Range-finding system for a motor vehicle, comprising a module for emitting a light beam and a safety module

Abstract

The invention relates to a range-finding system for a motor vehicle, comprising an emission module (2) comprising a luminous module (21) comprising a plurality of series-connected light sources (21a) and a modulation unit (22); a computing unit (4) for generating and transmitting a modulating data sequence (Seq_m) to the modulation unit (22) for the emission of a modulated light beam (F1); characterized in that it comprises a safety module (23) able to detect failure of each of the light sources; in that the safety module comprises switching means (23a) each associated with one of the light sources, the safety module being designed, in response to the detection of failure of a light source, to control the switching means so as to short-circuit the failed light source and allow the other light sources to emit the light beam.

Description

[0001] Description

[0002] Title of the invention: Telemetry system for a motor vehicle comprising a module for emitting a light beam and a safety module

[0003] [1] 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.

[0004] [2] 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.

[0005] [3] 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.

[0006] [4] 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.

[0007] [5] 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.

[0008] [6] However, this type of system based on the emission and reception of a light beam capable of performing both a photometric light function and a telemetry function has drawbacks.

[0009] [7] In order to be able to perform a telemetry function with good detection resolution, it is necessary for the light module to have small light sources, in order to increase their cut-off frequency and thus to be able to modulate the light beam emitted by the light module at high frequency so that the bandwidth and therefore the spatial resolution of the telemetry function comply with the safety requirements of the automotive sector.

[0010] [8] This reduction in the size of the light sources is then accompanied by a reduction in the light power that each light source can emit. Thus, to be able to combine this telemetry function with a photometric light function, it is then necessary to increase the number of light sources in the light module, so as to maintain a light power compatible with the regulatory requirements governing photometric light functions. In order to optimize the energy efficiency of the system, the light sources of the light module are then connected in series, in order to reduce the quantity of electric current directed to ground.

[0011] [9] This electronic architecture then has a major drawback. Indeed, if one of the light sources fails, all the light sources connected in series also fail and the telemetry and photometry functions are no longer ensured. However, these functions, and in particular the telemetry function, are functions with a high level of automotive safety integrity or ASIL (from the English “Automotive Safety Integrity Level”), at least level C.

[0012]

[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, with high bandwidth and light power and optimal energy efficiency, and for which these functions remain assured even in the event of failure of a light source of the system.

[0013]

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

[0014]

[0012] For these purposes, the invention relates to a telemetry system for a motor vehicle comprising: a. a transmission module comprising a light module comprising at least a plurality of light sources connected in series and capable of emitting a light beam whose spectrum has at least one portion in the visible spectrum and a modulation unit capable of receiving a data sequence, called modulating, and arranged to modulate said light beam emitted by said plurality of light sources from the received data sequence; b. a calculation unit arranged to generate a modulating data sequence and to transmit said modulating data sequence to the modulation unit for retransmission of a light beam modulated by the transmission module;

[0015]

[0013] The telemetry system according to the invention is characterized in that it comprises a safety module capable of detecting a failure of each of the light sources of said plurality of light sources; and in that the safety module comprises a plurality of switching means each associated with one of the light sources, the safety module being arranged to, in response to the detection of a failure of a light source, control the switching means to short-circuit said faulty light source and authorize the emission of the light beam by the other light sources of said plurality of light sources.

[0016]

[0014] The invention thus proposes to modulate a light beam emitted by a plurality of light sources connected in series one after the other, using a modulating sequence. Each pulse of the modulated light beam will be emitted with a peak light power, so that the average light power of the modulated light beam emitted, necessary for carrying out the photometric function, is thus defined by the sum of the peak light powers of the light sources and the duty cycle of the modulating data sequence. The emitted light beam can thus be modulated at a frequency high enough to have sufficient light power to carry out a photometric light function while simultaneously carrying out a telemetry function.

[0017]

[0015] Furthermore, in the event of a light source failing, the safety module is capable of identifying the source of failure and controlling the switching means to allow the passage of the electrical power signal carrying the modulating data sequence only through the other light sources. The functions are thus maintained by the system, in a slightly degraded mode, which is compatible with the safety requirements governing these functions.

