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 (1) comprising an emitting module (2) that comprises a light module (21) capable of emitting a light beam (Fl, Fl') that produces a flashing photometric function and a modulation unit (22) arranged to modulate the emitted light beam on the basis of a modulating data sequence (Seq2a, Seq2b); a receiving module (3) capable of receiving a light beam (F2); and a computing unit (4) arranged to generate modulating data sequences having different duty cycles in order to emit different modulated light beams during each active and inactive phase; the computing unit being arranged to determine a time of flight (T) separating the emission of the first or of the second emitted modulated light beam from the reception of a light beam received by the receiving module (3).

Description

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 the functions of detecting an object by a motor vehicle and estimating the distance between that object and 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 vehicle's lighting system to perform a given photometric function.

[0003] Typically, the light source that emits this beam is controlled by a pulse-width modulated (PWM) electrical signal. The light source is periodically switched on and off by this PWM signal, so that the emitted 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 beam is a function of the duty cycle of this PWM signal, allowing it to be controlled by adjusting this duty cycle and thus enabling a photometric function.

[0004] Beyond performing one or more photometric functions, such as daytime running lights or low beams, this type of lighting module can implement various other functions. For example, the module's light source 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 onboard computer 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 has a drawback for certain photometric functions, particularly for flashing functions. For example, a turn signal function implemented by a light module must consist of a sequence of successive cycles, each composed of an "active" phase in which the light module is on and an "inactive" phase in which the light module is off. Therefore, its use for a telemetry function is Limited to active phases, no light beam capable of supporting this telemetry function is emitted during inactive phases. This intermittent absence can therefore lead to a loss of tracking of an object detected during an active phase, particularly when the relative speed between this object and the vehicle is high.

[0007] There is therefore a need for a lighting system for a motor vehicle, capable of performing both a given flashing photometric function and a telemetry function, the telemetry function remaining available during the inactive phases of the photometric function.

[0008] The present invention falls within this context and aims to address this need.

[0009] For these purposes, the invention relates to a lighting system for a motor vehicle, comprising: a. an emission module comprising a light module capable of emitting a light beam whose spectrum has at least a portion in the visible spectrum, and a modulation unit arranged to control the light module for the realization, from said emitted light beam, of a flashing photometric function comprising a sequence of successive cycles each composed of an active phase followed by an inactive phase, the modulation unit being capable of receiving a data sequence, called modulating, and arranged to modulate said emitted light beam 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 including 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 computing 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 lighting module during each active phase and in that the computing 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 lighting module during each inactive phase;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 light beam, emitted by a light module of the emission module only during each active phase, which natively performs a flashing photometric function, like a direction indicator. The resulting light beam could, for example, be a pulsed beam. Each pulse corresponds to one or more consecutive high values ​​of the first modulating sequence, and the interval between two consecutive pulses corresponds 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 the average light power of the first modulated light beam emitted, necessary to perform the photometric function, is 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 during each active phase.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 environment of the vehicle and estimate its distance from the vehicle.

[0012] The invention further proposes modulating another light beam, emitted by the light module of the emission module only during each inactive phase. 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 allows the light module to maintain a substantially off appearance, thereby meeting the regulatory requirements for the flashing photometric function, while still enabling the processing unit to detect, from this second modulated beam, the presence of an object during each inactive phase.It should 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 time of flight of the second light beam, depending on the duty cycles used.

[0013] In one embodiment of the invention, the light module is capable of emitting a first, or second, light beam whose spectrum has a wavelength in the visible range, in particular between 400 nm and 500 nm. For example, the first, or second, light beam may have an amber or orange color. Advantageously, the light module comprises a light source including a semiconductor generator capable of emitting an elementary light beam, in particular whose spectrum has a wavelength in the visible range, and a photoluminescent element capable of converting said elementary light beam to obtain said light beam.

