EP2019256A1 - Lighting module for vehicle headlight - Google Patents

Abstract

The module (Ma) has a light source (S) placed at a focus on optical axis, and a cylindrical lens (La) i.e. diverging lens, placed between two planes passing via focuses of an arc of ellipse. The source is constituted by an LED (3a) that is arranged such that light beam emitted from the LED has an average direction sensibly orthogonal to a geometric axis of a complex surface type reflector (Ra). The reflector is situated on an emitted beam side relative to a plane of a rear surface (4a) of the LED, where a surface of the reflector is calculated based on protection optics of the LED.

Description

The invention relates to a lighting module, for a motor vehicle light projector, to give a cut-off beam, in particular a code beam.

• au moins une source lumineuse,
• un réflecteur du type à surface complexe, la source lumineuse étant disposée à un foyer situé sur l'axe optique ou à son voisinage, le réflecteur produisant vers l'avant un faisceau à coupure, et
• une lentille cylindrique à génératrices verticales placée entre les deux foyers de l'arc d'ellipse.

It is known, for example from the patent EP-A-1,491,816 , a module admitting an optical axis and comprising:

• at least one light source,
• a reflector of the complex surface type, the light source being disposed at or near a focal point on the optical axis, the reflector producing a cut-off beam towards the front, and
• a cylindrical lens with vertical generators placed between the two foci of the elliptical arc.

The patent EP-A-1,491,816 combines such a module with additional reflectors. Such a device is relatively bulky in the vertical direction so that to achieve a progressive illumination of turn lighting (PBL) it is hardly possible to perform a vertical stack of modules, and they must be juxtaposed horizontally, which leads to large sets.

The object of the invention is, above all, to provide a lighting module of relatively small size in the vertical direction, in particular to allow stacking of several modules in height.

The invention also aims to provide a high efficiency lighting module, whose power consumption is reduced for the same luminous flux. It is further desirable that the beam produced by the module is well spread to meet the requirements of the specifications.

• au moins une source lumineuse,
• un réflecteur du type à surface complexe, la source lumineuse étant disposée à un foyer situé sur l'axe optique ou à son voisinage, et la section du réflecteur par un plan horizontal étant sensiblement en arc d'ellipse admettant un premier foyer confondu avec le, ou voisin du, foyer où se trouve la source lumineuse, et un deuxième foyer situé en avant sur l'axe optique du module, le réflecteur produisant vers l'avant un faisceau à coupure, et
• une lentille cylindrique à génératrices sensiblement verticales placée entre les deux foyers (F1, F2) de l'arc d'ellipse, et tel que
• la source lumineuse comprend ou est constituée par au moins une diode électroluminescente disposée de manière que son faisceau lumineux ait une direction moyenne sensiblement orthogonale à l'axe géométrique du réflecteur,
• le réflecteur est situé, relativement au plan de la face arrière de la diode électroluminescente, du côté faisceau émis, et sa surface est calculée en tenant compte de l'optique de protection de la diode électroluminescente.

According to the invention, a lighting module is defined as follows: It is a lighting module, for a motor vehicle headlamp, to give a cut-off beam, in particular a code beam, this module admitting an optical axis , and comprising:

• at least one light source,
• a reflector of the complex surface type, the light source being disposed at a focus located on the optical axis or in its vicinity, and the section of the reflector by a horizontal plane being substantially in an elliptical arc admitting a first focus coinciding with the , or near the focus where the light source is located, and a second focus located forward on the optical axis of the module, the reflector producing a forward beam cutoff, and
• a cylindrical lens with substantially vertical generatrices placed between the two foci (F1, F2) of the elliptical arc, and such that
• the light source comprises or consists of at least one light-emitting diode arranged in such a way that its light beam has a mean direction substantially orthogonal to the geometric axis of the reflector,
• the reflector is located, relative to the plane of the rear face of the light emitting diode, the transmitted beam side, and its surface is calculated taking into account the protective optics of the light emitting diode.

It is understood that the surface of the reflector is calculated so that the deviations (spherical caps of the protective dome LEDs) or offsets (flat blades of the LEDs protected by the blade) due to the protection of the rays from the light source chosen are taken into account appropriately.

Advantageously, the horizontal plane mentioned above is merged or very close to the output face of the emitter of the diode.

Advantageously, the lens is generally divergent type, although one or more areas of the lens may not be divergent.

