FR2678353A1 - Headlamp with high luminous intensity and very sharp cut-off - Google Patents

Abstract

The invention relates to a headlamp for a motor vehicle, characterised in that it comprises: a light source (10); a first ellipsoidal reflector (20), a first focus (F1) of which is situated near the source and a second focus (F2) of which is located in front of the source; a mask (30) located in the vicinity of the second focus and having at least one light passage window (32), so as to simulate at least one source of fixed and predetermined geometry; at least two reflecting means (35a, 35b) provided downstream of the said mask and interacting therewith in order to define at least one virtual image source (SI) of the simulated source; a second reflector (40) comprising at least two regions (40a, 40b) homologous (similar) to the said reflecting means.

Description

 The present invention relates generally to a motor vehicle headlamp.

We already know in the prior art, in particular from patents FR-A-2,536,502, FR-A-2,536,503, FR-A-2,583,139, FR-A-2,597,575, FR-A-2 599 120, FR
A-2 599 121, FR-A-2 600 024, FR-A-2 602 306, FR-A-2 609 146, FR-A-2 609 148, FR-A-2 621 679, FR-A- 2,634,003, all in the name of the Applicant, headlamp reflectors which have the common characteristic of forming by themselves images of the filament, the position of which on a projection screen is well determined as a function of a particular photometry sought, and especially in relation to a cut-off which the type of beam considered must respect.

 To give satisfactory results, such reflectors must cooperate with a light source whose geometry is sufficiently well defined and whose size is not excessive.

 In the case where the light source is an incandescent filament, the contour of the emission is in close correlation with the physical configuration of the filament, and this is generally established in a reproducible manner from one lamp to another, and with satisfactory accuracy. Thus there is shown in Figure 1a of the drawings, by a series of isoluminance curves, the diagram of the light emission of such a filament, in the general shape of a right cylinder.

 But there are certain types of lamps whose geometry of the light emission does not have these qualities. It can be first of all filament lamps in which, for example for reasons related to manufacturing, the filament has either a shape or a position which can vary appreciably from one lamp to another, or even a poorly defined geometric shape, for example curved.

 They may also be arc lamps, known for their qualities in terms of light output and which we are now seeking to use in motor vehicle headlamps. This type of lamp indeed has a configuration of light emission whose contours vary widely, either from one lamp to another, or within the same lamp depending on the state thereof (heating phase or steady state), and moreover the contours of the emission configuration of such a lamp are extremely diffuse and make it difficult to obtain a cut of good sharpness.

 Is shown in Figure lb of the drawings the light emission of an arc established between two electrodes. The "equivalent filament" is also represented by a dashed rectangle, constituting the ideal light emission zone. One can observe that a very intense light radiation is emitted by zones located relatively far from the ideal rectangle, these malformations being translated by similar malformations at the level of the images of this source after reflection by the reflector.

 Thus a reflector of the type indicated above will generate images of such a source whose position, in particular with respect to a cut, will be more random.

This results in particular in the risk that certain images of the source overflow substantially above the cutoff, with consequently a dazzling of drivers of vehicles traveling in the opposite direction.

 Another drawback of a discharge lamp is that, regardless of the geometry of the source, its luminance can prove to be excessive and here again cause discomfort for drivers of vehicles traveling in the opposite direction.

 The present invention aims to overcome these drawbacks of the prior art and to propose a headlamp which makes it possible to use, with reflectors of the type defined above, a source whose geometry can be poorly defined, without however the quality of the beam. obtained light is noticeably degraded.

 Another object of the invention is to allow the reflector forming the actual beam to work from a source whose effective dimensions or luminance are limited.

To this end, it relates to a headlamp, in particular for a motor vehicle, characterized in that it comprises:
- a light source,
a first reflector, of the ellipsoidal type, of which a first focal point is located in the vicinity of the source and of which a second focal point is located in front of the source, and defining an optical axis,
a mask situated in the vicinity of the second focal point and having at least one window for the passage of light so as to simulate at least one source of fixed and predetermined geometry,
at least two reflecting means provided downstream of said mask and cooperating with it to define at least one virtual image source of the simulated source,
a second reflector comprising at least two homologous areas of said reflecting means and the surface of which determines by itself the position of the images of the virtual source or sources as a function of a determined photometry, and
- a closing window.

