FR3099543A1 - LUMINOUS DEVICE OF DIRECTION CHANGE INDICATOR WITH CONTROLLED CAUSTIC-GENERATING SURFACE FORMING A PATTERN ON A TARGET SURFACE - Google Patents

Abstract

The present invention relates to a luminous device (1) indicating the change of direction of a vehicle comprising: an optical element (10) having a pattern on a target surface. a caustic generating surface (12) controlled so as to propagate a pattern over a useful interval, a mounting part (2) on which is intended to be mounted a beam generator (3) of rays incident on said generating surface, 'optical element being arranged so that the propagated pattern is projected onto a target surface, visible from outside the light device and located in the useful interval. Figure for the abstract - Figure 1

Description

DIRECTION CHANGE INDICATOR LIGHTING DEVICE WITH CONTROLLED CAUSTIC GENERATING SURFACE FORMING A PATTERN ON A TARGET SURFACE

The present invention relates to the field of luminous devices emitting patterns on a given surface, in particular on the road and more particularly luminous devices indicating a change in the direction of movement of a vehicle.

Document WO2016184721A1 discloses vehicle light devices comprising two plates of transparent material whose front and rear diopters each have a surface forming a matrix of optical lenses. Between the two plates, a cover is arranged. The mask and optical lenses of each array are plated together and arranged to together form a given light pattern on a target surface.

It is known from document EP2543542A1 a vehicle with a turn signal system comprising a turn signal installed in a headlight housing, which comprises a first lamp unit configured to emit a light forming a flashing pattern and a second lamp unit configured to emit a patterning light on the road to indicate the change in the direction of travel, wherein the second lamp unit comprises a plurality of light source portions having a linear arrangement disposed adjacent to an outer edge of the headlight housing.

However, such a design is complex and relatively expensive.

The technical problem which the invention aims to solve is therefore to simplify a luminous device indicating a change in direction of a vehicle making it possible to produce luminous patterns in order to project them onto a surface of movement of the vehicle, in particular the road.

To solve this problem, the applicant had the idea of using caustics.

Caustics are an optical phenomenon that has been known for a long time. They are, for example, observable at the bottom of a swimming pool lit by the sun. They form fluctuating patterns there, generally forming a mesh of more concentrated and therefore brighter lines of light, with darker areas between the meshes. These dark lines and areas are due to the different fluctuations of the water surface. These fluctuations locally form orientation variations around the overall flat shape of the water surface. Thus, depending on the local variations encountered, the rays will be deflected differently, some approaching and forming more concentrated and therefore brighter lines, and others deviating and forming dark areas. The mesh varies according to the agitation of the surface.

In recent years, researchers have been interested in methods to use this phenomenon on fixed surfaces with local variations, so as to generate complex caustics of controlled shape. In particular, they have developed different methods for calculating refracting surfaces formed of a transparent material with a distribution and arrangement of local variations, so that when these refracting surfaces are illuminated, these allow, from a given light source, to form a pattern on a screen.

In some works, this pattern, called the target pattern, physically corresponds to a distorted image of the pattern formed in relief by the local variations, called the object pattern.

The applicant realized that such surfaces could be used in vehicle direction change indicator light devices.

Thus, the invention relates to luminous devices indicating a change of direction of a vehicle, in which a controlled caustic-generating surface deflects the light rays from a light source, this generating surface having local variations arranged in such a way to form a determined pattern on a given surface outside the vehicle, in particular the surface on which it is moving, generally the road.

To this end, a first object of the invention is a vehicle direction change indicator light device comprising:
an optical element having a controlled caustic-generating surface, this generating surface being a reflecting or refracting surface, extending according to a given overall shape and having local variations of shape around this given overall shape, these local variations being distributed over the the whole of said generating surface so that they give the whole of the generating surface a relief forming an object pattern, these different local variations being arranged in such a way that the majority of the said generating surface is smooth and so as to that for a beam of rays incident on the whole of said generating surface, these rays having a given distribution, said generating surface deflects the rays according to different orientations according to the local variations which they encounter, thus forming a deflected beam propagating an identifiable propagated pattern over a useful interval extending upstream of and at least up to a finite given optimal propagation distance, this propagated pattern corresponding to a distorted projection of the object pattern,
a mounting part on which a ray beam generator is intended to be mounted according to the given distribution, so that the rays are incident on said generating surface,
the optical element being arranged in such a way that the propagated pattern can be projected onto a target surface, which is visible from outside the luminous device and which is located inside the useful range and/or at a distance substantially equal to said optimum distance.

By “identifiable”, we mean that we recognize the pattern as the one that would be observed at the optimal distance.

The best result is observed when the target surface is located at a distance substantially equal to said optimal distance.

In the application, “smooth” means a zone derivable at any point, in other words a zone devoid of protruding or re-entrant edges. A portion is smooth when the set of points forming it obeys this definition.

Thus, it is possible to mount a light beam generator, such as a light source or a light source and a set of one or more optical elements, making it possible to generate rays according to a given distribution, this mounting being done so that these rays are incident on the optical element. Therefore, the ignition of the light beam generator will allow the generation of the propagated pattern, which will propagate until it encounters a surface, in particular the target surface on which the vehicle is moving.

The projection of the propagated pattern onto the targeted surface forms the target pattern.

These beam generators can be simple. The optical element is enough in itself to modify the beam to make a pattern.

