EP0966633A1

EP0966633A1 - Elliptical headlight for motor vehicle

Info

Publication number: EP0966633A1
Application number: EP99900505A
Authority: EP
Inventors: Denis Saladin
Original assignee: Valeo Vision SAS
Current assignee: Valeo Vision SAS
Priority date: 1998-01-09
Filing date: 1999-01-08
Publication date: 1999-12-29
Anticipated expiration: 2019-01-08
Also published as: US6431736B1; FR2773604B1; EP0966633B1; ES2587134T3; FR2773604A1; JP2001515649A; WO1999035438A1

Abstract

The invention concerns a headlight capable of generating a light beam of predetermined configuration, comprising a light source (10), an elliptical mirror (20) in the proximity of a first focal point of which is located the light source, a lens (40) placed in front of the mirror. The invention is characterised in that the mirror comprises at least two zones located side by side and capable of forming in a focal region of the lens hot spots preformed in width, and the spots mutually overlap in a horizontal direction. The invention is applicable to beams, in particular low beams, in motor vehicles.

Description

Projector of the elliptical type for a motor vehicle.

The present invention relates generally to headlamps of the elliptical type for motor vehicles. A projector of this kind generally comprises a mirror having a first focus area in the vicinity of which is placed a light source and a second focus area in the vicinity of which the radiation of the source is concentrated after reflection by the mirror. A lens, typically a convex plane spherical lens, is focused in the vicinity of the second focal area and projects this concentrated radiation onto the road.

It is also conventional to provide in the second focal area a screen intended to obscure part of the radiation and whose upper edge defines, in the beam formed, a clear cut, so as to obtain a cut beam, in particular a passing beam .

While these known projectors conventionally had a mirror in the shape of an ellipsoid of revolution, with first and second point focal points, the Applicant recently proposed to modify such a mirror to generate, in the focal plane of the lens, a spot of light concentrated pre-spread in width, so as to give the projected beam the required width. In this way, the use of optical elements (striations, prisms, etc.) of lateral spreading of light is substantially limited, such elements being always difficult to implement in a projector of the type with projection of a bright image of a projector of the elliptical genus.

Document FR 2 704 044 describes such a modified mirror. However, the mirror described in this document still has certain limitations. In particular, the very nature of the mirror leads to a beam which photometric study shows that it can be improved.

It is useful to recall here that a satisfactory passing beam, that is to say giving the maximum visual comfort to the driver while respecting the regulations in force, must include a spot of relatively sharp concentration either in the axis of the road, either slightly offset laterally down the aisle

(i.e. to the right for a right-hand traffic direction), and must also have a relatively uniform light over a certain width on either side of the concentration spot, with a relatively regular transition between the spot of concentration and the light spread out. In particular, it is desired to avoid the presence of sudden stops in the beam, that is to say the excessively rapid reduction in intensity at the lateral edge of the beam.

However, the mirror of the aforementioned type generally leads to a beam having a concentration zone of excessive width and as a corollary of insufficient light intensity. Another limitation of this known headlight is that the beam may have an insufficient thickness, that is to say have a high concentration of light just under the cut, but insufficiently illuminate the road closer to the vehicle.

Furthermore, the beams generated by the headlamps of the aforementioned type generally have a relatively reduced thickness, and in any case difficult to control, whereas it is rather desirable to have, at least in the case of a passing beam, a beam which has a substantial thickness towards the sides, and which at the same time does not generate excess light in the center line of the vehicle and too close to it.

The present invention aims to overcome these limitations of the state of the art and to provide a projector of the aforementioned type, in which the beam obtained is improved.

Another object of the present invention is to give the designer great flexibility in obtaining different characteristics of the beam, such as width and intensity of the concentration spot, evolution of the intensity towards the lateral edges of the beam.

Another object finally of the present invention is to provide a projector in which the thickness of the beam generated can be controlled more easily and with more flexibility during the design. Thus the invention provides a motor vehicle headlamp, of the type capable of generating a light beam of given configuration and comprising a light source, a mirror of the elliptical type in the vicinity of a first focus of which the light source is located, a lens placed in front of the mirror, characterized in that the mirror comprises at least two zones situated side by side and capable of forming in a focal region of the ^' lens light spots preformed in width, and in that the spots overlap each other in a direction horizontal.

