Detection system for a motor vehicle comprising a module for emitting a light beam and a module for receiving the light beam - Patent 7222247

Abstract

The present invention relates to a lighting system (1) for a motor vehicle comprising a light emitting module (2) having a lighting module (21) and a modulation unit (22), and a light receiving module (3) for receiving a light beam (F2), characterized in that the lighting system comprises a calculation unit (4) for receiving a first command to emit a first photometric function, the calculation unit being configured to generate a first modulation data sequence (Seq2a) having a first duty factor, and the calculation unit is capable of receiving a second command to emit a given second photometric function, and is configured to generate a second modulation data sequence (Seq2b) having a second duty factor different from the first duty factor.

Description

[Technical Field]

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

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

[0003] Conventionally, the light source emitting this light beam is controlled by a PWM electrical signal (PWM stands for pulse width modulation). The light source is thus periodically enabled and deactivated by this PWM signal, and the emitted light beam therefore consists of a series of light pulses that follow one after the other so quickly that they are indistinguishable by the human eye. The intensity of the emitted light beam depends on the duty cycle of this PWM signal, and it is therefore possible to control said intensity by adjusting this duty cycle of the PWM signal, thereby performing a photometric function.

[0004] In addition to the performance of one or more photometric functions, such as daytime running lights or low beams, various other functions may be performed by this type of lighting module. For example, the light source of the lighting module may be controlled so that the pulses of the emitted light beam transmit a data sequence. Therefore, the lighting system may be equipped with a reception module for receiving the emitted light beam after reflection from an object near the vehicle. Then, after detecting the data sequence in the received light beam, a computing unit of the automotive vehicle may determine the time-of-flight of the emitted light beam and thereby estimate the distance separating the vehicle from the object.

[0005] In this way, the light beam may perform its original role, i.e., photometric function, while at the same time enabling the lighting system to perform ranging functions, 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 drawbacks when the lighting module must perform various photometric functions. Specifically, certain functions may be performed through the same light output surface of the lighting module to ensure a harmonious lighting appearance for these two functions, thus giving the vehicle a distinctive lighting character. This is the case, for example, for DRL (Daytime Running Light) and position light functions, or even stop and tail light functions. These photometric functions are defined by regulations and have substantially different luminous intensities. For example, the DRL function has 10 times the luminous intensity of the position light function. Therefore, the power supplied to the lighting module's light source is typically significantly reduced to transition from one of these functions to the other.

[0007] However, this solution is not possible if the lighting module also performs a ranging function, especially since reducing the power to perform a low-power lighting function makes the system unsuitable for detecting objects located at long distances.

[0008] Therefore, there is a need for an automotive vehicle lighting system that includes a lighting module that is capable of simultaneously performing two different photometry and distance measurement functions, where the performance of the distance measurement function remains substantially constant regardless of which photometry function is performed. Summary of the Invention [Problem to be solved by the invention]

[0009] The present invention is within this context and aims to meet this need. [Means for solving the problem]

[0010] For these purposes, one subject of the present invention is a. an emission module comprising: an illumination module capable of emitting a light beam, the spectrum of the light beam having at least a portion within the visible spectrum; and a modulation unit capable of receiving a data sequence, referred to as a modulation data sequence, and configured to modulate the emitted light beam using the received data sequence; b. a light receiving module capable of receiving a light beam, the light receiving module comprising an elementary acquisition module having a photodetector capable of converting a received light signal into an electrical signal; A lighting system for an automobile vehicle, comprising:

[0011] The system according to the present invention is characterized in that the lighting system for an automotive vehicle is capable of receiving a first command to emit a given first photometric function and comprises a calculation unit configured, upon receiving the first command, to generate a first modulation data sequence having a first duty cycle and to transmit the first modulation data sequence to a modulation unit for emitting a first modulated light beam by the lighting module; and the calculation unit is capable of receiving a second command to emit a given second photometric function and is configured, upon receiving the second command, to generate a second modulation data sequence having a second duty cycle different from the first duty cycle and to transmit the second modulation data sequence to the modulation unit for emitting a second modulated light beam by the lighting module.

