FR3109203A1 - An optical device for a headlight having the appearance of a flat light guide. - Google Patents

Abstract

The invention relates to an optical device (DO) comprising a translucent screen (EC) extending between an input face (FE) and an output face (FS), having a privileged axis (AP) so that a parallel light beam illuminating the entry face (FE) with an incidence along the privileged axis (AP) is refracted into a parallel beam propagating in the screen (EC) directly to the exit face (FS), the device (DO) comprising an optical reflector (RL), remote from the screen (EC), arranged to reflect a light beam from at least one light source in a parallel beam propagating in a direction parallel to the axis privileged (AP) to illuminate the entrance face (FE), a cross section of the screen (EC) along the privileged axis (AP) having a first dimension, measured along this axis, greater than a second dimension orthogonal to the first dimension at the exit face (FS). (Figure 3)

Description

Optical device for a headlight having the appearance of a flat light guide.

The technical field relates to optical devices comprising optical reflectors.

The invention also relates to the headlights of motor vehicles equipped with such devices.

In the field of automotive-type vehicles, the lighting or signaling devices must ensure several photometric functions, such as the regulatory reversing and rear fog lamp functions. More and more frequently, their role is also to provide a light signature specific to each vehicle and, to this end, automobile manufacturers are seeking to make the shapes of the light surfaces offered by such devices more complex and in particular to refine luminous surfaces. However, the complexification of the luminous surfaces should not degrade the photometric properties of these surfaces.

In this context, it is increasingly common to use flat-type light guides, commonly referred to as flat guides. These flat guides have dimensions, in particular thicknesses, such that they make it possible to obtain headlights with relatively thin luminous surfaces, which offers many possibilities in terms of design.

A flat guide has an entrance face and an exit face and is designed to transfer photons illuminating the entrance face to said exit face in order to deliver them outside. Most of the light rays illuminating the entrance face of the flat guide undergo several internal reflections, at the level of the edges of the flat guide, to travel along the flat guide to the exit face. However, each internal reflection does not reflect 100% of the light energy and each internal reflection increases the optical path, thus increasing the light energy absorbed by the flat guide. Finally, the multiple internal reflections cause significant light scattering by the exit face since the light rays emitted by the exit face have multiple directions, resulting from the internal reflections. The loss of light output is generally compensated by using an increased number of light sources or by using more powerful LEDs.

The phenomenon of diffuse lighting is, most of the time, appreciated by designers for aesthetic reasons but can prove to be problematic for the implementation of certain photometric functions which require light emission with a privileged direction.

As just mentioned, the use of flat guides appreciated for the possibilities of offering fine luminous surfaces have drawbacks, in particular insufficient optical yields and significant diffusion, which make them difficult to match with certain photometric functions.

Also, there is a need to improve the optical solutions implemented to perform very directive photometric functions, which require light emission along a specific axis. In particular, it is desirable to improve the visual appearance and the dimensions of the luminous surfaces ensuring certain photometric functions, such as the reversing function or rear fog lamp, while guaranteeing compliance with regulatory requirements.

The present invention aims to propose a solution to the problems exposed and to improve the known devices.

To this end, the present invention proposes an optical device for a motor vehicle, comprising a translucent screen extending between an input face and an output face, having a privileged axis so that a parallel light beam illuminating the front face entry with an incidence along the privileged axis is refracted into a parallel beam propagating in the screen directly as far as the exit face, the device further comprising an optical reflector, remote from the screen, positioned and arranged to reflect a light beam from at least one light source into a parallel beam propagating in a direction parallel to the preferred axis to illuminate the input face, each light source being offset from the preferred axis, a cross section of the screen along the privileged axis having a first dimension, measured along this axis, greater than a second dimension orthogonal to the first dimension at the level of the front face tie.

The invention also relates to a vehicle headlight characterized in that it comprises at least one device according to the invention, associated with at least one light source.

Thus, an optical device according to the invention makes it possible to obtain a headlight according to the invention by associating it with at least one light source. The light source illuminating the optical reflector generates a parallel light beam which illuminates the entrance face of the screen with an incidence parallel to the privileged axis. By construction of the screen, a parallel light beam illuminating said entrance face along the preferred axis is refracted into a parallel beam propagating directly to the exit face, i.e. without internal reflection. By avoiding internal reflections, the optical device makes it possible to avoid the losses of light energy usually observed in a flat guide and therefore has an increased optical efficiency compared to a system using a flat guide. Without internal reflection, the parallel beam propagating in the screen between the entry and exit faces makes it possible to control the dispersion of the beam emerging from the exit face.

The reflector designed to convert a beam coming from a light source delocalized from the preferred axis allows a conventional arrangement in a vehicle headlight where said sources are not positioned in the axis of the headlight but on a plate substantially orthogonal to the face Release.

