Detection system of motor vehicle comprising module for emitting light beam and module for receiving light beam

Abstract

The invention relates to a lighting system (1) of a motor vehicle, comprising a transmitter module (2) having a lighting module (21) and a modulation unit (22); a receiving module (3) for receiving the light beam (F2); the invention relates to a light emitting system (1) comprising a computing unit (4) for receiving a first instruction for transmitting a first photometric function, said computing unit being arranged to generate a first modulated data sequence (Seq2a) having a first duty cycle, and the computing unit is capable of receiving a second instruction for transmitting a given second photometric function and is arranged to generate a second modulated data sequence (Seq2b) having a second duty cycle different from the first duty cycle.

Description

[0001] The present invention relates to the field of automotive lighting and to a function for detecting an object by a motor vehicle and estimating the distance separating the object from the vehicle. More precisely, the present invention relates to a lighting system for a motor vehicle capable of performing a distance measurement function by means of the light emitted by the lighting system.

[0002] In the automotive field, it is known to use pulsed light beams emitted by lighting modules of lighting systems for motor vehicles to perform given photometric functions.

[0003] Conventionally, the light source used to emit this light beam is controlled by a PWM electrical signal (PWM stands for pulse width modulation). Thus, the light source is periodically activated and deactivated by this PWM signal, resulting in the emitted light beam consisting of a series of continuous light pulses at a rate high enough that the human eye cannot distinguish them. The intensity of the emitted light beam depends on the duty cycle of this PWM signal and can therefore be controlled by adjusting this duty cycle, thereby performing a photometric function.

[0004] In addition to performing one or more photometric functions (such as daytime running lights or low beams), this type of lighting module can perform various functions. For example, the light source of the lighting module can be controlled so that the pulses of the emitted light beam transmit a data sequence. Therefore, the lighting system can be equipped with a receiving module to receive the emitted light beam (after reflection from objects near the vehicle). The computing unit of the motor vehicle can then determine the flight time of the emitted light beam after detecting the data sequence in the received light beam and thus estimate the distance separating the vehicle from the object.

[0005] In this way, the light beam can perform its original purpose, namely performing a photometric function, while allowing the lighting system to perform a ranging function, which may be particularly advantageous, for example in the context of advanced driver assistance functions or in the context of autonomous or semi-autonomous vehicles.

[0006] However, this type of system has disadvantages when the light module has to perform various photometric functions. In particular, certain functions can be performed by the same exit surface of the light module in order to ensure a harmonious luminous appearance for both functions and thus give the motor vehicle a luminous identity. This is the case, for example, for the DRL and position light functions, or even for the brake light and tail light functions (DRL stands for Daytime Running Light). These photometric functions are defined by regulations and have substantially different luminous intensities. For example, the luminous intensity of the DRL function is ten times that of the position light function. Therefore, conventionally, in order to pass from one of these functions to the other, the electrical power supplied to the light source of the light module is significantly reduced.

[0007] However, this solution is not feasible when the lighting module also performs a ranging function. Specifically, reducing the electrical power to perform the lower-power lighting function will make the system unsuitable for detecting objects located in the far field.

[0008] Therefore, there is a need for a lighting system for a motor vehicle comprising a lighting module capable of simultaneously performing two different photometric functions and a ranging function, the performance of the ranging function remaining substantially constant regardless of which photometric function is being performed.

[0009] The present invention falls within this background and is intended to meet this need.

[0010] To this end, a subject of the invention is a lighting system for a motor vehicle, comprising:

[0011] a. a transmitting module, comprising: a light emitting module capable of emitting a light beam, the spectrum of which has at least a portion in the visible spectrum; and a modulation unit capable of receiving a data sequence referred to as a modulation data sequence, and the modulation unit is arranged to modulate the emitted light beam using the received data sequence;

[0012] b. A receiving module, which can receive a light beam, wherein the receiving module includes a basic acquisition module, and the basic acquisition module includes a photodetector, which can convert the received light signal into an electrical signal.

[0013] The system according to the present invention is characterized in that: the lighting system includes a computing unit, which is capable of receiving a first instruction for emitting a given first photometric function, and is arranged to generate a first modulation data sequence with a first duty cycle when receiving the first instruction, and transmit the first modulation data sequence to the modulation unit so that the lighting module emits a first modulated light beam, and the computing unit is capable of receiving a second instruction for emitting a given second photometric function, and the computing unit is arranged to generate a second modulation data sequence with a second duty cycle different from the first duty cycle when receiving the second instruction, and transmit the second modulation data sequence to the modulation unit so that the lighting module emits a second modulated light beam.

