Motor vehicle detection system comprising a module for emitting, and a module for receiving, a light beam

Abstract

The invention relates to a light system for a motor vehicle, the system comprising an emitting module (2) that comprises two light modules (21a, 21b) capable of emitting light beams (F21a, F1b) having different powers, a modulation unit (22) capable of modulating the beams on the basis of data sequences having different duty cycles; a receiving module (3) capable of receiving a light beam (F2); and a computing unit (4) arranged to determine a time of flight (τ) separating the emission of the first or second emitted modulated light beam from the reception of a light beam received by the receiving module on the basis of an electrical signal (Sel) converted by the photodetector from the received light beam.

Description

Description Title of the invention: Motor vehicle detection system comprising a transmission module and a reception module for a light beam

[0001] The invention relates to the field of automotive lighting and 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 system for a motor vehicle capable of implementing telemetry functions by means of the light that it emits.

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

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

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

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

[0006] However, this type of system has a disadvantage for certain photometric functions, particularly for signaling functions. Indeed, a photometric function must meet regulatory requirements, particularly in terms of luminous power and accumulation with other photometric functions. For example, a daytime running light, or DRL, is limited by regulation to a maximum intensity of 1200 cd. Therefore, its use for a signaling function Telemetry does not allow an object to be detected beyond a certain distance, for example 50 meters. And it is not possible to combine this function with a more powerful function, such as road lighting, as a daytime running light should normally turn off when the vehicle's night lighting is activated.

[0007] There is thus a need for a lighting system for a motor vehicle, capable of performing both a given photometric function and a telemetry function, and whose detection range is optimal, regardless of the said photometric function used.

[0008] The present invention is placed in this context, and aims to meet this need.

[0009] For these purposes, the subject of the invention is a lighting system of a motor vehicle, comprising: a. an emission module comprising a first light module capable of emitting a first light beam having a first given light power and whose spectrum has at least one portion in the visible spectrum, a second light module capable of emitting a second light beam having a second given light power, greater than the first light power, and whose spectrum has at least one portion in the visible spectrum, and a modulation unit capable of receiving a data sequence, called a modulating unit, and arranged to modulate one and / or the other of said first and second light beams emitted from the received data sequence; b.a reception module capable of receiving a light beam, in which the reception module comprises an elementary acquisition module comprising a photodetector capable of converting a light signal that it receives into an electrical signal.

[0010] According to the invention, the lighting system is characterized in that it comprises a calculation unit arranged to 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 first light beam modulated by the first light module; in that the calculation unit is arranged to generate a second modulating data sequence having a second duty cycle lower than the first duty cycle and to transmit said second modulating data sequence to the modulation unit for the emission of a second light beam modulated by the second light module;and in that the calculation unit is arranged to determine a flight time separating the emission of the first or second modulated light beam emitted, from the reception of a light beam received by the reception module, from an electrical signal converted by the photodetector from said received light beam.;

[0011] It is thus understood that the invention proposes to modulate a first low-power light beam, for example whose intensity is less than 2000 cd, emitted by a light module of the emission module, which natively performs a first function photometric, such as a daytime running light. The resulting light beam may, for example, be a pulsed beam, each pulse corresponding to one or more consecutive high values ​​of the first modulating sequence and the interval separating two consecutive pulses corresponding to one or more consecutive low values ​​of the first modulating sequence. Each pulse of the modulated light beam is emitted with a peak light power, so that the average light power of the first modulated light beam emitted, necessary to perform the photometric function, is thus defined by the peak light power and the duty cycle of the modulating data sequence. Since the modulating sequence is generated cyclically, the first modulated light beam emitted will periodically contain this sequence while continuously performing the photometric function.The computing unit can thus detect, from the electrical signal converted by the photodetector, the presence of this modulating sequence in a beam received by the receiving module and thus detect the presence of an object in the vehicle's environment and estimate its distance from the vehicle. Given the light power of the first light beam emitted, the detection can be carried out in a relatively close field, less than 30 meters.

[0012] Simultaneously or sequentially, the invention further proposes modulating another high-power light beam, for example whose intensity is greater than 50,000 cd, emitted by another light module of the emission module, which natively performs a second photometric function, such as road-type lighting. However, this second beam will be modulated with a data sequence whose duty cycle is low, so that the average power of the second modulated beam is particularly low, in particular with regard to the average power of the first modulated beam.It is thus understood that the second modulated beam is imperceptible and that it makes it possible to maintain a substantially extinguished appearance of the second light module, so as to satisfy the regulatory requirements of the first photometric function, while allowing the calculation unit to detect, from this second modulated beam, the presence of an object in a more distant environment of the vehicle, in particular beyond 50 meters. It will be noted that it will be possible to use an identical telemetry method for the first and second light beams, or on the contrary to use different methods, and in particular a method of direct estimation of a flight time of the second light beam, depending on the duty cycles used. Therefore, the lighting system can implement telemetry functions, including for distant objects, regardless of the photometric function performed.