Furthermore, this pattern propagates over a given finite distance, namely over the useful interval comprising the distance where the sharpness is optimum, namely the optimum propagation distance, which allows a certain freedom over the distance between the element optics and the target surface. The direction change indicator luminous device according to the invention is simpler to assemble. This optimum propagation distance, hereinafter referred to as optimum distance, is the distance at which the majority of the deflected rays and forming the target pattern intersect and therefore at which this pattern has the best sharpness. The generating surface can thus be designed easily with respect to this definition.

Moreover, unlike the solutions with masks, in the light device according to this first object, most, if not all, of the light rays encountering the generating surface are deflected and form the target pattern. The luminosity of the target pattern is therefore greater with the luminous device indicating a change in direction of a vehicle according to this first object.

The luminous device according to the invention may optionally comprise one or more of the following characteristics:

• the given distribution is substantially such that for any transverse plane, in particular perpendicular, to the direction of propagation, at a given point of this plane, the incident ray(s) at this point come(s) from a single direction;
• depending on the given distribution, the rays are substantially parallel or substantially distributed in an emission cone;
• the distribution given corresponds to that of a light-emitting diode;
• the light device comprises the ray beam generator according to the given distribution; the light device is thus ready to emit;
• the generating surface comprises at least one smooth portion whose surface represents the majority of the generating surface, the transition from one local variation to another being smooth inside this smooth portion;
• the majority of the generating surface is arranged so that each local variation deflects the rays so as to form one and only one portion of the target pattern which is distinct from the portions of the target pattern formed by the other local variations, and for the majority of the target pattern, each potion of the target pattern receives the light rays of one and only one local variation; there is thus, for this majority of the generating surface and this majority of the target pattern, a one-to-one relationship between each smooth portion of the object pattern and each portion of the target pattern without marked discontinuity of luminosity; this simplifies the calculation and therefore the production of the generating surface;
• the entire generating surface is smooth, the transition from one local variation to another being smooth; this also makes it possible to less distort the image of the parts upstream of the optical element; it is thus possible either to distinguish these parts through the optical element, when the optical element is a transparent element refracting the rays emitted by said beam generator, or by observing the image of these parts on the optical element , when the latter is a reflector reflecting the rays emitted by said beam generator; this thus makes it possible to work on the style of the beam generator;
• the entire generating surface is arranged in such a way that each local variation deflects the rays so as to form one and only one portion of the target pattern which is distinct from the portions of the target pattern formed by the other local variations, and for the entire target pattern, each potion of the target pattern receives the light rays of one and only one local variation; there is thus a one-to-one relation between the totality of the object pattern and each potion of the target pattern without a marked discontinuity in luminosity; this simplifies the calculation and therefore the production of the generating surface;
• the passage between certain local variations is delimited by an edge; such a passage creates a discontinuity in the slope variations on the generating surface; this makes it possible to create very dark or even black areas and very bright and narrow areas, such as clean writing;
• the local variations are arranged in such a way that the rays of the deflected beam do not intersect until said optimum distance; thus the target pattern remains sharp on a target surface positioned upstream of or at the optimum distance;
• according to the previous paragraph, there may also be a minimum distance below which the pattern is not formed; in this case, the pattern is clear in an interval, corresponding to the useful interval going from this minimum distance to at least up to the optimum distance; for example, this interval represents more than half of the optimal distance;
• the local variations have a tangent to the given overall shape forming an angle between −60 and 60 degrees, in particular between −30 and 30 degrees; this allows good transmission of light rays;
• each local variation has, at each of its points, an amplitude defined as the distance between the local variation and said global shape along the normal at a given point of the global shape;
• the maximum amplitude of each local variation is within an interval of between 0.001 millimeter and 1 millimeter; this gives a smoother appearance to the generating surface;
• along an overall direction of propagation of the beam, the optical element is circumscribed in a rectangle, one side of which extending along a direction parallel to this direction of propagation is at least four times greater, in particular six times greater than that of the amplitude of each local variation with respect to the global shape given at the level of this local variation;
• along an overall direction of propagation of the beam, the generating surface is circumscribed in a rectangle, one side of which extending along a direction parallel to this direction of propagation is at least ten times greater, in particular thirty times, than that of one of the sides of a beam generator light source;
• the beam generator comprises a light source, in particular a light-emitting diode; the light-emitting diodes are particularly suitable for being coupled to a controlled generator surface;
• the beam generator comprises a light-emitting diode emitting its rays generally according to a cone; for example, the generator may be formed of only one or more light-emitting diodes
• the beam generator comprises a light source, in particular a light-emitting diode, and optics arranged with the light source so as to generate a beam of substantially parallel rays;
• the optical element comprises a reflective surface of which at least a portion is formed by the generating surface; in other words, the generating surface is reflective; in particular, the optical element may be a mask, in particular metallized; in this case the generating surface can form a portion of the surface of this mask; it is thus possible to confer another function on the mask, than that of masking certain parts of the light device;
• the optical element is made of a transparent material and is arranged with the beam generator so as to form the deflected beam by refraction of the rays emitted by the beam generator; this allows a simple arrangement;
• according to the previous paragraph, the optical element comprises an input face for said rays arranged opposite the beam generator and an output face for these rays arranged opposite said input face, the generating surface being formed on the entry face or on the exit face;
• according to the preceding paragraph, the optical element comprises two generating surfaces, a first generating surface being formed on the input face and a second generating surface being formed on the output face, these two generating surfaces being arranged together so as to forming the target pattern and ensuring its propagation over the optimal distance; this makes it possible to leave more freedom in the slopes to be conferred on the local variations; moreover, it can also make it possible to obtain better contrast, or to increase the depth of field, or even tend towards an infinite depth of field;
• the light device comprises a case and a cover glass of the case through which the rays emitted by the light device emerge, the cover glass forming the optical element, the generating surface being formed on the surface of a portion of the glass closure, the deflected beam being formed by refraction of the rays emitted by the beam generator; this thus makes it possible to propagate the target pattern outside the vehicle and without adding a new part; for example, the light device can be arranged so that, once mounted on the vehicle, the distance between the generating surface and the road in the direction of propagation of the target pattern, corresponds to the useful interval or is close to the optimal distance, according to a given orientation of the vehicle; this thus makes it possible to project the light pattern onto the road; this distance between the closing glass and/or the generating surface can be equal to half the optimum distance, when the road is horizontal; in the latter case, this makes it possible to have a clear visible pattern whatever the orientation of the vehicle, uphill, downhill, when braking or when accelerating;

