EP4078020A1

EP4078020A1 - System for projecting a light beam

Info

Publication number: EP4078020A1
Application number: EP20824956.5A
Authority: EP
Inventors: Pierre Albou
Original assignee: Valeo Vision SAS
Current assignee: Valeo Vision SAS
Priority date: 2019-12-20
Filing date: 2020-12-22
Publication date: 2022-10-26
Also published as: JP7462049B2; WO2021123459A1; CN114981591A; JP2023507197A; FR3106671A1; US20240027045A1; FR3106671B1

Abstract

The invention relates to a light system comprising a pixelated light source (1) provided with a plurality of selectively activatable emissive elements and each having a rectangular shape with a height dimension and a width dimension, the width dimension being the same for all the emissive elements, and an optical device having an optical axis and configured to project an image (S) of each of the emissive elements, characterised in that the optical device is configured such that the images (S) have a width dimension that increases non-linearly as the distance from the optical axis increases.

Description

Light beam projection system

TECHNICAL AREA

The present invention relates to the field of lighting and / or signaling and the organs, in particular optical, which participate therein. It finds a particularly advantageous application in the field of motor vehicles.

STATE OF THE ART

In the automotive sector, there are known devices capable of emitting light beams, also called lighting and / or signaling functions, generally meeting regulations

[0003] Recently, technologies have been developed to produce a segmented beam, also called pixelated, to achieve advanced lighting functions. This is particularly the case for a lighting function of the "complementary road" type generally based on a plurality of illumination units each comprising a light-emitting diode, diodes which can be driven individually. This beam can, in particular, be used to supplement the lighting of a code type beam, to form a road type lighting.

[0004] The beam, resulting from the different beam segments from each of the diodes, is projected by means of a projection optical system generally comprising one or more lenses. For example, it is possible to produce a complementary beam, associated with a basic beam totally or at least mainly projected below a horizontal cut-off line of the type used for the low beam function, the complementary beam being added to the base beam so as to complete it above the cut-off line; advantageously, this complementary beam is adaptive to turn on or off certain parts of the projected overall beam, for example for anti-glare functions. The acronym ADB (for Adaptive Driving Beam meaning adaptive high beam) is used for this type of function.

In the present description, called segmented beam, a beam whose projection forms an image composed of beam segments, each segment can be lit independently. We can use a pixelated light source to form these segments. Such a source comprises a plurality of selectively activatable emissive elements. The emissive elements are typically placed next to each other on a support, with a certain pitch.

[0006] In an ideal situation, the resolution of the light sources (ie the number of pixels) is unlimited so that one can cover a wide field of view while having a high light intensity. In particular, for sources with pixels of a given power, it suffices to increase the number of pixels to widen the field.

[0007] In practice, for reasons of limiting the complexity and the cost price, it is necessary to seek light sources that are as small as possible. At the same time, the objective of sufficient resolution and the targeted light intensity (very generally imposed by regulations) do not allow a large reduction in the number of pixels is therefore the cost price of such technologies.

[0008] An object of the present invention is therefore to provide a solution to this problem, by allowing satisfactory light intensity for a sufficiently wide visual field, with a pixelized source of controlled size.

[0009] The other objects, characteristics and advantages of the present invention will become apparent on examination of the following description and the accompanying drawings. It is understood that other advantages can be incorporated.

ABSTRACT

To achieve this objective, according to one embodiment there is provided a light system comprising a pixelized light source provided with a plurality of selectively activatable emissive elements and each having a rectangular shape with a height dimension and a dimension in width, the width dimension being the same for all emissive elements, and an optical device having an optical axis and configured to project an image of each of the emissive elements, characterized in that the optical device is configured so that the images have one dimension in width increasing non-linearly as one moves away from the optical axis.

Thus, a segmented beam is produced, from the light projection deriving from the plurality of emissive elements, with a spatial modulation of the intensity and of the surface spread of the images produced by each of the emissive elements.

Image spreading is understood to mean an increase of at least one dimension in width of the images the further the images are from the optical axis. Thus, the width of the images is greater at the periphery than at the center, that is to say at the level of the optical axis and in the vicinity of the latter. This arrangement makes it possible to obtain a given visual field, with a reduced number of pixels, that is to say of emissive elements. The increase in the size of the images compensates for a reduction in the number of images.

