EP3470728B1 - Light module for a motor vehicle - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION

The invention relates to the technical field of light modules for motor vehicle lighting.

• au moins une matrice de sources lumineuses rangées en au moins une ligne horizontale et en colonnes verticales, les sources lumineuses étant des surfaces émettrices de diodes électroluminescentes qui sont toutes agencées sur un substrat commun ;
• au moins un dispositif d'imagerie conçu pour projeter les sources lumineuses en un faisceau lumineux dans lequel chaque source lumineuse produit un pixel lumineux, l'activation des sources lumineuses d'une ligne formant une ligne lumineuse de pixels lumineux éclairée de manière homogène, le dispositif d'imagerie comportant au moins une première surface focale objet présentant un défaut de courbure de rayon de courbure déterminé.

The invention relates more particularly to a motor vehicle light module comprising:

• at least one matrix of light sources arranged in at least one horizontal row and in vertical columns, the light sources being emitting surfaces of light-emitting diodes which are all arranged on a common substrate;
• at least one imaging device designed to project the light sources into a light beam in which each light source produces a light pixel, the activation of the light sources of a line forming a light line of light pixels illuminated homogeneously, the imaging device comprising at least one first object focal surface having a curvature defect of determined radius of curvature.

TECHNICAL BACKGROUND OF THE INVENTION

Light modules of this type are already known. They are capable of emitting a segmented light beam longitudinally forward. The lighting device comprises a matrix of elementary light sources which is projected forward by an imaging device to form the segmented light beam into a matrix of light pixels. Each light pixel is illuminated by an associated light source. The light sources are capable of being activated in a manner individual and independent. By selectively switching on or off each of the elementary light sources, it is possible to create a light beam that specifically illuminates certain areas of the road in front of the vehicle, while leaving other areas in darkness.

Such an optical lighting module is used in particular to perform an adaptive lighting function also called "ADB", an acronym for the English expression "Adaptive Driving Beam". Such an ADB function is intended to automatically detect a road user likely to be dazzled by a lighting beam emitted in high beam mode by a headlight, and to modify the contour of this lighting beam so as to create a shadow zone at the location of the detected user while continuing to illuminate the road with a long-range beam on either side of the user. The advantages of the ADB function are numerous: ease of use, better visibility compared to lighting in dipped beam mode, greatly reduced risk of dazzling, safer driving, etc.

Such an optical module generally comprises a matrix of light sources, generally formed by light-emitting diodes (LEDs), and an imaging device. The light-emitting diodes are arranged on the surface of a flat substrate that extends in a plane orthogonal to the main emission direction of the light-emitting diodes. Each light source is imaged by the projection optics to form a light pixel. Each light pixel is capable of being selectively illuminated by activating or deactivating each light source.

Such an optical module is however likely to be subject to optical aberrations such as spherical aberration, coma aberration, distortion aberration, astigmatism, field curvature aberration, etc.

The present invention relates more particularly to solving the problems posed by field curvature aberration also called "Petzval field curvature". Theoretically, the imaging device is supposed to have an object focal surface formed by a plane orthogonal to the optical axis of said optics. However, this object focal surface actually has a concave spherical curvature.

As a result, since the light sources of the matrix are arranged in a plane orthogonal to the optical axis of the projection optics, only the secondary elementary light sources located on the curved object focal surface are projected sharply. The other light sources located in front of or behind the curved object focal surface will be projected more or less blurred depending on their longitudinal distance from the object focal surface. The further the light source is from the object focal surface, the more blurred the associated light pixel will be.

The array of light sources generally has a horizontal dimension much greater than its vertical direction. Thus, the light sources arranged at each end of a line are sufficiently far from the object focal surface for the curvature defect to have visible effects on the corresponding light pixels. The curvature defect therefore has annoying effects on the horizontal lines of light pixels, while the effects on the vertical columns of light pixels are barely perceptible to the naked eye.

To solve this problem, it has already been proposed to interpose a primary optical element between the light sources and the imaging device. The primary optical element comprises, for example, light guides, each of which is associated with a light source. The output faces of the light guides are arranged on a curved surface matching the curvature of the real object focal surface of the projection optics. The device imaging then projects an image of the output faces of the light guides.

Since the light-emitting diodes are carried by a flat printed circuit board, the input faces of the light guides are arranged in the same plane. As a result, the light guides located transversely at a distance from the optical axis of the projection optics have a length greater than that of the light guides located near said optical axis. Such a primary optical element is not easy to manufacture because of the variable lengths of the light guides.

Furthermore, the length of the light guides located at the ends of the primary optical element is such that the choice of material for making the primary optical element is limited, for example, to silicone. In particular, it is very complex and extremely expensive to make the light guides from polycarbonate or PMMA.