[0018]

[0016] It may be provided that the plurality of light sources is formed by blocks of elementary light sources mounted in series one after the other, each block forming one of the light sources. It may also be provided that the system according to the invention comprises other pluralities of light sources, mounted in parallel with each other, each being in this case equipped with its own security module.

[0019]

[0017] Advantageously, the light sources of said plurality of light sources are arranged so as to have an emission direction identical to each other. In other words, the light sources are arranged to emit the same beam carrying the same modulating data sequence.

[0020]

[0018] In one embodiment of the invention, the light module is capable of emitting a light beam whose spectrum has a peak at a wavelength in the visible, in particular between 400 nm and 500 nm. Advantageously, each light source of said plurality of light sources comprises 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 a light sub-beam, all of the sub-beams forming said light beam.

[0021]

[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 aluminum garnet, or CE:YAG, capable of absorbing blue light and, by photoluminescence and in response to the excitation produced by this light, of emitting rays of yellow light. The photoluminescent element is arranged on the generator so that a portion of the blue light rays excites this element so that it emits, by photoluminescence, rays of yellow light. The other portion of the blue light rays passes through this element. Thus, the light source emits simultaneously, when it is electrically powered, rays of blue and yellow light, the light thus formed appearing white to the human eye.

[0022]

[0020] Each 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”).

[0023]

[0021] In an exemplary embodiment of the invention, each light source of said plurality of light sources comprises a light-emitting diode of a size less than 500 micrometers, in particular of a size of substantially 300 micrometers. According to this characteristic, the capacitive component intrinsic to the diode is reduced, this component being proportional to the volume and therefore to the surface area of ​​the diode. The cut-off frequency of a diode being inversely proportional to this component, this type of diode has a cut-off frequency which is at least ten times the cut-off frequency of the diodes conventionally used in vehicles, this latter cut-off frequency being 5 MHz. Furthermore, these smaller diodes being crossed by a smaller current, the invention makes it possible to reduce the losses by Joule effect and to use smaller and therefore less expensive copper tracks.

[0024]

[0022] Advantageously, the light module may comprise an optical unit arranged to project the light rays emitted by the light sources of said plurality of light sources to form said light beam.

[0025]

[0023] In one embodiment of the invention, the modulation unit is arranged to modulate said light beam emitted by said plurality of light sources from the sequence of data received at a frequency greater than 5 MHz. It may in particular be provided that the modulation frequency is between 5 MHz and 200 MHz, and in particular between 30 and 150 MHz.

[0026]

[0024] Advantageously, the light sub-beam emitted by each light source may for example be a pulsed beam, each pulse corresponding to one or more consecutive high values ​​of the modulating data sequence and the interval separating two consecutive pulses corresponding to one or more consecutive low values ​​of this modulating data sequence. Each pulse of the modulated light sub-beam emitted by each light source is emitted with a peak light power, so that the average light power of the modulated light beam emitted by the light module is thus defined by the sum of the peak light powers of the light sources and the duty cycle of the modulating data sequence.

[0027]

[0025] Advantageously, the modulation unit is arranged to generate a pulse width modulated control signal, to modulate said control signal from the modulating data sequence and to control the emission of said light beam by the light module from the modulated control signal. For example, the modulation unit may be arranged to convert the modulating data sequence into a modulating signal and to modulate, for example in amplitude, frequency or phase, the control signal with this modulating signal.

[0028]

[0026] In one embodiment of the invention, the modulation unit is arranged to control, from the modulating data sequence, a power supply supplied to said plurality of light sources to modulate the light beam emitted by said plurality of light sources. Where appropriate, the modulation unit is connected to both an input terminal and an output terminal of said plurality of light sources and the modulation unit is arranged to alternate between a "push" configuration in which the power supply is controlled to flow from said input terminal to said output terminal and a "pull" configuration in which the power supply is controlled to flow from said output terminal to said input terminal. This feature makes it possible to significantly improve the rise time of the light sources, and thus to further increase the bandwidth of the system.

[0029]

[0027] In one embodiment of the invention, each switching means comprises a switch mounted in parallel with the light source with which it is associated. Where appropriate, the safety module comprises a controller arranged to detect a failure of each light source as a function of a comparison of the value of a voltage across the terminals of the switch mounted in parallel with this light source with a given threshold value.