The term "complex surface" is understood to mean a surface defined so as to create a cut by alignment of images, in the absence of a cover or a cup.

Preferably, the light-emitting diode comprises a radiator located on the opposite side to the reflector.

The assembly makes it possible to obtain a wide outgoing beam, with a clean cut-off line, with a high efficiency and a reduced consumption.

The light-emitting diode may be arranged with its rear face in a horizontal plane so as to emit a light beam downwards in a substantially vertical mean direction, the radiator of the light-emitting diode being preferably situated above it, while that the reflector is located below the horizontal plane of the rear face of the diode.

Alternatively, the light-emitting diode may be disposed with its rear face in a horizontal plane so as to emit a light beam upwards in a substantially vertical mean direction, the radiator of the light-emitting diode being preferably located below it. , while the reflector is located above the horizontal plane of the rear face of the diode.

Advantageously, the light-emitting diode is disposed with its rear face in a substantially vertical plane so as to emit a light beam having a substantially horizontal mean direction, the radiator of the light-emitting diode being preferably located behind it, while the reflector is located in front of the light-emitting diode facing down, and a reflecting mirror is disposed below the reflector to return the beam to the lens.

Alternatively, the light-emitting diode is disposed with its rear face in a substantially vertical plane so as to emit a light beam having a substantially horizontal mean direction, the radiator of the light-emitting diode being preferably located behind it, while the reflector is located in front of the light-emitting diode facing upwards, and a reflecting mirror is disposed above the reflector to send the beam back to the lens.

The reflecting mirror may be plane, and preferably inclined at about 45 ° in the horizontal plane. This angle can be modified in case the plane of the diodes is not rigorously vertical.

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

The light projector may comprise several modules with light emitting diode disposed with its rear face in a horizontal plane, the modules being juxtaposed with the rear faces of the light emitting diodes located in the same horizontal plane.

The luminous projector may comprise several modules where the modules are juxtaposed or stacked with the rear faces of the light emitting diodes located in the same plane.

Preferably, the light projector comprises a plurality of modules with a light-emitting diode arranged with its rear face in a vertical plane, and the modules are stacked so that the rear faces of the light-emitting diodes are located in the same vertical plane and on the same plate. printed circuit board.

The modules, according to one embodiment, can be stacked and have angularly offset beams, in horizontal projection, from bottom to top, and be turned on successively according to the turning of the wheels of the vehicle to obtain a progressive turn lighting (PBL for Progressive Bending Light ").

The projector can have three (or four) stacked modules and beams angularly offset.

Advantageously, the reflecting mirror is disposed above or below the reflector of the lower module and preferably forms with it a single piece.

• Fig. 1 est une coupe verticale schématique d'un module d'éclairage selon l'invention.
• Fig. 2 est une coupe horizontale schématique suivant la ligne II-II de Fig. 1.
• Fig. 3 est une vue schématique en coupe verticale d'un module à plusieurs diodes électroluminescentes selon l'invention.
• Fig. 4 est une vue en perspective de l'arrière, à plus petite échelle, d'un module selon Fig. 3, la plaque arrière de circuit imprimé étant retirée.
• Fig. 5 est une vue en perspective, de face, schématique du module de Fig. 4.
• Fig.6 est une coupe schématique verticale d'une diode électroluminescente encapsulée dans une plaque protectrice de matière transparente, illustrant le calcul du réflecteur, et
• Fig.7 est une coupe schématique verticale semblable à Fig.6 d'une diode électroluminescente séparée par une couche d'air de la plaque protectrice transparente, pour le calcul du réflecteur.

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 a schematic vertical section of a lighting module according to the invention.
• Fig. 2 is a schematic horizontal section along line II-II of Fig. 1 .
• Fig. 3 is a schematic vertical sectional view of a module with several light-emitting diodes according to the invention.
• Fig. 4 is a perspective view of the rear, on a smaller scale, of a module according to Fig. 3 , the printed circuit board being removed.
• Fig. 5 is a perspective, front view, schematic of the module of Fig. 4 .
• Fig.6 is a vertical schematic section of a light-emitting diode encapsulated in a transparent material protective plate, illustrating the calculation of the reflector, and
• Fig.7 is a vertical schematic section similar to Fig.6 of a light-emitting diode separated by an air layer of the transparent protective plate, for the calculation of the reflector.

Referring to Fig. 1 and 2 drawings, one can see a lighting module M for motor vehicle light projector, provided to give a cut-off beam, including a beam code. This module has a horizontal optical axis XX and comprises at least one light source S, and a reflector R with a surface of complex type. The geometric axis of the reflector R coincides with the optical axis XX.

