Light guide for an optical device, notably for lighting and/or signaling

A light guide for an optical device, notably for lighting and/or signaling, comprising:

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to French Application No. 1261426 filed Nov. 29, 2012.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a light guide for an optical device, notably a lighting or signaling or interior lighting device.

2. Description of the Related Art

It is known practice to provide the lighting and/or signaling devices with a light guide in the form of a non-planar sheet and light-emitting diodes whose light rays are guided by the light guide to the output of the device. A light beam is thus created using a light guide whose appearance when switched on is curved.

In order to direct the light beam emitted by the guide in certain directions, it is known practice to provide such guides with collimation subassemblies suitable for receiving light emitted by a light-emitting diode and for directing a part of this light toward the output of the device.

Now, the form of such subassemblies has to be adapted to the curvature of the sheet, for example by bending the subassemblies.

This adaptation leads to the drawback of degrading the appearance of the light guide when switched on, which can appear uneven, even discontinuous along the curved profile.

In addition, such curved subassemblies are complicated to design.

SUMMARY OF THE INVENTION

One aim of the invention is to produce a light guide that makes it possible to mitigate these drawbacks.

Thus, the subject of the invention is a light guide for an optical device, notably for lighting and/or signaling, comprising:at least one light output portion having a top face and a bottom face linked together by a light output rim,at least one collimation subassembly suitable for receiving light emitted by a light source and for directing at least a part of this light toward the light output portion, the collimation subassembly having a top face and a bottom face linked together by a rim, anda coupling portion coupling the light output portion to the subassembly, the coupling portion having a top face and a bottom face,

wherein the bottom and top faces of the subassembly extend substantially in mutually parallel planes, and in that the top face of the coupling portion and at least one of the top face of the collimation subassembly and of the top face of the light output portion meet at an edge.

By virtue of the invention, it is possible to do away with any deformation of the collimation subassembly and consequently to retain an optimum distribution of the light rays toward the light output rim and therefore enhance the uniformity of the light beam reaching the output face.

Furthermore, because of the flatness of the top and bottom faces of the subassembly, the guide according to the invention can be produced simply.

According to one embodiment of the invention, when a light ray arrives on the bottom face of the coupling portion with a given direction of incidence, the top and bottom faces of the coupling portion are arranged in such a way as to reflect this ray, notably by total internal reflection, toward the light output portion in a direction of reflection substantially parallel to the given direction of incidence.

“Direction of incidence” should be understood to mean the angle of incidence of the ray on the bottom face of the coupling portion and “direction of reflection” should be understood to mean the angle of reflection of the ray on the top face of the coupling portion. By virtue of this feature, the light rays that are propagated in the guide pass from the collimation subassembly to the output portion by retaining their direction, despite the curvature of the sheet. In this way, the uniformity of the light beam reaching the output face is enhanced.

As a variant, when a light ray arrives on the top face of the coupling portion with a given direction of incidence, the top and bottom faces of the coupling portion are arranged in such a way as to reflect this ray, notably by total internal reflection, toward the light output portion in a direction of reflection substantially parallel to the given direction of incidence.

Advantageously, the top face of the coupling portion and the top face of the collimation subassembly meet at a first edge, and the top face of the coupling portion and the top face of the output portion meet at a second edge.

If necessary, the first edge defines the apex of an angle formed by the top face of the coupling portion and the top face of the collimation subassembly. Preferentially, this angle is between 130° and 160°, is even equal to 135°.

The second edge defines the apex of an angle formed by the top face of the coupling portion and the top face of the output portion. Preferentially, this angle is between 130° and 160°, is even equal to 135°.

Advantageously, the first edge forms a straight segment.

Also advantageously, the top face of the coupling portion is planar.

According to one feature of the invention, the bottom face of the coupling portion and at least one of the bottom face of the collimation subassembly and of the bottom face of the light output portion meet at an edge.

Advantageously, the bottom face of the coupling portion and the bottom face of the collimation subassembly meet at a third edge, and the bottom face of the coupling portion and the bottom face of the output portion meet at a fourth edge.

If necessary, the third edge defines the apex of an angle formed by the bottom face of the coupling portion and the bottom face of the collimation subassembly. Preferentially, this angle is between 130° and 160°, is even equal to 135°.

The fourth edge defines the apex of an angle formed by the bottom face of the coupling portion and the bottom face of the output portion. Preferentially, this angle is between 130° and 160°, is even equal to 135°.

Advantageously, the third edge forms a straight segment.

Also advantageously, the bottom face of the coupling portion is planar.

Preferentially, the top and bottom faces of the coupling portion are mutually parallel.