[0013] It will be noted that the modulation unit may be the same modulation unit for the first and second light modules, or comprise modulation sub-units each dedicated to one of the light modules. Symmetrically, a single reception module or a plurality of reception sub-modules may be used, each dedicated to one of the emitted light beams.

[0014] Advantageously, the calculation unit is arranged to generate a first data sequence having a first duty cycle greater than 10% and to generate a second data sequence having a second duty cycle less than 5%. Preferably, the calculation unit will be able to generate a first sequence whose duty cycle is less than or equal to 50% and will be able to generate a second sequence whose duty cycle is less than or equal to 1%. This ensures that the average light power of the second modulated light beam is a particularly low fraction of the average light power of the second light beam.

[0015] In one embodiment of the invention, the calculation unit is arranged to generate a second data sequence having a determined duty cycle so that the second modulated light beam comprises a single light pulse. For example, said light pulse may be repeated periodically. Where appropriate, the calculation unit being able to receive an electrical signal converted by the photodetector from a light beam received by the reception module, the calculation unit is arranged to detect a light pulse in the light beam received from said electrical signal and to determine a time of flight separating the emission of said light pulse from the second light beam, from the reception of said light pulse detected by the reception module.In this mode, the calculation unit thus carries out a direct estimation of the time of flight of the second light beam, by detecting, for example by thresholding a portion of the electrical signal corresponding to the duration of the second data sequence, the presence of an echo of the light pulse of the second light beam. It will be noted that this mode is particularly advantageous, given the high peak power of the light pulse. Other estimation modes may be envisaged, for example via a histogram or by integration, without departing from the scope of the present invention.

[0016] Preferably, the second data sequence is transmitted periodically to the modulation unit so that the second light beam comprises a train of light pulses separated by a constant time interval. This time interval thus makes it possible to define an unambiguous detection distance. Preferably still, the calculation unit is arranged to determine the flight times separating the emissions of a train of light pulses of the second light beam, from the reception of a train of light pulses detected by the reception module.Where appropriate, the calculation unit is arranged to generate a histogram of the flight times determined during a given period of time, to detect the presence of one or more objects in the environment of the vehicle from the histogram, in particular by selecting one or more of the determined flight times whose occurrences are greater than a given threshold, and possibly to estimate a distance separating the said object(s) from the vehicle from the selected flight times.

[0017] In another embodiment, the lighting system may comprise a unit of demodulation connected to the photodetector and arranged to extract a data sequence, called demodulated, from an electrical signal converted by this photodetector; and, the calculation unit being able to receive a data sequence demodulated by the demodulation unit from an electrical signal converted by the photodetector from a light beam received by the reception module, the calculation unit is arranged to estimate values ​​of a correlation function between said demodulated data sequence and said second modulating data sequence and to determine a time of flight separating the emission of said second modulated light beam emitted, from the reception of said received light beam, from the values ​​of the correlation function.In other words, in this embodiment, the calculation unit can estimate the values ​​of a correlation function between the demodulated data sequence and the second modulating data sequence, each value of the correlation function is associated with a value of a time shift of the modulating sequence, or of the demodulated sequence, used to estimate this value of the correlation function.

[0018] Advantageously, the light system comprises a demodulation unit connected to the photodetector and arranged to extract a data sequence, called demodulated, from an electrical signal converted by this photodetector; and, the calculation unit being able to receive a data sequence demodulated by the demodulation unit from an electrical signal converted by the photodetector from a light beam received by the reception module, the calculation unit is arranged to estimate values ​​of a correlation function between said demodulated data sequence and said first modulating data sequence and to determine a time of flight separating the emission of said first modulated light beam emitted, from the reception of said received light beam, from the values ​​of the correlation function.

[0019] Preferably, the calculation unit is arranged to generate said first modulating data sequence, and possibly said second modulating data sequence, from an initial pseudo-random binary type sequence.

[0020] A pseudo-random binary sequence, or PRBS, 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 lag, that is to say when the sequence is compared to itself, and has a value significantly lower than this maximum for all other time lags, that is to say when the sequence is compared to time-shifted versions of itself. Furthermore, the cross-correlation function between two pseudo-random binary sequences is significantly lower than the maximum of the autocorrelation functions of these sequences.Finally, this type of sequence is usually generated using a linear feedback shift register, or LFSR, which produces a periodic recurring sequence whose. pattern is a pseudo-random binary sequence.

[0021] Given the autocorrelation properties of pseudo-random binary sequences, the correlation function thus estimated will be maximum for the time shift value corresponding to the time of flight of the modulated light beam emitted, reflected and then received, even in the event of significant noise. Consequently, the computing unit can identify this time shift value associated with the maximum value of the correlation function with significant precision and deduce therefrom the distance separating the object on which the beam was reflected and the motor vehicle. Furthermore, given the cross-correlation properties, it thus appears unlikely that the reception of a modulated light beam emitted by an equivalent system of another motor vehicle will lead to the detection of a false positive.Finally, we understand that the detection is carried out not on a single pulse but on a complete data sequence, so that the signal-to-noise ratio of the system is improved.