Sections such as 1 of the reflector R by vertical planes parallel to the optical axis XX are substantially in parabolic arcs, turning their concavity forward, that is to say to the right according to Fig. 1 . These sections have a focus located in the horizontal plane passing through the optical axis XX of the module. The arc 1 corresponds to the section of the reflector R by a vertical plane passing through the optical axis XX, and has a focus F located on this axis.

The light source S is disposed at the focus F or in its vicinity. The section of the reflector R by a horizontal plane passing through the optical axis is substantially in an elliptical arc 2 ( Fig. 2 ) admitting a first focus F1 coincides with the focus F or neighboring this focus, and a second focus F2 located forward on the optical axis of the module.

The reflector R of the complex surface type produces a cut beam to the front. The cutoff may correspond to a flat line, in particular horizontal for an anti-fog function. It may also correspond to a flat but oblique line, in particular to participate in the formation of the oblique part of a cross-type beam (which, according to European regulations, presents a cut in the form of a broken line comprising a horizontal plane segment and an oblique plane segment at 15 °).

A cylindrical lens L with vertical generatrices is placed between two planes passing through the foci F1 and F2 of the ellipse arc 2 and orthogonal to the optical axis. The lens has a general shape of a diverging lens, of which at least one zone may not be divergent.

According to the invention, the light source S is constituted by at least one light-emitting diode 3, abbreviated as LED. Preferably, the emitter of the LED 3 is of the rectangular or square plane type, with 1 to 5 mm of side. The focal length of the reflector R is of the order of 5 mm for such emitters. The LED 3 is arranged so as to illuminate downwards with the mean direction Δ of its light beam substantially vertical and orthogonal to the geometric axis of the reflector R. This reflector R is located, relative to the plane of the rear face 4 of the LED, entirely on the side of the beam emitted by the LED 3. The surface of the reflector R is calculated taking into account the optical protection of the LED 3.

according to Fig.1 and 2 , the leading edge of the LED 3 is located at the focus F and the LED extends rearward from the focus F. The collector reflector R is such that at each point of this reflector light rays such as i1 from the front edge of the LED 3 are reflected horizontally along a radius such as r1, or so as to define an oblique planar cut line up to 15 ° on the horizontal. The rays such as i2 emitted by LED 3 points located behind the front edge are reflected in rays such as r2 falling below the horizontal. With this arrangement, the illuminated area is therefore below a horizontal cut or an inclined cut rising on the horizontal.

If it is desired to obtain a beam whose illuminated portion is located above the cutoff line with a dark portion below this line, the LED 3 is then placed so that its trailing edge passes through the focus. F and LED 3 is located in front of this fireplace.

A radiator 5 for evacuating the heat released by the LED 3 is disposed against the rear face of this LED, on the opposite side to the reflector R.

The entire module is arranged in a box closed at the front by a transparent glass G.

According to the realization of Fig. 1 and 2 , the LED 3 is arranged so that the plane of its rear face 4 is horizontal, the radiator 5 is oriented upwards. The reflector R is located below the horizontal plane of the rear face 4.

The cylindrical lens L, substantially divergent, can be placed anywhere between the collector reflector R and the focus F2, and adjusts the horizontal distribution of light in the beam.

In the low-cut embodiment variant of Fig. 3-5 to improve the efficiency, the lens La, before folding the beam must exceed the reflector up, while in the case of Fig. 1 and 2 the lens L must extend beyond the reflector downwards because the beam diverges all the more as it is further away from the reflector. On the other hand, the closer the lens L, La is to F2, the more potentially it is narrow (the width corresponds to the dimension in a direction perpendicular to the plane of Fig. 1 ) since the beam in top view converges to F2; however, this effect is partially or totally canceled depending on the source chosen and its orientation due to the divergence due to the size of the source. However, it is desirable to keep the lens close to the reflector R to better control the horizontal distribution control.

The module M of Fig. 1 and 2 offers a high yield. It makes it possible to obtain a satisfactory luminous flux for a reduced electrical energy consumption, but does not lend itself well to vertical stacking, on the one hand because of the arrangement of the radiator 5 and on the other hand because the LEDs will not be located in the same plane, which prevents them from being placed on a single circuit board and complicates the electrical connections. However, modules can be juxtaposed horizontally, with the rear faces of the LEDs in the same horizontal plane, for mounting on a single horizontal printed circuit board.

