FR2583499A1 - MOTOR VEHICLE PROJECTOR WITH BEAM VARIATION - Google Patents

Abstract

THE INVENTION RELATES TO AN AUTOMOBILE HEADLIGHT OF THE TYPE INCLUDING AT LEAST ONE REFLECTOR 10, 20, 30A-30B, 34A-34B, 40-50 COOPERATING WITH A SINGLE LIGHT SOURCE 11; 23; 33; 42. IT IS CHARACTERIZED BY THE FACT THAT IT INCLUDES AN OCCULTATION SCREEN 15, 25, 36, 45 INTERPOSED ON THE PATH OF THE LIGHT RAYS AND INCLUDING AT LEAST ONE OCCULTATION ZONE CONSTITUTED OF LIQUID CRYSTALS LIKELY TO CONFERENCE IN THIS ZONE OF OCCULTATION SEVERAL STATES OF TRANSPARENCY.

Description

The present invention relates to automobile projectors capable of

to issue a

  variable light beam, and in particular

  may emit either a beam of

  long range, for example a beam of

  route, ie a cut beam, for example a

cross-hatch.

  It has already been proposed

  mobile road / crossing with a simple source

  light (filament) co-operating with occul-

  movers. Such a system is for example described in French Patent 1,296,036. It is unreliable, too sensitive to vibrations, too slow to switch,

  and did not give rise to industrial achievements.

  In the most common automotive technology, road / crossing spotlights include

  a parabolic reflector and a dual light source

  formed by two filaments of tungsten.

  For road lighting, one of the filaments cooperates with the entire reflector. For crossover lighting, an occultation screen or an occultation cup cuts the light rays

  emitted by the second filament and arriving on the reflec-

  tor, which sends them back as a cut beam

  crossing. In such a solution, known and useful

  for a long time, the transition from the state of

  rage crossing at the road lighting state, is done by switching the power supply of the filaments. The evolution of automotive technology suggests that such lamps with two tungsten filaments will probably be replaced by gas discharge lamps or arc lamps, the light source thus produced being much brighter than that obtained by filaments of tungsten. This great brilliance is interesting because it will allow the use of projectors of smaller dimensions, and in particular of smaller dimensions.

  height that will fit much more easily

  to the aerodynamic lines of a vehicle.

  However, such new light sources require for each of them a high voltage power supply that

  series with the source a ballast of a relative cost-

  high level. In addition, the transition from a state of enlightenment

  to another must be done as quickly as possible

  possible, and the light sources with

  Zeuse or arc have ignition times too high

  to allow a sufficiently fast switching.

  The present invention generally proposes

  to make a beam projector

  eliminating the disadvantages of earlier projectors

  and by static means, insensitive to vibrations, extremely rapid beam variations under the action of a

  online order. In particular, the invention

  tion proposes a particular implementation

  advantageous of the new light sources mentioned above.

  To do this, the projector according to

  type with at least one reflector

  cooperating with a single light source, is

  characterized in that it includes an occultation screen

  interposed on the path of the light rays and

  carrying at least one occultation zone consisting of liquid crystals capable of conferring on this occultation zone, either a state of transparency or a state of non-transparency, and, more generally,

various states of transparency.

  It is easy to understand that, in the state of transparency, everything happens substantially as if no obstacle was interposed on the path

  light rays, whereas in the state of non-

  transparency, the occultation zone carries out the

pure wanted of the light beam.

  The switching of the liquid crystal zone is preferably obtained by a variation of the electric voltage, this zone being produced in the manner known per se for producing screens.

  passive in the field of digital signage.

  In the simplest embodiment

  ple, the screen has a single occultation zone made of liquid crystals. It is constituted, in

  a preferred example of two glass slides trans-

  between which nematic liquid crystals are arranged in helix in correspondence with the occultation zone. On the outside of the glass slides are arranged two crossed light polarizers. Inside each blade, on the side of

  crystals, are arranged layers or bands

  ultra-thin transparent electrodes.