According to an advantageous feature of the invention, the top face of the coupling portion exactly covers the bottom face of the coupling portion. Advantageously, the bottom face of the coupling portion is, over its entire surface, facing the top face of the coupling portion. For example, provision can be made for the first edge and the third edge to be included in one and the same plane at right angles to the collimation subassembly. Provision can also be made for the second edge and the fourth edge to be included in one and the same cylinder defined by a translational generatrix on a directrix, the generatrix being a straight line at right angles to the collimation subassembly and the directrix being the second edge.

In another embodiment of the invention, the top face of the coupling portion is offset relative to the bottom face of the coupling portion. The first edge and the third edge are included in one and the same plane inclined relative to the collimation subassembly. The second edge and the fourth edge are included in one and the same cylinder defined by a translational generatrix on a directrix, the generatrix being a straight line secant to the collimation subassembly and the directrix being the second edge.

The guide according to the invention will also be able to have, optionally, at least one of the following features:the bottom face of the collimation subassembly is a light input face suitable for receiving light emitted by a light source,the collimation subassembly comprises collimation means for directing at least a part of the light originating from the bottom face of the collimation subassembly toward the coupling portion,when rays are emitted from a predetermined point relative to the guide, pass through the input face and arrive on these collimation means, the collimation means are arranged to direct, directly or indirectly, a majority, notably all, of these rays toward the coupling portion in the form of a beam with parallel rays, or rays that are approximately parallel to within 5°. In other words, the majority, even all, of the rays emitted from a predetermined point, that pass through the input face and arrive on the collimation means are directed in such a way as to be contained in mutually parallel planes and the majority, even all, of the rays contained in one of these planes are mutually parallel. This feature offers the advantage of being able to direct the light beam leaving the guide in a predetermined direction, for example to meet current regulations,the guide comprising an optical axis, the direction of the rays of the beam with parallel rays is substantially parallel to the optical axis of the guide,the collimation means comprise a coupler arranged in such a way that, when rays are emitted from a predetermined point relative to the guide, pass through the input face and arrive on this coupler, a part of these rays are reflected by the coupler toward the coupling portion and another part of these rays are reflected by the coupler toward the rim of the collimation subassembly,the rim of the collimation subassembly is a reflection face having a section of parabolic form in a plane parallel to the top face of the subassembly, the focal point of this section of parabolic form being positioned at the level of the coupler. In this way, the coupler transmits a part of the light to the rim of the subassembly which redirects it, in the form of a beam with parallel rays,the rim of the collimation subassembly has a section of V form in a plane at right angles to the top face of the subassembly and containing the optical axis, the rim being formed by two surfaces forming between them an angle of 90°. Thus, these two surfaces can operate with total internal reflection of the light rays, which makes it possible to dispense with aluminizing the rim of the subassembly,the light output portion forms a guiding sheet arranged to guide, toward the output rim, light coming from the coupling portion and being propagated in the sheet, notably by total internal reflection. A sheet denotes a solid whose thickness, for example measured between the top and bottom faces, is substantially smaller than dimensions, such as the length or the width, of these top and bottom faces. The guiding sheet is produced from a transparent material with a refractive index greater than the refractive index of the medium in which the guide is intended to be immersed, for example air. Thus, a light ray introduced into the thickness of the sheet encounters the top or bottom faces with an angle of incidence relative to the normal which is greater than a limiting refraction angle. The ray is then likely to be reflected totally by the top and bottom faces. The light ray is therefore guided in the thickness of the guiding sheet by successive reflections between the two guiding faces,the output portion has a curved form. This means that the top face and/or the bottom face of the output portion is not entirely contained in a plane,the top face of the output portion has a cylindrical form. In this case, the directrix of the top face is a curve portion,the bottom face of the output portion has a cylindrical form. In this case, the directrix of the bottom face is a curve portion,the thickness of the sheet is substantially constant at any point of the output portion. “Thickness” should be understood to mean the distance separating the top face of the output portion and the bottom face of the output portion measured in a plane at right angles to the top face,the thickness of the output portion is substantially equal to the thickness of the collimation subassembly,the guide having an optical axis, in a section of the guide through a plane at right angles to the top face of the output portion passing through the optical axis, the top face of the output portion is parallel to the top face of the collimation subassembly,in a section of the guide through a plane at right angles to the top face of the output portion passing through the optical axis, the bottom face of the output portion is parallel to the bottom face of the collimation subassembly,the output rim comprises means for diffusing the light leaving this output rim. If necessary, the output rim can exhibit striations, prisms or toroids,the guide comprises a plurality of collimation subassemblies,the guide comprises a single light output portion and a plurality of coupling portions, each coupling portion coupling one of the subassemblies to the light output portion,the top face of the light output portion and the output face meet at a top output rim edge, the bottom face of the light output portion and the output face meet at a bottom output rim edge, the top output rim edge and/or the bottom output rim edge has a curved and smooth, that is to say unbroken, profile,at least a part of the bottom faces of the collimation subassemblies extends in one and the same first plane and at least one other part of the bottom faces of the collimation subassemblies extends in one and the same second plane, the first and second planes being distinct,the bottom faces of the subassemblies extend in mutually parallel planes,the bottom faces of the subassemblies extend in one and the same plane,the guide is monolithic, notably by molding of a plastic material.