[0022] Advantageously, the calculation unit is arranged to generate an initial pseudo-random binary sequence of maximum size and to generate said first and / or second modulating data sequence from said initial sequence. For a pseudo-random binary sequence, the maximum of the autocorrelation function, i.e. for a zero time shift, corresponds to the number of high values ​​in the sequence, while its value, for all other time shifts, corresponds to this number of high values ​​multiplied by the cycle ratio of the sequence, i.e. the ratio between the number of high values ​​and the total length of the sequence. For a pseudo-random binary sequence of maximum size, also called MLS (from the English “Maximum Length Sequence”) or M-sequence, this cycle ratio is 50%.This duty cycle value thus makes it possible to increase the accuracy of peak detection, or estimation of the maximum, of the autocorrelation function, and therefore the accuracy of estimation of the distance from the vehicle to the detected object.

[0023] In one embodiment of the invention, the calculation unit is arranged to estimate each value of the correlation function between said demodulated data sequence and said first and / or second modulating data sequence by evaluating the cross-correlation of the demodulated data sequence and the first and / or second modulating data sequence delayed by a given duration associated with said value. In other words, each value of the correlation function is thus associated with a value of a time shift of the first and / or second modulating sequence used to estimate this value of the correlation function. The calculation unit is thus arranged to identify the time shift value associated with the maximum value of the cross-correlation function.

[0024] In one embodiment of the invention, the computing unit is capable of receiving an instruction to emit only the first light beam and, in response to receiving said instruction, the computing unit is arranged to generate and transmit jointly said first and second modulating data sequences to the modulation unit for the joint emission of a first light beam modulated by the first light module and a second light beam modulated by the second light module. It is thus understood that, in this embodiment, only the first light beam performs a first photometric function and a telemetry function while the second light beam performs, simultaneously, only a telemetry function without participating in the performance of any photometric function.

[0025] Preferably, the calculation unit is capable of receiving an instruction to emit only the second light beam and, in response to receiving said instruction, the calculation unit is arranged to generate and transmit only said second sequence of modulating data to the modulation unit for the emission only of a second light beam modulated by the second light module, the first light module remaining off.

[0026] In an alternative or cumulative embodiment of the invention, the calculation unit is arranged to generate and transmit said first modulating data sequence to the modulation unit for the emission of a first light beam modulated by the first light module. Where appropriate, the calculation unit may be arranged to, in response to a failure to estimate a flight time separating the emission of the first modulated light beam from the reception of a light beam received by the reception module, generate and transmit said second modulating data sequence to the modulation unit for the emission of a second light beam modulated by the second light module. It is thus understood that, in this mode, the activation of a “long distance” telemetry function performed by the second light module is only implemented when no object is detected in the near field by the calculation unit, by means of the first light module.

[0027] In an alternative or cumulative embodiment of the invention, the calculation unit is arranged to generate and transmit said first modulating data sequence to the modulation unit for the emission of a first light beam modulated by the first light module, the calculation unit being arranged to estimate a distance separating the vehicle from an object in the environment of the vehicle from the determination of a flight time separating the emission of the first modulated light beam from the reception of a light beam received by the reception module. Where appropriate, the calculation unit may be arranged to, when said estimated distance is greater than a given threshold distance, generate and transmit said second modulating data sequence to the modulation unit for the emission of a second light beam modulated by the second light module.It is thus understood that, in this mode, the calculation unit can thus follow the position of an object detected in the near field and, for example, determine that the object will leave the detection field of the first light module, for example. example when the distance of the object exceeds a given threshold or by prediction of a future position of the object, determined from estimated values ​​of the distance separating the object from the vehicle. In this case, the computing unit can thus activate the “long distance” telemetry function carried out by the second light module, in order to guarantee continuity of detection and tracking of the object.

[0028] Advantageously, the reception module comprises a plurality of elementary acquisition modules arranged in a matrix. If necessary, the second light module can be arranged so that the second light beam is pixelated, the modulation unit, upon joint reception of said first and second sequences of modulating data, is arranged to control the activation of only one or more pixels of one or more upper rows of the second light beam for the emission of the second modulated light beam. This ensures that the second modulated light beam is received, after reflection, by the upper elementary acquisition modules of the matrix, and does not disturb the detection capabilities of the system with respect to the first light beam, which is intended to interact, after reflection, with the lower elementary acquisition modules of the reception module.

[0029] In one embodiment of the invention, each of the first and second light modules is capable of emitting a first, respectively a second, light beam whose spectrum has a peak at a wavelength in the visible, in particular between 400 nm and 500 nm. Advantageously, each light module comprises a light source comprising a semiconductor generator capable of emitting an elementary light beam, in particular whose spectrum has a peak at a wavelength in the visible, and a photoluminescent element capable of converting said elementary light beam to obtain said light beam.

[0030] 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 carried out by this light, 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.

