A motor vehicle detection system comprising a light beam emission module and a light beam reception module

Abstract

The invention relates to a lighting system for a motor vehicle comprising an emission module (2) having two light modules (21a, 21b) capable of emitting light beams (F21a, F21b) of distinct power, a modulation unit (22) capable of modulating said beams from data sequences of distinct duty cycles; a reception module (3) capable of receiving a light beam (F2); and a processing unit (4) arranged to determine a time of flight (τ) 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 (Sel) converted by the photodetector from said received light beam. Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: A motor vehicle detection system comprising a light beam emission module and a light beam reception module

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

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

[0003] Conventionally, the light source that emits this light beam is controlled by a pulse-width modulated (PWM) electrical signal. The light source is thus periodically switched on and off by this PWM signal, so that the emitted light beam consists of successive light pulses occurring at a frequency high enough that they are indistinguishable to the human eye. The intensity of the emitted light beam is a function of the duty cycle of this PWM signal, making it possible to control it by adjusting this duty cycle and thus implement a photometric function.

[0004] Beyond performing one or more photometric functions, such as daytime running lights or low beams, various other functions can be implemented by this type of lighting module. For example, the light source of the lighting 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 receiver module to receive the emitted light beam after reflection from an object near the vehicle. A vehicle's computer unit can then, after detecting the data sequence in the received light beam, determine the time of flight of the emitted light beam and thus estimate the distance between the vehicle and the object.

[0005] In this way, the light beam can retain its original function, namely to perform a photometric function, while allowing the light 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 presents a drawback for certain photometric functions, particularly for signaling functions. Indeed, a photometric function must meet regulatory requirements, notably in terms of luminous power and its combination with other photometric functions. For example, a daytime running lamp (DRL) is legally limited to a maximum intensity of 1200 cd. Consequently, its use for a rangefinding function does not allow for the detection of an object beyond a certain distance, for example, 50 meters. Furthermore, it is not possible to combine this function with a more powerful function, such as high beams, as a daytime running lamp should normally switch off when the vehicle's nighttime lighting is activated.

[0007] There is therefore a need for a lighting system of 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 falls within this context and aims to meet this need.

[0009] To this end, the invention relates to a lighting system for a motor vehicle, including: 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 a 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 a portion in the visible spectrum, and a modulation unit 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 receiving module capable of receiving a light beam, in which the receiving module includes an elementary acquisition module comprising a photodetector capable of converting a light signal it receives into an electrical signal.

[0010] According to the invention, the lighting system is characterized in that it comprises a processing 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 processing 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 modulated light beam by the second light module; and in that the computing unit is arranged to determine a time of flight separating the emission of the first or second modulated light beam emitted, from the reception of a light beam received by the receiving 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, with an intensity of less than 2000 cd, emitted by a light module of the emitting module, which natively performs a first photometric function, such as a daytime running light. The resulting light beam could, 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 for performing 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 processing unit can thus detect, from the electrical signal converted by the photodetector, the presence of this modulating sequence in a beam received by the receiver module, thereby detecting the presence of an object in the vehicle's vicinity and estimating its distance from the vehicle. Given the luminous intensity of the first emitted beam, detection can be performed in a relatively close field, less than 30 meters.

[0012] Simultaneously or sequentially, the invention further proposes to modulate another high-power light beam, for example, one with an intensity greater than 50,000 cd, emitted by another light module of the emitting module, which natively performs a second photometric function, such as road lighting. However, this second beam will be modulated with a data sequence having a low duty cycle, so that the average power of the second modulated beam is particularly low, especially compared to the average power of the first modulated beam. It is thus understood that the second modulated beam is imperceptible and that it allows the second light module to maintain a substantially off appearance, so as to meet the regulatory requirements of the first photometric function, while allowing the processing unit to detect, from From this second modulated beam, the presence of an object in the vehicle's vicinity can be detected at a greater distance, particularly beyond 50 meters. It should be noted that it will be possible to use the same telemetry method for the first and second light beams, or conversely, to use different methods, including a method for directly estimating the time of flight of the second light beam, depending on the duty cycles employed. Therefore, the lighting system can implement telemetry functions, even for distant objects, regardless of the specific photometric function being performed.

