A motor vehicle detection system comprising a light beam emission module and a light beam reception module

Abstract

The invention relates to a lighting system for a motor vehicle comprising an emission module (2) including a light module (21) capable of emitting a light beam (F1) whose spectrum includes at least a portion in the visible spectrum, the light module being capable of modifying the polarization state (S, P) of the emitted light beam, and a modulation unit (22) capable of receiving a modulation instruction (Seq, Sig), and arranged to, upon receiving said modulation instruction, control the light module to modulate the polarization state of the emitted light beam. Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: A motor vehicle detection system comprising a light beam emission module and a light beam reception module

[0001] The invention relates to the field of automotive lighting and vehicle communication functions, or to the detection of an object by a motor vehicle and the estimation of the distance between that object and the vehicle. More specifically, the invention relates to a motor vehicle lighting system capable of implementing telemetry or communication functions by means of the light it emits.

[0002] It is known, in the automotive field, to use a pulsed light beam emitted by a light module of a light system of a motor vehicle to perform a given photometric function.

[0003] Conventionally, the light source that emits this light beam is controlled by a pulse-width modulated (PWM) electrical signal. The light source is thus periodically switched on and off by this PWM signal, so that the emitted light beam consists of successive light pulses occurring at a frequency high enough that they are indistinguishable to the human eye. The intensity of the emitted light beam is a function of the duty cycle of this PWM signal, making it possible to control it by adjusting this duty cycle and thus implement a photometric function.

[0004] Beyond performing one or more photometric functions, such as daytime running lights or low beams, various other functions can be implemented by this type of lighting module. For example, the light source of the lighting module can be controlled so that the pulses of the emitted light beam carry a data sequence. The lighting system can thus perform a telemetry function by being equipped with a receiver module to receive the emitted light beam after reflection from an object near the vehicle. A processing unit in the motor vehicle can then, after detecting the data sequence in the received light beam, determine the time of flight of the emitted light beam and thus estimate the distance between the vehicle and the object.Another system, equipping another vehicle or infrastructure, may also include such a receiving module as well as a computing unit, thus enabling vehicle-to-vehicle or vehicle-to-infrastructure communication.

[0005] In this way, the light beam can retain its original function, namely to perform a photometric function, while allowing the light system to implement a telemetry function, which can be particularly advantageous for example for driving assistance functions or in the context of autonomous or semi-autonomous driving, and / or a communication function.

[0006] However, this type of system, based on the use of a transmitting module capable of both performing a photometric light function and transmitting data, has a drawback. Indeed, the receiving module, intended to receive the light beam carrying the data, whether located in the same vehicle or in another vehicle or infrastructure, must include at least one photodetector to convert this light beam into an electrical signal, which can then be processed by the computing unit to detect one or more pulses.

[0007] However, under certain conditions, the signal-to-noise ratio of this photodetector can be significantly degraded due to stray light sources in the vehicle's environment, such as streetlights, headlights from oncoming or following vehicles, or even sunlight in bright conditions, and the nature of the objects in the environment, particularly their reflectivity. This degradation of the signal-to-noise ratio can then reduce the accuracy of the processing unit in estimating the distance to the target object, or even lead to false positives.

[0008] There is therefore a need for a lighting system of a motor vehicle, capable of performing both a given photometric function and an information transmission function, and whose signal-to-noise ratio is improved.

[0009] The present invention falls within this context and aims to meet this need.

[0010] To this end, the invention relates to a lighting system for a motor vehicle, comprising an emission module including a light module capable of emitting a light beam whose spectrum has at least a portion in the visible spectrum, the light module being capable of modifying the polarization state of the emitted light beam, and a modulation unit capable of receiving a modulation instruction, and arranged to, upon receiving said modulation instruction, control the light module to modulate the polarization state of the emitted light beam.

[0011] Unlike known solutions, which propose to modulate the amplitude of the emitted light beam in an on / off fashion, making them sensitive to noise and inducing performance losses with regard to the photometric functions they perform, the invention proposes to transmit information via the polarization states of the light beam emitted by a light module, which natively performs a photometric function. A data sequence or a particular signal can thus be encoded in a light beam emitted through Discrete or continuous changes in the polarization state of the light that composes it. For example, it could be a series of changes from horizontal linear polarization (P) to horizontal linear polarization (S), and vice versa. It could also be a series of changes from left-handed circular polarization to right-handed circular polarization, and vice versa. More generally, it could also be changes in the phase shift between the vertical and horizontal components of the light. These phase shift variations can be continuous, in which case the modulation is analog, or they can occur between several discrete phase shift values, defined beforehand, in which case the modulation is digital.

