Telemetry light system for a vehicle

Abstract

The invention relates to a system (1) for a motor vehicle, the system comprising an emitting module (2) that comprises a light module (21) comprising a first light source (23a) capable of emitting a first light beam (Fia), the spectrum (SI) of which has a first peak (P1) at a wavelength shorter than an intermediate wavelength and a second light source (23b) capable of emitting a second light beam (Flb), the spectrum (S2) of which has a second peak (P2) at a wavelength longer than the intermediate wavelength, the intermediate wavelength being longer than 490 nm, and a control unit (22) arranged to control the first and second light sources so as to simultaneously emit the first and second light beams, the control unit comprising a modulation unit (22a) that is capable of receiving a data sequence (Seq) and is arranged to modulate the first light beam that is emitted on the basis of the received data sequence.

Description

Description Title of the invention: Light telemetry system for a motor vehicle comprising a module for emitting a light beam

[0001] The invention relates to the field of automotive lighting and / or light signaling and to functions for detecting an object by a motor vehicle and estimating the distance separating this object from the vehicle. More specifically, the invention relates to a lighting and / or signaling system for a motor vehicle capable of implementing telemetry functions by means of the light that it emits.

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

[0003] Conventionally, the light source enabling the emission of this light beam is controlled by a pulse width modulated electrical signal, or PWM (from the English "Pulse Width Modulation"). The light source is thus periodically activated and deactivated by this PWM signal, so that the emitted light beam is composed of light pulses succeeding one another with a frequency high enough that the human eye can no longer distinguish them. The intensity of the emitted light beam is a function of the duty cycle of this PWM signal, so that it is possible to control it by adjusting this duty cycle and therefore to perform a photometric function.

[0004] Beyond the realization of one or more photometric functions, such as a daytime running light or dipped-beam lighting, various functions can be implemented by this type of light module. For example, the light source of the light module can be controlled so that the pulses of the emitted light beam carry a data sequence. The lighting system can thus be equipped with a reception module in order to receive the emitted light beam, after reflection on an object in the vicinity of the vehicle. A computing unit of 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 therefore evaluate the distance separating the vehicle from the object.

[0005] In this way, the light beam can retain its original function, namely performing a photometric function, while allowing the lighting 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.

[0006] However, this type of system based on the use of a transmission module capable of both performing a photometric light function and data transmission has disadvantages. Indeed, the reception module intended to receive the light beam carrying the data, whether it is arranged in the same vehicle or in another vehicle, must have at least one photodetector to convert this light beam into an electrical signal in order to demodulate this signal and extract a data sequence.

[0007] However, under certain conditions, this photodetector may see its signal-to-noise ratio significantly degraded, taking into account the sources of stray light present in the vehicle's environment, such as urban lighting, automobile lighting of passing or following vehicles, or even sunlight, and the nature of the objects present in the environment, and in particular their reflective capacity. This degradation of the signal-to-noise ratio can then reduce the accuracy of the calculation unit in estimating the distance of the target object, or even lead to false positive detections.

[0008] In this context, it has been imagined to use particular wavelengths, for which the standardized illumination of the sun is less important, or even non-existent. This is particularly the case, in the visible spectrum, for a range of wavelengths in the blue, between 430 nm and 460 nm. Therefore, if the light source of the emission module emits a light beam whose peak is located at one of these wavelengths, it is possible to use a filter at the level of the reception module which eliminates the bands of wavelengths in which the contribution of sunlight is too important, and to keep only a reduced band centered on this emitted wavelength, or the contribution of sunlight is less important. This increases the signal to noise ratio.

[0009] However, this solution is not entirely satisfactory. Indeed, a photometric function must meet regulatory requirements, particularly in terms of light output and color. For example, a daytime running light, or DRL (from the English "Daytime Running Lamp"), is limited by regulation to a maximum intensity of 1200 cd and must be composed of white light. Typically, light-emitting diodes are used, comprising a blue light generator associated with a phosphorescent element capable of converting part of this blue light into yellow light, the additive combination of the remaining blue light and the yellow light forming white light.

[0010] However, the blue component of this light only represents about 30% of this light from an energy point of view (or radiometric, i.e. with regard to the total energy of this light) and less than 10% from a photometric point of view (i.e. with regard to the energy of the part of this light visible to the human eye, weighted by a sensitivity curve of the human eye), so that the power of this blue component may be insufficient in degraded sunlight conditions or for long-distance detection. In order to maintain a satisfactory signal-to-noise ratio, one solution would be to increase the light power of each of the pulses of the emitted beam. However, this solution would lead to an increase in both the blue and yellow components of the emitted light beam and therefore in the average power of this emitted light beam, which would make it unsuitable for performing the photometric function that it is intended to perform. Another solution would be to increase the number of light sources, but this solution is difficult to reconcile with the requirements of compactness and cost experienced by the field of automotive lighting and light signaling.

[0011] There is therefore a need for a lighting system for a motor vehicle, capable of performing both a given regulatory photometric function and a telemetry function, which is efficient and whose signal-to-noise ratio is optimal in all weather conditions, including in cases of strong sunshine.

[0012] The present invention is placed in this context, and aims to meet this need.

[0013] For these purposes, the subject of the invention is a lighting system of a motor vehicle, comprising an emission module comprising a light module comprising a first light source capable of emitting a first light beam whose spectrum has a first peak lower than an intermediate wavelength and a second light source capable of emitting a second light beam whose spectrum has a second peak higher than the intermediate wavelength, the intermediate wavelength being greater than or equal to 490nm, and a control unit arranged to control the first and second light sources for the simultaneous emission of the first and second light beams, the control unit comprising a modulation unit capable of receiving a data sequence and arranged to modulate said first light beam emitted from the received data sequence.

