We can also calculate the tangent T at the edge 5 at this point M, by determining the direction vector of component 1, f '(x), 0 of this tangent T . We deduce the normal plane Em at the edge 5 at the point M considered. This normal plane is a vertical plane whose trace on the plane of the edge 5 is the normal NOT at the edge 5 at point M.

The reflector 2 is determined by a family of curves 2m, each curve 2m corresponding to the intersection of the reflector with a plane Em normal to the edge 5 at a current point M. Each curve 2m is located in a plane Em. The family of the curves 2m is obtained by moving the plane Em perpendicular to the edge 5.

A 2m curve must have the following property. We consider light rays i, i1, from the focus O center of the source S, and reaching the reflector 2 at current points P, P1 belonging to the plane Em. The points P, P1 are located on the curve 2m, which is such that the rays i, i1 are reflected along radii r, r1 pointing towards the point M of the edge 5. The rays reflecting r, r1 are therefore contained in the plane Em.

This property, and the choice of an arbitrary point, for example the point Py intersection of the reflector and the optical axis Y, define entirely the reflector 2, the curve 5 having been previously defined, by writing the constancy of the optical path from the source S to the edge 5 of the folder. The value of the optical path results from the choice of arbitrary points My and Py. The more detailed calculation is given later in this description.

The reflector 2 can thus be calculated as a parametric surface in x (dimension of a point M on the edge 5 of the bender, along the axis X) and according to the angle φ, this angle being that formed between a radius such that r1, returned by the reflector 2 and falling on the edge 5 at the point M, and the plane of the folder (see Fig. 2 ). The height of the folder is zero, z = 0.

The lens 3 can be determined as follows. The section, or intersection, 3Em of the lens 3 with the plane Em defined above, corresponds to the section of a stigmatic lens between the point M of the folding edge 5 of the folder and the infinite, this plane containing the axis of the stigmatic lens. This section 3Em is delimited by two dioptres: a diopter of entry 3Eme, and a dioptre of exit 3Ems. The material, glass or transparent plastic, of the section 3Em is between these two diopters.

One can choose arbitrarily one of the two dioptres of the lens. Generally one chooses the diopter of entry 3Eme. In the calculation example given below, this input diopter is constituted by a circular arc in the plane Em, convex towards the rear, of center Ω ( Fig.3 ) in the plane of the bender 5. The output diopter 3Ems is calculated so that a light ray u1, coming out of the lens 3 and coming from an incident ray q1 coming from the point M, is parallel to the horizontal plane of the folder 5.

The lens 3 could be parameterized in the same way as the reflector, but a mesh in (x, h), h being the height of the points on the input face of the lens (see Fig. 2 and 3 ) allows a simpler calculation. The lens 3 is not revolution, especially around a vertical axis.

Fig. 6 schematically illustrates the network of isolux curves obtained on a screen, generally at a distance of 25 m, with a module according to the invention. The illumination in the central zone between -10 ° and + 10 ° on either side of the optical axis is not decreased compared to a module whose folder would have a circular front edge of radius equal to the radius means of curvature of the edge 5 according to the invention.

On the other hand, the zones situated approximately at -35 ° and + 35 ° on either side of the optical axis, and corresponding to the lines listed 9-1 and 9-2 according to the R19-3 standard, have a higher illuminance. higher than that of a module with a folding machine in an arc. Areas in which light has been taken to be transferred to lines 9-1 and 9-2 correspond to substantially at intermediate lines 8-1 and 8-2 between the central zone and the extreme zones.

The invention thus allows optimization, in particular by the choice of R (x) from which the curve f (x) describing the front edge 5 of the folder is deduced, and offers greater flexibility. The optimization can result from comparative calculations made with different equations f (x) for curve 5.

It becomes possible to realize a fog lamp with a single module, while producing a beam that meets the regulatory requirements. A module according to the invention can also serve as a basic module for a code projector.

Examples of calculation are given below for the determination of the reflector 2 and the lens 3, with reference to the Fig.2 and 3 .

Reflector 2 calculation example

Let R (x) be the radius of curvature of the bending edge at a point M, of abscissa x, located on curve 5 of equation y = f (x).

