Light telemetry system for a motor vehicle comprising a module for emitting a light beam

Abstract

The invention relates to a telemetry system (1) of a motor vehicle comprising a first transmission module capable of transmitting a first light beam (F1a) modulated by a first modulating sequence (Seqa); a second transmission module (2b) capable of transmitting a second light beam (F1b) modulated by a second modulating sequence (Seqb); a reception module (3a, 3b) capable of receiving a light beam (F2) and extracting therefrom a demodulated data sequence (Seq2); a calculation unit (4) arranged to generate first and second modulating data sequences (Seqa, Seqb) of pseudo-random binary type and of which the peak of the cross-correlation function (Fcorr) is less than a threshold value (Vs) and arranged to estimate values ​​of a correlation function (Fcorr) between said demodulated data sequence (Seq2) and said first modulating data sequence (Seqa). Figure to be published with the abstract: Fig. 1

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, 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 to perform a photometric function, while allowing the lighting system to implement a telemetry function, which can be particularly advantageous. for example for driver 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 drawbacks. 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 comprise at least one photodetector to convert this light beam into an electrical signal in order to demodulate this signal and extract a data sequence therefrom.

[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 environment of the vehicle, 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 may then reduce the accuracy of the calculation unit in estimating the distance of the target object, or even lead to false positive detections.

[0008] Furthermore, in other conditions, where the light of a system is emitted by several light sources, there is a possibility of encountering delays due to the offset of positioning of the object to be detected relative to the different emission modules, this delay can have the effect of creating interference and potentially false detections.

[0009] This is particularly the case when each of the left and right headlights of the motor vehicle are equipped with a light module making it possible to perform both a photometric function and a telemetry function. When the object to be detected is located in an angular range that is substantially off-axis relative to the motor vehicle, the flight time of the light beam emitted by the right headlight may be greater than that of the light beam emitted by the left headlight, the time difference between these flight times being greater than the pulse duration making it possible to encode the data sequence for telemetry. This time difference thus creates interference that harms the signal-to-noise ratio of the lighting system.

[0010] There is thus 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 for all positions of an object to be detected.

[0011] The present invention is placed in this context, and aims to meet this need.

[0012] For this purpose, a motor vehicle telemetry system has been developed. comprising a first emission module comprising a light module capable to emit a first light beam, and a first modulation unit capable of receiving a first data sequence and arranged to modulate the first light beam emitted from said first modulating sequence, a second emission module comprising a light module, distant from the light module of the first emission module, capable of emitting a second light beam, a second modulation unit capable of receiving a second data sequence and arranged to modulate the second light beam emitted from the second modulating sequence, at least one reception module capable of receiving a light beam, the reception module comprising at least one elementary acquisition module comprising at least one photodetector capable of converting a light signal that it receives into an electrical signal and a demodulation unit connected to the photodetector and arranged to extract a data sequence, called demodulated,from an electrical signal converted by this photodetector, a calculation unit arranged to generate first and second sequences of modulating data of pseudo-random binary type and whose peak of the cross-correlation function is lower than a given threshold value, to transmit the first sequence of modulating data to the modulation unit of the first emission module for the emission of a first light beam modulated by the first emission module, to transmit the second sequence of modulating data to the modulation unit of the second emission module for the emission of a second light beam modulated by the second emission module.

[0013] According to the invention, 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 first 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.

[0014] The invention thus proposes to decompose the light beam emitted by the telemetry system of the motor vehicle into two light beams each emitted by a given light module. The first and second light beams are thus emitted simultaneously and together perform all or part of a photometric function.

[0015] Each of these first and second light beams may for example be a pulsed beam, each pulse corresponding to one or more consecutive high values ​​of the first, respectively second, data sequence and the interval separating two consecutive pulses corresponding to one or more consecutive low values ​​of this data sequence. Each pulse of these first and second modulated light beams are 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 first, respectively, modulating data sequence.

[0016] The light beam received by the reception module thus contains the reflection of these first and second light beams by an object to be detected. The data sequence demodulated by the demodulation unit is therefore composed of the first and second modulating sequences, each delayed by a different delay and noise. Each value of the correlation function estimated by the calculation unit is associated with a value of a time shift of the first modulating sequence, or of the demodulated sequence, used to estimate this value of the correlation function. The correlation function between this demodulated data sequence and one of the modulating sequences is therefore a function on the one hand of the autocorrelation of this modulating sequence and of the cross-correlation of the first and second modulating sequences.

