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

Abstract

The invention relates to a telemetry system (1) for a motor vehicle, the system comprising: a first transmitting module capable of transmitting a first light beam (F1a) modulated by a first modulation sequence (Seqa); a second emission module (2b) capable of emitting a second light beam (F1b) modulated by a second modulation sequence (Seqb); a receiving module (3) capable of receiving the light beam (F2) and extracting a demodulation data sequence (Seq2) therefrom; a computing unit (4) arranged to generate a first pseudo-random binary modulated data sequence and a second pseudo-random binary modulated data sequence (Seqa, Seqb), the peak (P) of the cross-correlation function (Fcorr) of which is below a threshold value (Vs), and the computing unit is arranged to estimate a value of a correlation function (Fcorr) between the demodulated data sequence (Seq2) and the first modulated data sequence (Seqa).

Description

[0001] The present invention relates to the field of automotive lighting and / or light signaling, as well as the field of functions for detecting objects by a motor vehicle and estimating the distance between the object and the vehicle. More precisely, the present invention relates to a lighting and / or signaling system for a motor vehicle, which is able to perform a ranging function by means of the light it emits.

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

[0003] Conventionally, the light source used to emit this light beam is controlled by a pulse width modulated (PWM) electrical signal. This PWM signal thus periodically activates and deactivates the light source, so that the emitted light beam is composed of light pulses which occur successively at a sufficiently high frequency so that the human eye can no longer distinguish them. The intensity of the emitted light beam depends on the duty cycle of the PWM signal, allowing the intensity to be controlled by adjusting the duty cycle, and thus allowing the photometric function to be performed.

[0004] In addition to performing one or more photometric functions, such as a daytime running light or a low beam function, various functions can also be performed by a light module of this type. For example, the light source of the light module can be controlled so that the pulses of the emitted light beam convey a data sequence. The light system can thus be equipped with a reception module in order to receive the emitted light beam (after reflection from an object in the vicinity of the vehicle). The computing unit of the motor vehicle can then determine the time of flight of the emitted light beam and thus evaluate the distance between the vehicle and the object, after detecting the data sequence in the received light beam.

[0005] In this way, the light beam can retain its original function, i.e. to perform a photometric function, while allowing the light system to perform a ranging function, which can be particularly advantageous, for example, for advanced driver assistance functions or in the context of autonomous or semi-autonomous vehicles.

[0006] However, this type of system, based on the use of an emitting module capable of performing both a photometric light function and data transmission, has drawbacks. In particular, the reception module intended to receive the light beam conveying data, whether it is arranged in the same vehicle or in another vehicle, must include at least one photodetector for converting the light beam into an electrical signal in order to demodulate the signal and extract the data sequence therefrom.

[0007] However, under certain conditions, the signal-to-noise ratio of such a photodetector can be seriously degraded in view of the stray light sources present in the environment of the vehicle, such as urban lighting, car lighting on vehicles encountered or followed, or even sunlight, and the nature of the objects present in the environment, 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 from the target object, or even possibly lead to false positive detections.

[0008] In addition, under other conditions, when the light of the system is emitted by a plurality of light sources, there is a possibility of encountering delays due to the position offset of the object to be detected relative to the various emission modules, such delays possibly creating interference and potentially leading to false detections.

[0009] This is particularly true when each of the left and right headlamps of the motor vehicle is equipped with a light-emitting module allowing both the execution of the photometric function and the ranging function. When the object to be detected is located in a range of angles substantially offset from the axis relative to the motor vehicle, the time of flight of the light beam emitted by the right headlamp can be greater than the time of flight of the light beam emitted by the left headlamp, the deviation between these times of flight being greater than the pulse duration used to encode the data sequence employed for ranging. This deviation thus creates interference, reducing the signal-to-noise ratio of the light-emitting system.

[0010] There is therefore a need for a light-emitting motor vehicle system capable of executing both a given regulatory photometric function and a ranging function, which is efficient and has an optimal signal-to-noise ratio regardless of the position of the object to be detected.

[0011] The present invention falls within this context and aims to meet this need.

