Motor vehicle lighting system comprising a module for emitting a light beam and a temperature sensor

Abstract

The invention relates to a motor vehicle lighting system (1) comprising: an emitting module (2) comprising a light module (21) capable of emitting a light beam (F1), and a modulation unit (22) capable of modulating the light beam on the basis of 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) in order for the emitting module to emit a modulated light beam (F1); characterised in that it comprises at least one sensor (23) capable of measuring the temperature (T°) of the emitting 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 according to the temperature measured by the sensor.

Description

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 vehicle's lighting system to perform a given photometric function.

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

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

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

[0006] However, this type of system, 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 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 its power output is too high, the emission duration is too long, and / or the modulation is too rapid. In these situations, it is necessary to reduce the operating current to decrease the thermal stress on the light source. This process is known as "derating."

[0009] This decrease in operating current 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 for 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 using a data sequence. The modulated light beam thus performs the photometric function. The resulting light beam could, for example, be a pulsed beam, each pulse corresponding to one or more consecutive high values ​​of the modulating sequence, and the interval separating 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 that the average light power of the emitted modulated light beam, necessary to perform the photometric function, is thus defined by the peak light power and the duty cycle of the modulating data sequence.Since the modulating sequence is generated cyclically 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 from an object in the vehicle's environment, and a processing unit can then detect it from a demodulated data sequence. 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 environment of the vehicle 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, thereby allowing a reduction in the operating current of the light source in 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, 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, a "sensor capable of measuring the temperature of all or part of the transmission module" means any element or combination of electronic and / or software components capable of obtaining a direct or indirect measurement of the temperature of an element 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 an element of the transmission module that may vary with the temperature of that element or another element, 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 could, for example, be a high-frequency driver device.

[0021] In one embodiment of the invention, the light module includes 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 elementary light beam to obtain said light beam. Where applicable, the unit of Modulation 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 through electroluminescence in response to an electric current passing through it. The photoluminescent element could, for example, be in the form of a cerium-doped yttrium aluminum garnet resin, or CE:YAG, capable of absorbing blue light and, through photoluminescence in response to the excitation produced by this light, emitting yellow light. The photoluminescent element is positioned on the generator so that some of the blue light excites it, causing it to emit orange light through photoluminescence. The remaining blue light passes through this element. Thus, when electrically powered, the light source simultaneously emits blue and yellow light in proportions such that the resulting light appears white to the human eye.

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

[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 the light beam based on the received modulating data sequence so that the emitted light beam consists of a train of light pulses, each with a light power conforming to the peak power setpoint. Advantageously, the control system is arranged to control the value of the peak light power setpoint based on the temperature measured by the sensor. This embodiment allows the control system to increase or decrease the light power. average of the modulated light beam, without impacting the data sequence.

[0027] In another alternative or cumulative embodiment of the invention, the control system is arranged to transmit a duty cycle setpoint to the generator, and wherein the generator is arranged to generate the modulating data sequence according to the duty cycle setpoint. 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. Since each "high" or "1" value corresponds to a pulse of the modulated light beam, the control system can thus 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 allows 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 could, for instance, produce 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 duration 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 duration of the "1" values ​​could 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 control device for the power supply provided to the second light module. Optionally, 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, exhibiting 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, exhibiting 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, in order to increase it, decrease it or keep it constant; these characteristics also allow control of the power supply control device supplied 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. It may also be provided that the the duration of each pulse should 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 based on the modulating data sequence it receives, and to control the emission of said light beam by the light module based on 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 for the realization of 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 configured to generate a modulating, pseudo-random binary data sequence based on the duty cycle setpoint. If necessary, the control system is configured to control the value of the duty cycle setpoint based on the temperature measured by the 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 random 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 recurrence sequence whose pattern is a pseudo-random binary sequence.

[0037] Given the autocorrelation properties of pseudo-random binary sequences, a light system processing unit can estimate the values ​​of a correlation function between a modulating sequence and a demodulated sequence extracted from a light beam received by the receiver module. The correlation function will be at its maximum for the time-shift value corresponding to the time of flight of the modulated light beam as it is emitted, reflected, and then received, even in the presence of significant noise. 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 configured to generate a modulating Kasami-type data sequence based on the aforementioned duty cycle instruction.