[0017] It is thus understood that, to the extent that the peak of the cross-correlation function of the modulating data sequences is less than a given threshold value, or is even substantially zero, the correlation function thus depends only on the autocorrelation of the first modulating sequence. It is thus possible to detect the presence of this first data sequence in the received 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. In this way, the interference that can be induced by a lateral offset of an object to be detected with respect to the motor vehicle is substantially reduced, or even cancelled out.

[0018] In one embodiment of the invention, each of the first and second light modules is capable of emitting a first, respectively a second, light beam whose spectrum has a peak at a wavelength in the visible, in particular between 400 nm and 500 nm. Advantageously, each of the first and second light modules comprises 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.

[0019] 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 blue light. The photoluminescent element may, for example, be in the form of a resin comprising a cerium-doped yttrium and aluminum garnet, or CE:YAG, capable of absorbing blue light and, by photoluminescence and in response to the excitation carried out by this light, to emit rays of yellow light. The photoluminescent element is arranged on the generator so that a part of the blue light rays excites this element so that it emits, by photoluminescence, rays of yellow light. The other part of the blue light rays passes through this element. Thus, the light source simultaneously emits, when electrically powered, rays of blue and yellow light, the light thus formed appearing white to the human eye.

[0020] 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 even a superluminescent diode or SLED (from the English “Superluminescent diode”).

[0021] Advantageously, each of the first and second light modules may comprise an optical unit arranged to project the light rays emitted by the light source to form said first, respectively second, light beam.

[0022] Advantageously, the first, respectively the second, modulation unit is arranged to generate a pulse width modulated control signal, to modulate said control signal from the first, respectively the second, modulating data sequence and to control the emission of said first, respectively the second, light beam by the first, respectively the second, light module from the modulated control signal. For example, the first, respectively the second, modulation unit may be arranged to convert the first, respectively the second, modulating data sequence into a modulating signal and to modulate, for example in amplitude, frequency or phase, the control signal with this modulating signal.

[0023] Where appropriate, the first, respectively the second, modulation unit may be arranged to control the light source of the first, respectively second, light module, and in particular an electrical power supply supplied to this light source, to modulate the first, respectively second, light beam.

[0024] 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 therefore to increase the spatial resolution of the reception module.

[0025] 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 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 significant gain, for example of the order of 106, and therefore to compensate for the degradations of the signal-to-noise ratio due to external conditions.

[0026] According to an exemplary embodiment of the invention, the reception module may comprise an optical unit arranged in front of the elementary acquisition module.

[0027] In a particular embodiment, the calculation unit is arranged to generate the first and second sequences of modulating data from at least one same initial sequence of pseudo-random binary type.

[0028] A pseudo-random binary sequence, or PRBS (from the English "PseudoRandom Binary Sequence"), is a data sequence composed of high values, namely "1s", and low values, namely "0s". 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 significantly lower than this maximum for all other time shifts, that is to say when the sequence is compared to time-shifted versions of itself.

[0029] Furthermore, the cross-correlation function between two pseudo-random binary sequences is significantly lower than the maximum of the autocorrelation functions of these sequences. Finally, this type of sequence is generally generated by means of a linear feedback shift register, or LFSR (from the English "Linear Feedback Shift Register"), which produces a periodic recurring sequence whose pattern is a pseudo-random binary sequence.

[0030] Taking into account the autocorrelation properties of pseudorandom 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 then received, even in the event of significant noise.

[0031] Consequently, the calculation 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.

[0032] Furthermore, taking into account 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 would lead to the detection of a false positive.

[0033] Finally, it is understood 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.

[0034] 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.

[0035] 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.

[0036] Preferably, the calculation unit is arranged to generate the first and second sequences of modulating data from a first initial sequence of pseudo-random binary type and a second initial sequence of pseudo-random binary type.

[0037] In a preferred embodiment, the calculation unit is arranged to generate the first sequence as an exclusive or function of the first and second initial sequences and the second sequence as an exclusive or function of the first initial sequence with a circular shift and the second initial sequence of pseudo-random binary type. The first and second modulating sequences thus generated are so-called “Gold” sequences, the cross-correlation of which is minimal.

[0038] In a particular embodiment, the calculation unit synchronously transmits the first and second sequences of modulating data to the modulation unit of the first and second transmission modules for the respective transmission of the first and second light beams by the first and second transmission modules.

