Optical component for operation with complete internal reflection

Description

[0001] The present invention relates to the field of motor vehicle lighting devices. More particularly, the present invention relates to an optical part arranged to operate in total internal reflection and designed to form a cut-off beam.

[0002] It is known to use light guides, in which light is guided from an input diopter to an output diopter. The light propagates by total internal reflections on the reflection surfaces of this guide located between the input and output diopters. By giving these reflection surfaces specific shapes and positions, it is possible to obtain a beam with a given photometry.

[0003] In the case of a dipped beam, or more generally a beam with a cut-off line delimiting an illuminated area from a dark area where vehicles being followed or coming in the opposite direction may be located, these reflection surfaces are arranged to form the beam as well as its cut-off line. For example, a reflection surface may form a collector concentrating the rays towards a cut-off edge formed by an edge separating two other surfaces. An optical system is then arranged to image the cut-off edge. The latter will then form the cut-off line in the beam. Document US 2006239020 A1 discloses a light guide operating in this manner.

[0004] However, it happens that stray reflections cause some of the rays to fall into the shadow zone delimited by the cut-off line, thus generating a risk of glare. In principle, when designing an optical part, we seek to reduce these stray rays as much as possible.

[0005] In some existing light guides, the surface downstream and below the cut-off edge is arranged vertically, or in other words the cut-off edge is formed by a sharp angle. In this case, no ray that passes by the cut-off edge encounters the first reflection surface downstream of the cut-off edge. It follows that because of this angle, the imaging optical system must extend significantly below the level of the cut-off edge in order for the imaging system to recover these rays.

[0006] The applicant realized that it could reduce this height by decreasing the angle inside the optical part between the surfaces separated by the cut-off edge. However, in doing so, some of the rays that passed next to the cut-off edge encountered the first reflection surface downstream of the cut-off edge and were returned directly to the imaging optical system. These rays were therefore directed virtually as if they had come by passing under the focal line of the imaging optical system and were therefore returned above the cut-off, thus increasing the quantity of stray rays.

[0007] An aim of the present invention is to improve optical parts intended to operate in total internal reflection and designed so as to form a cut-off beam, in particular by reducing the risk of glare, in particular without increasing their height too much.

[0008] To this end, a first object of the invention relates to an optical part according to claim 1.

[0009] Thus, by preventing the rays reflected by the first reflection surface from directly reaching the exit diopter, the optical part according to the invention reduces, or even eliminates, the risk of glare.

[0010] Furthermore, it allows parts to be produced with a cutting edge with a less pronounced angle and therefore a lower height in relation to the length of the guide portion.

[0011] In addition, this also makes it possible to obtain a beam with more thickness for the same guiding portion of the same thickness but without this first reflection surface.

[0012] This also helps to avoid too much intensity concentration above the horizontal.

[0013] The light device according to the invention may optionally have one or more of the following characteristics: the first reflection surface comprises at least one facet arranged to reflect towards said second reflection surface said first rays so as to produce said terminal total internal reflection; this simplifies the design of the first reflection surface by managing some of the rays by a facet, since it is the arrangement of the slope of the latter which makes it possible to return the corresponding rays in this way; the first reflection surface comprises one or more prisms, called first prisms, the first prisms each having a reflection slope on which the corresponding rays are reflected, the or each facet being formed by the or one of the reflection slopes; this is a simple way of forming a facet; when the first reflection surface has several prisms, the reflection slopes are less and less steep as they move away from the cut-off edge towards the exit diopter;when the first reflection surface has several prisms, the pitch between the first prisms is constant; this makes it possible to have a connecting surface between two prisms of the same overall height and to avoid variations in thickness which could cause greater injection constraints in plastics processing; when the first reflection surface has several prisms, the pitch between the first prisms is approximately 1 mm; this small pitch makes it possible to further discretize and better control the total reflections; the second reflection surface comprises at least one facet arranged so as to reflect towards the exit diopter some of these rays reflected by the first reflection surface; this or these facets are prisms, called second prisms; the length of the first reflection surface from the cut-off edge towards the exit diopter is greater than twice, preferably four times, the height of the exit diopter;thanks to the arrangement of the first surface, it is possible to obtain such ratios without increasing the risk of glare, thus making it possible to have elongated and thin optical parts; the height of the exit diopter is less than or equal to 6 mm; the optical part comprises several of these said guide portions; the optical part comprises a plate whose downstream edge carries the exit diopters of the guide portions, the plate comprising the guide portions arranged adjacently directly or indirectly; we thus have a thin optical part with respect to its depth, namely with respect to the distance between the exit diopters and the corresponding entry diopters; the guide portions can be arranged indirectly two by two via an optically inactive junction portion; in other words the junction portion does not receive rays circulating in these guide portions. ;