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

each zone of the mirror has a surface having a horizontal generator such that the rays which it reflects from the rays coming from the source extend in vertical planes which intersect an imaginary line at points whose curvilinear abscissas evolve on this line according to a predetermined law. - said imaginary lines of the different zones are continuous. said imaginary lines of the different zones are curves.

Each curve is all the more distant from the focal region of the lens, in a direction parallel to the axis of the mirror, that said curve is laterally distant from said axis.

in each zone of the mirror, a vertical section of said mirror situated in a vertical plane containing the rays reflected by the horizontal generator is capable of concentrating said rays reflected on said associated point of the imaginary line, said imaginary line being a line of secondary focal points , and said points being secondary foci.

- In at least part of one of the zones, an upper region of a vertical section is able to concentrate the rays which it reflects on another point situated between said associated secondary focal point and the lens.

- on either side of a transition line between two adjacent areas, the vertical sections of said areas have non-overlapping secondary hearth lines. said transition line is determined by the intersection of the surfaces of said zones, and said transition line is distinct from respective horizontal isodeviation lines of said zones.

- The mirror has two zones separated by a transition line extending substantially in the middle of the mirror in the horizontal direction. the mirror has three zones separated by two transition lines extending on either side of the axis of the mirror.

- A central area of the mirror is substantially narrower, in the horizontal direction, than two lateral areas.

- The projector further comprises a mask located in the focal region of said lens, so as to generate a cut beam.

- Said lines of secondary focal points are located, in an axial direction, between the mask and the lens.

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 example and made with reference to the accompanying drawings, in which: FIG. 1 illustrates by a partial schematic view in horizontal section the principle of construction of a zone of the mirror of a projector according to the invention, FIG. 2 illustrates by a partial schematic view in vertical section a first method of construction of the vertical sections from the mirror, FIG. 3 illustrates by a partial schematic view in vertical section a second mode of construction of the vertical sections of the mirror, FIG. 4 is a partial schematic view in horizontal section of a projector according to a first concrete embodiment of the invention,

- Figures 5a and 5b illustrate by sets of isocandela curves the light distribution of the beam portions generated by two individual regions of the projector mirror of Figure 4, Figure 6 illustrates by a set of isocandela curves the light distribution of the beam overall obtained, FIG. 7 is a partial schematic view in horizontal section of a projector according to a second embodiment of the invention,

- Figures 8a to 8c illustrate by sets of isocandela curves the light distribution of the beam parts generated by three individual regions of the mirror of the projector of Figure 7, and Figure 9 illustrates by a set of isocandela curves the light distribution of the beam overall obtained.

Referring firstly to FIG. 1, there have been shown diagrammatically elements of a headlamp according to the invention, which comprises a light source 10, a mirror 20, a screen or masking mask 30 and a lens 40.

The source 10 is typically the filament of an incandescent lamp or the arc of a discharge lamp. The mask 30 has, for example, in a conventional manner per se, an upper edge defined by two segments of lines defining together in an inverted and flattened "V", so as to generate a passing beam conforming to European regulations on the subject.

The lens 40 is for example a planar / convex spherical lens, with a point focus, or even a toric lens.

The mirror is constructed according to principles similar to those described in the document FR 2 704 044, to which reference will be made for more details, with differences with respect to these principles as will be explained below.

First of all, and as will be seen in more detail below, the mirror consists of at least two zones constructed individually and connecting according to slightly angled transition lines generally extending from top to bottom.

Each of these zones is constructed as will be described below.

We start by defining a horizontal generator GH similar to that described in FR 2 704 044, which is illustrated by the fact that a ray FIG emitted by the source in the direction of the reflecting surface of the area to be constructed, at its level. horizontal generator, will be reflected in a radius GF2 which will cut a line of secondary focal points LFS at a point F2 whose position, or curvilinear abscissa, on the line LFS varies according to the angle α of the radius FIG with respect to l optical axis xx. We could easily demonstrate that this amounts to using a horizontal generator whose equation is given at the bottom of page 8 of the document FR 2 704 044 mentioned above.

A difference compared to the teachings of this document is that the LFS line also makes it possible to control the focusing of the section of the mirror located in the vertical plane containing the reflected ray GF2.

It will be observed here that the line LFS can be any curve, preferably without discontinuity so as to avoid discontinuities in the generated surface.