Other aspects, aims and advantages of the present invention will appear better on reading the following detailed description of a preferred embodiment thereof, given by way of non-limiting example and made with reference to the accompanying drawings, in which, in addition to the figures la and lb already described,
FIG. 2 is a view in axial horizontal section of a headlight according to a first embodiment of the invention,
FIG. 3 is a partial view in section and in vertical elevation made according to arrows III-III of FIG. 2,
FIG. 4 illustrates the outline of an image projected by the projector of FIG. 2,
FIG. 5 represents images projected on a projection screen by the projector of FIG. 2,
FIG. 6 is a view in axial horizontal section of a headlight according to a second embodiment of the invention,
FIG. 7 is a view in section and in vertical elevation made according to the arrows VII-VII of FIG. 6,
FIG. 8 represents images projected on a projection screen by the projector of FIG. 6,
FIG. 9 is a view in axial horizontal section of a headlight according to a third embodiment of the invention,
FIG. 10 is a view in section and in vertical elevation made according to the arrows XX of FIG. 9, and
Figure 11 is an axial horizontal sectional view of a projector according to a fourth embodiment of the invention.

 It will first be indicated that, from one figure to another, identical or similar elements or parts are designated by the same reference numbers.

 Referring firstly to FIGS. 2 and 3, a motor vehicle headlight according to the present invention firstly comprises a substantially elongated light source, schematically indicated in 10.

 It can be, for example, an incandescent filament, the contours of which are ill-defined as indicated above, or else an arc generated within a discharge lamp.

 The projector further comprises a first reflector 20, which is generally ellipsoidal in shape and which is characterized by its two foci F1 and F2. The first focal point F1 is located approximately in the center of the source 10, the focal point F2 being located further forward.

 The major axis of the ellipsoid extends essentially horizontally and defines the optical axis xx of the projector. Furthermore, although it can be seen in FIG. 2 that the major axis of the ellipse is parallel to the longitudinal direction of the source, this arrangement is entirely optional, the source possibly being for example perpendicular to the major axis (case of '' a transverse filament lamp).

 A mask or mask 30 is interposed on the path of the light rays reflected by the first reflector 20, extending in a plane perpendicular to the optical axis and passing over or in the vicinity of its second focal point F2. This mask has a window 32 which appears more clearly in FIG. 3. This window has the form of a notch delimited by a horizontal lower edge and by two lateral edges, preferably vertical and parallel. It is positioned so that the focal point F2 is located on its vertical center line, and preferably substantially at the center of the horizontal bottom wall.

 The mask 30 thus behaves like a source whose lower emission contours and lateral ends are well defined, and in particular whose lower emission contour is as straight and horizontal as possible.

 In front of the mask 30 are provided two plane mirrors 35a, 35b which extend vertically with a determined inclination relative to the optical axis xx, symmetrically on either side thereof.

The inclination is preferably close to 450.

 The rearmost end edges of the two mirrors meet at a vertical edge located in the immediate vicinity of the plane of the mask 30 and the vertical center line of the window 32.

 In this way, the simulated source defined by the window 32 comprises a first lateral half which will cooperate exclusively with the mirror 35a and a second lateral half cooperating exclusively with the mirror 35b, to jointly define a virtual image source SI located on the axis xx and extending from the aforementioned edge, towards the front, over a length equal to the half-width of the window. This image source has a horizontal and sharp lower edge; it emits laterally across the solid angle covered by the mirrors.

The projector also comprises a second reflector 40. This reflector 40 is intended to form the light beam of the projector from the radiation reflected by the mirrors, seeming to come from the source.
IF. To this end, it comprises two parts 40a and 40b located side by side and respectively associated with the radiation reflected by the mirrors 35a and 35b. The reflector 40 can be designed in accordance with the teachings of any of the French patents cited in the introduction - the contents of which are incorporated into the present description by reference - to generate by itself a light beam of suitable configuration, and for example a passing beam delimited by a so-called "V" cut, in accordance with European regulations.

 It will simply be recalled that this kind of reflector is capable of forming images of the light source with which it cooperates, which are all located essentially for example below a given cut-off, the highest points of these images. being located in the vicinity of said cut. And an essential condition for this kind of reflector to be able to give the expected results is that the particularly lower limit of the source from which it works is geometrically well defined, which is obtained in the present invention thanks to the mask 30.