Advantageously, to allow easy vertical stacking, as illustrated on Fig. 3 , a module Ma according to the invention comprises at least one LED 3a whose rear face 4a is located in a vertical plane 6 so as to emit forward a light beam having a substantially horizontal mean direction Δa. The radiator 5a of the LED is located behind it while the reflector Ra is located in front of the LED with its concavity facing down. Geometric axis (not drawn on Fig.3 ) of the reflector Ra is vertical. The mean direction Δa of the beam of the LED is horizontal, and therefore orthogonal to the geometric axis of the reflector Ra. A reflecting mirror 7 plane is disposed below the reflector Ra to return the beam to the lens La with vertical generators. The mirror 7 is inclined, preferably at 45 °, on the horizontal plane.

As shown on Fig. 3 it is then possible to vertically stack several modules, for example three similar modules Ma, Ma1, Ma2 whose rear faces 4a, 4a1, 4a2 LEDs 3a, 3a1, 3a2 are located in the same vertical plane 6 and can be fixed and connected on the same vertical printed circuit board 8. Radiators 5a, 5a1, 5a2 are disposed behind each respective LED; alternatively the radiators could be grouped into a single common radiator.

Due to the reversal of the beam created by the reflecting mirror 7, the LED 3a is arranged such that its upper edge is substantially at the focal point Fa of the reflector Ra. The light rays such as i3 from areas of the LED 3a located lower than the focus are reflected downwardly by Ra away outwardly, and then reflected by the mirror 7 along radii such as r3 following a downward direction. The lens La is common to the three modules and has a height sufficient for this purpose.

To achieve a PBL (Progressive Bending Lignt) function, for example disclosed in the patent EP-A-1,500,553 angularly shifts the average direction of the beams of the superimposed modules Ma, Ma1, Ma2 about a vertical axis so that, by successively switching on the modules, for example from bottom to top, the light beam turns inwards. of the turn.

Advantageously, the reflecting plane mirror 7 of a module is fixed to the back of the reflector Ra1, Ra2 of the module located below and forms a single piece with this reflector. The input face 9 of the lens La may have recesses at the transition zones between the different modules while the exit face 10 of this lens is smooth, without recess.

• La lentille ne présente pas de puissance verticale, puisque la lentille est cylindrique d'axe vertical pour chaque module, ce qui impose que la coupure du faisceau soit entièrement réalisée en amont de la lentille. Ceci est bien le cas puisque la coupure est réalisée à l'aide du réflecteur R, Ra, Ra1, Ra2. Cela permet d'éviter des lignes brillantes et un aspect discontinu de la lentille.
• Le module ou le projecteur présente une bonne efficacité, similaire à celle de modules à plieuse ; la lumière proche et donc le flux sont importants pour une fonction PBL.
• Les LEDs, selon la variante des Fig. 3-5, sont situées sur un même plan vertical et adossées à leur radiateur ce qui simplifie le processus de fabrication et diminue le coût.

In a module, or in a projector composed of a stack of modules, according to the invention:

• The lens has no vertical power, since the lens is cylindrical vertical axis for each module, which requires that the cutting of the beam is made entirely upstream of the lens. This is indeed the case since the cut is made using the reflector R, Ra, Ra1, Ra2. This avoids shiny lines and a discontinuous appearance of the lens.
• The module or projector has good efficiency, similar to that of folding modules; the near light and therefore the flux are important for a PBL function.
• LEDs, according to the variant of the Fig. 3-5 , are located on the same vertical plane and backed by their radiator which simplifies the manufacturing process and reduces the cost.

It will be noted that, given the position of the reflectors in the folded version of Fig. 3-5 involving a mirror plane of return, the corresponding modules Ma, Ma1, Ma2 must give, before folding by the plane mirror, a lower cut, all the light must be above a horizontal line, in the frame of the figures preceding. If for implantation reasons it is decided to make the part with all the reflectors below the bottom of the lens exceed rather than above its upper end, it is then necessary for the unfolded elementary system to provide, in the reference used, a code-type break, with all the light below the horizontal break. In this case, the LEDs are located above the collecting mirrors R, which are themselves below the reflecting mirrors 7: an "upside down" configuration is obtained with respect to that represented in the figures.