[0013] It should be noted that the modulation unit may be the same modulation unit for the first and second light modules, or it may comprise modulation subunits, each dedicated to one of the light modules. Conversely, a single receiving module or a plurality of receiving submodules, each dedicated to one of the emitted light beams, may be used.

[0014] Advantageously, the computing unit is arranged to generate a first data sequence with a first duty cycle greater than 10% and to generate a second data sequence with a second duty cycle less than 5%. Preferably, the computing unit can generate a first sequence with a duty cycle less than or equal to 50% and can generate a second sequence with a duty cycle less than or equal to 1%. This ensures that the average luminous power of the second modulated light beam is a particularly small fraction of the average luminous power of the second light beam.

[0015] In one embodiment of the invention, the processing unit is arranged to generate a second data sequence with a determined duty cycle such that the second modulated light beam comprises a single light pulse. For example, said light pulse may be repeated periodically. If applicable, the processing unit being capable of receiving an electrical signal converted by the photodetector from a light beam received by the receiving module, the processing unit is arranged to detect a light pulse in the received light beam 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 receiving module.In this mode, the computing unit directly estimates 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 second beam's light pulse. It should be noted that this mode is particularly advantageous, given the high peak power of the light pulse. Other estimation modes could be considered. for example via a histogram or by integration, without going outside the scope of the present invention.

[0016] Preferably, the second data sequence is transmitted periodically to the modulation unit such 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, the computing unit is configured to determine the time-of-flight intervals between the emission of a train of light pulses from the second light beam and the reception of a train of light pulses detected by the receiving module.Where appropriate, the computing unit is configured to generate a histogram of determined flight times over a given period of time, to detect the presence of one or more objects in the vehicle's environment from the histogram, in particular by selecting one or more of the determined flight times whose occurrences exceed a given threshold, and possibly to estimate a distance separating said object(s) from the vehicle from the selected flight times.

[0017] In another embodiment, the light system may include a demodulation unit connected to the photodetector and arranged to extract a data sequence, said to be demodulated, from an electrical signal converted by this photodetector; and, the computing unit being capable of receiving a data sequence demodulated by the demodulation unit from an electrical signal converted by the photodetector from a light beam received by the receiving module, the computing 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 computing 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 that value of the correlation function.

[0018] Advantageously, the light system includes a demodulation unit connected to the photodetector and arranged to extract a data sequence, called demodulated data, from an electrical signal converted by this photodetector; and, the computing unit being capable of receiving a data sequence demodulated by the demodulation unit from an electrical signal converted by the photodetector from a light beam received by the receiving module, the computing 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 computing unit is arranged to generate said first modulating data sequence, and optionally 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 exhibits particularly interesting properties. Indeed, its autocorrelation function is at its maximum for a zero time lag, that is, when the sequence is compared to itself, and has a value significantly lower than this maximum for all other time lags, that is, 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 generally generated using a linear feedback shift register, or LFSR (from the English "Linear Feedback Shift Register"), which produces a periodic recurrence 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 lag value corresponding to the time of flight of the modulated light beam emitted, reflected, and then received, even in the case of significant noise. Consequently, the processing unit can identify this time lag value associated with the maximum value of the correlation function with high accuracy and deduce the distance between the object on which the beam was reflected and the motor vehicle. Furthermore, given the cross-correlation properties, it appears unlikely that the reception of a modulated light beam emitted by an equivalent system from another motor vehicle would lead to the detection of a false positive.It is finally understood that the detection is performed 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 computing 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 lag, corresponds to the number of high values within the sequence, while its value, for all other time shifts, corresponds to this number of high values ​​multiplied by the sequence's duty cycle, that is, the ratio between the number of high values ​​and the total length of the sequence. For a maximum-length pseudo-random binary sequence, also called a Maximum Length Sequence (MLS) or M-sequence, this duty cycle is 50%. This duty cycle value thus increases the accuracy of peak detection, or maximum estimation, of the autocorrelation function, and therefore the accuracy of estimating the distance between the vehicle and the detected object.