Another subject of the invention is an optical device, notably for a motor vehicle, such as a lighting or signaling device, or a device for lighting the interior of the vehicle passenger compartment, comprising:at least one light source,at least one light guide according to the invention.

In one embodiment of the invention, the light source is a light-emitting diode.

If so desired, the device comprises a plurality of light sources arranged to light the light guide.

Advantageously, each light source is associated with a different subassembly. That is to say that each collimation subassembly is able to receive light emitted by just one of the light sources and to direct at least a part of this light toward the light output portion.

In an exemplary implementation of the invention, the device is arranged to emit, through the output face of the light guide, a light with a light intensity of between 50 candelas and 1200 candelas.

The optical device can, for example, fulfill a function of DRL (Daytime Running Light) type, of Stop type, of fog lamp type, of direction indicator type or of reversing light type.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1shows an optical device1for a motor vehicle, such as a signaling device suitable for fulfilling a function of the DRL type.

The optical device1comprises:a plurality of light sources2, each light source2being formed by a light-emitting diode, or LED,a light guide3having an optical axis O.

The light guide3comprises:a light output portion4having a top face41and a bottom face42linked together by a light output rim43,a plurality of collimation subassemblies5A and5B, anda plurality of coupling portions6coupling the light output portion4to a subassembly5B.

Each LED2is associated with a subassembly5A or5B. That is to say that each collimation subassembly5A or5B is suitable for receiving light emitted by an LED2and for directing at least a part of this light toward the light output portion4.

The subassemblies5A and5B are all substantially identical.

FIG. 2shows a section of the device1ofFIG. 1through a plane P at right angles to the top face41of the device1and containing the optical axis O, andFIG. 3shows a plan view of a collimation subassembly5B and of an LED2associated with this collimation subassembly5B of the device1ofFIG. 1.

The subassembly5B has a top face51and a bottom face52linked together by a rim53.

The bottom52and top51faces of the subassembly5B extend substantially in mutually parallel planes.

The bottom face52of the collimation subassembly5B is a light input face52suitable for receiving light emitted by the LED2when this LED2is positioned under the collimation subassembly5B.

The top face51of the collimation subassembly5B comprises a coupler54arranged in such a way that, when the LED2is positioned vertically to this coupler54and when rays R are emitted from a point of this LED2, pass through the input face52and arrive on this coupler54, a part R1of these rays R are reflected by the coupler54in a beam with substantially parallel rays R1toward the coupling portion6and another part R2of these rays are reflected by the coupler54toward the rim53of the collimation subassembly5B.

The rim53of the collimation subassembly5B is a reflection face having a section of parabolic form in a plane parallel to the top face51of the subassembly5B. The focal point f of this section of parabolic form is positioned at the level of the coupler54. In this way, the coupler54transmits the part R2of the light to the rim53of the subassembly5which redirects it, in the form of a beam with substantially parallel rays R2, toward the coupling portion6.

Furthermore, the rim53of the collimation subassembly5B is formed by two surfaces53A and53B forming between them an angle of 90°. These two surfaces53A and53B can thus operate with total internal reflection of the light rays R2.

The coupling portion6has a planar top face61and a planar bottom face62. These top61and bottom62faces are mutually parallel.

The top face61of the coupling portion6and the top face51of the collimation subassembly5B meet at a first edge7, and the top face61of the coupling portion6and the top face41of the output portion4meet at a second edge8.

The first edge7forms a straight segment.

The bottom face62of the coupling portion6and the bottom face52of the collimation subassembly5B meet at a third edge9, and the bottom face62of the coupling portion6and the bottom face42of the output portion4meet at a fourth edge10.

The third edge9forms a straight segment.

The bottom face62of the coupling portion6is, over its entire surface, facing the top face61of the coupling portion6. The first edge7and the third edge9are included in one and the same plane at right angles to the collimation subassembly, which is not represented. The second edge8and the fourth edge10are included in one and the same cylinder, which is not represented, defined by a translational generatrix on a directrix, the generatrix being a straight line at right angles to the collimation subassembly and the directrix being the second edge8.

The first edge7defines the apex of an angle formed by the top face61of the coupling portion6and the top face51of the collimation subassembly5B. This angle is equal to 135°.

