A motor vehicle's lighting system comprising a light beam emission module and a temperature sensor

Abstract

The invention relates to a lighting system (1) of a motor vehicle, comprising: an emission module (2) comprising a light module (21) capable of emitting a light beam (F1), and a modulation unit (22) capable of modulating said light beam from a modulating data sequence (Seq_m, Seq_m1, Seq_m2); a control system (4) comprising a generator (41) for generating and transmitting a modulating data sequence (Seq_m, Seq_m1, Seq_m2) to the modulation unit (22) for the emission of a modulated light beam (F1) by the emission module; characterized in that it comprises at least one sensor (23) capable of measuring the temperature (T°) of the emission module, and the control system is arranged to control a parameter (θ, Pp) of the modulation, by the modulation unit (22), of the emitted light beam as a function of the temperature measured by said sensor. Figure to be published with the abbreviation: Fig. 1

Description

Title of the invention: Lighting system for a motor vehicle comprising a light beam emission module and a temperature sensor

[0001] The invention relates to the field of automotive lighting and / or signaling, specifically to the functions of detecting an object by a motor vehicle and estimating the distance between that object and the vehicle. More precisely, the invention relates to a lighting and / or signaling system for a motor vehicle capable of implementing telemetry functions.

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

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

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

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

[0006] However, this type of system based on the emission and reception of a light beam capable of performing both a photometric light function and a telemetry function has disadvantages.

[0007] When the light source of the light module is operating at a normal temperature, for example when its junction temperature is at its nominal value, it can be driven with a normal operating current, in particular in order to benefit from a maximum range of detection operated by the telemetry function.

[0008] However, this temperature can exceed critical thresholds, for example when the light source heats up under various conditions, particularly when the power it emits is too high and / or when the emission duration is too long and / or when the modulation is too rapid. Under these conditions, it is necessary to reduce the operating current to decrease the thermal stress on the light source. This process is known in particular as "derating".

[0009] This decrease in operating current then necessarily leads to a degradation of the telemetry function, particularly in terms of detection range.

[0010] There is therefore a need for a lighting system of a motor vehicle, capable of performing both a given regulatory photometric function and a telemetry function, and in which the performance of the telemetry function remains acceptable in the event of heating of a component of the emission module.

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

[0012] To this end, 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 capable of receiving a data sequence, called modulating, and arranged to modulate said light beam emitted from the received data sequence; b. a control system comprising a generator arranged to generate a modulating data sequence and to transmit said modulating data sequence to the modulation unit for the emission of a light beam modulated by the emission module.

[0013] The system according to the invention is characterized in that it comprises at least one sensor capable of measuring the temperature of all or part of the emission module, and in that the control system is arranged to control a parameter of the modulation, by the modulation unit, of the light beam emitted by the light module as a function of the temperature measured by said sensor.

[0014] It is thus understood that the invention proposes, when a photometric function is required, to modulate a light beam emitted by the light module at using a data sequence, the modulated light beam performs the photometric function. The resulting light beam could, for example, be a pulsed beam, with each pulse corresponding to one or more consecutive high values ​​of the modulating sequence and the interval between two consecutive pulses corresponding to one or more consecutive low values ​​of the modulating sequence. Each pulse of the modulated light beam is emitted with a peak light power, so the average light power of the emitted modulated light beam, 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 by the generator, the emitted modulated light beam will periodically contain this sequence while continuously performing the photometric function.A receiving module can thus receive this modulated light beam emitted after reflection on an object in the vehicle's environment, and a computing unit can thus detect, from a data sequence demodulated from this light beam received by the receiving module, the presence of this modulating sequence in this received beam and thus detect the presence of said object in the vehicle's environment and estimate its distance from the vehicle.

[0015] Furthermore, the modulation performed by the modulation unit defines the average power of the modulated light beam. For example, in the case of modulation from a binary sequence, the average power of the modulated light beam is defined, among other things, by the number of bits with a value of "1" in this binary sequence relative to the total number of bits in this sequence, by the duration of the binary sequence, by the duration of each pulse, and by the peak power of these pulses. The control system can thus control each of these parameters to influence the average power in order to increase it, decrease it, or maintain it constant, so as to allow a reduction in the operating current of the light source of the light module without significantly degrading the performance of the telemetry function.

[0016] In the context of the present invention, the term "modulation parameter" means any parameter influencing the average luminous power of the modulated light beam emitted and thus allowing this average luminous power to be controlled as a function of the temperature measured by the sensor. This parameter may include, in particular, the duty cycle of the modulating data sequence, the density of "1" values ​​in the sequence, the peak luminous power of the pulses in the light beam, the duration of the data sequence, and the duration of each pulse.

