Light device comprising a variable transmission optical filter

Abstract

Lighting device comprising a variable transmission optical filter. Lighting device (1) for a motor vehicle, characterized in that it comprises a first lighting module (M1) configured to produce a first light beam (F1), and a variable transmission optical filter (20), the first light beam having an opening angle (A1) less than or equal to 20°, the variable transmission optical filter comprising an area (Z1) intended to be illuminated by the first light beam, at least 80% of said area being intended to be illuminated with a brightness between 50% and 150% of the average brightness of said area, the lighting device being intended to perform a first lighting function when the variable transmission optical filter is transparent, the lighting device being intended to perform a second lighting function when the variable transmission optical filter is diffusing. Figure for the abstract: Figure 1

Description

Title of the invention: Lighting device comprising a variable transmission optical filter. Technical field of the invention

[0001] The invention relates to a lighting device for a motor vehicle, the lighting device comprising a variable transmission optical filter such as a liquid crystal filter dispersed in a polymer. Prior art

[0002] A motor vehicle is generally equipped with lighting devices to make it clearly visible to other motorists or road users and / or to illuminate the area around the vehicle for driving in otherwise unlit environments. Lighting devices comprising several functions are known, including a night-time running light, a daytime running light, a dipped beam, and a main beam. The night-time running light aims to make the vehicle clearly visible in the dark without, however, producing a beam of light sufficient to illuminate the area around the vehicle. Such a beam of light can be used, for example, when visibility is reduced on a lit road. The daytime running light, or DRL, is intended to improve the vehicle's visibility during daylight hours.Daytime running lights generally produce a beam of light with the same shape as a nighttime running light, but brighter. Low beams are designed to illuminate the area in front of the vehicle broadly without dazzling other drivers or road users. To this end, low beams produce a beam of light with an asymmetrical shape, adapted to the direction of traffic in the environment where the light is used. High beams are designed to powerfully illuminate the area in front of the vehicle to provide maximum visibility. High beams are intended for use when there are no other drivers or road users within the beam's field of vision. The beam of a high beam has a narrower angle than that of a low beam. In one embodiment, the high beam may also be a matrix or pixelated light.In this case, the high beam is configured to selectively switch on or off certain parts of the beam, depending on the detected position(s) of other vehicles, so as not to dazzle the occupants of those vehicles. Other lighting devices on the vehicle serve to inform other drivers or road users of a current or anticipated situation, such as taillights. stop lights which indicate braking, or direction indicator lights which indicate an upcoming change in the direction of the vehicle on the side on which they light up or, when activated simultaneously on the right and left sides, an abnormal situation such as a breakdown.

[0003] Several different lighting functions are generally integrated into a single lighting device comprising a set of separate lighting modules. Each lighting module is thus designed to produce a light beam whose characteristics correspond to a particular lighting function. Such lighting devices are relatively bulky.

[0004] Furthermore, the lighting devices equipping motor vehicles contribute significantly to their aesthetic appearance. When illuminated, these devices produce a distinctive light signature that helps to differentiate a vehicle. With lighting devices known in the prior art, a vehicle's light signature varies considerably depending on the activated light module. These variations are detrimental to the vehicle's proper identification and its aesthetic appeal. Presentation of the invention

[0005] The object of the invention is to provide a lighting device which at least partially remedies the above disadvantages and improves upon known lighting devices of the prior art.

[0006] More specifically, a first object of the invention is a compact lighting device that produces a more homogeneous light signature regardless of the lighting function that is activated. Summary of the invention

[0007] The invention relates to a lighting device for a motor vehicle, the lighting device comprising a first lighting module configured to produce a first light beam, and a variable transmission optical filter, the first light beam having an opening angle less than or equal to 50°, in particular less than or equal to 20°, the variable transmission optical filter comprising an area intended to be illuminated by the first light beam, at least 80% of said area being intended to be illuminated with a brightness between 50% and 150% of the average brightness of said area, the variable transmission optical filter being configured to be transparent or diffusing depending on at least one control parameter, the lighting device being intended to perform a first lighting function, in particular a high beam type lighting function, when the variable transmission optical filter is transparent,The lighting device is designed to perform a second lighting function, specifically a position light function, when the variable transmission optical filter is diffusing.

