System for the detection of a motor vehicle, comprising a module for emitting and a module for receiving a light beam
Patent Information
- Application Number
- EP2023836531
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2023-10-06
- Filing Date
- 2023-12-22
- Publication Date
- 2025-10-29
Smart Images
Figure 1.1
Abstract
Description
Description Title of the invention: Motor vehicle detection system comprising a transmission module and a reception module for a light beam
[0001] The invention relates to the field of automotive lighting and functions for detecting an object by a motor vehicle and estimating the distance separating this object from the vehicle. More specifically, the invention relates to a lighting system of a motor vehicle capable of implementing telemetry functions by means of the light that it emits.
[0002] It is known, in the automotive field, to use a pulsed light beam emitted by a light module of a lighting system of a motor vehicle to perform a given photometric function.
[0003] Conventionally, the light source enabling the emission of this light beam is controlled by a pulse width modulated electrical signal, or PWM (from the English "Pulse Width Modulation"). The light source is thus periodically activated and deactivated by this PWM signal, so that the emitted light beam is composed of light pulses succeeding one another with a frequency high enough that the human eye can no longer distinguish them. The intensity of the emitted light beam is a function of the duty cycle of this PWM signal, so that it is possible to control it by adjusting this duty cycle and therefore to perform a photometric function.
[0004] Beyond the realization of one or more photometric functions, such as a daytime running light or dipped-beam lighting, various functions can be implemented by this type of light module. For example, the light source of the light module can be controlled so that the pulses of the emitted light beam carry a data sequence. The lighting system can thus be equipped with a reception module in order to receive the emitted light beam, after reflection on an object in the vicinity of the vehicle. A computing unit of the motor vehicle can then, after detecting the data sequence in the received light beam, determine the time of flight of the emitted light beam and therefore evaluate the distance separating the vehicle from the object.
[0005] In this way, the light beam can retain its original function, namely performing a photometric function, while allowing the lighting system to implement a telemetry function, which can be particularly advantageous, for example, for driving assistance functions or in the context of autonomous or semi-autonomous driving.
[0006] However, this type of system has a disadvantage when the light module must perform different photometric functions. Indeed, certain functions can be performed through the same output surface of a light module, in order to maintain a uniform lit appearance for these two functions and thus give the motor vehicle a light signature. This is the case, for example, for the “daytime running lamp” or DRL (from the English Daytime Running Lamp) and “position light” functions, or even for the “brake light” and “tail light” functions. These photometric functions are defined by regulation and have significantly different light intensities. For example, the “daytime running light” function has a light intensity ten times greater than that of the “position light” function. Thus, in a conventional manner, the electrical power supplied to the light source of the light module is significantly reduced in order to switch from one of these functions to the other.
[0007] However, when the light module also performs a telemetry function, this solution is not feasible. Reducing the electrical power to perform the weakest light function would make the system unsuitable for detecting objects in the far field.
[0008] There is thus a need for a lighting system for a motor vehicle, comprising a lighting module capable of performing both two distinct photometric functions and a telemetry function, the performance of the telemetry function remaining substantially constant regardless of the photometric function performed.
[0009] The present invention is placed in this context, and aims to meet this need.
[0010] For these purposes, the subject of the invention is a lighting system of a motor vehicle, comprising: a. an emission module comprising a light module capable of emitting a light beam whose spectrum has at least one portion in the visible spectrum, and a modulation unit capable of receiving a data sequence, called modulating, and arranged to modulate said light beam emitted from the received data sequence; b. a reception module capable of receiving a light beam, in which the reception module comprises an elementary acquisition module comprising a photodetector capable of converting a light signal that it receives into an electrical signal.
[0011] The system according to the invention is characterized in that it comprises a calculation unit capable of receiving a first instruction to transmit a first given photometric function and arranged to, upon receipt of the first instruction, 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 transmission of a first light beam modulated by the light module, in that the calculation unit is capable of receiving a second instruction to transmit a second given photometric function and in that the calculation unit is arranged to, upon receipt of the second instruction,generating a second modulating data sequence having a second duty cycle distinct from the first duty cycle and for transmitting said second modulating data sequence to the modulation unit for the emission of a second light beam modulated by the light module.,
[0012] It is thus understood that the invention proposes, when a first photometric function is required, to modulate a light beam emitted by the light module using a first data sequence. The first modulated light beam thus performs the first photometric function. The resulting light beam may for example be a pulsed beam, each pulse corresponding to one or more consecutive high values of the first modulating sequence and the interval separating two consecutive pulses corresponding to one or more consecutive low values of the first modulating sequence. Each pulse of the modulated light beam is emitted with a peak light power, so that the average light power of the first modulated light beam emitted, necessary to perform the photometric function, is thus defined by the peak light power and the duty cycle of the modulating data sequence.The modulating sequence being generated cyclically, the first modulated light beam emitted will periodically contain this sequence while continuously performing the photometric function. The computing unit can thus detect, from the electrical signal converted by the photodetector, the presence of this modulating sequence in a beam received by the receiving module and thus detect the presence of an object in the environment of the vehicle and estimate its distance from the vehicle.
