EP0723109A1 - Vehicle headlamp with dioptric means interposed between the light source and the reflector - Google Patents

Abstract

The headlamp has a light source (10), reflector (20) and front glass (30). A dioptre lens (40b) is selectively interposed between the source and a reflector zone, modifying the beam by refraction. The dioptre has internal surfaces (41b) generally cylindrical, with its axis close to the reflector optical axis (A), which is near the source. The dioptre external surface (42b) is inclined progressively, relative to the internal surface, to defocus the source. This is in the horizontal optical axis and the vertical above and below the axis. This ensures shifting of the source image and dioptre extended angle laterally only. The dioptre internal surface may be a cylinder of revolution and there may be two dioptre lenses.

Description

The present invention relates generally to motor vehicle headlamps, and more particularly relates to a headlamp capable of generating at least two beams of different types with a single source and reflector.

Document FR-A-2 699 259 already discloses a motor vehicle headlamp which comprises a light source, a mirror focused in the vicinity of the source and a closing lens, and at least one thick blade made of a material capable of allow at least part of the spectrum of the radiation emitted by the source to pass towards at least one region of the mirror, and motorized means for selectively moving the blade or blades opposite the source in order to ensure, by refraction, a defocusing the source with respect to the mirror and varying the distribution of the radiation in the generated beam.

In an embodiment described in this document, the thick blades have the shape of blades with parallel faces transparent to visible radiation, to selectively generate a beam of road concentrated in the axis and, when the blades are interposed on the path of the light, one, wider road beam.

Also known from document US-A-4, 373 178 is a luminaire in which a diopter of revolution with a profile in the form of a lens is interposed between the source and the mirror. However, such a luminaire meets requirements which have nothing to do with those of automotive lighting.

Finally, FR-A-1 534 089 discloses a projector in which a transparent optical element with total reflection is placed below the lamp, in order to modify the configuration of the generated beam.

A drawback of the known diopter solutions lies in that the modification of the beam obtained during the interposition of the diopter (s) is poorly controlled. More specifically, if it actually gives rise to a certain widening of the beam, it also undesirably induces an increase in the thickness of the beam, with too much light either near the vehicle or above the road .

The present invention aims to overcome these limitations of the state of the art, and to propose a headlamp comprising a diopter which can be selectively interposed between the source and the mirror and capable of producing an enlarged beam, in particular an enlarged main beam, having the qualities required.

Thus the present invention relates to a headlamp for a motor vehicle, comprising a light source, a mirror and a lens, as well as at least one diopter capable of being selectively interposed between the source and at least one area of the mirror to ensure by refraction a modification of the generated beam, characterized in that at least one diopter comprises an interior generally cylindrical surface whose axis is located in the vicinity of an optical axis of the mirror itself passing in the vicinity of the source, and an exterior surface whose l the inclination relative to the interior surface varies progressively so as to define by refraction a progressive defocusing of the source both in horizontal direction along said optical axis and in vertical direction above and below the optical axis, and to ensure an offset of the images of the source essentially in lateral direction only, and in that the or each diopter presents a stretched so limited angular be interposed between the source and only one side area of the mirror.

• la surface intérieure du ou de chaque dioptre est cylindrique de révolution.
• le projecteur comporte deux dioptres identiques aptes à être interposés de part et d'autre de la source.
• en direction horizontale, le ou chaque dioptre assure une défocalisation qui diminue progressivement de sa région proche du fond du miroir vers sa région éloignée du fond du miroir.
• l'inclinaison mutuelle des faces intérieure et extérieure du ou de chaque dioptre, dans un plan horizontal passant par l'axe optique, diminue sensiblement linéairement en fonction de la cote suivant ledit axe optique.
• en direction verticale, la défocalisation est minimale, de préférence nulle, dans un plan horizontal passant par l'axe optique pour atteindre deux maxima aux extrémités supérieure et inférieure de chaque dioptre.
• le ou chaque dioptre est tronqué à son extrémité éloignée du fond du miroir, de manière à laisser une partie marginale du miroir exposée directement à la source quelle que soit la position du dioptre.
• le ou chaque dioptre est tronqué par une surface généralement conique centrée sur l'axe optique.