In the basic embodiment illustrated in FIG. 2, the whole of this section is able to focus the rays reflected by it on the point F2, the distance of which, measured along the axis xx, from the plane of the mask 30 can vary significantly along the LFS curve.

Each of these sections is therefore an elementary section of ellipsoid of revolution having foci FI and F2, and the parameters of this ellipsoid vary as the point F2 moves along the curve LFS. It is understood here that the profile of the aforementioned LFS curve makes it possible to control not only the width of the light spot which will be formed in the plane of the mask 30, but also the thickness of this light spot, this being all the more more important than the point F2 is distant in front of the mask 30.

FIG. 3 illustrates an alternative embodiment of certain vertical sections of the mirror 20, according to which a part 20 ′ of the section illustrated in this figure exhibits the same behavior as in the case of FIG. 2, that is to say concentrates the radiation reflected on the point F2, while an upper part 20 '' of this section will concentrate the reflected radiation at a point F2 'distant from F2 towards the front, i.e. towards The lens. This also has the result of thickening at will the light spot in the plane of the mask 30, and therefore the thickness of the projected beam.

It will be observed here that the reflective surfaces giving the optical behaviors corresponding to FIGS. 2 and 3 can be easily deduced from the surface equation given on page 9 of FR 2 704 044.

It being recalled here that the surface design described above applies to one of two or more zones, the mirror 20 is then defined by designing a first zone characterized by a certain LFS curve and a certain rule for the evolution of the position. points F2 on this line as a function of the angle a of the rays emitted by the source, and at least a second zone characterized by another rule for changing the position of points F2, and if necessary by another line LFS whose trajectory is different from that which corresponds to the first zone.

In addition, and according to an important characteristic of the invention, the rules for changing the positions of the points F2 between an area of the mirror and an adjacent area are such that there is an overlap, in the width direction, between the radiation produced in the plane of the mask 30 by an area and the radiation produced in this same plane by the adjacent area. This is achieved by designing the evolution rules for F2 points on the respective LFS lines of such that, for respective determined fractions of the first and second zones which are adjacent to the transition between the two zones, the horizontal angular intervals covered by the radiation reflected by these fractions of zones overlap. It is easily understood that, in this way, there will exist at the border between these two areas a slight bend, that is to say a non-differentiability, between the adjoining reflecting surfaces.

Furthermore, to ensure a transition between two adjacent zones which preferably extends substantially vertically, the parameters of the reflective surfaces of the two zones, defined essentially by the trajectory of the respective LFS curves and by the rules of evolution F2 = f (α) on these curves, are chosen so as to obtain this kind of transition. This implies in particular that the axial positions of the respective LFS curves with respect to the plane of the mask 30 must be reasonably close to one another as regards the fractions of zones whose fields, in terms of horizontal deviation, overlap.

FIG. 4 schematically illustrates a first concrete embodiment of a mirror of a projector according to the invention, with two zones 20a and 20b designed as described above and which are separated by a transition edge 21 which extends noticeably in the middle of the mirror.

FIGS. 5a and 5b illustrate the beam portions projected by the lens 40 from the light spots formed respectively by these two zones, and with the intervention of the mask 30. It is observed that the portion of the beam generated by the area 20a in combination with the mask 30 and the lens 40 (FIG. 5a) projects substantially to the right with respect to the central vertical axis of the projection screen and that, in the in the opposite direction, the part of the beam generated by the area 20b in combination with the mask 30 and the lens 40 (FIG. 5b) projects substantially to the left relative to the central vertical axis of the screen.

It is also observed that these overflows of the respective beam portions do not present sudden stops of light, but on the contrary that the quantity of light gradually decreases, as evidenced by the spacing between the isocandela curves represented. It will be noted here that this absence of sudden stops is obtained when the transition edge between the two zones 20a and 20b does not follow a line of horizontal isodeviation of the light, that is to say will not be superimposed on a line of each zone which would give the same horizontal deviation to the reflected rays. Typically, this is obtained by giving the LFS curves of the two zones different axial positions in the vicinity of their parts affected by the rays reflected by regions of the zones 20a, 20b adjacent to the border 21, and by determining the line 21 as being the line of intersection between the two surfaces thus defined. In this way, the two beam parts will merge into a global beam (Figure 6) which has excellent homogeneity, as well as a concentration in the axis which is both marked and both gradually merges with the wider parts of the beam. FIG. 7 illustrates a second embodiment of a projector mirror according to the invention. This time it comprises ^" three zones, with two lateral zones 20a, 20b separated by a substantially narrower central zone. Here again, the parameters used when designing the individual surfaces are such that the two transition lines 21 and 22 between the adjacent zones do not correspond to horizontal isode-deflection lines, so that the three corresponding beam parts, as illustrated in FIGS. 8a, 8b and 8c respectively, have lateral edges with progressive fading of the light This results in a fusion of these beam parts to form a homogeneous overall beam, which has the same qualities as in the case of FIG. 6, with however a higher level of central concentration.