[0012] To this end, a ranging system for motor vehicles has been developed, comprising: a first transmitting module including a light-emitting module capable of emitting a first beam, and a first modulation unit capable of receiving a first data sequence and arranged to modulate the emitted first beam using the first modulation sequence; a second transmitting module including a light-emitting module located away from the first transmitting module and capable of emitting a second beam, and a second modulation unit capable of receiving a second data sequence and arranged to modulate the emitted second beam using the second modulation sequence; and at least one receiving module capable of receiving the beam, the receiving module including at least one basic acquisition module. The system includes at least one photodetector capable of converting received optical signals into electrical signals, and a demodulation unit connected to the photodetector and arranged to extract a data sequence, referred to as a demodulated data sequence, from the electrical signals converted by the photodetector; a computing unit arranged to generate a first modulated data sequence and a second modulated data sequence of pseudo-random binary type, the peak value of the cross-correlation function of the first modulated data sequence and the second modulated data sequence being less than a given threshold; a modulation unit that transmits the first modulated data sequence to a first transmitting module for the purpose of transmitting a first modulated beam by the first transmitting module; and a modulation unit that transmits the second modulated data sequence to a second transmitting module for the purpose of transmitting a second modulated beam by the second transmitting module.

[0013] According to the present invention, the computing unit is capable of receiving a data sequence demodulated from an electrical signal by a demodulation unit, the electrical signal being converted by a photodetector based on a beam received by a receiving module. The computing unit is arranged to estimate the value of a correlation function between the demodulated data sequence and the first modulated data sequence, and to determine the time of flight between the emission of the emitted first modulated beam and the reception of the received beam based on the value of the correlation function.

[0014] Therefore, this invention proposes to split the light beam emitted by the ranging system of a motor vehicle into two beams, each emitted by a given light-emitting module. Thus, the first and second beams are emitted simultaneously and together perform all or part of the photometric measurement function.

[0015] Each of the first and second beams can be, for example, a pulse beam, each pulse corresponding to one or more consecutive high values ​​of the first and second data sequences, and the interval between two consecutive pulses corresponding to one or more consecutive low values ​​of the data sequences. Each pulse of the first and second modulated beams is emitted at a peak luminous power, such that the average luminous power of the emitted first modulated beam is thus defined by the peak luminous power and the duty cycle of the first modulated data sequence.

[0016] Therefore, the beam received by the receiving module includes reflections from the first beam and the second beam from the object to be detected. Thus, the data sequence demodulated by the demodulation unit consists of a first modulation sequence, a second modulation sequence, and noise, each modulation sequence being delayed by a different delay. Each value of the correlation function estimated by the computing unit is associated with a time shift of the first modulation sequence or the demodulated sequence used to estimate that value of the correlation function. Therefore, the correlation function between the demodulated data sequence and one of the modulation sequences depends on the autocorrelation of the modulation sequence and the cross-correlation of the first and second modulation sequences.

[0017] Therefore, it should be understood that when the peak value of the cross-correlation function of the modulated data sequence is less than a given threshold or even substantially zero, the correlation function depends only on the autocorrelation of the first modulated sequence. Thus, the presence of the first data sequence in the received beam can be detected after reflection from an object in the vehicle environment, and the presence of this object can be detected and the distance of the object from the vehicle estimated. In this way, interference that may be caused by lateral displacement of the object to be detected relative to the motor vehicle is significantly reduced or even eliminated.

[0018] In one embodiment of the invention, each of the first and second light-emitting modules is capable of emitting a first or second light beam whose spectrum has a peak at a wavelength in the visible light domain, particularly between 400 nm and 500 nm. Advantageously, each of the first and second light-emitting modules includes a light source comprising a semiconductor generator capable of emitting a fundamental light beam (particularly a beam whose spectrum has a peak at a wavelength in the visible light domain) and a photoluminescent element capable of converting the fundamental light beam to obtain the light beam.