At the same time, the light intensity of the images is also modulated so as not to penalize the level of illumination produced by the system, in particular in the main area of interest which is formed at the level of the optical axis and in its vicinity. In particular, it is in this area, towards the center of the beam projected at the front of a vehicle, that it is generally most useful to have high brightness. To achieve this, the images are smaller in the vicinity of the optical axis, which concentrates the light there and preserves the brightness at an acceptable level.

One means employed to obtain this enlargement of the images and of the pixels consists in creating a distortion, preferably causing a non-linear enlargement towards the edges of the field of view. While distortion is generally viewed as a flaw in an optical system, it is used here on purpose to modulate the size and light intensity of images.

Optionally, the first derivative of a function of the width dimension of an image relative to the angular position of the image along an axis parallel to the great width of the total illuminated field is equal to zero at optical axis level.

[0016] With this optional arrangement, the light intensity at the optical axis and its vicinity can be preserved at a high level.

Advantageously, the optical device is configured so that the images have an increasing dimension in width in a non-linear manner, and possibly in a manner greater than a linear growth, from a certain image angle (or of coordinate in width), away from the optical axis for at least one peripheral group of images. When this aspect is implemented, the increase in the width dimension of the images is greater than it would be if the growth was linear at least from a certain coordinate of the image in the width direction. This arrangement can be implemented at least on a portion of the projected beam located at the periphery, that is to say on an area extending to the contour of the beam. It is thus possible to rapidly increase the size of the images to produce a large spread, and, therefore, a higher angular field for the beam. Optionally, this arrangement can be used over the entire beam, from the optical axis. However, the increase is preferably smaller from the center (at the level of the optical axis) so as to preserve small image sizes there, and therefore high light intensity. As such, the increase can be very gradual at the start (starting from the optical axis) with a derivative of low image width (for example slower than a linear variation, possibly starting from a zero value derivative at the center), then increase as one moves away from the optical axis, to reach a derivative greater than linear growth.

Another aspect relates to an optical device that can be used in the system. It is possible to provide an optical device having an optical axis and configured to project an image of each of the emissive elements of a pixelized light source, the optical device being advantageously configured so that the images have an increasing dimension in width in a non-linear manner as they measure. that we move away from the optical axis.

[0020] The optical device may include, in one embodiment, an input optical unit and an output optical unit. In a preferred case, the input optical unit produces a distortion of the light beam, and it is in particular possible to have recourse to a lens output face of this unit produced with a high convex, preferably spherical, curvature to create a strong spatial dispersion of the rays exhibiting a large radial component.

[0021] The output optical unit may have lower optical power.

Another aspect relates to a motor vehicle equipped with at least one system and / or at least one optical device.

BRIEF DESCRIPTION OF THE FIGURES The aims, objects, as well as the characteristics and advantages of the invention will emerge better from the detailed description of an embodiment of the latter which is illustrated by the following accompanying drawings in which:

[0024] [Fig.1] Figure 1 shows an example of projection in a plane of a light beam, with a distribution of spread and light intensity of images of a pixelized source.

[0025] [Fig.2] Figure 2 shows the evolution of the light intensity and the width dimension of the images as a function of their distance from the optical axis.

[0026] [Fig.3A] [Fig.3B] Figures 3A and 3B show a first embodiment of an optical device.]

[0027] [Fig.4A] [Fig.4B] Figures 4A and 4B show a second embodiment of an optical device.

[0028] [Fig.5A] [Fig.5B] Figures 5A and 5B show a third embodiment of an optical device.

[0029] [Fig.6] Figure 6 shows another embodiment of an optical device.

[0030] The drawings are given by way of examples and are not limiting of the invention. They constitute schematic representations of principle intended to facilitate understanding of the invention and are not necessarily on the scale of practical applications.

DETAILED DESCRIPTION

[0031] Before starting a detailed review of embodiments of the invention, optional features are set out below which can optionally be used in combination or alternatively:

- the optical device comprises an input optical unit 2 receiving light from the plurality of emissive elements and an output optical unit 3 receiving light from the input optical unit 2 and projecting the images S of each of the emissive elements.

- The input optical unit 2 comprises a converging lens which has a radius of curvature / useful aperture radius ratio of less than 1.175 on its light exit face.

- the converging lens is made of a material having a refractive index, at a wavelength of 587.56nm, greater than 1.7. - the output optical unit 3 is convergent and presents an inverted chromatism, that is to say that the position of the focus on the optical axis as a function of the wavelength varies in the opposite direction compared to what it done in the case of a simple converging (refractive) lens. Unit 3 is over corrected in axial chromatism.