équation différentielle en f, avec pour conditions initiales au point My : $$\begin{array}{c}\mathrm{f}\left(\mathrm{0}\right)\end{array}\mathrm{=}{\mathrm{Y}}_{\mathrm{o}}$$

$$\begin{array}{c}\mathrm{fʹ}\left(\mathrm{0}\right)\end{array}\mathrm{=}\mathrm{0}$$

soluble numérique sous la forme $$\mathrm{Yʹ}\mathrm{=}\mathrm{F}\left(\mathrm{x}\mathrm{Y}\right),\mathrm{où}Y=\left[\begin{array}{c}\mathit{fʹ}\left(x\right)\\ f\left(x\right)\end{array}\right]=\left[\begin{array}{c}{Y}_1\\ Y_2\end{array}\right]$$

The center of curvature at the point M is in the plane z = o. The radius of curvature R (x) is given by the formula: $$\frac{1}{R\left(x\right)}=\frac{-\mathit{f"}\left(x\right)}{{\left(1+\begin{array}{c}\mathit{f\text{'}}{\left(x\right)}^2\end{array}\right)}^{{}^3{/}_2}}$$

differential equation in f, with for initial conditions at the point My: $$\begin{array}{c}\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="imgf0003.png"\; state="\{\{state\}\}">f</figure-callout>}\left(\mathrm{0}\right)\end{array}\mathrm{=}{\mathrm{Y}}_{\mathrm{o}}$$

$$\begin{array}{c}\mathrm{f\text{'}}\left(\mathrm{0}\right)\end{array}\mathrm{=}\mathrm{0}$$

soluble digital in the form $$\mathrm{Y\; \text{'}}\mathrm{=}\mathrm{F}\left(\mathrm{x}\mathrm{Y}\right),\mathrm{or}Y=\left[\begin{array}{c}\mathit{f\text{'}}\left(x\right)\\ f\left(x\right)\end{array}\right]=\left[\begin{array}{c}{Y}_1\\ {\mathrm{<figure-callout\; id="2"\; label="Y"\; filenames="imgf0001.png"\; state="\{\{state\}\}">Y</figure-callout>}}_2\end{array}\right]$$

Tangent vector at point M: $$\begin{array}{cc}\left[\begin{array}{c}1\\ \mathit{f\text{'}}\left(x\right)\\ 0\end{array}\right]=\overrightarrow{T_m}& F=\left\{\begin{array}{c}-\frac{{\left(1+{{\mathrm{<figure-callout\; id="1"\; label="Y"\; filenames="imgf0002.png"\; state="\{\{state\}\}">Y</figure-callout>}}_1}^2\right)}^{{}^3{/}_2}}{\mathrm{<figure-callout\; id="1"\; label="R\; x\; Y"\; filenames="imgf0002.png"\; state="\{\{state\}\}">R\; </figure-callout>}\left(x\right)}& \\ Y_{}{}_1\end{array}\right\}\end{array}$$

au point MNormal vector (in the direction of the center of curvature): $$\frac{1}{\sqrt{1+\begin{array}{c}\mathit{f\text{'}}{\left(x\right)}^2\end{array}}}\left[\begin{array}{c}\mathit{f\text{'}}\left(x\right)\\ -1\\ 0\end{array}\right]=\overrightarrow{{\mathrm{not}}_m}$$

at point M

• Pour tout x, et pour tout v orthogonal à T _m (x),

Suppose the source placed in O:

• For all x, and for everything v orthogonal to T _m (x),

(point courant de la courbe 5). K est une constante arbitraire. $$\mathrm{P}\mathrm{=}\mathrm{M}\mathrm{+}\mathrm{\lambda }\overrightarrow{\mathrm{v}}\mathrm{où}\overrightarrow{\mathrm{v}}\mathrm{=}\mathrm{cos\; \phi }\overrightarrow{{\mathrm{n}}_{\mathrm{m}}}\mathrm{+}\mathrm{sin\; \phi }\overrightarrow{\mathrm{z}}$$

there is a current point P of the reflector such that: PM (x) + PO = K = optical path with M (x) P collinear to v
and $\mathrm{M}\left(\mathrm{x}\right)\mathrm{=}\left(\begin{array}{c}\mathrm{x}\\ \mathrm{f}\left(\mathrm{x}\right)\\ \mathrm{o}\end{array}\right)$

(current point of curve 5). K is an arbitrary constant. $$\mathrm{P}\mathrm{=}\mathrm{M}\mathrm{+}\mathrm{\lambda }\overrightarrow{\mathrm{v}}\mathrm{or}\overrightarrow{\mathrm{v}}\mathrm{=}\mathrm{cos\; \phi }\overrightarrow{{\mathrm{not}}_{\mathrm{m}}}\mathrm{+}\mathrm{sin\; \phi }\overrightarrow{\mathrm{z}}$$