[0017] In the context of the present invention, "sensor capable of measuring the temperature of all or part of the emission module" means any element or combination of Electronic and / or software components capable of obtaining a direct or indirect measurement of the temperature of a component of the transmission module. This could be a temperature sensor capable of measuring the temperature of the modulation unit, the temperature of the light module, or even the temperature of the light source itself. It could also be a sensor capable of measuring an electrical parameter of a component of the transmission module that may vary with the temperature of that component or another component, such as thermal resistance, voltage, or activation time.

[0018] In the context of the present invention, "data sequence generator" means one or more electronic and / or software components capable of periodically generating a data sequence, for example composed of high values, namely "1s" in the case of a digital sequence or a "high" voltage in the case of an analog sequence, and low values, namely "0s" in the case of a digital sequence or a "low" voltage in the case of an analog sequence.

[0019] In the present invention, the duty cycle of a data sequence is understood to be 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 that sequence.

[0020] In the context of the present invention, the term "modulation unit" means one or more electronic and / or software components capable of receiving a data sequence and controlling the power supply provided by an electrical power source to the light module according to the received modulating data sequence, in particular so that the modulated light beam is formed by a train of light pulses carrying said received modulating data sequence. This modulation unit may, for example, be a high-frequency driver device.

[0021] In one embodiment of the invention, the light module comprises a light source, the modulation unit being arranged to, upon receiving the modulating data sequence, control said light source for the emission of the light beam modulated by the light module.

[0022] 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 beam elementary light source to obtain said light beam. Where appropriate, the modulation unit can be arranged to control the light source of the light module, and in particular a power supply provided to this light source, to modulate the light beam.

[0023] The semiconductor could, for example, be gallium nitride, or GaN, capable of emitting blue light rays by electroluminescence in response to an electric current passing through it. The photoluminescent element could, for example, be in the form of a resin comprising a cerium-doped yttrium aluminum garnet, or CE:YAG, capable of absorbing blue light and, by photoluminescence in response to the excitation produced by this light, of emitting yellow light rays. The photoluminescent element is arranged on the generator so that a portion of the blue light rays excites this element, causing it to emit orange light rays by photoluminescence. The remaining portion of the blue light rays passes through this element. Thus, when electrically powered, the light source simultaneously emits blue and yellow light rays in proportions such that the light thus formed appears white to the human eye..

[0024] The light source may thus be a laser type source, a light-emitting diode, a vertical-cavity surface-emitting laser diode, also called VCSEL (from the English "Vertical-Cavity Surface-Emitting Laser") or a superluminescent diode or SLED (from the English "Superluminescent diode").

[0025] Advantageously, the light module may include an optical unit arranged to project the light rays emitted by the light source to form said light beam.

[0026] In one embodiment, the control system is arranged to transmit a peak light power setpoint to the modulation unit, and the modulation unit is arranged to modulate said light beam based on the received modulating data sequence so that the emitted light beam consists of a train of light pulses, each having a light power conforming to said peak power setpoint. Advantageously, the control system is arranged to control the value of said peak light power setpoint as a function of the temperature measured by said sensor. This embodiment allows the control system to increase or decrease the average light power of the modulated light beam without affecting the data sequence.

[0027] In another alternative or cumulative embodiment of the invention, the control system is arranged to transmit a duty cycle command to the generator, and in which the generator is arranged to generate said modulating data sequence as a function of said duty cycle command. Advantageously, the control system is arranged to control the value of the duty cycle setpoint as a function of the temperature measured by the sensor. According to this embodiment, it is thus possible to control the density of "high" or "1" values ​​in the modulating data sequence. Each "high" or "1" value corresponds to a pulse of the modulated light beam, and the control system can therefore increase or decrease the average luminous power of the modulated light beam.

[0028] In yet another alternative or cumulative embodiment of the invention, the generator is arranged to generate a modulating binary data sequence in which the values ​​"1" are concentrated within a given period, and the control system is arranged to control the value of said given period as a function of the temperature measured by said sensor. This embodiment further enables the control system to increase or decrease the average luminous power of the modulated light beam by controlling a parameter of the modulating sequence.

[0029] In this example, the generator may, for instance, generate modulating data sequences of constant length, comprising the same number of data points regardless of the number of "1" values ​​in the sequence. The variation in the concentration time of the "1" values ​​can thus be achieved by the control system and the generator by modifying the duty cycle of an elementary sequence, supplemented by a continuous sequence of data points of the same value, either "1" or "0", to form the modulating data sequence. Alternatively, the variation in the concentration time of the "1" values ​​may be achieved by the control system and the generator by modifying the duration of the modulating data sequence, supplementing a predetermined and constant elementary sequence with a continuous sequence of data points of the same value, either "1" or "0", to form the modulating data sequence.

[0030] It should be noted that the control system will be able to combine the different embodiments above and control combinations of different parameters, for example the duty cycle of the modulating sequence and the peak light power setpoint, as a function of temperature, to maintain optimal performance of the telemetry function.