- the focal length of the output optical unit 3 is greater than the focal length of the input optical unit 2.

- the output optical unit 3 comprises at least two lenses.

- the output optical unit 3 comprises a diffractive optical element.

- the plurality of emissive elements form a rectangular matrix, the long dimension of the rectangular matrix being directed along the width dimension. The width dimension corresponds to the width of the beam.

- the width dimension is directed along the horizon line.

- the emissive elements have an identical dimension in height. Possibly the dimension in height is equal to that in width, so that the emissive elements have a square section.

The system according to the invention comprises a control unit for the activation of each of the emissive elements, configured to produce at least one dark zone in a projected beam by deactivation of a group of adjacent emissive elements, the control unit being configured to determine the number of emissive elements of the group of adjacent emissive elements corresponding to the dark zone as a function of the width dimension of the emissive elements.

A computer program product, preferably stored in a non-transient memory, comprises instructions which, when they are executed by a processor, make it possible to determine the emissive elements to be activated, in particular to obtain at least one area dark (in which the elements are not activated) of a determined area taking into account the variable area of the images of the elements.

In the characteristics set out below, terms relating to verticality, horizontality and transversality (or even lateral direction), or their equivalents, are understood in relation to the position in which the system of lighting is intended to be mounted in a vehicle. The terms "vertical" and "horizontal" are used in the present description to denote directions, following an orientation perpendicular to the plane of the horizon for the term "vertical" (which corresponds to the height of the systems), and following an orientation parallel to the plane of the horizon. horizon for the term "horizontal". They are to be considered in the operating conditions of the device in a vehicle. The use of these words does not mean that slight variations around the vertical and horizontal directions are excluded from the invention. For example, an inclination relative to these directions of the order of + or - 10 ° is here considered as a minor variation around the two preferred directions. With respect to the horizontal plane, the inclination is in principle between -5 ° and + 4 ° and it is between -6 ° and + 7.5 ° laterally.

In general, the refractive indices whose values are given by way of example correspond to values which would be measured at a wavelength of 587.56nm (sodium d line).

Motor vehicle headlamps can be fitted with one or more light systems arranged in a housing closed by a glass so as to obtain one or more lighting and / or signaling beams at the outlet of the headlamp.

The invention can participate in a main beam function which has the function of illuminating the scene in front of the vehicle over a large area, but also over a substantial distance, typically around two hundred meters. This light beam, due to its illumination function, is mainly located above the horizon line. It may have a slightly ascending optical axis of illumination, for example. In particular, it can be used to generate a lighting function of the “complementary” type which forms a portion of a high beam complementary to that produced by a near-field beam, the high beam seeking entirely or at least mainly to illuminate. above the horizon line while the near-field beam (which may have the characteristics of a low beam) seeks to illuminate all or at least mainly below the horizon line.

[0038] The device can also be used to train other lighting functions via or outside those described above in relation to adaptive beams.

It is specified that in the context of the present invention, the term "image" means the projection resulting from at least part of the light coming from an emissive element via the optical device of the invention in a plane located at a predetermined distance downstream of the optical device and perpendicular to the optical axis of the latter. Typically, such a plane has a vertical orientation at the front of a motor vehicle (or possibly at the rear) at a given distance from said vehicle. The variation in dimension of the images at a given distance from the optical device makes it possible to modulate the angular spread of the beam and the light intensity according to the zones of the beam.

Note that the plurality of emissive elements can be controlled so as to activate them selectively. This means that all emissive elements are not necessarily simultaneously active, i.e. emissive of light. This function allows you to modulate the shape of the rendered beam. In the event that an emissive element is not activated, its image, as projected by the optical device will be zero. It then forms an illumination void in the resulting overall beam. This vacuum is understood by coupling phenomena at the source and the effects of stray light from the optics.

The source 1 preferably comprises a support, one face of which carries emissive elements 11 which can be selectively activated, for example on the basis of LED technologies, as detailed below.

As shown schematically in Figure 3A, the light source 1 is advantageously centered on, and perpendicular to, the optical axis of the optical device 3, here represented by a group of lenses. The optical axis can be oriented substantially horizontally.