The vehicle direction change indicator light device according to the invention can be a dedicated device or, for example, be integrated into:

- a road lighting device, in particular a front headlamp, in particular emitting a dipped beam and/or a long-range headlamp, or even a fog lamp;

- a signaling device, in particular a rear position light, a daytime running light (or DRL, for "Day Running Light" ), a direction indicator, a brake light, a raised stop light, a rear fog light, a back.

The invention also relates to a vehicle comprising a luminous device indicating a change of direction of said vehicle according to the invention, in particular connected to the power supply of the vehicle.

The terms "upstream" and "downstream" refer to the direction of propagation of the light rays in the light device and outside of it.

Unless otherwise specified, the terms “front”, “rear”, “lower”, “upper”, “side”, “transverse” refer to the direction of light emission out of the corresponding turn indicator light device.

Other characteristics and advantages of the invention will appear on reading the detailed description of the non-limiting examples which follow, for the understanding of which reference will be made to the appended drawings, among which:

• [Fig. 1] is a schematic view of a beam generator and an optical element of a light device according to a first embodiment of the invention;
• [Fig. 2] is an enlarged view of a portion of Figure 1;
• [Fig. 3] is a schematic view of a beam generator and an optical element of a light device according to a second embodiment of the invention;
• [Fig. 4] schematically represents the propagation of a target pattern by a beam generator and an optical element of a light device according to the invention;
• [Fig. 5] schematically represents a target pattern formed by a beam generator and an optical element of a light device according to the invention;
• [Fig. 6] schematically represents the object pattern of the generating surface making it possible to generate the target pattern of FIG. 5;
• [Fig. 7] represents a first example of a light device according to the invention;
• [Fig. 8] schematizes a third embodiment according to the invention;
• [Fig. 9a], [Fig. 9b], [Fig. 9c], [Fig. 9d], [Fig. 9th], [Fig. 9f] schematize the different steps for calculating the generating surface.

Figures 1 and 2 illustrate an example of a vehicle direction change indicator light device 1 according to the invention. These figures also make it possible to illustrate the general principle of the invention.

According to the invention, the luminous device 1 indicator of a change of direction of a vehicle comprises an optical element 10 having a generating surface 12 of controlled caustic. This generating surface 12 can be a reflecting surface or a refracting surface, as illustrated in FIGS. 1 and 2. This optical element is referred to below as the caustic generator 10.

The generating surface 12 extends according to a given overall shape 13, represented by the vertical dotted line in Figures 1 and 2.

More particularly, in the embodiment of FIG. 1, the caustic generator 10 is a transparent plate having an entry face 11 and an exit face. The input face 11 is arranged opposite a beam generator 3 of light rays so as to receive the rays r ₁ , r ₂ , r ₃ emitted by the beam generator 3. The output face is arranged to receive the rays r ₁ , r ₂ , r ₃ refracted by the entrance face 11.

As in the example illustrated, the output face can be formed, in particular entirely, by the generating surface 12.

In general, the generating surface 12 has local variations in shape around the overall given shape 13. These local variations are distributed over the whole of the generating surface 12, so that they give the whole of the generating surface 12 a relief forming an object pattern.

For example, as illustrated in Figures 1 and 2, these local variations form hollows and bumps on the exit face of said caustic generator 10.

In general, these different local variations are arranged so that the majority of said generating surface 12 is smooth. Thus for the majority of the generating surface 12, this surface is differentiable at any point. In other words, on smooth areas, it has no protruding or re-entrant edges.

In general, these different local variations are arranged so that for the beam of rays r ₁ , r ₂ , r ₃ incident on the whole of said generating surface 12, these rays r ₁ , r ₂ , r ₃ having a known given distribution, the generating surface 12 deflects the rays r ₁ , r ₂ , r ₃ according to different orientations according to the local variations which they encounter, thus forming a deflected beam propagating a light pattern over a useful interval extending upstream of and at least up to a finite given optimal propagation distance, called optimal distance, this propagated pattern corresponding to a distorted projection of the object pattern.

This generating surface 12, with its local variations, corresponds to a controlled caustic generating surface.

Indeed, these local variations create local convergences and divergences of the rays. As these variations are local, a majority of rays diverge or approach each other without crossing before a certain distance. Thus, in the same way that the surface of a swimming pool crossed by the rays of the sun creates a luminous pattern propagating and projecting itself on the bottom of a swimming pool, the generating surface 12 creates a luminous pattern which propagates, the pattern spread.