[0031] In one embodiment of the invention, the light module is a first light module capable of emitting a first light beam whose spectrum has a first peak below 490 nm, and the light system comprises a second light module capable of emitting a second light beam whose spectrum has a second peak above 490 nm, and a device for controlling the power supply provided to the second light module. Where applicable, the The control system is arranged to control the power supply control device, and in particular a duty cycle of this control device, as a function of the temperature measured by said sensor.

[0032] In this example, the light beam intended to perform a photometric function is decomposed into two light beams, the first light beam being emitted by the first light module, having a spectrum with a peak substantially in the blue and modulated at high frequency by the modulation unit from the received data sequence, and the second light beam being emitted by the second light module, having a spectrum with a peak substantially in the yellow or amber, and modulated at low frequency so that the combination of the two beams is white.The control system controls the modulation unit to influence the average power of the first light beam, increasing, decreasing, or maintaining it constant. These characteristics also allow control of the power supply control device provided to the second light module so that the average power of the second light beam is adjusted so that the combination of the first and second light beams remains white.

[0033] In one embodiment of the invention, the modulation unit is arranged to modulate the light beam emitted by the light module using the modulating data sequence received at a frequency greater than 5 MHz. In particular, the modulation frequency may be between 5 MHz and 200 MHz, and especially between 30 and 150 MHz. The duration of each pulse may be between 400 nanoseconds and 1 millisecond.

[0034] Advantageously, the modulation unit is arranged to generate a pulse-width modulated control signal, to modulate said control signal from the modulating data sequence it receives, and to control the emission of said light beam by the light module from the modulated control signal. For example, the modulation unit may be arranged to convert the modulating data sequence 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 be provided to control the light module so that said modulated light beam is emitted only for high values ​​of said modulating data sequence received from the processing unit and so that the modulated light beam is emitted according to said peak light power setting.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 modulated light beam emitted, necessary to achieve . The photometric function is thus defined by the peak light power, the duty cycle of the modulating data sequence and by the control signal.

[0035] Advantageously, the generator is arranged to generate a modulating, pseudo-random binary data sequence as a function of said duty cycle setpoint. If applicable, the control system is arranged to control the value of said duty cycle setpoint as a function of the temperature measured by said sensor.

[0036] A pseudo-random binary sequence, or PRBS, is a data sequence composed of high values, namely "1s", and low values, namely "0s". This type of sequence exhibits particularly interesting properties. Indeed, its autocorrelation function is at its maximum for a zero time lag, that is, when the sequence is compared to itself, and has a value significantly lower than this maximum for all other time lags, that is, when the sequence is compared to time-shifted versions of itself. Furthermore, the cross-correlation function between two pseudo-random binary sequences is significantly lower than the maximum of the autocorrelation functions of these sequences.Finally, this type of sequence is generally generated using a linear feedback shift register, or LFSR (from the English "Linear Feedback Shift Register"), which produces a periodic recurrence sequence whose pattern is a pseudo-random binary sequence.

[0037] Given the autocorrelation properties of pseudo-random binary sequences, a processing unit of the lighting system can estimate the 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 case of significant noise. Consequently, the processing unit can identify this time-shift 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.

[0038] Preferably, the generator is arranged to generate a modulating Kasami code-type data sequence as a function of said duty cycle setting

[0039] Alternatively, the generator may be arranged to generate a modulating data sequence of the type "m-sequence or maximum length sequence", of the type "Gold code", or any other pseudo-random binary sequence exhibiting good autocorrelation and crosscorrelation properties, or even orthogonality, and to transmit the modulating data sequence to the modulation unit of the emission module for the emission of a light beam modulated by the emission module.

[0040] In one embodiment of the invention, the control system is arranged to control said modulation parameter, by the modulation unit, so as to decrease the average power of the light beam emitted by the light module when the temperature measured by said sensor exceeds a first predetermined threshold value. This feature thus makes it possible to prevent an excessive temperature rise without significantly degrading the performance of the telemetry function.

[0041] For example, it may be provided that the control system is arranged to control the duty cycle of the modulation, by the modulation unit, to a value of 50% when the temperature is below said first predetermined threshold value and to decrease the duty cycle of the modulation with the temperature measured by said sensor down to a value of 20%, when this temperature exceeds a first predetermined threshold value.

[0042] Advantageously, the control system is arranged to control said modulation parameter, by the modulation unit, so as to increase the average power of the light beam emitted by the light module when the temperature measured by said sensor exceeds a second predetermined threshold value lower than the first threshold value. This feature makes it possible to maintain the performance of the telemetry function unchanged when the temperature is in a first heating range involving a slight derating strategy.