[0043] The light source 1 can in particular be designed in the form of a matrix of emissive elements whose activation can be controlled individually, to turn off or turn on any of the emissive elements. The shape of the resulting beam is thus varied with very wide flexibility. For purely illustrative purposes, it is possible to use a matrix of emissive elements, for example forming 2464 pixels, or even more, arranged in rows and columns, for example 28 rows and 88 columns. Depending on the optical parameters, in particular of distortion, allowing the spreading of the images of the pixels, one can thus, for example, obtain a visual effect equivalent to that of a source having a matrix of 28 rows and 132 columns.

In a manner known per se, the present invention can use light sources of the light-emitting diode type still commonly called LEDs. It may possibly be organic LED (s). In particular, these LEDs can be provided with at least one chip using semiconductor technology and capable of emitting light. Furthermore, the term light source is understood here to mean an assembly of at least one elementary source such as an LED capable of producing a flux leading to the generation of at least one light beam at the output of the module of the invention. In an advantageous embodiment, the output face of the source is of rectangular section, which is typical for LED chips.

Preferably, the light-emitting source comprises at least one matrix of monolithic light-emitting elements, also called a monolithic matrix. In a monolithic matrix, the light emitting elements have grown from, or have been transferred to, a common substrate, and are electrically connected so as to be selectively activatable, individually or in subsets of light emitting elements. The substrate can be predominantly of a semiconductor material. The substrate may include one or more other materials, for example non-semiconductor. Thus each electroluminescent element or group of electroluminescent elements can form a luminous pixel and can emit light when its or their material is supplied with electricity. The configuration of such a monolithic matrix allows the arrangement of selectively activatable pixels very close to each other, compared to conventional light emitting diodes intended to be soldered to printed circuit boards. The monolithic matrix within the meaning of the invention comprises electroluminescent elements of which a main dimension of elongation, namely the height, is substantially perpendicular to a common substrate, this height being at most equal to one micrometer.

Advantageously, the monolithic matrix (s) capable of emitting light rays can be coupled to a unit for controlling the light emission of the pixelated source. The control unit can thus control (one can also say control) the generation and / or the projection of a light beam pixelated by the light device. The control unit can be integrated into the lighting device. The control unit can be mounted on one or more of the dies, the assembly thus forming a light module. The control unit may include a central processing unit coupled with a memory on which is stored a computer program which comprises instructions allowing the processor to perform steps generating signals allowing control of the light source. The control unit can thus for example individually control the light emission of each pixel of a matrix. In addition, the luminance obtained by the plurality of electroluminescent elements is at least 60Cd / mm ² , preferably at least 80Cd / mm ² .

[0047] The control unit can form an electronic device capable of controlling the electroluminescent elements. The control unit can be an integrated circuit. An integrated circuit, also called an electronic chip, is an electronic component reproducing one or more electronic functions and being able to integrate several types of basic electronic components, for example in a reduced volume (i.e. on a small plate). This makes the circuit easy to set up. The integrated circuit can be for example an ASIC or an ASSP. An ASIC (acronym for “Application-Specific Integrated Circuit”) is an integrated circuit developed for at least one specific application (ie for a customer). An ASIC is therefore a specialized integrated circuit (microelectronics). In general, it bundles a large number of unique or tailor-made features. An ASSP (acronym for "Application Specifies Standard Product") is an integrated electronic circuit (microelectronics) combining a large number of functions to satisfy a generally standardized application. An ASIC is designed for a more particular (specific) need than an ASSP. The monolithic matrices are supplied with electricity via the electronic device, which is itself supplied with electricity using, for example, at least one connector connecting it to a source of electricity. The source of electricity can be internal or external to the device according to the invention. The electronic device supplies the light source with electricity. The electronic device is thus able to control the light source.

According to the invention, the light source preferably comprises at least one monolithic matrix whose electroluminescent elements project from a common substrate. This arrangement of elements can result from a growth on the substrate from which they have grown respectively, or from any other production method, for example by transfer of the elements by transfer techniques. Different arrangements of light-emitting elements can meet this definition of a monolithic matrix, provided that the light-emitting elements have one of their main dimensions of elongation substantially perpendicular to a common substrate and the spacing between the pixels, formed by a or more electroluminescent elements grouped together electrically, is small compared to the spacings imposed in known arrangements of generally square flat chips soldered to a printed circuit board.