[0013] The invention further proposes, when another photometric function is required, to modulate the light beam emitted by the light module with another data sequence of distinct duty cycle. The second modulated light beam thus performs the second photometric function. However, taking into account the change in duty cycle, the average power of the second modulated beam is adapted to correspond to that required for the performance of this second function, without the peak light power having to be modified. Therefore, the range of the telemetry function can remain unchanged, even when the second photometric function requires a lower light intensity than the first.
[0014] In the present invention, the duty cycle of a data sequence is understood to mean the ratio between the number of high values and the total length of the data sequence. In the case where the data sequence is a binary sequence, the duty cycle therefore corresponds to the ratio between the number of bits with the value "1" in the binary sequence and the total number of bits in this sequence.
[0015] Preferably, the calculation unit is arranged to generate said first modulating data sequence and said second modulating data sequence, from the same initial sequence of pseudo-random binary type, in particular of pseudo-random binary type of maximum size.
[0016] A pseudo-random binary sequence, or PRBS, is a data sequence composed of high values, namely "1s", and low values, namely "0s". This type of sequence has particularly interesting properties. Indeed, its autocorrelation function is maximum for a zero time lag, that is to say when the sequence is compared to itself, and has a value significantly lower than this maximum for all other time shifts, 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, which produces a periodic recurring sequence whose pattern is a pseudo-random binary sequence.
[0017] Given the autocorrelation properties of pseudo-random binary sequences, the computing unit can estimate values of a correlation function between a modulating sequence and a demodulated sequence extracted from a light beam received by the receiving module. The correlation function will be maximum for the time shift value corresponding to the time of flight of the modulated light beam emitted, reflected and then received, even in the event of significant noise. Consequently, the computing unit can identify this time shift value associated with the maximum value of the correlation function with significant precision and deduce therefrom the distance separating the object on which the beam was reflected and the motor vehicle. Furthermore, given the cross-correlation properties, it thus appears unlikely that the reception of a modulated light beam emitted by an equivalent system of another motor vehicle will result in the detection of a false positive.Finally, we understand that the detection is carried out not on a single pulse but on a complete data sequence, so that the signal-to-noise ratio of the system is improved.
[0018] Advantageously, the modulation unit is arranged to control the light module so that the first and second light beams have the same peak light power and in that the calculation unit is arranged so that the first and second modulating data sequences are binary sequences and so that the first modulating data sequence has a number of bits of value "0" distinct from the number of bits of value "0" of the second modulating data sequence. According to this characteristic, the increase in the number of bits of value "0" in one of the modulating data sequences, reflecting a reduction in its duty cycle, therefore makes it possible to increase the number or duration of the intervals separating consecutive pulses of the corresponding modulated light beam. The average light power of this beam is thus reduced.Conversely, reducing the number of bits with the value “0”, reflecting an increase in the duty cycle, makes it possible to increase the number or duration of the pulses of the modulated light beam and therefore to increase its average light power.
[0019] Advantageously, the modulation unit is arranged to generate a pulse width modulated control signal, to modulate said control signal from the modulating data sequence that it receives and to control the emission of said beam. light by the light module from the modulated control signal. For example, the modulation unit may be arranged to convert the modulating data sequence that it receives into a modulating signal and to modulate, for example in amplitude, frequency or phase, the control signal with this modulating signal. In particular, the modulation unit may control the light module so that said modulated light beam is emitted only for high values of said modulating data sequence received from the calculation unit and so that the modulated light beam is emitted according to said peak light power value.It is thus understood that each pulse of the modulated light beam is emitted with said peak light power and that the average light power of the first or second modulated light beam emitted, necessary for the realization of the first or second photometric function, is thus defined by the peak light power, the duty cycle of the first or second modulating data sequence and by the control signal.