[0019] The semiconductor can be, for example, gallium nitride (GaN), which is capable of electroluminescence and emits blue light in response to an electric current passing through it. The photoluminescent element can be, for example, in the form of a resin comprising cerium-doped yttrium aluminum garnet (CE:YAG), capable of absorbing blue light and emitting yellow light in response to excitation by that light. The photoluminescent element is arranged on the generator such that some of the blue light excites the element, causing it to emit yellow light through photoluminescence. The remaining blue light passes through the element. Therefore, when powered, the light source emits both blue and yellow light simultaneously, resulting in light that appears white to the human eye.

[0020] The light source can therefore be a laser source, a light-emitting diode (LED), a vertical-cavity surface-emitting laser (VCSEL), or a superluminescent diode (SLED). Preferably, the light source is an LED that emits incoherent light. In this way, eye safety issues that complicate and increase the cost of the system are avoided.

[0021] Advantageously, each of the first and second light-emitting modules may include an optical unit arranged to project light emitted by the light source to form the first beam or the second beam, respectively.

[0022] Advantageously, the first modulation unit and the second modulation unit are arranged to generate a pulse width modulation control signal, modulate the control signal using a first modulation data sequence and a second modulation data sequence, and respectively use the modulation control signal to control the emission of the first light-emitting module and the second light-emitting module from the first light beam and the second light beam. For example, the first modulation unit and the second modulation unit may be arranged to convert the first modulation data sequence and the second modulation data sequence into a modulation signal, and respectively modulate the amplitude, frequency, or phase of, for example, the control signal using the modulation signal.

[0023] Where appropriate, the first modulation unit and the second modulation unit can be arranged to control the light source of the first light-emitting module and the second light-emitting module, and in particular the power supply supplied to the light source, so as to modulate the first beam and the second beam respectively.

[0024] Advantageously, the receiving module comprises multiple basic acquisition modules arranged in a matrix array, each basic acquisition module including a photodetector capable of converting its received optical signal into an electrical signal. For example, all photodetectors can be combined to form a sensor, such as a single electronic component. Also, for example, each photodetector can have a width and / or length of less than about ten micrometers, which allows for a basic acquisition module with a receiving field of at most 0.1°, and thus improves the spatial resolution of the receiving module.

[0025] Advantageously, the photodetector of the basic acquisition module or each basic acquisition module is an avalanche photodiode. This type of photodetector is also known as a single-photon avalanche diode (SPAD). Avalanche photodiodes can therefore be used together to form a silicon photomultiplier (SiPM). This type of photodetector is capable of detecting the incidence of a single photon with a high gain (e.g., a gain on the order of 10⁶), and thus compensates for the degradation of the signal-to-noise ratio due to external conditions.

[0026] According to one example of an embodiment of the present invention, the receiving module may include an optical unit arranged in front of the basic acquisition module.

[0027] In one particular embodiment, the computing units are arranged to generate a first modulated data sequence and a second modulated data sequence from at least one and the same initial sequence of pseudo-random binary type.

[0028] Pseudo-random binary sequences (PRBS) are data sequences consisting of high values ​​(i.e., "1") and low values ​​(i.e., "0"). This type of sequence has particularly advantageous properties. Specifically, its autocorrelation function is at its maximum for a time shift of zero (i.e., when the sequence is compared to itself), and for any other time shift (i.e., when the sequence is compared to a time-shifted version of itself), the value of the autocorrelation function is significantly lower than this maximum value.

[0029] Furthermore, the cross-correlation function between two pseudo-random binary sequences is significantly smaller than the maximum value of the autocorrelation function of these sequences. Finally, this type of sequence is typically generated using a linear feedback shift register (LFSR), which produces periodic recursive sequences in the pattern of pseudo-random binary sequences.

[0030] Given the autocorrelation properties of the pseudo-random binary sequence, the correlation function thus estimated will be maximized for the time shift corresponding to the flight time of the modulated beam, including the emission, reflection, and subsequent reception, even when noise is high.

[0031] Therefore, the computing unit can accurately identify the time shift associated with the maximum value of the correlation function and deduce the distance between the object reflecting the beam and the motor vehicle.