[0014] Advantageously, the intermediate wavelength is equal to 490nm. Alternatively, the intermediate wavelength is greater than 490nm to encompass the wavelengths corresponding to turquoise light. Where appropriate, the intermediate wavelength is preferably less than 510nm, preferably 500nm.

[0015] For example, a turquoise light can be used to perform signaling functions in an autonomous driving mode.

[0016] The invention thus proposes to decompose the light beam intended to perform a photometric function into two light beams, including a first light beam having a spectrum with a peak substantially in the blue when the first light source emits light of a generally blue color, or in the turquoise when the first light source emits light of a generally turquoise color, and thus making it possible to perform the telemetry function with a good signal-to-noise ratio, taking into account in particular the profile of the spectrum of the light emitted by the sun.

[0017] The first light beam may for example be a pulsed beam, each pulse corresponding to one or more consecutive high values ​​of the data sequence and the interval separating two consecutive pulses corresponding to one or more consecutive low values ​​of the data sequence. Each pulse of the first modulated light beam is emitted with a peak light power, so that the average light power of the first modulated light beam emitted is thus defined by the peak light power and the duty cycle of the modulating data sequence. It is thus possible to detect the presence of this data sequence in this first light beam after reflection on an object in the environment of the vehicle and thus detect the presence of this object as well as estimate its distance from the vehicle.

[0018] The second light beam has a spectrum with a peak in the visible range which complements the spectrum of the first light beam so that the simultaneous emission of these first and second light beams results in an overall light beam of white light. In the invention, the term "simultaneous emission" means that the first and second light beams together perform all or part of the same photometric function. The overall light beam performing this photometric function may result either from an additive association of the first and second light beams, or from alternating pulses of these first and second light beams at a frequency high enough for the light thus formed to appear white to the human eye.

[0019] According to the invention, each light beam is emitted by its dedicated light source(s). In particular, it may be envisaged to use one or more light sources for the emission of each of the light beams. In this way, it is possible to increase the power of the pulses emitted by the first light source(s), in order to increase the efficiency and the signal-to-noise ratio of the telemetry function performed by the first light beam, while adapting the power of the second light beam emitted by the second light source(s), in order to satisfy the regulatory requirements of the photometric function performed by the overall light beam.

[0020] Advantageously, the first light source is arranged so that the spectrum of the first emitted light beam has a first peak in a range from 380 nm to 490 nm, preferably in a range from 420 nm to 460 nm, and the second light source is arranged so that the spectrum of the second light beam has a second peak in a range from 520 nm to 580 nm, or even in a range from 530 nm to 555 nm. Preferably, the first light source will be arranged so that the spectrum of the first light beam has a full width at half maximum, also called FWHM (from the English "Full width at half maximum"), of between 15 nm and 30 nm, and the second ... so that the spectrum of the second light beam has a half-width between 70 nm and 140 nm. In other words, the first light source emits light of a generally blue color, which makes it possible to significantly increase the power of the pulses making up the first light beam. The second light source emits light of a generally yellow color making it possible to supplement the light of a generally blue color, the intensities of the first and second light beams being able to be modulated, in particular through the duty cycles, to obtain an overall light beam of regulatory white color. Advantageously, the first light source is arranged so that the spectrum of the first emitted light beam has a first peak in a range from 480 nm to 510 nm, preferably in a range from 490 nm to 500 nm, and the second light source is arranged so that the spectrum of the second light beam has a second peak in a range from 520 nm to 680 nm, or even in a range from 585 nm to 680 nm. Preferably, the first light source will be arranged so that the spectrum of the first light beam has a full width at half maximum, also called FWHM (from the English "Full width at half maximum"), of between 15 nm and 30 nm, and the second light source will be arranged so that the spectrum of the second light beam has a full width at half maximum of between 70 nm and 140 nm.In other words, the first light source emits light of a generally turquoise color, which makes it possible to significantly increase the power of the pulses making up the first light beam. The second light source emits light of an orange color, for example amber, making it possible to supplement the light of a generally turquoise color, the intensities of the first and second light beams being able to be modulated, in particular through the duty cycles, to obtain an overall light beam of a regulatory white color.

[0021] Preferably, the first light source and at least the second light source are arranged so that the overlap band of their spectra is substantially zero. Alternatively, the first light source and at least the second light source are arranged so that the overlap band of their spectra extends beyond a given wavelength, for example a wavelength of 460 nm when the first light source emits light of a generally blue color, or a wavelength of 500 nm when it emits light of a generally turquoise color. Said overlap band may be, for example, a band in which the spectral power of each of the first and second light beams is greater than 10% of the spectral power of the peak of the first light beam. Such an overlap band may be considered to be substantially zero if its width is less than 5 nm. These characteristics in particular make it possible to guarantee that no photon emitted by the second light source will be added to the first light beam in its portion enabling the telemetry function to be carried out, which would generate noise likely to deteriorate the signal-to-noise ratio of the system for carrying out the telemetry function, in particular in the case where the reception module intended to carry out this function is equipped with a blue filter.

[0022] In an exemplary embodiment, the first light source comprises a generator capable of emitting said first light beam, the first light source being devoid of a photoluminescent element. Preferably, in the case of the first light source, the generator may be a semiconductor generator. The semiconductor may for example be a gallium nitride, or GaN, capable of emitting, by electroluminescence and in response to an electric current passing through it, rays of turquoise and / or blue and / or ultraviolet light.

[0023] Where appropriate, the second light source may comprise a generator capable of emitting light rays. For example, in the case of the second light source, the generator may be a semiconductor generator capable of emitting yellow, orange or amber light. The semiconductor may, for example, be a gallium phosphide, or GaP, a gallium phospho-arsenide, or GaAsP, a silicon carbide, or SiC, capable of emitting, by electroluminescence and in response to an electric current passing through it, rays of yellow, orange or amber light.