[0030]

[0028] In this embodiment, each switch is thus connected to the terminals of the associated light source, so that a measurement of the voltage across the switch indicates the voltage across the associated light source. It is thus possible, for example, to detect an opening fault of the light source when the voltage between the drain and the source of the switch is greater than a first threshold value or a short-circuit fault of the light source when the voltage between the drain and the source of the switch is less than a second threshold value.

[0031]

[0029] Preferably, each switch has an open default configuration, and upon detection of a failure of a light source, the controller is arranged to control the closing of the associated switch.

[0032]

[0030] In another embodiment, the security module may comprise a shunt resistor connected in series with each light source, and a controller arranged to detect a failure of each light source as a function of a comparison of the value of a voltage across the shunt resistor associated with a given threshold value.

[0031] All of the components of the security module may be formed by the same integrated circuit or by a plurality of separate electronic components.

[0033]

[0032] In an exemplary embodiment of the invention, each switch may comprise an optocoupler. This characteristic makes it possible to ensure galvanic isolation between the modulation unit, which generates high-frequency modulation signals, and the security module, so as to prevent the security module from being subjected to electromagnetic interference linked to a high-frequency permutation.

[0034]

[0033] Advantageously, the calculation unit is able to receive from the security module information relating to a detection of a failure of a light source of said plurality of light sources. Where appropriate, the calculation unit is arranged to generate, in response to the reception of said information, a new modulating data sequence and to transmit said new modulating data sequence to the modulation unit for the emission of a light beam modulated by the emission module.

[0035]

[0034] Beyond maintaining the photometric and telemetry functions in the event of a failure of a light source, this characteristic makes it possible to adapt the light power of the modulated light beam in order to avoid degrading the performance of the system as much as possible.

[0036]

[0035] In an exemplary embodiment, the calculation unit is arranged to: a. in the absence of failure of a light source of said plurality of light sources, generate a first modulating data sequence having a first duty cycle and to transmit said first modulating data sequence to the modulation unit for the emission of a light beam modulated by the emission module; b. in response to the reception of information relating to a detection of a failure of a light source of said plurality of light sources, generate a second modulating data sequence having a second duty cycle greater than the first duty cycle and to transmit said second modulating data sequence to the modulation unit for the emission of a light beam modulated by the emission module.

[0037]

[0036] It is thus understood that the second sequence of modulating data has a number of bits of value “1” greater than that of the first sequence of modulating data, which thus makes it possible to obtain a modulated light beam whose light power is maintained at a substantially constant value following the failure of a light source.

[0038]

[0037] Advantageously, the telemetry system comprises a reception module capable of receiving a light beam and 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, the or each elementary acquisition module being capable of generating a data sequence, called demodulated, from the electrical signal converted by the photodetector. Where appropriate, the calculation unit being capable of receiving a demodulated data sequence generated by the or each elementary acquisition module from a light beam received by the reception module, the calculation unit being arranged to determine a time of flight separating the emission of said modulated light beam emitted from the reception of said light beam received from said demodulated data sequence and said modulating data sequence

[0039]

[0038] Preferably, the reception module comprises a plurality of elementary acquisition modules. Advantageously, the plurality of elementary acquisition modules is arranged in a matrix.

[0040]

[0039] For example, each photodetector, or each plurality of photodetectors, may have a width and / or a length of less than 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.

[0041]

[0040] According to an exemplary embodiment of the invention, the reception module may comprise an optical unit arranged in front of the elementary acquisition module(s).

[0042]

[0041] In one embodiment of the invention, the or each elementary acquisition module comprises a plurality of photodetectors and at least one electronic component arranged to generate an elementary detection signal as a function of the sum of the electrical signals converted by said photodetectors. For example, all of the photodetectors of the same elementary acquisition module can form a sensor, for example a single electronic component.

[0043]

[0042] In a particular embodiment, the outputs of the photodetectors of each elementary acquisition module are connected in parallel to a comparator arranged to compare the sum of the electrical signals converted by these photodetectors with said threshold value associated with this elementary acquisition module and to generate said demodulated data sequence as a function of said comparison. The comparator thus forms a unit for demodulating the light beam received by the reception module, capable of extracting a data sequence, called demodulated, from the electrical signals converted by the photodetectors.