[0012] It is thus possible to modulate a predetermined signal or a predetermined data sequence to allow the system to simultaneously implement a given photometric function and a telemetry function. It is also possible to modulate a data sequence, or a signal, carrying information that the vehicle wishes to communicate to another vehicle or another infrastructure.

[0013] It should be noted that light sources capable of generating noise that is added to the emitted light beam emit light that is generally unpolarized or only slightly polarized, or in other words, composed of randomly polarized wave trains. In other words, a portion of the light beam modulated with a given polarization state will be noisy by only a part of this light, so that the signal-to-noise ratio is improved.

[0014] In one embodiment of the invention, the light module comprises a light source and a polarization controller capable of modifying the polarization state of the light emitted by the light source, and the modulation unit is arranged to, upon receiving said modulation instruction, control the polarization controller to drive a sequence of changes in the polarization state of the light emitted by the light source.

[0015] For example, the polarization controller may include a linear polarizer arranged downstream of the light source and capable of polarizing light emitted by the light source in a given polarization direction, and a delay optical element arranged downstream of the linear polarizer and capable of polarizing light from the polarizer with an elliptical polarization state. The delay optical element is rotatably mounted in the light module, in particular about an axis of rotation substantially coinciding with the overall emission direction of the light source. It is thus understood that the angular position of the delay optical element allows control of the elliptic angle of the light from the polarization controller.

[0016] Where applicable, the polarization controller is equipped with an actuator capable of driving a rotation of the optical delay element and the modulation unit is arranged to, upon receiving said modulation instruction, control the actuator to drive a sequence of rotations of the optical delay element, so as to cause a sequence of changes in the angle of ellipticity of the light coming from the polarization controller.

[0017] The modulation unit may, for example, control the rotation of the optical delay element according to a given modulating signal, predetermined or received from a processing unit, so that the elliptic angle of the light emitted by the light module reproduces this modulating signal. Alternatively, the modulation unit may, for example, control the rotation of the optical delay element according to a modulating data sequence, predetermined or received from a processing unit, so that the elliptic angle of the emitted light is sequentially switched between several discrete values ​​according to the data in the modulating data sequence. The values ​​of the data in this sequence are thus encoded in the elliptic angle values, or in the changes in these values, that successively result from the polarization of the light beam emitted by the light module.

[0018] For example, the linear polarizer may comprise a semi-reflective plate inclined at the Brewster angle with respect to the emission axis of the light source, or a grid polarizer. For example, the optical delay element may comprise one or more half-wave or quarter-wave delay plates, or a pair of rhombic Fresnel prisms.

[0019] In another alternative or cumulative embodiment, the light module includes a spin-LED type light source capable of emitting light having a circular polarization whose direction is controllable and the modulation unit is arranged to, upon receiving said modulation instruction, control the light source to cause a sequence of changes in the direction of the circular polarization of the light source.Such a spin-LED is notably designed from several superimposed layers of semiconductor, such as a first layer of undoped gallium nitride (GaN), followed by layers of silicon-doped gallium nitride (n-Gan), layers of silicon-doped aluminum-gallium nitride (n-AlGaN, hole-blocking layer), layers of undoped gallium nitride (GaN), layers of indium-gallium nitride (InGaN, active layer forming a quantum well), a magnesium-doped aluminum-gallium nitride (p-AlGaN, electron-blocking layer) and layers of magnesium-doped gallium nitride (p-GaN), and including a spin injection layer, for example of a gallium-chromium nitride (GaCrN) layer. In one example, the modulation unit may be able to apply a magnetic field, for example with an amplitude of a few Tesla, to the spin-LED, via this spin injection layer, to control the direction of circular polarization.

[0020] The modulation unit may, for example, control the direction of rotation of the circular polarization of the light emitted by the light source according to a modulating data sequence, predetermined or received from a processing unit, so that this direction of rotation is sequentially switched between a left-handed value and a right-handed value, according to the data in the modulating data sequence. The values ​​of the data in this sequence are thus encoded in the directions of rotation, or in the changes in direction of rotation, successively exhibited by the circular polarization of the light beam emitted by the light module.

[0021] In another embodiment, alternative or cumulative, the light module comprises a plurality of light sources, each selectively controllable, and a plurality of polarizing devices, each associated with one of the light sources and arranged to polarize light emitted by that light source according to a given polarization state, and the modulation unit is arranged to, upon receiving said modulation instruction, control said light sources to drive a sequence of selective activation of the light sources.

[0022] The modulation unit may, for example, sequentially activate light sources, one after the other, according to a modulating data sequence, predetermined or received from a computing unit, so that the light beam emitted by the light module is composed of a continuous train of elementary beams whose polarization states vary according to the data in the modulating data sequence. The values ​​of the data in this sequence are thus encoded in the polarization states, or in the changes of polarization states, that the light beam emitted by the light module successively exhibits.