[0024] Where appropriate, the second light source may comprise a generator capable of emitting light rays and a photoluminescent element capable of absorbing the majority of said light rays and emitting the second light beam. For example, the semiconductor may be a gallium nitride, or GaN, capable of emitting, by electroluminescence and in response to an electric current passing through it, rays of turquoise and / or blue and / or ultraviolet light. Where appropriate, the semiconductor and / or the doping proportions of the semiconductor may differ between the first and second light sources, so as to ensure that the peak of the spectrum of the first light beam is distinct from the peak of the spectrum of the second light beam.

[0025] The photoluminescent element may for example be in the form of a resin comprising for example a garnet, a silicate, an aluminate, an oxynitride, particles of the quantum dot type, or "quantum dots" or even perovskite, capable of absorbing turquoise or blue or ultraviolet light and, by photoluminescence and in response to the excitation carried out by this light, of emitting rays of yellow light. The photoluminescent element is arranged on the generator of the second light source so that the majority of the rays of blue or ultra- violet excites this element so that it emits, by photoluminescence, orange light rays. Thus, the light source emits mainly yellow, orange or amber light rays when electrically powered.

[0026] The light source could therefore 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 even a superluminescent diode or SLED (from the English "Superluminescent diode").

[0027] Alternatively, it may be provided that the second light source comprises a plurality of light elements each capable of emitting light rays of a different color, in particular red or green. Varying the light intensity of each of these light elements makes it possible to modify the color of the second light beam, which can then complement the first light beam so that the overall light beam has a white color.

[0028] In one embodiment, the control unit comprises a unit for controlling the power supply of the second light source, the control unit being arranged to control said control unit with a pulse width modulated signal with a duty cycle greater than the duty cycle of the received data sequence. The duty cycle of the data sequence may for example be defined by the ratio between the number of high values ​​and the total length of the data sequence.In the invention, the first light source is controlled at high frequency, so that the pulses forming the first light beam follow one another with a frequency greater than 100 kHz, or even greater than 1 MHz, while the second light source is controlled at low frequency, of the order of kHz, with a duty cycle high enough for the pulses of the second light beam to have a temporal extent such that the overall light beam resulting from the first and second light beams has a white color for the human eye.

[0029] Advantageously, the control unit is arranged to determine the duty cycle of the pulse width modulated signal from at least the duty cycle of the received data sequence and a peak power setpoint of the pulses forming the first light beam. In particular, it may be provided that the control unit is arranged to determine the duty cycle of the pulse width modulated signal from the duty cycle of the received data sequence, a peak power setpoint of the pulses forming the first light beam and a photometric function setpoint intended to be carried out at least partially by the first and second light beams.

[0030] In one embodiment, the light module comprises an optical unit capable of receiving the first and second light beams and having a common output face for said first and second light beams. By output face is meant output a wall, a surface or a fictitious region of the optical unit through which the first and second light beams are emitted. The optical unit may thus comprise a lens, a light guide, a reflector, or even a combination of several of these optical elements. In this embodiment, the optical unit is thus a common optical unit arranged to project and / or deflect and / or shape the light rays emitted by the first and second light sources to form said first and second light beams.

[0031] In an exemplary embodiment of the invention, the optical unit comprises a light guide comprising at least one coupling face for the first and second light beams, the guide being arranged so that light rays coupled via said coupling face propagate in the guide by total internal reflection. Where appropriate, the guide comprises decoupling elements capable of decoupling light rays propagating in the guide in the direction of the common output face and the guide comprises, between the coupling face and the decoupling elements, a mixing portion of the first and second light beams coupled to the light guide. This mixing portion makes it possible to spatially homogenize the color of the overall light beam so that this color as well as the lit appearance of the light guide satisfy the regulatory requirements of the photometric function intended to be performed by this overall light beam.

[0032] Advantageously, the light guide has a substantially cylindrical shape, the section of the guide at the mixing portion being polygonal. The section of the guide at the mixing portion may, for example, have a square or hexagonal profile. These shapes make it possible in particular to optimize the mixing of the first and second light beams.

[0033] It may be provided that the light guide has, at a main portion comprising the common output face, an elliptical or circular section, the decoupling elements comprising prisms and / or diffusion members and / or asperities formed in the wall of the main portion at least opposite the output face. The light guide may for example comprise a junction portion between the mixing portion and the main portion, this junction portion being arranged to continuously join the polygonal section of the mixing portion to the elliptical or circular portion of the main portion.

[0034] Alternatively, it may be provided that the section of the mixing portion is identical to the section of the main portion of the light guide comprising the common output face, the length of the section of the mixing portion being sufficient for the first and second light beams to mix along this portion.

[0035] In another exemplary embodiment, the light guide may have the form of a guide sheet comprising a coupling member, such as a collimator, light rays coupled to the sheet via the coupling member propagating by total internal reflection on opposite walls of the guide sheet until reaching a decoupling member arranged to deflect these light rays towards the common exit face of the guide sheet. Where appropriate, the mixing portion may be a translucent portion of the guide sheet or diffusion members provided on a wall of the guide sheet or even a portion of the guide sheet without decoupling members and sufficiently long to achieve the mixing of the first and second light beams.

[0036] Advantageously, the system may comprise at least two first light sources, the first and second light sources being arranged opposite each other on the same coupling face of the light guide, the first light sources framing the second light source. For example, the system may comprise a plurality of first light sources aligned in a first direction and a plurality of second light sources aligned in a second distinct direction and crossing the plurality of first light sources. Alternatively, the first light sources may be provided to totally or partially frame one or more second light sources. These different arrangements also make it possible to promote the mixing of the first and second light beams within the light guide.

[0037] Advantageously, the dimensions of the second light source may be greater than the dimensions of the first light source.