It has also been proposed to interpose an optical element for correcting the field curvature between the imaging device and the light source matrix.

However, such a solution again requires adding an element to the light module. The manufacturing cost and the weight of the light module are then increased. A motor vehicle light module according to the preamble of claim 1 is known from documents US 2001/019486 A1 And EP 2 505 910 A2 .

BRIEF SUMMARY OF THE INVENTION

• au moins une matrice de sources lumineuses rangées en au moins une ligne horizontales et en colonnes verticales, les sources lumineuses étant des surfaces émettrices de diodes électroluminescentes qui sont toutes agencées sur un substrat commun ;
• au moins un dispositif d'imagerie conçu pour projeter les sources lumineuses en un faisceau lumineux dans lequel chaque source lumineuse produit un pixel lumineux, l'activation des sources lumineuses d'une ligne formant une ligne lumineuse de pixels lumineux éclairée de manière homogène, le dispositif d'imagerie comportant au moins une première surface focale objet présentant un défaut de courbure de rayon de courbure déterminé ;

caractérisé en ce que la matrice est montée sur une monture qui permet d'ajuster son rayon de courbure de manière à ce que le substrat présente, dans un plan horizontal, une forme courbe au moins en partie parallèle ou confondue à la première surface focale objet du dispositif d'imagerie.The invention provides a motor vehicle light module comprising:

• at least one matrix of light sources arranged in at least one horizontal row and in vertical columns, the light sources being emitting surfaces of light-emitting diodes which are all arranged on a common substrate;
• at least one imaging device designed to project the light sources into a light beam in which each light source produces a light pixel, the activation of the light sources of a line forming a light line of light pixels illuminated homogeneously, the imaging device comprising at least one first object focal surface having a curvature defect of determined radius of curvature;

characterized in that the matrix is mounted on a mount which allows its radius of curvature to be adjusted so that the substrate has, in a horizontal plane, a curved shape at least partly parallel or coincident with the first focal surface object of the imaging device.

Such a shape of the substrate makes it possible to arrange each light source of a line at a unique distance from the first object focusing surface of the imaging device. As a result, the light pixels obtained by projection of the light sources of the same line have substantially the same light intensity profile regardless of their position along the line. In particular, a light pixel located at the end of the line will have substantially the same light intensity distribution as a light pixel located in the middle of the line.

According to another aspect of the invention, the substrate which carries the matrix of light sources is flexible at least in a horizontal plane to adapt its radius of curvature to the radius of curvature of the first object focal surface.

Flexible means that the substrate can be bent under stress and that it returns to its original shape when the stress is removed. In particular, the substrate can return to a planar shape in its unstressed state.

It is thus possible to adapt the radius of curvature of the substrate to the radius of curvature of the first object focusing surface of the imaging device. This makes it possible in particular to use the same model of light source matrix with different imaging devices. This also allows the matrix curvature radius to be perfectly adjusted to each imaging device.

Alternatively, the substrate is also flexible in a vertical plane to form a portion of a sphere after deformation.

According to another aspect of the invention, the imaging device comprises an entry face for the light rays, the imaging device being designed so that the first object focal surface has a radius of curvature determined so that, in projection in a horizontal plane, the circle virtually extending said first object focal surface passes through the end edges of the entry face for the light rays.

This very advantageously makes it possible to improve the luminous efficiency of the light module by increasing the luminous flux of the light sources emitted by the light sources located at the end of the line through the imaging device.

According to a variant of the invention, the light sources are merged with the first focal surface object of the imaging device.

This variant is particularly interesting when the light sources of the same line are substantially contiguous.

According to another aspect of the invention, the light sources are offset rearwardly relative to the first object focal surface by a determined offset distance.

For example, the offset distance is defined such that a cone whose base rests on the circumference of the input face of the imaging device and whose apex is located on the focus intercepts, in the extension of its apex, a segment whose length is equal to the distance between the center of two consecutive light sources of the same line.

This improves the light homogeneity of the light beam emitted by the light module.

According to a first embodiment of the invention, the imaging device comprises a single object focal surface which is formed by said first object focal surface.

Such an imaging device is simpler to design.

According to a first variant of the first embodiment, the matrix of light sources comprises at least two horizontal lines of light sources and the vertical distance separating two adjacent light sources of the same column is substantially equal to the horizontal distance separating two adjacent light sources of the same line so that, in the light beam, the light lines of light pixels overlap vertically.

According to a second variant of the first embodiment, the matrix of light sources comprises at least two horizontal lines of light sources and the vertical distance separating two adjacent light sources of the same column is greater than the horizontal distance separating two adjacent light sources of the same line so that, in the light beam, the light lines of light pixels appear distinctly from each other with vertical interposition of darker intermediate lines.