[0014] Therefore, it should be understood that the present invention proposes that, when a first photometric function is required, the light beam emitted by the light module is modulated with a first data sequence. Thus, the first modulated light beam performs the first photometric function. The resulting light beam may, for example, be a pulsed light beam, with each pulse corresponding to one or more consecutive high values ​​of the first modulation sequence, and the interval separating two consecutive pulses corresponding to one or more consecutive low values ​​of the first modulation sequence. Each pulse of the modulated light beam is emitted at a peak luminous power, and the average luminous power of the emitted first modulated light beam is required to perform the photometric function and is therefore defined by the peak luminous power and the duty cycle of the modulation data sequence. Because the modulation sequence is cyclically generated, the emitted first modulated light beam will periodically contain this sequence while continuously performing the photometric function. Therefore, the computing unit can detect the presence of this modulation sequence in the light beam received by the receiving module based on the electrical signal converted by the photodetector, and thereby detect the presence of objects in the vehicle environment and estimate the distance of these objects from the vehicle.

[0015] The present invention further proposes that, when a second photometric function is required, the light beam emitted by the light module is modulated using another data sequence with a different duty cycle. Thus, the second modulated light beam performs the second photometric function. However, due to the change in duty cycle, the average power of the second modulated light beam corresponds to the average power required to perform this second function, without modifying the peak light power. Therefore, even when the second photometric function requires a lower light intensity than the first photometric function, the range of the ranging function can be maintained.

[0016] In the present invention, the duty cycle of a data sequence refers to the ratio between the number of high values ​​and the total length of the data sequence. In the case of a binary sequence, the duty cycle thus corresponds to the ratio between the number of bits of the binary sequence with the value "1" and the total number of bits of this sequence.

[0017] Preferably, the calculation unit is arranged to generate said first modulated data sequence and said second modulated data sequence from a same initial pseudo-random binary sequence, which pseudo-random binary sequence in particular has a maximum size.

[0018] A pseudo-random binary sequence (PRBS) is a data sequence consisting of high values ​​(i.e., "1") and low values ​​(i.e., "0"). This type of sequence has particularly advantageous properties. In particular, its autocorrelation function is at a maximum for a time shift of zero (i.e., when the sequence is compared with itself), and for any other time shift (i.e., when the sequence is compared with a time-shifted version of itself), the value of the autocorrelation function is significantly lower than this maximum value. In addition, the cross-correlation function between two pseudo-random binary sequences is substantially smaller than the maximum value of the autocorrelation functions of these sequences. Finally, this type of sequence is usually generated with the aid of a linear feedback shift register (LFSR), which produces a periodic recursive sequence whose pattern forms a pseudo-random binary sequence.

[0019] Given the autocorrelation properties of the pseudo-random binary sequence, the computing unit can estimate the value of the correlation function between the modulated sequence and the demodulated sequence extracted from the light beam received by the receiving module. The correlation function will be at its maximum for the time shift corresponding to the flight time of the modulated light beam that is transmitted, reflected, and then received, even when noise is high. Therefore, the computing unit can accurately identify the time shift associated with the maximum value of the correlation function and deduce the distance between the object that reflected the light beam and the motor vehicle. In addition, due to the cross-correlation properties, receiving a modulated light beam transmitted by an equivalent system of another motor vehicle is less likely to result in a false positive detection. Finally, it should be understood that detection is not based on a single pulse but on a complete data sequence, thereby improving the signal-to-noise ratio of the system.

[0020] Advantageously, the modulation unit is configured to control the light-emitting module so that the first and second light beams have the same peak luminous power, and the calculation unit is configured so that the first and second modulation data sequences are binary sequences, and so that the first modulation data sequence contains a different number of bits with the value "0" than the second modulation data sequence. According to this feature, increasing the number of bits with the value "0" in one of the modulation data sequences, thereby reducing its duty cycle, thus allows for an increase in the number or duration of intervals separating consecutive pulses of the corresponding modulated light beam. Consequently, the average luminous power of this light beam is reduced. Conversely, reducing the number of bits with the value "0" to increase the duty cycle allows for an increase in the number or duration of pulses of the modulated light beam, and thus an increase in its average luminous power.

[0021] Advantageously, the modulation unit is configured to generate a PWM control signal, modulate the control signal using the modulation data sequence received by the modulation unit, and control the emission of the light beam by the light module using the modulated control signal. For example, the modulation unit may be configured to convert the modulation data sequence received by the modulation unit into a modulation signal, and modulate the control signal using the modulation signal (e.g., amplitude modulation, frequency modulation, or phase modulation). In particular, the modulation unit may control the light module such that the modulated light beam is emitted only for high values ​​of the modulation data sequence received from the calculation unit, and such that the modulated light beam is emitted according to the peak light power. It should be understood that each pulse of the modulated light beam is emitted at the peak light power, and that the average light power of the emitted first or second modulated light beam required to perform the first or second photometric function is therefore defined by the peak light power, the duty cycle of the first or second modulation data sequence, and the control signal.