[0014] Another subject of the invention is a vehicle lighting device comprising an optical part according to the invention. This lighting device may in particular be a vehicle headlight.

[0015] The vehicle lighting device according to the invention may comprise: an optical part according to the invention, a light source opposite the entrance diopter, the light device being arranged so that the rays emitted by the light source exits the exit diopter to participate in the creation of a cut-off lighting beam, in particular a flat cut-off.

[0016] In particular, this lighting beam can be a side lighting beam also called a “cornering” function.

[0017] Another subject of the invention is a vehicle comprising a vehicle lighting device according to the invention.

[0018] Unless otherwise indicated, the terms "rear", "front", "lower", "upper", "top", "down", "right", "horizontal", as well as their variations in gender or number, refer to the direction of light emission from the optical part. Unless otherwise indicated, the terms "upstream" and "downstream" refer to the direction of light propagation.

[0019] 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 ] There figure 1 represents a top view of the optical part according to an exemplary embodiment of the invention; [ Fig. 2 ] There figure 2 represents a perspective view of the figure 1 , top view; [ Fig. 3 ] There figure 3 represents a rear view of the figure 1 ; [ Fig. 4 ] There figure 4 represents a perspective view figure 1 , bottom view; [ Fig. 5 ] There figure 5 represents a sectional and perspective view along plane AA' in figure 1 ; [ Fig. 6 ] There figure 6 represents the section corresponding to the cut of the figure 5 ; [ Fig. 7 ] There figure 7 represents a beam obtained with an optical part similar to that of the figure 1 but with a first flat reflection surface; [ Fig. 8 ] There figure 8 represents a beam obtained with the optical part illustrated in figure 1 .

[0020] THE figures 1 à 5 illustrate an example of an embodiment of an optical part 1 according to the invention.

[0021] In this example, the X, Y, Z axes correspond to the longitudinal, transverse and vertical directions respectively of a vehicle in which the optical part 1 is intended to be mounted. In these figures 1 à 6 , the optical part 1 is therefore oriented relative to these axes X, Y, Z according to the orientation that it is intended to have in this vehicle.

[0022] In this example, optical part 1 is intended to perform a lighting function in the sides. Here, as illustrated in figures 1 à 3 , the front and the rear of the optical part 1, are therefore generally diagonal to the longitudinal axis X and the transverse axis Y, the optical axis O of the optical part being oriented here in a direction close to a bisector formed between the longitudinal axis X and the transverse axis Y. In other words, once mounted in the vehicle while respecting these orientations, the optical part 1 allows the lighting device which comprises it to illuminate on the sides and diagonally, here between the left and the front of the vehicle.

[0023] Generally speaking, as illustrated in this example, particularly in figure 1 , this optical part 1 may comprise a plurality of light guiding portions 10. These guiding portions 10 together form the optical part 1 in a single piece. In particular, these guiding portions 10 may be made from a single piece with the entire optical part 1.

[0024] According to the invention, as here, the guide portions 10 can be arranged side by side, in particular as here in a fan shape. This makes it possible to broaden the overall illumination beam formed by the optical part 1 when it is coupled with light sources.

[0025] These guide portions 10 can, as here, be connected to each other by a portion of the optical part, called the junction portion 30, forming the continuity of material between two adjacent guide portions 10.

[0026] In this application, to explain the arrangement of these guide portions 10, the cuts and sections of the figures 5 And 6are made at one of these guide portions 10, namely the fourth guide portion starting from the right of the optical part 1 (namely in figure 1 , the fourth from the bottom). Similarly, the references on the drawings are essentially placed on this fourth guide portion 10.

[0027] The various explanations and illustrations of the application can be transposed to each of the guide portions 10 of the optical part 1.