[0044]

[0043] Advantageously, the or each photodetector of the or each elementary acquisition module is an avalanche photodiode, in particular a single-photon 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.

[0045]

[0044] Advantageously, 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 emitted modulated light beam from the reception of said received light beam from the values ​​of the correlation function.

[0045] Each value of the correlation function estimated by the calculation unit is associated with a value of a time shift of the modulating data sequence, or of the demodulated data sequence, used to estimate this value of the correlation function. The correlation function between this demodulated data sequence and the modulating data sequence is therefore a function of the autocorrelation of this modulating data sequence.

[0046]

[0046] It is thus possible to detect the presence of this modulating 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.

[0047]

[0047] Preferably, the calculation unit is arranged to determine the value of a peak of said correlation function, to compare said peak value with a predetermined threshold value and to detect the presence of said modulating data sequence in the demodulated data sequence as a function of said comparison. The calculation unit may for example conclude that said modulating data sequence is present in said demodulated data sequence only if said peak value is greater than the predetermined threshold value.

[0048]

[0048] Advantageously, the calculation unit is arranged to generate a modulating data sequence of pseudo-random binary type and to transmit the modulating data sequence to the modulation unit of the transmission module for the transmission of a light beam modulated by the transmission module.

[0049]

[0049] 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.

[0050]

[0050] 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.

[0051]

[0051] Taking into account the autocorrelation properties of pseudo-random binary sequences, the correlation function thus estimated will thus 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.

[0052]

[0052] 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.

[0053]

[0053] 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.

[0054]

[0054] In an exemplary embodiment of the invention, the transmission module is arranged in a front headlight of the motor vehicle. Preferably, the reception module and the transmission module are arranged in the same front headlight of the vehicle.

[0055]

[0055] Advantageously, the emission module is arranged so that the light beam participates, totally or partially, in 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.

[0056]

[0056] The invention also relates to a telemetry method implemented by a system according to the invention.

[0057]

[0057] 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.

[0058]

[0058] 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:

[0059]

[0059] [Fig.1] represents, schematically and partially, a view of a telemetry system of a motor vehicle according to an exemplary embodiment of the invention.

[0060]

[0060] [Fig. 2] represents, schematically and partially, an exemplary embodiment of a transmission module of the telemetry system of [Fig. 1]; and

[0061]

[0061] [Fig.3] represents, schematically and partially, an example of operation of the system of [Fig.1] during the implementation of a telemetry method.

[0062]

[0062] It should be noted that in these figures the structural and / or functional elements common to the different variants may have the same references.

[0063]

[0063] Of course, various other modifications may be made to the invention within the scope of the appended claims.

[0064]

[0064] With reference to [Fig. 1], the present invention is a telemetry system 1 of a vehicle comprising a transmission module 2, a reception module 3, and a calculation unit 4.

[0065]

[0065] The emission module 2 comprises a light module 21 capable of emitting a first light beam F1, and a modulation unit 22 capable of receiving a modulating data sequence Seq_m and arranged to modulate the light beam F1 emitted from said modulating sequence Seq_m.

[0066]

[0066] The first emission module 2 is for example arranged in a headlight of the motor vehicle.

[0067]

[0067] The light module 21 comprises a plurality of light sources 21a, connected in series one after the other. In the example described, each light source 21a is a light-emitting diode of a size less than 500 micrometers, preferably of a size of substantially 300 micrometers, and the light module comprises at least three sources 21a connected in series. It may be provided that each light source 21a is formed from a block of several elementary light sources connected in parallel, without departing from the scope of the present invention. It may also be provided that the light module 21 comprises other branches of light sources connected in series one after the other, the branches being connected in parallel, without departing from the scope of the present invention.

[0068]

[0068] The light sources 21 a are arranged so as to have an emission direction identical to each other, all of the light sub-beams emitted by these light sources 21 a forming a light beam F1.

[0069]

[0069] The light module 21 is arranged so that the light beam F1 that it emits has an electromagnetic spectrum of which at least a portion is located in the visible spectrum. Preferably, the spectrum of this light beam F1 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.