 It can be observed here that, by nature, a reflector of the ellipsoidal genus such as the reflector 20 produces at its second focal point, due to the non-negligible dimensions of the real source 10, a light spot whose dimensions are large, typically with greater large dimension of the order of 20 to 25 mm. The projector constructed according to the present invention, thanks to the separation into two of the simulated source available at the output of the mask 30, the size of which is also large, allows the reflector 40 to work on images whose surface is half as large which in particular makes it easier to obtain a beam whose width is not excessive and whose spot of concentration in the axis has sufficient intensity. FIG. 4 illustrates the basic outline of the images produced by the spotlight of the invention, a contour which corresponds to that of a lateral half of the radiation emanating from the window 32.

 In order to avoid the formation of stray reflections on one side or the other of the mask 30, and therefore the deterioration of the beam, this mask is preferably non-reflective on each of its faces. It can for example be covered with a matt black coating.

 Finally, the headlamp comprises a closing glass 50, which comprises, if necessary, in a conventional manner, deflecting streaks or prisms capable of modifying the light distribution of the beam without altering the cut defined by the reflector.

 Thanks to the present invention, variations in the light emission configuration of the real source 10 are avoided, either when the lamp is replaced or when it is warmed up. Furthermore, the use according to the invention of a first reflector of the ellipsoidal type allows excellent recovery of the light flux emitted by the source, and the positioning of the first reflector behind the second reflector avoids increasing the lateral bulk of the projector for a given useful emission surface.

 FIG. 5 illustrates, in a standardized projection plane on which the standardized European cut h'Hc has been represented, a certain number of images I whose contours correspond, to a uniformity and to a rotation close, to that of the figure 4.

 It can be observed that the rotation imparted by the reflector to the images is such that the ill-defined edge of each image is in all circumstances far from the cut; it therefore does not risk disturbing the formation thereof; more precisely, it is only the three well-defined edges of the virtual source and of its images which generate the cut, and the latter therefore remains extremely clear.

 Figures 6 and 7 illustrate a second basic embodiment of the present invention. The mask 30 comprises two windows 32a, 32b, namely a substantially rectangular lower window 32b and an upper window 32a delimited only by a horizontal lower edge and two vertical lateral edges and aligned with those of the lower window 32b. The two windows are separated by an interval of reduced thickness, in order to minimize the amount of radiation obscured by the mask. As a corollary, the two mirrors 35a and 35b are arranged one above the other, at levels homologous to the two windows. In this case, the mirror 35a extends vertically at around 450 with respect to xx, forward from the right side edge (bottom in Figure 6) of the window 32a, so as to reflect the radiation towards the area 40a of the reflector 40, while the mirror 35b extends vertically to approximately 45 relative to xx, forward from the left lateral edge of the window 32b to reflect the radiation towards the area 40b of the reflector. The mirror 35a is limited at the bottom and the mirror 35b is limited at the top by a horizontal plane passing in the vicinity of the zone of thin thickness of the mask which performs the separation between the windows 32a and 32b.

 In this way, the mirror 35a creates from the radiation passing through the window 32a a virtual image source SIa located at least approximately on an axis xxa parallel to xx and offset to the right with respect thereto, and whose lower limit and the lateral limits are geometrically well defined. The mirror 35b creates, for its part from the radiation passing through the window 32b, a virtual image source SIb located at least approximately on an axis xxb parallel to xx and shifted to the left relative to the latter, and whose set of limits (rectangular outline) are well defined.

 In this way, and now with reference to FIG. 8, the zone 40a of the reflector 40 forms images Ia whose contours correspond, to a homothety and to a rotation close, to those of the zone Za of FIG. 7, while zone 40b forms images Ib whose contours correspond to those of zone Zb in FIG. 7.

 The areas 40a and 40b of the reflector are designed individually, preferably using the teachings of the above-mentioned French patents, on the basis of respective main axes which are the axes xxa and xxb. It will be observed here that, for for reflectors which require that the source is delimited at the bottom by a plane passing through the main axis considered, the axes xxa and xxb are offset in height by being situated respectively at the height of the base of the window 32a and at the height of the base of window 32b, as illustrated in FIG. 7, the traces of these axes.