According to this second variant, the invention also relates to a segmented light beam projector for a motor vehicle which comprises two light modules each produced according to the invention, the lines of light pixels of one light beam being interposed between the lines of light pixels of the other light beam to create a homogeneous overall light beam.

According to a second embodiment of the invention, the imaging device comprises a second object focal surface, the first object focal surface focusing the light rays in a horizontal plane, and the second object focal surface focusing the light rays in a vertical plane, the light module comprising a primary optical element which shapes the light rays emitted by the light sources to obtain vertically adjoining secondary light sources which are arranged in coincidence with or close to the second object focal surface.

This advantageously makes it possible to obtain a homogeneous light beam in which the light pixels also overlap vertically.

BRIEF DESCRIPTION OF THE FIGURES

• la figure 1 est une vue de côté qui représente schématiquement un véhicule automobile équipé d'un module lumineux réalisé selon les enseignements de l'invention qui éclaire un écran transversal ;
• la figure 2 est une vue de face qui représente l'écran éclairé par le faisceau lumineux émis par le module lumineux de la figure 1 qui est segmenté en plusieurs pixels lumineux chevauchants ;
• la figure 3 est un diagramme qui représente le profil d'intensité lumineuse de trois pixels lumineux adjacents du faisceau lumineux en fonction de leur position sur un axe transversal de l'écran ;
• la figure 4 est une vue en perspective qui représente schématiquement le module lumineux réalisé selon un premier mode de réalisation de l'invention ;
• la figure 5 est une vue de face qui représente une matrice de sources lumineuses qui équipe le module lumineux de la figure 4 ;
• la figure 6 est une vue en coupe longitudinale transversale selon le plan de coupe 6-6 de la figure 4 qui représente le substrat courbé de la matrice de sources lumineuses ainsi que la première surface de focalisation objet d'un dispositif d'imagerie du module lumineux ;
• la figure 7 est une vue similaire à celle de la figure 6 qui représente une variante de réalisation de l'invention dans lequel la première surface de focalisation a été prolongée par un cercle passant par des bords d'extrémité de la surface d'entrée du dispositif d'imagerie ;
• la figure 8 est une vue en coupe verticale longitudinale selon le plan de coupe 8-8 de la figure 4 ;
• la figure 9 est une vue de face similaire à celle de la figure 2 dans laquelle l'écran est éclairé par un projecteur comportant deux modules lumineux réalisés selon une variante du premier mode de réalisation de l'invention ;
• la figure 10 est une vue en coupe longitudinale transversale qui représente schématiquement le projecteur comportant les deux modules qui éclairent l'écran de la figure 9 ;
• la figure 11 est une vue similaire à celle de la figure 6 qui représente un module lumineux réalisé selon un deuxième mode de réalisation de l'invention dans lequel il comporte un élément optique primaire et dans lequel le dispositif d'imagerie comporte deux surfaces de focalisation objet distinctes ;
• la figure 12 est une vue similaire à celle de la figure 8 qui représente le module lumineux réalisé selon le deuxième mode de réalisation de l'invention ;
• la figure 13 est une vue similaire à celle de la figure 12 qui représente une variante du deuxième mode de réalisation de l'invention.

Other features and advantages of the invention will become apparent upon reading the detailed description which follows, for the understanding of which reference will be made to the appended drawings in which:

• there figure 1 is a side view which schematically represents a motor vehicle equipped with a light module produced according to the teachings of the invention which illuminates a transverse screen;
• there figure 2 is a front view showing the screen illuminated by the light beam emitted by the light module of the figure 1 which is segmented into several overlapping light pixels;
• there figure 3 is a diagram that represents the luminous intensity profile of three adjacent luminous pixels of the light beam as a function of their position on a transverse axis of the screen;
• there figure 4 is a perspective view which schematically represents the light module produced according to a first embodiment of the invention;
• there figure 5 is a front view that represents a matrix of light sources that equips the light module of the figure 4 ;
• there figure 6 is a transverse longitudinal sectional view along section plane 6-6 of the figure 4 which represents the curved substrate of the light source matrix as well as the first focusing surface object of an imaging device of the light module;
• there figure 7 is a view similar to that of the figure 6 which represents an alternative embodiment of the invention in which the first focusing surface has been extended by a circle passing through end edges of the input surface of the imaging device;
• there figure 8 is a longitudinal vertical sectional view along section plane 8-8 of the figure 4 ;
• there figure 9 is a front view similar to that of the figure 2 in which the screen is illuminated by a projector comprising two light modules produced according to a variant of the first embodiment of the invention;
• there figure 10 is a transverse longitudinal sectional view which schematically represents the projector comprising the two modules which illuminate the screen of the figure 9 ;
• there figure 11 is a view similar to that of the figure 6 which represents a light module produced according to a second embodiment of the invention in which it comprises a primary optical element and in which the imaging device comprises two distinct object focusing surfaces;
• there figure 12 is a view similar to that of the figure 8 which represents the light module produced according to the second embodiment of the invention;
• there figure 13 is a view similar to that of the figure 12 which represents a variant of the second embodiment of the invention.