[0028] Here, the figure 6 schematically illustrates the path of the rays r 1 , r 2 in the optical part 1, more precisely here in one of the guide portions 10, as well as the different total internal reflection surfaces 4, 5, 11, 21 (or TIR, for “Total Internal Reflection” in English).

[0029] The optical part 1 is arranged so as to guide the rays r 1 , r 2 between an input diopter 2 of these rays and an output diopter 9 of the same guide portion. Preferably, this arrangement is such that very few, or even no, rays pass through the junction portions 30.

[0030] The exit diopter 9 extends between a first reflection surface 11 and a second reflection surface 21. As here, these two reflection surfaces 11, 21 can extend essentially horizontally, the exit diopter 9 extending from bottom to top.

[0031] The first reflection surface 11 and the second reflection surface 21 here form the front portion of an upper portion of the guide portion 10. This front portion extends between the exit diopter 9 and another total internal reflection surface, namely the return surface 4.

[0032] Here, as can be seen in figures 3 à 5 , each guide portion 10 comprises a lower portion, extending downwards between the input diopter 2 and the return surface 4. In this example, this lower portion forms an input collimator 3.

[0033] Generally speaking, as here, the optical part 1 may comprise on each side means for fixing to a vehicle lighting device. Here the optical part 1 comprises two. These are two fixing ears 32, 33, formed in a single piece with the rest of the optical part 1.

[0034] As can be seen, more particularly in figure 1 , the optical part 1 comprises portions forming rear tabs 31, allowing the vertical positioning, namely in the Z direction, of the optical part 1.

[0035] Also, as here, referencing pins 34, 35, in particular of different shapes, can be provided to ensure a more precise position of the optical part 1 in the lighting device.

[0036] As can be seen in figure 5 , at each guide portion 10, the lower surface comprises a cut-off edge 6, formed by an edge separating the first reflection surface 11 from another total internal reflection surface 5, which forms a folder 5. The first reflection surface 11 extends downstream of the cut-off edge 6, from the cut-off edge 6 and towards, here up to, the exit diopter 9. The folder 5 extends upstream of the cut-off edge 6, from the cut-off edge 6 and towards, here up to, the collimator 3.

[0037] The second reflection surface 21 can be connected to the return surface 4 by other surfaces.

[0038] In general and as here, all of the upper portions of the guide portions 10 can form a plate 8, here with the junction portions 30. On the figures 1 et 2 , it is essentially this plate 8 which is visible. In particular, this plate 8 is thin compared to the width of the optical part 1.

[0039] As for example illustrated in figure 5 , the length L of the first reflection surface 11 from the cut-off edge 6 to the exit diopter 9 is greater than four times the height h of the exit diopter 9. For example, the height h of the exit diopter 9 may be, as here, less than 6 millimeters (mm).

[0040] In the example illustrated, each upper portion present is formed by the first reflection surface 11 and the folder 5. The length of the first reflection surface 11 of the guide portions 10 is here approximately 25 mm.

[0041] There figure 6 is a longitudinal section, namely according to the maximum dimension along which the guide portion 10 considered and illustrated extends. This figure makes it possible to illustrate the operation of each guide portion 10.

[0042] Once the optical part 1 is positioned in the lighting device, here a projector P, a light source is arranged opposite the input diopter 2, formed at the bottom of the collimator 3.

[0043] Generally speaking, the input diopter 2 is arranged so as to receive almost all, or even all, of the rays emitted by the light source 40. The collimator 3 concentrates these rays r 1 , r 2 , towards the return surface 4. Thanks to its arrangement with the input diopter 2, this return surface 4 returns the light rays r 1 , r 2 coming from the input diopter 2 towards the cut-off edge 6.

[0044] Generally speaking, the output diopter 9 can, as here, form a projection member, arranged so as to image the cut-off edge 6.

[0045] For example, as here, the exit diopter 9 may have a curvature arranged so that this exit diopter 9 forms a convergent system having a line of foci. This line of focus is arranged so as to superimpose itself on the cut-off edge 6.

[0046] Several categories of rays returned by the return surface 4 can be defined: the first rays r 1 , the second rays r 2 and the third rays (not shown).

[0047] The path of the first rays r 1 will be described in more detail later.