[0032] Furthermore, given the cross-correlation properties, it seems unlikely that receiving a modulated beam emitted by an equivalent system of another vehicle would lead to a false alarm.

[0033] Finally, it should be understood that the detection is performed not on a single pulse but on the entire data sequence, which improves the signal-to-noise ratio of the system.

[0034] In one embodiment of the invention, the computing unit is arranged to estimate each value of the correlation function between the demodulated data sequence and the first modulated data sequence by evaluating the cross-correlation between the demodulated data sequence and the first modulated data sequence delayed by a given time associated with the value.

[0035] In other words, each value of the correlation function is therefore associated with a time shift of the first modulation sequence used to estimate that value of the correlation function. Thus, the computational unit is designed to identify the time shift associated with the maximum value of the cross-correlation function.

[0036] Preferably, the computing unit is arranged to generate a first modulated data sequence and a second modulated data sequence 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 computing unit is arranged to generate a first sequence as an XOR function of a first initial sequence and a second initial sequence, and to generate a second sequence as an XOR function of a cyclically shifted first initial sequence and a pseudo-random binary type second initial sequence. The first and second modulation sequences thus generated are so-called Gold sequences, which have minimal cross-correlation.

[0038] In one particular embodiment, the computing unit synchronously transmits the first modulation data sequence and the second modulation data sequence to the modulation units of the first and second transmitting modules, so that the first and second transmitting modules can respectively transmit the first beam and the second beam.

[0039] The statement "the computing unit synchronously transmits the first modulation data sequence and the second modulation data sequence to the modulation unit of the first and second transmitting modules" means that the data transmission of the first and second transmitting modules is performed in a regular and coordinated manner, and in particular, the pulses of the first beam and the second beam corresponding to the first data of these first modulation sequences and the second modulation sequences are emitted simultaneously by the first light-emitting module and the second light-emitting module.

[0040] Advantageously, the first and second emission modules are designed such that the first and second beams together fully or partially contribute to performing a predetermined regulatory photometric function. For example, this could be a problem with daytime running lights (DRLs), which have the advantage of emitting at low intensity over a wide field.

[0041] Advantageously, the first transmitting module is arranged in the first headlight of the motor vehicle, and the second transmitting module is arranged in the second headlight of the motor vehicle, the first headlight being different from the second headlight. Preferably, the first and second headlights can be located on opposite sides of a certain side of the vehicle, preferably on opposite sides of the front of the vehicle.

[0042] Preferably, the receiving module and the first transmitting module are arranged in the same headlight of the vehicle.

[0043] In one particular embodiment, at least one receiving module is a first receiving module, which includes a first basic acquisition module, which includes at least one first photodetector capable of converting received optical signals into electrical signals, and a first demodulation unit connected to the first photodetector and arranged to extract a data sequence, referred to as a demodulated data sequence, from the electrical signals converted by the first photodetector. The at least one receiving module also includes a second receiving module, which includes a second basic acquisition module, which includes at least one second photodetector capable of converting received optical signals into electrical signals, and a second demodulation unit connected to the second photodetector and arranged to extract a data sequence, referred to as a demodulated data sequence, from the electrical signals converted by the second photodetector.

[0044] Preferably, the computing unit is a computing unit shared by the first receiving module and the second receiving module.

[0045] As a variant, it can be proposed that the first receiving module and the second receiving module each include a computing unit. Where appropriate, the computing unit of each receiving module can be arranged to estimate the value of a correlation function between the data sequence demodulated by the modulation unit of that receiving module and the first modulated data sequence and the second modulated data sequence, and to determine the time of flight between the emission of the first modulated beam and the emission of the second modulated beam and the reception of the received beam based on the value of the correlation function.

[0046] Of course, the various features, variations and embodiments of the present invention can be combined with each other in various combinations, as long as they are compatible with each other or not mutually exclusive.

[0047] Furthermore, various other features of the invention will become apparent from the accompanying description given with reference to the accompanying drawings, which illustrate non-limiting embodiments of the invention, in which: [ Figure 1 The diagram schematically and partially illustrates a view of an example of a motor vehicle system according to an embodiment of the invention.