[0070]

[0070] To the extent that the light beam F1 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, the light module 21 may comprise an optical unit arranged to shape this light beam F1 so that its photometric distribution satisfies the requirements of said function. For example, it may be provided that the light beam F1 participates in the realization of a function of the daytime running light, or DRL, type.

[0071]

[0071] In addition to this photometric function, the light beam F1 allows 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.

[0072]

[0072] For these purposes, the modulation unit 22 is arranged to modulate the light beam F1 emitted by the light module 21, from the sequence of modulating data Seq_m that it receives, for example by controlling the electrical power supplied to the series of light sources 21a of the light module.

[0073]

[0073] It will thus be possible to provide that the modulation unit 22 comprises a generator of a pulse width modulated control signal. This control signal makes it possible to control a switching power supply (not shown) supplied to the first light source 21a of the series of light sources 21a of the light module 21. Conventionally, the duty cycle of this control signal, set by the modulation unit 22, thus makes it possible to control the average electrical power supplied to the light sources 21a, and therefore to control the light intensity of the light beam F1, so as to satisfy the requirements of the photometric function that it performs.

[0074]

[0074] In the example described, the modulation unit 22 is arranged to convert the data sequence Seq_m 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).

[0075]

[0075] Each light sub-beam emitted by a light source 21a, and therefore the light beam F1 thus emitted, is 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 F1 to transport the data sequence Seq_m.

[0076]

[0076] If an object is present in the environment of the motor vehicle, it can reflect this light beam F1 towards the reception module 3, which thus receives a light beam F2.

[0077]

[0077] This reception module 3 comprises a plurality of elementary acquisition modules

[0078] 32i,j. Each elementary acquisition module 32i,j comprises several photodetectors 32ak,l each capable of converting a light signal that it receives into an electrical signal Selk,l. Each elementary acquisition module 32i,j further comprises a demodulation unit 34, comprising a comparator, to the input of which all the outputs of the photodetectors 32ak, I are connected in parallel. The comparator thus receives an elementary detection signal formed from the sum of the electrical signals Selk, I from these photodetectors 32ak,l. The comparator is arranged to compare this elementary detection signal with a given threshold value, the comparison giving a high value, or a “1” when the elementary detection signal is greater than the threshold value, and a low value, or a “0”, when the elementary detection signal is less than the threshold value.The demodulation unit 34 is thus arranged to generate a demodulated binary sequence Seq_di,j, which it transmits to the calculation unit 4.

[0079]

[0078] In the example described, the photodetectors 32ak,l are identical and are each formed by a single-photon avalanche photodiode, or SPAD, these photodiodes and the demodulation unit 34 being integrated into a silicon photomultiplier, or SiPM. 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.

[0080]

[0079] Each electrical signal Selk, I translates the activation and deactivation sequences of the photodiode 32ak, l under the effect of photons having reached this photodiode. An incident photon can in fact trigger an avalanche effect leading to the generation of an electrical signal Selk. l for an elementary period of one or a few nanoseconds, during which the photodiode is inoperative. Then, the photodiode becomes, again, waiting for a new incident photon, no electrical signal then being generated by this photodiode in this state. The elementary detection signal resulting from the sum of these electrical signals Selk. l therefore translates an estimate of the number of photons having reached the sensor during this each elementary period. It thus contains information relating to the optical power incident on the sensor, which can comprise a part of the beam emitted by the emission module then reflected by an obstacle.

[0081]

[0080] As a variant, it may be possible to replace the comparator of the demodulation unit

[0082] 34 by active circuits, the demodulated data sequence being in this case directly a digital sequence formed of “1” and “0”.

[0083]

[0081] In the example described, the reception module 3 is arranged in the headlight of the motor vehicle, next to the transmission module 2.

[0084]

[0082] The calculation unit 4 is capable of receiving the demodulated binary sequences Seq_di,j, generated by the elementary acquisition modules 32 i,j and of detecting in each demodulated binary sequence Seq_di,j, the presence of the modulating data sequence Seq_m. The demodulation units 34 thus make it possible to reduce the quantity of data to be manipulated by the calculation unit, thus operating a compression of the elementary detection signals Sdei.