  As is well known to the liquid crystal specialist, the application or non-application of an electrical voltage to the electrodes results in a torsion variation of the liquid crystals, so that the whole may or may not be traversed by

  the light. The transmission factor of such a system

  is not 100% but it remains sufficient for automotive lighting especially when using light sources such as gas discharge lamps

or arc lamps.

According to another characteristic of

  the invention, it is realized by distributing suitable

  various excitation electrodes according to various regions to be obscured, a modulation of the limit of the occultation zone, constituting the limit of

  pure beam. For example, by using a

  electrodes in horizontal bands juxtaposed, one can adjust the height of the occultation zone, according to the electrodes finally excited on each

of the two aforementioned plates.

  It is also possible, according to another characteristic

  of the invention, to realize a screen of occult-

  tation with discontinuities, if we wish to

  on the cut beam, hold a light supply above the cut. It is thus possible to modulate by electrical means at the same time the cut-off limit

and the intensity of the cut.

  The invention is capable of application in many optical structures of projectors, and in particular, but not exclusively: those comprising a reflector of parabolic type, the light source being close to its focus,

  - those comprising an elliptical reflector

  the light source being in the vicinity of one of the foci of this elliptical reflector, the light rays emitted by the source being returned by the elliptical reflector to its second focus, and picked up again.

  either by a lens or a parabolic reflector

lic.

  The realization of passive screens with crys-

  liquid levels of all types is known in the art

  in the field of digital signage. We are

  for example, in the journal LA RECHERCHE, Volume 12,

  N 125, September 1981, pages 936-939.

  The field of automotive lighting, using very bright sources and high luminous flux, is very different from that of

  digital signage; in the automotive headlamps

  important warm-ups are inevitable.

  However, the tests conducted by the Applicant have shown the "feasibility" of the new projector according to the invention. To avoid heating problems, the screens according to the invention can be judiciously placed in the projector, particularly in the vicinity of its light exit window, away from the light source. Thus, in the extreme, the liquid crystal screen is confused with the ice

  output of the projector. According to another

  as the heating, it oversizes the glass plates of the screen, especially in thickness (relative

  display screens), in order to increase the

heat dissipation.

  Other features and benefits

  of the invention will emerge from the description which

  follow with reference to the attached drawings in

  several examples of embodiments of the invention.

  More specifically, in the accompanying drawings:

  - Figures 1 and 2 represent schematic

  in perspective and in vertical section the realization of a road / crossing projector according to

  the invention in a first embodiment using

  reading an elliptical reflector and a lens, Figure 2a showing the detail of the screen used; - Figures 3 and 4 show in perspective and in schematic vertical section a road / crossing projector in a second embodiment of the invention comprising a parabolic reflector; FIGS. 5 and 6 show in perspective and in horizontal section the constitution of a road / crossing projector according to a third embodiment of the invention comprising

  elliptical reflectors and parabolic reflectors

  c; Figure 6a shows a detail of an embodiment of an organ of Figures 5 and 6; Figures 7 and 8 show the illumination obtained on the road in the two lighting regimes of this projector; - Figures 9 and 10 show schematically in perspective and in vertical section a road / crossing projector, according to a fourth

  embodiment of the invention, FIG.

  a schematic front view of this projector and FIG. 12 showing the illumination obtained on

a screen.

  We will describe about figures 1 and

  2 the first embodiment of the invention.

  From the point of view of its optical structure,

  the projector of this first embodiment

  carries an elliptical reflector 10, a light source

  11 disposed in the vicinity of its internal focus 12, the light rays emitted by the source returned

  by the elliptical reflector 10 converging with the

  the outer focus 13. The convergent-divergent reflected rays are taken up by a lens

  14 to finally constitute a useful transmitted beam.