[0022] In one embodiment of the present invention, the calculation unit is configured so that the number of bits in the first modulated data sequence is the same as the number of bits in the second modulated data sequence. Consequently, regardless of the photometric function being performed, the acquisition time of the data sequence demodulated by the receiving module (enabling the calculation unit to detect the presence of the modulation sequence in the light beam received by the receiving module) remains constant. This feature simplifies the design of the calculation unit.

[0023] In one embodiment of the present invention, the calculation unit is arranged to generate a first initial pseudo-random binary sequence and to generate a second initial sequence by cyclic sampling of the first initial sequence. Where appropriate, the calculation unit is arranged to combine the first initial sequence and a second initial sequence that has undergone a cyclic shift of a first shift using an "exclusive-or" function to generate a first modulated data sequence, and to combine the first initial sequence and a second initial sequence that has undergone a cyclic shift of a second shift different from the first shift using an "exclusive-or" function to generate a second modulated data sequence. The first and second modulation sequences thus generated are so-called "Kasami" sequences belonging to the same group of Kasami sequences, which contain a large number of sequences whose mutual correlation is minimized and whose number of "0"s varies between sequences. Therefore, the choice of which shift to apply to the second initial sequence makes it possible to control the number of "0"s of the modulation sequence, it being understood that the larger the shift, the more the number of "0"s is reduced.

[0024] Advantageously, the calculation unit is configured such that a first duty cycle of the first modulated data sequence is greater than a duty cycle of the second modulated data sequence. In particular, provision can be made for the duty cycle of the second modulated data sequence to be reduced tenfold relative to the first duty cycle. Consequently, the first modulated light beam can perform a photometric function having a luminous intensity substantially greater than the luminous intensity of the photometric function performed by the second modulated light beam.

[0025] In one embodiment of the present invention, the lighting module includes a light source, and the modulation unit is configured to control the light source to emit a first modulated light beam from the lighting module upon receiving a first modulation data sequence, and to control the light source to emit a second modulated light beam from the lighting module upon receiving a second modulation data sequence. In other words, the same light source, and possibly the same optical unit, is used to selectively emit the first modulated light beam and the second modulated light beam.

[0026] In one embodiment of the present invention, the lighting module is capable of emitting a first light beam whose spectrum has a wavelength in the visible light domain, particularly between 400 nm and 500 nm. Advantageously, the light source comprises a semiconductor generator capable of emitting a primary light beam whose spectrum particularly has a wavelength in the visible light domain, and a photoluminescent element capable of converting the primary light beam to obtain the light beam. Where appropriate, the modulation unit can be configured to control the light source of the lighting module, particularly the power supplied to the light source, in order to modulate the light beam.

[0027] The semiconductor may be, for example, gallium nitride (GaN), which is capable of emitting blue light through electroluminescence in response to an electric current passing through the semiconductor. The photoluminescent element may be, for example, in the form of a resin comprising cerium-doped yttrium aluminum garnet (CE:YAG), capable of absorbing blue light and emitting yellow light through photoluminescence in response to excitation by this light. The photoluminescent element is placed on the generator so that some of the blue light excites the element, causing it to emit orange light through photoluminescence. The remainder of the blue light passes through the element. Thus, when the light source is powered, it simultaneously emits blue and yellow light in proportion, so that the resulting light appears white to the human eye.

[0028] Thus, the light source may be a laser source, a light emitting diode, a vertical cavity surface emitting laser (VCSEL) or even a superluminescent diode (SLED).

[0029] Advantageously, the lighting module may comprise an optical unit arranged to project the light emitted by the light source so as to form said light beam.

[0030] In one embodiment of the present invention, a receiving module comprises a plurality of elementary acquisition modules, each of which comprises at least one photodetector capable of converting its received optical signals into electrical signals. Advantageously, the plurality of elementary acquisition modules are arranged in a matrix array. For example, the photodetectors of a given elementary acquisition module can collectively form a sensor, such as a single electronic component. Again for example, each photodetector, or each of the plurality of photodetectors, can have a width and / or length of less than approximately ten microns, which enables a elementary acquisition module having a reception field of at most 0.1° and thus improves the spatial resolution of the receiving module.

[0031] Advantageously, the photodetector of the or each basic acquisition module is a single-photon avalanche diode (SPAD). The SPADs can thus together form a silicon photomultiplier (SiPM). This type of photodetector is capable of detecting the incidence of single photons with high gain (e.g., a gain of the order of 106) and thus compensating for a reduction in the signal-to-noise ratio due to external conditions.

[0032] According to an example of an embodiment of the present invention, the receiving module may include an optical unit arranged in front of the basic acquisition module.

[0033] In one embodiment of the invention, the calculation unit is arranged to determine the flight time separating the emission of the emitted first modulated light beam or the second modulated light beam and the reception of the light beam received by the receiving module based on the electrical signal converted by the photodetector from the received light beam.

