FR2671162A1 - Motor vehicle headlamp with light conduction means - Google Patents

Abstract

The invention relates to a motor vehicle headlamp, characterised in that it comprises: - a light source (11), - a means for recovering flux associated with the source, - a grouped bundle (30) of optical fibres (F0), in which the entry adaptor of each directly receives the light from the said flux recovery means, the geometrical arrangement of the fibres in the cross section of the bundle of fibres varying between an entry face (31) and an exit face (32) so as to define, at the latter, a luminous pattern corresponding to the photometry of a light beam to be generated, and - a means (40) for projecting the said luminous pattern associated with said output adaptor.

Description

 The present invention relates generally to motor vehicle headlamps, and more particularly to a headlamp fitted, between its source and the exit of the light beam, with light conduction means.

 We already know, for example from FR-A 514 105 or FR-R 472 135, a projector which comprises a source such as a filament lamp, a reflector of the ellipsoidal type at the first focal point which is placed the source and in the region from the second hearth from which is placed an entry edge of a glass rod. The cut is formed in the first case by a screen placed close to said entry edge, and in the second case by a special design of the glass, divided into elementary blocks which end with subdivisions of the glass rod.

 In the first case, there is a significant loss in flow due to the presence of the screen. In the second case, the formation of the beam requires a light conductor and a glass of complex and expensive designs.

 The present invention aims to propose a new solution for forming a beam of predetermined photometry in a projector of the aforementioned type.

 More specifically, the invention aims to propose a projector in which, without providing a screening screen, still causing a loss of part of the flux emitted by the source, and without providing design glass special and expensive, it is very easy to form a beam satisfying certain photometric criteria, the headlamp moreover retaining all the advantages of headlamps with light conductors, in particular with regard to flexibility of installation in a vehicle.

To this end, it relates to a motor vehicle headlamp, characterized in that it comprises:
- a light source,
- a flow recovery means associated with the source,
a grouped bundle of optical fibers, one inlet end of each of which receives the light directly from said flux recovery means, the geometric arrangement of the fibers in the section of the bundle of fibers varying between an inlet face and an outlet face so as to define, at the level of the latter, a light pattern corresponding to the photometry of a light beam to be generated, and
- Means for projecting said light pattern associated with said outlet face.

According to another aspect, the invention relates to a motor vehicle headlamp, characterized in that it comprises:
- a light source,
- a flow recovery means associated with the source,
a grouped bundle of optical fibers, one inlet end of each of which receives the light directly from said flux recovery means, the geometric arrangement of the fibers in the section of the bundle of fibers varying between an inlet face and an outlet face so as to define, at the level of the latter, a light pattern corresponding to a virtual light source,
a reflector associated with said virtual light source to form a light beam to be generated, and
- a closing window.

Other aspects, aims and advantages of the present invention will appear better on reading the following detailed description of preferred embodiments thereof, given by way of non-limiting example and made with reference to the accompanying drawings, in which
FIG. 1 is a schematic view of a headlamp according to the present invention,
FIG. 2 is a view in axial vertical section of part of the headlight from FIG. 1,
FIG. 3 schematically illustrates, in perspective, a theoretical example of the evolution of a grouped bundle of optical fibers of a projector of the present invention,
FIG. 4 is a schematic perspective view of the projector with a first type of lamp,
FIG. 5 is a schematic perspective view of the projector with a second type of lamp,
FIG. 6 schematically illustrates, in perspective, a first concrete example of the evolution of a grouped bundle of optical fibers from a projector of the invention,
FIG. 7 illustrates by a partial view on an enlarged scale an alternative embodiment of the fiber bundle of FIG. 6,
FIG. 8 schematically illustrates, in perspective, a second concrete example of the evolution of a grouped bundle of optical fibers from a projector of the invention,
FIG. 9 schematically illustrates, in perspective, a third concrete example of the evolution of a grouped bundle of optical fibers from a projector of the invention,
FIG. 10 is a detailed perspective view of a practical embodiment possible for the bundle of FIG. 9,
FIG. 11 is a schematic perspective view of an alternative embodiment of a projector for the invention,
FIG. 12 is a perspective view of part of the projector of FIG. 11,
FIG. 13 schematically illustrates a European projection screen standardized at 25 meters, with an image of a virtual source of the projector in FIG. 11,
FIG. 14 illustrates in front view a particular embodiment of an end face of a grouped bundle of optical fibers according to the present invention, and
FIG. 15 illustrates in profile view a particular embodiment of an end face of a grouped bundle of optical fibers according to the present invention
It will be noted at the outset that, from one figure to another, identical or similar elements or parts have been designated by the same reference signs.