[0020] In one embodiment of the invention, the calculation unit is arranged so that the number of bits of the first modulating data sequence is identical to the number of bits of the second modulating data sequence. Therefore, the acquisition time of a demodulated data sequence by the reception module, so that the calculation unit can detect the presence of a modulating sequence in a beam received by the reception module, remains constant regardless of the photometric function performed. This characteristic thus makes it possible to simplify the design of the calculation unit.
[0021] In one embodiment of the invention, the calculation unit is arranged to generate a first initial sequence of pseudo-random binary type and a second initial sequence by cyclic sampling of the first initial sequence. Where appropriate, the calculation unit is arranged to generate the first modulating data sequence from a combination according to an “exclusive or” function of the first initial sequence and a circular shift of the second initial sequence according to a first shift, and to generate the second modulating data sequence from a combination according to an “exclusive or” function of the first initial sequence and a circular shift of the second initial sequence according to a second shift distinct from the first shift.The first and second modulating sequences thus generated are so-called “Kasami” sequences belonging to the same set of Kasami sequences, comprising a large number of sequences whose cross-correlations are minimal and whose number of “0”s varies from one sequence to another. The choice of an offset value for the second initial sequence thus makes it possible to control the number of “0”s in the modulating sequence, it being understood that the more the offset value increases, the more the number of “0”s decreases.
[0022] Advantageously, the calculation unit is arranged so that the first modulating data sequence has a first duty cycle greater than the duty cycle of the second modulating data sequence. In particular, it may be conceived that the duty cycle of the second modulating data sequence is reduced by a factor of ten with respect to the first duty cycle. The first modulated light beam can thus perform a photometric function whose luminous intensity is significantly greater than that of the photometric function performed by the second modulated light beam.
[0023] In one embodiment of the invention, the light module comprises a light source, the modulation unit being arranged to, upon receipt of the first modulating data sequence, drive said light source for the emission of the first light beam modulated by the light module; and to, upon receipt of the second modulating data sequence, drive said light source for the emission of the second light beam modulated by the light module. In other words, it is the same light source, and possibly the same optical unit, which is used to selectively emit the first and second modulated light beams.
[0024] In one embodiment of the invention, the light module is capable of emitting a first light beam whose spectrum has a wavelength in the visible range, in particular between 400 nm and 500 nm. Advantageously, the light source comprises 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. Where appropriate, the modulation unit may be arranged to control the light source of the light module, and in particular a power supply supplied to this light source, to modulate the light beam.
[0025] The semiconductor may, for example, be a gallium nitride, or GaN, capable of emitting, by electroluminescence and in response to an electric current passing through it, rays of blue light. The photoluminescent element may, for example, be in the form of a resin comprising a cerium-doped yttrium aluminum garnet, or CE:YAG, capable of absorbing blue light and, by photoluminescence and in response to the excitation produced by this light, emitting rays of yellow light. The photoluminescent element is arranged on the generator so that part of the blue light rays excites this element so that it emits, by photoluminescence, rays of orange light. The other part of the blue light rays passes through this element. Thus, the light source emits simultaneously, when it is electrically powered, rays of blue and yellow light, in proportions such that the light thus formed appears white to the human eye.
[0026] The light source could therefore be a laser type source, a light-emitting diode, a vertical-cavity surface-emitting laser diode, also called VCSEL (from the English “Vertical-Cavity Surface-Emitting Laser”) or even a diode superluminescent or SLED (from the English “Superluminescent diode”).
[0027] Advantageously, the light module may comprise an optical unit arranged to project the light rays emitted by the light source to form said light beam.
[0028] In one embodiment of the invention, the reception module comprises a plurality of elementary acquisition modules each comprising at least one photodetector capable of converting a light signal that it receives into an electrical signal. Advantageously, the plurality of elementary acquisition modules is arranged in a matrix. For example, all of the photodetectors of the same elementary acquisition module can form a sensor, for example a single electronic component. For example, each photodetector, or each plurality of photodetectors, may have a width and / or a length of less than about ten micrometers, which makes it possible to obtain a reception field of the elementary acquisition module of at most 0.1° and therefore to increase the spatial resolution of the reception module.
[0029] Advantageously, the photodetector of the or each elementary acquisition module is a single-photon avalanche photodiode. This type of photodetector is also known as SPAD, from the English "Single-Photon Avalanche Diode". The set of avalanche photodiodes can thus form a silicon photomultiplier or SiPM (from the English "Silicon PhotoMultiplier"). This type of photodetector makes it possible to detect the incidence of a single photon with a significant gain, for example of the order of 106, and therefore to compensate for the degradations of the signal-to-noise ratio due to external conditions.