[0012] It will be appreciated that the present invention can modulate the light beam emitted by the lighting module with a first data sequence when a first photometric function is required. In this manner, the first modulated light beam performs the first photometric function. The resulting light beam can be, for example, a pulsed beam, with each pulse corresponding to one or more successive high values ​​of the first modulation sequence and the interval separating two successive pulses corresponding to one or more successive low values ​​of the first modulation sequence. Each pulse of the modulated light beam is emitted at a peak illumination output, and the average illumination output of the emitted first modulated light beam is required to perform the photometric function and is therefore defined by the peak illumination output and the duty cycle of the modulation data sequence. The modulation sequence is generated periodically, so that the emitted first modulated light beam periodically includes this sequence while continuously performing the photometric function. Therefore, the calculation unit may detect the presence of this modulation sequence in the beam received by the light receiving module based on the electrical signal converted by the photodetector, thereby detecting the presence of an object in the vehicle's surroundings and estimating its distance from the vehicle.

[0013] The present invention further provides a method for modulating the light beam emitted by the illumination module with a different data sequence at a different duty cycle when a different photometric function is required. In this manner, the second modulated light beam performs a second photometric function. However, due to the change in duty cycle, the average power of the second modulated beam corresponds to the power required to perform this second function, and the peak illumination power does not need to be modified. Therefore, even if the second photometric function requires a lower light intensity than the first photometric function, the range of the ranging function may remain unchanged.

[0014] 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. Thus, if the data sequence is a binary sequence, the duty cycle corresponds to the ratio between the number of bits with value "1" in the binary sequence and the total number of bits in this sequence.

[0015] Preferably, the calculation unit is configured to generate said first modulated data sequence and said second modulated data sequence from the same initial pseudo-random binary sequence, the pseudo-random binary sequence being of a particular maximum size.

[0016] A pseudo-random binary sequence (PRBS) is a data sequence consisting of high values, or "1," and low values, or "0." This type of sequence has particularly advantageous properties. Specifically, its autocorrelation function is maximum when the time shift is zero, i.e., when the sequence is compared to itself, and has values ​​substantially lower than this maximum when the sequence is compared to a time-shifted version of itself. Furthermore, the cross-correlation function between two pseudo-random binary sequences is substantially lower than the maximum of the autocorrelation functions of these sequences. Finally, this type of sequence is typically generated using a linear feedback shift register (LFSR), which creates a periodic, recursive sequence whose pattern forms the pseudo-random binary sequence.

[0017] Considering the autocorrelation properties of the pseudorandom binary sequence, the computation unit may estimate the value of a correlation function between the modulated sequence and the demodulated sequence extracted from the light beam received by the light receiving module. The correlation function will be maximized for a time shift corresponding to the time of flight of the modulated light beam emitted, reflected, and then received, even in the presence of high noise. As a result, the computation unit may accurately identify this time shift associated with the correlation function maximum and infer therefrom the distance separating the object from which the beam was reflected and the automotive vehicle. Furthermore, considering the cross-correlation properties, reception of a modulated light beam emitted by an equivalent system on another automotive vehicle is unlikely to lead to a false detection. Finally, it will be appreciated that detection is based on the complete data sequence, rather than a single pulse, thereby improving the signal-to-noise ratio of the system.

[0018] Advantageously, the modulation unit is configured to control the lighting module so that the first and second light beams have the same peak illumination output, and the calculation unit is configured so that the first and second modulation data sequences are binary sequences and the first modulation data sequence includes a different number of "0" bits than the number of "0" bits in the second modulation data sequence. According to this feature, by increasing the number of "0" bits in one of the modulation data sequences to decrease the duty cycle of that sequence, it is possible to increase the number or duration of intervals separating successive pulses of the corresponding modulated light beam, thus decreasing the average illumination output of that beam. Conversely, by decreasing the number of "0" bits to increase the duty cycle, it is possible to increase the number or duration of pulses of the modulated light beam, thus increasing the average illumination output.

[0019] Advantageously, the modulation unit is configured to generate a PWM control signal using the received modulation data sequence to modulate the control signal, and to use the modulated control signal to control the emission of the light beam by the lighting module. For example, the modulation unit may be configured to convert the received modulation data sequence into a modulation signal and use this modulation signal to modulate (e.g., amplitude, frequency, or phase) the control signal. Specifically, the modulation unit may control the lighting module to emit the modulated light beam only when the value of the modulation data sequence received from the calculation unit is high, and to emit the modulated light beam according to the peak illumination power. It will therefore be understood that each pulse of the modulated light beam is emitted at the peak illumination power, and that the average illumination power of the emitted first or second modulated light beam required to perform the first or second photometric function is defined by the peak illumination power, the duty cycle of the first or second modulation data sequence, and the control signal.