[0039] Alternatively, the generator can 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 the sensor exceeds a predetermined threshold value. This feature prevents excessive temperature rise without significantly degrading the performance of the telemetry function.

[0041] For example, it may be possible to provide 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 the modulation parameter, via the modulation unit, so as to increase the average power of the light beam emitted by the light module when the temperature measured by the sensor exceeds a second predetermined threshold value lower than the first threshold value. This feature allows the telemetry function's performance to remain unchanged when the temperature is within a first heating range, thus necessitating a slight derating strategy.

[0043] 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 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 including a photodetector capable of converting a light signal it receives into an electrical signal, said elementary acquisition module being capable of generating a data sequence, said demodulated, from the electrical signal converted by the photodetector. The control system includes a computing unit capable of receiving a demodulated data sequence generated by the or each elementary acquisition module from a light beam received by the receiving module, the computing unit being arranged to determine a time of flight separating the emission of said modulated light beam emitted 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 length of less than ten micrometers, which makes it possible to obtain a receiving field of view of the elementary acquisition module of a maximum of 0.1° and thus increase the spatial resolution of the receiving module.

[0046] Advantageously, each photodetector of each elementary acquisition module is an avalanche photodiode, specifically a single-photon type. This type of photodetector is also known as a SPAD, from the English "Single-Photon Avalanche Diode." A collection of avalanche photodiodes can thus form a silicon photomultiplier, or SiPM (from the English "Silicon Photomultiplier"). This type of photodetector makes it possible to detect the impact of a single photon with a high gain, for example, on the order of 10⁶, and therefore to compensate for signal-to-noise ratio degradation 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(s) is capable of generating an elementary detection signal based on the electrical signal(s) converted by the photodetector(s) of the elementary acquisition module; and each elementary acquisition module is arranged to compare said detection signal elementary to a threshold value associated with said elementary acquisition module and to generate said data sequence, said demodulated, from said comparison.

[0049] In one particular embodiment, the outputs of the photodetectors of each elementary acquisition module are connected in parallel to a comparator arranged to compare the sum of the electrical signals converted by these photodetectors to the threshold value associated with that 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 in the modulating data sequence, or the demodulated data sequence, used to estimate that 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] We can thus detect the presence of this modulating data sequence in the light beam received, after reflection on an object in the environment of the vehicle and thus detect the presence of this object and estimate its distance from the vehicle.

[0054] Preferably, the computing unit is configured to determine the value of a peak in 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 fulfilling 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 area 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 as long as they are not incompatible or mutually exclusive.

[0059] Furthermore, 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 lighting system of a motor vehicle according to an example of an embodiment of the invention;

[0061] [Fig. 2] schematically and partially represents an example of the 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 attached claims.

[0065] With reference to [Fig. 1], the present invention is a vehicle lighting system 1 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 system 1.

[0066] The emission module 2 includes a light module 21 capable of emitting a first light beam F1, 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 F1 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. In the example described, each light source is a light-emitting diode (LED) smaller than 500 micrometers, 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. It is further envisaged that the light module 21 includes other branches of light sources mounted in series one after the other, the branches being mounted in parallel, without going out of the scope of the present invention.

[0069] The light module 21 is arranged so that the light beam F1 it emits has an electromagnetic spectrum in which at least a portion lies within the visible spectrum. Preferably, the spectrum of this light beam F1 exhibits a peak intensity, or line, in the blue at 450 nm. It should be noted that the spectrum may also contain other peak intensity in the visible and / or infrared regions.

[0070] Since the light beam F1 is composed, partially or entirely, of white light, it is possible to use this light beam to contribute, partially or entirely, to 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 F1 so that its photometric distribution meets the requirements of said function. For example, the light beam F1 may be used to perform a daytime running light (DRL) function.

[0071] In addition to this photometric function, the F1 light beam allows 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.

[0072] For these purposes, the modulation unit 22 is arranged to modulate the light beam F1 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 this purpose, 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 F1, 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 F1 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, specifically 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 relative to the period allows the light beam F1 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 F1 towards the receiving module 3, which thus receives a light beam F2.