DETAILED DESCRIPTION OF THE FIGURES

In the remainder of the description, elements having an identical structure or similar functions will be designated by the same reference.

In the remainder of the description, a local reference point linked to the light module will be adopted, without limitation, having longitudinal orientations, oriented from back to front and corresponding to the normal direction of movement of the vehicle, vertical orientation, oriented from bottom to top, and transverse orientation, oriented from left to right, indicated by the trihedron "L, V, T" in the figures. The vertical orientation is used here as a geometric reference point for the description of the light module, without relation to the direction of gravity.

Furthermore, the vertical and transverse orientations are independent of a reference point linked to the vehicle. As a non-limiting example, in the example of the figure 1 , the transverse orientation extends from one wing to the other of the vehicle parallel to the road, while the vertical orientation extends orthogonally to the road, from the wheels to the roof of the vehicle. However, it will be understood that the light module can also be arranged in the vehicle such that the vertical and transverse orientations are rotated about the longitudinal axis relative to the vehicle.

It was represented at the figure 1 a motor vehicle 10 equipped with a headlight 12 which produces a light beam 14 segmented into light pixels which performs a specific lighting function. In a non-limiting manner, this is a high beam function. The light beam 14 is emitted along a substantially longitudinal emission axis "A" towards the front of the vehicle 10.

For the purposes of the description, a vertical transverse screen 16 has been arranged at a determined longitudinal distance in front of the vehicle 10. The screen 16 is here arranged 25 m from the vehicle.

As shown in the figure 2 , a transverse axis "H" and a vertical axis "V" have been drawn on the screen 16, which are concurrent with the axis "A" of emission of the light beam 14. The axes "H" and "V" are graduated in degrees of opening of the light beam.

The light beam 14 illuminates an area 18 of the screen 16. This illuminated area 18 is divided into a matrix of juxtaposed light pixels 20 which are arranged in transverse lines and vertical columns. The light pixels 20 can be activated individually and independently of each other.

The term "juxtaposed" means that two adjacent luminous pixels 20, vertically or transversely, overlap. Thus, when all the luminous pixels 26 are lit, the light beam 14 illuminates the area 18 of the screen 16 in a substantially uniform manner. When a luminous pixel 20 is extinguished, a portion of the space that it occupied on the screen 16 is not illuminated by the neighboring pixels.

More particularly, each light pixel 20 has a bell-shaped light intensity profile along a cutting line. The overlap of two light pixels 20 is defined by the fact that the light profiles of two successive light pixels along a line, for example transverse, intersect.

There figure 3 gives a non-limiting example of overlapping of the luminous pixels 20. The figure 3 represents the luminous intensity profiles of three adjacent luminous pixels 20A, 20B, 20C projected on the screen 16. Each luminous pixel 20A, 20B, 20C has a bell-shaped luminous intensity profile, the maximum luminous intensity Imax being located at the center of the luminous pixel 20A, 20B, 20C. As can be seen, the luminous pixel 20A on the left overlaps the central luminous pixel 20B so that the luminous intensity curves intersect at a point "P1" having a luminous intensity substantially equal to half of the maximum luminous intensity Imax. Similarly, the right luminous pixel 20C overlaps the central luminous pixel 20B so that the luminous intensity curves intersect at a point "P2" having a luminous intensity substantially equal to half of the maximum luminous intensity Imax. A central strip comprising the top of the bell is illuminated only by the central luminous pixel 20B and this central strip is surrounded by strips illuminated in a degraded and low-intensity manner, which extend from the central strip respectively to the points P1 and P2.

In a variant of the invention that is not shown, each light pixel has a light profile approaching a crenel shape in which the top of the bell is spread out to substantially form a plateau. In this case, the crossing between two light intensity profiles of two successive light pixels occurs at a light intensity less than half the maximum intensity.

According to another variant not shown of the invention, for example when the light sources are projected in a blurred manner, the space occupied by a given light pixel is likely to be entirely illuminated by the adjacent light pixels. In this case, to obtain a completely dark area, it is necessary to extinguish at least two adjacent pixels.

To produce such a light beam 14, the projector 12 comprises at least one light module 22. As is for example shown in figure 4 , the light module 22 comprises at least one matrix 24 of light sources 26 and at least one imaging device 28 which is designed to project the light sources by forming the light beam 14 in which each light source 26 produces a light pixel 20. The light sources 26 are here all identical in dimensions.