[0048] [ Figure 2 [Illustratively and partially showing] Figure 1 An example of how the system operates during the implementation of the ranging method.

[0049] It should be noted that in these figures, structural and / or functional elements common to various alternative embodiments may have the same reference numerals.

[0050] Of course, various other modifications can be made to the invention within the scope of the appended claims.

[0051] refer to[Figure 1 ]and[ Figure 2 The present invention relates to a ranging system 1 for a vehicle, the ranging system comprising a first transmitting module 2a, a second transmitting module 2b, a first receiving module 3a, a second receiving module 3b, and a computing unit 4.

[0052] The first transmitting module 2a includes a light-emitting module 21a capable of emitting a first light beam F1a, and a first modulation unit 22a capable of receiving a first data sequence Seqa and arranged to use the first modulation sequence Seqa to modulate the emitted first light beam F1a.

[0053] The second transmitting module 2b includes a light-emitting module 21a located away from the first transmitting module 2a and capable of emitting a second beam F1b, and a second modulation unit 22b capable of receiving a second data sequence Seqb and arranged to use the second modulation sequence Seqb to modulate the emitted second beam F1b.

[0054] The first launching module 2a is arranged, for example, in the right headlight of the motor vehicle, and the second launching module 2b can be arranged in the left headlight of the motor vehicle.

[0055] Each of the light-emitting modules 21a and 21b is designed such that the emitted light beams F1a and F1b have electromagnetic spectra, at least a portion of which are located in the visible spectrum. Preferably, the spectra of light beams F1a and F1b have intensity peaks or spectral lines in the blue light at 450 nm. It should be noted that the spectra may have other intensity peaks in the visible light and / or infrared, or even the peaks of light beams F1a and F1b may be separate.

[0056] When the light beam formed by combining beams F1a and F1b is partially or entirely composed of white light, this beam can be used to partially or entirely assist in performing a predetermined, particularly regulatory, photometric measurement function. In this case, each light-emitting module 21a and 21b may include an optical unit arranged to shape beams F1a and F1b such that the photometric distribution of each beam meets the requirements of the function. For example, beams F1a and F1b may be proposed to assist in performing a daytime running light (DRL) function.

[0057] In addition to this photometric function, beams F1a and F1b allow system 1 to perform functions that enable the detection and assessment of the location of obstacles on the road and / or communication with other vehicles or road infrastructure.

[0058] For this purpose, each modulation unit 22a and 22b is arranged to modulate the light beams F1a and F1b emitted by the light-emitting modules 21a and 21b using the modulation data sequences Seqa and Seqb received therefrom, for example by controlling the electrical power of the light source supplied to the light-emitting modules.

[0059] Therefore, it can be proposed that each modulation unit 22a, 22b includes a generator of a PWM control signal (PWM stands for Pulse Width Modulation). The control signal enables control of the switching mode power supply (not shown) of the light source of the light-emitting modules 21a, 21b. Conventionally, the duty cycle of the control signal set by the modulation units 22a, 22b thus allows control of the average electrical power supplied to the light source, and thus allows control of the luminous intensity of the beams F1a, F1b to meet the requirements of the photometric function performed by the beams.

[0060] In the described example, each modulation unit 22a, 22b is arranged to convert the data sequence Seqa, Seqb into a modulation signal, and use the modulation signal to modulate the initial control signal. It should be noted that any of a variety of modulation types can be employed within the scope of this invention, particularly on-off keying (OOK), pulse code modulation (PCM), pulse amplitude modulation (PAM), pulse width modulation (PWM), or even pulse position modulation (PPM).

[0061] Therefore, the emitted light beams F1a and F1b consist of a series of continuous light pulses, which follow one another at a sufficiently high rate (e.g., above 30 MHz, particularly 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 relative to the period allow the light beams F1a and F1b to transmit the data sequence Seqa and Seqb to the receiving modules 3a and 3b.