[0077] This receiving module 3 comprises a plurality of elementary acquisition modules 32i,j. Each elementary acquisition module 32i,j includes several photodetectors 32ak,I, each capable of converting a received light signal into an electrical signal Selk,I. Each elementary acquisition module 32i,j 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 Sdeij formed from the sum of the electrical signals Selk,I from these photodetectors 32ak,I.The comparator is configured to compare this elementary detection signal Sdeij to a given threshold value, the comparison yielding a high value, or a "1", when the elementary detection signal Sdeij is greater than the threshold value, and a low value, or a "0", when the elementary detection signal Sdeij is less than the threshold value. The demodulation unit 34 is thus configured to generate a demodulated binary sequence Seq_di,j, which it transmits to a processing unit 42 du. control system 4.

[0078] In the example described, the photodetectors 32ak,l are identical and each consists of a single-photon avalanche photodiode (SPAD). These photodiodes and the demodulation unit 34 are integrated into a silicon photomultiplier (SiPM). It should be noted that the dimensions of the photodetectors are on the order of a micrometer. The assembly thus forms a sensor with a spatial reception resolution on the order of 1°, or even 0.1°, and whose detection capabilities, due to the use of avalanche photodiodes, are particularly high, even under degraded acquisition conditions.

[0079] Each electrical signal Selk,I represents the activation and deactivation sequences of the photodiode 32ak,I under the influence of photons that have struck it. An incident photon can indeed trigger an avalanche effect, leading to the generation of an electrical signal Selk,I for an elementary period of one or a few nanoseconds, during which the photodiode is inoperative. Then, the photodiode becomes, once again, in a state of waiting for a new incident photon, with no electrical signal being generated by the photodiode in this state. The elementary detection signal SdeiJ, resulting from the sum of these electrical signals Selk,I, 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 transmitting module and then reflected by an obstacle.

[0080] Alternatively, it may be possible to replace the comparator of the demodulation unit 34 with 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_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 amount of data that must be handled by the processing unit, thereby compressing the elementary detection signals Sdeij.

[0083] To this end, the computing unit 42 is configured to estimate values ​​of a correlation function Fcorrij between each demodulated binary sequence Seq_di j 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_di,j, based on these values ​​of the correlation function Fcorrij. Upon detection, it can then determine a time of flight T separating the emission of the first modulated light beam F1 from the reception of the first 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 connection with [Fig. 2] which represents a telemetry process implemented by the light system 1.

[0085] In a first step E1, 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 in 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 F1 by the emission module 2.

[0087] In a second step E2, the modulation unit 22 modulates the light beam F1 emitted by the light module 21 using this data sequence Seq_m and a peak light power setpoint 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 F1 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 F1 containing the Seq_m sequence is thus defined by the number of bits with a value of "1" in this Seq_m sequence 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 F1 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 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 F1 reflected by the object O and noise, for example generated by sources of stray light such as urban lighting, car lighting, or even the sun.

[0092] In a third step E3, each of the elementary acquisition modules 32i,j thus extracts, using its demodulation unit 34, a demodulated binary sequence Seq_di j which it transmits to the calculation unit 42.

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

[0094] The computing unit 42 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,j and the modulating sequence Seq_m delayed according to each of the time-shift values.

[0095] Given the autocorrelation and cross-correlation properties of the modulating sequence, the correlation function Fcorrij will thus be maximum for a time shift value corresponding to the time of flight of the light beam F1, 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,j of the reception module 3, the modulating sequence Seq_m delayed by this value thus corresponding substantially to the demodulated binary sequence Seq_di,j up to noise.

[0096] In a fifth step E5, the calculation unit 42 identifies the maximum value Fcorr_max of each correlation function Fcorrij associated with each elementary acquisition module 32i,j and compares it to a threshold value Vs.

[0097] If this maximum value Fcorrjnax is greater than the threshold value Vs, the modulating sequence Seq_m is considered to be detected by the processing unit 42 in the demodulated binary sequence Seq_di,j from the elementary acquisition module 32i,j associated with this correlation function Fcorrij. An object O is therefore detected within the angular range, or pixel, monitored by this elementary acquisition module 32i,j, and the processing unit 42 can then estimate, in a sixth step E6, the value T of the time of flight of the light beam F1 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 F1 with regard to the desired performance of the telemetry function, in particular to achieve maximum detection range.