[0023] For example, the light module may comprise two light sources, for example, two semiconductor chips emitting light from the same light-emitting diode (LED) that can be selectively controlled, and a first linear polarizer arranged downstream of one of the chips and capable of polarizing the light emitted by that chip in a given polarization direction, as well as a second linear polarizer arranged downstream of the other chip and capable of polarizing the light emitted by that chip in another given polarization direction. It is thus possible to achieve, in a simple manner, binary modulation by polarization shift of the light beam. Alternatively, the light module may be designed to comprise more than two light sources, the polarization states defined by the polarizing devices associated with these light sources being all distinct from one another, without necessarily being limited to linear polarization states..

[0024] In one embodiment of the invention, the light module is capable of emitting a light beam whose spectrum has a peak at a wavelength in the visible range, in particular between 400 nm and 500 nm. Advantageously, the light module includes a light source comprising a semiconductor generator capable of emitting an elementary light beam, in particular whose spectrum has a peak at a wavelength in the visible, and a photoluminescent element capable of converting said elementary light beam to obtain said light beam.

[0025] The semiconductor could, for example, be gallium nitride, or GaN, capable of emitting blue light rays by electroluminescence in response to an electric current passing through it. The photoluminescent element could, for example, be in the form of a resin comprising a cerium-doped yttrium aluminum garnet, or CE:YAG, capable of absorbing blue light and, by photoluminescence in response to the excitation produced by this light, of emitting yellow light rays. The photoluminescent element is arranged on the generator so that a portion of the blue light rays excites this element, causing it to emit yellow light rays by photoluminescence. The other portion of the blue light rays passes through this element. Thus, when electrically powered, the light source simultaneously emits blue and yellow light rays, the resulting light appearing white to the human eye.

[0026] The light source may thus be a laser type source, a light-emitting diode, a vertical-cavity surface-emitting laser diode, also called VCSEL (from the English "Vertical-Cavity Surface-Emitting Laser") or a superluminescent diode or SLED (from the English "Superluminescent diode").

[0027] Advantageously, the light module may include an optical unit arranged to project the light rays emitted by the light source to form said light beam.

[0028] Advantageously, the modulation unit is capable of receiving a modulating data sequence, and the modulation unit is arranged so that, upon receiving said modulating data sequence, it controls the light module to modulate the polarization state of the light beam emitted by the light module according to a given polarization modulation alphabet and according to the modulating data sequence. A polarization modulation alphabet may, for example, associate a symbol—that is, a value that a data point in a modulating sequence or a series of several successive values ​​may take—with a given polarization state or a change from one polarization state to another. This embodiment thus corresponds to a digital modulation of the polarization of the light beam emitted by the light module.Each piece of data, or sequence of data, in the modulating data sequence can thus be transposed, according to this alphabet, into a modulation state of the light beam emitted by the light module. The sequence of modulation states followed by the modulated light beam thus encodes the modulating data sequence. The data sequence can be a predetermined sequence, intended for the implementation of a telemetry function, or a variable sequence carrying information, intended for the implementation of a communication function for that information.

[0029] Alternatively, the modulation unit may be provided to be capable of receiving a modulating signal and to be arranged so that, upon receiving the modulating signal, the modulation unit controls the light module to modulate the polarization state of the emitted beam according to this modulating signal, the changes in polarization state reproducing the modulating signal. This embodiment thus corresponds to an analog modulation of the polarization of the light beam emitted by the light module.

[0030] In one embodiment, the lighting system comprises a receiving module capable of receiving a light beam. The receiving module comprises an elementary acquisition module including a plurality of photodetectors, each capable of converting a received light signal into an electrical signal. The elementary acquisition module includes, for each photodetector, a polarizing filter of a given polarization state, arranged to transmit only to that photodetector a component of the received light beam exhibiting that given polarization state. It is thus possible to distinguish, within the received light beam, a modulated light beam emitted by the lighting module of the system's receiving module, or by an equivalent system equipping another vehicle or infrastructure. Advantageously, the receiving module may comprise a plurality of elementary acquisition modules.If applicable, the set of polarization states filtered by the polarizing filters may correspond to the polarization states of the polarization modulation alphabet used by the modulation unit.

[0031] For example, the set of photodetectors can form a sensor, for example a single electronic component.

[0032] Advantageously, the photodetector of the elementary acquisition module(s) is an avalanche photodiode. This type of photodetector is also known as a SPAD, from the English "Single-Photon Avalanche Diode". A set of avalanche photodiodes can thus form a silicon photomultiplier or SiPM (from the English "Silicon PhotoMultiplier"). This type of photodetector makes it possible to detect the incidence of a single photon with a high gain, for example on the order of 10⁶, and therefore to compensate for the degradation of the signal-to-noise ratio due to external conditions.