[0030] According to an exemplary embodiment of the invention, the reception module may comprise an optical unit arranged in front of the elementary acquisition modules.
[0031] In one embodiment of the invention, the calculation unit is arranged to determine a flight time separating the emission of the first or second modulated light beam emitted, from the reception of a light beam received by the reception module, from an electrical signal converted by the photodetector from said received light beam.
[0032] Advantageously, the light system comprises a demodulation unit connected to the photodetector and arranged to extract a data sequence, called demodulated, from an electrical signal converted by this photodetector. Where appropriate, the calculation unit is able to receive a data sequence demodulated by the demodulation unit from an electrical signal converted by the photodetector from a light beam received by the reception module and the calculation unit is arranged to estimate values of a correlation function between said demodulated data sequence and said first or second modulating data sequence and to determine a time of flight separating the emission of said first or said second modulated light beam emitted, from the reception of said received light beam, from the values of the correlation function.
[0033] Each value of the correlation function estimated by the calculation unit is associated with a value of a time shift of the modulating data sequence, or of the demodulated data sequence, used to estimate this value of the correlation function. The correlation function between this demodulated data sequence and the modulating data sequence is therefore a function of the autocorrelation of this modulating data sequence.
[0034] It is thus possible to detect the presence of this modulating data sequence in the received light beam, after reflection on an object in the vehicle's environment and thus detect the presence of this object as well as estimate its distance from the vehicle.
[0035] Preferably, the calculation unit is arranged to determine the value of a peak of said correlation function, to compare said peak value with a predetermined threshold value and to detect the presence of said modulating data sequence in the demodulated data sequence as a function of said comparison. The calculation unit may for example conclude that said modulating data sequence is present in said demodulated data sequence only if said peak value is greater than the predetermined threshold value.
[0036] For example, the or each elementary acquisition module is capable of generating an elementary detection signal as a function of the electrical signal(s) converted by the photodetector(s) of the elementary acquisition module; and each elementary acquisition module being arranged to compare said elementary detection signal with a threshold value associated with said elementary acquisition module and to generate a data sequence, called demodulated, from said comparison.
[0037] In particular, it may be conceived that each elementary acquisition module comprises a comparator arranged to compare said elementary detection signal with said threshold value associated with this elementary acquisition module and to generate said demodulated data sequence as a function of said comparison. The comparator thus forms a unit for demodulating the light beam received by the reception module, capable of extracting a data sequence, called demodulated, from the electrical signals converted by the photodetectors. As a variant, it may be provided to replace the comparator with active circuits.
[0038] In one embodiment of the invention, each elementary acquisition module comprises a plurality of photodetectors and at least one electronic component arranged to generate said elementary detection signal as a function of the sum of the electrical signals converted by said photodetectors.
[0039] In an exemplary embodiment of the invention, the transmission module is arranged in a front headlight of the motor vehicle. Preferably, the reception module and the transmission module are arranged in the same front headlight of the vehicle.
[0040] Advantageously, the light module is arranged so that the first modulated light beam participates, totally or partially, in the realization of a first regulatory photometric function corresponding to the first instruction and so that the second modulated light beam participates, totally or partially, in the realization of a second regulatory photometric function corresponding to the second instruction. Preferably, the luminous intensity of the second regulatory photometric function may be significantly lower than that of the first regulatory photometric function.
[0041] Advantageously still, the light module is arranged so that the first modulated light beam participates, totally or partially, in the realization of a first signaling function of the “daytime running light” type and so the second modulated light beam participates, totally or partially, in the realization of a second signaling function of the “position light” type.
[0042] The invention also relates to a method for detecting an obstacle located in the environment of a motor vehicle and for estimating the distance separating this object from the vehicle, the method being implemented by a lighting system according to the invention.
[0043] The present invention is now described using examples which are purely illustrative and in no way limitative of the scope of the invention, and from the appended drawings, drawings in which the various figures represent:
[0044] [Fig.l] represents, schematically and partially, a view of a telemetry system of a motor vehicle according to an exemplary embodiment of the invention.
[0045] [Fig. 2] represents, schematically and partially, an example of operation of the system of [Fig.l] during the implementation of a telemetry method;
[0046] [Fig. 3] represents, schematically and partially, different sequences of data generated by the computing unit of the telemetry system of [Fig. 1] during its operation.
[0047] In the following description, elements which are identical in structure or function and which appear in different figures retain, unless otherwise specified, the same references. Of course, various other modifications may be made to the invention within the scope of the appended claims.