[0034] Advantageously, the light emitting system comprises a demodulation unit connected to the photodetector and arranged to extract a data sequence, referred to as a demodulated data sequence, from the electrical signal converted by the photodetector. Where appropriate, the calculation unit is capable of receiving the data sequence demodulated by the demodulation unit from the electrical signal converted by the photodetector from the light beam received by the receiving module, and is arranged to estimate the value of a correlation function between the demodulated data sequence and the first modulated data sequence or the second modulated data sequence, and to determine the flight time separating the emission of the emitted first modulated light beam or the second modulated light beam from the reception of the received light beam based on the value of the correlation function.

[0035] Each value of the correlation function estimated by the calculation unit is associated with a time-shifted value of the modulated data sequence or demodulated data sequence used to estimate the value of the correlation function. Therefore, the correlation function between the demodulated data sequence and the modulated data sequence depends on the autocorrelation of the modulated data sequence.

[0036] It is thus possible to detect the presence of this modulated data sequence in the received light beam after reflection from an object in the vehicle's environment and thus detect the presence of this object and estimate its distance from the vehicle.

[0037] Preferably, the calculation unit is arranged to determine a peak value of the correlation function, compare the peak value with a predetermined threshold value, and detect the presence of the modulated data sequence in the demodulated data sequence based on the comparison. For example, the calculation unit may conclude that the modulated data sequence is present in the demodulated data sequence only if the peak value is greater than the predetermined threshold value.

[0038] For example, the basic acquisition module or each basic acquisition module is capable of generating a basic detection signal based on one or more electrical signals converted by one or more photodetectors of the basic acquisition module, and each basic acquisition module is arranged to compare the basic detection signal with a threshold value associated with the basic acquisition module and generate a data sequence called a demodulated data sequence based on the comparison.

[0039] In particular, it is conceivable that each elementary acquisition module comprises a comparator arranged to compare the elementary detection signal with the threshold value associated with the elementary acquisition module and to generate the demodulated data sequence based on the comparison. The comparator thus forms a unit for demodulating the light beam received by the receiving module, capable of extracting a data sequence, referred to as the demodulated data sequence, from the electrical signal converted by the photodetector. As a variant, it is possible to provide for replacing the comparator with an active circuit.

[0040] In one embodiment of the present invention, each basic acquisition module comprises a plurality of photodetectors and at least one electronic component arranged to generate the basic detection signal according to the sum of the electrical signals converted by the photodetectors.

[0041] In one example of an embodiment of the present invention, the transmitting module is arranged in a headlamp of a motor vehicle. Preferably, the receiving module and the transmitting module are arranged in the same headlamp of the vehicle.

[0042] Advantageously, the lighting module is arranged such that the first modulated light beam contributes entirely or partially to performing a first photometric adjustment function corresponding to the first instruction, and the second modulated light beam contributes entirely or partially to performing a second photometric adjustment function corresponding to the second instruction. Preferably, the lighting intensity of the second photometric adjustment function can be significantly lower than the lighting intensity of the first photometric adjustment function.

[0043] Likewise advantageously, the lighting module is arranged such that the first modulated light beam contributes completely or partially to performing the first signaling function of "daytime running light" and such that the second modulated light beam contributes completely or partially to performing the second signaling function of "position light".

[0044] Another subject matter of the invention is a method for detecting obstacles in the environment of a motor vehicle and for estimating the distance separating such objects from the vehicle, the method being implemented by the lighting system according to the invention.

[0045] The present invention will now be described using examples, which are illustrative only and in no way limitative of the scope of the invention, and with reference to the accompanying drawings, in which the figures show:

[0046] [ Figure 1 ] shows schematically and partially a view of a distance measurement system for a motor vehicle according to one example of an embodiment of the present invention;

[0047] [ Figure 2 ] schematically and partially shows [ Figure 1 An example of the operation of a system of ] during implementation of a ranging method;

[0048] [ Figure 3 ] schematically and partially shows the [ Figure 1 ]'s ranging system generates various data sequences during its operation.

[0049] In the following description, unless otherwise specified, elements that are identical in structure or function and appear in the various figures are marked with the same reference numerals. Of course, various other modifications are possible to the invention within the scope of the appended claims.

[0050] [ Figure 1 ] shows a system 1 of a motor vehicle according to one example of embodiment of the invention. The vehicle's distance measuring system 1 comprises a transmitting module 2 capable of transmitting a light beam F1, a receiving module 3 intended to receive a light beam F2, and a calculation unit 4.

[0051] In the example described, the transmitting module 2 and the receiving module 3 are arranged in the same headlamp of the motor vehicle. Provision can be made, without departing from the scope of the present invention, to arrange the modules 2 and 3 at different locations in the motor vehicle.

[0052] The emission module 2 comprises a light emitting module 21 capable of emitting a light beam F1 and a modulation unit 22 capable of receiving a modulation data sequence Seq_m, the modulation unit being arranged to modulate the emitted light beam F1 using said modulation sequence Seq_m.