[0038] In one embodiment of the invention, the system comprises a reception module capable of receiving a light beam, the reception module comprising at least one elementary acquisition module comprising a photodetector capable of converting a light signal that it receives into an electrical signal. Where appropriate, the system comprises a calculation unit arranged to generate a modulating data sequence and to transmit said modulating data sequence to the modulation unit for the emission of the first modulated light beam by the light module; the calculation unit being arranged to determine a time of flight separating the emission of the first modulated light beam emitted, from the reception of a light beam received by the reception module, from an electrical signal converted by the photodetector from said received light beam.

[0039] Advantageously, the reception module comprises a plurality of elementary acquisition modules arranged in a matrix and each comprising a photodetector capable of converting a light signal that it receives into an electrical signal. For example, all of the photodetectors can form a sensor, for example a single electronic component. For example, each photodetector may have a width and / or a length of less than about ten micrometers, which makes it possible to obtain a reception field of the elementary acquisition module of at most 0.1° and thus increase the spatial resolution of the receiving module.

[0040] Advantageously, the photodetector of the or each elementary acquisition module is an avalanche photodiode. This type of photodetector is also known as SPAD, from the English "Single-Photon Avalanche Diode". The set of avalanche photodiodes can thus form a photomultiplier on silicon or Si PM (from the English "Silicon PhotoMultiplier"). This type of photodetector makes it possible to detect the incidence of a single photon with a significant gain, for example of the order of 10 5 , and therefore to compensate for the degradation of the signal-to-noise ratio due to external conditions

[0041] According to an exemplary embodiment of the invention, the reception module may comprise an optical unit arranged in front of the elementary acquisition module.

[0042] Advantageously, the system comprises a demodulation unit connected to the photodetector and arranged to extract a data sequence, called demodulated, from an electrical signal converted by this photodetector. Where appropriate, the calculation unit being able to receive a data sequence demodulated by the demodulation unit from an electrical signal converted by the photodetector from a light beam received by the reception module, the calculation unit is arranged to estimate values ​​of a correlation function between said demodulated data sequence and said modulating data sequence and to determine a time of flight separating the emission of said first modulated light beam emitted, from the reception of said received light beam, from the values ​​of the correlation function.

[0043] In other words, in this embodiment, the calculation unit can estimate the values ​​of a correlation function between the demodulated data sequence and the modulating data sequence, each value of the correlation function is associated with a value of a time shift of the modulating sequence, or of the demodulated sequence, used to estimate this value of the correlation function.

[0044] Preferably, the computing unit is arranged to generate said first modulating data sequence, from an initial pseudo-random binary sequence. A pseudo-random binary sequence, or PRBS (from the English "PseudoRandom Binary Sequence"), is a data sequence composed of high values, namely "1", and low values, namely "0". This type of sequence has particularly interesting properties. Indeed, its autocorrelation function is maximum for a zero time shift, that is to say when the sequence is compared to itself, and has a value substantially lower than this maximum for all other time shifts, that is to say when the sequence is compared to time-shifted versions of itself. Furthermore, the cross-correlation function between two pseudo-random binary sequences is substantially lower than the maximum of the autocorrelation functions of these sequences.Finally, this type of sequence is usually generated using a feedback shift register. linear, or LFSR (from the English “Linear Feedback Shift Register”), which produces a periodic recurring sequence whose pattern is a pseudo-random binary sequence.

[0045] Given the autocorrelation properties of pseudo-random binary sequences, the correlation function thus estimated will be maximum for the time shift value corresponding to the time of flight of the modulated light beam emitted, reflected and then received, even in the event of significant noise. Consequently, the computing unit can identify this time shift value associated with the maximum value of the correlation function with significant precision and deduce therefrom the distance separating the object on which the beam was reflected and the motor vehicle. Furthermore, given the cross-correlation properties, it thus appears unlikely that the reception of a modulated light beam emitted by an equivalent system of another motor vehicle will lead to the detection of a false positive.Finally, we understand that the detection is carried out not on a single pulse but on a complete data sequence, so that the signal-to-noise ratio of the system is improved.

[0046] In one embodiment of the invention, the calculation unit is arranged to estimate each value of the correlation function between said demodulated data sequence and said first modulating data sequence by evaluating the cross-correlation of the demodulated data sequence and the first modulating data sequence delayed by a given duration 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 first modulating sequence used to estimate this value of the correlation function. The calculation unit is thus arranged to identify the time shift value associated with the maximum value of the cross-correlation function.

[0047] Advantageously, the elementary acquisition module includes a blue light filter. In addition to the fact that the properties of the spectrum of light emitted by the sun make it possible to increase the signal-to-noise ratio in the case where the telemetry function uses a blue-colored beam, it should be noted that, in the case where the first light beam is emitted from a semiconductor light source, such as a light-emitting diode, this light beam is obtained from a blue light generator emitting photons quickly, with respect to the conversion speed of a phosphorescent element. Therefore, in a context of obstacle detection by analyzing a time of flight of a light beam, the resolution of evaluation of the time of flight will necessarily be higher if the evaluation is made from only blue light rather than from another wavelength range, or even from the entire visible spectrum.The use of a blue light filter thus makes it possible to reduce the uncertainty in detecting the distance of an obstacle from the vehicle.

[0048] It will be possible to provide that the blue light filter includes an optical filter of the type bandpass placed in front of the photodetector, said optical filter being capable of transmitting a wavelength range and being arranged so that the width of said range is substantially less than 20 nm and said filter has a transmission peak at a wavelength of substantially 450 nm. In the present invention, the term "width of a wavelength range of a filter" means a wavelength range in which the transmission coefficient of the filter is at least 80%. In the present invention, the term "transmission peak of a filter" means the wavelength of the range of the filter for which the transmission coefficient of the filter is maximum.

[0049] Alternatively, in the case where the first light source emits turquoise light, the elementary acquisition module comprises a turquoise light filter, offering advantages similar to those provided by a blue light filter when a first blue light source is used. In the same way, the turquoise light filter may comprise a bandpass type optical filter placed in front of the photodetector, said optical filter being capable of transmitting a wavelength range and being arranged so that the width of said range is substantially less than 20 nm, and that said filter has a transmission peak at a wavelength close to 494 nm to within 10 nm.