[0048] [Fig. 1] shows a system 1 of a motor vehicle according to an exemplary embodiment of the invention. The telemetry system 1 of a vehicle comprises a transmission module 2 capable of transmitting a light beam F1, a reception module 3 intended to receive a light beam F2, and a calculation unit 4.
[0049] In the example described, the transmission module 2 and the reception module 3 are arranged in the same front headlight of the motor vehicle. It may be provided that the modules 2 and 3 are arranged in different locations of the motor vehicle, without departing from the scope of the present invention.
[0050] The emission module 2 comprises a light module 21 capable of emitting a light beam Fl, and a modulation unit 22 capable of receiving a modulating data sequence Seq_m and arranged to modulate the light beam Fl emitted from said modulating sequence Seq_m.
[0051] The light module 21 is arranged so that the light beam Fl that it emits has an electromagnetic spectrum of which at least a portion is located in the visible spectrum. Preferably, the spectrum of this light beam Fl has an intensity peak, or line, in the blue at 450 nm. It will be noted that it is possible for the spectrum to have other intensity peaks, in the visible and / or in the infrared.
[0052] To the extent that the light beam Fl is composed, partially or totally, of white light, it is possible to use this light beam to participate, partially or totally, in the realization of several photometric functions, in particular regulatory, predetermined, as will be described later. In this case, the light module 21 may comprise an optical unit arranged to shape this light beam Fl so that its photometric distribution satisfies the requirements of one or other of these functions.
[0053] In addition to this photometric function, the light beam Fl allows the system 1 to perform functions of detecting and evaluating the position of an obstacle on the road and / or communicating with another vehicle or with road infrastructure.
[0054] For these purposes, the modulation unit 22 is arranged to modulate the light beam Fl emitted by the light module 21, from the sequence of modulating data Seq_m that it receives, for example by controlling the electrical power supplied to the light source of the light module.
[0055] It will thus be possible to provide that the modulation unit 22 comprises a generator of a pulse width modulated control signal. This control signal makes it possible to control a switching power supply (not shown) of the light source of the light module 21. Conventionally, the duty cycle of this control signal, set by the modulation unit 22, thus makes it possible to control the average electrical power supplied to the light source, and therefore to control the light intensity of the light beam F1, so as to satisfy the requirements of the photometric function that it performs.
[0056] In the example described, the modulation unit 22 is arranged to convert the data sequence Seq_m into a modulating signal and to modulate the initial control signal using this modulating signal. It will be noted that several types of modulation can be used indifferently within the scope of the present invention, and in particular an on-off keying modulation (OOK), a pulse code modulation (PGM), a pulse amplitude modulation (PAM), a pulse width modulation (PWM) or a pulse position modulation (PPM).
[0057] The light beam Fl thus emitted is composed of a train of light pulses succeeding one another with a sufficiently high frequency, for example greater than 30 MHz, in particular between 50 MHz and 100 MHz, so that the human eye cannot distinguish them. more. Furthermore, the amplitude, width and / or position of each pulse with respect to the period allows the light beam Fl to carry the data sequence Seq_m.
[0058] If an object is present in the environment of the motor vehicle, it can reflect this light beam Fl towards the receiving module 3, which thus receives a light beam F2.
[0059] This reception module 3 comprises a plurality of elementary acquisition modules 32i,j. Each elementary acquisition module 32i,j comprises several photodetectors 32a k,l each capable of converting a light signal that it receives into an electrical signal Sel k, I. Each elementary acquisition module 32i,j further comprises a demodulation unit 34, comprising a comparator, to the input of which all the outputs of the photodetectors 32ak, I are connected in parallel. The comparator thus receives an elementary detection signal Sdei,j formed from the sum of the electrical signals Sel k, I from these photodetectors 32a k, I. The comparator is arranged to compare this elementary detection signal Sdei,j with a given threshold value, the comparison giving a high value, or a “1” when the elementary detection signal is greater than the threshold value, and a low value, or a “0”, when the elementary detection signal is less than the threshold value.The demodulation unit 34 is thus arranged to generate a demodulated binary sequence Seq_di,j, which it transmits to the calculation unit 4. It may be provided, as a variant, to replace the comparator of the demodulation unit 34 with active circuits, the sequence of demodulated data being in this case directly a digital sequence formed of “1” and “0”.
[0060] In the example described, the photodetectors 32ak,l are identical and are each formed by a single-photon avalanche photodiode, or SPAD, these photodiodes and the demodulation unit 34 being integrated into a silicon photomultiplier, or SiPM. It should be noted that the dimensions of the photodetectors are of the order of a micrometer. The assembly thus forms a sensor whose spatial reception resolution is of the order of 1°, or even 0.1°, and whose detection capabilities, due to the use of avalanche photodiodes, are particularly high, even in the case of degraded acquisition conditions.