[0085]

[0083] For these purposes, the calculation unit 4 is thus arranged to estimate values ​​of a correlation function FcorriJ between each demodulated binary sequence Seq_di,j, and said modulating data sequence Seq_m, and to detect in this demodulated binary sequence Seq_di,j, the presence of the modulating data sequence Seq_m from these values ​​of the correlation function FcorriJ. In the event of detection, it can then determine a time of flight T separating the emission of said first modulated light beam emitted F1 from the reception of said received light beam F2.

[0086]

[0084] 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. 3] which represents a telemetry method implemented by the lighting system 1.

[0087]

[0085] In a first step E1, the calculation unit 4 generates, periodically, a modulating data sequence Seq_m, for example of binary type, composed of “0” and “1”, pseudo random and of maximum size, also called M-sequence, having a duty cycle of 50%.

[0088]

[0086] The calculation unit 4 transmits the modulating data sequence Seq_m to the modulation unit 22 of the transmission module 2 for the transmission of the light beam F1 by the transmission module 2.

[0089]

[0087] In a second step E2, the modulation unit 22 modulates each sub-beam emitted by each light source 21a, and therefore the light beam F1 emitted by the light module 21 from this data sequence Seq_m. Thus, the modulation unit 22 converts the data sequence Seq_m into a modulating signal and modulates the initial control signal using this modulating signal.

[0090]

[0088] It will be noted that in the example described, each light pulse of the light beam F1 emitted by the light module 21 corresponds to a bit of value “1” of the modulating sequence Seq_m. The average power of a portion of the light beam F1 containing the sequence Seq_m is thus defined by the number of bits of value “1” of this sequence Seq_m with respect to the total number of bits of this sequence, by the duration of the pulses and by the peak power of these pulses.

[0091]

[0089] The light beam F1 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.

[0092]

[0090] Depending on the angular position of the object O, the light beam F2 received by the reception module 3 is thus concentrated on one of the elementary acquisition modules 32 i,j.

[0093]

[0091] 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 reception module 3. The light beam F2 received by the reception module 3 is thus composed of a part of the light beam F1 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.

[0094]

[0092] In a third step E3, each of the elementary acquisition modules 32i,j thus extracts, using its demodulation unit 34, a demodulated binary sequence Seq_di,j which it transmits to the calculation unit 4

[0095]

[0093] For each demodulated binary sequence Seq_di,j that it receives, the calculation unit 4 estimates, in a fourth step E4, values ​​of a correlation function FcorriJ between the modulating sequence Seq_m and this demodulated binary sequence Seq_di,j.

[0096]

[0094] 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 each demodulated binary sequence Seq_di,j and the modulating sequence Seq_m delayed according to each of the time shift values.

[0097]

[0095] Taking into account the autocorrelation and cross-correlation properties of the modulating sequence, the correlation function Fcorri will thus be maximum for a time shift value corresponding to the time of flight of the light beam F1, separating the instant when it is emitted by the emission module 2 and the instant when it is received by an elementary acquisition module 32 i, j of the reception module 3, the modulating sequence Seq_m delayed by this value thus corresponding substantially to the demodulated binary sequence Seq_di,j to within the noise.

[0098]

[0096] In a fifth step E5, the calculation unit 4 identifies the maximum value Fcorr_max of each correlation function Fcorr associated with each elementary acquisition module 32i,j and compares it to a threshold value Vs.

[0099]

[0097] In the case where this maximum value Fcorr_max is greater than the threshold value Vs, the modulating sequence Seq_m is considered to be detected by the calculation unit 4 in the demodulated binary sequence Seq_di,j from the elementary acquisition module 32i,j associated with this correlation function Fcorrij. An object O is therefore detected in the angular range, or the pixel, monitored by this elementary acquisition module 32i,j and the calculation unit 4 can then estimate, in a sixth step E6, the value T of the time of flight of the light beam F1 between the object O and the vehicle, associated with this maximum value, as well as the distance d separating the object O from the vehicle.

[0100]

[0098] Referring again to [Fig. 1], the transmission module 2 comprises a security module 23.

[0101]

[0099] This security module 23 is, on the one hand, capable of detecting a failure of each of the light sources 21 a.