[0043] For example, the control system may be arranged to control the duty cycle of the modulation, by the modulation unit, to a value of 50% when the temperature is below said second predetermined threshold value, to increase the duty cycle of the modulation with the temperature measured by said sensor up to a value of 60%, when this temperature is between the second threshold value and the first threshold value, and then to decrease the duty cycle of the modulation with the temperature measured by said sensor down to a value of 20%, when this temperature exceeds the first predetermined threshold value.

[0044] In one embodiment of the invention, the lighting system comprises a receiving module capable of receiving a light beam, the receiving module comprising at least one elementary acquisition module comprising a A photodetector capable of converting a received light signal into an electrical signal, said elementary acquisition module being capable of generating a demodulated data sequence from the electrical signal converted by the photodetector. The control system includes a processing unit capable of receiving a demodulated data sequence generated by the elementary acquisition module(s) from a light beam received by the receiving module, the processing unit being arranged to determine a time of flight separating the emission of said modulated light beam from the reception of said light beam received from said demodulated data sequence and said modulating data sequence.

[0045] In one embodiment of the invention, the receiving module comprises a plurality of elementary acquisition modules, each including at least one photodetector capable of converting a received light signal into an electrical signal. Advantageously, the plurality of elementary acquisition modules is arranged in a matrix. For example, all the photodetectors of a single elementary acquisition module can form a sensor, for example, a single electronic component. Again, for example, each photodetector, or each plurality of photodetectors, may have a width and / or a length of less than ten micrometers, which makes it possible to obtain a reception field of the elementary acquisition module of a maximum of 0.1° and thus increase the spatial resolution of the receiving module.

[0046] Advantageously, the photodetector(s) of each elementary acquisition module(s) is an avalanche photodiode, in particular a single-photon one. This type of photodetector is also known as a 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 high gain, for example on the order of 10⁶, and therefore to compensate for the degradation of the signal-to-noise ratio due to external conditions.

[0047] According to one embodiment of the invention, the receiving module may include an optical unit arranged in front of the elementary acquisition modules.

[0048] For example, the elementary acquisition module or modules is capable of generating an elementary detection signal as a function of the electrical signal or signals converted by the photodetector or photodetectors of the elementary acquisition module; and each elementary acquisition module is arranged to compare said elementary detection signal to a threshold value associated with said elementary acquisition module and to generate said data sequence, said demodulated, from said comparison.

[0049] In a particular embodiment, the outputs of the photodetectors of each elementary acquisition module are connected in parallel to a A comparator is arranged to compare the sum of the electrical signals converted by these photodetectors to the threshold value associated with this elementary acquisition module and to generate the demodulated data sequence based on this comparison. The comparator thus forms a demodulation unit for the light beam received by the receiving module, capable of extracting a demodulated data sequence from the electrical signals converted by the photodetectors. Alternatively, the comparator can be replaced by active circuits.

[0050] In the context of the present invention, "computing unit" means one or more electronic and / or software components capable of receiving a first data sequence and a second data sequence and of detecting the presence of the first data sequence in the second data sequence, and of determining a time of flight separating the emission of a modulated light beam containing the first data sequence from the reception of a received light beam from which the second data sequence has been extracted.

[0051] Advantageously, the computing unit is arranged to estimate values ​​of a correlation function between said demodulated data sequence and said modulating data sequence and to determine a time of flight separating the emission of said modulated light beam emitted from the reception of said light beam received from the values ​​of the correlation function.

[0052] Each value of the correlation function estimated by the computing unit is associated with a time lag value 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.

[0053] It is thus possible to detect the presence of this modulating data sequence in the received light beam, after reflection on an object in the environment of the vehicle and thus detect the presence of this object as well as estimate its distance from the vehicle.

[0054] Preferably, the computing unit is arranged to determine the value of a peak of said correlation function, to compare said peak value to a predetermined threshold value, and to detect the presence of said modulating data sequence in the demodulated data sequence based on said comparison. The computing 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.

[0055] In one 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.

[0056] Advantageously, the emitting module is arranged so that the light beam participates, wholly or partially, in the performance of a predetermined regulatory photometric function. For example, it could be a daytime running light (DRL), which has the advantage of being emitted over a wide field with low intensity.

[0057] 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 according to the invention.

[0058] Of course, the different features, variants and embodiments of the invention can be combined with each other in various ways insofar as they are not incompatible or mutually exclusive.

[0059] In addition, various other features of the invention become apparent from the attached description made with reference to the drawings which illustrate non-limiting embodiments of the invention and where:

[0060] [Fig-1] represents, schematically and partially, a view of a system luminous of a motor vehicle according to an example of an embodiment of the invention;

[0061] [Fig.2] represents, schematically and partially, an example of operation of the system in [Fig. 1] during the implementation of a telemetry process; and

[0062] [Fig.3] represents, schematically and partially, examples of control of the lighting system of [Fig.1] according to an embodiment of the invention.