In particular, the light source according to one aspect of the invention may comprise a plurality of electroluminescent elements distinct from each other and which are grown individually from the substrate, by being electrically connected to be selectively activatable, the if necessary by sub-assemblies within which rods can be activated simultaneously.

According to an embodiment not shown, the monolithic matrix comprises a plurality of electroluminescent elements, of submillimeter dimensions, or even less than 10 miti, which are arranged projecting from a substrate so as to form rods of section especially hexagonal. The electroluminescent rods extend parallel to the optical axis of the light module when the light source is in position in the housing.

These electroluminescent rods are grouped together, in particular by electrical connections specific to each assembly, in a plurality of selectively activatable portions. The electroluminescent rods originate on a first face of a substrate. Each electroluminescent rod, here formed by using gallium nitride (GaN), extends perpendicularly, or substantially perpendicularly, projecting from the substrate, here made from silicon, other materials such as silicon carbide being able to be used without go beyond the context of the invention. For example, the electroluminescent rods could be made from an alloy of aluminum nitride and gallium nitride (AIGaN), or from an alloy of aluminum phosphides, indium and gallium (AlInGaP). Each electroluminescent rod extends along an axis elongation defining its height, the base of each rod being disposed in a plane of the upper face of the substrate.

According to another embodiment not shown, the monolithic matrix may include light-emitting elements formed by layers of epitaxial light-emitting elements, in particular a first layer of n-doped GaN and a second layer of p-doped GaN, on a substrate single, for example made of silicon carbide, and which is cut (by grinding and / or ablation) to form a plurality of pixels respectively originating from the same substrate. The result of such a design is a plurality of electroluminescent blocks all coming from the same substrate and electrically connected to be selectively activatable from each other.

In an exemplary embodiment according to this other embodiment, the substrate of the monolithic matrix may have a thickness of between 100 μm and 800 μm, in particular equal to 200 μm; each block may have a length and a width, each being between 50 μm and 500 μm, preferably between 100 μm and 200 μm. In a variant, the length and the width are equal. The height of each block is less than 500 μm, preferably less than 300 μm. Finally, the exit surface of each block can be made via the substrate on the side opposite to the epitaxy. The separation distance of the contiguous pixels may be less than 1 μm, in particular less than 500 μm, and it is preferably less than 200 μm.

According to another embodiment not shown, both with electroluminescent rods extending respectively projecting from the same substrate, as described above, with electroluminescent blocks obtained by cutting superimposed electroluminescent layers on the same substrate, the monolithic matrix may further comprise a layer of a polymer material in which the electroluminescent elements are at least partially embedded. The layer can thus extend over the entire extent of the substrate or only around a determined group of electroluminescent elements. The polymer material, which may in particular be based on silicone, creates a protective layer which makes it possible to protect the electroluminescent elements without hindering the diffusion of light rays. In addition, it is possible to integrate in this layer of polymer material means for converting wavelength, and for example phosphors, capable of absorbing at least part of the rays emitted by one of the elements and of converting at least part of said absorbed excitation light into emission light having a length wave different from that of the excitation light. It is equally possible to provide that the phosphors are embedded in the mass of the polymer material, or that they are placed on the surface of the layer of this polymer material. The phosphors can also be deposited under vacuum on the semiconductor chips, without the polymer layer. The light source may further include a coating of reflective material to deflect the light rays to the output surfaces of the pixelated source.

The light-emitting elements of submillimeter dimensions define in a plane, substantially parallel to the substrate, a determined exit surface. It is understood that the shape of this exit surface is defined according to the number and the arrangement of the electroluminescent elements which compose it. It is thus possible to define a substantially rectangular shape of the emission surface, it being understood that the latter can vary and take any shape without departing from the context of the invention.

It is not excluded that the selectively activatable emissive elements are secondary light sources.

[0057] Figure 1 shows an example of a projection obtained by the invention. In the illustrated case, this is a projection of a checkerboard (1 pixel in 4 is lit: 1 in two in each row on and every other row on, a row on being shifted by one pixel horizontally by compared to the immediately neighboring lit rows, so that one out of four pixels is lit in each column) in a plane perpendicular to the optical axis, at a predetermined distance from the optical device, here at 25 m. The beam resulting from the projection is segmented in the sense that, in the projection plane, it is formed of a plurality of images each produced by the light of an emissive element. Reference S shows one of these images.