[0062] The first receiving module 3a includes a first basic acquisition module 321, which includes at least one first photodetector 321a, which is capable of converting the received optical signal 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 data sequence Seq2 from the electrical signal Sel converted by the first photodetector 321a.

[0063] The second receiving module 3b includes a second basic acquisition module 322, which includes at least one second photodetector 322a, which is capable of converting the received optical signal 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 data sequence Seq2 from the electrical signal Sel converted by the second photodetector 322a.

[0064] In the described example, the first receiving module 3a is arranged in the right headlight of the motor vehicle, next to the first transmitting module 2a, and the second receiving module 3b is arranged in the left headlight of the motor vehicle, next to the second transmitting module 2b.

[0065] Photodetectors 321a and 322a are identical, and each is formed from an avalanche photodiode of a silicon photomultiplier. These photodiodes are arranged in an array. It should be noted that the size of the photodetectors is on the order of one micrometer. Therefore, this assembly forms a sensor with a receiving spatial resolution on the order of 1° or even 0.1°, and its detection capability is particularly high even under degraded acquisition conditions due to the use of avalanche photodiodes.

[0066] Therefore, each of the photodetectors can convert a portion of the received beam F2 into an electrical signal that is transmitted to the demodulation units 33a and 33b, from which the demodulation unit can extract a data sequence for transmission to the computing unit 4.

[0067] The computing unit 4 is shared by the transmitting modules 2a and 2b and the receiving modules 3a and 3b.

[0068] To achieve the optimal signal-to-noise ratio under all weather conditions and regardless of the location of the object being detected, the computing unit 4 is capable of receiving the data sequence Seq2, demodulated from the electrical signal Sel by the demodulation units 33a and 33b. This electrical signal is converted by photodetectors 321a and 322a based on the beam received by the receiving modules 3a and 3b. The computing unit 4 is then configured to estimate the value of the correlation function Fcorr between the demodulated data sequence Seq2 and the first modulated data sequence Seqa and the second modulated data sequence Seqb, and to determine the time of flight τ between the emission of the first modulated beam and the reception of the received beam based on the value of the correlation function Fcorr.

[0069] Therefore, computing unit 4 is capable of performing functions that allow for the detection and evaluation of the position of objects on the road, such as referencing [ Figure 2 As described, the figure illustrates a ranging method implemented by the luminous system 1.

[0070] In the first step E1, computing unit 4 periodically generates the initial data sequences Seq01 and Seq02. In the described example, the initial sequences Seq01 and Seq02 are the largest pseudo-random binary sequences (composed of "0" and "1"), i.e., the so-called M-sequences, with a duty cycle of 50%.

[0071] In the second step E2, the computing unit generates a first modulation data sequence Seqa and a second modulation data sequence Seqb based on the initial sequences Seq01 and Seq02.

[0072] More precisely, the computation unit 4 is arranged to generate a first sequence Seqa by applying an XOR function to a first initial sequence Seq01 and a second initial sequence Seq02, and to generate a second sequence Seqb by applying an XOR function to the first initial sequence Seq01 after cyclic shift and to the second initial sequence Seq02.

[0073] Therefore, the first modulated data sequence Seqa and the second modulated data sequence Seqb are Gold sequences, and the peak value P of the cross-correlation function Fcorr of the Gold sequence is less than a given threshold Vs.

[0074] The computing unit 4 synchronously transmits the first modulation data sequence Seqa and the second modulation data sequence Seqb to the modulation units 22a and 22b of the first transmission module 2a and the second transmission module 2b, so that the first transmission module 2a and the second transmission module 2b can simultaneously transmit the first beam F1a and the second beam F1b.

[0075] In the third step E3, modulation units 22a and 22b modulate the light beams F1a and F1b emitted by light-emitting modules 21a and 21b based on the data sequences Seqa and Seqb. Therefore, each modulation unit 22a and 22b converts the corresponding data sequences Seqa and Seqb into a modulation signal and uses the modulation signal to modulate the initial control signal.