[0023] In one embodiment of the invention, the computing 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 time associated with said value. In other words, each value of the correlation function is thus associated with a time lag value of the first and / or second modulating sequence used to estimate that value of the correlation function. The computing unit is thus arranged to identify the time lag value associated with the maximum value of the cross-correlation function.

[0024] In one embodiment of the invention, the processing unit is capable of receiving an instruction to emit only the first light beam and, in response to receiving said instruction, the processing unit is configured to jointly generate and transmit 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 simultaneously performs only a telemetry function without participating in the performance of any photometric function.

[0025] Preferably, the computing unit is capable of receiving an instruction to emit only the second light beam and, in response to receiving said instruction, the computing unit is arranged to generate and transmit only said second modulating data sequence 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 computing unit is arranged to generate and transmit said first data sequence The modulation unit is used to generate and transmit a second modulating data sequence to the modulation unit for the emission of a first modulated light beam by the first light module. If necessary, the processing unit can be configured to, in response to a failure to estimate the time of flight between the emission of the first modulated light beam and the reception of a light beam by the receiving module, generate and transmit this second modulating data sequence to the modulation unit for the emission of a second modulated light beam by the second light module. It is thus understood that, in this mode, the activation of a "long-range" telemetry function performed by the second light module is only implemented when no object is detected in the near field by the processing unit, using the first light module.

[0027] In an alternative or cumulative embodiment of the invention, the processing 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 processing unit being arranged to estimate a distance separating the vehicle from an object in the vehicle's environment based on the determination of a time of flight separating the emission of the first modulated light beam from the reception of a light beam received by the receiving module. If necessary, the processing 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 processing unit can track the position of an object detected in the near field and, for example, determine that the object will move out of the detection range of the first light module, for example, when the object's distance exceeds a given threshold or by predicting the object's future position, determined from estimated values ​​of the distance separating the object from the vehicle. In this case, the processing unit can then activate the "long-range" telemetry function performed by the second light module, in order to guarantee continuous detection and tracking of the object.

[0028] Advantageously, the receiving 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 modulating data sequences, is arranged to control the activation of only one or more pixels in 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 disrupt the capabilities detection 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 receiving module.

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

[0030] The semiconductor could, for example, be gallium nitride, or GaN, capable of emitting blue light rays by electroluminescence in response to an electric current passing through it. The photoluminescent element could, 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 in response to the excitation produced by this light, of emitting yellow light rays. The photoluminescent element is arranged on the generator so that a portion of the blue light rays excites this element, causing it to emit yellow light rays by photoluminescence. The other portion of the blue light rays passes through this element. Thus, when electrically powered, the light source simultaneously emits blue and yellow light rays, the resulting light appearing white to the human eye.

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

[0032] Advantageously, each of the first and second light modules may include 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 receiving module comprises a plurality of elementary acquisition modules, each comprising a photodetector capable of converting a light signal it receives into an electrical signal.

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

[0035] Advantageously, the photodetector of the elementary acquisition module(s) is an avalanche photodiode. This type of photodetector is also known as a SPAD, from the English "Single-Photon Avalanche Diode". A 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 impact of a single photon with a high gain, for example on the order of 10⁶, and therefore to compensate for the degradation of the signal-to-noise ratio due to external conditions.

[0036] According to one embodiment of the invention, the receiving module may include 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 always, 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 estimating the distance separating this object from the vehicle, the method being implemented by a light system, in particular by a light system according to the invention.

[0041] The present invention is now described by means of purely illustrative and in no way limiting examples of the scope of the invention, and from the accompanying drawings, in which the various figures represent:

[0042] [Fig-1] represents, schematically and partially, a view of a system of a motor vehicle according to an example of an 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 scene route during the implementation of the telemetry process by the system of the [Fig. 1]

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

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

[0047] A system 1 of a motor vehicle is shown in [Fig.1] according to an example of an 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 within 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, at least a portion of which lies in the visible spectrum. In the example described, the spectrum has an intensity peak, or line, in the blue at 450 nm. It should be noted that the spectrum may have other intensity peaks in the visible and / or infrared ranges.