[0008] The first light module may include at least one light source and at least one collimation means configured to collimate rays from the light source, the collimation means being positioned upstream of the variable transmission optical filter, the light rays from the light device propagating from upstream to downstream.

[0009] The variable transmission optical filter can be a liquid crystal filter dispersed in a polymer, and can be equipped with two electrodes, the liquid crystal filter dispersed in a polymer being configured to be transparent or diffusing depending on an electrical voltage applied to its electrodes.

[0010] The variable transmission filter can be equipped with two electrodes and can be configured to be transparent when an electrical voltage is applied between its two electrodes. The variable transmission filter can be configured to be diffusing when no electrical voltage is applied between its two electrodes.

[0011] The lighting device may include a second light module configured to produce a second light beam, the second beam avoiding the variable transmission optical filter, the second light module being intended to perform a third lighting function, in particular a low beam type lighting function.

[0012] The lighting device may include a housing inside which the first lighting module and the second lighting module are arranged, the housing including an opening, and the lighting device including a closing glass closing said opening, the variable transmission optical filter being positioned upstream of the closing glass.

[0013] The second light beam may include an opening angle strictly greater than the opening angle of the first light beam, in particular the opening angle of the second light beam may be greater than or equal to 40°, in particular greater than or equal to 60°.

[0014] The first light module and the variable transmission optical filter can each comprise an annular shape, the second light module being positioned inside a ring formed by the annular shape of the first light module.

[0015] The first light module may comprise a plurality of light sources, the light sources of the first light module being distributed regularly around the second light module.

[0016] The first light module may include at least one variable-power light source, at least one light source being activated at a first power level to perform the first lighting function, at least one source of light being activated at a second power strictly lower than the first power to perform the second lighting function. Presentation of the figures

[0017] These objects, features and advantages of the present invention will be described in detail in the following description of a particular embodiment, given by way of non-limiting example, with reference to the accompanying figures, among which:

[0018] Fig. 1 is a schematic view of a lighting device according to an embodiment of the invention, the lighting device comprising a first lighting module and a second lighting module, the lighting device being observed along the general direction of the light beam(s) exiting the lighting device.

[0019] Fig. 2 is a schematic cross-sectional view of the first light module equipped with a collimation means according to a first embodiment.

[0020] Fig. 3 is a schematic cross-sectional view of the first light module equipped with a collimation means according to a second embodiment.

[0021] Fig. 4 is a schematic cross-sectional view of the first light module equipped with a collimation means according to a third embodiment.

[0022] The [Fig.5] is a schematic cross-sectional view of the first light module equipped with a collimation means according to a fourth embodiment.

[0023] Fig. 6 is a schematic cross-sectional view of the first light module equipped with a collimation means according to a fifth embodiment.

[0024] Fig. 7 is a schematic cross-sectional view of the lighting device of Fig. 1. Detailed description

[0025] Figure 1 schematically illustrates a lighting device 1 for a motor vehicle according to an embodiment of the invention. The lighting device 1 is intended to be integrated into the front of a vehicle and to perform several lighting functions, in particular four lighting functions. These four lighting functions are a night position light, a daytime running light (DRL), a low beam headlight, and a high beam headlight, for example, a fixed high beam headlight and / or an adaptive high beam headlight and / or a matrix or pixelated high beam headlight. Alternatively, the lighting device 1 could produce only three or only two of the four lighting functions mentioned. The lighting device could also perform other lighting functions in addition to the four lighting functions mentioned, for example, a fog light function.Preferably, the lighting device 1 is intended to produce at least one position light function (night and / or day) and one high beam function. As a side note, the invention could also be adapted. to a lighting device intended to be integrated at the rear of the vehicle to perform various lighting functions for positioning and / or illumination.