[0050] 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.

[0051] Advantageously, the emission module is arranged so that the first and second light beams participate together, totally or partially, in the realization of a predetermined regulatory photometric function.

[0052] For example, it could be a daytime running light or DRL (from the English “Daytime Running Lamp”), which has the advantage of being emitted in a wide field with low intensity.

[0053] The invention also relates to a front headlight of a motor vehicle comprising a transmission module, and optionally a reception module, according to the invention.

[0054] The present invention is now described with the aid of examples which are solely illustrative and in no way limitative of the scope of the invention, and from the accompanying drawings:

[0055] [Fig. 1] represents, schematically and partially, a view of a system of a motor vehicle according to an exemplary embodiment of the invention;

[0056] [Fig. 2] represents, schematically and partially, an example of the realization of the light sources of the system of [Fig. 1];

[0057] [Fig. 3] represents, schematically and partially, the emission spectrum of a light beam formed simultaneously by the light sources of [Fig. 2];

[0058] [Fig. 4] represents, schematically and partially, an example of operation of the system of [Fig. 1] during the implementation of a telemetry method; and

[0059] [Fig. 5] represents, schematically and partially, an example of the embodiment of an optical unit of the transmission module of the system of [Fig. 1].

[0060] In the following description, elements which are identical, by structure or by function, appearing in different figures retain, unless otherwise specified, the same references.

[0061] [Fig. 1] shows a system 1 of a motor vehicle according to an exemplary embodiment of the invention.

[0062] 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.

[0063] 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 of the motor vehicle, without departing from the scope of the present invention.

[0064] The emission module 2 comprises a light module 21 intended to emit a light beam Fl and a control unit 22.

[0065] The light module 21 comprises a first light source 23a capable of emitting light rays and an optical unit 24 arranged to project these light rays to form a first light beam Fia. The light module 21 also comprises a second light source 23b capable of emitting light rays, the optical unit 24 being arranged to project these light rays to form a second light beam Flb.

[0066] In the invention, the optical unit 24 thus has a common output face for said first and second light beams Fia and Flb. It may indifferently comprise one or more reflectors, one or more lenses, one or more diaphragms, one or more light guides or one or more collimators or even a combination of several of these optical elements. A specific embodiment of the optical unit 24 will be described later.

[0067] [Fig. 2] shows an example of the embodiment of the light sources 23a and 23b and [Fig. 3] shows the spectrum of the light beam formed simultaneously by these light sources 23a and 23b.

[0068] The light source 23a comprises a semiconductor generator 23al, for example a gallium nitride or GaN, capable of emitting, by electroluminescence and in response to an electric current passing through it, rays of blue light intended to form the first light beam Fia. It may be provided that the generator 23a is arranged in a reflective cavity. The light source 23a is also devoid of a photoluminescent element intended to convert all or part of these rays of blue light into rays of light of another color. The SI spectrum of the first light beam Fia thus has an emission peak PI at 445 nm and a full width at half maximum FWHM1 of 20 nm.

[0069] The light source 23b also comprises a semiconductor generator 23bl, for example a gallium nitride or GaN, capable of emitting, by electroluminescence and in response to an electric current passing through it, rays of blue light. The light source 23b further comprises a photoluminescent element 23b2 superimposed on the generator 23bl, in the form of an organic or inorganic encapsulant, in particular 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 carried out by this light, of emitting rays of yellow, orange or amber light.

[0070] The photoluminescent element 23b2 is arranged on the generator 23bl so that a major part of the blue light rays emitted by the generator 23bl excites this element 23b2 so that it emits, by photoluminescence, rays of yellow, orange or amber light intended to form substantially entirely the second light beam Flb.

[0071] The S2 spectrum of the first light beam Flb thus has an emission peak P2 at 550 nm and a full width at half maximum FWHM2 of 100 nm.

[0072] As shown in [Fig. 3], the position of the emission peaks PI and P2 as well as the half-widths FWHM1 and FWHM2 ensure that the overlap band of the spectra SI and S2 extends beyond a wavelength of 460 nm.

[0073] Thus, the light beams Fia and Flb, when emitted simultaneously, under the control of the control unit 22, form an overall light beam whose spectrum corresponds to the superposition of the emission spectra SI and S2 as shown in [Fig. 3]. Depending on the power of the light beams Fl and Flb, the color of this overall light beam may then appear white to the human eye.

[0074] To the extent that the color of this overall light beam appears white, it is possible to use this light beam to participate, partially or totally, in the realization of a predetermined photometric function, in particular regulatory. In this case, the optical unit 24 is arranged to shape this overall light beam so that its photometric distribution satisfies the requirements of said function. For example, it may be provided that the overall light beam participates in the realization of a function of the daytime running light type, or DRL.

[0075] It will be noted that the invention is not limited to the combination of a single first light source 21a and a single second light source 21b and that the number of first and second light sources may be varied without departing from the scope of the present invention. Similarly, it may be envisaged to modify the propor- tions of the semiconductor components of the generator 23al, 23bl and / or of the photoluminescent element 23b2 of one and / or the other of the first and second light sources 23a, 23b to move the peaks Pl, P2 and / or modify the amplitude of the widths at half-maximum FWM1, FWHM2 of the spectra SI and S2 without departing from the scope of the present invention. It will be possible in particular to envisage replacing the second light source 23b described in [Fig. 2] by chips emitting red and green light respectively, selectively controllable so as to be able to control the color of the light beam that these chips emit so that it complements the first light beam Fia to form an overall light beam of substantially white color.

[0076] In addition to this photometric function, the first light beam Fia allows the system 1 to perform functions of detecting and evaluating the position of an object on the road, as will be described in connection with [Fig. 4] which represents a telemetry method implemented by the lighting system 1 using the lighting module 21.