[0039] The expression "the calculation unit synchronously transmits the first and second sequences of modulating data to the modulation unit of the first and second transmission modules" means that the transmission of the data from the first and second transmission modules is carried out in such a way as to transmit information at a regular and coordinated rate and in particular that the pulses of the first and second light beams corresponding to the first data of these first and second modulating sequences are emitted by the first and second light modules at the same time.

[0040] Advantageously, the first and second emission modules are arranged so that the first and second light beams participate together, totally or partially, to the realization of a predetermined regulatory photometric function. It could for example 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 a low intensity.

[0041] Advantageously, the first emission module is arranged in a first front headlight of the motor vehicle and the second emission module is arranged in a second front headlight of the motor vehicle.

[0042] Preferably, the reception module and the first transmission module are arranged in the same front headlight of the vehicle.

[0043] In a particular embodiment, the at least one reception module is a first reception module comprising a first elementary acquisition module comprising at least one first photodetector capable of converting a light signal that it receives into an electrical signal and a first demodulation unit connected to the first photodetector and arranged to extract a data sequence, called demodulated, from an electrical signal converted by the first photodetector and in that it comprises a second reception module comprising a second elementary acquisition module comprising at least one second photodetector capable of converting a light signal that it receives into an electrical signal and a second demodulation unit connected to the second photodetector and arranged to extract a data sequence, called demodulated, from an electrical signal converted by the second photodetector.

[0044] Preferably, the computing unit is a common computing unit for the first and second receiving modules.

[0045] Alternatively, it may be provided that the first and second reception modules each comprise a calculation unit. Where appropriate, the calculation unit of each reception module may be arranged to estimate values ​​of a correlation function between the data sequence demodulated by the modulation unit of this reception module and the first, respectively the second, modulating data sequence and to determine a time of flight separating the emission of said first, respectively second, modulated light beam emitted from the reception of said received light beam from the values ​​of the correlation function.

[0046] Of course, the various features, variants and embodiments of the invention may be combined with each other in various combinations to the extent that they are not incompatible or mutually exclusive.

[0047] Furthermore, various other characteristics of the invention emerge from the appended description given with reference to the drawings which illustrate non-limiting forms of embodiment of the invention and where:

[0048] [Fig.l] represents, schematically and partially, a view of a system of a motor vehicle according to an exemplary embodiment of the invention.

[0049] [Fig.2] represents, schematically and partially, an example of operation of the system of [Fig.l] when implementing a telemetry method.

[0050] It should be noted that in these figures the structural and / or functional elements common to the different variants may have the same references.

[0051] Of course, various other modifications may be made to the invention within the scope of the appended claims.

[0052] With reference to [Fig.l] to [Fig.2], the present invention is a telemetry system 1 of a vehicle comprising a first transmission module 2a, a second transmission module 3a, a first reception module 3a; a second reception module 3b, and a calculation unit 4.

[0053] The first emission module 2a comprising a light module 21a capable of emitting a first light beam Fia, and a first modulation unit 22a capable of receiving a first data sequence Seqa and arranged to modulate the first light beam Fia emitted from said first modulating sequence Seqa.

[0054] The second emission module 2b comprising a light module 21b, distant from the light module 21a of the first emission module 2a, capable of emitting a second light beam Flb, a second modulation unit 22b capable of receiving a second data sequence Seqb and arranged to modulate the second light beam Flb emitted from the second modulating sequence Seqb.

[0055] The first emission module 2a is for example arranged in a right headlight of the motor vehicle and the second emission module 2b may be arranged in a left headlight of the motor vehicle.

[0056] Each of the light modules 21a and 21b is arranged so that the light beam Fia and Flb that it emits has an electromagnetic spectrum of which at least a portion is located in the visible spectrum. Preferably, the spectrum of these light beams Fia and Flb has an intensity peak, or line, in the blue at 450 nm. It will be noted that it is possible for the spectrum to have other intensity peaks, in the visible and / or in the infrared, or even for the peaks of the beams Fia and Flb to be distinct.

[0057] To the extent that the light beam formed by the combination of the beams Fia and Flb is composed, partially or totally, of white light, 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, each light module 21a and 21b may comprise an optical unit arranged to shape these light beams Fia and Flb so that the photometric distribution of each satisfies the requirements of said function. For example, it could be provided that the light beams Fia and Flb participate in the realization of a function of the daytime running light type, or DRL.