The second edge8defines the apex of an angle formed by the top face61of the coupling portion6and the top face41of the output portion4. This angle is equal to 135°.

The third edge9defines the apex of an angle formed by the bottom face62of the coupling portion6and the bottom face52of the collimation subassembly5B. This angle is equal to 135°.

The fourth edge10defines the apex of an angle formed by the bottom face62of the coupling portion6and the bottom face42of the output portion4. This angle is equal to 135°.

When a light ray R3of the beams with parallel rays R1or R2arrives on the bottom face62of the coupling portion6with a given direction of incidence α1, this ray R3is successively reflected, notably by total internal reflection, by the bottom face62and by the top face61toward the light output portion4in a direction of reflection α2substantially parallel to the direction of incidence α1.

By virtue of this feature, the light rays R1, R2and R3being propagated in the guide pass from the collimation subassembly5B to the output portion4while retaining their direction.

The light output portion4forms a guiding sheet4made of PMMA with a refractive index of 1.49 or of PC with a refractive index of 1.59.

In the example described, the guide3is monolithic.

The light rays R1, R2and R3are guided in the sheet4toward the light output rim43, directly or by successive total internal reflections between the top41and bottom42faces of the sheet4.

The output portion4has a curved form. That is to say that the top face41and/or the bottom face42of the output portion4is not entirely contained in a plane.

In the example described, the top faces41and42of the output portion4each have a cylindrical form whose directrix is a curve portion.

The thickness e1of the sheet is substantially constant at any point of the output portion and is substantially equal to the thickness e2of the collimation subassemblies5A and5B.

In order to better understand the invention,FIG. 4Ashows a rear view of the device1ofFIG. 1andFIG. 4Bshows a front view of the device1ofFIG. 1.

TheseFIGS. 4A and 4Bshow, notably, the flatness of the top51and bottom52faces of the collimation subassemblies5A and5B, the curvature of the light output portion4of the device and the top61and bottom62faces of the coupling portions6in the curved areas of the output portion4.

A first part of the bottom faces52of the collimation subassemblies5A and5B extends in one and the same first plane P1; a second part of the bottom faces52of the collimation subassemblies5B extends in one and the same second plane P2; and a third part of the collimation subassemblies5A and5B extends in one and the same third plane P3.

The first plane P1, the second plane P2and the third plane P3are distinct.

The first plane P1and the third plane P3are mutually parallel.

The top face41of the light output portion4and the output face43meet at a top output rim edge44. The bottom face42of the light output portion4and the output face43meet at a bottom output rim edge45. The top output rim edge44and the bottom output rim edge45have a curved and smooth, that is to say unbroken, profile.

Obviously, numerous modifications will be able to be made to the invention without departing from the framework thereof.

It is possible, for example, to replace the collimation subassemblies5A and5B with other elements making it possible to direct the light emitted by the LEDs2toward the light output portion4.

FIG. 5shows a cross section of a device20according to the invention, similar to the device1ofFIGS. 1 and 2, except for the coupling portion26.

The coupling portion26has a planar top face261and a planar bottom face262. These top261and bottom262faces are mutually parallel.

The top face261of the coupling portion26and the top face51of the collimation subassembly5B meet at a first edge27, and the top face261of the coupling portion26and the top face41of the output portion4meet at a second edge

The first edge27forms a straight segment.

The bottom face262of the coupling portion26and the bottom face52of the collimation subassembly5B meet at a third edge29, and the bottom face262of the coupling portion26and the bottom face42of the output portion4meet at a fourth edge

The third edge29forms a straight segment.

The top face261of the coupling portion26is offset relative to the bottom face262of the coupling portion26. The first edge27and the third edge29are included in one and the same plane that is inclined relative to the collimation subassembly, which is not represented. The second edge28and the fourth edge30are included in one and the same cylinder, which is not represented, defined by a translational generatrix on a directrix, the generatrix being a straight line secant to the collimation subassembly and the directrix being the second edge.

The first edge27defines the apex of an angle formed by the top face261of the coupling portion26and the top face51of the collimation subassembly5B. This angle is equal to 145°.

The second edge28defines the apex of an angle formed by the top face261of the coupling portion26and the top face41of the output portion4. This angle is equal to 145°.

The third edge29defines the apex of an angle formed by the bottom face262of the coupling portion26and the bottom face52of the collimation subassembly5B. This angle is equal to 145°.

The fourth edge30defines the apex of an angle formed by the bottom face262of the coupling portion26and the bottom face42of the output portion4. This angle is equal to 145°.

While the system herein described, and the forms of apparatus for carrying this system into effect, constitute preferred embodiments of this invention, it is to be understood that the invention is not limited to this precise system and forms of apparatus, and that changes may be made in either without departing from the scope of the invention, which is defined in the appended claims.