[0102]

[0100] On the other hand, this security module 23 comprises a plurality of switching means, which will be detailed in connection with [Fig. 2]. Each switching means is associated with one of the light sources 21 a and is capable of short-circuiting this light source. When a light source 21 a is short-circuited by the associated switching means, the electrical power supply flowing through the series of light sources 21 a passes through the switching means rather than the short-circuited light source to reach the next light source.

[0103]

[0101] The safety module 23 is thus arranged to, in response to the detection of a failure of a light source 21a, control the switching means to short-circuit said faulty light source and authorize the emission of the light beam F1 by the other light sources of said plurality of light sources 21a.

[0104]

[0102] It is thus understood that, when a light source 21 a is faulty, the light beam F1 continues to be emitted, and the functions of the system 1 are thus maintained.

[0105]

[0103] The information relating to a detection of a failure of a light source 21a is transmitted by the security module 23 to the calculation unit 4.

[0106]

[0104] At the following iteration of step E1, the calculation unit 4 then generates, periodically, a new modulating data sequence Seq_m, the duty cycle of which is greater than that of the sequence generated when no light source 21a was faulty.

[0107]

[0105] It is thus understood that this new sequence of modulating data Seq_m has a number of bits of value “1” greater than that of the previous sequence of modulating data, which thus makes it possible to obtain a modulated light beam F1 whose light power is maintained at a substantially constant value following the failure of the light source 21 a.

[0108]

[0106] With reference to [Fig. 2], an example embodiment of the transmission module 2 and the security module 23 will now be described.

[0109]

[0107] The security module 23 comprises a plurality of switches 23a. Each switch 23a comprises a transistor connected in parallel with one of the light sources 21a, thus forming the switching means associated with this light source 21a.

[0110]

[0108] The safety module 23 further comprises a controller 23b. The controller 23b is capable of measuring the voltage across each switch 23a.

[0111]

[0109] The controller 23b can thus detect an opening fault of a light source 21a when the voltage between the drain and the source of the associated switch 23a is greater than a first threshold value or even a short-circuit fault of a light source 21a when the voltage between the drain and the source of the associated switch 23a is less than a second threshold value.

[0112]

[0110] It will be noted that each switch 23a thus has an open default configuration, the electrical supply passing through the series of light sources 21a by crossing each of these light sources 21. Conversely, when a failure of a light source 21a is detected, the controller 23b is then arranged to control the closing of the associated switch 23a, this electrical supply then passing through this switch 23a rather than through the light source 21a.

[0113]

[0111] In the example described, all of the components of the security module 23, and in particular the switches 23a and the controller 23b, are formed by the same integrated circuit.

[0114]

[0112] It will also be noted that the modulation unit 22 is connected to both an input terminal and an output terminal of said series of light sources 21a. This modulation unit 22, also called a “high-frequency driver”, is thus arranged to alternate between a “push” configuration in which the electrical power supply is controlled to flow from said input terminal to said output terminal and a “pull” configuration in which the electrical power supply is controlled to flow from said output terminal to said input terminal.

[0115]

[0113] The foregoing description clearly explains how the invention makes it possible to achieve the objectives it has set itself, namely to provide a telemetry system for a motor vehicle, capable of performing both a given regulatory photometric function and a telemetry function, with high bandwidth and light power and optimal energy efficiency, and of which these functions remain ensured even in the event of failure of a light source of the system. These objectives are achieved in particular using a safety module capable of identifying the failure source and short-circuiting it to allow the passage of the electrical power signal carrying the modulating data sequence only through the other light sources.

[0116]

[0114] 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 is also possible to consider replacing the transistors in the safety module with optocouplers or to detect a failure of a light source by measuring the voltage across a shunt resistor connected in series with this light source rather than by measuring the voltage across the switch itself.

Claims

Claims

1. Telemetry system (1) of a motor vehicle comprising: a. an emission module (2) comprising a light module (21) comprising at least a plurality of light sources (21a) connected in series and capable of emitting a light beam (F1) whose spectrum has at least one portion in the visible spectrum and a modulation unit (22) capable of receiving a data sequence, called modulating, and arranged to modulate said light beam emitted by said plurality of light sources from the received data sequence; b.a calculation unit (4) arranged to generate a modulating data sequence (Seq_m) and to transmit said modulating data sequence to the modulation unit (22) for the emission of a modulated light beam (F1) by the emission module; characterized in that it comprises a safety module (23) capable of detecting a failure of each of the light sources of said plurality of light sources; in that the safety module comprises a plurality of switching means (23a) each associated with one of the light sources, the safety module being arranged to, in response to the detection of a failure of a light source, control the switching means to short-circuit said faulty light source and authorize the emission of the light beam by the other light sources of said plurality of light sources.