The first and second dimensions of the screen make it possible to obtain an exit face having the appearance of an exit face obtained by the use of a flat guide. Indeed, the length along the optical path traveled by the beam between the entry and exit faces is greater than the thickness of the screen measured along a direction orthogonal to the direction of the preferred axis in a cutting plane longitudinal. Thus, the dimensions of the screen are similar to the usual dimensions of a flat guide.

Advantageously, the screen consists of a flat light guide having such a privileged axis.

According to one embodiment of the invention, the reflector has at least one reflective surface forming a paraboloid portion whose focal point is the position for a light source. Thus, such a reflector makes it possible, by positioning a light source at the focus of the parabola of revolution, to obtain a parallel beam, the reflecting surface having the optical properties of a parabola of revolution.

According to one possibility of the invention, the reflector comprises a plurality of reflective surfaces. Thus, the optical device makes it possible to illuminate the entry face of the screen with a plurality of light sources, making it possible to obtain an exit face that is sufficiently bright to meet the regulatory requirements of a photometric function.

Advantageously, the reflector is metallized.

According to one embodiment, the cross section along the preferred axis is of substantially rectangular shape.

According to a preferred mode of the invention, the entry face is planar and substantially orthogonal to the privileged axis.

Advantageously, the exit face and/or the entry face have prisms and/or beading. The use of a prism on the entrance face and/or the exit face makes it possible to compensate for a curve in the screen.

According to one possibility, the device is designed to perform a photometric function.

Finally, the invention relates to a vehicle characterized in that it comprises at least one headlight according to the invention.

The invention will be better understood on reading the detailed description which follows, given solely by way of non-limiting example and made with reference to the appended drawings in which:

FIG. 1 represents a perspective view of a vehicle headlight according to the invention, fitted with an optical device according to the invention;

Figure 2 shows a cross-sectional view of the headlight of Figure 1 along the axis AA of Figure 1;

Figure 3 shows a detail view of the reflector and the screen of the device of Figure 2.

In these figures, the same references are used to designate the same elements.

A headlight P for an automobile according to the invention, illustrated in FIGS. 1 and 2, comprises a box BO defining a mounting cavity CA closed by a transparent lens GL. In the mounting cavity CA the headlight P comprises at least one light source SL, in this case a plurality of light sources SL such as, for example, a plurality of light-emitting diodes (abbreviated as LEDs), mounted on an electronic plate PL , illustrated in FIG. 2. In the box BO is also installed an optical device DO according to the invention, illustrated in FIGS. 1 to 3, intended to perform a photometric function.

The device DO comprises an optical reflector RL, illustrated in figures 2 and 3, as well as a translucent screen EC visible in figures 1 to 3.

The screen EC extends between an entry face FE, illustrated in FIGS. 2 and 3, and an exit face FS, illustrated in FIGS. 1 to 3. The screen EC is made of translucent material, more particularly in molded or injected plastic. The screen EC is made of colorless or colored material depending on the needs of the photometric function targeted by the use of the device DO.

The screen EC has a privileged axis AP, illustrated in FIG. 2, so that a parallel light beam FP1 illuminating the entrance face FE along this privileged axis AP is refracted into a parallel beam FP2 propagating in the screen EC directly to the exit face FS.

As illustrated in FIG. 2, the screen EC has a cross-section along the privileged axis AP having a first dimension L, measured along this axis, greater than a second dimension H orthogonal to the first dimension L at the level of the face of FS output. Thus, along the privileged axis AP, the length corresponding to the first dimension L is greater than the thickness corresponding to the second dimension H. In particular, as illustrated in FIG. 2, the screen EC has a cross section of the shape substantially rectangular, delimited, on the one hand, by the input FE and output FS faces and, on the other hand, by two parallel faces called upper FH and lower FI.

As illustrated in Figure 3, the screen EC forms a block B similar to the shape of a flat guide GP, visible in Figure 2. The input faces FE and output FS are substantially flat and parallel to each other. The entry faces FE and exit FS are orthogonal to the privileged axis AP. For example, the upper face FH is substantially flat while the lower face FI is curved so that the thickness of the block, measured between the upper faces FH and lower faces FI is variable.

The block B has a maximum thickness corresponding to the second dimension H (measured between the upper faces FH and lower FI) limited with respect to the other dimensions, in particular to the first dimension L, measured between the entrance faces FE and the exit faces FS.

As illustrated in FIG. 1, the output face FS has beading BI in order to provide optical effects to the light passing through the output face FS.