Preferred, but not limiting, aspects of the projector according to the invention are as follows:

• the inner surface of the or each diopter is cylindrical in revolution.
• the projector has two identical dioptres capable of being interposed on either side of the source.
• in the horizontal direction, the or each diopter ensures a defocusing which progressively decreases from its region close to the bottom of the mirror to its region remote from the bottom of the mirror.
• the mutual inclination of the inner and outer faces of the or each diopter, in a horizontal plane passing through the optical axis, decreases substantially linearly as a function of the dimension along said optical axis.
• in the vertical direction, the defocusing is minimal, preferably zero, in a horizontal plane passing through the optical axis to reach two maxima at the upper and lower ends of each diopter.
• the or each diopter is truncated at its end remote from the bottom of the mirror, so as to leave a marginal part of the mirror exposed directly to the source whatever the position of the diopter.
• the or each diopter is truncated by a generally conical surface centered on the optical axis.

• la figure 1 est une demi-vue schématique en coupe horizontale d'un projecteur selon la présente invention,
• la figure 2 est une vue de face d'une partie du projecteur de la figure 1,
• la figure 3 est une vue en coupe horizontale d'un projecteur selon une variante de réalisation de l'invention,
• la figure 4 est une vue de face du miroir du projecteur de la figure 3, illustrant différentes zones,
• la figure 5 est une vue à échelle agrandie illustrant le comportement optique d'une partie du projecteur de la figure 1 dans un plan horizontal,
• la figure 6 est une vue à échelle agrandie illustrant le comportement optique d'une partie du projecteur de la figure 1 dans un plan vertical transversal à l'axe optique, et
• la figure 7 illustre dans un plan de projection le déplacement d'une image du filament occasionnée par l'interposition d'un dioptre, en l'absence de la glace de fermeture du projecteur.

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 nonlimiting example and made with reference to the appended drawing, in which :

• FIG. 1 is a schematic half-view in horizontal section of a projector according to the present invention,
• FIG. 2 is a front view of part of the projector of FIG. 1,
• FIG. 3 is a view in horizontal section of a headlight according to an alternative embodiment of the invention,
• FIG. 4 is a front view of the mirror of the projector of FIG. 3, illustrating different zones,
• FIG. 5 is a view on an enlarged scale illustrating the optical behavior of a part of the projector of FIG. 1 in a horizontal plane,
• FIG. 6 is a view on an enlarged scale illustrating the optical behavior of a part of the projector of FIG. 1 in a vertical plane transverse to the optical axis, and
• FIG. 7 illustrates in a projection plane the displacement of an image of the filament caused by the interposition of a diopter, in the absence of the lens closing the projector.

It will be noted at the outset that, from one figure to another, identical or similar elements or parts are designated as far as possible by the same reference signs.

Referring first to Figures 1 and 2, there is shown a motor vehicle headlamp which comprises a light source 10, in this case the generally cylindrical filament of an incandescent lamp, a mirror 20 of the parabolic type, focused at F on the source or in the vicinity thereof, a closing glass 30, and two displaceable diopters 40a, 40b which can be selectively interposed between the source 10 and certain zones of the mirror 20.

Each diopter can occupy an inactive or retracted position (not shown), for example by being translated through openings provided in the region of the bottom of the mirror, and a well-defined active position, as illustrated in FIGS. 1 and 2.

We will not describe here the diopter support means or the motorized means intended for their displacement, these means can for example be of the type described in document FR-A-2 699 259.

Preferably, the dioptres 40a, 40b are made of glass. If desired, these diopters can be made of a material capable of acting on the spectral distribution of light, according to the teachings of the aforementioned document.

As can be clearly seen in FIG. 2, the mirror 20 is divided into four zones, namely two lateral zones 21a, 21b, an upper zone 22 and a lower zone 23.

The lateral zones 21a, 21b are the zones covered by the solid angle of the respective diopter 40a, 40b seen from the focal point F of the mirror, while the other two zones 22, 23 remain directly exposed to the light coming from the source, whatever or the position of the diopters.

Each diopter 40a, 40b comprises an inner surface, respectively 41a, 41b, which is cylindrical in revolution and centered at least approximately on the optical axis A of the projector on which the filament 10 is aligned. Each diopter further comprises an outer surface, respectively 42a, 42b, the complex shape of which is chosen so as to ensure variable defocusings of the source in order to ensure a widening of the beam generated without however inducing a significant increase in the height of the beam. . In addition, these external surfaces are designed to ensure, by the game of progressive defocusing, a great homogeneity in the spreading of the beam, this homogeneity being if necessary worked at the level of the glass.