[0076] It should be noted that in the described example, each optical pulse of the light beams F1a and F1b emitted by the light-emitting modules 21a and 21b corresponds to a bit with a value of "1" in the modulation sequence Seqa and Seqb. Therefore, the average power of the first beam F1a and the second beam F1b, which includes a portion of the corresponding sequences Seqa and Seqb, is defined by the number of bits with a value of "1" in the sequences Seqa and Seqb relative to the total number of bits in the sequence, the duration of the pulse, and the peak power of the pulse.

[0077] Therefore, the beam consisting of the first beam F1a and the second beam F1b is emitted and propagates until it reaches the object O located in the vehicle environment, which reflects the beam in the direction of the receiving modules 3a and 3b.

[0078] Therefore, the beam F2 received by receiving modules 3a and 3b is focused on one or more of photodetectors 321a and 322a.

[0079] When sunlight conditions near the vehicle are particularly bright, sunlight is added to the beam F2 received by receiving modules 3a and 3b. Therefore, the beam F2 received by receiving modules 3a and 3b consists of the portion of the overall beam F1a and F1b reflected by object O and noise, which may be generated by stray light sources such as city lighting, car lighting, or even the sun.

[0080] In the fourth step E4, each of the photodetectors 321a and 322a converts a portion of the received beam F2 into an electrical signal Sel that is transmitted to the demodulation units 33a and 33b, from which the demodulation units can then extract a data sequence Seq2, known as the demodulated data sequence, in the fifth step E5.

[0081] Demodulation units 33a and 33b count the number of photons received by the basic acquisition module 32 during the time interval corresponding to the pulse duration from the electrical signal Sel, and then determine whether the number of photons corresponds to the pulse of the first beam F1a by thresholding and comparing it with a value determined according to the peak power, and therefore whether it corresponds to a bit with a value of "1" or a bit with a value of "0".

[0082] Therefore, the demodulated binary sequence Seq2 is transmitted to the computing unit 4, which estimates the value of the correlation function Fcorr between one of the modulation sequences Seqa and Seqb (which modulation sequence depends on which receiving module 3a, 3b provides the demodulated binary sequence Seq2) and the demodulated sequence Seq2 in the sixth step E6.

[0083] Therefore, computation unit 4 evaluates the cross-correlation value between the demodulated sequence Seq2 and the modulation sequences Seqa and Seqb delayed by each of these time shifts by means of circular convolution multiplication for multiple time shifts.

[0084] Given the autocorrelation and cross-correlation properties of the Gold sequence, the correlation function Fcorr will be maximized for the time shift corresponding to the time of flight between the time when beams F1a and F1b are emitted by the transmitting modules 2a and 2b and the time when they are received by the corresponding receiving modules 3a and 3b. The modulation sequences Seqa and Seqb delay this shift and therefore essentially correspond to the demodulation sequence Seq2, excluding noise.

[0085] In step E7, the calculation unit 4 identifies the maximum value of the correlation function Fcorr and estimates the flight time τ of the beams F1a and F1b between object O and the vehicle, the flight time being associated with the maximum value. In step E8, the calculation unit 4 estimates the distance d between object O and the vehicle.

[0086] The above description clearly explains how the present invention achieves its targeted objective of providing a luminous motor vehicle system capable of simultaneously performing a given regulatory photometric measurement function and a ranging function, maintaining an optimal signal-to-noise ratio regardless of the position of the object being detected. These objectives are achieved specifically using two separate emitting modules, the modulated beams emitted by these two separate emitting modules having modulation sequences with satisfactory cross-correlation characteristics.

[0087] In any event, the invention is not limited to the embodiments specifically described herein, but extends particularly to all equivalent devices and any technically operable combinations thereof. In particular, it may be proposed that the transmitting module have other configurations, specifically employing light source types other than those described, such as laser diodes, VCSELs, SLEDs, or RGB diodes. It may also be proposed to perform photometric functions other than those described, and particularly low beam illumination functions, or position light or turn signaling functions. Wavelength ranges other than those described are also conceivable.