[0048] Generally speaking, as here, each guide portion 10 can be arranged so that the rays passing at the level of the cut-off edge 6 directly reach the exit diopter 9. These are said second rays. This cut-off edge 6 being superimposed on the focal line, these second rays r 2 then exit parallel to the direction of the optical axis of the corresponding guide portion 10, axis oriented horizontally according to this illustrated example.

[0049] Generally speaking, as in this example, the third rays, not shown, can meet the folder 5 slightly upstream of the cut-off edge 6. The folder 5 is oriented in such a way that it returns these third rays towards the second reflection surface 21, which thanks to its arrangement, returns them towards the exit diopter 9. These third rays will thus pass above the cut-off edge 6 and therefore the line of foci, so that the exit diopter 9 refracts them downwards.

[0050] The second rays r 2 form the upper limit of the beam, the third rays being directed below this limit. It follows that the exit diopter 9 projects from these rays a beam having a cut-off line formed by this upper limit, which corresponds to the shape of the cut-off edge 6.

[0051] However, in the case of an elongated and thin upper portion, as in this example, in particular in the case of a plate 8, the angle between the folder 5 and the first reflection surface 11 seen from inside the corresponding guide portion 10 is not very marked, in particular between 180° and 225°. There is a risk that certain rays, namely said first rays, passing directly above the cut-off edge 6 after their deflection by the return surface 4, reach the first reflection surface 11, rather than directly reaching the exit diopter 9. In such a case, there is a risk that these first rays r 1 are reflected upwards by the first reflection surface 11 and then reach the exit diopter 9. These first rays would thus come virtually from below the focal line and would therefore be refracted upwards, creating a risk of dazzling.

[0052] To avoid this, the first reflection surface 11 comprises an arrangement from the cut-off edge 6, here in the form of prisms 13, making it possible to prevent the first rays r 1 , passing next to, here above, the cut-off edge 6 from going, after total internal reflection on the first reflection surface 11, directly onto the exit diopter 9.

[0053] Here these prisms 13, called first prisms 13, are formed by an alternation of ribs and ridges oriented generally perpendicular to the optical axis of the corresponding guide portion 10. Each first prism 13 thus comprises a slope or reflection facet 14 oriented upstream and a junction facet 15 oriented downstream.

[0054] It is these reflection facets 14 which are arranged so as to allow the first reflection surface 11 to deflect the first rays r 1 by total internal reflection on these reflection facets 14. By this deflection, the reflection facets 14 send these first rays r 1 onto the second reflection surface 21 with an angle making it possible to produce a total internal reflection on this said second reflection surface 21. These first rays r 1 are then reflected towards the exit diopter 9 after this reflection on this said second reflection surface 21. This reflection is thus called terminal total internal reflection.

[0055] The slopes of the reflection facets 14 are less and less steep as they move away from the cut-off edge 6 towards the exit diopter 9. The first rays r 1 are in fact more and more grazing the further their point of impact on the first reflection surface 11 is from the cut-off edge 6.

[0056] Here the first prisms 13 are arranged up to the exit diopter 9. However, it is possible to arrange them only on an upstream portion of the first reflection surface 11, for example on the first 12 to 15 millimeters and / or at least on the first third of the first reflection surface 11.

[0057] The pitch between the first prisms 13 is constant here. This simplifies the design of optical part 1 and potentially avoids variations in part thickness. As in this example, the pitch between the first prisms can be approximately 1 mm.

[0058] Here, the second reflection surface 21 is smooth. However, alternatively, it could also comprise a plurality of prisms, called second prisms, the reflection facets of which would be arranged so as to reflect towards the exit diopter 9 the first rays r 1 reflected by the first reflection surface 11.

[0059] These second prisms may have the same characteristics as the first prisms 13, in particular concerning their pitch and / or the slope of their reflection facets 14.

[0060] Thus, each of the guide portions 10 is capable of forming a beam having a higher cutoff. The sum of all of these beams forms the overall illumination beam F in the sides, illustrated in figure 8 . We can observe that this global beam F has a cut-off line C arranged on the horizon H. Above the cut-off line C, the illustrated isolux curves represent parasitic rays but which are in sufficiently small quantity not to dazzle.