[0031] The light source could therefore be a laser type source, a light-emitting diode, a vertical-cavity surface-emitting laser diode, also called VCSEL (from the English “Vertical-Cavity Surface-Emitting Laser”) or even a diode superluminescent or SLED (from the English “Superluminescent diode”).

[0032] Advantageously, each of the first and second light modules may comprise an optical unit arranged to project the light rays emitted by the light source to form said first or second light beam.

[0033] In one embodiment of the invention, the reception module comprises a plurality of elementary acquisition modules each comprising a photodetector capable of converting a light signal that it receives into an electrical signal.

[0034] For example, all photodetectors can form a sensor, for example a single electronic component.

[0035] Advantageously, the photodetector of the or each elementary acquisition module is an avalanche photodiode. This type of photodetector is also known as SPAD, from the English "Single-Photon Avalanche Diode". The set of avalanche photodiodes can thus form a silicon photomultiplier or SiPM (from the English "Silicon PhotoMultiplier"). This type of photodetector makes it possible to detect the incidence of a single photon with a significant gain, for example of the order of 10 6 , and therefore to compensate for the degradation of the signal-to-noise ratio due to external conditions

[0036] According to an exemplary embodiment of the invention, the reception module may comprise an optical unit arranged in front of the elementary acquisition module.

[0037] In one embodiment of the invention, the transmission module is arranged in a front headlight of the motor vehicle. Advantageously, the reception module and the transmission module are arranged in a front headlight of the motor vehicle.

[0038] Preferably, the first light module is arranged so that the first light beam participates, totally or partially, in the realization of a first predetermined regulatory photometric function and the second light module is arranged so that the second light beam participates, totally or partially, in the realization of a second predetermined regulatory photometric function.

[0039] Preferably still, the first light module is arranged so that the first light beam participates, totally or partially, in the realization of a first signaling function of the “daytime running light” type and in which the second light module is arranged so that the second light beam participates, totally or partially, in the realization of a second lighting function of the “road” type.

[0040] The invention also relates to a method for detecting an obstacle located in the environment of a motor vehicle and for estimating the distance separating this object from the vehicle, the method being implemented by a lighting system, in particular by a lighting system according to the invention.

[0041] The present invention is now described using examples which are purely illustrative and in no way limitative of the scope of the invention, and from the appended drawings, drawings in which the various figures represent:

[0042] [Fig. 1] represents, schematically and partially, a view of a vehicle system automobile according to an exemplary embodiment of the invention;

[0043] [Fig. 2] represents, schematically and partially, a telemetry method implemented by the system of [Fig. 1];

[0044] [Fig. 3] represents, schematically and partially, a top view of a road scene during the implementation of the telemetry method by the system of [Fig. 1];

[0045] [Fig. 4] represents, schematically and partially, an example of telemetry implemented by a second light module of the system of [Fig. 1],

[0046] In the following description, elements which are identical, by structure or by function, appearing in different figures retain, unless otherwise specified, the same references.

[0047] [Fig. 1] shows a system 1 of a motor vehicle according to an exemplary embodiment of the invention.

[0048] The system 1 comprises an emission module 2 arranged to emit a first light beam Fia and a second light beam Flb and a reception module 3 intended to receive a light beam F2.

[0049] In the example described, the transmission module 2 and the reception module 3 are arranged in the same front headlight of the motor vehicle. It may be provided that the modules 2 and 3 are arranged in different locations of the motor vehicle, without departing from the scope of the present invention.

[0050] The emission module 2 comprises a first light module 21a intended to emit a first light beam Fia, a second light module 21b intended to emit a second light beam Flb, and a modulation unit 22.

[0051] Each of the light modules 21a and 21b is arranged so that the light beam Fia, Flb that it emits, has an electromagnetic spectrum of which at least a portion is located in the visible spectrum. In the example described, the spectrum 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.

[0052] In order to emit this light beam Fia, Flb, the light module 21a, 21v comprises a light source 23a, 23b capable of emitting light rays and an optical unit 24a, 24b arranged to project these light rays to form the light beam Fia, Flb. In the invention, the optical unit 24a, 24b may indifferently comprise one or more reflectors, one or more lenses, one or more diaphragms or one or more collimators or even a combination of several of these optical elements.

[0053] The light source 23a, 23b comprises, for example, a semiconductor generator (not shown), for example a gallium nitride or GaN, capable of emitting, by electroluminescence and in response to an electric current passing through it, rays of blue light with an emission peak at 450 nm. The light source also comprises a photoluminescent element, in the form of a resin comprising a cerium-doped yttrium aluminum garnet, or CE:YAG, capable of absorbing blue light. and, by photoluminescence and in response to the excitation produced by this light, to emit rays of yellow light.

[0054] 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, yellow light rays. The other portion of the blue light rays passes through this element. Thus, the light source 23a, 23b simultaneously emits, when electrically powered, blue and yellow light rays, the light thus formed appearing white to the human eye.