In the case of a swimming pool, this pattern generally propagates over a distance of 3 meters. The propagated pattern is therefore observable by projecting onto the bottom of the swimming pool, whether the bottom is at 1.5 m or at 2 m. This background therefore forms the screen on which the caustic forming the propagated pattern is observable.

In the case of a controlled caustic-generating surface, as according to the invention, depending on the local variations, the light pattern propagates at least over a given optimum distance. Beyond this optimum distance D _p , the rays of the deflected beam intersect.

In the context of the invention, and as can be seen in the block diagram in FIG. 4, the optimum distance D _p is finite. If a screen is interposed at an intermediate distance D ₁ or at another intermediate distance D ₂ , which are less than the optimum distance D _p , the same more or less distorted pattern will be observed.

It should be noted that this optimal distance D _p is that at which the pattern will have the best sharpness. The generating surface can thus be designed with respect to this definition.

There may also be a minimum distance D₀below which the pattern is not formed. This minimum distance D₀is generally quite low. This minimum distance D₀can be a few centimeters or even a few millimeters depending on the application, such as an application to a automobile light device. In the latter case it may be less than 1 centimeter (cm).

Also, the pattern is not lost as soon as the rays cross but afterwards, at a greater maximum distance (not shown). However, it is easier to design the generating surface with respect to the crossing distance of the rays, which is defined more precisely than the distance at which the pattern is considered to be lost. In the present application, this crossing distance of the rays is therefore called optimum propagation distance or optimum distance.

In other words, the useful interval includes a downstream portion, going from the optimal distance D_pat this maximum distance, and an upstream portion, going from the minimum distance D₀to the optimal distance D_p. The observable pattern at the optimal distance D_p,if a screen is placed there, remains identifiable within these upstream and downstream portions.

In general, in the invention, this downstream portion can be of a different value from that of the upstream portion. In particular, it may be less than it by more than half.

For example, in a floodlight with a diffusing portion of closing glass, with an optimal distance D _p of 20 cm, a minimum distance D ₀ of 1 cm, the value of the upstream portion would be 19 cm, and the downstream portion could be less than 9.5 cm.

In particular, said caustic generator 10 and its local variations are arranged so that the propagated pattern is projected onto a target surface, which forms the screen, to form a light pattern there, called the target pattern. This target surface is visible from outside the luminous device 1 and is located at a distance included in the useful interval. The target surface can be around or at the optimal distance D_p,which improves the sharpness. The target surface corresponds to the surface of movement of the vehicle, in particular a portion of the road.

In general, to manufacture the generating surface 12, the latter is in particular calculated taking into account the target pattern that it is desired to display, the shape of the target surface and its arrangement with respect to the light rays forming the target pattern, as well as the given distribution of the rays r ₁ , r ₂ , r ₃ on emission by the beam generator 3, in particular their incidence on said caustic generator 10.

According to the invention, the given distribution may correspond to substantially parallel rays r ₁ , r ₂ , r _{3 ,} as illustrated in FIG. 3, or, in particular, as illustrated in FIGS. 1 and 2, substantially distributed globally according to a cone of emission 14, in particular as with a divergent light source, such as an LED. This makes it possible to more simply establish the angle of incidence of the rays on said caustic generator 10, thus simplifying the calculation of the generating surface 12.

For this, it is possible to consider that the given distribution is such that for any plane perpendicular to the direction of propagation, at a given point of this plane, the incident ray(s) at this point come(nen )t from a single direction. Indeed, the distribution of the rays emitted by an LED corresponds substantially to such a given distribution.

To simplify the calculation, it is possible to discretize the surface into numerous elementary surfaces and to assimilate the latter to the points mentioned in the preceding paragraph.

The luminous device 1 indicating a change of direction of a vehicle can be delivered without the beam generator 3, but has a mounting part 2 on which it is intended to be mounted, so that the rays r ₁ , r ₂ , r ₃ are incident on said generating surface 12.

In particular, this mounting part 2 and the beam generator 3 can be arranged so that, on mounting, the beam emitted by the beam generator 3 has a given overall direction with respect to said caustic generator 10. Thus, it does not there is no need for the assembly to adjust this orientation so that it corresponds to the layout allowing to generate the target pattern.

It should be noted that these caustic-generating surfaces do not require great precision as to the positioning of the beam generator 3. The assembly is therefore simplified.

In the example shown in figure 1, the beam generator 3 is mounted on the mounting part 2.

The beam generator 3 can, as here, be formed by a light-emitting diode or LED. In FIG. 1, a light-emitting element 4 of the LED is schematized with, attached to it, a protective dome 5 transparent.

The target surface is a surface outside the vehicle, such as the road.