[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 in [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," containing these light sources. Alternatively, the sensor 23 could be a temperature sensor located near these light sources, or 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 F1 by the light module 21 as a function of the temperature measured by said sensor 23.

[0102] It should be noted that the average power of the modulated light beam emitted F1 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 F1 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 light power of the beam F1, 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] The [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 F1 operated by the modulation unit 22 according to this temperature T°.

[0106] The control system 4 compares the temperature T° to two threshold values ​​T1 and T2, the threshold value T2 being lower than the threshold value T1.

[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 mo- unit 22-fold extension with a duty cycle 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 T1, the control system 4 transmits to the generator 41 a duty cycle reference setpoint 01 greater than 50%, for example 60%.

[0109] Generator 41 then generates a new modulating data sequence Seq_m1 of Kasami code type, of identical length to the previous sequence Seq_m, and whose number of bits with the value "1" is selected according to the said duty cycle instruction 01. This number is greater than that of the sequence Seq_m, the density of "1" in the sequence Seq_m1 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 F1, the control system 4 transmits a peak light power setpoint Pp1 lower than the previous setpoint Pp.

[0111] Despite the reduction in the operating current of the light sources required by heating these light sources, the average luminous power of the light beam F1 therefore remains substantially unchanged.

[0112] When the temperature T° exceeds the threshold value T1, the control system 4 transmits a duty cycle setpoint 02 of less than 50% to the generator 41. 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_m1. Generator 41 then completes this sequence with a continuous sequence of "0"s to form a modulating data sequence Seq_m2. The resulting Seq_m2 sequence thus retains satisfactory autocorrelation and crosscorrelation properties while exhibiting a lower density of "1"s than the Seq_m sequence, the "1"s also being concentrated over a shorter period.

[0114] In return, control system 4 transmits a peak light power setpoint Pp2 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 F1 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 F1, 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 given regulatory photometric function and a telemetry function, and in which the performance of the telemetry function remains acceptable even if a component of the emission module overheats. These objectives are achieved, in particular, through a control system capable of controlling one or more parameters that regulate the average luminous intensity of the modulated light beam emitted as a function of the temperature measured by a sensor on the emission 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, including 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. It may also be provided for the implementation of other photometric functions than that described, including dipped 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 (F1) 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_m1, 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_m1, Seq_m2) and to transmit said modulating data sequence 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 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, Pp1, Pp2), and wherein the modulation unit (22) is arranged to modulate said light beam (F1) from the received modulating data sequence (Seq_m, Seq_m1, 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, 01, 02), and wherein the generator is arranged to generate said modulating data sequence (Seq_m, Seq_m1, 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_m1, Seq_m2) of pseudo-random binary type as a function of said duty cycle setpoint (0, 01, 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_m1, 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 (F1) emitted by the light module (21) when the temperature (T°) measured by said sensor (23) exceeds a first predetermined threshold value (T1).

7. A lighting system (1) according to any one of the preceding claims, characterized in that the control system (4) is arranged to control said modulation parameter (0, Pp) by the modulation unit (22) so as to increase the average power of the emitted light beam (F1). Tl 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 (T1).

8. A light system (1) according to any one of the preceding claims, characterized in that it comprises a receiving module (3) capable of receiving a light beam (F2), in which the receiving module comprises at least one elementary acquisition module (32i,j) comprising a photodetector (32ak, I) capable of converting a light signal that it receives into an electrical signal (Selk.(l), said elementary acquisition module (32) being capable of generating a data sequence, said demodulated, (Seq_di,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_di,j) 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 (T) separating the emission of said modulated light beam emitted from the reception of said light beam received from said demodulated data sequence (Seq_di,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 (Fcorrij) between said demodulated data sequence (Seq_di,j) and said modulating data sequence (Seq_m) and to determine a time of flight (T) 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 lighting system (1) according to the preceding claim, wherein the emission module (2) is arranged such that the light beam (F1) participates, totally or partially, in the realization of a predetermined regulatory photometric function.

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