[0053] The light emitting module 21 is arranged so that the light beam F1 it emits has an electromagnetic spectrum, at least a portion of which is in the visible spectrum. Preferably, the spectrum of this light beam F1 has an intensity peak or spectral line in the blue at 450 nm. It should be noted that the spectrum has other intensity peaks in the visible and / or infrared light.

[0054] In the case where the light beam F1 is partially or entirely composed of white light, this light beam can be used to partially or entirely participate in the performance of a plurality of predetermined (in particular, regulating) photometric functions, as will be described below. In this case, the lighting module 21 can include an optical unit arranged to shape this light beam F1 so that its photometric distribution meets the requirements of any of these functions.

[0055] In addition to this photometric function, the light beam F1 allows the system 1 to perform functions of detecting and evaluating the position of obstacles on the road and / or communicating with other vehicles or with the road infrastructure.

[0056] To this end, the modulation unit 22 is arranged to use the modulation data sequence Seq_m it receives to modulate the light beam F1 emitted by the light module 21 , for example by controlling the electrical power supplied to the light source of the light module.

[0057] Therefore, it can be provided that the modulation unit 22 comprises a generator of a PWM control signal (PWM stands for Pulse Width Modulation). This control signal makes it possible to control a switched-mode power supply (not shown) of the light source of the lighting module 21. Conventionally, the duty cycle of this control signal set by the modulation unit 22 thus allows the average electrical power supplied to the light source to be controlled, and therefore the luminous intensity of the light beam F1 to meet the requirements of the photometric function performed by this light beam.

[0058] In the example described, the modulation unit 22 is arranged to convert the data sequence Seq_m into a modulation signal and to modulate the initial control signal using this modulation signal. It should be noted that any of a number of different types of modulation may be employed within the scope of the present invention, in particular on-off keying (OOK), pulse code modulation (PCM), pulse amplitude modulation (PAM), pulse width modulation (PWM), or even pulse position modulation (PPM).

[0059] The emitted light beam F1 is thus composed of a series of continuous light pulses whose rate is high enough (for example, higher than 30 MHz, in particular between 50 MHz and 100 MHz) for the human eye to no longer be able to distinguish them. Furthermore, the amplitude, width and / or position of each pulse relative to the period allow the light beam F1 to transmit the data sequence Seq_m.

[0060] If there is an object in the environment of the motor vehicle, this object can reflect this light beam F1 towards the receiving module 3 , which thus receives the light beam F2 .

[0061] This receiving module 3 comprises a plurality of elementary acquisition modules 32i,j. Each elementary acquisition module 32i,j comprises a plurality of photodetectors 32ak,l, each of which is capable of converting the optical signal it receives into an electrical signal Selk,l. Each elementary acquisition module 32i,j also comprises a demodulation unit 34, which comprises a comparator, the input of which is connected in parallel to all the outputs of the photodetectors 32ak,l. The comparator thus receives an elementary detection signal Sdei,j, formed by the sum of the electrical signals Selk,l delivered by the photodetectors 32ak,l. The comparator is arranged to compare this elementary detection signal Sdei,j with a given threshold value. This comparison yields a high value, or "1," when the elementary detection signal is greater than the threshold value, and a low value, or "0," when the elementary detection signal is less than the threshold value. The demodulation unit 34 is thus arranged to generate a demodulated binary sequence Seq_di,j, which it transmits to the calculation unit 4. As a variant, it can be provided that the comparator of the demodulation unit 34 is replaced by an active circuit, in which case the demodulated data sequence is a digital sequence formed directly from "1"s and "0".

[0062] In the example described, the photodetectors 32ak,l are identical and each consists of a single-photon avalanche photodiode, or SPAD, integrated into a silicon photomultiplier, or SiPM, along with the demodulation unit 34. It should be noted that the dimensions of the photodetectors are of the order of one micron. Thus, due to the use of avalanche photodiodes, this assembly forms a sensor with a spatial resolution of reception of the order of 1° or even 0.1°, and a particularly high detection capability even under degraded acquisition conditions.

[0063] The calculation unit 4 is able to receive the demodulated binary sequences Seq_di,j generated by the elementary acquisition modules 32i,j and to detect the presence of the modulated data sequence Seq_m in each demodulated binary sequence Seq_di,j. The demodulation unit 34 thus makes it possible to reduce the amount of data that must be manipulated by the calculation unit and thus achieve compression of the elementary detection signals Sdei,j.

[0064] To this end, the calculation unit 4 is therefore arranged to estimate the values ​​of the correlation function Fcorri,j between each demodulated binary sequence Seq_di,j and said modulated data sequence Seq_m and, based on these values ​​of the correlation function Fcorri,j, to detect the presence of the modulated data sequence Seq_m in this demodulated binary sequence Seq_di,j. In the event of detection of its presence, it can then determine the flight time τ separating the emission of said emitted modulated light beam F1 and the reception of said received light beam F2.