From the optical equation we draw: $$\begin{array}{ll}\mathrm{OP}\mathrm{=}\mathrm{K}\mathrm{-}\mathrm{<figure-callout\; id="2"\; label="MP\; \Rightarrow \; OP"\; filenames="imgf0001.png"\; state="\{\{state\}\}">MP\; </figure-callout>}& \mathrm{\Rightarrow }{\mathrm{OP}}^{}{}^{\mathrm{2}}\mathrm{=}{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="imgf0001.png"\; state="\{\{state\}\}">K</figure-callout>}}^{\mathrm{2}}\mathrm{+}{\mathrm{MP}}^{\mathrm{2}}\mathrm{-}\mathrm{2}\mathrm{<figure-callout\; id="2"\; label="KMP\; \Rightarrow \; OM"\; filenames="imgf0001.png"\; state="\{\{state\}\}">KMP\; </figure-callout>}& \\ & \mathrm{\Rightarrow }{\mathrm{OM}}^{}{}^{\mathrm{2}}\mathrm{+}{\mathrm{<figure-callout\; id="2"\; label="\lambda "\; filenames="imgf0001.png"\; state="\{\{state\}\}">\lambda </figure-callout>}}^{\mathrm{2}}\mathrm{+}\mathrm{2}\mathrm{\lambda }\overrightarrow{\mathrm{OM}}\mathrm{\cdot }\overrightarrow{\mathrm{v}}\mathrm{=}{\mathrm{<figure-callout\; id="2"\; label="K"\; filenames="imgf0001.png"\; state="\{\{state\}\}">K</figure-callout>}}^{\mathrm{2}}\mathrm{+}{\mathrm{\lambda }}^{\mathrm{2}}\mathrm{-}\mathrm{2}\mathrm{KMP}\\ & \mathrm{\iff }\mathrm{2}\mathrm{\lambda }\left(\overrightarrow{\mathrm{OM}}\mathrm{.}\overrightarrow{\mathrm{v}}\mathrm{+}\mathrm{K}\right)\mathrm{=}{\mathrm{K}}^{\mathrm{2}}\mathrm{-}{\mathrm{<figure-callout\; id="2"\; label="OM"\; filenames="imgf0001.png"\; state="\{\{state\}\}">OM</figure-callout>}}^{\mathrm{2}}\end{array}$$

When K ² = OM ² we reach a limit point for the calculation of the reflector.

Calculation example for lens 3

Let I ( Fig.3 ) a current point of altitude h of the input diopter 3Eme, radius of curvature Ri. Let Q be the distance from point M of curve 5 to the point of the input diopter situated in the horizontal plane of curve 5.

$$\mathrm{tg\; \alpha }\mathrm{=}\frac{\mathrm{h}}{}\begin{array}{cc}\mathrm{\}}& {\mathrm{z}}_{\mathrm{i}}\\ \mathrm{\}}& \end{array}$$

$$\mathrm{Q}\mathrm{+}{\mathrm{R}}_{\mathrm{i}}\mathrm{-}{\mathrm{R}}_{\mathrm{i}}\mathrm{cos\; \beta }{\mathrm{y}}_{\mathrm{i}}$$

avec n_L = indice de réfraction du matériau de la lentille 3
angle d'incidence: α + β angle de réfraction: p $${\mathrm{n}}_{\mathrm{L}}\mathrm{sin\; \rho }\mathrm{=}\sin \left(\mathrm{\alpha }\mathrm{+}\mathrm{\beta }\right)$$

$$\mathrm{y}\mathrm{=}\mathrm{\rho }\mathrm{-}\mathrm{\beta }$$

The angle α designates the angle between MI and the horizontal. Ω designates the center of the arc forming the input diopter 3Eme, Ω being located in the plane of the folder. The angle between ΩI and the horizontal is designated β. $$\mathrm{sin\; \beta }\mathrm{=}\frac{\mathrm{h}}{\mathrm{Ri}}$$

$$\mathrm{tg\; \alpha }\mathrm{=}\frac{\mathrm{h}}{}\begin{array}{cc}\mathrm{\}}& {\mathrm{z}}_{\mathrm{i}}\\ \mathrm{\}}& \end{array}$$

$$\mathrm{Q}\mathrm{+}{\mathrm{R}}_{\mathrm{i}}\mathrm{-}{\mathrm{R}}_{\mathrm{i}}\mathrm{cos\; \beta }{\mathrm{there}}_{\mathrm{i}}$$