[0055] To the extent that the light beam Fia, Flb is composed, partially or totally, of white light, it is possible to use this light beam to participate, partially or totally, in the realization of a predetermined photometric function, in particular regulatory. In this case, the optical unit 24 is arranged to shape this light beam Fia, Flb so that its photometric distribution satisfies the requirements of said function. In the example described, the first light beam Fia participates in the realization of a function of the daytime running light type, or DRL, while the second light beam Flb participates in the realization of a road lighting function.

[0056] In addition to this photometric function, each of these light beams Fia and Flb allows the system 1 to perform functions of detecting and evaluating the position of an object on the road, as will be described in connection with [Fig. 2] which represents a telemetry method implemented by the lighting system 1 using one or other of the first or second light modules 21a, 21b, as well as with [Fig. 3] which represents a top view of a road scene during the implementation of this telemetry method implemented by the system 1.

[0057] In the road scene of [Fig. 2] a motor vehicle equipped with the lighting system 1 according to the invention is shown, as well as a first object 01 located in a field relatively close to the vehicle, less than 30 meters away.

[0058] The first light beam Fia performing a DRL type function and the second light beam Flb performing a road lighting function, the regulatory requirements governing the DRL type function require that the first light beam Fia be deactivated when the second light beam Flb is activated, and vice versa. Each of the first and second light modules 21a and 21b thus makes it possible to implement the same telemetry method when it is activated, the first light module 21a being for example activated during the day, and the second light module 21b being for example activated at night.

[0059] To implement this telemetry method, the system 1 comprises a computing unit 4.

[0060] In a first step, the computing unit 4 periodically generates an initial data sequence Seqla. The initial sequence Seqla is, in the example described, a binary sequence, composed of "0" and "1", pseudo random and of maximum size, also called M-sequence, presenting a cyclic ratio of 50%.

[0061] In a second step, the calculation unit 4 generates a first data sequence Seq2a, called modulating, from the initial sequence Seq1a, while retaining at least the same autocorrelation and cross-correlation properties of the initial sequence Seq1a. For example, the calculation unit may generate a first data sequence Seq2a whose duty cycle is less than 50%, while remaining greater than 10%. Alternatively, it may be provided that the first modulating sequence Seq2a is identical to the initial sequence Seq1a.

[0062] In a third step, the modulation unit 22 modulates the light beam Fia or Flb emitted by the first or second light module 21a, 21b which is activated, from this first data sequence Seq2a, for example by controlling the electrical power supplied to the light source 23a, 23b.

[0063] In the example described, the modulation unit 22 comprises a generator of a pulse frequency modulated control signal. This control signal makes it possible to control a switching power supply (not shown) of the light source 23a, 23b. Conventionally, the frequency setpoint of this control signal, set by the modulation unit 22, thus makes it possible to control the average electrical power supplied to the light source 23a, 23b, and therefore to control the light intensity of the light beam Fia, Flb, so as to satisfy the requirements of the photometric function that it performs.

[0064] Thus, the modulation unit 22 converts the data sequence Seq2a into a modulating signal and modulates the initial control signal using this modulating signal. In other words, the light beam Fia, Flb thus emitted under the control of the modulated signal Sseqa is composed of a train of light pulses. The pulses follow one another with a sufficiently high variable frequency, for example greater than 10 MHz, in particular between 50 MHz and 100 MHz, so that the human eye can no longer distinguish them. Furthermore, the amplitude, width and / or position of each pulse with respect to the period allows the light beam Fia, Flb to transport the data sequence to the reception module 3.

[0065] It will be noted that in the example described, each light pulse corresponds to a bit of value “1” of the modulating sequence Seq2a. The average power of a portion of the light beam Fia, Flb containing the first sequence Seq2a is thus defined by the number of bits of value “1” of this sequence Seq2a with respect to the total number of bits of this first sequence Seq2a, by the duration Ta p pulses and by the peak power Pa p of these impulses.

[0066] The average power of the light beam Fia, Flb being constrained by the regulatory requirements governing the photometric function that the beam Fia, Flb must perform, the calculation unit 4 can thus determine the values ​​of the peak power Pa p and the pulse duration Ta p depending on the duty cycle of the first modulating sequence Seq2a and a photometric function setpoint, for example expressed as an average power setpoint or a frequency setpoint of the modulated signal Sseqa.

[0067] It will be noted that other types of modulation may be used indifferently within the framework of the present invention, and in particular pulse code modulation (or PGM for “Puise Code Modulation”), pulse amplitude modulation (or PAM for “Puise Amplitude Modulation”), pulse width modulation (or PWM for “Pulse Width Modulation”) or even pulse position modulation (or PPM for “Puise Position Modulation”).

[0068] The light beam Fia, Flb is thus emitted until it reaches an object 01, located in the environment of the vehicle, which reflects it in the direction of the reception module 3. The light beam F2 received by the reception module is thus composed of a part of the light beam Fia, Flb reflected by the object 01 and of noise, for example generated by sources of stray light such as urban lighting, automobile lighting, or even the sun.