 Referring firstly to Figures 1 and 2, a motor vehicle headlight according to the present invention comprises a light source 10, such as a standardized filament lamp 11, a reflector of the ellipsoidal type 20, to a first focus F1 of which the source is placed, and forming a recuperator of the light flux emitted by the source 10.

 At 30 is indicated a grouped bundle of optical fibers FO. An entry face 31 of the bundle 30, containing the entry ends of the individual fibers, is situated in a plane perpendicular to the optical axis xx of the reflector 20 and passing in the vicinity of the second focal point F2 of said reflector 20, in such a way that practically all of the light rays coming from the reflector 20 are incident on said face.

 the beam 30 can follow in the vehicle any desired path, being suitably shaped when grouping the individual optical fibers.

This makes it possible in particular to position the light source at any location on the vehicle, if necessary at a distance from its front region, so as to minimize the space required in this region.

 There is also a projection device, in this case in the form of a plano-convex lens 40.

An exit face 32 of the bundle of optical fibers, containing the exit ends of the individual fibers, is situated in a plane essentially perpendicular to the main axis A of the lens 40 and passing in the vicinity of the object focus F of the lens.

 Finally, the projector comprises a closing glass 50, which is placed in front of the lens 40 and which comprises, for example, vertical streaks 51 for spreading the beam formed in the horizontal direction.

 According to an essential aspect of the invention, the use of a grouped bundle of optical fibers 30 as a means of transmitting light between the source 10 and the outlet of the beam (glass 50) makes it possible to keep the distribution of illumination as as provided by the reflector 20. Thus, as indicated schematically in FIG. 1, the lamp / reflector assembly applies to the input face 31 of the bundle of optical fibers a quantity of light which is greater in the area face center (hatched area) 311 to the quantity received by the - peripheral area (area not hatched 312).

 Thanks to the fact that each fiber, by nature, restores at its output the amount of light applied to its input, the present invention therefore makes it possible to find, at the output face 32, a similar sampling of light, that is to say say with fibers that restore more light than others, which is quite interesting in the case of projectors. In fact, the light beams of illumination must conventionally comprise a spot of light concentration, generally central, for the range of the beam, and a lower illumination zone but of wide blus extent, for the visual comfort of the driver.

 In contrast, a simple glass rod or the like, the use of which proves to be suitable for light signaling functions, inevitably causes a loss of the illumination distribution information collected at its input face, because we are witnessing within it a mixture of all the rays applied to the entrance.

 By nature, for optical fibers of constant circular section, the solid angle of opening of the incident radiation on each fiber at the entry 31 of the beam 30 is equal to the solid angle of opening of the radiation emanating from the end opposite of the fiber.

The characteristics of the lens 40, and in particular its diameter and its focal length, are chosen as a function of this solid angle, so that all of the radiation emanating from each fiber comes to strike the lens.

 According to another aspect of the present invention, it is possible to use the optical fiber bundle 30 to transform the light distribution obtained at its entry face into a different light distribution, and very advantageously into a light distribution corresponding to the photometry of the beam to be formed.

 In this case, the projection lens 40 allows, without the need to associate beam shaping elements (screens or the like) to project directly onto the road, through the glass 50 which can be designed to give a spread in width, the bundle as it is formed at the exit face of the bundle of optical fibers 30.

 Thus, FIG. 1 shows an outlet face 32 the shape and the light distribution of which correspond, with near homothety and upside-down and left-right reversal to counterbalance the inversion inherently effected by the lens 40, to a standardized passing beam in accordance with European regulations, while the shape of the entry face is circular with a concentration zone 311 located centrally.

 The conversion between the lighting pattern received at the face 31 and the lighting pattern to be projected via the lens 40 at the face 32 is effected by modifying the organization and the distribution of the fibers as they are progression in the beam 30 between the entry and exit faces 31 and 32.