[0026] The lighting device 1 comprises a first light module M1 configured to produce a first light beam Fl and a second light module M2 configured to produce a second light beam F2. According to the embodiment presented, the first light module M1 has an annular shape and is provided with a central opening inside which the second light module M2 is arranged. The second light module M2 has a circular shape inscribed inside the central opening of the first light module M1. In other words, the second light module M2 is positioned inside the ring formed by the annular shape of the first light module M1 along an observation direction corresponding to the general direction of the light beams exiting the lighting device 1.This configuration allows for a compact lighting device 1 with the center of the first light beam Fl substantially coinciding with the center of the second light beam F2. Alternatively, other arrangements of the light modules M1 and M2 could be considered. The first light module M1 and the second light module M2 could, for example, be positioned side-by-side. The lighting device 1 further comprises a housing within which the first light module M1 and the second light module M2 are arranged. The lighting device 1 thus forms a single unit intended for assembly in a motor vehicle. According to another variant, the lighting device 1 could comprise only the first light module ML. The housing includes an opening closed by a glass cover. The light beams Fl and F2 are intended to pass through the glass cover.

[0027] Figure 7 illustrates the light device in 1 in cross-section along a plane of parallel cross-section with the light emission axis DI and passing substantially through a center of the light device. With reference to Figure 7, the first light beam Fl is a relatively narrow beam: it has an aperture angle Al of 20° or less, or even 15° or less. The aperture angle of a light beam can be defined as the maximum angle formed between two directions of propagation of light rays in the light beam before the light beam reaches a variable transmission optical filter, which will be defined later. An aperture angle of 20° therefore means that the light rays of the light beam are contained within a cone of light whose apex angle is 20°.For the assessment of the beam angle of a light beam, one can neglect stray light rays and / or those causing low-intensity lighting, for example an intensity less than or equal to 5% of the maximum intensity of the light beam, or even less than or equal to 1% of the maximum intensity of the light beam.

[0028] In order to produce a narrow beam of light as defined above, the first light module M1 comprises at least one light source 11 and at least one collimation means 12 configured to collimate rays emanating from the light source. "Collimating" is understood to mean a transformation of a light beam resulting in the production of a narrow beam of light as defined above.

[0029] Advantageously, the first light module M1 can comprise a plurality of light sources, each light source being associated with a collimation means. In this case, the first light module comprises twelve light sources and twelve collimation means, each collimation means being associated with a light source. The light sources 11 and the collimation means 12 are distributed regularly around the center of the first light module M1. Alternatively, the number of light sources 11 and the number of collimation means 12 could be different from twelve, for example, any number between six and twenty. Furthermore, they could be distributed irregularly.

[0030] Each light source 11 may preferably include a luminescent semiconductor element such as a light-emitting diode. Each light source may in particular include a single light-emitting diode. Each light-emitting diode may be connected to a printed circuit board.

[0031] Different types of collimation means 12 can be envisaged. Figures 2 to 6 show examples of collimation means 12, in cross-section along a pair plane parallel to the light emission axis DI and passing substantially through a light source 11 associated with said collimation means 12. With reference to [Fig. 2], the collimation means 12 may comprise only a parabolic reflective wall 13, the light source 11 then being positioned at the focus of the parabolic shape or near the focus of the parabolic shape, the light source comprising a light emission axis DI coinciding or substantially coinciding with a director axis of the parabolic shape. With reference to [Fig.[3] The collimation means 12 may include a parabolic reflecting wall 13 as defined previously and an optical lens 14, in particular a convex optical lens, positioned downstream of the reflecting wall 13 along the direction of propagation of the light rays from the light source 11. With reference to [Fig. 4], the collimation means 12 may include only the optical lens 14, in particular a convex optical lens. With reference to [Fig. 5], the collimation means 12 may include a parabolic or substantially parabolic collector 15, the light source 11 then being positioned at the focus of the parabolic shape or near the focus of the parabolic shape, the light source comprising a light emission axis DI. perpendicular or substantially perpendicular to a parabolic axis. According to the embodiment of [Fig. 6], the collimation means 12 comprises a collector 15 as defined previously in relation to [Fig. 5] and an optical lens 14, in particular a convex optical lens, positioned downstream of the collector 15 in the direction of propagation of the light rays from the light source 11. Note that throughout this description, the terms "upstream" and "downstream" refer to the direction of propagation of the light rays, which propagate from upstream to downstream.