More particularly, the light sources 26 are formed by light-emitting surfaces of light-emitting diodes. They are all arranged on a front face 29 of a common substrate 30. The common substrate 30 has a plate shape which extends in a generally vertical transverse plane

More particularly, all the light sources 26 are arranged in the same plane parallel to or merged with the face 29. For example, if the light-emitting diodes protrude relative to the face 29, they all protrude by the same distance.

The light sources 26 are arranged in horizontal rows 32 and vertical columns 34. The matrix 24 here has a greater number of columns 34 than rows 32. As a result, the matrix has a transverse width much greater than its vertical height.

In the embodiment shown in figure 5 , two adjacent light sources 26 of the same line 32 are spaced apart by a first transverse distance "D1". Here, the transverse distance "D1" is the same for all the light sources 26 of the same line 32.

Similarly, two adjacent light sources 26 of the same column 34 are spaced apart by a second vertical distance “D2”. Here, the vertical distance “D2” is the same for all light sources of the same column 34.

The light module 22 comprises at least one imaging device 28 which is designed to project an image of each light source 26 substantially to infinity. The imaging device 28 is in particular designed to project the light sources 26 by forming the light beam 14 in which each light source 26 produces a light pixel 20.

In the embodiments shown in the figures, the imaging device 28 is in the form of a single lens. It will nevertheless be understood that the imaging device may also comprise at least one reflective element and/or one or more lenses.

Generally, the imaging device 28 has an entry face 36 for the light rays and an exit face 38 for the light beam 14.

The imaging device 28 has at least a first focal length F1 and a first generally vertical transverse object focal surface 40 which is arranged substantially in coincidence with the light sources 26.

The first object focal surface 40 is notably arranged so that, when all the light sources 26 of a line 32 are activated, the screen 16 is illuminated homogeneously by a luminous line of corresponding luminous pixels 20.

In common usage, the object focal surface 40 of the imaging device 30 is represented as a first approximation by a planar object focal surface 40 that is perfectly orthogonal to the optical axis "A". However, in reality, it is known that the projection optics 14 have an object focal surface that has a concave spherical curvature defect. Such a defect is called Petzval field aberration. The curvature defect has a radius of curvature of determined radii of curvature. Thus, as shown for example in figure 6 , in section view along a horizontal cutting plane, the first object focal surface 40 appears as an arc of a circle.

In order for the luminous pixels 20 of the same line to have uniform sharpness, the invention proposes that the substrate 30 of the matrix 24 has, in a horizontal plane, a curved shape at least partly parallel to the first object focal surface 40 of the imaging device 28. In particular, the part of the substrate 30 comprising the light sources 26 may have, in a horizontal plane, a curved shape parallel to the first object focal surface 40 of the imaging device 28 while the ends of the substrate 30 located on either side of the part of the substrate 30 comprising the light sources 26 may have, in this same horizontal plane, a shape parallel or not to the first object focal surface 40 of the imaging device 28.

According to an example shown in the figure 6 , the entire substrate 30 of the matrix 24 has, in a horizontal plane, a curved shape parallel to the first object focal length 40 of the imaging device.

The substrate 30 is thus curved so that its front face 29 has the shape of a cylinder sector with vertical generatrices and a horizontal circular arc directrix. The radius of curvature of the substrate 30 is determined so that each line 32 of light sources 26 is parallel with the object focal surface 40 taken along a horizontal section plane passing through said line 32. Thus, all the light sources 26 of the same line 32 are arranged at the same distance from the first object focal surface 40.

Advantageously, the substrate 30 which carries the matrix 24 of light sources 26 is flexible at least in a horizontal plane to precisely adapt its radius of curvature to the radius of curvature of the first object focal surface 40. The substrate 30 is for example elastically flexible, the front face 29 of the substrate 30 having a planar shape in its unstressed state, as shown in broken lines in FIG. figure 6 . This makes it possible to precisely adjust the radius of curvature of the substrate 30 to the curvature defect of the associated imaging device 30.

In practice, the die 24 is mounted on a mount which allows its radius of curvature to be adjusted. The mount comprises, for example, two clamping jaws 35 which are each arranged against a vertical edge of the substrate 30 and which transversely clamp the substrate 30 to constrain it in the desired curved position.

In a variant not shown, the mount has a curved support surface against which a rear face of the substrate 30 is fixed, for example by gluing or by elastic interlocking or by any other suitable fixing means.

When the transverse distance "D1" which separates two adjacent light sources 26 of the same line 32 is substantially zero, it is possible to make the first object focal surface 40 coincide perfectly with the light sources to obtain homogeneous illumination of a line of corresponding light pixels 20. The light sources 26 are thus merged with the first object focal surface 40 of the imaging device 28.