[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 a combination of several of these optical elements.

[0053] The light source 23a, 23b comprises, for example, a semiconductor generator (not shown), for example gallium nitride or GaN, capable of emitting, by electroluminescence and in response to an electric current passing through it, blue light beams 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 absorb blue light and, through photoluminescence and in response to the excitation caused by this light, emit yellow light rays.

[0054] The photoluminescent element is arranged on the generator such that a portion of the blue light rays excites this element, causing it to emit yellow light rays by photoluminescence. The remaining portion of the blue light rays passes through this element. Thus, the light source 23a, 23b simultaneously emits blue and yellow light rays when electrically powered, the resulting light appearing white to the human eye.

[0055] Insofar as the light beam Fia, Flb is composed, partially or entirely, of white light, it is possible to use this light beam to participate, partially or entirely, in the performance of a predetermined photometric function, particularly a regulatory one. In this case, the optical unit 24 is arranged to shape this light beam Fia, Flb so that its photometric distribution meets the requirements of said function. In the example described, the first light beam Fia participates in the performance of a daytime running light (DRL) function, while the second light beam Flb participates in the performance of a road lighting function.

[0056] In addition to this photometric function, each of these light beams Fia and Flb enables the system 1 to perform functions of detection and evaluation of the position of an object on the road, as will be described in relation to [Fig.2] which represents a telemetry process implemented by the light system 1 using one or the 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 process implemented by the system 1.

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

[0058] Since the first light beam Fia performs a DRL-type function and the second light beam Flb performs a road-type lighting function, the regulatory requirements governing the DRL-type function stipulate that the first light beam Fia must 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 enables the implementation of the same telemetry method when activated, the first light module 21a being activated, for example, during the day, and the second light module 21b being activated, for example, at night.

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

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

[0061] In a second step, the computing unit 4 generates a first modulating data sequence, Seq2a, from the initial sequence, Seqla, while preserving at least the same autocorrelation and cross-correlation properties as the initial sequence, Seqla. For example, the computing unit could generate a first data sequence, Seq2a, with a duty cycle of less than 50%, but greater than 10%. Alternatively, the first modulating sequence, Seq2a, could be identical to the initial sequence, Seqla.

[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 power supply provided to the light source 23a, 23b.

[0063] In the example described, the modulation unit 22 includes a generator of a pulse-frequency modulated control signal. This control signal controls a switched-mode power supply (not shown) for the light source 23a, 23b. Conventionally, the frequency setpoint of this control signal, determined by the modulation unit 22, thus controls the average electrical power supplied to the light source 23a, 23b, and therefore controls the luminous intensity of the light beam Fia, Flb, so as to satisfy the requirements of the photometric function 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 at 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 carry the data sequence to the receiving module 3.

[0065] It should be noted that, in the example described, each light pulse corresponds to a bit with a value of "1" in 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 with a value of "1" in this sequence Seq2a with respect to the total number of bits of this first Seq2a sequence, by the duration Tap of the pulses and by the peak power Pap of these pulses.

[0066] Since the average power of the light beam Fia, Flb is 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 Pap and the pulse duration Tap as a function of 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 should be noted that other types of modulation can be used interchangeably within the framework of the present invention, and in particular pulse coding modulation (or PCM from the English "Puse Code Modulation"), pulse amplitude modulation (or PAM from the English "Puse Amplitude Modulation"), pulse width modulation (or PWM from the English "Puse Width Modulation") or pulse position modulation (or PPM from the English "Puse 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 towards the receiving module 3. The light beam F2 received by the receiving module is thus composed of a part of the light beam Fia, Flb reflected by the object 01 and noise, for example generated by sources of parasitic light such as urban lighting, car lighting, or even the sun.