[0032] The lighting device 1, and more particularly the first light module M1, also includes a variable transmission optical filter 20 positioned downstream of the collimation means 12 along the direction of propagation of the light rays from the light source 11. The variable transmission optical filter 20 is designed to receive the first narrow light beam Fl, as defined above. The variable transmission optical filter 20 extends in a plane perpendicular or substantially perpendicular to a central axis of the first light beam FL. According to one embodiment, the variable transmission optical filter 20 can be positioned upstream of the closing glass that closes the housing in which the light modules M1 and M2 are housed. The variable transmission optical filter 20 can, in particular, extend along an inner face of the closing glass.

[0033] A variable transmission optical filter is an optical device whose transparency can be adjusted in real time. A variable transmission optical filter can be configured to modulate the amount of light transmitted and / or to modulate the shape of a light beam transmitted downstream. In this case, the variable transmission optical filter 20 can be controlled to be in a transparent state or in a diffusing state.

[0034] The variable transmission optical filter 20 comprises electrodes 21, 22 electrically connected to an electronic control unit 23. The electronic control unit 23 is capable of applying an electrical voltage to the variable transmission optical filter 20, via the electrodes 21, 22, to modify its transmission. The variable transmission optical filter 20 can thus be in a transparent state or in a diffusing state depending on the electrical voltage between its electrodes 21, 22. The electrical voltage controlled by the electronic control unit 23 is therefore a control parameter of the variable transmission optical filter 20.

[0035] According to a preferred embodiment, the variable transmission optical filter 20 is a polymer dispersed liquid crystal (PDLC) filter. A polymer dispersed liquid crystal filter generally consists of a transparent polymer matrix containing anisotropic microdroplets of liquid crystals. The entire assembly is encapsulated, typically sandwiched between two transparent conductive substrates connected to electrodes 21 and 22. In the absence of an electrical voltage between electrodes 21 and 22, the liquid crystals inside the microdroplets are randomly oriented, particularly from one microdroplet to another, causing light scattering and rendering the filter translucent or opaque. When a sufficient electrical voltage is applied between electrodes 21 and 22, the liquid crystals align in a uniform direction, allowing light to pass through directly and making the filter transparent.

[0036] When the variable transmission optical filter 20 is in a transparent state, it allows the first light beam Fl to pass through without significantly distorting it. However, in its so-called "transparent" state, the variable transmission optical filter 20 is not perfectly transparent: it retains an internal grain, or texture, which slightly modifies the contours of the first light beam Fl. The variable transmission optical filter 20 thus exhibits residual scattering. This residual scattering can be due to surface tension effects at the interface between the microdroplets and the transparent polymer matrix and / or to differential effects depending on the polarization of the light for light rays arriving at a high angle of incidence. This grain can also be explained by the presence of liquid crystals which, even when aligned in the same direction, form micro-obstacles that intercept some light rays.This grain only very slightly disturbs light rays oriented perpendicular to the plane in which the variable transmission optical filter 20 extends. However, this grain more significantly disturbs light rays incident at an angle of incidence other than 0° with respect to the light emission axis DI. More precisely, the more the angle of incidence of the light rays incident on the variable transmission optical filter 20 deviates from 0°, the more the grain of the variable transmission optical filter 20, in its transparent state, disturbs the path of these light rays. Since the first light beam Fl has a small aperture angle Al, namely less than or equal to 20°, the first light beam Fl is not significantly modified by its passage through the variable transmission optical filter 20 in its transparent state.