[0014] The semiconductor could, for example, be gallium nitride, or GaN, capable of emitting blue light rays through electroluminescence in response to an electric current passing through it. The photoluminescent element could, for example, be under the A resin containing cerium-doped yttrium aluminum garnet (CE:YAG) capable of absorbing blue light and, through photoluminescence and in response to excitation by this light, emitting yellow light. The photoluminescent element is positioned on the generator so that some of the blue light excites it, causing it to emit orange light through photoluminescence. The remaining blue light passes through this element. Thus, when electrically powered, the light source simultaneously emits blue and yellow light in proportions such that the resulting light appears yellow, orange, or amber to the human eye.

[0015] The light source can 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 a superluminescent diode or SLED (from the English "Superluminescent diode").

[0016] In one embodiment of the invention, the light module comprises a light source, the modulation unit being arranged to control said light source for the emission of the first light beam modulated by the light module during each active phase and to control said light source for the emission of the second light beam modulated by the light module during each inactive phase. It is thus understood that the same light source is used for the emission of the first modulated light beam during the active phase and for the emission of the second modulated light beam during the inactive phase.

[0017] Advantageously, the light module may include an optical unit arranged to project the light rays emitted by the light source to form said first or second light beam.

[0018] In another embodiment, the light module comprises a first light source and a second light source, the modulation unit being arranged to drive said first light source for the emission of the first light beam modulated by the light module during each active phase and to drive said second light source for the emission of the second light beam modulated by the light module during each inactive phase.

[0019] Advantageously, the light module comprises a common optical unit arranged to project the light rays emitted by the first and second light sources to form said first and second light beams. Alternatively, the module may comprise two separate optical units, each arranged to project the light rays emitted by one or the other of the light sources to form said first and second light beams. If necessary, the second light source and the optical unit may be arranged to perform together another regulatory photometric function, which can be activated when the flashing photometric function is deactivated.

[0020] Advantageously, the computing unit is configured to generate a first data sequence with a first duty cycle greater than 10% and 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 greater than or equal to 50% and 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.

[0021] 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. Optionally, the processing unit is capable of receiving an electrical signal converted by the photodetector from a light beam received by the receiver module. The processing unit is then arranged to detect a light pulse within the received light beam from said electrical signal and to determine a time-of-flight interval between the emission of said light pulse in the second light beam and the reception of said light pulse detected by the receiver module.In this mode, the computing unit thus proceeds to 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.

[0022] Preferably, the second data sequence is periodically transmitted to the modulation unit so that the second modulated light beam emitted during an inactive phase consists of a train of light pulses separated by a constant time interval. This time interval allows for the definition of an unambiguous detection distance. Preferably, the processing 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 arranged 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 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.

[0023] In another embodiment, the lighting system may include 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 processing unit being capable of receiving a data sequence demodulated by the unit In the demodulation process, an electrical signal is converted by the photodetector from a light beam received by the receiver module. The processing unit is configured to estimate the values ​​of a correlation function between the demodulated data sequence and the second modulating data sequence, and to determine the time of flight between the emission of the second modulated light beam and the reception of the received light beam, based on the correlation function values. In other words, in this embodiment, the processing 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 time offset of the modulating sequence, or of the demodulated sequence, used to estimate that value of the correlation function.

[0024] Advantageously, the light system includes 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 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.

[0025] 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.

[0026] A pseudorandom 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. Its autocorrelation function is at its maximum for a zero time lag, that is, when the sequence is compared to itself, and is 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 pseudorandom 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 recurrent sequence whose pattern is a pseudo-random binary sequence.

[0027] Given the autocorrelation properties of pseudo-random binary sequences, the correlation function thus estimated will be maximum for the shift value The time lag corresponds to the time of flight of the modulated light beam as it is emitted, reflected, and then received, even in the presence of significant noise. Therefore, 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 receiving a modulated light beam emitted by an equivalent system from another motor vehicle would result in a false positive detection. Finally, it is understood that the detection is performed not on a single pulse but on a complete data sequence, thus improving the system's signal-to-noise ratio.