[0077] For this purpose, the system 1 comprises a calculation unit 4 and the control unit 22 comprises a modulation unit 22a intended to control the first light source 23a as well as a control unit 22b intended to control the power supply of the second light source 23b.

[0078] In a first step, the calculation unit 4 periodically generates an initial data sequence Seq. The initial sequence Seq is, in the example described, a binary type sequence, composed of “0” and “1”, pseudo random and of maximum size, also called M-sequence, having a duty cycle of 50%.

[0079] In a second step, the modulation unit 22a modulates the first light beam Fia emitted by the first light source 23a of the light module 21, from this data sequence Seq, for example by controlling the electrical power supplied to the first light source 23a.

[0080] In the example described, the modulation unit 22a comprises a generator of a pulse frequency modulated control signal. This control signal makes it possible to control a switching power supply (not shown) of the first light source 23a. Conventionally, the frequency setpoint of this control signal, set by the modulation unit 22a, thus makes it possible to control the average electrical power supplied to the first light source 23a, and therefore to control the light intensity of the first light beam Fia.

[0081] Thus, the modulation unit 22a converts the data sequence Seq into a modulating signal and modulates the initial control signal using this modulating signal. In other words, the first light beam Fia thus emitted under the control of the modulated signal Sseq is composed of a train of light pulses. The pulses follow one another with a sufficiently high variable frequency, for example greater than 100 KHz, or even higher than 1 MHz, in particular between 50 MHz and 100 MHz, so that the human eye can no longer distinguish them. Furthermore, the amplitude, width and / or position of each pulse with respect to the period allows the first light beam Fia to transport the data sequence to the receiving module 3.

[0082] It will be noted that in the example described, each light pulse corresponds to a bit of value “1” of the modulating sequence Seq. The average power of a portion of the first light beam Fia containing the sequence Seq is thus defined by the number of bits of value “1” of this sequence Seq with respect to the total number of bits of this first sequence Seq, by the duration T p pulses and by the peak power P p of these impulses.

[0083] It will also be noted that other types of modulation may be used indifferently within the framework of the present invention, and in particular pulse code modulation (or PGM for “Puise Code Modulation”), pulse amplitude modulation (or PAM for “Puise Amplitude Modulation”), pulse width modulation (or PWM for “Pulse Width Modulation”) or even pulse position modulation (or PPM for “Puise Position Modulation”).

[0084] Concomitantly with the second step, the control unit 22 determines a DC duty cycle and the control unit 22b controls the electrical power supplied to the second light source 23b according to this duty cycle.

[0085] In the example described, the control unit comprises a generator of a pulse width modulated control signal Spwm according to the DC duty cycle. This control signal makes it possible to control a switching power supply (not shown) of the second light source 23b. Conventionally, the DC duty cycle of this control signal, set by the control unit 22, thus makes it possible to control the average electrical power supplied to the second light source 23b, and therefore to control the light intensity of the second light beam Flb.

[0086] In other words, the second light beam Flb thus emitted under the control of the signal Spwm is composed of a train of light pulses. The pulses follow one another with a variable frequency that is sufficiently high, although significantly lower than that of the first light beam Fia, for example of the order of KHz, so that the human eye can no longer distinguish them. It will be noted that in the embodiment shown, the control unit 22b is of the low-frequency type while the modulation unit 22a is of the high-frequency type.

[0087] Furthermore, the duty cycle DC will be determined by the control unit 22 so that the duration TH of the pulses of the second light beam Flb as well as the period T of these pulses are much longer than the duration Tp of the pulses of the first light beam Fia.

[0088] More precisely, in the invention, the peak power P pof the pulses of the first light beam Fia can be significantly increased compared to known solutions, since this increase in power has no impact on the power of the second light beam Fib. It is thus possible to increase the detection distance and reduce the signal-to-noise ratio of the telemetry function.

[0089] However, the average power of the overall light beam formed by the first and second light beams Fia, Flb is constrained by the regulatory requirements governing the photometric function that this overall light beam must perform. According to the duty cycle of the data sequence Seq, this peak power P p, and the type of photometric function that the overall light beam must perform, the calculation unit 4 can thus determine a DC duty cycle such that the ratio of blue and yellow in this overall light beam is correct and that the regulatory requirements of the photometric function are met.

[0090] The light beam composed of the first and second light beams Fia, Flb is thus emitted until it reaches an object O, located in the environment of the vehicle, which reflects it in the direction of the reception module 3. The light beam F2 received by the reception module is thus composed of a part of the overall light beam Fia, Flb reflected by the object O and of noise, for example generated by sources of stray light such as urban lighting, automobile lighting, or even the sun.

[0091] As shown in [Fig. 1], the reception module 3 comprises an optical unit 31, downstream of which a plurality of elementary acquisition modules 32 are provided. The reception module 3 also comprises a demodulation unit 33.

[0092] Each of the elementary acquisition modules 32 comprises a photodetector 32a as well as a blue light filter 32b arranged in front of the photodetector 32a. The light beam F2 received by the reception module 3 is thus concentrated by the optical unit 31 on one or more of the photodetectors 32a, after passing through the filters 32b.

[0093] Each 32b filter is a bandpass type blue light filter, the transmission peak of which is centered on a wavelength of 450 nm and capable of letting through light rays whose wavelength is between 440 and 460 nm, the remainder being absorbed by this 32b filter.

[0094] When the sunlight conditions in the vicinity of the vehicle are particularly strong, sunlight is thus added to the light beam F2 received by the receiving module 3. The illumination of the sun, in the visible spectrum, is significantly greater than that of a photometric function such as a daytime running light. Therefore, the light beam F2 received by the receiving module 3 is composed on the one hand of the light beams Fia, Flb emitted by the transmitting module 2 and of the sunlight. The intensity levels of this beam F2 greatly exceed those of the beam Fl for the wavelength ranges of the visible domain. On the other hand, due to the absorption of part of the light by the atmospheric layers, there are dips in the solar spectrum in which the illumination is weaker, or even zero. This is particularly the case in the visible spectrum, for the wavelength range between 440 nm and 460 nm.