The projection obtained has an image distribution corresponding to that of the pixels of the source. In this example, the outline is substantially rectangular, in the case of a source also having a rectangular shape. The long dimension is preferably oriented horizontally. The height of the images corresponds to the vertical. The ratio between these two dimensions can be of the order of 3, for example 3.15; it can be derived from the ratio of two blocks of juxtaposed LEDs, for example each having a ratio of 1.6.

This projection is centered on the optical axis of the device, the intersection of which with the projection plane is represented by the point O.

According to one possibility, the angular sector covered by the field of view of the beam produced is greater than 25 °, or even greater than or equal to 30 °.

We immediately note a stronger brightness of the images near the point O, and a decrease in this brightness as we move away from the latter. At the same time, the outline of the images is narrower near point O and enlarges, being less sharp, outwards.

[0062] For example, the source 1 pixel array may have a rectangular shape having an aspect ratio of at least 3 between its largest dimension and its smallest dimension. In this elongated arrangement, cleverly arranged in the horizontal direction, the distortion effect will be accentuated in this horizontal direction, and of less importance, if not negligible, in the other, vertical direction. The mark provided in Figure 1 shows the width dimension of the images under the letter "I" and the height dimension of the images under the letter "h".

FIG. 2 shows the evolution of the dimension (given in mm) in width of the images of the activated pixels (here one in two in the example given of a checkerboard as in FIG. 1) and of their light intensity, as we move away from point O horizontally to the right in this illustration. Note that the images are narrower at the origin of the abscissa and that the width gradually increases. At the same time, the light intensity (given on an arbitrary ordinate scale) decreases, revealing the spread of light over a larger image area.

In order to use conventional sources, it is advantageous that the emissive elements all have the same shape and the same dimensions, in height and in width. However, this choice is not limiting. In particular, in order to at least partially compensate for the effects of the distortion in the vertical direction, the height dimension of the emissive elements can be progressively reduced as one moves away from the optical axis. This dimensional reduction can follow a function equivalent, but inverse, to that of the distortion function produced by the optical device.

Preferably, the optical device makes it possible to adjust the growth function of the size of the images to obtain the desired light intensity modulation and the required visual field.

For any point of the source matrix, it is possible to calculate from knowledge of the projection optics the spot formed in the projection plane and the centroid of this image task. We can therefore connect each point on the source matrix to a point of the image (the centroid mentioned previously) or, which is equivalent when the distance from the projection plane tends to infinity, to one direction (two angles) in the projected field. Moreover, if we imagine an arbitrarily small rectangular emitter around the point of the source considered, we can calculate the projected image and define a magnification (ratio of the sizes of the sides of the projected image to the sizes of the sides of the hypothetical source ). If we now consider only points located along a line parallel to the largest side of the source matrix and meeting the optical axis of the projection system, we can determine two quantities in R for each point: the position of the centroid along the projection of the line of sources considered (and therefore at infinity a projection angle, in practice an angle in a horizontal plane) and the corresponding magnification. From these calculations which can be carried out at any point of the line considered on the matrix of sources, we deduce a gamma function from R to R connecting an angle (in practice horizontal) in the field projected to a magnification. This function obviously applies to the calculation of the size of the source pixel images. Its first derivative gives the increase in the magnification of said pixels in the field. For an optic produced according to the invention, the derivative of the increase (second derivative of gamma) is zero for an angle 0 corresponding to a point on the optical axis of the projection optic.

An embodiment of the projection system is provided with reference to Figures 3A and 3B. FIG. 3A shows from right to left a light source 1 which may be of the type mentioned above, in particular in the form of a matrix of emissive elements, a first optical unit, called the input unit 2 and a second unit, said output unit 3. The source 1 is advantageously centered on the optical axis of the optical device.

It is understood that the unit 2 is configured to receive light from the source 1 through its input face 21. The light leaving the unit 2 enters the unit 3, preferably directly. It comes out through the outlet face of unit 3 with a view to being projected, preferably directly, into the space surrounding the vehicle.

[0069] In a preferred embodiment, the input unit 2 comprises, and preferably consists of, a lens. Advantageously, this is the part that provides the distortion. In the illustrated case, it is a meniscus lens, having an entry face 21 with a concave portion. Optionally, the entrance face can be completely flat. The opposite face, forming the exit diopter, is convex and has a high curvature, which induces a distortion, in particular by the strong inclination with respect to the normal to the surface of certain rays in incidence on the exit diopter, in particular towards the periphery of the optically useful surface of the lens. It can be a spherical face, which avoids having to resort to complex and therefore expensive shapes.