with n _L = refractive index of lens material 3
angle of incidence: α + β refraction angle: p $${\mathrm{not}}_{\mathrm{The}}\mathrm{sin\; \rho }\mathrm{=}\sin \left(\mathrm{\alpha }\mathrm{+}\mathrm{\beta }\right)$$

$$\mathrm{there}\mathrm{=}\mathrm{\rho }\mathrm{-}\mathrm{\beta }$$

By designating by μ the distance, in the lens 3, between the input point I of a beam and the output point W on the output diopter 3Ems, the W point coordinates are obtained. $$W\left[\begin{array}{c}{\mathrm{there}}_i+\mu \cos \gamma \\ {\mathrm{there}}_i+\mathrm{\mu sin\gamma }\end{array}\right]=\left[\begin{array}{c}{\mathrm{there}}_W\\ z_W\end{array}\right]$$

d'où on tire µ (h), et donc y_i(h) et W(h)
Surfaces conjuguées
Deux points fonction de x et de h $$\mathrm{Entrée}\mathrm{:}\mathrm{M}\mathrm{-}{\mathrm{y}}_{\mathrm{i}}\overrightarrow{{\mathrm{n}}_{\mathrm{w}}}\mathrm{+}\mathrm{h}\overrightarrow{\mathrm{z}}$$

$$\mathrm{Sortie}\mathrm{:}\mathrm{M}\mathrm{-}{\mathrm{y}}_{\mathrm{w}}\overrightarrow{{\mathrm{n}}_{\mathrm{w}}}\mathrm{+}{\mathrm{z}}_{\mathrm{w}}\overrightarrow{\mathrm{z}}$$

Let e _{L be} the thickness of the lens 3 at the center, we put: yo = Q + e _L and K1 = Q + n _L e _L $$\begin{array}{cc}\mathrm{Optical\; path}& =\frac{\mathrm{h}}{\mathrm{sin\; \alpha }}\mathrm{+}{\mathrm{not}}_{\mathrm{The}}\mathrm{\mu }\mathrm{+}{\mathrm{there}}_{\mathrm{0}}-{\mathrm{there}}_{\mathrm{w}}\hfill \\ & \mathrm{=}\frac{\mathrm{h}}{\mathrm{sin\; \alpha }}\mathrm{+}\left({\mathrm{there}}_{\mathrm{0}}\mathrm{-}{\mathrm{there}}_{\mathrm{i}}\right)+\mathrm{\mu }\left({\mathrm{not}}_{\mathrm{The}}\mathrm{-}\mathrm{cos\; \gamma }\right)\mathrm{=}\mathrm{K}\mathrm{1}\hfill \end{array}$$

from which we draw μ (h), and hence y _i (h) and W (h)
Conjugated surfaces
Two points depending on x and h $$\mathrm{Entrance}\mathrm{:}\mathrm{M}\mathrm{-}{\mathrm{there}}_{\mathrm{i}}\overrightarrow{{\mathrm{not}}_{\mathrm{w}}}\mathrm{+}\mathrm{h}\overrightarrow{\mathrm{z}}$$

$$\mathrm{Exit}\mathrm{:}\mathrm{M}\mathrm{-}{\mathrm{there}}_{\mathrm{w}}\overrightarrow{{\mathrm{not}}_{\mathrm{w}}}\mathrm{+}{\mathrm{z}}_{\mathrm{w}}\overrightarrow{\mathrm{z}}$$

• selon la courbe C2, pour x ≥ x₀ et pour x ≤ x₁, où x_o ≥ 0, et x₁ ≤ 0, les plans normaux à la courbe 5 en x_o et x₁ font un angle supérieur à 5°, de préférence supérieur ou égal à 10°, par rapport à l'axe optique. Pour x appartenant au segment [x_1- x_o], ή(x) est nul.
• Par comparaison, la première variante de l'invention, avec le faisceau lumineux selon la figure 6, correspond sur cette figure 7 à la courbe C1, courbe où ή(x) est constamment nul.

According to another variant of the invention, it is sought to make a light beam with a "downward" cut in its most lateral zones, as shown in FIG. figure 7 . As explained in figure 9 , which represents the evolution of the value of ή (x) as a function of x, we see that we use a function ή (x) increasing or constant as a function of | x | (absolute value of x):

• according to the curve C2, for x ≥ x ₀ and for x ≤ x ₁ , where x _o ≥ 0, and x ₁ ≤ 0, the planes normal to the curve 5 in x _o and x ₁ form an angle greater than 5 °, preferably greater than or equal to 10 °, with respect to the optical axis. For x belonging to the segment [x _1- x _o ], ή (x) is zero.
• By comparison, the first variant of the invention, with the light beam according to the figure 6 , fits on this figure 7 at the curve C1, curve where ή (x) is constantly zero.