[0063] It should be noted that in these figures the structural and / or functional elements common to the different variants may have the same references.

[0064] Of course, various other modifications can be made to the invention within the scope of the annexed claims.

[0065] With reference to [Fig. 1], the present invention is a lighting system 1 of a vehicle comprising an emission module 2, a reception module 3, and a control system 4. [Fig. 3] represents a detailed view of the electronic architecture of the system 1.

[0066] The emission module 2 includes a light module 21 capable of emitting a first light beam Fl, and a modulation unit 22 capable of receiving a modulating data sequence Seq_m generated by a generator 41 of the control system 4 and arranged to modulate the light beam Fl emitted from said modulating sequence Seq_m.

[0067] The first emission module 2 is for example arranged in a headlight of the motor vehicle.

[0068] The light module 21 comprises a plurality of light sources, for example connected in series one after the other. In the example described, each source The light source is a light-emitting diode (LED) less than 500 micrometers in size, preferably approximately 300 micrometers in size, and the light module comprises at least three sources connected in series. Each light source may be formed from a block of several elementary light sources connected in parallel, without departing from the scope of the present invention. The light module may also comprise other branches of light sources connected in series, one after the other, with the branches connected in parallel, without departing from the scope of the present invention.

[0069] The light module 21 is arranged so that the light beam Fl it emits has an electromagnetic spectrum, at least a portion of which lies 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 should be noted that the spectrum may also have other intensity peaks in the visible and / or infrared ranges.

[0070] Insofar as the light beam Fl is composed, partially or entirely, of white light, it is possible to use this light beam to participate, partially or entirely, in the performance of a predetermined photometric function, particularly a regulatory one. In this case, the light module 21 may include an optical unit arranged to shape this light beam Fl so that its photometric distribution meets the requirements of said function. For example, the light beam Fl may be used to perform a daytime running light (DRL) function.

[0071] In addition to this photometric function, the light beam Fl enables the system 1 to perform functions of detection and evaluation of the position of an obstacle on the road and / or communication with another vehicle or with road infrastructure.

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

[0073] For these purposes, the modulation unit 22 is a high-frequency driver and includes a generator (not shown) of a pulse-width modulated control signal. This control signal controls a switched-mode power supply 51 supplied to the light sources of the light module 21. Conventionally, the duty cycle of this control signal, set by the modulation unit 22, thus controls the average electrical power supplied to the light sources, and therefore controls the luminous intensity of the light beam Fl, so as to satisfy the requirements of the photometric function it performs.

[0074] In the example described, the modulation unit 22 is arranged to convert the data sequence Seq_m into a modulating signal and to modulate the initial control signal using this modulating signal. It should be noted that several types of modulation can be used interchangeably within the framework of the present invention, and in particular on-off keying (OOK), pulse code modulation (PCM), pulse amplitude modulation (PAM), pulse width modulation (PWM), or pulse position modulation (PPM).

[0075] The light beam Fl emitted by the light module 21 is composed of a train of successive light pulses with a sufficiently high frequency, for example greater than 30 MHz, in particular between 50 MHz and 100 MHz, so that the human eye can no longer distinguish them. Furthermore, the amplitude, width, and / or position of each pulse with respect to the period allows the light beam Fl to carry the data sequence Seq_m.

[0076] 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.

[0077] This receiving module 3 comprises a plurality of elementary acquisition modules 3¾. Each elementary acquisition module 3¾ includes several photodetectors 32ak>i, each capable of converting a light signal it receives into an electrical signal Selk4. Each elementary acquisition module 3¾ also includes 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 Sdc, formed from the sum of the electrical signals Selk>i from these photodetectors 32akJ. The comparator is arranged to compare this elementary detection signal Sdc to a given threshold value, the comparison yielding a high value, or a "1", when the elementary detection signal Sdc, is greater than the threshold value, and a low value, or a "0", when the elementary detection signal Sde^ is less than the threshold value.The demodulation unit 34 is thus arranged to generate a demodulated binary sequence Seq_dij, which it transmits to a computing unit 42 of the control system 4.

[0078] In the example described, the photodetectors 32ak> i are identical and each consists of 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 on the order of micrometer. The assembly thus forms a sensor whose spatial reception resolution is on the order of 1°, or even 0.1°, and whose detection capabilities, due to the use of avalanche photodiodes, are particularly important, even in the case of degraded acquisition conditions.

[0079] Each electrical signal Selk>i represents the activation and deactivation sequences of the photodiode 32ak>i under the effect of photons that have struck this photodiode. An incident photon can indeed trigger an avalanche effect, leading to the generation of an electrical signal Selk4 for an elementary period of one or a few nanoseconds, during which the photodiode is inoperative. Then, the photodiode again becomes inactive, awaiting a new incident photon, with no electrical signal being generated by this photodiode in this state. The elementary detection signal Sde^ resulting from the sum of these electrical signals Selkj therefore represents an estimate of the number of photons that have reached the sensor during each elementary period. It thus contains information relating to the optical power incident on the sensor, which may include a portion of the beam emitted by the emitting module and then reflected by an obstacle.