[0020] In one embodiment of the present invention, the calculation unit is configured such that the number of bits of the first modulated data sequence is the same as the number of bits of the second modulated data sequence. Therefore, the acquisition time of the data sequence demodulated by the light receiving module remains constant regardless of the photometric function being performed, so that the calculation unit can detect the presence of the modulated data sequence in the beam received by the light receiving module. This feature can therefore simplify the design of the calculation unit.

[0021] In one embodiment of the present invention, the computing unit is configured to generate a first initial pseudo-random binary sequence and a second initial sequence by cyclic sampling of the first initial sequence. Where appropriate, the computing unit is configured to generate a first modulated data sequence by combining the first initial sequence with a second initial sequence after being cyclically shifted by a first shift using an "exclusive-or" function, and to generate a second modulated data sequence by combining the first initial sequence with a second initial sequence after being cyclically shifted by a second shift different from the first shift using an "exclusive-or" function. The first and second modulated data sequences thus generated are so-called "Kasami" sequences, which belong to the same set of Kasami sequences and include a number of sequences with minimal cross-correlation and a varying number of "0s" per sequence. Therefore, by selecting which shift is applied to the second initial sequence, it is possible to control the number of "0s" in the modulated sequence; it will be understood that the larger the shift, the fewer the number of "0s."

[0022] Advantageously, the calculation unit is configured such that the first modulated data sequence has a first duty cycle that is greater than the duty cycle of the second modulated data sequence. In particular, the duty cycle of the second modulated data sequence may be reduced by a factor of 10 relative to the first duty cycle. Thus, the first modulated light beam may perform a photometric function whose luminous intensity is substantially greater than the luminous intensity of the photometric function performed by the second modulated light beam.

[0023] In one embodiment of the invention, the lighting module comprises a light source, and the modulation unit is configured to control the light source for emitting a first modulated light beam by the lighting module upon receiving a first modulation data sequence, and to control the light source for emitting a second modulated light beam by 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 for selectively emitting the first and second modulated light beams.

[0024] In one embodiment of the present invention, the lighting module is capable of emitting a first light beam, the spectrum of which has wavelengths in the visible range, in particular between 400 nm and 500 nm. Advantageously, the light source comprises a semiconductor generator capable of emitting a fundamental light beam, the spectrum of which has wavelengths in the visible range, in particular, and a photoluminescent element capable of converting said fundamental light beam to obtain said light beam. Where appropriate, the modulation unit may be configured to control the light source of the lighting module, in particular the power supply transmitted to this light source, so as to modulate the light beam.

[0025] The semiconductor may be, for example, gallium nitride (GaN), capable of emitting blue light by electroluminescence and in response to an electric current passing therethrough. The photoluminescent element may be, for example, in the form of a resin containing cerium-doped yttrium aluminum garnet (CE:YAG), capable of absorbing blue light and emitting yellow light by photoluminescence and in response to excitation by this light. The photoluminescent element is placed on the generator so that a portion of the blue light excites the element, causing it to emit orange light by photoluminescence. The remaining blue light passes through the element. Thus, when the light source is powered, it simultaneously emits blue and yellow light in such a ratio that the resulting light appears white to the human eye.

[0026] 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 (SLD).

[0027] Advantageously, the lighting module may comprise an optical unit configured to project light rays emitted by the light source to form said light beam.

[0028] In one embodiment of the present invention, the light receiving module comprises a plurality of elementary acquisition modules, each of which comprises at least one photodetector capable of converting the received optical signal into an electrical signal. Advantageously, the plurality of elementary acquisition modules are arranged in a matrix array. For example, the photodetectors of a given elementary acquisition module may be combined to form a sensor, e.g., a single electronic component. Also, for example, each photodetector or each of the plurality of photodetectors may have a width and / or length of less than approximately 10 microns, which allows obtaining a basic acquisition module with a receiving field of view of up to 0.1°, thus improving the spatial resolution of the light receiving module.

[0029] Advantageously, the photodetector of the or each elementary acquisition module is a single-photon avalanche diode (SPAD), which may therefore together form a silicon photomultiplier (SiPM). Photodetectors of this type are able to detect the incidence of single photons with a high gain, for example of the order of 10, and are therefore able to compensate for the degradation of the signal-to-noise ratio due to external conditions.

[0030] According to an example embodiment of the present invention, the light receiving module may comprise an optical unit arranged in front of the basic acquisition module.