[0065] The calculation unit 4 is thus able to perform the functions of detecting and evaluating the position of objects on the road, as will be seen in reference [ Figure 2 ] described, the figure shows the ranging method implemented by the light-emitting system 1.

[0066] As indicated above, the lighting module 21 is able to selectively perform various functions, such as a DRL first function (DRL stands for Daytime Running Lights) and a “position light” second function, through the same exit surface.

[0067] In order to be able to activate one or the other of these functions, the calculation unit 4 receives, in a step E0 , an instruction for emitting one or the other of these first and second photometric functions.

[0068] This instruction will originate, for example, from a central computer of the motor vehicle (not shown) and be determined by the central computer, for example based on traffic parameters of the motor vehicle, based on information from various sensors such as a camera filming the road, a steering wheel angle sensor or a navigation system.

[0069] Depending on the received instruction, the calculation unit determines the duty cycle τ1 or τ2 according to the photometric function indicated by this instruction, and generates a first modulated data sequence Seq_m1 or a second modulated data sequence Seq_m2.

[0070] To this end, in a step E0 ′, the calculation unit generates an initial pseudo-random binary sequence Seq0 of maximum size.

[0071] Next, in step E1, the computing unit periodically generates:

[0072] a. the first modulated data sequence Seq_m1 from the initial sequence Seq0, the first modulated data sequence having a first duty cycle τ1;

[0073] b. or the second modulated data sequence Seq_m2 from the initial sequence Seq0, the second modulated data sequence having a second duty cycle τ2.

[0074] It should be noted that regardless of the duty cycle τ1 or τ2, the number of bits in the first modulated data sequence Seq_m1 is the same as the number of bits in the second modulated data sequence Seq_m2. Furthermore, considering the photometric function that the light module 21 must perform, the value of the first duty cycle τ1 is greater than the value of the second duty cycle τ2. Specifically, the value of the first duty cycle is 10 times the value of the second duty cycle. In other words, the number of bits with a value of "0" in the first sequence Seq_m1 is greater than the number of bits with a value of "0" in the second sequence Seq_m2.

[0075] The calculation unit 4 transmits the modulation data sequence Seq_m1 or Seq_m2 thus generated to the modulation unit 22 of the transmission module 2 , so that the transmission module 2 transmits the light beam F1 or F1 ′.

[0076] In a second step E2 , the modulation unit 22 modulates the light beam emitted by the light emitting module 21 based on the data sequence Seq_m1 or Seq_m2 to obtain a modulated light beam F1 or F1 ′.

[0077] It should be noted that, in the example described, each light pulse of the light beam F1 or F1 ′ emitted by the light module 21 corresponds to a bit of the modulation sequence Seq_m1 or Seq_m2 having the value “1”. Therefore, the average power of the portion of the light beam F1 / F1 ′ containing the sequence Seq_m1 or Seq_m2 is defined by the number of bits of this sequence Seq_m1 or Seq_m2 having the value “1” relative to the total number of bits of this sequence, the duration of the pulses, and the peak power Pp of these pulses.

[0078] Given that the peak luminous power Pp remains the same for each data sequence Seq_m1 or Seq_m2, the average power of light beam F1 modulated by the first sequence Seq_m1 is substantially greater than the average power of light beam F1' modulated by the second sequence Seq_m2. Specifically, taking into account the relative values ​​of duty cycles τ1 and τ2, the first light beam F1 includes more light pulses and / or longer light pulses than the second light beam F1'. Consequently, light beam F1 can perform a relatively high-intensity photometric function (such as a daytime running light), while light beam F1' can perform a dimmer photometric function (such as a position light), without affecting the peak luminous power Pp of the pulses.

[0079] The light beam F1 / F1 ′ is thus emitted and then reaches an object O located in the vehicle's surroundings, which reflects the light beam in the direction of the receiving module 3 .

[0080] Depending on the angular position of the object O, the light beam F2 received by the receiving module 3 is thus concentrated on the elementary acquisition module 32 i,j One of the above.

[0081] When the sunlight conditions near the vehicle are particularly bright, sunlight is therefore added to the light beam F2 received by the receiving module 3. Therefore, the light beam F2 received by the receiving module 3 is composed of a portion of the light beam F1 / F1' reflected by the object O and noise, for example, noise generated by parasitic light sources such as city lighting, car lighting or even the sun.

[0082] In the third step E3, each basic acquisition module 32 i,j The demodulated binary sequence Seq_d is thus extracted by means of its demodulation unit 34 i,j , the demodulation unit transmits the demodulated binary sequence to the calculation unit 4.