Generally, the transverse distance "D1" between two adjacent light sources 26 of the same line 32 is not zero. For example, the transverse distance "D1" is between 10% and 50% of the width of a light source 26. To enable uniform illumination of the screen 16 by the corresponding line of light pixels 20, the object focal surface 40 is offset longitudinally forward by a longitudinal distance "D3" relative to the closest light sources 26, as shown in FIG. figure 6 . This allows the light source 26 to be imaged by a slightly blurred and more transversely spread light pixel 20 which overlaps the adjacent pixels 20, thus making the dark spaces between two transversely adjacent light sources 26 disappear. In this case, the radius of curvature of the substrate 30 is equal to the sum of the radius of curvature of the first object focal surface 40 and the longitudinal offset distance "D3".

In the embodiment shown in figure 6 , the offset distance "D3" is defined so that a cone 43 whose base rests on the circumference of the entry face 36 of the imaging device 28 and whose apex is located on the focus of the imaging device 28 intercepts, in the extension of its apex, a segment whose length is equal to the distance between the center of two consecutive light sources 26 of the same line 32. It will be noted that the opening angle "a" of the cone 43 corresponds to the opening angle of the imaging device 28.

According to another aspect of the invention, a virtual circle "C" is defined which is formed by extending the first object focal plane 40. The imaging device 28 is advantageously designed so that the first object focal plane 40, in projection in an axial horizontal plane, has a radius of curvature determined so that the circle "C" passes through the end edges of the entry face 36 of the light rays, as illustrated in FIG. figure 7 . Thus, the end edges of the entrance face 36 delimit an arc 41 of the circle "C". The so-called "inscribed angle" theorem states that an angle inscribed in the circle "C" which intercepts said arc 41 has the same value "a" regardless of the position of its vertex on the circle "C". The angle "α" corresponds to the opening angle of the imaging device 28.

In optical terms, and in the context of the invention, this means that the luminous flux produced by a light source 26, arranged in the vicinity of the first object focal surface 30, passing through the input face 36 of the imaging device 28 is substantially identical for all the light sources 26 of said line 32. This configuration thus makes it possible to very substantially improve the luminous efficiency of the light sources 26 arranged at the end of the line 32 compared to a light module in which the light sources are arranged on a flat substrate. This configuration also helps avoid vignetting optical aberrations.

According to a first embodiment of the invention which is described with reference to figures 4 , 6 , 7 And 8 , the imaging device 28 comprises a single object focal surface which is formed by said first object focal surface 40.

The matrix 24 of light sources 26 is designed so that the vertical distance "D2" separating two adjacent light sources 26 of the same column 34 is substantially equal to the horizontal distance "D1" separating two adjacent light sources 26 of the same line 32. Thus, the light beam 14 illuminates the screen 16 in such a way that the light lines of light pixels 20 overlap vertically, in the same way as two light pixels 20 of the same line 32. The light beam 14 thus illuminates the screen 16 homogeneously.

As shown in the figure 8 , when the substrate 30 is flexible in only one plane, the matrix 24 has, in vertical axial section, a rectilinear shape, while the first object focal surface 40 has the shape of an arc of a circle. However, this configuration is not inconvenient because, as explained above, the vertical dimension of the matrix 24 is much smaller than its transverse dimension. As a result, the blur created by the effect of the field curvature is not perceptible to the naked eye on the luminous pixels 20 of the same column.

However, it is not always easy to obtain a 24 matrix presenting light sources so close together vertically.

To solve this problem, the invention proposes a variant of this first embodiment which is shown in figures 9 And 10 . The vertical distance "D2" separating two adjacent light sources 26 of the same column 34 is greater than the horizontal distance "D1" separating two sources adjacent luminous pixels 26 of the same line 32 so that, in the light beam 14A, the lines 42A of luminous pixels 20 appear distinctly from each other with the interposition of darker intercalary lines, as shown in the figure 9 .

To enable uniform illumination of the screen 16, the projector 12 then comprises two similar light modules 22A, 22B. The second light module 22B is arranged so as to project a light beam 14B having lines 42B of light pixels 20 between the lines 42A of light pixels of the other light beam 14A to create a uniform overall light beam.

The two light modules 22A, 22B are here arranged in the same projector 12. The projector 12 comprises a common housing 44 closed by a glass 46 enclosing the two light modules 22A, 22B.

Alternatively, to solve the problem posed when the vertical distance "D2" between the light sources 26 of the matrix 24 is too great, the invention proposes a second embodiment of the invention which is shown in figures 11 And 12 .