More specifically, the outer surface 42a or 42b is a surface such that, in sections through planes passing through the optical axis of the projector, the inclination mutual traces of the interior and exterior surfaces in such a plane varies progressively, between a maximum mutual inclination, for example of the order of 45 °, at the rear end of the diopter (on the left in FIG. 1) and a mutual inclination minimum, for example from a few degrees to 10 °, at the front end of the diopter (on the right in Figure 1).

In addition, the exterior surfaces 42a, 42b of the diopters are such that, in sections through vertical planes perpendicular to the optical axis of the projector, the inclination of the traces of the interior and exterior surfaces of a diopter varies between maxima ( for example of the order of 20 to 25 °) at the upper and lower ends and a minimum (zero angle) halfway up the diopter.

With reference to FIG. 5, two different defocusings have been illustrated for two different directions of the light coming from the focal point F in the axial horizontal plane. for the ray R1, directed the most rearward, the diopter 40b creates a virtual source 101 placed substantially behind the real source 10. For the ray R2, less inclined towards the rear, the virtual source obtained 102 is less shifted towards the back.

Thus it is understood that the defocus decreases progressively as one moves from the rear towards the front of the diopter, thereby ensuring an essentially continuous lateral spreading of the light.

It is further observed that, in this case, the defocusing is all the more reduced as the point of impact of the light ray on the mirror is distant, which means that the small images of the filament in the generated beam are less deflected horizontally than large images. The beam portion generated by the zones 21a, 21b therefore retains a spot of light concentration in the axis of the vehicle.

With reference to FIG. 6, it can be seen that the more the rays R3, R4 coming from the focal point F are inclined up or down, the more the corresponding virtual source, respectively 103, 104, is offset, also upwards or down.

Now, if we position ourselves at any point on the diopter, we understand that the phenomena illustrated in Figures 5 and 6 will accumulate, thereby widening the beam in a variable manner without significant influence on its height distribution. More precisely, and now with reference to FIG. 7, an inclined image of the filament, designated by I1, which would be practically centered on the reference center of a projection screen in the absence of the diopter, will be subject to by the presence of the diopter on the one hand an offset along its major axis (arrow F1), to obtain the image I2, and on the other hand a vertical drawdown (arrow F2), to return to a height close to that of the optical axis as shown in picture I3.

Thus the diopter has the effect of shifting an image I1 in a generally lateral direction (image I3).

The fact that the diopters 40a, 40b have a limited angular extent on either side of the source 10 makes it possible to work on images of the source which move between a horizontal orientation and a certain oblique orientation, determined by this angular extent. In this way the enlargement is carried out on images which, in a projection plane, have a limited height.

On the contrary, the images of the filament generated by the zones 22 and 23, which have the double characteristic of being large and being either vertical, or slightly inclined relative to the vertical, are not subject to spreading by the diopters. In fact, it has been observed that a shift of this type of image by dioptric means cannot be effected without compromising the quality of the widened beam. These images therefore always keep the same position in the beam.

Referring now to Figures 3 and 4, there is illustrated an alternative embodiment of a projector of the invention, according to which each diopter 40a, 40b is truncated in its front region so as to leave on the mirror, beyond the zones 21a 21b subject to the action of the diopters, two marginal zones 24a, 24b which directly receive the light coming from the source whatever the position, retracted or active, of the diopter.

Preferably, the truncation of the diopters is carried out by conical surfaces (surface 43a for the diopter 40a in FIG. 3) centered on the optical axis and of angle at the appropriate vertex.

In this way, when the diopters are placed in the active position, only images from the bottom of the mirror and the medium-sized images of the filament will be processed by the diopters, thereby broadening the beam evenly, while the small images generated by the marginal zones 24a, 24b, the most distant from the filament, remain positioned in the axis of the beam to maintain a high concentration of the beam along this axis.

Thus the mirror (FIG. 4) has six zones, 21a, 21b, 22, 23, 24a and 24b of which only the zones 21a, 21b, defining a kind of bow tie over only part of the width of the mirror, are affected by the interposition of diopters. FIG. 3 also indicates an area 25 corresponding to the lamp hole.