[0083] For each demodulated binary sequence Seq_d received i,j The calculation unit 4 estimates in a fourth step E4 the difference between the modulation sequence Seq_m1 or Seq_m2 used to modulate the emitted light beam F1 / F1' and the demodulated binary sequence Seq_d i,j The correlation function Fcorr i,j The value of .

[0084] It should be noted that, as long as these modulation sequences Seq_m1 or Seq_m2 contain the same number of bits, the acquisition time of the demodulated data sequence remains constant whatever the photometric function performed by the emitted light beam F1 / F1 ′.

[0085] Therefore, the calculation unit 4 uses each demodulated binary sequence Seq_d i,j The cross-correlation of multiple time shifts is evaluated by performing circular convolution with the modulation sequence Seq_m1 or Seq_m2 delayed by each time shift.

[0086] Given the autocorrelation and cross-correlation characteristics of the modulation sequence, the correlation function Fcorr i,j Therefore, for the time of flight of the light beam F1 (i.e., the time between the time when the transmitting module 2 transmits the light beam and the time when the basic acquisition module 32 of the receiving module 3 i,j The time shift corresponding to the time length of the received light beams will be the largest, and the modulation sequence Seq_m1 or Seq_m2 delayed by this time shift therefore substantially corresponds to the demodulated binary sequence Seq_d i,j , ignoring any noise.

[0087] In a fifth step E5 , the calculation unit 4 identifies the i,j Each associated correlation function Fcorr i,j The maximum value Fcorr_max is obtained and compared with the threshold value Vs.

[0088] In the case where the maximum value Fcorr_max is greater than the threshold value Vs, the modulation sequence Seq_m1 or Seq_m2 is considered to be the modulation sequence generated by the calculation unit 4 by the correlation function Fcorr i,j Associated basic acquisition module 32 i,j Delivered demodulated binary sequence Seq_d i,j Therefore, in the basic acquisition module 32 i,j An object O is detected within the monitored angular range or pixel and the calculation unit 4 can then estimate in a sixth step E6 the value τ of the time of flight of the emitted light beam F1 / F1' between the object O and the vehicle associated with this maximum value, and also the distance d separating the object O from the vehicle.

[0089] refer to[ Figure 3 ], an example of an embodiment of a calculation unit will now be described which allows the generation of modulation sequences Seq_m1 and Seq_m2 having autocorrelation and cross-correlation characteristics that meet the needs of the present invention and whose duty cycle can be controlled.

[0090] The calculation unit 4 pregenerates a first initial pseudo-random binary sequence having a maximum size Seq0, for example, by means of a linear feedback shift register.

[0091] The calculation unit 4 then generates a second initial sequence Seq0' by cyclically sampling the first initial sequence. Thus, each bit of the second initial sequence Seq0' has the value of a bit of the first initial sequence Seq0, the rank of which corresponds to the rank of the bit of the second initial sequence to be calculated multiplied by a coefficient calculated based on the length of the first initial sequence Seq0, modulo this length.

[0092] Therefore, the second initial sequence Seq0' undergoes a cyclic shift of a value Δ1 when calculating the first modulation sequence Seq_m1, and undergoes a cyclic shift of a value Δ2 when calculating the second modulation sequence Seq_m2. The value Δ2 will be greater than the value Δ1 to ensure that the number of "0"s in the second modulation sequence Seq_m2 is greater than the number of "0"s in the first modulation sequence Seq_m1.

[0093] Finally, the calculation unit combines the cyclic shifts (Δ1) of the first initial sequence Seq0 and the second initial sequence Seq0' using an "exclusive-OR" function to generate a first modulated data sequence Seq_m1, and combines the cyclic shifts (Δ2) of the first initial sequence Seq0 and the second initial sequence Seq0' to generate a second modulated data sequence Seq_m2. Therefore, these first modulated sequence Seq_m1 and second modulated sequence Seq_m2 are so-called "Kasami" sequences belonging to the same group of Kasami sequences.

[0094] The foregoing description clearly explains how the present invention achieves the objectives set forth, namely, to provide a lighting system comprising a lighting module capable of simultaneously performing two different photometric functions and a ranging function, the performance of the ranging function remaining substantially constant regardless of the photometric function being performed. These objectives are achieved in particular by configuring the value of the duty cycle of the data sequence modulating the light beam emitted by the lighting module according to the photometric function that the lighting module must perform.

[0095] In any case, the present invention is not limited to the embodiments specifically described in this document and extends in particular to all equivalent devices and to any technically operative combination of these devices. In particular, it is possible to provide that the transmission module has another configuration, in particular that the transmission module uses light source types other than those described, such as laser diodes, VCSELs, SLEDs, or RGB diodes. It is also possible to implement photometric functions other than those described, in particular low-beam lighting functions or brake or taillight signaling functions. It is even possible to use methods for generating modulation sequences other than those described.