 The embodiment which has just been described retains the advantages of that of FIGS. 2 and 3 in particular as regards the reduction of the source surface from which the zones 40a and 40b of the reflector work, but in this case, it is a separation by a horizontal line. In this regard, it will be noted that the windows 32a and 32b are designed so that the zones Za and Zb have luminances or neighboring surfaces.

 Referring now to Figures 9 and 10, there is shown a code / route projector which comprises elements 10, 20, 30, 35a, 35b and 40 substantially identical to those of Figure 2. These elements constitute together, and with the glass not shown, a dipped headlight which forms a beam delimited at the top by an appropriate cut-off. There is further provided a second light source 60 (filament lamp or discharge lamp) which cooperates with a reflector of the elloipsoidal type 70 and with two other plane mirrors 80a, 80b. The source 60 is located on the optical axis xx, in front of the mirrors 35a, 35b, on the first focal point F3 of the reflector 70. The latter is positioned so as to direct the flux emitted by the source 60 towards the rear in the direction mirrors 80a and 80b. These are positioned in the vicinity of the second focus F4 of the reflector, are oriented vertically and are inclined at an angle of approximately 450 relative to the axial vertical plane of the projector, away from the optical axis. rearward.

 FIG. 10 shows that the two mirrors 35a, 35b are situated at a height homologous to that of the window 32 of the mask 30, while the mirrors 80a, 80b are located below the mirrors 35a, 35b. The flux recovery reflector 70 is designed so that the majority of the radiation emitted towards the region of its second focus hits one or other of the mirrors 80a, 80b.

Furthermore, it can be seen in FIG. 10 that, in the region of the mirrors 35a, 35b which is situated behind (with respect to the general direction of emission of the projector) of the mirrors 80a, 80b, said mirrors 35a, 35b can be extended as desired downwards, as illustrated by the dashed lines, in order to recover the flow leaving the window 32 in the plunging direction and to return it to the reflector 40.

 The assembly constituted by the source 60, the reflector 70, the mirrors 80a, 80b, the reflector 40 and the glass can be arranged to constitute either a full-fledged main beam, in which case the passage of code en route and vice versa. 'Carry out by alternately switching on the sources 10 and 60, ie a beam complementary to the passing beam generated by the elements 10, 30, 35a, 35b, 40 and 50 to form in conjunction with it the driving beam. In this case, the passage of code en route and vice versa takes place by switching the source 60 on and off, the source 10 remaining permanently on.

 If necessary, and in particular in the latter case, it is also possible to interpose between the reflector 70 and the mirrors 80a, 80b a mask whose window is configured as a function of the desired objective, in particular for simulating a source whose limit in particular is upper geometrically well-defined.

 An advantage of the embodiment of FIGS. 9 and 10 resides in that the reflector 70 forms a mask of direct light with respect to the sources 10 and 60.

 Referring now to Figure 11, there is shown another embodiment in which the mirrors 35a, 35b are replaced by a prism 90 located immediately in front of the mask 30. This prism comprises a first face 90a (entry face) located in a vertical plane and oriented at approximately 45 relative to the axis xx. This face extends forward from the left end edge of the window 32 of the mask 30. It is designed (by an appropriate choice of the nature of the prism material and of the orientation of the face) for that about half of the incident radiation is reflected, the other half entering the prism with refraction.

 The prism further comprises a total reflecting face 90b and an exit face 90c, designed such that all of the refracted radiation at 90a leaves the prism through the face 90c in a general lateral direction, after total reflection on the face. 90b.

The reflection on the face 90a creates a virtual image source SIb of the simulated source created by the window 32, which is located on an axis xxb shifted to the left relative to the central axis xx and which extends forward essentially from the left side edge of the window. The refraction on the input and output faces 90a, 90c and the total reflection on the face 90b create a virtual image source SIa which is located on an axis xxa shifted to the right with respect to the axis xx and which s' extends substantially in front of the plane of the mask 30,
The areas 40a and 40b of the reflector 40 are designed as a function of the position and the size of these virtual sources, to generate the desired beam.

 A particular advantage of this embodiment is that the luminance of the sources SIa and SIb from which the two homologous areas of the reflector work is reduced by half compared to the luminance of the radiation passing through the window 32. This thus decreases risks of dazzling drivers of oncoming traffic.