[0061] In the absence of the first prisms 13, we obtain the beam F' of the figure 7 . If it also has a horizontal cut-off line C', there are more stray rays above the cut-off line C'. The risk of glare is higher.

[0062] Furthermore, these first prisms 13 make it possible to reinject certain rays, namely the first rays r 1 , under the cut-off line C and thus give a vertical thickness of the beam F greater than that of the beam F' obtained without the first prisms 13.

[0063] The efficiency and quality of the lighting beam in the corners have therefore been improved despite the low thickness of the guide portions 10 and therefore of the plate 8 of the optical part 1.

[0064] Although particularly interesting in the context of lighting in corners, the invention can be applied to other types of cut-off beams, such as a fog beam, or even a dipped beam.

Claims

1. An optical component (1) intended to operate with total internal reflection and comprising at least one light guide portion (10), the guide portion comprising: - an entry diopter (2), - a return surface (4), - a cutoff edge (6), - a first total internal reflection surface (11) downstream of the cutoff edge, - a second total internal reflection surface (21), - an exit diopter (9) that images a row of focal points, the row of focal points being arranged on the cutoff edge (6), the entry diopter and the return surface being arranged such that the return surface returns the light rays (r1, r2) from the entry diopter toward the row of focal points, the cutoff edge being formed by an edge separating the first reflection surface (11) from another total internal reflection surface (5), which forms a folder (5), the first reflection surface (11) extending downstream of the cutoff edge (6), from the cutoff edge (6) and towards the exit diopter (9), the folder (5) extending upstream of the cutoff edge (6), from the cutoff edge (6) and towards a portion of the guiding portion extending between the entry diopter (2) and the return surface (4). said optical component being characterized in that these rays (r1, r2) comprise first rays (r1) that pass next to the cutoff edge (6) and reach said first reflection surface (11), said first reflection surface being arranged so as to reflect these first rays (r1) toward said second reflection surface (21) so as to produce a terminal total internal reflection from this said second reflection surface, these first rays being reflected toward the exit diopter (9) through this terminal total internal reflection.

2. The optical component (1) as claimed in claim 1, wherein the first reflection surface (11) comprises at least one facet (14) arranged so as to reflect said first rays (r1) toward said second reflection surface (21) so as to produce said terminal total internal reflection.

3. The optical component (1) as claimed in claim 2, wherein the first reflection surface (11) comprises one or more prisms, called first prisms (13), the first prisms each having a reflection slope from which the corresponding rays are reflected, the or each facet (14) being formed by the or one of the reflection slopes.

4. The optical component (1) as claimed in claim 3, wherein, when the first reflection surface (11) has multiple first prisms (13), the reflection slopes are increasingly less steep as they move away from the cutoff edge (6) toward the exit diopter (9).

5. The optical component (1) as claimed in claim 3 or 4, wherein, when the first reflection surface (11) has multiple first prisms (13), the pitch between the first prisms is constant.

6. The optical component (1) as claimed in any one of claims 3 to 5, wherein, when the first reflection surface (11) has multiple first prisms (13), the pitch between the first prisms is approximately 1 mm.

7. The optical component (1) as claimed in any one of the preceding claims, wherein the second reflection surface (21) comprises at least one facet arranged so as to reflect some of these rays reflected by the first reflection surface (11) toward the exit diopter (9).

8. The optical component (1) as claimed in any one of the preceding claims, wherein the length (L) of the first reflection surface (11) from the cutoff edge to the exit diopter (9) is greater than twice the height (h) of the exit diopter.

9. The optical component (1) as claimed in any one of the preceding claims, comprising a plurality of these said guide portions (10).

10. The optical component as claimed in claim 9, comprising a plate (8) the downstream segment of which bears the exit diopters (9) of the guide portions (10), the plate comprising the guide portions arranged directly or indirectly adjacently.

11. A vehicle lighting device (P), comprising: - an optical component (1) as claimed in any one of the preceding claims, - a light source (40) facing the entry diopter (2), the lighting device being arranged such that the rays (r1, r2) emitted by the light source exit the exit diopter (9) so as to contribute to producing a lighting beam (F) with a cutoff (C), in particular with a flat cutoff.

12. Vehicle comprising a light device according to claim 11.