Figure 3 illustrates a theoretical example of transposition. The twelve optical fibers FO1 located in the central concentration zone 311 of the entry face 31 are found in this case in a concentration zone 321 of the exit face which is spread in width and which occupies the lower region of said face . At the same time, the forty optical fibers
F02 located in the peripheral zone 312, receiving less light, from the entry face 31, are distributed around the spreading concentration zone 321, laterally and above it, so as to define an enlarged zone of lesser lighting, suitable for providing visual comfort.

 FIGS. 4 and 5 show two possible shapes of input faces, depending on the type of lamp used. In the case of FIG. 4, the filament 11 is axial, so that, to collect the maximum of light after reflection by the ellipsoidal mirror 20, the face 31 is circular.

 In the case of Figure 5, the lamp 10 has a transverse filament 11, oriented horizontally. In this case, the majority of the light reflected by the mirror 20 will be inscribed in a rectangle, and the face 31 is here correspondingly shaped.

 Is observed on the surface of the faces 31 of Figures 4 and 5 of the isolux curves C, decreasing values from the inside to the outside, representative of the fact that the amount of light received from the ellipsoid by the face 31 decreases progressively inside to outside.

 Thus in both cases, and more generally with any flux recovery means associated with a source of any type, it is observed that certain optical fibers receive more light than others, with equal section.

 FIG. 6 illustrates in detail a first concrete example of the modification of the distribution of the fibers FO in the bundle of fibers 30 between the inlet and the outlet. The face 31 is here circular (case of an axial source). The position of the individual fibers in the bundle 30 is progressively moved between the entry face 31 and the exit face 32 so that the light pattern at the latter corresponds to the beam typically formed by a parabolic reflector associated with a filament with blackout cup to form a passing beam.

 It may be recalled here that such a passing beam is characterized by two half-cuts, one horizontal and the other inclined at 150 above the horizontal, and by a spot of concentration situated just below the cut, at the meeting of the two half-cuts.

 It can be seen in FIG. 6 that the light pattern of the face 32, in front view, is turned upside down and left-right. In this way, after the image inversion conventionally created by a lens such as the lens 40 described above, a beam will be projected onto the road, the cutoff of which is correctly positioned in relation to regulatory requirements.

 With optical fibers FO whose section remains constant, it is understood that the useful surfaces of the faces 31 and 32 are identical. Thus, in the case where the face 31 has the shape of a circle of diameter D1, the face ~ 32 can for example be inscribed in a circle (marked CE) of diameter D2 greater than D1, and easily calculated as a function of l 'angle (typically 150) of lifting the cut.

 FIG. 7 represents a variant of the face 32, in which the modification of the distribution of the optical fibers FO in the bundle 30 is essentially carried out by shifting the fibers located in the lower region of the circle CE '(corresponding to the contour of the input face 31) to bring them laterally with respect to this circle, in a zone Z, so as to obtain an enlarged beam, as illustrated. This minimizes the lateral spreading work that glass 50 normally has to perform.

 FIG. 8 illustrates the shape of the optical fiber bundle 30 in the case where it is desired to form an anti-fog bundle. We observe at face 32 a large spread in width, and the distribution of the light pattern in a zone of high concentration 321, located above a horizontal line which will define a cut of the beam, and a zone of less concentration. 322, giving the light beam its full width on either side of the zone 321 and its full height above said zone 321.

 In this way, after inversion by the lens 40, an anti-fog beam in accordance with the regulations is obtained, which requires practically no additional spreading by the glass.

 FIG. 9 illustrates the case of a driving beam. A luminous pattern essentially ovoid or elliptical is observed at the exit face 32, with a spot of central concentration 321 and an area of lower concentration 322.

 Throughout the above description, it has been assumed that the individual optical fibers FO are fibers of constant circular cross section over their entire length.

 As a variant, and now with reference to FIG. 10, it can be provided that the optical fibers are each of variable contour and / or cross-sectional area. In the example illustrated, the surface area is constant but the contour gradually changes from the entry face to the exit face, from a circular shape to a flattened ovoid or elliptical shape.