The methods for calculating this generating surface 12 can follow the following process, an example of which is illustrated in FIGS. 9a to 9f:

- in a step, called upstream step E1, illustrated in figure 9a, establish the relationship defining the angle of incidence of the rays r ₁ , r ₂ , r _3, r ₄ , r ₅ and their distribution at each point of the shape given overall shape 13, taking into account the given distribution of the rays r ₁ , r ₂ , r ₃ , making it possible in other words to also define the luminosity of each point at the level of the given overall shape 13 on said caustic generator 10, called point object p ₁ , p ₂ , p ₃ , p _4, p ₅ ,

- in a step, called downstream step E2, which can be carried out before, after or at the same time as said upstream step E1, defining the light distribution on the target surface making it possible to obtain the target pattern, and therefore defining the brightness of each point of the target surface 19, called target point p′ ₁ , p′ ₂ , p′ ₃ , p′ ₄ ,

- then, in a correlation step E3, illustrated in FIG. 9b, establishing a relationship between each object point p ₁ , p ₂ , p ₃ , p _{4 ,} p ₅ and each target point p′ ₁ , p′ ₂ , p′ ₃ , p′ ₄ , in particular so that each target point p′ ₁ , p′ ₂ , p′ ₃ , p′ ₄ receiving light is associated with a single or a set of object points p ₁ , p ₂ , p ₃ , p _4, p ₅ making it possible to obtain the luminosity required at these points for the formation of the pattern,

- then, in a step E4/E5 of orientation of the local variations, illustrated in FIGS. 9c to 9f, as a function of the target points and the object points associated by the relationship established in the correlation step E3, determining the orientation of the local variations to be applied to the global shape so that the rays r ₁ , r ₂ , r _{3 ,} r ₄ , r ₅ incident on the object points p ₁ , p ₂ , p ₃ , p _4, p ₅ are deviated so as to have the orientation enabling them to reach the target points p′ ₁ , p′ ₂ , p′ ₃ , p′ ₄ associated by this relation.

The upstream step E1 takes into account the distribution of the rays on their arrival at the given overall shape 13. The simplest case, not shown, is that of an optical element 10, such as that illustrated in FIGS. 1 and 9a, formed of a transparent plate whose entry face 11 and the given overall shape 13 of the generating surface 12 are flat, and with a beam generator 3, such as that of FIG. 3, emitting parallel rays.

In this simple case, the beam generator 3 and said caustic generator 10 are arranged so that the rays are perpendicular to the entry face 11. These rays are therefore not deflected before meeting the exit surface on which the generating surface is formed.

The embodiment of Figures 1 and 2 and of Figures 9a to 9f is an intermediate case where the rays are distributed in an initial cone 14 at the exit of the beam generator 3, then refracted by the flat entry face, thus remaining inscribed in a cone, allowing easy determination of the angle of incidence of the rays r ₁ , r ₂ , r _3, r ₄ , r ₅ with the overall shape 13, and therefore easy determination of the angle of incidence rays r ₁ , r ₂ , r _{3 ,} r ₄ , r ₅ with the generating surface 12.

The embodiment of FIG. 3 is another intermediate case where the distribution of the rays r ₁ , r ₂ , r ₃ is initially simpler, since they are parallel at the output of the beam generator 3. On the other hand, they are then refracted differently by the entrance face 11 because the latter is curved, for example cylindrical with a circular or elliptical section. However, this curvature being defined, it makes it possible to determine the orientation of the rays r ₁ , r ₂ , r ₃ on their arrival at the given overall shape 13 of the generating surface 12, which is also curved.

In the example illustrated in FIG. 3, the optical element is a curved transparent plate, of which the entry face 11 and the overall shape 13 of the generating surface 12 are cylindrical.

So as to have parallel rays, the beam generator 3 can comprise a light source 6, such as a light-emitting diode, and a collimating lens 7 whose diopters make it possible to orient the rays parallel.

However, more complicated cases can be considered, with:

- rays distributed in an emission cone,

- a curved entry surface, in particular cylindrical, and

- a generating surface of given curved overall shape.

It is also possible to envisage other given distributions of the rays.

Concerning the downstream step E2, the simplest case is when the target surface 19 is flat and perpendicular to the global direction of emission of the rays on arrival at the level of the global shape 13 of the generating surface 12 to be calculated. The target pattern then corresponds to the propagated pattern.

In more complex cases, it is necessary to take into account the orientation of the planar target surface, presenting an angle with the global direction of emission of the rays on arrival at the level of the generating surface. Nevertheless, such a determination remains simple. It is more complicated, but feasible, when the target surface is not flat. It is then necessary to take account of its shape, in particular to define it by an equation to determine the light distribution, in order to be able to observe the target pattern in projection. In all these more complex cases, the propagated pattern, if it is defined according to a plane perpendicular to the direction of propagation thereof, differs from the target pattern.

Then, different methods can be used to perform the correlation step E3 between the incident rays on the overall shape 13 of the generating surface 12 and the light distribution on the target surface 19.

As explained previously, this correlation step makes it possible to determine which object points p ₁ , p ₂ , p ₃ , p _{4 ,} p ₅ of the given overall shape 13 are associated with which target points p′ ₁ , p′ ₂ , p′ ₃ , p' ₄ of the target surface 19.

Thanks to the upstream step E1, the orientation of the rays r ₁ , r ₂ , r _{3 ,} r ₄ , r ₅ on arrival at the given overall shape 13 of the generating surface 12 is known. to the correlation between target points p' ₁ , p' ₂ , p' ₃ , p' ₄ and object points p ₁ , p ₂ , p ₃ , p _{4 ,} p ₅ , the orientation of the rays r ₁ , r is determined ₂ , r _{3 ,} r ₄ , r ₅ starting from this given global shape 13 to join the object points p ₁ , p ₂ , p ₃ , p _{4 ,} p ₅ to the target points p′ ₁ , p′ ₂ , p′ ₃ , p' ₄ with which they are correlated.