[0058] In addition to this photometric function, the light beams Fia and Flb allow the system 1 to perform functions of detecting and evaluating the position of an obstacle on the road and / or communicating with another vehicle or with a road infrastructure.

[0059] For these purposes, each modulation unit 22a and 22b is arranged to modulate the light beam Fia, Flb emitted by the light module 21a and 21b, from the sequence of modulating data Seqa, Seqb that it receives, for example by controlling the electrical power supplied to the light source of the light module.

[0060] It may thus be provided that each modulation unit 22a, 22b comprises a generator of a pulse width modulated control signal. This control signal makes it possible to control a switching power supply (not shown) of the light source of the light module 21a, 21b. Conventionally, the duty cycle of this control signal, set by the modulation unit 22a, 22b, thus makes it possible to control the average electrical power supplied to the light source, and therefore to control the light intensity of the light beam Fia, Flb, so as to satisfy the requirements of the photometric function that it performs.

[0061] In the example described, each modulation unit 22a, 22b is arranged to convert the data sequence Seqa, Seqb into a modulating signal and to modulate the initial control signal using this modulating signal. It will be noted that several types of modulation can be used indifferently within the framework of the present invention, and in particular an on-off keying modulation (OOK), a pulse code modulation (PCM), a pulse amplitude modulation (PAM), a pulse width modulation (PWM) or a pulse position modulation (PPM).

[0062] The light beams Fia, Flb thus emitted are composed of a train of light pulses succeeding one another with a sufficiently high frequency, for example greater than 30 MHz, in particular between 50 MHz and 100 MHz, so that the human eye can no longer distinguish them. Furthermore, the amplitude, the width and / or the position of each pulse with respect to the period allows the light beam Fia, Flb to transport the data sequence Seqa, Seqb, to the reception modules 3a, 3b.

[0063] The first reception module 3a comprises a first elementary acquisition module 321 comprising at least one first photodetector 321a capable of converting a light signal that it receives into an electrical signal Sel and a first unit of demodulation 33a connected to the first photodetector 321a and arranged to extract a data sequence, called demodulated Seq2, from an electrical signal Sel converted by the first photodetector 321a.

[0064] The second reception module 3b comprises a second elementary acquisition module 322 comprising at least one second photodetector 322a capable of converting a light signal that it receives into an electrical signal Sel and a second demodulation unit 33b connected to the second photodetector 322a and arranged to extract a data sequence, called demodulated Seq2, from an electrical signal Sel converted by the second photodetector 322a.

[0065] In the example described, the first reception module 3a is arranged in the right headlight of the motor vehicle, next to the first transmission module 2a, and the second reception module 3b is arranged in the left headlight of the motor vehicle, next to the second transmission module 2b.

[0066] The photodetectors 321a, 322a are identical and are each formed by an avalanche photodiode of a silicon photomultiplier. These photodiodes are distributed in a matrix manner. It will 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.

[0067] Each of the photodetectors can thus convert the portion of the light beam F2 that it receives into an electrical signal that it transmits to the demodulation unit 33a 33b, which can then extract a data sequence from it to transmit it to the calculation unit 4.

[0068] The calculation unit 4 is common to the transmission modules 2a, 2b and to the reception modules 3a, 3b.

[0069] In order to obtain an optimal signal-to-noise ratio in all weather conditions, and for all positions of an object to be detected, the calculation unit 4 is able to receive the demodulated data sequences Seq2 by the demodulation units 33a, 33b from an electrical signal Sel converted by the photodetectors 321a, 322a from the light beams received by the reception modules 3a, 3b. The calculation unit 4 is then arranged to estimate values ​​of a correlation function Fcorr between said demodulated data sequence Seq2 and said first and second modulating data sequences Seqa, Seqb and to determine a flight time r 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 Fcorr.

[0070] The calculation unit 4 can thus perform functions of detecting and evaluating the position of an object on the road, as will be described in connection with [Fig.2] which represents a telemetry method implemented by the lighting system 1.

[0071] In a first step E1, the calculation unit 4 periodically generates initial data sequences SeqO1, SeqO2. The initial sequences SeqO1, SeqO2 are, in the example described, binary type sequences, composed of “0” and “1”, pseudo random and of maximum size, also called M-sequence, having a duty cycle of 50%.