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

[0070] Each of the elementary acquisition modules 32 comprises a photodetector. The light beam F2 received by the reception module 3 is thus concentrated by the optical unit 31 onto one or more of the photodetectors.

[0071] The photodetectors are identical and are each formed by an avalanche photodiode of a silicon photomultiplier. These photodiodes are distributed in a matrix fashion. It should be noted that the dimensions of the photodetectors are of the order of a micrometer. The assembly thus forms a sensor whose spatial reception resolution is of the order of 1°, or even 0.1°, and whose detection capabilities, due to the use of avalanche photodiodes, are particularly high, even in the case of degraded acquisition conditions.

[0072] In a fourth step, each of the photodetectors converts the portion of the light beam F2 that it receives into an electrical signal Sel that it transmits to the demodulation unit 33, which can then extract from it a data sequence Seq3, called demodulated, in a fifth step.

[0073] In the example described, the demodulation unit 33 can for example count, from the electrical signal Sel, the number of photons received by an elementary acquisition module 32 during a time interval corresponding to a pulse duration Ta p , then determine by thresholding with respect to a value determined from the peak power Pa p whether or not this quantity of photons corresponds to a pulse of the light beam Fl, and therefore to a bit of value “1” or to a bit of value “0”.

[0074] The demodulated binary sequence Seq3 is thus transmitted to the calculation unit 4, which estimates, in a sixth step, values ​​of a correlation function Fcorr between the first modulating sequence Seq2a and the demodulated sequence Seq3.

[0075] The calculation unit 4 thus evaluates, for a plurality of time shift values, the value of the cross-correlation, by means of a cyclic convolution product, between the demodulated sequence Seq3 and the first modulating sequence Seq2a delayed according to each of the time shift values.

[0076] Taking into account the autocorrelation and cross-correlation properties of pseudo-random binary sequences, the correlation function Fcorr will thus be maximum for a time shift value corresponding to the flight time of the light beam Fia, Flb, separating the instant when it is emitted by the transmission module 2 and the instant when it is received by the reception module 3, the first modulating sequence Seq2a delayed by this value thus corresponding substantially to the demodulated sequence Seq3, apart from the noise.

[0077] In a seventh step, the calculation unit 4 identifies this maximum value of the correlation function Fcorr and estimates the value T of this flight time of the light beam Fia, Flb between the object 01 and the vehicle, associated with this maximum value.

[0078] In an eighth step E8, the calculation unit 4 estimates the distance d separating the object 01 from the vehicle.

[0079] In the road scene of [Fig. 2] a second object 02 is also shown located in a field relatively far from the vehicle, more than 50 meters away.

[0080] The first light beam Fia performing a DRL type function, it has a first light power, substantially lower than that of the second light beam Flb, which performs a road type lighting function. Therefore, it will be noted that, taking into account these light powers, the first object 01 is located both in the fields of the first and second light beams Fia and Flb, while the second object 02 is located only in the field of the second light beam Flb. It is therefore understood that, when the second beam Flb is deactivated, for example in a daytime situation, it is impossible for the lighting system 1 to detect the second object 02.

[0081] For these purposes, when the first light beam Fia is activated for performing the DRL function and the telemetry function, the lighting system 1 implements another telemetry method using the second light module 21b and the second light beam Flb, as shown in [Fig. 4],

[0082] In a first step, concomitantly with the generation of the first modulating data sequence Seq2a, the calculation unit 4 generates a second modulating data sequence Seq2b having a duty cycle substantially lower than the duty cycle of the first modulating sequence Seq2a.

[0083] In the example described, the second modulating data sequence Seq2b may have a duty cycle less than or equal to 1%, for example by comprising a single bit of value “1”, so that the second modulated light beam comprises a single light pulse for a period corresponding to the total number of bits of the second modulating sequence Seq2b.

[0084] In a second step, the modulation unit 22 modulates the light beam Flb emitted by the second light module 21b, from this second data sequence Seq2b. The modulation unit 22 thus converts the second data sequence Seq2b into a modulating signal and modulates the initial control signal using this modulating signal.

[0085] In other words, the second light beam Flb thus emitted under the control of the modulated signal Sseqb is composed of a single light pulse corresponding to the bit of value "1" of the modulating sequence Seq2a. Although the peak power Pb p of this pulse is significantly greater than the peak power Pb apulses of the first light beam Fia, the low duty cycle of the second modulating sequence Seq2b makes it possible to significantly reduce the average power of the second light beam Flb.

[0086] Although the first and second light beams Fia and Flb are emitted jointly, this low average power of the second light beam Flb makes it substantially imperceptible, compared to the first light beam Fia and maintains a substantially extinguished appearance of the second light module 21b, which makes it possible to satisfy the regulatory requirements of the photometric function performed by the first light beam Fia.