Claims

1. A ranging system (1) for motor vehicles, comprising: - a first emission module (2a) comprising a light emission module (21a) capable of emitting a first light beam (Fla) and a first modulation unit (22a) capable of receiving a first data sequence (Seqa) and arranged to modulate the emitted first light beam (Fla) using the first modulation sequence (Seqa); - a second emission module (2b) comprising a light emission module (21b) capable of emitting a second light beam (Flb) remote from the light emission module (21a) of the first emission module (2a) and a second modulation unit (22b) capable of receiving a second data sequence (Seqb) and arranged to modulate the emitted second light beam (Flb) using the second modulation sequence (Seqb); - at least one reception module (3) capable of receiving a light beam (F2), said reception module (3) comprising at least one elementary acquisition module (32) comprising at least one photodetector (32a) capable of converting the optical signal it receives into an electrical signal (Sel) and a demodulation unit (33) connected to the photodetector (32a) and arranged to extract from the electrical signal (Sel) converted by the photodetector (32a) a data sequence referred to as a demodulated data sequence (Seq2); - a calculation unit (4) arranged to: • generate first and second modulation data sequences (Seqa, Seqb) of a pseudo-random binary type and whose cross-correlation function (Fcorr) has a peak (P) less than a given threshold (Vs); • transmit the first modulation data sequence (Seqa) to the modulation unit (22a) of the first emission module (2a) with a view to the emission of a first modulated light beam by the first emission module (2a); and • transmit the second modulation data sequence (Seqb) to the modulation unit (22b) of the second emission module (2b) with a view to the emission of a second modulated light beam by the second emission module (2b); characterized in that the calculation unit (4) is capable of receiving the data sequence (Seq2) demodulated by the demodulation unit (33) from the electrical signal (Sel) converted by the photodetector (32a) on the basis of the light beam received by the reception module (3), the calculation unit (4) being arranged to estimate the value of the correlation function (Fcorr) between the demodulated data sequence (Seq2) and the first modulation data sequence (Seqa) and to determine the time of flight (T) between the emission of the emitted first modulated light beam and the reception of the received light beam on the basis of the value of the correlation function (Fcorr). ​ 2. The distance measuring system (1) as claimed in claim 1, characterized in that The calculation unit (4) is arranged to generate the first and second modulated data sequences (Seqa, Seqb) from at least one and the same initial sequence of pseudo-random binary type.

3. The distance measuring system (1) as claimed in claim 1, characterized in that The calculation unit (4) is arranged to generate the first and second modulated data sequences (Seqa, Seqb) from a first initial sequence of pseudo-random binary type and a second initial sequence of pseudo-random binary type.

4. The ranging system (1) as claimed in claim 1, characterized in that The calculation unit (4) is arranged to generate a first sequence (Seq1) as an exclusive-or function of the first initial sequence and the second initial sequence (Seqa, Seqb), and to generate the second sequence (Seq2) as an exclusive-or function of the first initial sequence (Seqa) cyclically shifted and the second initial sequence (Seqb) of pseudo-random binary type.

5. The ranging system (1) according to any one of the preceding claims, characterized in that, The calculation unit (4) transmits the first and second modulated data sequences (Seqa, Seqb) in synchronism to the modulation units (22a, 22b) of the first and second emission modules (2a, 2b) for the emission of the first and second light beams (F1a, F1b) by the first and second emission modules (2a, 2b), respectively.

6. The ranging system (1) according to any one of the preceding claims, characterized in that, The first emission module (2a) is arranged in a first headlamp of the motor vehicle, and wherein the second emission module (2b) is arranged in a second headlamp of the motor vehicle, the first headlamp being different from the second headlamp.

7. The ranging system (1) as claimed in claim 5, characterized in that The reception module (3) and the first emission module (2a) are arranged in the same headlamp of the vehicle.

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

9. Ranging system (1) according to the preceding claim, characterized in that The calculation unit (4) is a calculation unit (4) common to the first and second reception modules (3a, 3b).

10. The ranging system (1) as claimed in claim 8, characterized in that The first and second receiving modules (3a, 3b) each comprise a computing unit (4a, 4b).

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