[0033] According to one embodiment of the invention, the receiving module may include an optical unit arranged in front of the elementary acquisition module(s). The polarizing filters may be arranged between the elementary acquisition module and the optical unit, or upstream of said optical unit.

[0034] In one embodiment, the lighting system includes a processing unit arranged to generate a modulating signal and to transmit said modulating signal to the modulation unit for the emission of a light beam modulated by the lighting module. Where applicable, the processing unit is arranged to determine a time-of-flight interval between the emission of the modulated light beam and the reception of a light beam by the receiving module, based on one or more electrical signals converted by one or more of said photodetectors of the elementary acquisition module from said received light beam. The modulating signal may be a predetermined continuous signal or a predetermined data sequence.

[0035] In one embodiment of the invention, the lighting system comprises a demodulation unit connected to said photodetectors and arranged to extract a signal, referred to as the demodulated signal, from one or more electrical signals converted by one or more of said photodetectors of the elementary acquisition module from said received light beam. Where applicable, the processing unit is arranged to detect, in a demodulated signal extracted by the demodulation unit, the presence of said modulating signal and to determine, from said detection, a time of flight separating the emission of said emitted light beam from the reception of said received light beam. In other words, the detection of the presence of the modulating signal in the modulated signal makes it possible to identify the moment of reception of this modulating signal in the received light beam, and thus to estimate the time of flight of the modulated light beam, in order to enable the performance of a photometry function.It should be noted that this detection of the modulating signal can be achieved without using a correlation algorithm.

[0036] Alternatively, the computing unit can be configured to estimate each value of a correlation function between said demodulated signal and said modulating signal by evaluating the cross-correlation of the modulated signal and the modulating signal delayed by a given time associated with said value. In other words, each value of the correlation function is thus associated with a value of a time shift of the modulating signal used to estimate that value of the correlation function. The computing unit is thus configured to identify the time shift value associated with the maximum value of the cross-correlation function. The computing unit can thus determine a time-of-flight separating the emission of said modulated light beam. from the reception of said light beam received from the values ​​of the correlation function.

[0037] For example, in the case of digital modulation, the computing unit can be arranged to generate a modulating data sequence and to transmit said modulating data sequence to the modulation unit for the emission of a light beam modulated by the light module, and the demodulation unit is connected to said photodetectors and arranged to extract a data sequence, said to be demodulated, from one or more electrical signals, converted by one or more of said photodetectors of the elementary acquisition module from said received light beam, and from the polarization modulation alphabet used by the modulation unit.

[0038] For example, the demodulation unit may be arranged so that, upon receiving an electrical signal converted by one of the photodetectors of the elementary acquisition module, it emits a corresponding symbol, in the polarization modulation alphabet used by the modulation unit, to the polarization state filtered by the polarizer filter associated with that photodetector.

[0039] Alternatively, in the case of analog modulation, the polarizing filters act as samplers of the polarization state value of the received light beam. Therefore, an electrical signal converted by one of the photodetectors of the elementary acquisition module and received by the demodulation unit can be converted into said polarization state value filtered by the polarizing filter associated with that photodetector, and the demodulation unit will be configured to extrapolate a demodulated signal from these converted values.

[0040] In one embodiment of the invention, the transmission module is arranged in a front headlight of the motor vehicle. Advantageously, the reception module and the transmission module are arranged in a front headlight of the motor vehicle.

[0041] Preferably, the emitting module is arranged so that the light beam participates, wholly or partially, in the performance of a predetermined regulatory photometric function. For example, it could be a daytime running light (DRL), which has the advantage of being emitted over a wide field with low intensity.

[0042] The invention also relates to a method of transmitting information, the method being implemented by a light system, in particular by a light system according to the invention.

[0043] The present invention is now described by means of purely illustrative and in no way limiting examples of the scope of the invention, and from the accompanying drawings, in which the various figures represent:

[0044] [Fig.1] represents, schematically and partially, a view of a system of a motor vehicle according to an example of an embodiment of the invention;

[0045] [Fig.2] represents, schematically and partially, a first example of realization of the system of [Fig.1];

[0046] [Fig.3] represents, schematically and partially, a transmission method of information implemented by the lighting system of [Fig.2];

[0047] [Fig.4] represents, schematically and partially, a second example of implementation of the system in [Fig. 1]; and

[0048] [Fig.5] represents, schematically and partially, a transmission method of information implemented by the lighting system of [Fig.4].

[0049] In the following description, identical elements, by structure or by function, appearing on different figures retain, unless otherwise specified, the same references.

[0050] A system 1 of a motor vehicle is shown in [Fig.1] according to an example of an embodiment of the invention.