[0072] In a second step E2, the calculation unit generates the first and second sequences of modulating data Seqa, Seqb from the initial sequences SeqOl and Seq02.

[0073] More precisely, the calculation unit 4 is arranged to generate the first sequence Seqa by operating an exclusive or function on the first and second initial sequences SeqOl and Seq02 and to generate the second sequence Seqb by operating an exclusive or function on the first initial sequence SeqOl with a circular shift and the second initial sequence Seq02.

[0074] The first and second sequences of modulating data Seqa, Seqb are thus Gold sequences, the peak of the cross-correlation function Fcorr of which is lower than a given threshold value Vs.

[0075] The calculation unit 4 synchronously transmits the first and second sequences of modulating data Seqa, Seqb to the modulation units 22a, 22b of the first and second transmission modules 2a, 2b for the simultaneous transmission of the first and second light beams Fia, Flb by the first and second transmission modules 2a, 2b.

[0076] In a third step E3, the modulation units 22a, 22b modulate the light beams Fia, Flb emitted by the light modules 21a, 21b from this data sequence Seqa, Seqb. Thus, each modulation unit 22a, 22b respectively converts the data sequence Seqa, Seqb into a modulating signal and modulates the initial control signal using this modulating signal.

[0077] It will be noted that in the example described, each light pulse of the light beams Fia, Flb emitted by the light modules 21a, 21b corresponds to a bit of value “1” of the modulating sequences Seqa, Seqb. The average power of a portion of the first and second light beams Fia, Flb respectively containing the sequences Seqa, Seqb is thus defined by the number of bits of value “1” of these sequences Seqa, Seqb with respect to the total number of bits of these sequences, by the duration of the pulses and by the peak power of these pulses.

[0078] 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 modules 3a, 3b.

[0079] The light beam F2 received by the reception modules 3a, 3b is thus concentrated on one or more of the photodetectors 321a, 322a.

[0080] When the sunlight conditions in the vicinity of the vehicle are particularly high, sunlight is thus added to the light beam F2 received by the receiving modules 3a, 3b. The light beam F2 received by the receiving modules 3a, 3b 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.

[0081] In a fourth step E4, each of the photodetectors 321a, 322a converts the portion of the light beam F2 that it receives into an electrical signal Sel that it transmits to the demodulation units 33a, 33b, which can then extract from it a data sequence Seq2, called demodulated, in a fifth step E5.

[0082] The demodulation units 33a, 33b count, from the electrical signals Sel, the number of photons received by an elementary acquisition module 32 during a time interval corresponding to a pulse duration, then determine by thresholding with respect to a value determined from the peak power 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”.

[0083] The demodulated binary sequence Seq2 is thus transmitted to the calculation unit 4, which estimates, in a sixth step E6, values ​​of a correlation function Fcorr between one or other of the modulating sequences Seqa and Seqb, depending on whether the demodulated binary sequence Seq2 comes from one or other of the reception modules 3a, 3b, and the demodulated sequence Seq2.

[0084] 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 Seqa, Seqb delayed according to each of the time shift values.

[0085] Taking into account the autocorrelation and cross-correlation properties of Gold type 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 emission modules 2a, 2b and the instant when it is respectively received by the reception modules 3a, 3b, the modulating sequences Seqa, Seqb delayed by this value thus corresponding substantially to the demodulated sequence Seq2, apart from noise.

[0086] In a seventh step E7, the calculation unit 4 identifies this maximum value of the correlation function Fcorr and estimates the value r of this flight time of the light beam Fia, Flb between the object O and the vehicle, associated with this maximum value. In an eighth step E8, the calculation unit 4 estimates the distance d separating the object O from the vehicle.

[0087] 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, the signal-to-noise ratio remaining optimal regardless of the position of the object to be detected. These objectives are achieved in particular using two separate emission modules emitting modulated light beams with modulating sequences having satisfactory cross-correlation characteristics.