[0095] Each filter 32b thus makes it possible to minimize on the one hand the influence of the sun and on the other hand the component resulting from the second light beam Flb on the beam F2, by eliminating all the wavelengths of the beam F2 with the exception of a range comprising the wavelength of the peak of the spectrum of the first emitted light beam Fia.

[0096] It will also be noted that the filter 32b then makes it possible to retain only the component of the beam F2 corresponding to the light rays by the first light source 23a, the yellow light rays being emitted by the second light source 23b with a longer response time taking into account the delay introduced by the photoluminescence. Therefore, to the extent that the detection is carried out solely from the blue light received by the reception module 3, the resolution of evaluation of the time of flight of the light beam F2 and / or the data transmission rate between the transmission module 2 and the reception module 3 is thus improved.

[0097] The photodetectors 32a are identical and are each formed by an avalanche photodiode of a silicon photomultiplier. These photodiodes are distributed in a matrix manner. It should be noted that the dimensions of the photodetectors are of the order of a micrometer. The assembly thus forms a sensor whose spatial reception resolution is of the order of 1°, or even 0.1°, and whose detection capabilities, due to the use of avalanche photodiodes, are particularly high, even in the case of degraded acquisition conditions.

[0098] In a third step, each of the photodetectors 32a converts the portion of the light beam F2 that it receives into an electrical signal Sel that it transmits to the demodulation unit 33, which can then extract from it a data sequence Seq2, called demodulated, in a fourth step.

[0099] In the example described, the demodulation unit 33 can for example count, from the electrical signal Sel, the number of photons received by an elementary acquisition module 32 during a time interval corresponding to a pulse duration T p , then determine by thresholding with respect to a value determined from the peak power P p whether or not this quantity of photons corresponds to a pulse of the first light beam Fia, and therefore to a bit of value “1” or to a bit of value “0”.

[0100] The demodulated binary sequence Seq2 is thus transmitted to the calculation unit 4, which estimates, in a fifth step, values ​​of a correlation function Fcorr between the modulating sequence Seq and the demodulated sequence Seq2.

[0101] The calculation unit 4 thus evaluates, for a plurality of time shift values, the value of the cross-correlation, by means of a cyclic convolution product, between the demodulated sequence Seq2 and the modulating sequence Seq delayed according to each of the time shift values.

[0102] Taking into account the autocorrelation and cross-correlation properties of pseudo-random binary sequences, the correlation function Fcorr will thus be maximum for a time shift value corresponding to the time of flight of the light beam Fia, Flb, separating the instant when it is emitted by the transmission module 2 and the instant when it is received by the reception module 3, the modulating sequence Seq delayed by this value thus corresponding substantially to the demodulated sequence Seq2, apart from the noise.

[0103] In a sixth step, the calculation unit 4 identifies this maximum value of the correlation function Fcorr and estimates the value T of this flight time of the light beam Fia, Flb between the object O and the vehicle, associated with this maximum value.

[0104] In a seventh step, the calculation unit 4 estimates the distance d separating the object O from the vehicle.

[0105] In connection with [Fig. 5], we will now describe an example of the embodiment of the optical unit 24.

[0106] In the example of [Fig. 5], the optical unit 24 comprises a cylindrical light guide 5 formed by a single solid part, for example made of polymethyl methacrylate (PMMA) or polycarbonate (PC).

[0107] This light guide 5 comprises a coupling face 51, or input face, opposite which the first and second light sources 23a and 23b are arranged.

[0108] In the example described, the light module 21 comprises three first light sources 23a, aligned along a diagonal of the coupling face 51, and two second light sources 23b, aligned along another diagonal of the coupling face 51 crossing the first diagonal. Other arrangements of the first and second light sources 23a and 23b may be designed without departing from the scope of the present invention.

[0109] The light guide 5 comprises three portions, namely a mixing portion 52 extending from the coupling face 51, a joining portion 53 extending from the mixing portion 52, and a main portion 54 extending from the joining portion 53.

[0110] The coupling face 51 makes it possible to couple to the light guide 5 light rays, emitted by the first and second light sources 23a and 23b and penetrating into the guide 5 via this coupling face 51. The light rays thus propagate by total internal reflection in the light guide 5.

[0111] Furthermore, the mixing portion 52 is of hexagonal section S52 and is devoid of any decoupling member making it possible to stop the propagation by total internal reflection of the light rays. This hexagonal section thus makes it possible to optimize mixing the light rays emitted by the first and second light sources 23a and 23b in order to spatially homogenize the color of the overall light beam.

[0112] The main portion 54 is of substantially circular section S54 and comprises on a part of its periphery prisms 54a defining on an opposite part of the periphery of the main portion 54 an exit face 54b of the light guide 5.

[0113] These prisms 54a form decoupling elements making it possible to reflect, by total internal reflection, light rays propagating in the guide towards the exit face 54b, which is consequently a common exit surface for the light rays emitted by the first and second light sources 23a and 23b.

[0114] It is understood that, without departing from the scope of the invention, the same advantages can be obtained for a lighting system comprising a first turquoise light source, in particular when said lighting system comprises a turquoise optical filter.

[0115] The foregoing description clearly explains how the invention makes it possible to achieve the objectives it has set itself, namely to provide a lighting system for a motor vehicle, capable of performing both a given regulatory photometric function and a telemetry function, and in which it is possible to increase the power of the component of the light beam performing the telemetry function without increasing the number of light sources and while satisfying the regulatory requirements of the photometric function. These objectives are notably achieved on the one hand using an emission module provided with two light sources, one of which is dedicated to performing the telemetry function while the other complements the first to perform the photometric function.