Advantageously, the ratio between the radius of curvature of the exit face and the useful opening (also called in English clear aperture) of the latter (radius of the cross section of the base of the exit face) is less at 1, 175. Typically, it is possible to choose a lens radius and a radius of curvature of the output diopter of very similar dimensions, which ensures the largest possible radius of curvature.

Advantageously, it is this diopter which has the greatest curvature in the entire optical device. Preferably, this curvature is at least 1.25 times greater than all the other curvatures of the optical device.

It is desirable to use a high index material for the lens of unit 2. Preferably, the refractive index will be greater than 1.7. The Abbe number is preferably chosen from the range between 40 and 55. In particular, the glasses from the company Schott® AG bearing the references LAK10, LAK21 and LAK43 or the glasses indicated as equivalent to these from others. glassmakers give satisfaction. FIG. 3A then provides an exemplary embodiment of the output unit 3. It is desirable for the optical power of this unit to be less than the optical power of the unit 2, with a focal length greater than for the unit 2. Advantageously, the ratio between the optical power of the input unit 2 and the output unit 3 is greater than 1, 6 and / or less than 2.2. It is also advantageous for the chromatism of unit 3 to be inverted (the relative position of the focal points corresponding to the plurality of wavelengths of light is opposite to that of the case of a converging refractive lens). This is possibly the case for the two units 2 and 3 of the system of FIG. 3A. A simple description of this chromaticism inversion amounts to saying that for unit 3 for example, the “red” focus is closer to the lens 31 than the “blue” focus and that the “green” focus is located between the two. . Unit 3 thus makes it possible to compensate for the chromatic aberrations generated by unit 2 while maintaining high optical power for the projection system. Indeed, high-performance automotive lighting, performing in particular the functions of non-dazzling high beam and dynamic cornering lighting (ADB functions), requires the widest possible illuminated field; in other words, it is desirable that the image of the matrix of sources be as large as possible. Moreover, the cost of the source matrices increases with their surface; in other words, it is desirable that the source matrix be as small as possible. As a result, the focal length of the projection optics must be small in order to have a large illuminated field and a small source. It is therefore necessary that the projection optics have a high power. The optic of the invention achieves this condition by combining two converging elements of lower power than the total power required. The first optical element - the unit 2- of a device according to the invention is an element with high distortion and large aperture (it is necessary to capture as much luminous flux as possible since one seeks to illuminate a large field with a small source - which therefore has a restricted luminous flux). By limiting this optical element to a reasonable number of lenses (one, possibly two, preferably spherical), it is impossible to simultaneously optimize the chromatism. We therefore realize as the second element - unit 3 - a convergent system (sharing of the power with the first element) with the chromatism reversed compared to that of the first element, in order to perform a chromatism correction (essential to avoid completely undesirable colorings in the projected image). The first element -unit 2- behaving like a simple converging lens, the second element -unit 3- must be convergent and of inverted chromatism.

In the case of Figure 3A, this unit 3 comprises three lenses successively following the path of the rays. Going up the path of the rays: the third lens 33 is there in a plane convex shape, but it could also be, for example, biconvex. It can be formed from Crown glass. It is followed by a biconcave lens 32 preferably of Flint glass or polycarbonate. Optionally, a stopper, limiting the useful opening of the lens 32, can be positioned on its entry face, that directed towards the light source 1. Then, a lens 31 is in the example of biconvex shape; it can be Crown glass.

It will be noted that it is advantageous to alternate Flint type glasses and Crown type glasses in this case, as in the following embodiments.

FIG. 3B provides an example of light ray paths according to this embodiment, from different pixels of the source 1.

Figures 4A and 4B give a variant of the situation described above. In fact, the input unit 2 is not modified in its general form, but the output unit 3 has two lenses this time. The lens 31 is a biconvex converging lens, advantageously made of Crown glass with a high refractive index. Typically, glass with a refractive index of 1.6 and an Abbe number of 60 can be used.

[0078] The other lens 32 is a divergent meniscus lens also exhibiting a high refractive index, preferably Flint glass. The concave face of lens 32 forms its entry face and is directed towards the source 1 side. Typically, a material having a refractive index of 1.95 with an Abbe number of 20 can be used.

The corresponding ray path is shown in FIG. 4B.