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

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

[0071] The photodetectors are identical and each consists of an avalanche photodiode in a silicon photomultiplier. These photodiodes are arranged in a matrix. It should be noted that the dimensions of the photodetectors are on the order of a micrometer. The assembly thus forms a sensor with a spatial reception resolution on the order of 1°, or even 0.1°, and whose detection capabilities, due to the use of avalanche photodiodes, are particularly high, even under 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 which it transmits to the unit demodulation 33, which can then extract a Seq3 data sequence, 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 Tap, then determine by thresholding with regard to a value determined from the peak power Pap whether this quantity of photons corresponds or not to a pulse of the light beam Fl, and therefore to a bit with a value of "1" or to a bit with a value of "0".

[0074] The demodulated binary sequence Seq3 is thus transmitted to the computing 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] Given the autocorrelation and cross-correlation properties of pseudo-random binary sequences, the correlation function Fcorr will thus be maximum for a time offset value corresponding to the time of flight of the light beam Fia, Flb, separating the instant when it is emitted by the transmitting module 2 and the instant when it is received by the receiving module 3, the first modulating sequence Seq2a delayed by this value thus corresponding substantially to the demodulated sequence Seq3, up to noise.

[0077] In a seventh step, the computing unit 4 identifies this maximum value of the correlation function Fcorr and estimates the value r of this time of flight 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, at more than 50 meters.

[0080] The first light beam Fia, performing a DRL-type function, has a first luminous intensity that is significantly lower than that of the second light beam Flb, which performs a road-type lighting function. Therefore, it should be noted that, given these luminous intensities, the first object 01 is located within the fields of both the first and second light beams Fia and Flb, while the second object 02 is located only within the field of the second light beam Flb. It is thus 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 the realization of the DRL function and the telemetry function, the light 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, concurrently with the generation of the first modulating data sequence Seq2a, the computing 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 having a single bit with a value of "1", so that the second modulated light beam has a single light pulse for a period corresponding to the total number of bits in 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, using 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 consists of a single light pulse corresponding to the bit with the value "1" of the modulating sequence Seq2a. Although the peak power Pbp of this pulse is significantly higher than the peak power Pba of the pulses of the first light beam Fia, the low duty cycle of the second modulating sequence Seq2b makes it possible to greatly 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, with regard to the first light beam Fia and maintains a substantially off 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, given its peak power Pbp, is able to reach the second object 02 to be reflected back to the receiving module 3. The second light module 21b thus makes it possible to implement a "long distance" telemetry function.

[0088] It should 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 time interval constant and whose duration is significantly greater than the duration of the light pulses.

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

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

[0091] In a sixth step, the computing 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 the said object(s) 02 from the vehicle from the selected flight times.

[0092] In an example not described, the second light beam Flb may be pixelated, and the telemetry function just described may be implemented by means of only one or more upper rows of pixels in the Flb beam, capable of reaching a range unattainable by the first light beam Fia, the remaining pixels being inactive. The light power of the second light beam Flb is further reduced, and care is taken to ensure that the echoes of this second light beam Flb do not interfere with the telemetry function implemented by the first light beam Fia.

[0093] As an alternative to the telemetry function just described in relation to [Fig. 4], the second light beam Flb can be modulated with a second data sequence Seq2b containing more than one bit with the value "1", as in [Fig. 2], while ensuring that the duty cycle of this second data sequence Seq2b is particularly low compared to the first data sequence Seq1a. The processing unit 4 can then implement the same steps of the process in [Fig. 2] to realize the "long-distance" telemetry function using the second light module 21b.

[0094] In the embodiment just described, the first and second light beams Fia and Flb are emitted simultaneously and continuously, so that the "Short range" and "long range" telemetry functions are simultaneously active.

[0095] In an undescribed variant, which can be combined with the previous embodiment, it may be provided that the computing unit 4 activates the "long range" telemetry function, by generating the second data sequence Seq2b, only when the "short range" telemetry function fails, i.e. when no object is 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.