[0051] The system 1 comprises an emission module 2 arranged to emit a light beam Fl and a reception module 3 intended to receive a light beam F2.

[0052] In the example described, the transmission module 2 and the reception module 3 are arranged in the same front headlight of the motor vehicle. It may be provided that the modules 2 and 3 are arranged in different locations within the motor vehicle, without departing from the scope of the present invention.

[0053] The emission module 2 comprises a light module 21 for emitting a light beam Fl and a modulation unit 22.

[0054] The light module 21 is arranged so that the light beam Fl it emits has an electromagnetic spectrum, at least a portion of which lies within the visible spectrum. In the example described, the spectrum has an intensity peak, or line, in the blue at 450 nm. It should be noted that the spectrum may also have other intensity peaks in the visible and / or infrared ranges.

[0055] In order to emit this light beam Fl, the light module 21 comprises a light source 23 capable of emitting light rays and an optical unit 24 arranged to project these light rays to form the light beam FL. In the invention, the optical unit 24 may indifferently comprise one or more reflectors, one or more lenses, one or more diaphragms or one or more collimators or a combination of several of these optical elements.

[0056] The light source 23 comprises, for example, a semiconductor generator (not shown), for example gallium nitride or GaN, capable of emitting, by electroluminescence and in response to an electric current passing through it, blue light rays with an emission peak at 450 nm. The light source also comprises a photoluminescent element, in the form of a resin comprising a cerium-doped yttrium aluminum garnet, or CE:YAG, capable of absorbing blue light and, by photoluminescence and in response to the excitation caused by this light, to emit rays of yellow light.

[0057] The photoluminescent element is arranged on the generator such that a portion of the blue light rays excites this element, causing it to emit yellow light rays by photoluminescence. The remaining portion of the blue light rays passes through this element. Thus, the light source 23 simultaneously emits blue and yellow light rays when electrically powered, the resulting light appearing white to the human eye.

[0058] Insofar as the light beam Fl is composed, partially or entirely, of white light, it is possible to use this light beam to participate, partially or entirely, in the performance of a predetermined photometric function, particularly a regulatory one. In this case, the optical unit 24 is arranged to shape this light beam Fl so that its photometric distribution meets the requirements of said function. In the example described, the light beam Fl participates in the performance of a daytime running light, or DRL, function.

[0059] In addition to this photometric function, the light beam Fl allows the system 1 to transmit information, in order to perform functions of detection and evaluation of the position of an object on the road and / or communication.

[0060] For these purposes, the light module 21 is capable of modifying the polarization state of the emitted light beam FL. As will be described in the examples of [Fig.2] to [Fig.5], the light module can be arranged to modify the polarization state continuously, for example by continuously changing the value of the phase shift between the vertical and horizontal components of the light in the light beam Fl, also called the ellipticity angle; or discretely, for example by switching the polarization state between several given states or by switching the value of the ellipticity angle between several discrete values.

[0061] In addition, system 1 includes a computing unit 4.

[0062] Depending on the function that system 1 is to perform, the processing unit 4 can generate either a predetermined signal, intended for the performance of a telemetry function, or a variable signal, intended for the transmission of information, encoded in this signal or sequence, to another vehicle or infrastructure. The generated signal may be a continuous signal or a data sequence, depending on the ability of the light module 21 to modify the polarization state of the light beam Fl continuously or discretely.

[0063] In the case of a telemetry function, the data sequence may be expected to be a binary signal exhibiting various predetermined characteristics, such as, in particular, an autocorrelation peak for a zero time lag and / or low autocorrelation values ​​for a non-zero time lag and / or a Significant length, these characteristics allow for an improved signal-to-noise ratio of the system. Such a sequence could, for example, be generated using a random or pseudo-random code generation algorithm.

[0064] This signal, called modulating, is transmitted by the calculation unit to the modulation unit 22 of the light module 21.

[0065] The modulation unit 22 is then arranged to control the light module 21 in order, on the one hand, to control the emission of the light beam Fl, and on the other hand, to modulate the polarization state of the emitted light beam Fl according to this modulating signal, so that this modulating signal is carried by the changes in the polarization state of the modulated light beam Fl.

[0066] In the example described, the modulation unit 22 includes a generator of a pulse-width modulated control signal. This control signal allows control of a switched-mode power supply (not shown) of the light source 23. Conventionally, the duty cycle of this control signal, set by the modulation unit 22, thus allows control of the average electrical power supplied to the light source 23 and therefore control of the luminous intensity of the light beam Fl, so as to satisfy the requirements of the photometric function it performs.