  According to the invention, in order to achieve the cutoff, a liquid crystal screen 15 of the above-mentioned type defining an occultation zone Z defined between two glass plates is arranged in the vicinity of the external focus 13 of the elliptical reflector 10.

having liquid crystals.

  In a typical example, the screen 15 comprises two parallel glass blades tightly assembled and between which are disposed "helical" nematic liquid crystals. Figure 2a shows such a glass slide 15a. On the two inner faces of the two parallel glass plates a are arranged electrodes 15b in layers

  very thin transparencies (indium or tin oxide).

  By chemical etching, the electrode layer is given before the configuration corresponding to the occultation

  Z. For example, the electrodes are

  in strips 15c. Between the distant plates of

  a few tens of microns, the molecules of

  Liquid rates are oriented quarter-helix (twisted structure). On the two outer faces of the glass plates are arranged crossed polarizers 15d. When such a screen 15 is illuminated, the light polarized by the first polarizer of the first glass plate undergoes a rotation of 90

  between the two plates due to the heli configuration.

  this liquid crystal and comes out the polar back

  rised perpendicularly to its entry direction, the second polarizer of the second plate leaving it

go out. There is transparency.

  If an electric field is applied between the electrodes 15c of the screen 15 via

  terminals 15e, the crystals are deformed.

  Liquid levels, molecules move in parallel

  to the direction of the field. They therefore become

  pendicular to the two glass plates 15a. The polarized light at the entrance is no longer rotated 900 by the liquid crystals. It is stopped by the output polarizer 15d. There is opacity. It can be seen in FIG. 1 that the zone Z is provided with a limit that simply corresponds to the requirements of the crossover lighting (concealment of the area 17 on a projection screen 18). Depending on the state of excitation of the electrical terminals 15e, the

  light rays are or are not obscured by the screen 15.

  The projector can emit either a driving beam,

either a passing beam.

  The input electrodes can be arranged in parallel horizontal bands such that c can be variably excited. Thus, one can adjust the height, and more generally the configuration of the cutoff zone Z by varying

the limited cut.

  In the same way, we can

  trodes 15c, areas completely transparent and always transparent, if you want to have light

above the cut.

  We can finally realize any modulation

  of the cutoff intensity by realizing a zone of oc-

  type Z cultation, that is to say an area

  consisting of successively opaque and trans-

  parents, the tightness of the screen to vary

the degree of occultation.

  The second embodiment of the invention will now be described with reference to FIGS.

3 and 4.

  The projector of this second mode of

  The invention comprises a parabolic main reflector having a focal point 21 on its optical axis constituting the optical axis 22 of the projector. A light source 23, constituted for example by a filament or an electric arc, is located slightly in front of the hearth 21, its rear part coinciding with this focus. As can be seen in the figure, the rays emitted by the light source and reflected by the reflector are therefore slightly convergent. In front of the reflector is disposed a closing window 24 provided with beam distribution grooves, in a manner known per se. Between the reflector and the ice, is

  disposed a liquid crystal screen 25 according to the

  vention having a similar structure to that which comes

  to be described, with two electrical control terminals

  from 25th. When no potential difference is applied to these terminals 25e, the light rays, such as

  than, which pass over the horizontal, pass through

  feel the screen freely and come to refract in the ice 24 thus ensuring a complementary beam

  to that created by the rays such as o <who, themselves,

  always pour freely the upper part of the

ice cream 24.

  So, when no voltage is applied to the 25th terminals, does the projector emit

  beam corresponding to the totality of the rays

  flexed by the reflector and refracted by the totality

  This produces a driving beam. When a potential difference is applied across the electrodes 25e, the liquid crystals orient themselves and make the screen 25 opaque. Rays such as P are now stopped by the

  opaque zone Z of the screen, and only the convergent rays

  Thus, no dazzling gents such as d pass freely through the upper portion of the window 24 which provides the light distribution. We obtain

thus a passing beam.