The optical reflector RL, illustrated in FIGS. 2 and 3, is formed from a one-piece piece PM made for example of injected plastic material. The one-piece piece PM is dimensioned to extend at least partly opposite the entrance face FE, along an axis BB, illustrated in FIG. 3. The reflector RL has a plurality of reflective surfaces SR each forming an optical mirror. To this end, the reflective surfaces SR are, for example, covered with a reflective layer, such as a layer of metal. Alternatively, the RL reflector is completely metallized.

The reflector RL is distant from the screen EC.

The reflector RL is designed to reflect a light beam FL1 from a light source SL, shown in Figure 2, into a parallel beam FP1. In the headlight P, the reflector RL is positioned and oriented so that the parallel beam FP1 illuminates the entrance face FE following an incidence parallel to the privileged axis AP of the screen EC. The reflector RL is adapted to the light source SL offset from the preferred axis AP. To this end, each reflective surface SR forms a portion of paraboloid whose focal point corresponds to the position of a light source SL.

Once positioned in the headlight P, the preferred axis AP of the device DO corresponds to a front/rear longitudinal axis of a vehicle likely to be fitted with the headlight P.

The reflector RL advantageously has fixing means such as a fixing zone ZF making it possible to fix the reflector RL in the headlight P, for example, by screwing or quarter-turn fixing.

The headlight P further comprises a mask MO, illustrated in figure 2, designed to prevent a light ray from crossing the transparent lens GL without having crossed the screen EC. The mask MO is positioned between the reflector RL and the lens GL. The screen EC crosses the mask MO using an opening OV (figure 2) made in the mask MO, the perimeter of the opening OV of the mask MO matching the contour of the screen EC. In the example illustrated in Figure 2, the flat guide GP also passes through the mask MO, in the same way as the screen EC.

Thus, when the light sources SL of the headlight P according to the invention emit light, they illuminate each reflecting surface SR. The light sources SL being positioned at the respective foci of each reflecting surface SR, the light reflected by said reflecting surfaces form parallel beams FP1 which illuminate the entrance face FE of the screen EC along its preferred axis AP. Each parallel beam FP1 is thus refracted by the entrance face FE in the screen EC into a parallel beam FP2 propagating as far as the exit face FS. Depending on the shape of the output face FS, the light emitted by the latter is a plurality of parallel light beams compatible with a directive photometric function. The perception of an observer looking at the exit face FS emitting light is comparable, visible through the glass GL, presents the visual appearance of a surface of a flat guide GP but with an increased light intensity.

The device DO according to the invention therefore makes it possible to obtain directional photometric functions having an appearance similar to a system implementing a flat guide GP with, however, improved optical efficiency.

The invention is not limited to the embodiment of the optical device described above, only by way of example, but other embodiments can be designed by those skilled in the art without departing from the framework and the scope. of the present invention.

Claims (10)

Optical device (DO) for a motor vehicle, comprising a translucent screen (EC) extending between an entry face (FE) and an exit face (FS), having a privileged axis (AP) so that a beam parallel light (FP1) illuminating the entrance face (FE) with an incidence along the privileged axis (AP) is refracted into a parallel beam (FP2) propagating in the screen (EC) directly up to the face of output (FS), the device (DO) further comprising an optical reflector (RL), remote from the screen (EC), positioned and arranged to reflect a light beam (FL1) coming from at least one light source (SL ) in a parallel beam (FP1) propagating in a direction parallel to the preferred axis (AP) to illuminate the entrance face (FE), each light source (SL) being offset from the preferred axis (AP), a cross-section of the screen (EC) along the favored axis (AP) having a first dimension (L), measured along this axis, greater than a second th dimension (H) orthogonal to the first dimension (L) at the exit face (FS). Optical device (DO) according to Claim 1, characterized in that the reflector (RO) has at least one reflecting surface (SR) forming a portion of a paraboloid whose focal point is the position for a light source (SL). Optical device (DO) according to Claim 1 or 2, characterized in that the reflector (RO) comprises a plurality of reflective surfaces (SR). Optical device (DO) according to one of Claims 1 to 3, characterized in that the reflector (RL) is metallised. Optical device (DO) according to one of Claims 1 to 4, characterized in that the cross section along the preferred axis (AP) is of substantially rectangular shape. Optical device (DO) according to one of Claims 1 to 5, characterized in that the input face (FE) is flat and substantially orthogonal to the preferred axis (AP). Optical device (DO) according to one of Claims 1 to 6, characterized in that the exit face (FS) and/or the entrance face (FE) have prisms and/or beads (BI). Optical device (DO) according to one of Claims 1 to 7, characterized in that the device (DO) is designed to perform a photometric function. Vehicle headlight (P) characterized in that it comprises at least one device (DO) according to one of Claims 1 to 8, associated with at least one light source (SL). vehicle characterized in that it includes at least one headlight (P) according to claim 9.