[0028] Advantageously, the computing unit is arranged to generate an initial pseudo-random binary sequence of maximum size and to generate the first and / or second modulating data sequence from said initial sequence. For a pseudo-random binary sequence, the maximum of the autocorrelation function, that is, for a zero time lag, corresponds to the number of high values ​​in the sequence, while its value, for all other time lags, corresponds to this number of high values ​​multiplied by the duty cycle of the sequence, 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 an MLS (Maximum Length Sequence) or M-sequence, this duty cycle is 50%.This duty cycle value thus makes it possible to increase the accuracy of peak detection, or maximum estimation, of the autocorrelation function, and therefore the accuracy of estimating the distance of the vehicle to the detected object.

[0029] 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.

[0030] In one embodiment of the invention, the computing unit is arranged to generate and transmit the first modulating data sequence to the modulation unit for the emission of a first light beam modulated by the light module during each active phase. The computing unit is arranged to estimate the distance between the vehicle and an object in the vehicle's environment by determining the time of flight between the emission of the first modulated light beam and the reception of a beam. The light received by the receiving module. If necessary, the processing unit is configured to estimate the relative speed of the object with respect to the vehicle based on the estimated distance. When the estimated relative speed exceeds a given threshold, the processing unit is configured to generate and transmit the second modulating data sequence to the modulation unit for the emission of a second modulated light beam by the light module during each inactive phase. Thus, the first light beam performs a telemetry function during active phases, allowing the object's speed relative to the vehicle to be estimated from several successively estimated distances.When the estimated speed, or a speed predicted from the estimated speed, exceeds a given threshold, it is possible to lose tracking of the object detected during an active phase during the subsequent inactive phase. In this case, the processing unit can activate the telemetry function performed by the second light beam during the following inactive phase(s) to ensure continuous detection and tracking of the object.

[0031] Advantageously, the receiving module comprises a plurality of elementary acquisition modules arranged in a matrix.

[0032] 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.

[0033] For example, all the photodetectors together can form a sensor, for example a single electronic component.

[0034] Advantageously, the photodetector of each elementary acquisition module is an avalanche photodiode. This type of photodetector is also known as a SPAD, from the English "Single-Photon Avalanche Diode." A collection of avalanche photodiodes can thus form a silicon photomultiplier, or SiPM (from the English "Silicon PhotoMultiplier"). This type of photodetector allows the detection of the impact of a single photon with a significant gain, for example, on the order of 10⁻¹⁰. 6 , and therefore to compensate for the degradation of the signal-to-noise ratio due to external conditions

[0035] According to one embodiment of the invention, the receiving module may include an optical unit arranged in front of the elementary acquisition module.

[0036] 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.

[0037] Preferably, the light module is arranged so that the first light beam participates, totally or partially, in the realization of a first predetermined regulatory photometric function.

[0038] Preferably, the light module is always arranged so that the first beam of light participates, wholly or partially, in the performance of a first function. of the "direction indicator" type signaling. Where appropriate, the modulation unit may be arranged so that each active phase has a duration of approximately 500 ms and each inactive phase has a duration of approximately 500 ms.

[0039] 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.

[0040] 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:

[0041] [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;

[0042] [Fig. 2] represents, schematically and partially, a telemetry process implemented by the system of [Fig. 1];

[0043] [Fig. 3] represents, schematically and partially, a top view of a road scene during the implementation of the telemetry process by the system of [Fig. 1];

[0044] [Fig. 4] schematically and partially represents a telemetry process implemented by the system of [Fig. 1]; and

[0045] [Fig. 5] represents, schematically and partially, an example of a control signal for the realization of a flashing photometric function implemented by the system of [Fig. 1],

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

[0047] [Fig. 1] A system 1 of a motor vehicle is represented according to an example of an embodiment of the invention.

[0048] System 1 includes an emission module 2 arranged to emit a light beam Fl 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 is possible for modules 2 and 3 to be arranged in different locations within the motor vehicle without departing from the scope of the present invention.