[0087] On the other hand, the light pulse contained in this second light beam Flb, taking into account its peak power Pb p, is capable of reaching the second object 02 to be reflected towards the receiving module 3. The second light module 21b thus makes it possible to implement a “long distance” telemetry function.

[0088] It will be noted that the second data sequence Seq2b is transmitted periodically to the modulation unit 22 so that the second light beam Flb is composed of a train of light pulses separated by a constant time interval and whose duration is substantially greater than the duration of the light pulses.

[0089] In a third step, one or more of the photodetectors of the reception module 3 converts the portion of the light beam F2 that it receives into an electrical signal Sel that it transmits to the calculation unit 4 which detects, in a fourth step, for example by thresholding, the presence of a light pulse in this received light beam F2. The calculation unit can directly estimate a time of flight T separating the emission of said light pulse from the second light beam Flb, from the reception of said light pulse detected by the reception module 3.

[0090] These third and fourth steps are thus repeated by the calculation unit 4 until a series of light pulses is identified, corresponding to a train of light pulses emitted by the second light module 21b in a given period of time. In a fifth step, the calculation unit 4 generates a histogram H of the different flight times thus determined.

[0091] In a sixth step, the calculation unit 4 can thus detect the presence of one or more objects 02 in a field distant from the vehicle from the histogram H, for example by selecting one or more of the determined flight times whose occurrences are greater than a given threshold, and can thus estimate a distance separating said object(s) 02 from the vehicle from the selected flight times.

[0092] In an example not described, it may be provided that the second light beam Flb is pixelated, and that the telemetry function which has just been described is implemented by means of only one or more upper rows of pixels of the beam Flb, capable of reaching a range unattainable by the first light beam Fia, the rest of the pixels being inactive. The light power of the second light beam Flb is further reduced and it is ensured that the echoes of this second light beam Flb do not disturb the telemetry function implemented by the first light beam Fia.

[0093] As an alternative to the telemetry function which has just been described in connection with [Fig. 4], it may be provided that the second light beam Flb is modulated with a second data sequence Seq2b having more than one bit of value “1”, as in [Fig. 2], while ensuring that the duty cycle of this second data sequence Seq2b is particularly low with respect to the first data sequence Seq1a. The calculation unit 4 may then implement the same steps of the method of [Fig. 2] for the realization of the “long distance” telemetry function by the second light module 21b.

[0094] In the embodiment just described, the first and second light beams Fia and Flb are emitted simultaneously, continuously, so that the “short distance” and “long distance” telemetry functions are simultaneously active.

[0095] In a variant not described, which can be combined with the previous embodiment, it may be provided that the calculation unit 4 activates the “long distance” telemetry function, by generating the second data sequence Seq2b, only when the “short distance” telemetry function fails, i.e. when no object is detected in a field close to the vehicle by the calculation unit 4 using the method of [Fig. 2] implemented with the first light module 21a.

[0096] In a variant not described, which can be combined with the previous alternatives, it may be provided that the computing unit 4 activates the “long distance” telemetry function, by generating the second data sequence Seq2b, only when an object detected in a field close to the vehicle by the computing unit 4, by means of the method of [Fig. 2] implemented with the first light module 21a, is likely to move away from the vehicle to enter a field out of reach of the first light beam Fia. The computing unit 4 may thus implement a function for tracking the position of the detected object and compare the distance of this detected object to the vehicle with a threshold value. data and / or predict a future position of the detected object from the evolution of its position, and activate the “long distance” telemetry function based on this comparison and / or this prediction.

[0097] The foregoing description clearly explains how the invention makes it possible to achieve the objectives it has set itself, namely to provide a system for a motor vehicle capable of simultaneously performing a photometric function and a telemetry function from visible light and which makes it possible to detect an object over significant distance ranges, regardless of the photometric function performed or the night or day conditions. These objectives are achieved in particular by using a second, more powerful light module which also performs a telemetry function by modulating the light beam which it emits with a sufficiently low duty cycle so that the modulated light beam does not disturb the photometric function performed by the first light module.

[0098] 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, it may be possible to use other types of light source than that described, such as a laser diode, a VCSEL or a SLED. It may also be possible to provide other photometric functions than that described, and in particular dipped beam type lighting functions or position light type signaling functions. It may also be possible to provide other methods of generating a modulating sequence than those described.

Claims

Claims

1. Lighting system (1) of a motor vehicle, comprising: a. an emission module (2) comprising a first light module (21a) capable of emitting a first light beam (Fia) having a first given light power and whose spectrum has at least one portion in the visible spectrum, a second light module (21b) capable of emitting a second light beam (Flb) having a second given light power, greater than the second light power, and 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 one and / or the other of said first and second light beams emitted from the received data sequence;b. a reception module (3) capable of receiving a light beam (F2), in which the reception module comprises an elementary acquisition module (32) comprising a photodetector capable of converting a light signal that it receives into an electrical signal (Sel); characterized in that it comprises a calculation unit (4) arranged to generate a first modulating data sequence (Seq2a) having a first duty cycle and to transmit said first modulating data sequence to the modulation unit (22) for the emission of a first modulated light beam (Fia) by the first light module (21a);in that the calculation unit (4) is arranged to generate a second modulating data sequence (Seq2b) having a second duty cycle lower than the first duty cycle and to transmit said second modulating data sequence to the modulation unit (22) for the emission of a second modulated light beam (Flb) by the second light module (21b); and in that the calculation unit (4) is arranged to determine a time of flight (T) separating the emission of the first or second modulated light beam emitted, from the reception of a light beam received by the reception module, from an electrical signal converted by the photodetector from said received light beam.;