[0067] In the case of a telemetry function, the light beam Fl is thus emitted until it reaches an object located in the environment of the vehicle, which reflects it towards the receiving module 3. In the case of a communication function, the light beam Fl is thus emitted until it reaches another system located in the environment of the vehicle, equipped with a receiving module equivalent to the receiving module 3. Symmetrically, the receiving module 3 can thus receive a light beam F2 emitted by a transmitting module of another system, equivalent to the transmitting module 2.

[0068] In both cases, the light beam F2 received by the receiving module is thus composed of a part of the light beam Fl, reflected by the object or transmitted by another system, and noise, for example generated by sources of stray light such as urban lighting, car lighting, or even the sun.

[0069] Horn shown in [Fig.1], the receiving module 3 comprises an optical unit 31, downstream of which are provided a plurality of elementary acquisition modules 32. The receiving module 3 also comprises a demodulation unit 33.

[0070] Each of the elementary acquisition modules 32 comprises a plurality of photodetectors, and, for each photodetector, a polarizing filter of a given polarization state, arranged to transmit only to that photodetector a component of said received light beam having said given polarization state. For each elementary acquisition module 32, each polarizing filter is associated to a polarization state different from all other polarization states associated with the other polarizing filters of this module 32.

[0071] The light beam F2 received by the receiving module 3 is thus concentrated by the optical unit 31 onto one or more of the elementary acquisition modules, and then filtered by the polarizing filters. If the light beam F2 contains a component polarized according to a given polarization state, this component will therefore be transmitted, through the polarizing filter of a module 32 associated with this given polarization state, to the photodetector arranged downstream of this filter, and will be blocked by all the other filters of this module 32.

[0072] The photodetectors are identical and each consists of an avalanche photodiode in a silicon photomultiplier. These photodiodes are arranged in a matrix. It should be noted that the dimensions of the photodetectors are on the order of a micrometer. The assembly thus forms a sensor with a spatial reception resolution on the order of 0.1°, and whose detection capabilities, due to the use of avalanche photodiodes, are particularly high, even under degraded acquisition conditions.

[0073] Each photodetector converts the portion of the light beam F2 that it receives, after passing through the associated polarizing filter, into an electrical signal which it transmits to the demodulation unit 33. It is therefore understood that, in the case where the light beam F2 contains a portion of the modulated light beam Fl, reflected by an object or transmitted by another system, the photodetectors will successively convert a portion of this light beam F2 into an electrical signal, according to the polarization state of the modulated beam Fl. The demodulation unit 33 thus receives an electrical signal from an elementary acquisition module 32, composed of a sequence of signals, each transmitted by one of the photodetectors of this elementary acquisition module 32 and thus corresponding to the modulation state filtered by the polarizing filter associated with that photodetector.

[0074] The demodulation unit 33 thus extracts a signal, called demodulated, from this electrical signal transmitted by this elementary acquisition module 32, according to the modulation technique used by the modulation unit 22 to modulate the light beam FL. This demodulated signal is then transmitted to the calculation unit 4.

[0075] In the case where system 1 implements a communication function, the demodulated signal can then be processed by the computing unit 4 and / or transmitted to a computer in the vehicle, to be interpreted, decoded and / or transmitted to equipment or a user of the vehicle.

[0076] In the case of a telemetry function, the processing unit 4 can thus detect the presence of the predetermined modulating signal, with which the modulation unit 22 has modulated the light beam Fl emitted by the light module 21. In this case, the unit The calculation can determine a time of flight separating the emission of the light beam Fl from the reception of the portion of the light beam F2 containing this modulating signal.

[0077] We will now describe an example of the realization of the light system 1, within the framework of a digital modulation, in connection with [Fig.2] which represents this system 1 and with [Fig.3] which represents a method of transmitting and receiving information implemented by the light system 1 of [Fig.2].

[0078] In this example, the light module 21 comprises two light sources 23a and 23, formed by two semiconductor chips emitting light from the same light-emitting diode. These light sources 23a and 23b are selectively controllable by the modulation unit.

[0079] The light module 21 also includes a first linear polarizer 25a arranged downstream of the source 23a and capable of polarizing light emitted by this source 23a along a polarization direction P and a second linear polarizer 25b arranged downstream of the source 23b and capable of polarizing light emitted by source 23b along a polarization direction S. In the example described, each linear polarizer 25a and 25b is formed by a grid polarizer, it being understood that another type of linear polarizer, such as a semi-reflective plate inclined at Brewster's angle with respect to the emission axis of the light source, may be used interchangeably.

[0080] The modulation unit 22 has a polarization modulation alphabet A associating a linear polarization P symbol with a "1" symbol and a linear polarization S symbol with a "0" symbol.

[0081] In order to transmit information, for a telemetry or communication function, the computing unit generates, in a first step, a modulating data sequence Seq and transmits said modulating data sequence Seq to the modulation unit 22.