[0050] The emission module 2 comprises a light module 21 intended to emit a light beam Fl and a modulation unit 22.

[0051] The light module 21 is arranged so that the light beam Fl it emits exhibits an electromagnetic spectrum, at least a portion of which lies within the visible spectrum. In the example described, the spectrum displays lines in a wavelength range between 400 and 500 nm. It should be noted that the spectrum may also exhibit other intensity peaks in the visible and / or infrared regions.

[0052] In order to emit this light beam Fl, the light module 21 comprises a light source 23 capable of emitting light rays and an optical unit 24 arranged to project these light rays to form the light beam Fl. In the invention, the optical unit 24 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 23 includes, for example, a semiconductor generator (not shown), such as gallium nitride or GaN, capable of emitting, by electroluminescence and in response to an electric current passing through it, beams of blue light with an emission peak at 450 nm. The light source also includes a photoluminescent element, in the form of a resin containing a cerium-doped yttrium aluminum garnet, or CE:YAG, capable of absorbing blue light and, by photoluminescence and in response to excitation by this light, of emitting beams of yellow, orange, or amber light.

[0054] The photoluminescent element is positioned on the generator so that a portion of the blue light rays excites this element, causing it to emit yellow, orange, or amber light rays through photoluminescence. The remaining blue light rays pass through this element. Thus, when electrically powered, the light source 23 simultaneously emits blue and yellow light rays, the resulting light appearing orange or amber to the human eye.

[0055] Insofar as the light beam Fl is composed, partially or entirely, of orange or amber 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 Fl so that its photometric distribution meets the requirements of said function. In the example described, the light beam Fl participates in the performance of a direction indicator function.

[0056] To this end, the modulation unit 22 cyclically controls the light source 23 so that, for one cycle, the light beam Fl is emitted for one period TTI, then deactivated for one period TTI. The function performed by the light module 21 is thus flashing and comprises a sequence of cycles, each consisting of an active phase, in which the light beam Fl is emitted, and an inactive phase, in which the light beam Fl is off.

[0057] In addition to this photometric function, this light beam Fl allows 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 the light module 21, as well as with [Fig. 3] which represents a top view of a road scene during the implementation of this telemetry process implemented by system 1.

[0058] 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.

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

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

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

[0062] In a third step, the modulation unit 22 modulates the light beam Fl emitted by the light module 21 during each active phase, from this first data sequence Seq2a, for example by controlling the power supply provided to the light source 23.

[0063] In the example described, the modulation unit 22 includes a generator of a pulse frequency modulated control signal. This control signal allows control of a switched-mode power supply (not shown) to the light source 23. Conventionally, the frequency setpoint of this control signal, fixed by the modulation unit 22, thus allows control of the average electrical power supplied to the light source 23, and therefore control of the luminous intensity of the light beam Fl, so as to satisfy the requirements of the photometric function it performs.

[0064] Thus, the modulation unit 22 converts the Seq2a data sequence into a modulating signal and modulates the initial control signal using this modulating signal. In other words, the light beam Fl, emitted during an active phase 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, specifically between 50 MHz and 100 MHz, so that they are indistinguishable to the human eye. Furthermore, the amplitude, width, and / or position of each pulse relative to the period allows the light beam Fl to carry the data sequence to the receiving module 3.

[0065] Note that, in the example described, each light pulse corresponds to a bit with the value "1" in the modulating sequence Seq2a. The average power of a portion of the light beam Fl containing the first Seq2a sequence is thus defined by the the number of bits with the value "1" in this Seq2a sequence compared to the total number of bits in this first Seq2a sequence, multiplied by the duration T p pulses and by the peak power P p of these impulses.

[0066] Since the average power P of the light beam Fl is constrained by the regulatory requirements governing the photometric function that the beam Fl must perform, the calculation unit 4 can thus determine the peak power values ​​P p and the pulse duration T pdepending 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 should be noted that other types of modulation can be used interchangeably within the framework of the present invention, and in particular pulse code modulation (or PGM 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 Fl is thus emitted during each active phase until it reaches an object O, 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 Fl, reflected by the object O and noise, for example generated by sources of stray light such as urban lighting, car lighting, or even the sun.