2. Lighting system (1) according to the preceding claim, characterized in that the calculation unit (4) is arranged to generate a first data sequence (Seq2a) having a first duty cycle greater than 10% and to generate a second data sequence (Seq2b) having a second duty cycle less than 5%.

3. Lighting system (1) according to the preceding claim, characterized in that the calculation unit (4) is arranged to generate a second data sequence (Seq2b) having a determined duty cycle so that the second modulated light beam (Flb) comprises a single light pulse, and in that, the calculation unit (4) being able to receive a signal electrical signal (Sel) converted by the photodetector from a light beam (F2) received by the receiving module (3), the calculation unit (4) is arranged to detect a light pulse in the light beam received from said electrical signal and to determine a time of flight (T) separating the emission of said light pulse from the second light beam, from the reception of said light pulse detected by the receiving module.

4. Lighting system (1) according to one of the preceding claims, characterized in that it comprises a demodulation unit (33) connected to the photodetector and arranged to extract a data sequence, called demodulated, (Seq3) from an electrical signal (Sel) converted by this photodetector; and in that, the calculation unit being able to receive a data sequence demodulated by the demodulation unit from an electrical signal converted by the photodetector from a light beam (F2) received by the reception module (3), the calculation unit is arranged to estimate values ​​of a correlation function (Fcorr) between said demodulated data sequence and said first modulating data sequence (Seq2a) and to determine a time of flight (T) separating the emission of said first modulated light beam (Fia) emitted, from the reception of said received light beam, from the values ​​of the correlation function.

5. Lighting system (1) according to one of the preceding claims, characterized in that the calculation unit (4) is capable of receiving an instruction to emit the first light beam (Fia) only and in that, in response to the reception of said instruction, the calculation unit is arranged to jointly generate and transmit said first and second modulating data sequences (Seq2a, Seq2b) to the modulation unit (22) for the joint emission of a first modulated light beam (Fia) by the first light module (21a) and of a second modulated light beam (Flb) by the second light module (21b).

6. Lighting system (1) according to the preceding claim, characterized in that the calculation unit (4) is arranged to generate and transmit said first modulating data sequence (Seq2a) to the modulation unit (22) for the emission of a first modulated light beam (Fia) by the first light module (21a), in that the calculation unit (4) is arranged to, in response to a failure to estimate a time of flight (T) separating the emission of the first modulated light beam from the reception of a light beam (F2) received by the reception module (3), generate and transmit said second modulating data sequence (Seq2b) to the modulation unit for the emission of a second modulated light beam (Flb) by the second light module (21b).

7. Lighting system (1) according to one of claims 5 or 6, characterized in that the calculation unit (4) is arranged to generate and transmit said first modulating data sequence (Seq2a) to the modulation unit (22) for emission of a first modulated light beam (Fia) by the first light module (21a), in that the calculation unit (4) is arranged to estimate a distance (d) separating the vehicle from an object (01) in the environment of the vehicle from the determination of a flight time (r) separating the emission of the first modulated light beam from the reception of a light beam (F2) received by the reception module (3), and to, when said estimated distance is greater than a given threshold distance, generate and transmit said second modulating data sequence (Seq2b) to the modulation unit for the emission of a second modulated light beam (Flb) by the second light module (21b).

8. Lighting system (1) according to one of claims 5 to 7, characterized in that the reception module (3) comprises a plurality of elementary acquisition modules (32) arranged in a matrix, in that the second lighting module (21b) is arranged so that the second light beam (Flb) is pixelated, and in that the modulation unit (22), upon joint reception of said first and second modulating data sequences (Seq2a, Seq2b), is arranged to control the activation of only one or more pixels of one or more upper rows of the second light beam for the emission of the second modulated light beam.

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

10. Lighting system (1) according to the preceding claim, in which the first lighting module (21a) is arranged so that the first light beam (Fia) participates, totally or partially, in the realization of a first predetermined regulatory photometric function and in which the second lighting module (21b) is arranged so that the second light beam (Flb) participates, totally or partially, in the realization of a second predetermined regulatory photometric function.

11. Lighting system (1) according to the preceding claim, in which the first light module (21a) is arranged so that the first light beam (Fia) participates, totally or partially, in the realization of a first signaling function of the “daytime running light” type and in which the second light module (21b) is arranged so that the second light beam (Flb) participates, totally or partially, in the realization of a second lighting function of the “road” type.

Images