It is understood here that by playing on the width of the zone 20c and on the lateral spreading (and if necessary on the thickening) which it achieves, makes it possible to modulate the appearance of the beam with great flexibility.

Of course, the present invention is not limited to the embodiments described and shown, but the skilled person will be able to make any variant or modification according to his spirit. In particular, it is understood that a projector mirror according to the invention can be subdivided into as many zones as necessary, so as to be able to model the beam as a function of the objectives in terms of photometry both in regulatory terms and in terms of comfort plan visual.

It is also understood that the invention applies to obtaining any type of beam, limited or not by a cut (the mask 30 being absent in the latter case).

Finally, it is important to note here that the invention is fundamentally different from the case where two light spots formed by two different zones of the same reflector, for example ellipsoidal, overlap by virtue of the fact that the light source is not punctual, but covers all cases where the overlap between these light spots goes beyond the overlap, which is, moreover, uncontrolled, which would be obtained with conventional surfaces.

Claims

1. Motor vehicle headlamp, of the type capable of generating a light beam of given configuration s and comprising a light source (10), a mirror (20) of the elliptical type in the vicinity of a first focus of which the light source is situated , a lens (40) placed in front of the mirror, characterized in that the mirror comprises at least two zones (20a, 20b; 20a, 20b, 20c) o located side by side and capable of forming in a focal region of the lens luminous spots preformed in width, and in that the spots overlap each other in a horizontal direction.

2. Projector according to claim 1, characterized in that each zone (20a, 20b; 20a, 20b, 20c) of the mirror has a surface having a horizontal generator (GH) such that the rays (GF2) that it reflects at from the rays (FIG) from the source (10) extend in vertical planes which intersect an imaginary line (LFS) at 0 points (F2) whose curvilinear abscissas evolve on this line according to a predetermined law.

3. Projector according to claim 2, characterized in that said imaginary lines (LFS) of the different zones are continuous. 5

4. Projector according to claim 2, characterized in that said imaginary lines (LFS) of the different zones are curves.

5. Projector according to claim 4, characterized in that each curve (LFS) is all the more distant from the focal region of the lens, in a direction parallel to the axis (xx) of the mirror (20), that said curve is laterally distant from said axis.

6. Projector according to claim 2, characterized in that in each zone of the mirror, a vertical section of said mirror located in a vertical plane containing the ray (GF2) reflected by the horizontal generator (GH) is capable of concentrating said reflected rays on said associated point

(F2) of the imaginary line, said imaginary line being a line of secondary foci (LFS), and said points (F2) being secondary foci.

7. Projector according to claim 6, characterized in that, in at least part of one of the zones, an upper region (20 '') of a vertical section is capable of concentrating the rays which it reflects on a another point (F2 ¹ ) located between said associated secondary focus (F2) and the lens (40).

8. Projector according to claim 6, characterized in that, on either side of a transition line (21; 21, 22) between two adjacent areas, the vertical sections of said areas have secondary focal lines (LFS ) not superimposed.

9. Projector according to claim 8, characterized in that said transition line (21; 1, 22) is determined by the intersection of the surfaces of said zones, and in that said transition line is distinct from lines of horizontal isodeviation respective of said zones.

10. Projector according to claim 1, characterized in that the mirror has two zones (20a, 20b) separated by a transition line (21) extending substantially in the middle of the mirror in the horizontal direction.

11. Projector according to claim 1, characterized in that the mirror has three zones (20a, 20b, 20c) separated by two transition lines (21, 22) extending on either side of the axis ( xx) of the mirror.

12. Projector according to claim 11, characterized in that a central zone (20c) of the mirror is substantially narrower, in the horizontal direction, than two lateral zones o (20a, 20b).

13. Projector according to claim 1, characterized in that it further comprises a mask (30) located in the focal region of said lens (40), so as to generate a cut beam.