The reflectors R, Ra, Ra1, Ra2 of "complex surface" type are adapted to the LEDs 3. Indeed, given the target focal lengths (of the order of 5 mm for light emitters of 1 to 5 mm side) , you have to take into account the protection optics of the LEDs.

Calculation of reflector surfaces

^1st case : The cutting of the LED (transmitter + "optical" protection) by a vertical plane passing through the focus is independent of the cutting plane considered, except for the length behind the focus of the segment representing the section of the transmitter , or for the length in front of the home if one seeks to obtain a code-like break rather than a high break.

This case corresponds to a protective optics of the blade type or plate with parallel faces.

Under these conditions, if we consider a line tangent, at a current point P, to a given plane parameter curve (straight line and curve contained in a horizontal plane) and if we consider a plane perpendicular to this line and passing through the focus F ( which is a well chosen point of the transmitter), one can validly make a 2D optical construction in this perpendicular plane for a hypothetical reflective surface, cylindrical, having for cross-section the result of this construction and for direction the straight line of which it is question above, which is then one of the generatrices of the cylinder. In fact, all the rays emitted from the focus in the plane of construction remain contained there (result of the property on the cuts stated above) and the construction is valid, in projection according to the direction of the cylinder, in all points of this one. .

• 1a/ celles dont l'émetteur est encapsulé dans une couche protectrice de matière transparente, notamment une résine, de face de sortie plane (Fig.6) et
• 1b/ celles dont l'émetteur est simplement protégé par une lame transparente, notamment lame de verre, plane avec une couche d'air entre l'émetteur et la lame (Fig.7).

This 1 ^st case corresponds to two known families of LEDs:

• 1a / those whose emitter is encapsulated in a protective layer of transparent material, in particular a resin, with a plane exit face ( Fig.6 ) and
• 1b / those whose emitter is simply protected by a transparent blade, especially a glass slide, flat with a layer of air between the emitter and the blade ( Fig.7 ).

A method for calculating the cross-sections for the two families of LEDs above (1a, 1b) is given below for a direction parallel to x (axis of the marker, itself parallel to one of the sides of the emitter ), in the case of a low cut, dead zone at the top after folding and assembly. Note that in this case, the "focus" is the most forward corner of the transmitter along the optical axis and the opposite side x to the part of the reflector being built - the other side can be constructed by symmetry, but not necessarily with the same parameter, that is to say here the same section by z = 0). The exposed calculation method is an elementary numerical solution of the underlying equation, which is a differential equation.

• h_s = dimension de l'émetteur suivant la direction y
• δ = épaisseur de la couche transparente au-dessus de l'émetteur
• δ1 = l'épaisseur d'air entre l'émetteur et la lame protectrice (comme représenté à la figure 7)
• e = angle d'un rayon issu du foyer avec la surface de sortie de la couche
• y_e = coordonnée suivant y du point de sortie du rayon
• r = angle du rayon réfracté dans l'air avec surface de sortie de la couche
• M₀ = point connu de la surface du réflecteur
• Vecteur $\overrightarrow{{\mathrm{n}}_0}$
  
  = normale en M₀ à la surface du réflecteur
• M = point à déterminer de la surface du réflecteur, voisin de M₀
• Vecteur n = normale en M à la surface du réflecteur
• n = indice de réfraction de la couche
• λ = longueur du segment entre M et le point de sortie du rayon
• Le vecteur n est orienté selon la bissectrice de l'angle entre le rayon incident et l'horizontale.

Referring to Fig. 6 we see that :

• h _s = dimension of the transmitter in the y direction
• δ = thickness of the transparent layer above the transmitter
• δ1 = the air thickness between the transmitter and the protective blade (as shown in figure 7 )
• e = angle of a ray from the focus with the exit surface of the layer
• y _e = coordinate following y of the ray exit point
• r = angle of the refracted ray in the air with exit surface of the layer
• M ₀ = known point of reflector surface
• Vector $\overrightarrow{{\mathrm{not}}_0}$
  
  = normal in M ₀ on the surface of the reflector
• M = point to be determined from the reflector surface, close to M ₀
• Vector not = normal in M on the reflector surface
• n = refractive index of the layer
• λ = length of the segment between M and the exit point of the radius
• The vector not is oriented along the bisector of the angle between the incident ray and the horizontal.