[0037] In its diffusing state, the variable transmission optical filter diffuses the first light beam Fl; in particular, it widens the light beam by increasing its opening angle and it homogenizes the brightness of the first light beam FL. When the first light module Ml is observed with its light source(s) 11 illuminated and the variable transmission optical filter in its transparent state, it is possible to distinguish with the naked eye brighter areas corresponding to the light source(s) or to the reflection of these light sources on reflective surfaces. Conversely, when the first light module Ml is observed With its light source(s) switched on and the variable transmission optical filter in the diffusing state, it is no longer possible to distinguish with the naked eye brighter areas corresponding to the light source or light sources.

[0038] The variable transmission optical filter 20 comprises a zone Zl, delimited by dashed lines in [Fig. 1], intended to receive the first light beam Fl. Zone Zl corresponds to a functional part of the variable transmission optical filter 20 and is entirely permeable to light rays. This zone Zl is intended to be illuminated homogeneously: in particular, at least 80% of said zone Zl is intended to be illuminated with a brightness between 50% and 150% of the average brightness of said zone Zl. Zone Zl is therefore not intended to be partially illuminated, for example with a cutoff beam such as a beam adapted for use as a low beam. Indeed, the grain of the variable transmission optical filter 20 in its transparent state would impair the sharpness of such a cutoff.

[0039] The variable transmission optical filter 20 enables two lighting functions to be performed with the first light module M1: in this case, the first light module M1 is capable of performing a first lighting function, in particular a high beam function, when the variable transmission optical filter is in its transparent state. The light device 1 is intended to perform a second lighting function, in particular a position light function, when the variable transmission optical filter is in its diffusing state. This results in a particularly compact light device that produces the same light signature when the position lights are activated and when the high beam is activated.

[0040] Advantageously, the light source(s) 11 of the first light module are of the "variable power" type, meaning that they emit a variable flux of light depending on their power supply, in particular depending on the intensity of a supply current and / or depending on pulse-width modulation parameters. The light source(s) 11 can thus be activated at a first power level to perform the first lighting function, and at a second power level strictly lower than the first power level to perform the second lighting function. For example, the light source(s) 11 can be activated at a low power level to perform a night-time position light function and at a higher power level to perform a day-time position light function.In another example, the light source(s) 11 can be activated at a low power level to perform a position light function and at a higher power level to perform a high beam function. In yet another example, the light source(s) 11 can be activated at a low power level to perform... a night position light function, at an intermediate power to perform a day position light function, and at a higher power to perform a high beam function.

[0041] Advantageously, the variable transmission optical filter 20 is configured to be transparent when an electrical voltage is applied between its electrodes 21, 22, and the variable transmission optical filter 20 is configured to be diffusing when no electrical voltage is applied between its electrodes 21, 22. Since the use cases of a high beam are less frequent than those of a position light, the activation time of the variable transmission optical filter 20 is limited and thus the consumption of electrical current by the lighting device 1 is reduced.

[0042] As previously stated, the second light module M2 is configured to produce a second light beam F2. The second beam F2 avoids the variable transmission optical filter 20: the second light beam F2 therefore does not pass through the variable transmission optical filter 20. It is thus understood that the variable transmission optical filter 20 comprises an annular shape with a central aperture through which the second light beam F2 passes.

[0043] The second light module M2 is intended to perform a third lighting function, in particular a low beam function. To this end, the second light module M2 also includes at least one second light source and a set of second optical components capable of shaping the light beam produced by the second light source.

[0044] As illustrated in [Fig. 7], the second light beam F2 has a beamwidth A2 strictly greater than the beamwidth Al of the first light beam FL. The beamwidth of the second light beam can be greater than or equal to 40°. Some light rays of the second light beam F2 therefore form a relatively small angle, in particular less than or equal to 70°, with the plane in which the variable transmission optical filter 20 extends. These light rays are nevertheless not disturbed by the grain of the variable transmission optical filter 20 in its transparent state since they do not pass through the variable transmission optical filter 20. This makes it possible to produce a "low beam" type light beam with sharp edges, which ensures that other motorists and / or road users are not dazzled.It is therefore understood that the residual diffusion of the variable transmission optical filter 20 in its transparent state is incompatible with a cutoff light beam such as a dipped headlight. This is not a problem because the second light module is positioned so that the second light beam F2 does not pass through the variable transmission optical filter 20.