[0082] For each data item in the Seq sequence, the modulation unit 22 determines, in a second step, using the alphabet A, the polarization state S or P that the light beam Fl must have to encode the value of that data item.

[0083] In a third step, for each data item in the Seq sequence, the modulation unit 22 activates, for a given duration, the light source 23a or 23b associated with the linear polarizer 25a, 25b polarizing according to the polarization state determined for that data item.

[0084] The light beam Fl emitted by the light module 21 is thus composed of a continuous train of linearly polarized elementary beams whose polarization states vary according to the data in the modulating data sequence Seq. The values ​​of the data in this sequence Seq are thus encoded in the successive polarization states of the light beam FL. luminous Fl thus carries the modulating data sequence Seq, while performing a photometric function of the daytime running light type.

[0085] It may be foreseen, for example, that the changes in polarization state will follow one another with a sufficiently high frequency, for example greater than 10 MHz, in particular between 50 MHz and 100 MHz.

[0086] From the point of view of the receiving chain, the receiving module 3 comprises, for each elementary acquisition module 32, two photodetectors 32c and two linear polarizing filters 32a and 32b, each capable of filtering, in a fourth stage, a component of said received light beam F2 having a linear S or P polarization.

[0087] In a fifth step, the demodulation unit 33 can thus, depending on whether an electrical signal comes from one or the other of the photodetectors 32c, determine whether the polarization direction of the portion of the light beam F2 received is of type S or P.

[0088] In a sixth step, the demodulation unit 33, also having the alphabet A, thus generates a demodulated data sequence Seq_d composed, for each polarization direction determined in the previous step, of the symbol associated with this direction in the alphabet A.

[0089] This demodulated data sequence can then be transmitted to the computing unit 4, to be processed there depending on whether the system 1 performs a telemetry or communication function.

[0090] It should be noted that the modulation just described is a binary polarization-shift modulation. It is possible to use a more complex polarization-shift modulation, for example by using a larger number of light sources and polarizers, so that the modulation alphabet has more than two inputs and can encode a sequence of several bits in a given modulation state.

[0091] In addition, instead of light sources and linear polarizers, a spin-led type light source could be used, capable of emitting circularly polarized light and whose direction is controllable by the modulation unit 22. If necessary, the data will be coded, in the modulated light beam Fl, by a left or right circular polarization.

[0092] We will now describe another example of the realization of the light system 1, within the framework of an analog modulation, in connection with [Fig.4] which represents this system 1 and with [Fig.5] which represents a method of transmitting and receiving information implemented by the light system 1 of [Fig.4].

[0093] In this example, the light module 21 comprises a light source 23 and a polarization controller 25. In the example described, the polarization controller 25 comprises a half-wave plate capable of linearly polarizing the light emitted by the light source 23 and a quarter-wave plate capable of polarizing light from the half-wave plate with an elliptical polarization state.

[0094] The quarter-wave plate is rotatably mounted in the light module and the polarization controller 25 includes an actuator, controlled by the modulation unit 22, which drives the quarter-wave plate to rotate towards a given angular configuration.

[0095] In order to transmit information, for a telemetry or communication function, the computing unit generates, in a first step, a modulating signal Sig and transmits this modulating signal Sig to the modulation unit 22.

[0096] The modulation unit 22 generates a control instruction Pol of the polarization controller actuator 25, defining for each value of the modulating signal Sig a rotation angle of the quarter-wave plate.

[0097] In a third step, the modulation unit 22 simultaneously controls the emission of the light beam Fl and the rotation of the quarter-wave plate according to the control instruction Pol.

[0098] Since the angular configuration of the quarter-wave plate directly defines the elliptic angle of the light from the polarization controller, controlling the quarter-wave plate according to the Pol control instruction allows for continuous modulation of the polarization state of the light beam Fl according to the modulating signal Sig. In other words, the modulated light beam Fl has a variable elliptic angle, this variation substantially reproducing the modulating signal Sig. The modulated light beam Fl thus carries the modulating signal Sig, while simultaneously performing a daytime running light photometric function.

[0099] From the point of view of the receiving chain, the receiving module 3 comprises, for each elementary acquisition module 32, a plurality of photodetectors 32e and a plurality of polarizing filters 32d, each capable of filtering, in a fourth step, a component of said received light beam F2 having a given polarization state.

[0100] It is therefore understood that the 32d polarizing filters act as samplers of the value of the polarization state of the received light beam F2, the precision of this sampling depending on the number of polarizing filters used.

[0101] In a fifth step, the demodulation unit 33 can thus, depending on whether an electrical signal comes from one or the other of the photodetectors 32e, convert this signal into a value Val, corresponding to the polarization state filtered by the polarizer filter 32d associated with this photodetector.