 Of course, the present invention is in no way limited to the embodiments 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 flux recovery reflector 20, described in the foregoing as being in the general shape of an ellipsoid, can be replaced by any other reflector capable of giving from the flux emitted by the source an appropriate flux concentration where the we will put the mask 30.

Claims (10)

 1. Headlamp, in particular for a motor vehicle, characterized in that it comprises:  - a light source (10),  - A first reflector (20), of the ellipsoidal kind, of which a first focal point (F1) is located in the vicinity of the source and of which a second focal point (F2) is situated in front of the source, and defining an optical axis (xx) ,  a mask (30) located in the vicinity of the second focal point and having at least one window (32; 32a, 32b) for the passage of light so as to simulate at least one source of fixed and predetermined geometry,  - at least two reflecting means (35a, 35b; 90) provided downstream of said mask and cooperating with it to define at least one virtual image source (SI; SIa, SIb) of the simulated source,  - a second reflector (40) comprising at least two zones (40a, 40b) homologous to said reflecting means and the surface of which determines by itself the position of the images (I; Ia, Ib) of the virtual source or sources as a function of '' a determined photometry, and  - a closing glass (50).  2. Projector according to claim 1, characterized in that the light source (10) is the arc of a discharge lamp.  3. Projector according to claim 1 or 2, characterized in that the mask (30) comprises a single window (32) and in that the reflecting means comprise first and second plane mirrors (35a, 35b) extending in essentially vertical planes from a vertical line passing on the optical axis and substantially in the middle of the window, with an inclination of approximately 450 on either side of the optical axis (xx), so as to create a single virtual source (SI) with an area equal to approximately half that of the simulated source and located on said optical axis  4.Projector according to claim 1 or 2, characterized in that the mask (30) comprises a single window (32) and in that the reflecting means comprise a prism (90) comprising an entry face (90a) semi reflecting, situated in a vertical plane and extending from the vicinity of a lateral edge of the window with an inclination of about 450 with respect to the optical axis, a face of total reflection (90b) and a face of output (90c), refraction on the input and output faces and reflection on the total reflection face generating a first virtual source (SIa), and reflection on the input face generating a second virtual source (SIb) ), said virtual sources having a luminance equal to approximately half that of the simulated source.  5. Projector according to claim 3 or 4, characterized in that the window (32) is defined by a notch formed in the mask and delimited by a substantially horizontal bottom edge and two essentially vertical side edges.  6. Projector according to claim 1 or 2, characterized in that the mask comprises two windows (32a, 32b) located one above the other and in that the reflecting means comprise two plane mirrors (35a, 35b) respectively associated with the two windows and extending in essentially vertical planes at the height of the said windows, each plane mirror extending forwards, with an inclination of approximately 450 relative to the optical axis (xx), from a respective lateral edge of the associated window, thus defining two virtual sources (SIa, SIb) located on either side of the optical axis and whose height is less than that of the simulated source.  7. Projector according to claim 6, characterized in that the two windows include a lower window (32b) in the general shape of a rectangle whose large dimension is horizontal, and an upper window (32a) in the general shape of a notch delimited by a substantially horizontal bottom edge located in close proximity to the top edge of the bottom window and two essentially vertical side edges aligned with the side edges of the bottom window.  8. Projector according to claim 3, characterized in that the second reflector (40) is capable of generating a passing beam delimited by an upper cut and in that it further comprises:  - a second light source (60) located in the vicinity of the optical axis,  a third reflector (70), of the ellipsoidal genus, of which a first focal point (F3) is situated in the vicinity of the second source and of which a second focal point (F4) is situated behind the second source,  - at least two other reflecting means (80a, 80b) provided in the vicinity of the second focal point of the third reflector for directing the radiation reflected by the third reflector towards the second reflector (40) and generating a driving beam or a beam complementary to the beam crossing.  9. Projector according to claim 8, characterized in that the other two reflecting means comprise third and fourth plane mirrors (80a, 80b) generally located above the first and second plane mirrors (35a, 35b) and in essentially planes verticals which respectively intersect the planes of the first and second plane mirrors along vertical lines, and in that the first and second plane mirrors, behind said straight lines, are extended downward to recover the plunging radiation passing through the window (32 ).  10. Projector according to one of claims 1 to 9, characterized in that the second reflector (40) has a reflecting surface which generates images of the virtual source or sources whose highest points are located in the immediate vicinity of a cut.