[0031] In one embodiment of the present invention, the calculation unit is configured to determine, based on the electrical signal converted by the photodetector from the received light beam, a time of flight separating the emission of the emitted first or second modulated light beam from the reception of the light beam received by the light receiving module.

[0032] Advantageously, the illumination system comprises a demodulation unit connected to the photodetector and configured to extract a data sequence, referred to as a demodulated data sequence, from the electrical signal converted by the photodetector. Where appropriate, a 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 light receiving module, the calculation unit being configured to estimate a value of a correlation function between said demodulated data sequence and said first or second modulated data sequence, and to determine, based on the value of the correlation function, a time of flight separating the emission of said first or second emitted modulated light beam from the reception of said received light beam.

[0033] Each value of the correlation function estimated by the calculation unit is associated with the value of one of the time shifts of the modulated or demodulated data sequence employed to estimate this value of the correlation function, and thus the correlation function between the demodulated and modulated data sequences depends on the autocorrelation of the modulated data sequence.

[0034] Thus, by detecting the presence of this modulated data sequence in the received light beam after reflection from an object in the vehicle's surroundings, it is possible to detect the presence of this object and estimate its distance from the vehicle.

[0035] Preferably, the calculation unit is configured to determine a peak value of the correlation function, compare the peak value with a predetermined threshold, and detect the presence of the modulated data sequence in the demodulated data sequence based on the comparison. The calculation unit may, for example, conclude that the modulated data sequence is present in the demodulated data sequence only if the peak value is greater than a predetermined threshold.

[0036] For example, the or each basic acquisition module may be capable of generating a basic detection signal in response to one or more electrical signals converted by one or more photodetectors of the basic acquisition module, and each basic acquisition module is configured to compare said basic detection signal with a threshold value associated with said basic acquisition module and to generate a data sequence, referred to as a demodulated data sequence, based on said comparison.

[0037] In particular, it is conceivable that each elementary acquisition module comprises a comparator configured to compare the elementary detection signal with the threshold value associated with this elementary acquisition module and to generate the demodulated data sequence based on said comparison. The comparator thus forms a unit for demodulating the light beam received by the light receiving module, making it possible to extract a data sequence, called demodulated data sequence, from the electrical signal converted by the photodetector. As a variant, the comparator can also be replaced by an active circuit.

[0038] In one embodiment of the present invention, each elementary acquisition module comprises a plurality of photodetectors and at least one electronic component configured to generate said elementary detection signal in terms of the sum of electrical signals converted by said photodetectors.

[0039] In one embodiment of the present invention, the light-emitting module is disposed in a front headlamp of an automobile vehicle. Preferably, the light-receiving module and the light-emitting module are disposed in the same front headlamp of the vehicle.

[0040] Advantageously, the lighting module is configured such that the first modulated light beam contributes wholly or partly to the performance of a first regulatory photometric function corresponding to a first command, and the second modulated light beam contributes wholly or partly to the performance of a second regulatory photometric function corresponding to a second command. Preferably, the luminous intensity of the second regulatory photometric function may be substantially lower than the luminous intensity of the first regulatory photometric function.

[0041] Also advantageously, the lighting module is configured such that the first modulated light beam contributes wholly or partly to performing a first signaling function of "daytime running lights", and the second modulated light beam contributes wholly or partly to performing a second signaling function of "position lights".

[0042] Another subject of the invention is a method for detecting an obstacle located in the surroundings of a motor vehicle and for estimating the distance separating this object from the vehicle, the method being implemented by a lighting system according to the invention.

[0043] The present invention will now be described, by way of example only, with reference to the accompanying drawings, which do not limit the scope of the invention. [Brief explanation of the drawings]

[0044] [Figure 1] 1 is a diagram illustrating a schematic and partial view of a ranging system for an automotive vehicle according to an example embodiment of the present invention; [Figure 2] 2 shows a schematic and partial view of an example of the operation of the system of FIG. 1 during the implementation of a ranging method; [Figure 3] 2A and 2B show schematic and partial views of various data sequences generated by the calculation unit of the ranging system of FIG. 1 during its operation; DETAILED DESCRIPTION OF THE INVENTION

[0045] In the following description, elements that are identical in structure or function and that appear in various figures are designated by the same reference numerals unless otherwise specified. Naturally, various other modifications may be made to the present invention within the scope of the appended claims.

[0046] [Fig. 1] shows a system 1 for an automobile vehicle according to an embodiment of the present invention. The vehicle ranging system 1 comprises a light emitting module 2 capable of emitting a light beam F1, a light receiving module 3 intended to receive a light beam F2, and a calculation unit 4.