Claims

1. A lighting system (1) for a motor vehicle, the lighting system comprising: a. a transmitting module (2), comprising: a light emitting module (21), capable of emitting a light beam (F1, F1'), the spectrum of which has at least a portion in the visible spectrum; and a modulation unit (22), capable of receiving a data sequence referred to as a modulation data sequence (Seq2a, Seq2b), and arranged to modulate the emitted light beam using the received data sequence; b. a receiving module (3), the receiving module being capable of receiving a light beam (F2), wherein the receiving module comprises a basic acquisition module (32), the basic acquisition module comprising a photodetector, the photodetector being capable of converting the received light signal into an electrical signal (Sel); The light-emitting system is characterized in that the light-emitting system includes a computing unit (4), which is capable of receiving a first instruction for emitting a given first photometric function, and is arranged to generate a first modulation data sequence (Seq2a) having a first duty cycle when receiving the first instruction, and transmit the first modulation data sequence to the modulation unit (22), so that the light-emitting module (21) emits a first modulated light beam (F1), and the computing unit is capable of receiving a second instruction for emitting a given second photometric function, and is arranged to generate a second modulation data sequence (Seq2b) having a second duty cycle different from the first duty cycle when receiving the second instruction, and transmit the second modulation data sequence to the modulation unit (22), so that the light-emitting module (21) emits a second modulated light beam (F1').

2. Lighting system (1) according to the preceding claim, characterized in that The modulation unit is arranged to control the light-emitting module so that the first light beam and the second light beam have the same peak light-emitting power, and the calculation unit is arranged so that the first modulation data sequence and the second modulation data sequence are binary sequences, and so that the number of bits with a value of "0" contained in the first modulation data sequence is different from the number of bits with a value of "0" in the second modulation data sequence.

3. Lighting system (1) according to the preceding claim, characterized in that The calculation unit is arranged to make the number of bits of the first modulated data sequence the same as the number of bits of the second modulated data sequence.

4. The distance measuring system (1) as claimed in any one of the preceding claims, characterized in that The calculation unit (4) is arranged to generate a first initial pseudo-random binary sequence, generate a second initial sequence by cyclically sampling the first initial sequence, combine the first initial sequence and the second initial sequence that has undergone a cyclic shift of a first shift by using an "exclusive-OR" function to generate the first modulated data sequence, and combine the first initial sequence and the second initial sequence that has undergone a cyclic shift of a second shift different from the first shift by using an "exclusive-OR" function to generate the second modulated data sequence.

5. The lighting system (1) as claimed in any one of the preceding claims, characterized in that The calculation unit (4) is arranged to make a first duty cycle of the first modulated data sequence (Seq2a) greater than a duty cycle of the second modulated data sequence (Seq2b).

6. Lighting system (1) according to any one of the preceding claims, characterized in that The light emitting module (21) includes a light source (23), and the modulation unit (22) is arranged to control the light source so that the light emitting module emits the first modulated light beam (F1) when the first modulation data sequence is received, and to control the light source (23) so that the light emitting module emits the second modulated light beam (F1') when the second modulation data sequence is received.

7. The lighting system (1) as claimed in any one of the preceding claims, characterized in that The calculation unit is arranged to determine the flight time (τ) separating the emission of the emitted first modulated light beam or the second modulated light beam and the reception of the light beam received by the receiving module (3) based on the electrical signal converted from the received light beam by the photodetector.

8. Lighting system (1) according to the preceding claim, characterized in that The light emitting system comprises a demodulation unit (33) connected to the photodetector and arranged to extract a data sequence (Seq3) called a demodulated data sequence from the electrical signal (Sel) converted by the photodetector, and the calculation unit (4) is capable of receiving the data sequence demodulated by the demodulation unit from the electrical signal, the electrical signal being converted by the photodetector from the light beam (F2) received by the receiving module (3), the calculation unit being arranged to estimate the value of a correlation function (Fcorr) between the demodulated data sequence and the first modulated data sequence or the second modulated data sequence (Seq2a), and to determine the flight time (τ) separating the emission of the emitted first modulated light beam or the second modulated light beam (F1) and the reception of the received light beam based on the value of the correlation function.

9. The lighting system (1) as claimed in any one of the preceding claims, characterized in that The transmitting module (2) is arranged in a headlight of the motor vehicle.

10. Lighting system (1) according to the preceding claim, wherein The lighting module (21) is arranged so that the first modulated light beam (F1) contributes completely or partially to performing a first adjustment photometric function corresponding to the first instruction, and so that the second modulated light beam (F1) contributes completely or partially to performing a second adjustment photometric function corresponding to the second instruction.

11. Lighting system (1) according to the preceding claim, wherein The lighting module (21) is arranged so that the first modulated light beam (F1) fully or partially contributes to performing a first signaling function of "daytime running light", and the second modulated light beam (F1) fully or partially contributes to performing a second signaling function of "position light".

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