In this embodiment, the imaging device 28 is a bifocal device, sometimes also called astigmatic, which comprises, in addition to the first object focal surface 40, a second object focal surface 48. The second object focal surface 48 is arranged at a focal length "F2" relative to the optical center of the imaging device 28.

The first object focal surface 40 focuses the light rays in a horizontal plane, while the second object focal surface 48 focuses the light rays in a vertical plane.

The light module further comprises a primary optical element 50 which shapes the light rays emitted by the light sources 26 to obtain light sources 52 vertically adjoining secondary lenses which are arranged on the second object focal surface.

The primary optical element 50 is an optical part, or a set of optical parts and/or structures, arranged to transfer the light emitted by said light sources 26 onto a virtual projection surface, which is located opposite and at a predefined distance from the matrix 24, in the direction of light emission, to form the secondary light sources 52 there.

In the example shown in the figure 12 the virtual surface is advantageously a virtual concave surface in the form of a portion of a sphere parallel to or merged with the second object focusing surface 48.

Alternatively, the virtual projection surface may be a portion of a cylinder parallel to the front face of the matrix 24.

Advantageously, each secondary light source 52 has a height greater than that of each associated light source 26. Thus, the secondary light sources 52 are here vertically adjoining.

Of course, the primary optical element 50 can be made in a single optical part but can comprise at least two optical parts which can have different shapes and/or refractive indices. Said at least two parts can also be made of different materials and can comprise coatings to improve the light transmission efficiency, such as an anti-reflective coating. In order to optimize the efficiency and the quality of the beam projected by the light module, the primary element 50 can comprise diffractive or refractive structures, such as diffraction gratings or Fresnel structures.

In the embodiment shown in figures 11 And 12 , the primary optical element 50 comprises several layers of light guide 54, each of which is arranged facing a line 32 of associated light sources 26.

A guide sheet 54 is defined as an optical part capable of guiding light by total internal reflection of this light, for example from an entry face to an exit face. A guide sheet 54 has a small thickness compared to its length and its width.

Thus, each guide sheet 54 has an upper face 56 and a lower face 58 of extended guidance separated by a perimeter. This perimeter defines a thickness of the guide sheet 56, which can be variable, for example increasing from one end to the other. The perimeter comprises a transverse vertical rear face 60 for entering the light common to all the light sources 26 of the associated line 32. The rear entry face 60 is arranged close to the associated light sources 26, for example a few millimeters away.

The light emitted by the light sources 26 which enters through the rear face 60 propagates inside the guide sheet 60 by successive total internal reflections against the upper and lower faces 56, 58 in the direction of a vertical transverse front exit face 62. The front face 62 forms a portion of the periphery of the guide sheet 54.

In the embodiment shown in the figures, the outlet face 62 of each guide sheet 54 has a height greater than that of its inlet face 60. As a result, each guide sheet 54 has, in transverse longitudinal section, a divergent profile from its inlet face 60 to its outlet face 62.

The input face 60 has a height which is substantially equal to the height of the emission surface of the associated light sources 26.

The exit face 62 is thus illuminated over its entire height by the associated light sources 26, thus forming a line of secondary light sources 52.

The first object focusing surface 40 of the imaging device 28 is arranged in the same manner as in the previous embodiments, i.e. in coincidence with or in proximity to the light sources 26. The second object focusing surface 48 which is arranged substantially in coincidence with the exit faces 62 of the guide sheets 54.

Thus, for each light source 26 arranged substantially close to the first object focusing surface 40, the light rays emitted by the emission surface of said light source 14 are projected in parallel by the imaging device 28 in longitudinal vertical planes, such that the light beam associated with said light source 26 creates a light segment of generally rectangular shape delimited transversely by vertical edges which are the clear image of the vertical edges of the emission surface.

Likewise, each light source 26 creates a secondary light source 52 on the output face 62 of the guide sheet 20. Each secondary light source 52 is thus delimited vertically by two transverse edges which coincide with the edges formed by the upper and lower faces 56, 58 with the output face 62.

The output face 62 being arranged substantially in coincidence with the second object focusing surface 48, the light rays emitted by each secondary light source 52 are therefore projected in parallel by the imaging device 28 in longitudinal transverse planes, so that the light beam associated with said light source 20 creates a light segment of generally rectangular shape delimited vertically by vertical edges which are the image clear of the transverse edges of the secondary light source 52.

The secondary light sources 52 being substantially contiguous, the pixels 20 obtained are also contiguous vertically.

For the same reasons of homogeneity of the light beam 14, it may be possible to slightly shift the second object focal surface 48 forwards relative to the secondary light sources 52 to make it possible to obtain light pixels 20 which overlap slightly vertically, in the sense explained above.