[0061] The calculation unit 4 is capable of receiving the demodulated binary sequences Seq_di,j, generated by the elementary acquisition modules 32i,j and of detecting in each demodulated binary sequence Seq_di,j„ the presence of the modulating data sequence Seq_m. The demodulation units 34 thus make it possible to reduce the quantity of data to be manipulated by the calculation unit, thus operating a compression of the elementary detection signals Sdei.
[0062] For these purposes, the calculation unit 4 is thus arranged to estimate values of a correlation function Fcorri between each demodulated binary sequence Seq_di,j, and said modulating data sequence Seq_m, and to detect in this demodulated binary sequence Seq_di,j, the presence of the modulating data sequence Seq_m from these values of the correlation function Fcorri. In the event of detection, it can then determine a flight time T separating the emission of said emitted modulated light beam Fl from the reception of said received light beam F2.
[0063] The computing unit 4 can thus perform functions of detecting and evaluating the position of an object on the road, as will be described in connection with [Fig. 2] which represents a telemetry method implemented by the lighting system 1.
[0064] As indicated above, the light module 21 is capable of selectively performing different functions through the same output surface, such as a first “daytime running lamp” function, or DRL (from the English Daytime Running Lamp) and a second “position light” function.
[0065] In order to be able to activate one or other of these functions, the calculation unit 4 receives, in a step E0, an instruction to transmit one or other of these first and second photometric functions.
[0066] This instruction could, for example, come from a central computer of the motor vehicle (not shown), and be determined by the central computer, for example, based on traffic parameters of the motor vehicle, information from various sensors such as a camera filming the road, an angle sensor on the steering wheel, or a navigation system.
[0067] Depending on the instruction received, the computing unit determines a duty cycle cl or T2 according to the photometric function indicated by this instruction, and generates either a first modulating data sequence Seq_ml or a second modulating data sequence Seq_m2.
[0068] For these purposes, the calculation unit generates, in a step E0', an initial pseudo-random binary sequence SeqO of maximum size.
[0069] Then, in a step E1, the calculation unit generates, periodically: a. either said first modulating data sequence Seq_ml from the initial sequence Seq0, the first modulating data sequence having the first duty cycle cl; b. or said second modulating data sequence Seq_m2 from the initial sequence Seq0, the second modulating data sequence having the second duty cycle T2.
[0070] It will be noted that, whatever the duty cycle cl or T2, the number of bits of the first modulating data sequence Seq_ml is identical to the number of bits of the second modulating data sequence Seq_m2. Furthermore, taking into account the photometric functions that the light module 21 must perform, the value of the first duty cycle cl is greater than the value of the second duty cycle T2, in particular by a factor of 10. In other words, the number of bits with value “0” of the first sequence Seq_ml is greater than the number of bits with value “0” of the second sequence Seq_m2.
[0071] Computing unit 4 transmits the modulating data sequence Seq_ml or Seq_m2 thus generated at the modulation unit 22 of the emission module 2 for the emission of a light beam Fl or Fl' by the emission module 2.
[0072] In a second step E2, the modulation unit 22 modulates the light beam emitted by the light module 21 from this data sequence Seq_ml or Seq_m2 to obtain a modulated light beam Fl or Fl'.
[0073] It will be noted that in the example described, each light pulse of the light beam Fl or Fl' emitted by the light module 21 corresponds to a bit of value "1" of the modulating sequence Seq_ml or Seq_m2. The average power of a portion of the light beam Fl / Fl' containing the sequence Seq_ml or Seq_m2 is thus defined by the number of bits of value "1" of this sequence Seq_ml or Seq_m2 with respect to the total number of bits of this sequence, by the duration of the pulses and by the peak power Pp of these pulses.
[0074] Since the peak light power Pp is the same for either the Seq_ml or Seq_m2 data sequences, the average power of the light beam Fl modulated by the first Seq_ml sequence is therefore significantly higher than that of the light beam Fl' modulated by the second Seq_m2 sequence. Indeed, this first beam Fl contains more light pulses and / or longer light pulses than the second beam Fl', taking into account the relative value of the duty cycles cl and T2. The light beam Fl can thus perform a significantly intense photometric function, such as a daytime running light, while the light beam Fl' can perform a weaker photometric function, such as a position light, without the peak light power Pp of the pulses being impacted.