[0102] Finally, in a sixth step, the demodulation unit 33 extrapolates a demodulated signal Sig_d from these converted values ​​Val.

[0103] This demodulated signal can then be transmitted to the computing unit 4, to be processed there depending on whether the system 1 performs a telemetry or communication function.

[0104] The preceding description clearly explains how the invention achieves its objectives, namely, to provide a system for a motor vehicle capable of performing both a given photometric function and an information transmission function, and whose signal-to-noise ratio is improved. These objectives are achieved in particular by modulating the polarization of the light beam emitted by the system, this modulation being able to be digital or analog.

[0105] In any event, the invention is not limited to the embodiments specifically described in this document, and extends in particular to all equivalent means and to any technically feasible combination of these means. In particular, it may be possible to use other types of light source than that described, such as a laser diode, a VCSEL, or an SLED. It may also be possible to perform other photometric functions than that described, and in particular low-beam illumination functions or position light signaling functions.

Claims

Demands

1. A light system (1) of a motor vehicle, comprising an emission module (2) comprising a light module (21) capable of emitting a light beam (Fl) whose spectrum has at least a portion in the visible spectrum, the light module being capable of modifying the polarization state of the emitted light beam, and a modulation unit (22) capable of receiving a modulation instruction (Seq, Sig), and arranged to, upon receiving said modulation instruction, control the light module to modulate the polarization state (P, S) of the emitted light beam (Fl);characterized in that it comprises a receiving module (3) capable of receiving a light beam (F2), in which the receiving module comprises an elementary acquisition module (32) comprising a plurality of photodetectors (32c, 32e) each capable of converting a light signal which it receives into an electrical signal, and in that the elementary acquisition module comprises, for each photodetector, a polarizing filter (32a, 32b, 32d) of a given polarization state (S, P) arranged to transmit only to this photodetector, a component of said received light beam having said given polarization state;in that it comprises a calculation unit (4) arranged to generate a modulating signal (Seq, Sig) and to transmit said modulating signal to the modulation unit (22) for the emission of a modulated light beam (Fl) by the light module (21), and in that the calculation unit is arranged to determine a time of flight separating the emission of the emitted modulated light beam from the reception of a received light beam (F2) by the receiving module (3), from one or more electrical signals converted by one or more of said photodetectors (32a, 32b, 32d) of the elementary acquisition module (32) from said received light beam; and in that the light module (2) is arranged so that the light beam (Fl) participates, totally or partially, in the realization of a first predetermined regulatory photometric function.

2. A lighting system (1) according to the preceding claim, characterized in that the lighting module (21) comprises a light source (23), and a polarization controller (25) capable of modifying the polarization state of the light emitted by the light source, and in that that the modulation unit (22) is arranged to, upon receiving said modulation instruction (Seq, Sig), control the polarization controller to drive a sequence of polarization state changes of the light emitted by the light source.

3. A lighting system according to any one of the preceding claims, characterized in that the lighting module (21) comprises a spin-LED type light source capable of emitting light having a circular polarization whose direction is controllable and in that the modulation unit (22) is arranged to, upon receiving said modulation instruction (Seq, Sig), control the light source to drive a sequence of changes in the direction of the circular polarization of the light source.

4. A lighting system (1) according to any one of the preceding claims, characterized in that the lighting module (21) comprises a plurality of light sources (23a, 23b) each selectively controllable and a plurality of polarizing devices (25a, 25b) each associated with one of the light sources and arranged to polarize light emitted by that light source according to a given polarization state (S, P), and in that the modulation unit (22) is arranged to, upon receiving said modulation instruction (Seq, Sig), control said light sources to drive a selective activation sequence of the light sources.

5. Light system (1) according to any one of the preceding claims, characterized in that the modulation unit (22) is capable of receiving a modulating data sequence (Seq), and in that the modulation unit is arranged to, upon receiving said modulating data sequence, control the light module (21) to modulate the polarization state (S, P) of the light beam (Fl) emitted by the light module according to a given polarization modulation alphabet (A) and according to the modulating data sequence.

6. A light system (1) according to any one of the preceding claims, characterized in that it comprises a demodulation unit (33) connected to said photodetectors (32a, 32b, 32d) and arranged to extract a signal (Seq_d, Sig_d), said to be demodulated, from one or more electrical signals converted by one or more of said photodetectors of the elementary acquisition module (32) from said received light beam (F2); and in that the processing unit (4) is arranged to detect, in a demodulated signal extracted by the unit

7. of demodulation, the presence of said modulating signal (Seq, Sig) and to determine, from said detection, a time of flight separating the emission of said emitted light beam (F1) from the reception of said received light beam (F2). Lighting system (1) according to any one of the preceding claims, characterized in that the emission module (2) is arranged in a front headlight of the motor vehicle.

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