This therefore makes it possible to carry out the orientation step E4/E5, by calculating the variation to be attributed to the exit surface with respect to this given overall shape 13 at any point thereof, which makes it possible to define the generating surface 12.

Once this calculation has been carried out, it is therefore observed, depending on the amplitudes of the local variations, that the generating surface 12 is at a greater or lesser distance from the given overall shape 13. To refine the calculation of the generating surface 12, it is therefore possible repeat the upstream and downstream steps as well as the definition step, considering the arrival of the rays and their departure with respect to the shape of the generating surface obtained previously and no longer with respect to the overall shape given. The precision of this surface and therefore the sharpness of the image will be improved with the number of iterations. Furthermore, this also makes it possible to smooth the generating surface.

To carry out the orientation step, it is possible to use Descartes' laws, also known as Snell's laws in some English-speaking countries, or even under the name of Snell-Descartes' laws.

Thus, in a sub-step E4, illustrated in FIGS. 9c and 9e, for an object point p ₁ , p ₂ , p ₃ , p _{4 ,} p ₅ of the given overall shape 13 or of the generating surface calculated previously, with the direction of arrival and the direction of departure of the rays r ₁ , r ₂ , r _3, r ₄ , r ₅ , we can determine the tangent and normal of the exit surface at this point so that the latter deflects each ray r ₁ , r ₂ , r _{3 ,} r ₄ , r ₅ incident on arrival along the corresponding direction of refraction.

By determining, the set of normals , also called fields of the normals, in a sub-step E5, illustrated in FIGS. 9d and 9f, the generating surface 12 having these normals is determined.

FIGS. 9c and 9d illustrate the realization of these two sub-steps in an enlargement at the level of the object points p ₁ , p ₂ , p ₃ , not referenced in FIGS. 9c and 9d for greater clarity.

FIGS. 9e and 9f illustrate the realization of these two sub-steps in an enlargement at the level of the object points p _{4 ,} p ₅ not referenced in FIGS. 9e and 9f for greater clarity.

In FIG. 2, one can observe the local variations of the generating surface 12 with respect to the given overall shape 13, flat in this example. These local variations correspond to changes in slope, defined by the normal and/or the tangent to the generating surface 12 at the level of these local variations. As a result, this generating surface 12 includes deviations from the overall shape 13 and forms hollows and bumps.

For clarity the normals and tangents have only been represented here for three points of the generating surface 12, the normal and/or the tangent are however calculated for all the points.

The amplitude of a local variation can in this application be defined as the distance between the local variation and said global shape 13 according to the normal at a given point of the global shape 13.

If the overall shape is flat, as in Figures 1 and 2, any point of the given overall shape can be defined by a dimension along a single direction z perpendicular to this overall shape 13.

We observe, in FIG. 2, a minimum amplitude a ₁ , by negative convention because located upstream of the generating surface 12, and a maximum amplitude a ₂ downstream of the generating surface 12, by positive convention.

It should be noted that in the process illustrated, it is possible to discretize the surface into numerous elementary surfaces and to assimilate the latter to the points mentioned p ₁ , p ₂ , p ₃ , p _4, p _5, p' ₁ , p' ₂ , p′ ₃ , p′ ₄ .

Figure 5 illustrates the propagated pattern 16, as it will be seen on a flat screen, perpendicular to the direction of propagation and at a distance equal to or close to the propagation distance. If the target surface is also flat and oriented so, then this propagated pattern 16 will also be the target pattern 16' seen in Figure 5. Otherwise, it will be distorted.

The generating surface 12 having made it possible to produce this propagated pattern 16 is illustrated in FIG. 6. Due to the reliefs formed on this surface 12, it is possible to observe the object pattern 15 formed by this relief and therefore the local variations. This object pattern 15, symbolized in figure 6, corresponds to a distorted form of the propagated pattern 16.

In a case where it would also be desirable for the pattern in FIG. 5 to be the target pattern 16′ observed by a driver or a third party observing the roadway, the target pattern being formed by rays grazing relative to the roadway since, for example, coming of a headlight, a rear light or a direction indicator, the propagated pattern should then be distorted with respect to the target pattern, to observe the star on the road as it is represented in figure 5.

According to the invention, as in FIGS. 1 and 2, the generating surface 12 can be arranged, and therefore calculated, so that, for the majority of the generating surface 12, namely on smooth portions representing the majority of this surface, the transition from one local variation to another is smooth. This is notably the case of the portion illustrated in FIG. 2. In a case where, for the calculation, the local variations are not considered as points but as a small area of the generating surface, in particular an infinitesimal area, the generating surface 12 can also be arranged so that, for these smooth portions, the local variations are smooth.

In particular, one of the smooth portions may have a surface representing the majority of the generating surface.

A first example of a calculation method can be used to calculate this generative surface 12. This is the method disclosed in the document Yue et al. [1]. This document indicates in particular the various steps for constructing the generating surface 12 from a given example, in particular for establishing the relationship between the points of the generating surface 12 and those of the target surface.

This first example of a method makes it possible to obtain a totally smooth generating surface 12. The transition from one local variation to another is smooth.

To establish the relation of the correlation step, in particular as in this first method, it is fixed as a condition to establish a bijection between the object points and the target points. Thus, the entire generating surface 12 is arranged so that:

- each local variation deflects the incident light rays so as to form one and only one portion of the target pattern 16' which is distinct from the portions of the target pattern formed by the other local variations, and

- for the entire target pattern, each portion of the target pattern receives the light rays from one and only one local variation.