The figure 10 , which represents the curve 5 in plan view, represents the trace of the plane normal to the points M of coordinates x ₁ and x _o

If ή (x) remains low (in particular less than 3.5 °), the beam is improved without compromising compliance with the standards, in particular those concerning fog lamps. The term "improved" beam is understood here to mean that it is possible to increase the amount of light close to the vehicle at high lateral angles, a light that is more useful to the driver than distant light.

What distinguishes this variant of the preceding variant relates to the construction of the lens: in this variant, the lens 3 'can be determined as follows: The section, or intersection 3'Em of the lens 3' with the plane Em defined below. above, corresponds to the section of a stigmatic lens between the point M of the edge 5 of the folder and the infinite, this plane containing the axis of the stigmatic lens, axis inclined by an angle ή, continuous function of x, relative to the projection of the optical axis of the module in the plane considered. Here, the output diopter 3Ems' is calculated so that the light ray u1 'coming out of the lens 3' and coming from an incident ray q1 coming from the point M makes an angle ή (x) with the horizontal plane of the folder 5.

The calculation example for the lens 3 'has the following modifications with respect to the example according to the first variant detailed above: as for the previous example, the point I is a current point which is in a plane perpendicular to the curve 5 passing through any point M 'thereof of lateral coordinate x.

The optical path is modified as follows: $$\begin{array}{l}\mathrm{Optical\; path}\mathrm{=}\frac{\mathrm{h}}{\mathrm{sin\; \alpha }}\mathrm{+}{\mathrm{not}}_{\mathrm{The}}\mathrm{\mu }\mathrm{+}{\mathrm{<figure-callout\; id="1"\; label="\mu "\; filenames="imgf0002.png"\; state="\{\{state\}\}">\mu </figure-callout>}}_{\mathrm{1}}\\ \mathrm{=}\frac{\mathrm{h}}{\mathrm{sin\; \alpha }}\mathrm{+}\left({\mathrm{there}}_{\mathrm{0}}\mathrm{-}{\mathrm{there}}_{\mathrm{i}}\right)\cos \stackrel{\mathrm{\text{'}}}{\mathrm{\eta }}\mathrm{+}\mathrm{h\; sin}\stackrel{\mathrm{\text{'}}}{\mathrm{\eta }}\mathrm{+}\mathrm{\mu }\left({\mathrm{not}}_{\mathrm{The}}\mathrm{-}\mathrm{cos\; y\; cos}\stackrel{\mathrm{\text{'}}}{\mathrm{\eta }}\mathrm{+}\mathrm{sin\; y\; sin}\stackrel{\mathrm{\text{'}}}{\mathrm{\eta }}\right)\mathrm{=}\mathrm{K}\mathrm{1}\end{array}$$

The inclined plane of an angle ή (x) with respect to the vertical and perpendicular to the plane of the construction whose trace is the line π constitutes an exit wave surface by the section of the lens considered. If we put ή (x) = 0, we find the example according to the previous variant.

In summary, for this second variant, the lighting module is such that, for any plane perpendicular to the edge of the folder 5 at a point M, the intersection of the lens 3 with said plane is the section of a stigmatic lens between point M and infinity, the direction of emergent rays making an angle ή with the plane of the folder, continuous function angle of the lateral coordinate (x) of said point M.

Preferably, the function ή (x) is constant or increasing as a function of the lateral coordinate (x) of the point M.

And, in particular, the function ή (x) is constant and zero between the lateral coordinates of the points of the edges of the folder located on either side of a vertical plane containing the optical axis (Y) of the module, with preferably the angle of the normal planes at the edge of the folder passing through these points with said axis (Y) is greater than or equal to 5 °, in particular greater than or equal to 10 °.