  The example of Figures 3 and 4 thus shows,

  in a very simple optical configuration, the inter-

  an LCD screen 25 according to the invention.

  vention to achieve, according to the excitation state of the screen, two illumination regimes. We will notice

  it is a static system with electronic control

  It uses a single light source, which obviously makes it far superior to both prior art systems using mobile screens and systems using two light sources, and in any case much less expensive.

  systems using two gas-discharge sources.

  A third embodiment of the invention will now be described with reference to FIGS. 5 to 8. The projector of Figures 5 and 6 comprises two substantially elliptical reflectors 30a, 30b, arranged symmetrically with respect to a central vertical plane. These two reflectors 30a, 30b, have a common internal focus 31 and each an external focus (32a, 32b), the two outer foci (32a, 32b) of the two elliptical reflectors are also symmetrical with respect to a central plane. The light source 33 which may for example be a tungsten filament, an electric arc, a discharge lamp, is arranged at the common focus 31 of the two reflectors (30a, 30b), so that, as shown, the rays coming from the light source and sent back

  left and right by the two elliptical reflectors

1 1

  ticks converge towards the hearths (32a, 32b).

  Outside the two elliptical reflectors

  tics, and always symmetrically with respect to a central vertical plane, are disposed two parabolic reflectors (34a, 34b) whose respective foci are coincident with the external foci (32a, 32b) of the elliptical reflectors (30a, 30b). The overall arrangement is such that the light rays coming from the source 33 reflected by the elliptical reflectors (30a, 30b) converge at their external foci (32a, 32b), meet the parabolic reflectors (34a, 34b) and are finally returned in beams of substantially parallel radii in the emission direction E. In the vicinity of the hearth 32b is disposed vertically an opaque screen of conventional type 35,

  which obscures the rising rays and gives here a

  cut horizontally of the cross beam type

  obtained by reflection on the reflectors 30b and 34b giving an illumination of the type shown on

  Figure 7 (the opaque screen 35 is shown from the face fig.6b).

  On the contrary, the associated reflectors a and 34a do not have a cut-off device. They

  give a complete beam illuminating the totality

  the perspective of the road and which is super-

  pose at the lower part of the beam given by the reflectors 30b and 34b, as seen on

Figure 8.

  With the device defined above, there are thus means of crossing illumination,

  and road illumination means.

  According to the invention, the reflections

  30a and 34a and over the entire output light window a screen 36 containing liquid crystal constituted as previously indicated. When

  this screen 36 is not subject to a voltage of

  The rays such as Ra pass freely through said screen and the totality of the road perspective is illuminated as

  Figure 8. The road function is thus realized.

  When a voltage is applied to the screen 36, it becomes opaque and obscures the rays Ra. Only Rb radii emitted by the subset

  (30b, 34b), i.e.

are emitted (Fig. 7).

  Again, as before, we realize

  with a single light source a static switching

  tick by electrical means. As a variant, the subassembly (30a, 34a) may be equipped with a permanent screen to conceal the cross-type spokes permanently since the other subassembly

  (30b, 34b) always gives enough.

  In a fourth embodiment,

  corresponding to FIGS. 9 to 12, a

  jector having an upper half-reflector

  40. The light source 42 con-

  An axial filament is slightly ahead of this focus 41. This half-reflector 40 gives downward rays such as Poet gives on a screen (FIG. 12).

  a projection 43 whose upper part is sen-

  so horizontal, so not dazzling. the

  upper half-reflector 40 is associated with half a

  lower parabolic reflector 50 whose focus 51

  is located in the middle of the source 42. This half-reflection

  The lower emitter thus gives a beam of rays such as the projection on a screen (FIG. 12).

gives an image such as 53.

  The combination of these two beams given by the same source 42 can give, after optical correction by a closing window (not shown) a good driving beam. To achieve the occultation necessary to obtain a passing beam, it is arranged (FIGS. 9 and 11) around the source of two liquid crystal screens 45 as previously defined, arranged in V below

from the source 41.