This method allows good brightness gradients and good resolution. It can for example be used to produce the generating surface 12 of FIG. 1.

According to other methods, to improve the contrast and have darker areas and areas with maximum brightness, it is possible to arrange the local variations so that the generating surface 12 has one or more edges.

Depending on the case, the generating surface 12 comprises:

- at least one edge delimiting portions of the generating surface with different orientations so as to generate a divergence such that certain areas of the target pattern receive almost no rays, or even none at all, thus forming dark areas, and/or

- at least one edge delimiting portions of the generating surface with different orientations so as to generate a convergence such that certain zones of the target pattern receive the rays of several local variations and/or of several portions of this generating surface.

This makes it possible in particular to create patterns with luminous lines or very clear writing.

For this, it is possible for example to use a second calculation method to calculate the generating surface 12, disclosed in the document Schwartzburg et al. [2] .

In this second method, no bijection constraint is used in the correlation step. This method is more complex but makes it possible to obtain a higher contrast, namely a ratio between the light zone and the dark zone. This method indeed makes it possible to obtain darker zones than those of the method of Yue and Al , mentioned previously. Thus, it is possible with this second method to obtain more marked demarcations between dark zone and light zone. The portions outside the edges are smooth, the transition from one local variation to the other being smooth there.

For example, in Figures 9a to 9f, the method used does not impose a bijection constraint to establish the target pattern. At certain locations, several object points p _{4 ,} p ₅ correspond to a single target point p′ ₄ . As a result, the generating surface 12 has a slope variation discontinuity, corresponding to an outgoing edge 18 on the generating surface 12, and therefore re-entrant in the direction of the incident rays. The local variations on either side of this edge 18 make it possible to concentrate the rays r4, r5 on a line of the target surface, for example to form a clear intense line.

Apart from this edge 18, in particular above and below, the correlation step E3 resulted, without however having constrained it, in a one-to-one relationship between the corresponding object points p ₁ , p ₂ , p ₃ and the corresponding target points p′ ₁ , p′ ₂ , p′ ₃ .

Whatever the method used, each point of the generating surface 12 is therefore associated with an amplitude which corresponds to a deviation from the global shape 13, this amplitude being defined according to a direction parallel to the normal to the global shape 13 at this point. .

For example, as illustrated in FIGS. 1 and 3, a plane comprising the global direction of the beam of incident rays is considered. Considering in this plane, the rectangle 17, in which the caustic generator 10 is circumscribed, this rectangle 17 can have a side at least four times greater, in particular six times greater than that of the amplitude of each local variation with respect to the global shape given 13 at the level of this local variation, therefore greater than six times the maximum amplitude.

Moreover, the local variations can present a tangent forming an angle α with the overall shape given between -60 and 60 degrees, in particular between -30 and 30 degrees.

By combining these slope and amplitude conditions, optimum results are obtained, in particular in terms of contrast and sharpness, allowing in particular propagation of the propagated pattern over the useful interval, in particular at the optimum distance D _p .

It should be noted that the smaller the size of the light source 4, 6 of the beam generator 3 is relative to the generating surface 12, the closer the projected pattern is to the desired pattern used for the construction of the generating surface. For example, the side of the rectangle 17 in which the caustic generator 10 is circumscribed can be at least ten times greater, in particular thirty times, than that of one side of this light source 3, 6, in particular when this source is a light emitting diode.

The two embodiments of FIGS. 1 to 3 relate to caustic generators 10 operating by refraction.

Here the generating surface 12 is formed on an optical element 10 specially dedicated for this purpose. However, it can also be formed on elements having other functions, such as a closing glass of the luminous device or of an automobile lighting and/or signaling device into which the luminous device according to the invention is integrated, an optical lens, a mask.

In the application, the term “mask” denotes the trim intended to mask certain elements, such as cables, the bottom of the case. It is also called "bezel" in English.

Furthermore, FIGS. 1 to 3 illustrate cases where the generating surface 12 is on the output face of the caustic generator 10. However, this is not limiting and in general, the optical element may have a surface generator on the entry face and/or on the exit face.

FIG. 8 illustrates a third embodiment, according to which the optical element 10' or caustic generator 10' operates by reflection.

The caustic generator 10′ is here a mirror whose reflecting surface forms the generating surface 12′, presenting local variations around its planar overall shape 13′.

This 10' mirror can have one or more edges. Here, there is a re-entrant edge 18', namely forming the bottom of a hollow, delimiting portions of surfaces with an orientation facing each other, these portions thus allowing create an intense luminous line of particular shape on the target pattern, not shown.

The same construction methods can be applied to this reflective 12' generating surface, taking into account during the different stages that it is a reflection and not a refraction.

In such a case, the upstream step is simplified because the radii r₁, r₂, r₃, r₄arrive directly on the generating surface 12 according to the given distribution and also leave there directly.

Figure 7 illustrates a first example of a light device according to the invention. In the case illustrated, a vehicle 20 with longitudinal axis X is equipped with two luminous devices according to the invention, which are here integrated respectively into a right rear light 21 and a left rear light 22.

For example, these taillights 21, 22 each include a case and a corresponding case closing glass. Each closing lens comprises a portion whose interface between the lens and the exterior forms the generating surface. Each of these generating surfaces receives part of the light rays from a light source of the corresponding rear light 21, 22. It would also be possible to provide a light source specially dedicated to this generating surface.