[0096] In an undescribed variant, which can be combined with the preceding alternatives, the processing unit 4 may be provided that it activates the "long-range" telemetry function, by generating the second data sequence Seq2b, only when an object detected in the vicinity of the vehicle by the processing unit 4, using the method of [Fig. 2] implemented with the first light module 21a, is likely to move away from the vehicle and enter a field beyond the reach of the first light beam Fia. The processing unit 4 may thus implement a function to track the position of the detected object and compare the distance of this detected object to the vehicle with a given threshold value and / or predict a future position of the detected object based on the evolution of its position, and activate the "long-range" telemetry function according to this comparison and / or prediction.

[0097] The preceding description clearly explains how the invention achieves its objectives, namely, to provide a system for a motor vehicle capable of simultaneously performing a photometric function and a rangefinding function using visible light, and which enables the detection of an object over significant distances, regardless of the photometric function performed or whether the conditions are day or night. These objectives are achieved in particular by employing a second, more powerful light module that also performs a rangefinding function by modulating the light beam it emits with a sufficiently low duty cycle so that the modulated light beam does not interfere with the photometric function performed by the first light module.

[0098] In any event, the invention is not limited to the embodiments specifically described in this document, and extends in particular to all equivalent means and to any technically feasible 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 an SLED. It may also be possible to perform other photometric functions than that described, and in particular, low beam lighting functions or position light signaling functions. It may also be possible to use other methods for generating a modulating sequence than those described.

Claims

1. Demands 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 a 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 first light power, and whose spectrum has at least a 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 receiving module (3) capable of receiving a light beam (F2), in which the receiving module includes 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 processing 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 processing 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); in that the processing unit (4) is arranged to determine a time of flight (r) separating the emission of the first or second modulated light beam emitted from the reception of a light beam received by the receiving module, from an electrical signal converted by the photodetector from said received light beam and 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 predetermined regulatory photometric function 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 predetermined regulatory photometric function.

2. Light system (1) according to the preceding claim, characterized in that the computing 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. A light system (1) according to the preceding claim, characterized in that the computing unit (4) is arranged to generate a second data sequence (Seq2b) having a determined duty cycle such that the second modulated light beam (Flb) comprises a single light pulse, and in that, the computing unit (4) being capable of receiving an electrical signal (Sel) converted by the photodetector from a light beam (F2) received by the receiving module (3), the computing 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 (r) 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. A light system (1) according to any 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, referred to as the demodulated sequence, (Seq3) from an electrical signal (Sel) converted by this photodetector; and in that, the processing unit being capable of receiving a data sequence demodulated by the demodulation unit from an electrical signal converted by the photodetector from a light beam (F2) received by the receiving module (3), the processing unit is arranged to estimate values ​​of a correlation function (Fcorr) between said demodulated data sequence and said first sequence of modulating data (Seq2a) and to determine a time of flight (r) 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. Light system (1) according to any one of the preceding claims, characterized in that the computing 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 computing 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 a second modulated light beam (Flb) by the second light module (21b).

6. Light system (1) according to the preceding claim, characterized in that the computing 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 computing unit (4) is arranged to, in response to a failure to estimate a time of flight (r) separating the emission of the first modulated light beam from the reception of a light beam (F2) received by the receiving 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. A lighting system (1) according to claim 5 or 6, characterized in that the processing 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 processing unit (4) is arranged to estimate a distance (d) separating the vehicle from an object (01) in the vehicle's environment from the determination of a time of flight (r) separating the emission of the first modulated light beam from the reception of a light beam (F2) received by the receiving module (3), and for, when said estimated distance is greater than a given threshold distance, generating and transmitting said second data sequence modulating (Seq2b) to the modulation unit for the emission of a second modulated light beam (Flb) by the second light module (21b).

8. Light system (1) according to any one of claims 5 to 7, characterized in that the receiving module (3) comprises a plurality of elementary acquisition modules (32) arranged in a matrix, in that the second light module (21b) is arranged so that the second light beam (Flb) is pixelated, and in that the modulation unit (22), at the joint reception of said first and second modulating data sequences (Seq2a, Seq2b), is arranged to control the activation only of 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 any 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, wherein the first lighting 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 wherein the second lighting 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.

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