As a variant of the invention shown in figure 13 , the guide sheet is replaced by reflective surfaces. In this case, the space that was occupied by the guide sheet of the figure 12 is left empty, while the reflecting surfaces are carried by prisms 64 which extend longitudinally from their base 66 located on the front face of the substrate 24, between two lines 32 to a free front transverse edge 68. The upper 58 and lower 56 faces of the prisms 64 form reflecting surfaces. The prisms exactly fill the voids between two guide sheets of the figure 12 . This embodiment works in the same way as the embodiment of the figure 12 and it provides the same benefits.

Thanks to the light module produced according to any of the embodiments previously described, the pixels obtained are sharper, particularly on the transverse edges of the area illuminated by the light beam.

Furthermore, when the imaging device is designed according to the other aspect of the invention so that the virtual sphere carrying the object focusing surface passes through the edges of its input face, the luminous efficiency of the module luminous is significantly improved compared to known designs.

Claims (11)

1. Motor vehicle lighting module (22) comprising:

   - at least one matrix (24) of light sources (26) arranged in at least one horizontal row (32) and in vertical columns (34), the light sources (26) being emitting surfaces of light-emitting diodes which are all arranged on a common substrate (30);

   - at least one imaging device (28) designed to project the light sources (26) in a light beam (14) in which each light source (26) produces a light pixel (20), the activation of the light sources (26) of a row (32) forming a light row of light pixels (20) lit uniformly, the imaging device (28) comprising at least one first object focal surface (40) exhibiting a curvature defect of determined radius of curvature;

   characterized in that the matrix (24) is mounted on a mount which makes it possible to adjust its radius of curvature so that the substrate (30) has, in a horizontal plane, a curved form at least partly parallel to or coinciding with the first object focal surface (40) of the imaging device (28) and in that the front face of the substrate (30) has a planar form in its non-stressed state.
2. Lighting module (22) according to the preceding claim, characterized in that the substrate (30) which bears the matrix (24) of light sources (26) is flexible at least in a horizontal plane to adapt its radius of curvature to the radius of curvature of the first object focal surface (40).
3. Lighting module (22) according to either one of the preceding claims, characterized in that the imaging device (28) comprises an input face (36) for the light rays, the imaging device (28) being designed for the first object focal surface (40) to have a determined radius of curvature so that, in projection in a horizontal plane, the circle (C) virtually prolonging said first object focal surface (40) passes through the end edges of the input face (36) for the light rays.
4. Lighting module (22) according to any one of the preceding claims, characterized in that the light sources (26) are merged with the first object focal surface (40) of the imaging device.
5. Lighting module (22) according to any one of Claims 1 to 3, characterized in that the light sources (26) are offset to the rear relative to the first object focal surface (40) by a determined offset distance.
6. Lighting module (22) according to the preceding claim, characterized in that the offset distance (D3) is defined such a way that a cone (43) whose base bears on the circumference of the input face (36) of the imaging device (28) and whose vertex is situated on the focus intercepts, in the extension of its vertex, a segment whose length is equal to the distance between the centre of two consecutive light sources (26) of one and the same row (32).
7. Lighting module (22) according to any one of the preceding claims, characterized in that the imaging device (28) comprises a single object focal surface (40) which is formed by said first object focal surface (40).
8. Lighting module (22) according to the preceding claim, in which the matrix of light sources comprises at least two horizontal lines of light sources characterized in that the vertical distance (D2) separating two adjacent light sources (26) of one and the same column (34) is substantially equal to the horizontal distance (D1) separating two adjacent light sources (26) of one and the same row (32) such that, in the light beam (14), the light rows of light pixels (20) overlap vertically.
9. Lighting module (22) according to Claim 7, in which the matrix of light sources comprises at least two horizontal lines of light sources characterized in that the vertical distance (D2) separating two adjacent light sources (26) of one and the same column (34) is greater than the horizontal distance (DI) separating two adjacent light sources (26) of one and the same row (32) such that, in the light beam (14), the light rows of light pixels (20) appear distinct from one another with vertical interposition of darker separating rows.
10. Lighting module (22) according to any one of Claims 1 to 6, characterized in that the imaging device (28) comprises a second object focal surface (48), the first object focal surface (42) focusing the light rays in a horizontal plane, and the second object focal surface (48) focusing the light rays in a vertical plane, the lighting module (22) comprising a primary optical element (50) which forms the light rays emitted by the light sources (20) to obtain vertically contiguous secondary light sources (52) which are arranged coinciding with or in proximity to the second object focal surface (48) .
11. Headlight (12) for segmented light beams (14) for a motor vehicle, characterized in that it comprises two lighting modules (22A, 22B) each produced according to Claim 8, the rows of light pixels (20) of one light beam (14A) being interposed between the rows of light pixels (20) of the other light beam (14B) to create an overall uniform light beam.

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