• 1a - Cas d'une LED encapsulée (schéma de Fig.6), noyée dans une plaque 11 ou couche transparente de protection : $${\mathrm{y}}_{\mathrm{e}}\mathrm{=}\frac{\mathrm{hs}}{\mathrm{2}}\mathrm{-}\frac{\mathrm{\delta }}{\mathrm{tg\; e}}$$
  
  $$\mathrm{n}\sin \left(\frac{\mathrm{\pi }}{\mathrm{2}}\mathrm{-}\mathrm{e}\right)\mathrm{=}\sin \left(\frac{\mathrm{\pi }}{\mathrm{2}}\mathrm{-}\mathrm{r}\right)$$
  
  $$\mathrm{n\; cos\; e}\mathrm{=}\mathrm{cos\; r}\left({\mathrm{e}}_{\min }\mathrm{=}\mathrm{arc\; cos}\frac{\mathrm{1}}{\mathrm{n}}\right)$$
  
  $$\mathrm{M}\mathrm{=}\left(\begin{array}{c}{\mathrm{y}}_{\mathrm{e}}\mathrm{-}\mathrm{\lambda \; cos\; r}\\ \mathrm{\lambda \; sin\; r}\end{array}\right)$$
  
  $$\overrightarrow{{\mathrm{M}}_{\mathrm{0}}\mathrm{M}}\mathrm{perpendiculaire\; à}\overrightarrow{{\mathrm{n}}_{\mathrm{0}}}\mathrm{\Rightarrow }\left({\mathrm{y}}_{\mathrm{e}}\mathrm{-}\mathrm{\lambda \; cos\; r}\mathrm{-}{\mathrm{y}}_{\mathrm{M}\mathrm{0}}\right){\mathrm{n}}_{\mathrm{0}\mathrm{y}}\mathrm{+}\left(\mathrm{\lambda \; sin\; r}\mathrm{-}{\mathrm{z}}_{\mathrm{M}\mathrm{0}}\right){\mathrm{n}}_{\mathrm{0}\mathrm{z}\mathrm{=}\mathrm{0}}$$
  
  d'où λ et M
  Par ailleurs, $$\overrightarrow{\mathrm{n}}\mathrm{=}\left(\begin{array}{c}\cos \frac{\mathrm{r}}{\mathrm{2}}\\ \mathrm{-}\sin \underline{\mathrm{r}}\end{array}\right)$$
  
  $$2$$
  
• 1b - Cas où une couche d'air 12 (Fig.7) se trouve entre l'émetteur 3 de la LED et la plaque transparente 11a de protection
  La signification des lettres apparaît sur Fig.7, avec :
  • δ1 = épaisseur de la couche d'air 12
  • t = épaisseur de la plaque ou couche transparente 11a $${\mathrm{y}}_{\mathrm{e}}\mathrm{=}\frac{\mathrm{hs}}{\mathrm{2}}\mathrm{-}\frac{\mathrm{\delta }\mathrm{1}}{\mathrm{tg\; e}}\mathrm{-}\frac{\mathrm{t}}{\mathrm{tg}{\mathrm{r}}_{\mathrm{i}}}$$
    
    $$\mathrm{n\; cos}{\mathrm{r}}_{\mathrm{i}}\mathrm{=}\mathrm{cos\; e}$$
    
    
    e_min est tel que y_e = - f (équation en e), avec f la distance entre F et le fond du miroir mesurée selon l'axe optique, comme représenté en figure 2)
  Le reste du calcul est semblable au cas précédent.

Calculation of the reflector section

• 1a - Case of an encapsulated LED (diagram of Fig.6 ), embedded in a plate 11 or transparent protective layer: $${\mathrm{there}}_{\mathrm{e}}\mathrm{=}\frac{\mathrm{hs}}{\mathrm{2}}\mathrm{-}\frac{\mathrm{\delta }}{\mathrm{tg\; e}}$$
  
  $$\mathrm{not}\sin \left(\frac{\mathrm{\pi }}{\mathrm{2}}\mathrm{-}\mathrm{e}\right)\mathrm{=}\sin \left(\frac{\mathrm{\pi }}{\mathrm{2}}\mathrm{-}\mathrm{r}\right)$$
  
  $$\mathrm{n\; cos\; e}\mathrm{=}\mathrm{cos\; r}\left({\mathrm{e}}_{\min }\mathrm{=}\mathrm{arc\; cos}\frac{\mathrm{1}}{\mathrm{not}}\right)$$
  
  $$\mathrm{M}\mathrm{=}\left(\begin{array}{c}{\mathrm{there}}_{\mathrm{e}}\mathrm{-}\mathrm{\lambda \; cos\; r}\\ \mathrm{\lambda \; sin\; r}\end{array}\right)$$
  