[0080] Alternatively, the comparator of the demodulation unit 34 may be replaced by active circuits, the demodulated data sequence in this case being directly a digital sequence made up of "1" and "0".

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

[0082] The processing unit 42 is capable of receiving the demodulated binary sequences Seq_d;j, generated by the elementary acquisition modules 3¾, and of detecting in each demodulated binary sequence Seq_dij, the presence of the modulating data sequence Seq_m. The demodulation units 34 thus make it possible to reduce the amount of data that has to be handled by the processing unit, thereby compressing the elementary detection signals Sde^.

[0083] To this end, the computing unit 42 is arranged to estimate values ​​of a correlation function Fcorr, between each demodulated binary sequence Seq_dij and the modulating data sequence Seq_m, and to detect the presence of the modulating data sequence Seq_m in this demodulated binary sequence Seq_dij based on these values ​​of the correlation function Fcorr,. Upon detection, it can then determine a time of flight r separating the emission of the first modulated light beam emitted Fl from the reception of the received light beam F2.

[0084] The computing unit 42 can thus 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.

[0085] In a first step El, the generator 41 periodically generates a modulating data sequence Seq_m, for example of Kasami code type, composed of "0" and "1", pseudo-random and of maximum size, exhibiting under nominal operating conditions a duty cycle of 50%.

[0086] The generator 41 transmits the modulating data sequence Seq_m to the modulation unit 22 of the emission module 2 for the emission of the light beam Fl by the emission module 2.

[0087] In a second step E2, the modulation unit 22 modulates the light beam Fl emitted by the light module 21 using this data sequence Seq_m and a light power setpoint pic Pp. Thus, the modulation unit 22 converts the data sequence Seq_m into a modulating signal and modulates the initial control signal using this modulating signal.

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

[0089] The light beam Fl is thus emitted until it reaches an object O, located in the environment of the vehicle, which reflects it towards the receiving module 3.

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

[0091] When the sunlight conditions in the vicinity of the vehicle are particularly important, the 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 reflected by the object O and noise, for example generated by sources of parasitic light such as urban lighting, car lighting, or even the sun.

[0092] In a third step E3, each of the elementary acquisition modules 3¾ thus extracts, using its demodulation unit 34, a demodulated binary sequence Seq_dij which it transmits to the calculation unit 42.

[0093] For each demodulated binary sequence Seq_d;j that it receives, the computing unit 42 estimates, in a fourth step E4, values ​​of a correlation function Fcorr, , between the modulating sequence Seq_m and this demodulated binary sequence Seq_dij.

[0094] The computing unit 42 thus evaluates, for a plurality of time lag values, the value of the cross correlation, by means of a cyclic convolution product, between each demodulated binary sequence Seq_d;j and the modulating sequence Seq_m delayed according to each of the time offset values.

[0095] Given the autocorrelation and cross-correlation properties of the modulating sequence, the correlation function Fcorr; j 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 3¾ of the reception module 3, the modulating sequence Seq_m delayed by this value thus corresponding substantially to the demodulated binary sequence Seq_dij up to noise.

[0096] In a fifth step E5, the computing unit 42 identifies the maximum value Fcorr_max of each correlation function Fcorr;j associated with each elementary acquisition module 3¾ and compares it to a threshold value Vs.

[0097] In the case where this maximum value Fcorr_max is greater than the threshold value Vs, the modulating sequence Seq_m is considered to be detected by the computing unit 42 in the demodulated binary sequence Seq_dij from the elementary acquisition module 32;j associated with this correlation function Fcorrij. An object O is therefore detected in the angular range, or pixel, monitored by this elementary acquisition module 32;j and the computing unit 42 can then estimate, in a sixth step E6, the value r of the time of flight of the light beam 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.

[0098] The operating mode just described corresponds to normal operating conditions, in which the modulation unit 22 and the light sources of the light module 21 operate at normal temperatures. Under these conditions, the peak light power setpoint Pp can be adjusted by the control system with respect to the 50% duty cycle of the modulating sequence Seq_m to optimize the average light power of the light beam Fl with regard to the desired performance of the telemetry function, in particular to benefit from the maximum detection range operated by the telemetry function.

[0099] In order to maintain substantially equivalent performance or to find an acceptable compromise between the performance of the telemetry function and the thermal stress experienced by the components of the transmission module 2, the transmission module 2 includes a temperature sensor 23.