In the situation shown in Figures 5A and 5B, the output unit 3 comprises four lenses. Thus, unit 3 is organized there in two pairs of doublets. A first pair comprises a biconvex lens 31 and a planar concave lens 32, the concavity of this lens being oriented towards the lens 31. The second pair of lenses successively comprises a planar concave lens 33 and a planar convex lens 34, the concavity of the lens 33 being oriented towards the lens 34. The assembly typically has the structure of two Fraunhofer doublets placed back to back (the converging lens is crown glass and the diverging one is flint); however, the doublets are not chromatically corrected here like true Fraunhofer doublets. It will be noted that in this situation, the lens 2 is located in the immediate vicinity of the unit 3.

FIG. 5B provides an example of ray path for this configuration.

Another solution for the second optical unit 3 is the use of a diffractive optical element, for example in the form of a converging blaze grating, as shown in FIG. 6. In fact, the converging diffractive elements have a chromatism. axial inverse with respect to the converging refractive elements.

The association of a light source 1 described above with an optical device comprising the units 2 and 3 provides a resulting segmented beam exhibiting the distortion corresponding to FIG. 1. Preferably, the system further comprises a control unit the selective activation of the light-emitting elements in a different way, taking into account the variable size of the images of these elements. We understand that to cover an area of predetermined size, more pixels will be needed in the vicinity of the center corresponding to point O than in the periphery.

Optionally, the magnification ratio between each image around the optical axis and an image of an emissive element at the level of the optical axis can be determined for each emissive element, so as to have a base of data used for the calculation making it possible to approximate the surface of a zone to be lit or extinguished in relation to the number (and to the identity) of the emissive elements necessary and sufficient to cover this zone. The system may include computer processing means, in particular with a processor and a non-volatile memory for the storage of computer program instructions allowing the operations of determining the emissive elements to be activated and the emissive elements to be deactivated according to the beam. to train.

The invention is not limited to the embodiments described above and extends to all the embodiments covered by the claims.

Claims

1. A light system comprising a pixelized light source (1) having a plurality of selectively activatable emissive elements and each having a rectangular shape with a height dimension and a width dimension, the width dimension being the same for all of the lights. emissive elements, and an optical device having an optical axis and configured to project an image (S) of each of the emissive elements, characterized in that the optical device is configured so that the images (S) have a dimension in width increasing in such a way nonlinear as one moves away from the optical axis.

2. System according to the preceding claim, wherein the derivative of a function of the increase in the width dimension of an image (S) with respect to the angular position of the image (S) along an axis parallel to the width dimension of the total illuminated field is equal to zero at the level of the optical axis.

3. System according to any one of the preceding claims, wherein the optical device is configured so that the images (S) have an increasing width dimension in a non-linear manner as one moves away from the image. optical axis for at least one peripheral group of images (S).

4. System according to any one of the preceding claims, wherein the optical device comprises an input optical unit (2) receiving light from the plurality of emissive elements and an output optical unit (3) receiving light. the light coming from the input optical unit (2) and projecting the images (S) of each of the emissive elements.

5. System according to the preceding claim, wherein the input optical unit (2) comprises a converging lens which has on its output face a radius of curvature / useful opening radius ratio of less than 1.175.

6. System according to any one of the two preceding claims, in which the converging lens is made of a material having a refractive index greater than 1.7.

7. System according to any one of claims 4 to 6, wherein the output optical unit (3) is convergent and has inverted chromatism.

A system according to any one of claims 4 to 7, wherein the focal length of the output optical unit (3) is greater than the focal length of the input optical unit (2).

9. A system according to any one of claims 4 to 8, wherein the output optical unit (3) comprises at least two lenses.

10. A system according to any one of claims 4 and 8, wherein the output optical unit (3) comprises a diffractive optical element.

11. A system according to any preceding claim, wherein the plurality of emissive elements form a rectangular matrix, the long dimension of the rectangular matrix being directed in the width dimension.

12. The system of the preceding claim, wherein the width dimension is directed along the horizon line.

13. System according to any one of the preceding claims, in which the emissive elements have an identical dimension in height.

14. System according to any one of the preceding claims, comprising a unit for controlling the activation of each of the emissive elements, configured to produce at least one dark zone in a projected beam by deactivation of a group of adjacent emissive elements. , the control unit being configured to determine the number of emissive elements of the group of adjacent emissive elements corresponding to the dark zone as a function of the width dimension of the emissive elements.