  When these screens 45 are in their transparent state, the rays such as oémis o by the source 41 can pass through them easily to come to reflect on the reflector 50 and go back above the horizontal plane to form

the shaded area 53 (FIG. 12).

In case you want to go

  crossing beam, it suffices to apply the

  excitation excitation suitable for liquid crystal displays 45 to make them opaque. At this time, all the rays as they are stopped, the hatched area on the screen is no longer illuminated. Only area 43 and the lower part of the

  area 53 above the horizontal. The fact-

  The cut water then constitutes a passing beam.

  It will be noted that this fourth embodiment, which has just been described, represents the transposition, in a liquid crystal display system of the movable shutter system described in the old French patent 1 296 036 given here for reference and additional information. This reference also includes all the advantages of the electrically controlled static system according to the invention which has the advantage of being faster, more reliable

and insensitive to vibrations.

  The four examples of realization

  given above are not limiting. They pre-

  all feel the benefit of allowing the realization

  a headlamp with two illumination

  both static systems with electric control. They show that the invention applies to the most diverse optical structures, as to the nature of the optical elements used, in particular

reflectors.

  The production of a liquid crystal screen has been given in a technological embodiment known to the Applicant. Of course, this embodiment is only one example, and other liquid crystal displays can be

  used without departing from the scope of the invention.

  The embodiments of projectors, in their novel features, in addition to the presence of liquid crystal occultation screens,

  are also part of the present invention.

  Finally, it must be understood that the invention

  applies to any variable beam projector

  or switchable. For example, a project can be

  passing jets whose illumination changes from the "traffic on the right" mode to the "traffic" mode

  on the left. "We can modulate and make progressive

  any program of change, the variation of

  by correspondingly arranging the controls of the screen which can be in large numbers

(plurality of electrodes).

  It is thus possible to enslave the limit of

  pure to any leading phenomenon, for example the plate

of the vehicle.

Claims (8)

  1.- An automobile projector of the type   having at least one reflector (10; 20; 30a -   30b - 34a - 34b; 40 - 50) cooperating with a single light source (11; 23; 33; 42), characterized in that it comprises an occultation screen (15; 25; 36; 45) interposed on the path of the light rays   and having at least one occultation zone constituting   killed liquid crystals likely to confer   this zone of occultation several states of trans-   ency. 2. A projector according to claim 1, characterized in that said zone of said screen (15; 25; 36; 45) can take either a state of transparency, a state of non-transparency.   3. A projector according to one of the   cations 1 and 2, characterized in that the screen (15; 25;   36; 45) is of the type comprising from outside to   two polarisers, two glass slides, two transparent thin-film electrodes, at least one of which has a surface defining the   the occultation zone, a central filling of crys- helical liquid levels.   4.- A projector according to one of the claims   1 to 3, characterized by a distribution in bands   (15c) of the electrode and the zone of oc- cultation (Z) of the screen (15).   5. A projector according to one of the claims   1 to 4, characterized by a parabolic reflector   that (20) cooperating with a light source (11) lightly   in front of his home, and a screen (25)   placed on the path of the rays reflected by the reflec- tor (20).   6. A projector according to one of the   cations 1 to 4, characterized by a reflector (10)   elliptical having a light source (11) in the vicinity   swimming from its internal focus (12) and a liquid crystal screen (15) in the vicinity of its external focus (13).   7.- A projector according to one of the   cations 1 to 4, characterized by a light source   (33) cooperating with two sets of reflections   elliptical motors (30a, 30b) associated with two reflections   parabolic troughs (34a, 34b), one of the assemblies (30b, 34b) having beam cutoff means (35) and the other (30a, 34a) a liquid crystal display   (36) disposed on its light exit window.   8. A projector according to one of the   cations 1 to 4, characterized in that it comprises a light source (42) cooperating with at least   a reflector (40, 50), and at least one crys-   liquid rates (45) interposed between the source and the reflector.