[0075] The light beam Fl / Fl' is thus emitted until it reaches an object O, located in the vehicle's environment, which reflects it towards the reception module 3.
[0076] Depending on the angular position of the object O, the light beam F2 received by the reception module 3 is thus concentrated on one of the elementary acquisition modules 32ij.
[0077] When the sunlight conditions in the vicinity of the vehicle are particularly strong, sunlight is thus added to the light beam F2 received by the receiving module 3. The light beam F2 received by the receiving module 3 is thus composed of a part of the light beam Fl / Fl' reflected by the object O and of noise, for example generated by sources of stray light such as urban lighting, automobile lighting, or even the sun.
[0078] In a third step E3, each of the elementary acquisition modules 32i thus extracts, using its demodulation unit 34, a demodulated binary sequence Seq_di which it transmits to the calculation unit 4.
[0079] For each demodulated binary sequence Seq_dij that it receives, the calculation unit 4 estimates, in a fourth step E4, values of a correlation function Fcorrij between the modulating sequence Seq_ml or Seq_m2 which was used to modulate the emitted light beam Fl / Fl' and this demodulated binary sequence Seq_di.
[0080] It should be noted that, to the extent that these modulating sequences Seq_ml or Seq_m2 contain an identical number of bits, the acquisition time of a demodulated data sequence remains constant regardless of the photometric function performed by the emitted light beam Fl / Fl'.
[0081] The calculation unit 4 thus evaluates, for a plurality of time shift values, the value of the cross-correlation, by means of a cyclic convolution product, between each demodulated binary sequence Seq_di and the modulating sequence Seq_ml or Seq_m2 delayed according to each of the time shift values.
[0082] Taking into account the autocorrelation and cross-correlation properties of the modulating sequence, the correlation function Fcorry will thus be maximum for a time shift value corresponding to the time of flight of the light beam Fl, separating the instant when it is emitted by the emission module 2 and the instant when it is received by an elementary acquisition module 32i of the reception module 3, the modulating sequence Seq_ml or Seq_m2 delayed by this value thus corresponding substantially to the demodulated binary sequence Seq_dij to within noise.
[0083] In a fifth step E5, the calculation unit 4 identifies the maximum value Fcorr_max of each correlation function Fcornj associated with each elementary acquisition module 32ij and compares it to a threshold value Vs.
[0084] In the case where this maximum value Fcorr_max is greater than the threshold value Vs, the modulating sequence Seq_ml or Seq_m2 is considered to be detected by the calculation unit 4 in the demodulated binary sequence Seq_di from the elementary acquisition module 32ij associated with this correlation function Fcorrij. An object O is therefore detected in the angular range, or the pixel, monitored by this elementary acquisition module 32ij and the calculation unit 4 can then estimate, in a sixth step E6, the value T of the time of flight of the emitted light beam Fl / Fl' between the object O and the vehicle, associated with this maximum value, as well as the distance d separating the object O from the vehicle.
[0085] In connection with [Fig. 3], we will now describe an example of an embodiment of the calculation unit making it possible to generate modulating sequences Seq_ml and Seq_m2, having autocorrelation and intercorrelation properties adapted to the needs of the invention and whose duty cycle can be controlled.
[0086] The calculation unit 4 first generates a first initial pseudo-random binary sequence of maximum size Seq0, for example by means of a linear feedback shift register.
[0087] The calculation unit 4 then generates a second initial sequence Seq0' by cyclic sampling of the first initial sequence. Each bit of the second initial sequence Seq0' thus takes the value of a bit of the first initial sequence Seq0 whose rank corresponds to the rank of the bit of the second initial sequence that one seeks to calculate, multiplied by a coefficient calculated as a function of the length of the first initial sequence Seq0, modulo this length of the first initial sequence Seq0.
[0088] This second initial sequence SeqO' thus undergoes a circular shift of a value Al for the calculation of the first modulating sequence Seq_ml and of a value A2 for the calculation of the second modulating sequence Seq_m2. The value A2 will be greater than the value Al so as to ensure that the number of "0"s in the second modulating sequence Seq_m2 is greater than the number of "0"s in the first modulating sequence Seq_ml.
[0089] Finally, the calculation unit combines, according to an “exclusive or” function, the first initial sequence SeqO and the circular shift of the second initial sequence SeqO'(A1) to generate the first modulating data sequence Seq_ml, and the first initial sequence SeqO and the circular shift of the second initial sequence SeqO'(A2) to generate the second modulating data sequence Seq_m2. These first and second modulating sequences Seq_ml and Seq_m2 are thus so-called “Kasami” sequences belonging to the same set of Kasami sequences.