  $$\overrightarrow{{\mathrm{M}}_{\mathrm{0}}\mathrm{M}}\mathrm{perpendicular\; to}\overrightarrow{{\mathrm{not}}_{\mathrm{0}}}\mathrm{\Rightarrow }\left({\mathrm{there}}_{\mathrm{e}}\mathrm{-}\mathrm{\lambda \; cos\; r}\mathrm{-}{\mathrm{there}}_{\mathrm{M}\mathrm{0}}\right){\mathrm{not}}_{\mathrm{0}\mathrm{there}}\mathrm{+}\left(\mathrm{\lambda \; sin\; r}\mathrm{-}{\mathrm{z}}_{\mathrm{M}\mathrm{0}}\right){\mathrm{not}}_{\mathrm{0}\mathrm{z}\mathrm{=}\mathrm{0}}$$
  
  from where λ and M
  Otherwise, $$\overrightarrow{\mathrm{not}}\mathrm{=}\left(\begin{array}{c}\cos \frac{\mathrm{r}}{\mathrm{2}}\\ \mathrm{-}\mathrm{<figure-callout\; id="2"\; label="sin\; r"\; filenames="imgf0001.png,imgf0003.png"\; state="\{\{state\}\}">sin\; </figure-callout>}\underset{}{\mathrm{r}}\underset{\mathrm{}}{\mathrm{}}\end{array}\right)$$
  
  $$2$$
  
• 1b - Case where an air layer 12 ( Fig.7 ) is located between the emitter 3 of the LED and the transparent plate 11a of protection
  The meaning of the letters appears on Fig.7 , with:
  • δ1 = thickness of the air layer 12
  • t = thickness of the plate or transparent layer 11a $${\mathrm{there}}_{\mathrm{e}}\mathrm{=}\frac{\mathrm{hs}}{\mathrm{2}}\mathrm{-}\frac{\mathrm{\delta }\mathrm{1}}{\mathrm{tg\; e}}\mathrm{-}\frac{\mathrm{t}}{\mathrm{tg}{\mathrm{r}}_{\mathrm{i}}}$$
    
    $$\mathrm{n\; cos}{\mathrm{r}}_{\mathrm{i}}\mathrm{=}\mathrm{cos\; e}$$
    
    
    e _min is such that y _e = - f (equation in e), with f the distance between F and the mirror bottom measured along the optical axis, as represented in figure 2 )
  The rest of the calculation is similar to the previous case.

We can then calculate a suitable tangent cylinder at any point P current of the parameter curve and thus construct the complete surface (this surface is the inner envelope - that is, the source side - of this infinity of cylinders). Advantageously, one calculates a section of each of the cylinders belonging to the desired envelope, cut by a vertical plane containing P parallel to the radius coming from F1 after reflection at P. The calculation of the cross section of the cylinder is carried out as above after projection of F and the emitter on a vertical plane passing through P and containing the normal to the parameter curve, generally elliptical, in P. Hs and f then have different values for each point P.

Preferably, the parameter curve is an elliptical arc of F and F2 foci.

Note that here, for example, F and F1 are merged or substantially merged, but this is only an example, and F and F1 can also be distinct.

Then, by calculation, the output lens is constructed as a function of a horizontal deflection parameter of the images which makes it possible to control the shape of the iso illumination curves on a measurement screen and the total width of the beam. For more details, we can refer to the method of construction described in the patent EP 1 243 846 . ^2nd case - This is particularly the case of LEDs protected by a spherical dome. A 2D construction is meaningless, since the norms for the "optics" of protection are not contained in the construction planes (therefore, the radii do not remain in the plane of section).

The principle used consists in transforming a spherical wave coming from a corner of the emitter (F, as above) into a spherical wave of center F2. The calculation obviously takes into account the deviations due to the protective dome (which is not centered on the focus).

The procedure is relatively simple, which comes from the fact that it is desired to make a low-cut beam, regardless of the choice of a beam converging in a top view towards F2.

• l'ensemble de LEDs fixées sur une plaque de circuit imprimé et/ou un radiateur ;
• les réflecteurs, incluant des pattes de fixation (non représentées) vers le radiateur et la lentille ;
• la lentille.