2. Telemetry system (1) according to the preceding claim, characterized in that the modulation unit (22) is arranged to modulate said light beam (F1) emitted by said plurality of light sources (21 a) from the received data sequence (Seq_m) at a frequency greater than 5 MHz. [Claim s] Telemetry system (1) according to one of the preceding claims, characterized in that the modulation unit (22) is arranged to control, from the modulating data sequence (Seq_m), a power supply supplied to said plurality of light sources (21 a) to modulate the light beam (F1) emitted by said plurality of light sources, in that the modulation unit is connected to both an input terminal and an output terminal of said plurality of light sources and in that the modulation unit is arranged to alternate between a "push" configuration in which the power supply is controlled to flow from said input terminal to said output terminal and a "pull" configuration in which the power supply is controlled to flow from said output terminal to said input terminal.

4. Telemetry system (1) according to one of the preceding claims, characterized in that each switching means (23a) comprises a switch mounted in parallel with the light source (21a) with which it is associated, and in that the safety module comprises a controller (23b) arranged to detect a failure of each light source as a function of a comparison of the value of a voltage at the terminals of the switch mounted in parallel with this light source with a given threshold value.

5. Telemetry system (1) according to the preceding claim, characterized in that each switch (23a) comprises an optocoupler. [Claim s] Telemetry system (1) according to one of the preceding claims, characterized in that the calculation unit (4) is capable of receiving from the security module (23) information relating to a detection of a failure of a light source (23a) of said plurality of light sources and in that the calculation unit is arranged to generate, in response to the reception of said information, a new modulating data sequence (Seq_m) and to transmit said new modulating data sequence to the modulation unit (22) for the emission of a modulated light beam (F1) by the emission module (2).

7. Telemetry system (1) according to the preceding claim, characterized in that the calculation unit (4) is arranged to: a. In the absence of failure of a light source (21 a) of said plurality of light sources, generate a first modulating data sequence (Seq_m) having a first duty cycle and to transmit said first modulating data sequence to the modulation unit (22) for the emission of a modulated light beam (F1) by the emission module; b in response to the reception of information relating to a detection of a failure of a light source of said plurality of light sources, generate a second modulating data sequence (Seq_m) having a second duty cycle greater than the first duty cycle and to transmit said second modulating data sequence to the modulation unit (22) for the emission of a modulated light beam (F1) by the emission module.

8. Telemetry system (1) according to the preceding claim, characterized in that it comprises a reception module (3) capable of receiving a light beam (F2) and comprising at least one elementary acquisition module (32i,j) comprising at least one photodetector (32ak,l) capable of converting a light signal that it receives into an electrical signal (Selk, I), the or each elementary acquisition module being capable of generating a data sequence, called demodulated, (Seq_di,j) from the electrical signal converted by the photodetector; and in that the calculation unit (4) being capable of receiving a demodulated data sequence (Seq_di,j) generated by the or each elementary acquisition module from a light beam received (F2) by the reception module, the calculation unit (4) being arranged to determine a time of flight (T) separating the emission of said modulated light beam (F1) emitted from the reception of said light beam received from said demodulated data sequence (Seq_di,j) and said modulating data sequence (Seq_m)

9. Telemetry system according to the preceding claim, characterized in that the calculation unit (4) is arranged to estimate values ​​of a correlation function (FcorriJ) between said demodulated data sequence (Seq_di j) and said modulating data sequence (Seq_m) and to determine a flight time (T) separating the emission of said modulated light beam (F1) emitted from the reception of said received light beam (F2) from the values ​​of the correlation function.

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

11. Telemetry system (1) according to the preceding claim, in which the emission module (2) is arranged so that the light beam (F1) participates, totally or partially, in the realization of a predetermined regulatory photometric function.

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