[0069] As shown in [Fig. 1], the receiving module 3 includes an optical unit 31, downstream of which are provided a plurality of elementary acquisition modules 32. The receiving module 3 also includes 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 resolution of approximately 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 demodulation unit 33, which can then extract 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 T p , then determine by thresholding with respect to a value determined from the peak power P p whether this quantity of photons corresponds to a pulse of the light beam Fl or not, and therefore to a bit with a value of "1" or 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 Fl, 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 T of this time of flight of the light beam Fl between the object O 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 O from the vehicle.

[0079] The first light beam Fl performs a direction indicator function and is emitted only during the active phases of this function. Therefore, system 1 is unable to implement a telemetry function during the inactive phases of the flashing photometric function, which can hinder the performance of advanced functions, such as tracking the object O during its movement or the movement of the vehicle, particularly if the relative speed of the object O and the vehicle is high.

[0080] To ensure the continuity of this telemetry function, when the first light beam Fl is deactivated during an inactive phase of the flashing photometric function, the light system 1 implements another telemetry method using the light module 21, which then emits, during this inactive phase, a second modulated light beam Fl'. Figure 4 represents a telemetry method implemented by the light system 1 using the light module 21 during an inactive phase, and Figure 5 shows a control signal Sseq obtained using the methods of Figures 2 and 4 over several cycles of the photometric function.

[0081] In a first step, initialized at the beginning of an inactive phase, the computing unit 4 generates a second modulating data sequence Seq2b exhibiting a duty cycle significantly lower than the duty cycle of the first modulating sequence Seq2a.

[0082] In the example described, the second modulating data sequence Seq2b may have a duty cycle of 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.

[0083] In a second step, a light beam Fl' is emitted by the light module 21 during the inactive phase, the modulation unit 22 modulating this light beam Fl', based on 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.

[0084] In other words, the second light beam Fl' emitted under the control of the modulated signal Sseqb consists of a single light pulse corresponding to the bit value "1" of the modulating sequence Seq2a. The peak power P p Since this pulse is identical to the peak power of the pulses of the first light beam Fl, the low duty cycle of the second modulating sequence Seq2b allows for a significant reduction in the average power of the second light beam Fl'.

[0085] This low average power of the second light beam Fl' makes it practically imperceptible during the inactive phase, and maintains a practically off appearance of the second light module 21, which makes it possible to satisfy the regulatory requirements of the photometric function performed by the first light beam Fl, this function remaining flashing with cycles of active and inactive phases.

[0086] On the other hand, the light pulse contained in this second light beam Fl' remains capable of reaching the object O to be reflected back to the receiving module 3, so that the system 1 can continue the telemetry function during an inactive phase.

[0087] It should be noted that the second data sequence Seq2b is transmitted periodically during the inactive phase to the modulation unit 22 so that the second light beam Fl' is composed, for the same inactive phase, 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.

[0088] 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 within this received light beam F2. The processing unit can directly estimate a time of flight T separating the emission of said light pulse from the second light beam Fl', and the reception of said light pulse detected by the receiving module 3.

[0089] 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 light module 21 during the same inactive phase. In a fifth step, the computing unit 4 generates a histogram H of the different flight times thus determined.

[0090] In a sixth step, the computing unit 4 can thus detect the presence of one or more objects O 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) O from the vehicle from the selected flight times.

[0091] As shown in [Fig. 5], the light module therefore emits, cyclically, a light beam Fl during the active phases, under the control of the modulated signal Sseqa, and a light beam Fl' during the inactive phases, under the control of the modulated signal Sseqb, the sequences of the modulated signals Sseqa and Sseqb thus forming a global modulated signal Sseq.

[0092] As an alternative to the telemetry function just described in relation to [Fig. 4], the second light beam Fl' 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 Seqla. The processing unit 4 can then implement the same steps of the process in [Fig. 2] to perform the telemetry function during the inactive phases of the light module 21.