Claims (16)

Lighting module for a motor vehicle headlamp, giving a cut-off light beam, comprising a concave reflector (2), at least one light source (S) disposed in the concavity of the reflector for illuminating, in particular at least upwards, and a lens (3) located in front of the reflector and the light source, the reflector being associated with a folder (4), in particular horizontal, whose upper surface is reflective for folding the beam coming from the reflector, said folder having an edge ( 5) of the front end to form the cut-off in the lighting beam,
characterized in that the front edge (5) of the folder is formed by a plane curve with variable curvature, the curvature at a point (M) being a continuous function of the lateral coordinate (x) of this point, the reflector (2) is determined to transform the wave surface coming from the source into a wave surface that is reduced to the curve with variable curvature of the edge (5) of the folder, - And the lens (3) is determined to give a point (M) of the edge (5) of the folder, especially for all the rays contained in the plane perpendicular to the front edge of said folder at the point considered, an image to infinity. Lighting module according to the preceding claim, characterized in that the lens (3) is determined to give a point (M) of the edge (5) of the folder an image at infinity in a direction inclined with respect to the plane of the bending machine of an angle continuous function of the distance from this point to the optical axis. Lighting module according to claim 1, characterized in that the curvature of the front edge (5) of the folder has at least a maximum (5b1, 5b2) located angularly between the optical axis (Y) of the module and an angular limit beam. Lighting module according to one of the preceding claims, characterized in that the curvature of the front edge (5) of the folder has a secondary maximum located on or substantially on the optical axis. Lighting module according to claim 3 or 4, characterized in that the curvature of the front edge (5) of the folder has a maximum (5b1, 5b2) on each side of the optical axis. Lighting module according to the preceding claim, characterized in that the front edge (5) of the folder is symmetrical with respect to the optical axis. Lighting module according to any one of the preceding claims, characterized in that the maximum curvature (5b1, 5b2) of the front edge of the folder is chosen so that the illumination of the extreme angular zones of the beam is reinforced, without decreasing illumination of the central area. Lighting module according to any one of the preceding claims, characterized in that the extreme angular zones of the beam extend in directions greater than or equal to ± 35 ° on either side of the optical axis. Lighting module according to one of the preceding claims, characterized in that, for any plane perpendicular to the edge of the folder 5 at a point M, the intersection of the lens (3) with said plane is the section of a stigmatic lens between the point M and the infinite, the direction of emerging rays making an angle ή with the plane of the folder, angle continuous function of the lateral coordinate (x) of said point M. Lighting module according to one of the preceding claims, characterized in that the function ή (x) is constant or increasing as a function of the absolute value of the lateral coordinate (x) of the point M. Lighting module according to one of the preceding claims, characterized in that the function ή (x) is constant and zero between the lateral coordinates of the points of the edges of the folder located on either side of a vertical plane containing the optical axis (Y) of the module, preferably with the angle of the normal planes to the edge of the folder passing through these points with said axis (Y) is greater than or equal to 5 °, in particular greater than or equal to 10 °. Lighting module according to any one of the preceding claims, characterized in that the surface of the reflector (2) is such that light rays (i, i1) originating from the source and falling at points (P, P1) situated on the intersection (2m) of this surface and a vertical plane (Em) passing through the center of curvature, but separated from the source, are reflected in this vertical plane so as to converge at a point (M) located at the intersection of the vertical plane and the edge of the folder. Lighting module according to any one of the preceding claims, characterized in that the illumination in the central zone between -10 ° and + 10 ° on either side of the optical axis is maintained relative to a basic module whose folder would have a circular front edge of radius equal to the average radius of curvature of the front edge (5), while the areas located at -35 ° and + 35 ° on either side of the axis optical, and corresponding to the lines listed 9-1 and 9-2 according to the R19-3 standard, have a higher illumination than that obtained with said basic module. Lighting module according to any one of the preceding claims, characterized in that the cut-off beam obtained is flat-cut, in particular being selected between an anti-fog beam and a flat-cut code beam portion. Lighting module for a motor vehicle headlamp, giving a cut-off light beam, comprising a concave reflector (2), at least one light source (S) arranged in particular in the concavity of the reflector to illuminate, in particular at least upwards, and a lens (3) located in front of the reflector and the light source, the reflector being associated with a folder (4), in particular horizontal, the upper surface of which is reflective for folding the beam coming from the reflector, said folder having an edge (5) front end clean to form the cut in the lighting beam,
characterized in that the front edge (5) of the folder is formed by a plane curve, in particular in a horizontal plane, with a variable curvature, the curvature at a point (M) being a continuous function of the lateral coordinate (x) of this point, the reflector (2) has a shape chosen so that a ray coming from the center of the light source and reflected by the reflector intersects the front edge of the folder being contained in a plane normal to this edge passing through this intersection, - And the lens (3) is arranged to give a point (M) of the edge (5) of the folder an image to infinity in the plane perpendicular to the front edge of the folder at the point of intersection. Motor vehicle headlamp, characterized in that it comprises at least one module according to any one of the preceding claims.

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