[0088] 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 modules 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. 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. Telemetry system (1) of a motor vehicle comprising: - A first emission module (2a) comprising a light module (21a) capable of emitting a first light beam (Fia), and a first modulation unit (22a) capable of receiving a first data sequence (Seqa) and arranged to modulate the first light beam (Fia) emitted from said first modulating sequence (Seqa); - A second transmission module (2b) comprising a light module (21b), distant from the light module (21a) of the first transmission module (2a), capable of emitting a second light beam (Flb), a second modulation unit (22b) capable of receiving a second data sequence (Seqb) and arranged to modulate the second light beam (Flb) emitted from the second modulating sequence (Seqb); - At least one reception module (3a, 3b) capable of receiving a light beam (F2), the reception module (3a, 3b) comprising at least one elementary acquisition module (321, 322) comprising at least one photodetector (321a, 322a) capable of converting a light signal that it receives into an electrical signal (Sel) and a demodulation unit (33a, 33b) connected to the photodetector (321a, 322a) and arranged to extract a data sequence, called demodulated (Seq2), from an electrical signal (Sel) converted by this photodetector (321a, 322a); - A computing unit (4) designed for: Generate first and second sequences of modulating data (Seqa, Seqb) of pseudo-random binary type and whose peak of the cross correlation function (Fcorr) is less than a given threshold value (Vs); and Transmit the first sequence of modulating data (Seqa) to the modulation unit (22a) of the first transmission module (2a) for the transmission of a first light beam modulated by the first transmission module (2a); • Transmitting the second modulating data sequence (Seqb) to the modulation unit (22b) of the second transmission module (2b) for the transmission of a second light beam modulated by the second transmission module (2b); Characterized in that the calculation unit (4) being able to receive a demodulated data sequence (Seq2) by the demodulation unit (33a, 33b) from an electrical signal (Sel) converted by the photodetector (321a, 322a) from a light beam received by the reception module (3a, 3b), the calculation unit (4) is arranged to estimate values ​​of a correlation function (Fcorr) between said demodulated data sequence (Seq2) and said first modulating data sequence (Seqa, Seqb) and to determine a time of flight (r) 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 (Fcorr);in that the first emission module (2a) is arranged in a first front headlight of the motor vehicle and in that the second emission module (2b) is arranged in a second front headlight of the motor vehicle and in that each of the first and second light modules is capable of emitting a first, respectively a second, light beam whose spectrum has a peak at a wavelength in the visible.;

2. Telemetry system (1) according to claim 1, characterized in that the calculation unit (4) is arranged to generate the first and second sequence of modulating data (Seqa, Seqb) from at least one same initial sequence of pseudo-random binary type (SeqOl, Seq02).

3. Telemetry system (1) according to claim 1, characterized in that the calculation unit (4) is arranged to generate the first and second sequence of modulating data (Seqa, Seqb) from a first initial sequence of pseudo-random binary type (SeqOl) and a second initial sequence of pseudo-random binary type (SeqO2).

4. Telemetry system (1) according to claim 1, characterized in that the calculation unit (4) is arranged to generate the first sequence (Seqa) as being a function or exclusive of the first and second initial sequences (SeqOl, Seq02) and the second sequence (Seqb) as an exclusive or function of the first initial sequence (SeqOl) with a circular shift and the second initial sequence (Seq02) of pseudo-random binary type.

5. Telemetry system (1) according to one of the preceding claims, characterized in that the computing unit (4) synchronously transmits the first and second modulating data sequences (Seqa, Seqb) to the modulation unit (22a, 22b) of the first and second transmission modules (2a, 2b) for the respective transmission of the first and second light beams (Fia, Flb) by the first and second transmission modules (2a, 2b).

6. Telemetry system (1) according to one of the preceding claims, characterized in that the at least one reception module (3a) is a first reception module (3a) comprising a first elementary acquisition module (321) comprising at least one first photodetector (321a) capable of converting a light signal that it receives into an electrical signal (Sel) and a first demodulation unit (33a) connected to the first photodetector (321a) and arranged to extract a data sequence, called demodulated (Seq2),from an electrical signal (Sel) converted by the first photodetector (321a) and in that it comprises a second reception module (3b) comprising a second elementary acquisition module (322) comprising at least one second photodetector (322a) capable of converting a light signal that it receives into an electrical signal (Sel) and a second demodulation unit (33b) connected to the second photodetector (322a) and arranged to extract a data sequence, called demodulated (Seq2), from an electrical signal (Sel) converted by the second photodetector (322a).,

7. Telemetry system (1) according to the preceding claim, characterized in that the computing unit (4) is a computing unit (4) common to the first (3a) and second (3b) receiving module.

8. Telemetry system (1) according to claim 7, characterized in that the first (3a) and second (3b) receiving module each comprise a computing unit (4).

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