 In this way, the width of the light pattern, which will give the width of the beam actually formed, is obtained without having to disrupt the distribution of the individual fibers in the beam 30. In particular, in the case of a driving light beam such as 'illustrated in FIG. 9, the desired light pattern can, with the individual fibers with an evolving contour which we have just described, be obtained without having to modify the distribution of the fibers FO in the bundle 30.

 We will now describe with reference to Figure 11 a projector according to a second embodiment of the present invention.

 Here, as in FIG. 1, there is a light source 10, 11, a flux recuperator 20 in the preferred form of a reflector of the ellipsoidal type, and a bundle 30 of optical fibers FO.

 However, in this case, the beam 30 is intended, by modifying the distribution of the fibers between the inlet face 31 and the outlet face 32, to form at the level of the latter a virtual light source whose contours and distribution the light within it is well determined, this virtual source being used in cooperation with an optical element such as a half-reflector 40 'to generate the desired beam.

 More precisely, and now with reference to both FIGS. 11 and 12, it can be seen that the fiber bundle 30 progressively passes from a circular contour (face 31), adapted to the axial source / ellipsoidal reflector couple, to a rectangular contour ( face 32), supposed to reproduce, seen from the reflector 40 ', the outline of an axial filament disposed tangentially to the optical axis x'x' of the reflector 40 ', below the latter. For purposes of illustration, there is shown on the input face 31 a zone of maximum concentration 311, a zone of medium concentration 312 and a zone of low concentration 313. Preferably, as shown in FIG. 12, the zones different homologous illuminations 321, 322 and 323 are essentially concentric in the contour of the outlet face 32.

 This defines a virtual light source whose edges are straight and sharp. Thus an image of the virtual source produced by the reflector 40 ′, for example the image I represented in FIG. 13, has its upper end aligned with good precision with the cut to be defined, for example on the European standard cut line. hHc, and, in combination with the other images produced, will be able to generate a cut beam whose cut is particularly well defined.

 The reflector 40 can be of any suitable type.

For example, to generate a passing beam according to European standards, it is possible to use a reflector as defined in particular in patent FR-A-2,536,502 or
FR-A-2 599 121 in the name of the plaintiff, the contents of these documents being incorporated here by reference. It will be recalled here that this type of surface is capable, in itself, of positioning the images of a light source in the projection plane so as to define a cut beam in accordance with European regulations.

 Both in the embodiment of Figure 1 and in that of Figure 11, in the case where at least one edge of the light pattern generated at the second face 32 of the fiber bundle 30 must have perfect sharpness along an edge (for example the edge defining a light beam cut-off in the case of FIG. 1), it is possible to use the variant of embodiment shown in FIG. 14. According to this variant, a mask or screening screen 60 is provided to mask half, or approximately half, of each FOC optical fiber adjacent to the cut. More specifically, in the illustrated case of a European passing beam whose cut was defined above, the cover 60 can include a first horizontal edge L passing diametrically at the end of each FOC fiber participating in the definition of the horizontal half-cut, and a second edge L ', inclined for example 150 downward relative to the edge L, passing diametrically at the end of each FOC fiber participating in the definition of the inclined half-cut.

 It will be noted here that the cover 60 is not a cut-off cover as it is usually understood. In fact, the cut is well generated by the outlet face 32 itself, the cover 60 being limited to improving if necessary the definition of said cut.

 Furthermore, it may be desirable in certain cases that the light beam, opposite the cut (that is to say illuminating the road closest to the vehicle), present a fuzzy limit, that is to say to say that there does not exist in this region of excessively clear transition between the beam and the surrounding darkness.

 To this end, and now with reference to FIG. 15, it can be provided that the optical fibers FO located opposite the cut, that is to say the highest fibers at the end 32 of the fiber bundle 30, are defocused (relative to the plane passing through the focal point of the lens 40). It is observed concretely in FIG. 15 that these tallest fibers are progressively shortened compared to the other fibers. In this way, a greater angular dispersion of the light radiation emanating from these fibers is ensured, in order to obtain the desired blurring effect.

 Of course, the present invention is in no way limited to the embodiment described above and shown in the drawings, but a person skilled in the art will know how to make any variant or modification in accordance with his spirit.