[0100] In the example of [Fig. 1], the temperature sensor 23 is a temperature sensor for the light sources of the light module 21, for example integrated into the housing, or "package", incorporating these light sources. Alternatively, the sensor 23 may be a temperature sensor arranged in the vicinity of these light sources, or even a temperature sensor for the modulation unit 22. or a sensor capable of indirectly measuring the temperature of the light module 21 or the modulation unit, via a measurement of the thermal resistance of these components or the forward voltage across the terminals of these components.

[0101] The control system 4 is thus arranged to control a parameter of the modulation, implemented by the modulation unit 22, of the light beam emitted Fl by the light module 21 as a function of the temperature measured by said sensor 23.

[0102] It will be noted that the average power of the modulated light beam emitted Fl is thus defined, among other things, by the number of bits with a value of "1" in the modulating sequence Seq_m in relation to the total number of bits in this sequence Seq_m, by the total number of bits in this sequence Seq_m, by the density of bits with a value of "1" in the modulating sequence, by the duration of each of the pulses composing the light beam Fl and by the peak light power Pp of these pulses.

[0103] The control system 4 can thus control each of these parameters to influence the average luminous power of the beam Fl, so as to allow a reduction in the operating current of the light sources of the light module 21 without significantly degrading the performance of the telemetry function.

[0104] With reference to [Fig.3], we will describe an example of control of different parameters, namely the duty cycle 0 and the peak power Pp by the control system 4 as a function of the temperature measured by the sensor 23.

[0105] Fig. 3 represents, in the upper part, the temperature T° of the light sources of the light module 21 measured by the sensor 23; in the middle part the modulating sequence Seq_m generated by the generator 41 according to this temperature T° and in the lower part the modulation of the light beam Fl operated by the modulation unit 22 according to this temperature T°.

[0106] The control system 4 compares the temperature T° to two threshold values ​​Ti and T2, the threshold value T2 being lower than the threshold value Tb

[0107] As long as the temperature T° is below the threshold value T2, the emission module 2 is in normal operating conditions, for which there is no need to reduce the operating current of the light sources of the light module 21. The modulation is thus carried out by the modulation unit 22 with a duty cycle 0 of 50% and with a peak power Pp corresponding to an optimal operating current.

[0108] When the temperature T° exceeds the threshold value T2 while remaining below the threshold value, the control system 4 transmits to the generator 41 a duty cycle reference setpoint 0i greater than 50%, for example 60%.

[0109] The generator 41 then generates a new modulating data sequence Seq_mi of Kasami code type, of identical length to the previous sequence Seq_m, and whose number of bits of value "1" is selected according to said duty cycle instruction 0b This number is greater than that of the sequence Seq_m, the density of "1" in the sequence Seq_mi being greater than that of the sequence Seq_m.

[0110] In return, in order to comply with the regulatory constraints governing the photometric function performed by the light beam Fl, the control system 4 transmits a peak light power setpoint Ppi lower than the previous setpoint Pp.

[0111] Despite the reduction in the operating current of the light sources required by heating of these light sources, the average luminous power of the light beam Fl therefore remains substantially unchanged.

[0112] When the temperature T° exceeds the threshold value, the control system 4 transmits to the generator 41 a duty cycle setpoint 02 of less than 50%. The setpoint value can be selected from a range of 20% to 50%, depending on the temperature T° measured by the sensor 23.

[0113] In the example described, generator 41 then generates, from this instruction 02, a new modulating data sequence of Kasami code type, shorter than the previous sequences Seq_m and Seq_mi. Generator 41 then completes this sequence with a continuous sequence of "0"s to form a modulating data sequence Seq_m2. The sequence Seq_m2 thus obtained retains satisfactory autocorrelation and crosscorrelation properties while exhibiting a lower density of "1"s than the sequence Seq_m, the "1"s also being concentrated over a shorter period.

[0114] In return, the control system 4 transmits a peak light power setpoint Pp 2 higher than the previous setpoint Pp.

[0115] Despite the reduction in the operating current of the light sources required by heating of these light sources, the reduction in the average luminous power of the light beam Fl only slightly impacts the performance of the telemetry function.

[0116] It may be foreseen, in variants not shown, that the control system 4 controls other parameters of the modulation operated by the modulation unit 22 which may influence the average luminous power of the modulated light beam emitted Fl, and in particular the duration of the data sequence or the duration of each of the pulses.

[0117] The preceding description clearly explains how the invention achieves its objectives, namely to provide a lighting system for a motor vehicle capable of performing both a photometric function and a lighting system. regulatory data and a telemetry function, and in which the performance of the telemetry function remains acceptable in the event of overheating of a component of the transmission module. These objectives are achieved in particular using a control system capable of controlling one or more parameters controlling the average luminous power of the modulated light beam emitted as a function of the temperature measured by a sensor of the transmission module.