[0116] In any event, the invention cannot be limited to the embodiments specifically described in this document, and extends in particular to any equivalent means and to any technically effective combination of these means. In particular, other configurations of the emission module may be provided, and in particular an emission module using other types of light source than those described, such as a laser diode, a VCSEL or a SLED or an RGB diode, or other types of optical unit than that described, such as a guide sheet. It may also be possible to provide other photometric functions than that described, and in particular lighting functions of the dipped beam type or signaling functions of the position light or direction indicator type. It may also be possible to envisage other wavelength ranges than those described.

Claims

Claims

1. Lighting system (1) of a motor vehicle, comprising an emission module (2) comprising a light module (21) comprising a first light source (23a) capable of emitting a first light beam (Fia) whose spectrum (SI) has a first peak (PI) less than an intermediate wavelength and a second light source (23b) capable of emitting a second light beam (Flb) whose spectrum (S2) has a second peak (P2) greater than the intermediate wavelength, the intermediate wavelength being greater than or equal to 490nm, and a control unit (22) arranged to control the first and second light sources for the simultaneous emission of the first and second light beams, the control unit comprising a modulation unit (22a) capable of receiving a data sequence (Seq) and arranged to modulate said first light beam emitted from the received data sequence.

2. Light system (1) according to the preceding claim, characterized in that the intermediate wavelength is equal to 490nm.

3. Light system (1) according to the preceding claim, characterized in that the first light source (23a) is arranged so that the spectrum (SI) of the first light beam (Fia) emitted has a first peak (PI) in a range from 380 nm to the intermediate wavelength, in that the second light source (23b) is arranged so that the spectrum (S2) of the second light beam (Flb) has a second peak (P2) in a range from 520 nm to 580 nm.

4. Lighting system (1) according to the preceding claim, characterized in that the first and second light sources (23a, 23b) are arranged so that the overlap band of their spectra (S1, S2) is substantially zero.

5. Lighting system (1) according to one of the preceding claims, characterized in that the first light source (23a) comprises a generator (23al) capable of emitting said first light beam (Fia), the first light source being devoid of a photoluminescent element, and in that the second light source (23b) comprises a generator (23bl) capable of emitting light rays and a photoluminescent element (23b2) capable of absorbing the majority of said light rays and emitting the second light beam (Flb).

6. Lighting system (1) according to one of the preceding claims, characterized in that the control unit (2) comprises a control unit (22b) for the electrical power supply of the second light source (23b), the control unit being arranged to control said control unit with a pulse width modulated signal (Spwm) with a duty cycle (DC) greater than the duty cycle of the received data sequence (Seq).

7. Lighting system (1) according to the preceding claim, characterized in that the control unit (2) is arranged to determine the duty cycle (DC) of the pulse width modulated signal (Spwm) from at least the duty cycle of the received data sequence (Seq) and a peak power setpoint (P p ) pulses forming the first light beam (Fia).

8. Lighting system (1) according to one of the preceding claims, characterized in that the light module (21) comprises an optical unit (24, 5) capable of receiving the first and second light beams (F21a, F21b) and having a common exit face (54b) of said first and second light beams.

9. Lighting system (1) according to the preceding claim, characterized in that the optical unit (24) comprises a light guide (5) comprising at least one coupling face (51) of the first and second light beams (Fia, Flb), the guide being arranged so that light rays coupled via said coupling face propagate in the guide by total internal reflection, in that the guide comprises decoupling elements (54a) capable of decoupling light rays propagating in the guide in the direction of the common output face (54b) and in that the guide comprises, between the coupling face and the decoupling elements, a mixing portion (52) of the first and second light beams coupled to the light guide.

10. Lighting system (1) according to the preceding claim, characterized in that the light guide (5) has a substantially cylindrical shape, the section (S52) of the guide at the level of the mixing portion (52) being polygonal.

11. Lighting system (1) according to one of the preceding claims, characterized in that it comprises a reception module (3) capable of receiving a light beam (F2), in which the reception module comprises at least one elementary acquisition module (32) comprising a photodetector (32a) capable of converting a light signal that it receives into an electrical signal (Sel), in that it comprises a calculation unit (4) arranged to generate a modulating data sequence (Seq) and to transmit said modulating data sequence to the modulation unit (22a) for the emission of the first light beam (Fia) modulated by the light module (21); and in that the calculation unit is arranged to determine a flight time (T) separating the emission of the first modulated light beam emitted, from the reception of a light beam received by the reception module (3), from an electrical signal converted by the photodetector from said received light beam.

12. Lighting system (1) according to the preceding claim, characterized in that it comprises a demodulation unit (33) connected to the photodetector (32a) and arranged to extract a data sequence (Seq2), called demodulated, from an electrical signal (Sel) converted by this photodetector; and in that, the calculation unit (4) being able to receive a data sequence demodulated by the demodulation unit from an electrical signal converted by the photodetector from a light beam (F2) received by the reception module (3), the calculation unit is arranged to estimate values ​​of a correlation function (Fcorr) between said demodulated data sequence and said modulating data sequence (Seq) and to determine a time of flight (T) separating the emission of said first modulated light beam (Fl) emitted, from the reception of said received light beam, from the values ​​of the correlation function.

13. Lighting system (1) according to one of claims 11 or 12, characterized in that the elementary acquisition module (32) comprises a filter allowing passage of light corresponding to the first peak (PI) of the first light beam (Fia), for example blue light or turquoise light.

14. Lighting system (1) according to one of the preceding claims, characterized in that the emission module (2) is arranged in a front headlight of the motor vehicle.

15. Lighting system (1) according to the preceding claim, in which the emission module (2) is arranged so that the first and second light beams (Fia, Flb) participate together, totally or partially, in the realization of a predetermined regulatory photometric function.

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