Among the advantages provided by the invention include the vertical lens L, La with smooth exit surface. In addition only three optical parts are to be assembled namely:

• the set of LEDs fixed on a printed circuit board and / or a radiator;
• the reflectors, including attachment tabs (not shown) to the radiator and the lens;
• The lens.

Claims (13)

Lighting module, for a motor vehicle headlamp, for giving a cut-off beam, in particular a code beam, this module admitting an optical axis, and comprising: at least one light source (S), a reflector (R, Ra, Ra1, Ra2) of the complex surface type, the light source being disposed at a focus (F) located on the optical axis or in its vicinity, and the reflector section by a horizontal plane being substantially in an elliptical arc admitting a first focus (F1) coinciding with, or adjacent to, the focus (F) where the light source is located, and a second focus (F2) located forward on the optical axis of the module, the reflector producing a cut-off beam forward, and a cylindrical lens (L, La) with substantially vertical generatrices placed between the two foci (F1, F2) of the ellipse arc, characterized in that the light source comprises or consists of at least one light-emitting diode (3, 3a, 3a1, 3a2) arranged in such a way that its light beam has a mean direction (Δ, Δa) substantially orthogonal to the geometric axis of the reflector (R , Ra, Ra1, Ra2), the reflector (R, Ra, Ra1, Ra2) is located, relative to the plane of the rear face (4, 4a, 4a1, 4a2) of the light-emitting diode, of the emitted beam side, and its surface is calculated taking into account the the optical protection of the light-emitting diode. Module according to claim 1, characterized in that the light-emitting diode comprises a radiator (5, 5a, 5a1, 5a2) located on the opposite side to the reflector. Module according to one of the preceding claims, characterized in that the electroluminescent diode (3) is arranged with its rear face (4) in a horizontal plane so as to emit a light beam downwards in a mean direction (Δ) substantially vertical, the radiator (5) of the light emitting diode being located above it, while the reflector (R) is located below the horizontal plane of the rear face of the diode. Module according to one of the preceding claims 1 or 2, characterized in that the light-emitting diode (3) is arranged with its rear face (4) in a horizontal plane so as to emit a light beam upwards in a mean direction ( Δ) substantially vertically, the radiator (5) of the light-emitting diode being in particular located below it, while the reflector (R) is located above the horizontal plane of the rear face of the diode. Module according to claim 1 or 2, characterized in that the light-emitting diode (3a, 3a1, 3a2) is disposed with its rear face in a substantially vertical plane so as to emit a light beam having a substantially horizontal mean direction (Δa), the radiator (5a, 5a1, 5a2) of the light-emitting diode being located behind it, while the reflector (Ra, Ra1, Ra2) is located in front of the light-emitting diode, facing downwards, and a reflecting mirror (7) is disposed below the reflector to return the beam to the lens (La). Module according to claim 1 or 2, characterized in that the light-emitting diode (3a, 3a1, 3a2) is disposed with its rear face in a substantially vertical plane so as to emit a light beam having a substantially horizontal mean direction (Δa), the radiator (5a, 5a1, 5a2) of the light-emitting diode being located behind it, while the reflector (Ra, Ra1, Ra2) is located in front of the light-emitting diode, facing upwards, and a reflecting mirror (7) is disposed above the reflector to send the beam back to the lens (La). Module according to one of claims 5 or 6, characterized in that the reflecting mirror (7) is plane or cylindrical. Module according to one of claims 5 or 6, characterized in that the reflecting mirror (7) is inclined at approximately 45 ° in the horizontal plane. Motor vehicle light projector, characterized in that it comprises at least one module (M, Ma, Ma1, Ma2) according to any one of the preceding claims. Motor vehicle light projector according to claim preceding embodiment comprising several modules according to one of the preceding claims, characterized in that the modules (Ma, Ma1, Ma2) are juxtaposed or stacked with the rear faces (4a, 4a1, 4a2) of the light-emitting diodes (3) located in the same plan (6). Light projector according to the preceding claim, characterized in that the modules (Ma, Ma1, Ma2) are stacked and have beams angularly offset in horizontal projection, from bottom to top and are switched on successively according to the steering of the wheels of the vehicle, for Gradual turning lighting (PBL). Light projector according to claim 9, characterized in that it comprises three or four stacked modules (Ma, Ma1, Ma2) and beams angularly offset. Illuminated headlamp according to one of Claims 8 to 10, characterized in that the reflecting mirror (7) is arranged above or below the reflector of the lower module (Ra1, Ra2) and preferably forms with it a single piece.

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