[0118] In any event, the invention is not limited to the embodiments specifically described in this document, and extends in particular to all equivalent means and to any technically feasible combination of these means. In particular, other configurations of the emission modules may be provided, and notably an emission module employing other types of light source than those described, such as a laser diode, a VCSEL, an SLED, or an RGB diode. Other photometric functions than that described may also be provided, and in particular low beam lighting functions or signaling functions such as position lights or direction indicators.

Claims

Demands

1. A light system (1) of a motor vehicle, comprising: a. an emission module (2) comprising a light module (21) capable of emitting a light beam (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, (Seq_m, Seq_mi, Seq_m2) and arranged to modulate said light beam emitted from the received data sequence; b.a control system (4) comprising a generator (41) arranged to generate a modulating data sequence (Seq_m, Seq_mi, Seq_m2) and to transmit said modulating data sequence to the modulation unit (22) for the emission of a modulated light beam (Fl) by the emission module; characterized in that it comprises at least one sensor (23) capable of measuring the temperature (T°) of all or part of the emission module, and in that the control system is arranged to control a parameter (0, Pp) of the modulation, by the modulation unit (22), of the light beam emitted by the light module (21) as a function of the temperature measured by said sensor.

2. A light system (1) according to the preceding claim, wherein the control system (4) is arranged to transmit to the modulation unit (22) a peak light power setpoint (Pp, Ppb Pp2), and wherein the modulation unit (22) is arranged to modulate said light beam (Fl) from the received modulating data sequence (Seq_m, Seq_mi, Seq_m2) so that the emitted light beam is formed by a train of light pulses, each having a power conforming to said peak light power setpoint, characterized in that the control system is arranged to control the value of said peak light power setpoint as a function of the temperature (T°) measured by said sensor (23).

3. A lighting system (1) according to any one of the preceding claims, wherein the control system (4) is arranged to transmit to the generator (41) a duty cycle setpoint (0, 0B 02), and in which the generator is arranged to generate said modulating data sequence (Seq_m, Seq_mi, Seq_m2) as a function of said duty cycle setpoint; characterized in that the control system is arranged to control the value of said duty cycle setpoint as a function of the temperature (T°) measured by said sensor (23).

4. Lighting system (1) according to the preceding claim, wherein the generator (41) is arranged to generate a modulating data sequence (Seq_m, Seq_mi, Seq_m2) of pseudo-random binary type as a function of said duty cycle setpoint (0, 0b 02); characterized in that the control system (4) is arranged to control the value of said duty cycle setpoint as a function of the temperature (T°) measured by said sensor (12).

5. Light system (1) according to any one of the preceding claims, wherein the generator (41) is arranged to generate a modulating data sequence (Seq_m, Seq_mi, Seq_m2) of binary type in which the values ​​"1" are concentrated in a given period and in which the control system (4) is arranged to control the value of said given period as a function of the temperature (T°) measured by said sensor (23).

6. Light system (1) according to any one of the preceding claims, characterized in that the control system (4) is arranged to control said parameter (0, Pp) of the modulation, by the modulation unit (22), so as to decrease the average power of the light beam (Fl) emitted by the light module (21) when the temperature (T°) measured by said sensor (23) exceeds a first predetermined threshold value (Ti).

7. Lighting system (1) according to any one of the preceding claims, characterized in that the control system (4) is arranged to control said parameter (0, Pp) of the modulation, by the modulation unit (22), so as to increase the average power of the light beam (Fl) emitted by the light module (21) when the temperature (T°) measured by said sensor (23) exceeds a second predetermined threshold value (T2) lower than the first threshold value (TJ).

8. A lighting system (1) according to any one of the preceding claims, characterized in that it comprises a receiving module (3) capable to receive a light beam (F2), in which the receiving module comprises at least one elementary acquisition module (32ij) including a photodetector (32ak i) capable of converting a light signal which it receives into an electrical signal (Selkji), said elementary acquisition module (32) being capable of generating a data sequence, said demodulated, (Seq_d;j) from the electrical signal converted by the photodetector; and in that the control system comprises a computing unit (42) capable of receiving a demodulated data sequence (Seq_dij) generated by the or each elementary acquisition module from a light beam received (F2) by the receiving module, the computing unit (42) being arranged to determine a time of flight (r) separating the emission of said modulated light beam emitted from the reception of said light beam received from said demodulated data sequence (Seq_d;j) and said modulating data sequence (Seq_m).

9. Light system (1) according to the preceding claim, characterized in that the computing unit (42) is arranged to estimate values ​​of a correlation function (Fcon^) between said demodulated data sequence (Seq_dij) and said modulating data sequence (Seq_m) and to determine a time of flight (r) separating the emission of said modulated light beam emitted (F1) from the reception of said received light beam (F2) from the values ​​of the correlation function.

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

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

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