The generating surface of the right rear light 21 is arranged to generate a target pattern 23 on the road forming a pattern composed of three triangles, here indicating to following vehicles a change of direction to the right, with respect to the direction of movement of the vehicle illustrated by the X arrow.

Figure 7 being an aerial view, this pattern is stretched but will be perceived by following vehicles as less stretched. The object pattern, not shown, formed by the relief of the corresponding generating surface presents a distorted form of this target pattern composed of a set of three triangles.

In this example, it is understood that, depending on the direction of propagation, the distance of the pattern between the generating surface and the target surface, namely the road, will vary depending on the attitude of the vehicle 20, for example if it is loaded or not. Here, the generating surface is arranged so that when the attitude of the vehicle 20 is horizontal on a horizontal road, the optimum distance D _p given is greater, for example twice, than the distance between the generating surface and the road according to the direction of propagation of the propagated pattern. This makes it possible to have a net visible target pattern, whatever the orientation of the vehicle 20, in particular of its attitude. The target pattern therefore remains visible uphill, downhill, in the event of braking or in the event of acceleration, and whatever its load.

In this example, the generating surface of the right rear light 21 receives the light rays from the light source making it possible to generate a direction indicator signal.

Note that the lights could also be built according to the principle illustrated in Figures 1 and 3. In this case, instead of the generating surface being formed on the closing glass 9, closing the box 8, this is, as described above formed on a transparent plate 10, specially designed to present the generating surface.

In the present invention, the target pattern forms a logo, a pictogram, a geometric pattern or a set of several logos, pictograms or geometric patterns as well as their combination, such as for example a pictogram associated with one or more geometric patterns. Advantageously, a geometric pattern whose shape is well recognized, such as chevrons, triangles or discs, will be chosen. Advantageously, the pictogram represents a straight or curved arrow.

List of references

[1] Yonghao Yue, Kei Iwasaki, Bing-Yu Chen, Yoshinori Dobashi, Tomoyuki Nishita. Poisson-Based Continuous Surface Generation for Goal-Based Caustics, ACM Transactions on Graphics , Vol. 31, No. 3, Article 31 (May 2014).

[2] Yuliy Schwartzburg, Romain Testuz, Andrea Tagliasacchi, Mark Pauly. High-contrast Computational Caustic Design, ACM Transactions on Graphics (Proceedings of ACM SIGGRAPH 2014), Vol. 33, Issue 4, Article No. 74 (July 2014)

Claims (12)

Luminous device (1) direction change indicator of a vehicle comprising:
an optical element (10; 10') having a controlled caustic generating surface (12; 12'), this generating surface being a reflecting or refracting surface, extending according to a given overall shape (13; 13') and having local variations in shape around this given overall shape, these local variations being distributed over the whole of said generating surface so that they give the whole of the generating surface a relief forming an object pattern (15), these different local variations being arranged so that the majority of said generating surface is smooth and so that for a beam of incident rays (r ₁ , r ₂ , r ₃ ) on the whole of said generating surface, these rays having a given distribution, said generating surface deflects the rays according to different orientations according to the local variations which they encounter, thus forming a deflected beam propagating an identifiable propagated pattern (16) over a useful interval extending upstream from and at least up to an optimum distance (D _p ) of finite given propagation, this propagated pattern corresponding to a distorted form of the object pattern,
a mounting part (2) on which is intended to be mounted a beam generator (3) of rays according to the given distribution, so that the rays are incident on said generating surface,
the optical element being arranged in such a way that the propagated pattern is projected onto a target surface, which is visible from outside the luminous device and which is located within the useful interval and/or at a distance (D ₁ , D ₂ ) substantially equal to said optimum distance. Luminous device (1) according to claim 1, in which the given distribution is substantially such that for any plane transverse to the direction of propagation, at a given point of this plane, the ray or rays (r1, r2, r3 ) incident(s) at this point come(s) from a single direction. Luminous device (1) according to any one of the preceding claims, in which the given distribution corresponds to that of a light-emitting diode. Luminous device (1) according to any one of the preceding claims, in which the luminous device comprises the beam generator (3) of rays (r1, r2, r3) according to the given distribution. Luminous device (1) according to any one of the preceding claims, in which the generating surface comprises at least one smooth portion whose surface represents the majority of the generating surface (12; 12'), the transition from a local variation to the other being smooth inside this smooth portion. Luminous device (1) according to claim 5, in which the entire generating surface (12) is smooth, the transition from one local variation to the other being smooth Luminous device (1) according to claim 5, in which the passage between certain local variations is formed by a ridge (18, 18') Luminous device (1) according to any one of the preceding claims, in which the beam generator (3) comprises a light-emitting diode (4,5) Luminous device (1) according to any one of the preceding claims, in which the beam generator (3) comprises a light source (6) and an optic (7) arranged with the light source so as to generate a beam of rays (r ₁ , r ₂ , r ₃ ) substantially parallel. Luminous device (1) according to any one of the preceding claims, in which the optical element (10') comprises a reflecting surface of which at least a portion is formed by the generating surface (12'). A luminous device (1) according to claim 10, wherein the optical element (10') is a mask. Luminous device (1) according to any one of claims 1 to 9, comprising a case and a case closing glass through which the light rays emitted by the luminous device emerge, the closing glass forming the optical element, the generating surface being formed on the surface of a portion of the closing glass, the deflected beam being formed by refraction of the rays emitted by the beam generator.