 In particular, the invention can be used with light sources of any type and position, in particular filament lamps or even discharge lamps. In the latter case, the present invention is particularly advantageous in that it makes it possible to eliminate parasitic rays, that is to say distant from a defined emission geometry, generated by this type of lamp without any auxiliary arrangement. .

 Furthermore, the flux recuperator constituted in the above description by a reflector of the ellipsoidal type, can be formed by any other type of optical means. Concretely, an ellipsoidal or similar reflector makes it possible to recover approximately 95% of the light flux emitted by the source.

Claims (16)

 1. Motor vehicle headlight, characterized in that it comprises:  - a light source (11),  - a flow recovery means (20) associated with the source,  - A grouped bundle (30) of optical fibers (F0) of which an inlet endpiece of each receives the light directly from said flux recovery means, the geometrical arrangement of the fibers in the section of the bundle of fibers varying between one face of inlet (31) and an outlet face (32) so as to define, at the latter, a light pattern corresponding to the photometry of a light beam to be generated, and  - Means (40) for projecting said light pattern associated with said outlet face.  2. Projector according to claim 1, characterized in that the quantity of light received by the optical fibers (FO) at their respective input endpiece varies according to their position.  3. Projector according to claim 2, characterized in that the light pattern comprises a zone of high concentration (321) defined by the juxtaposition of the optical fibers which receive at their respective end piece the greatest amount of light.  4. Projector according to one of claims 1 to 3, characterized in that a part of the contour of the outlet face (32) corresponds to a cut in the light beam to be generated.  5. Projector according to claim 4, attached to claim 3, characterized in that the zone of high concentration (321) of the light pattern is adjacent to the part of the contour of the exit face corresponding to the cut.  6. Projector according to one of claims 1 to 5, characterized in that the variation of the geometrical arrangement of the optical fibers (FO) in the bundle (30) has at least partially originated an evolution of the section of the individual optical fibers from their inlet nozzle to their outlet nozzle (32).  7. Projector according to claim 4, characterized in that a screen (60) is provided, one edge of which passes diametrically in line with the optical fibers adjacent to said part of the contour of the outlet face corresponding to the cut.  8. Projector according to one of claims 4 and 7, characterized in that optical fibers located opposite said part of the contour of the outlet face (32) corresponding to the cut are designed to cause diffusion of the light through the projection means (40).  9. Projector according to one of claims 1 to 8, characterized in that the projection means comprises a lens (40) of which an object focus (F) is located in the vicinity of a plane passing through the outlet face (32 ).  10. Motor vehicle headlamp, characterized in that it comprises:  - a light source (11),  - a flow recovery means (20) associated with the source,  - a grouped bundle (30) of optical fibers (F0), one inlet end of each of which receives the light from said flux recovery means, the geometric arrangement of the fibers in the section of the bundle of fibers varying between an inlet face (31) and an outlet face (32) so as to define, at the latter, a light pattern corresponding to a virtual light source,  - a reflector (40 ') associated with said virtual light source to form a light beam, and  - a closing glass (50).  11. Projector according to claim 10, characterized in that the outlet face (32) has an essentially rectangular outline.  12. Projector according to claim 11, characterized in that there is provided in the outlet face a high concentration area (321) of essentially rectangular shape, disposed along a large edge of said contour.  13. Projector according to one of claims 11 and 12, characterized in that the outlet face is arranged in a vertical plane passing through an optical axis (x'x ') of the reflector (40'), and in that said reflector is capable of positioning by itself the iages of the virtual source to form a beam of determined photometry  14. Projector according to one of the preceding claims, characterized in that the flux recovery means comprises a reflector of the ellipsoidal type (20), the light source being placed in the vicinity of a first focus (F1) of the reflector and the input face of the optical fiber bundle being placed in the vicinity of a second focal point (F2) of the reflector.  15. Projector according to claim 14, characterized in that the source (11) is elongated and arranged substantially on the major axis of said reflector and in that the contour of the input face (31) is of generally circular shape.  16. Projector according to claim 14, characterized in that the source (11) is elongated and disposed substantially transversely to the major axis of said reflector and in that the contour of the input face (31) is of generally rectangular shape.