[0045] If the variable transmission optical filter 20 had been placed in front of the second light module M2, the diffusion generated by this filter in its transparent state would have posed A problem arises in ensuring a clean break in the second light beam F2, meaning a strong contrast between the high-intensity area below the break and the low-intensity area above it. Even slight diffusion could significantly alter the beam at the break. Some of the diffused light would end up angularly above the break, making it less sharp and potentially causing non-compliance with regulations, including a risk of glare for other road users, such as drivers of oncoming vehicles.

[0046] Finally, thanks to the invention, we have a compact lighting device 1 capable of producing numerous lighting functions. The light signature produced by the lighting device remains homogeneous, at least for some of the lighting functions performed by the lighting device 1.

Claims

Demands

1. A lighting device (1) for a motor vehicle, characterized in that it comprises a first lighting module (Ml) configured to produce a first light beam (Fl), and a variable transmission optical filter (20), the first light beam having an opening angle (Al) less than or equal to 50°, in particular less than or equal to 20°, the variable transmission optical filter comprising an area (Zl) intended to be illuminated by the first light beam, at least 80% of said area being intended to be illuminated with a brightness between 50% and 150% of the average brightness of said area, the variable transmission optical filter being configured to be transparent or diffusing depending on at least one control parameter, the lighting device being intended to perform a first lighting function, in particular a high beam function, when the variable transmission optical filter is transparent,the lighting device being intended to perform a second lighting function, in particular a position light function, when the variable transmission optical filter is diffusing.

2. A light device (1) according to the preceding claim, characterized in that the first light module (M1) comprises at least one light source (11) and at least one collimation means (12) configured to collimate rays from the light source, the collimation means being positioned upstream of the variable transmission optical filter (20).

3. A light device (1) according to any one of the preceding claims, characterized in that the variable transmission optical filter (20) is a liquid crystal filter dispersed in a polymer, and is equipped with two electrodes (21, 22), the liquid crystal filter dispersed in a polymer being configured to be transparent or diffusing depending on an electrical voltage applied to its electrodes.

4. A lighting device (1) according to any one of the preceding claims, characterized in that the variable transmission filter (20) is equipped with two electrodes (21, 22) and is configured to be transparent when an electrical voltage is applied between its two electrodes, and in that the variable transmission optical filter (20) is configured to be diffusing when no electrical voltage is applied between its two electrodes.

5. A lighting device (1) according to any one of the preceding claims, characterized in that it comprises a second lighting module (M2) configured to produce a second light beam (F2), the second beam avoiding the variable transmission optical filter, the second lighting module being intended to perform a third lighting function, in particular a low beam type lighting function.

6. Light device (1) according to the preceding claim, characterized in that it comprises a housing inside which are arranged the first light module (M1) and the second light module (M2), the housing comprising an opening, and the light device comprising a closing glass closing said opening, the variable transmission optical filter (20) being positioned upstream of the closing glass.

7. Light device (1) according to any one of claims 5 or 6, characterized in that the second light beam (F2) comprises an opening angle (A2) strictly greater than the opening angle (Al) of the first light beam, in particular in that the opening angle of the second light beam is greater than or equal to 40°, in particular greater than or equal to 60°.

8. Light device (1) according to any one of claims 5 to 7, characterized in that the first light module (M1) and the variable transmission optical filter (20) each comprise an annular shape, the second light module (M2) being positioned inside a ring formed by the annular shape of the first light module (M1).

9. A lighting device (1) according to any one of claims 5 to 8, characterized in that the first lighting module (M1) comprises a plurality of light sources (11), the light sources of the first lighting module being distributed regularly around the second lighting module (M2).

10. A lighting device (1) according to any one of the preceding claims, characterized in that the first lighting module (M1) comprises at least one light source (11) of variable power, the at least one light source being activated at a first power to perform the first lighting function, the at least one source light being activated at a second power strictly lower than the first power to perform the second lighting function.