[0090] The foregoing description clearly explains how the invention makes it possible to achieve the objectives it has set itself, namely to provide a lighting system comprising a lighting module capable of performing both two distinct photometric functions and a telemetry function, the performance of the telemetry function remaining substantially constant regardless of the photometric function performed. These objectives are achieved in particular by adapting the value of the duty cycle of the data sequence modulating the light beam emitted by the lighting module as a function of the photometric function that the lighting module must perform.
[0091] In any event, the invention cannot be limited to the embodiments specifically described in this document, and extends in particular to any equivalent means and to any technically effective combination of these means. In particular, other configurations of the emission modules may be provided, and in particular an emission module using other types of light source than those described, such as a laser diode, a VCSEL or a SLED or an RGB diode. It may also be possible to provide other photometric functions than those described, and in particular dipped beam type lighting functions or signaling functions such as a brake light or rear light. It may also be possible to provide other methods of generating a modulating sequence than those described.
Claims
Claims
1. Lighting system (1) of a motor vehicle, comprising: a. an emission module (2) comprising a light module (21) capable of emitting a light beam (Fl, Fl') whose spectrum has at least a portion in the visible spectrum, and a modulation unit (22) 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) capable of receiving a first instruction to emit a first given photometric function and arranged to, upon receipt of the first instruction,generating a first modulating data sequence (Seq2a) having a first duty cycle and for transmitting 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), in that the calculation unit is capable of receiving a second instruction for the emission of a second given photometric function and in that the calculation unit is arranged to, upon receipt of the second instruction, generate a second modulating data sequence (Seq2b) having a second duty cycle distinct from the first duty cycle and for transmitting 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).,
2. Lighting system (1) according to the preceding claim, characterized in that the modulation unit is arranged to control the light module so that the first and second light beams have the same peak light power and in that the calculation unit is arranged so that the first and second modulating data sequences are binary sequences and so that the first modulating data sequence has a number of bits of value "0" distinct from the number of bits of value "0" of the second modulating data sequence.
3. Lighting system (1) according to the preceding claim, characterized in that the calculation unit is arranged so that the number of bits of the first modulating data sequence is identical to the number of bits of the second modulating data sequence.
4. Telemetry system (1) according to one of the preceding claims, characterized in that the calculation unit (4) is arranged to generate a first sequence initial pseudo-random binary type sequence and a second initial sequence by cyclic sampling of the first initial sequence, and to generate the first modulating data sequence from a combination according to an "exclusive or" function of the first initial sequence and a circular shift of the second initial sequence according to a first shift, and to generate the second modulating data sequence from a combination according to an "exclusive or" function of the first initial sequence and a circular shift of the second initial sequence according to a second shift distinct from the first shift.
5. Lighting system (1) according to one of the preceding claims, characterized in that the calculation unit (4) is arranged so that the first modulating data sequence (Seq2a) has a first duty cycle greater than the duty cycle of the second modulating data sequence (Seq2b).
6. Lighting system (1) according to one of the preceding claims, characterized in that the light module (21) comprises a light source (23), the modulation unit (22) being arranged to, upon reception of the first modulating data sequence, control said light source for the emission of the first modulated light beam (Fl) by the light module; and to, upon reception of the second modulating data sequence, control said light source (23) for the emission of the second modulated light beam (Fl') by the light module.
7. Lighting system (1) according to one of the preceding claims, characterized 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.
8. Lighting system (1) according to the preceding claim, 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 or second modulating data sequence (Seq2a) and to determine a time of flight (T) separating the emission of said first or said second modulated light beam (Fl) emitted, from the reception of said received light beam, from the values of the correlation function.
9. Lighting system (1) according to one of the preceding claims, characterized in that the emission module (2) is arranged in a front headlight of the motor vehicle.
10. Lighting system (1) according to the preceding claim, in which the lighting module (21) is arranged so that the first modulated light beam (Fl) participates, totally or partially, in the realization of a first regulatory photometric function corresponding to the first instruction and so that the second modulated light beam (Fl) participates, totally or partially, in the realization of a second regulatory photometric function corresponding to the second instruction.
11. Lighting system (1) according to the preceding claim, in which the lighting module (21) is arranged so that the first modulated light beam (Fl) participates, totally or partially, in the realization of a first signaling function of the “daytime running light” type and so the second modulated light beam (Fl) participates, totally or partially, in the realization of a second signaling function of the “position light” type.