[0093] The embodiment just described provides that the same module 21 emits the first light beam Fl during active phases and the second light beam Fl' during inactive phases. In another, undescribed embodiment, the second light beam Fl' emitted during inactive phases may be provided by another light module, normally intended for another photometric function, for example a daytime running light, and possibly also for a rangefinding function.

[0094] 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 flashing photometric function and a rangefinding function from visible light, and which enables the detection of an object even during inactive phases of this flashing function. These objectives are achieved, in particular, by also performing a rangefinding function during the inactive phases through modulation of a second light beam emitted during these inactive phases with a sufficiently low duty cycle so that this second modulated light beam does not interfere with the photometric function performed by the first beam of light.

[0095] 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 any technically feasible combination thereof. Specifically, 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, including, in particular, dipped beam lighting functions or position light signaling functions. Furthermore, it may be possible to use other methods for 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 light module (21) capable of emitting a light beam (Fl, Fl') whose spectrum has at least one portion in the visible spectrum, and a modulation unit (22) arranged to control the light module for the production, from said emitted light beam, of a flashing photometric function comprising a sequence of successive cycles each composed of an active phase followed by an inactive phase, the modulation unit being capable of receiving a data sequence, called modulating, (Seq2a, Seq2b) and arranged to modulate said emitted light beam 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 (Fl) by the light module (21) during each active phase and in that the calculation unit 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 (Fl') by the light module (21) during each inactive phase;and in that the calculation unit is arranged to determine a flight time (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 (3), 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 light module (21) comprises a light source (23), the modulation unit (22) being arranged to control said light source for the emission of the first modulated light beam (Fl) by the light module during each active phase and to control said light source (23) for the emission of the second modulated light beam (Fl') by the light module during each inactive phase.

3. Lighting system according to claim 1, characterized in that the light module (21) comprises a first light source (23) and a second light source, the modulation unit (22) being arranged to control said first light source for the emission of the first modulated light beam (Fl) by the light module during each active phase and for controlling said second light source for the emission of the second modulated light beam (Fl') by the light module during each inactive phase.

4. Lighting system (1) according to one of the preceding claims, 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%.

5. 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 (Fl') comprises a single light pulse, and in that, the calculation unit being able to receive an electrical signal (Sel) converted by the photodetector from a light beam (F2) received by the reception module (3), 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 (T) separating the emission of said light pulse from the second light beam, from the reception of said light pulse detected by the reception module (3).

6. 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 (Seq3), called demodulated, from an electrical signal (Sel) converted by this photodetector; and in that, the calculation unit (4) 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 (Fl) emitted, from the reception of said received light beam, from the values ​​of the correlation function.

7. Lighting system (1) according to one of the preceding claims, characterized in that the calculation unit (4) is arranged to generate and transmit the first modulating data sequence (Seq2a) to the modulation unit (22) for the emission of a first modulated light beam (Fl) by the light module (21) during each active phase, in that the calculation unit is arranged to estimate a distance (d) separating the vehicle from an object (O) in the environment of the vehicle from the determination of a flight time (T) separating the emission of the first modulated light beam from the reception of a light beam (F2) received by the reception module (3), in that the calculation unit is arranged to estimate a relative movement speed of the object with respect to the vehicle from said estimated distance, and in that the calculation unit is arranged to, when said estimated relative speed is greater than a given threshold speed, generate and transmit said second modulating data sequence (Seq2b) to the modulation unit for the emission of a second modulated light beam (Fl') by the light module during each inactive phase.

8. 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.

9. Lighting system (1) according to the preceding claim, in which the light module (21) is arranged so that the first light beam (Fl) participates, totally or partially, in the realization of a first predetermined regulatory photometric function.

10. Lighting system (1) according to the preceding claim, in which the lighting module (21) is arranged so that the first light beam (F1) participates, totally or partially, in the realization of a first signaling function of the “direction indicator” type.

Images