The outer surface 42a, 42b of each diopter can be defined either empirically or mathematically, depending on the desired result.

où

A(x) =

α(1-(x/l))

Dx =

[0;l]

0 =

origine des coordonnées à l'intersection des traces 41b, 42b,

l =

longueur de la surface suivant x.

We will indicate below a possible equation for the trace of the external surface 42b of the diopter 40b in the axial horizontal plane, this equation being given in the system of axes (x, y) represented in FIG. 5: $${\text{y (x) = ∫}}_{\text{Dx}}\text{tan (A (x)). dx}$$

or

A (x) =

α (1- (x / l ))

Dx =

[0; l ]

0 =

origin of the coordinates at the intersection of traces 41b, 42b,

l =

length of the surface along x.

Integration gives: $$\text{y (x) = (}\underline{\text{l}}\text{/α).ln(cos(A(α)/cos(α))}$$

This equation ensures a decrease in the mutual inclination of the traces 41b, 42b which evolves linearly as a function of the dimension in x. Of course, one can provide a profile which gives a non-linear evolution.

In the above description, the mirror 20 is parabolic, that is to say that it generates a long-range and relatively narrow beam in the absence of the dioptres, and that it generates an enlarged beam, but with a good concentration in the axis, in the presence of the diopters.

Of course, the invention can also be implemented in other types of projectors. In particular, owing to the fact that the dioptres according to the invention make it possible to practically not modify the beam in height, they can be used with self-generating mirrors of cut beams, that is to say whose surface is calculated to bring all the images of the filament below a given cut limit, preferably by aligning the highest points of these images with this cut limit. The invention can also be used in fog lamps and projectors for beams complementary to the passing beams.

According to another interesting embodiment, diopters according to the invention can be used to transform a long-range beam into an anti-fog beam, by virtue of the ability of the dioptres to cause the images to fold down.

In addition, according to another variant, it is possible to provide, to reduce the proportion of light subject to widening by the diopters, to provide only one diopter on one side of the source. To modulate this proportion as desired, one can also play on the angular extent of the diopters, which determines the relative importance of the surfaces 21a, 21b with respect to the surfaces 22, 23.

Claims (8)

Motor vehicle headlamp, comprising a light source (10), a mirror (20) and a lens (30), as well as at least one diopter (40a, 40b) capable of being selectively interposed between the source and at least one zone (21a, 21b) of the mirror to ensure by refraction a modification of the generated beam, characterized in that at least one diopter (40a, 40b) comprises an interior surface (41a, 41b) generally cylindrical whose axis is located in the vicinity an optical axis (A) of the mirror itself passing in the vicinity of the source (10), and an outer surface (42a, 42b) whose inclination relative to the inner surface varies gradually so as to define by refraction a progressive defocusing of the source both in horizontal direction along said optical axis and in vertical direction above and below the optical axis, and in ensuring an offset of the images of the source essentially in lateral direction only, and in that e the or each diopter has a limited angular extent so as to be interposed between the source and only a lateral zone (21a, 21b) of the mirror. Projector according to claim 1, characterized in that the internal surface (41a, 41b) of the or each diopter is cylindrical of revolution. Projector according to one of claims 1 and 2, characterized in that it comprises two identical diopters (40a, 40b) capable of being interposed on either side of the source (10). Projector according to one of claims 1 to 3, characterized in that in the horizontal direction, the or each diopter (40a, 40b) provides a defocusing which decreases gradually from its region near the bottom of the mirror to its region distant from the bottom of the mirror. Projector according to claim 4, characterized in that the mutual inclination of the inner and outer faces (41a, 41b; 42a, 42b) of the or each diopter, in a horizontal plane passing through the optical axis, decreases substantially linearly in function of the dimension (x) along said optical axis (A). Projector according to one of the preceding claims, characterized in that in the vertical direction, the defocusing is minimal, preferably zero, in a horizontal plane passing through the optical axis to reach two maxima at the upper and lower ends of each diopter ( 40a, 40b). Projector according to one of claims 1 to 6, characterized in that the or each diopter (40a, 40b) is truncated (43a, 43b) at its end remote from the bottom of the mirror, so as to leave a marginal part of the mirror exposed directly at the source whatever the position of the diopter. Projector according to claim 7, characterized in that the or each diopter is truncated by a generally conical surface (43a, 43b) centered on the optical axis.

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