[0047] In the example described, the light-emitting module 2 and the light-receiving module 3 are arranged in the same front headlamp of the motor vehicle. It is also possible for the modules 2 and 3 to be arranged in different positions within the motor vehicle without departing from the scope of the present invention.

[0048] The light emitting module 2 comprises an illumination module 21 capable of emitting a light beam F1 and a modulation unit 22 capable of receiving a modulation data sequence Seq_m and configured to modulate the emitted light beam F1 using said modulation sequence Seq_m.

[0049] The lighting module 21 is configured so that the light beam F1 it emits has an electromagnetic spectrum at least partly located within the visible spectrum. Preferably, the spectrum of this light beam F1 has an intensity peak or intensity line in the blue at 450 nm. It should be noted that the spectrum may have other intensity peaks in the visible and / or infrared.

[0050] Insofar as the light beam F1 is partially or entirely composed of white light, it can be employed to partially or entirely participate in the performance of several predetermined, in particular regulatory, photometric functions, as will be explained below, in which case the illumination module 21 may comprise an optical unit configured to shape this light beam F1 so that the photometric distribution of this light beam F1 meets the requirements of any one of these functions.

[0051] In addition to this photometry function, the light beam F1 enables the system 1 to perform the function of detecting and assessing the position of obstacles on the road and / or the function of communicating with another vehicle or road infrastructure.

[0052] For these purposes, the modulation unit 22 is configured to use the modulation data sequence Seq_m received by the modulation unit 22 to modulate the light beam F1 emitted by the lighting module 21, for example by controlling the power supplied to the light source of the lighting module.

[0053] The modulation unit 22 may therefore comprise a generator of a PWM control signal (PWM stands for pulse width modulation) which makes it possible to control the 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, makes it possible to control the average power supplied to the light source and therefore the luminous intensity of the light beam F1 so as to meet the requirements of the photometric function that the light beam F1 performs.

[0054] In the described example, the modulation unit 22 is configured 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 within the scope of the present invention, various types of modulation may be employed, in particular on-off-keying (OOK), pulse-code modulation (PCM), pulse-amplitude modulation (PAM), pulse-width modulation (PWM) or even pulse-position modulation (PPM).

[0055] The light beam F1 thus emitted consists of a train of successive light pulses that follow one another at a rate sufficiently high to be indistinguishable by the human eye, for example, higher than 30 MHz, in particular between 50 MHz and 100 MHz, and furthermore, the amplitude, width and / or position of each pulse relative to the period enable the light beam F1 to carry a data sequence Seq_m.

[0056] If an object is present around the motor vehicle, the object may reflect this light beam F1 towards the light receiving module 3, which in this way receives the light beam F2.

[0057] The light receiving module 3 comprises a number of elementary acquisition modules 32i,j. Each elementary acquisition module 32i,j comprises a number of photodetectors 32ak,l capable of converting the optical signal it receives into an electrical signal Sel,l. Each elementary acquisition module 32i,j further comprises a demodulation unit 34 with a comparator, the inputs of which are connected in parallel to the outputs of all the photodetectors 32ak,l. The comparator receives an elementary detection signal Sdei,j formed by the sum of the electrical signals Sel,l transmitted by these photodetectors 32ak,l. The comparator is configured to compare this elementary detection signal Sdei,j with a given threshold value, and the comparison result is a high value, i.e., "1", if the elementary detection signal is greater than the threshold value, and a low value, i.e., "0", if the elementary detection signal is less than the threshold value. The demodulation unit 34 is thus configured to generate a demodulated binary sequence Seq_di,j and transmit it to the calculation unit 4. Alternatively, the comparators of the demodulation unit 34 can be replaced by active circuits, in which case the demodulated data sequence is a digital sequence formed directly by "1"s and "0"s.

[0058] In the described example, the photodetectors 32a,l are identical and are each formed by a single-photon avalanche photodiode (SPAD), and these photodiodes and the demodulation unit 34 are integrated in a silicon photomultiplier tube (SiPM). It should be noted that the dimensions of the photodetectors are on the order of 1 micron. In this way, the assembly forms a sensor with a spatial resolution of reception on the order of 1°, or even 0.1°, and, thanks to the use of avalanche photodiodes, a particularly high detection capacity even under adverse acquisition conditions.

[0059] The calculation unit 4 receives the demodulated binary sequences Seq_di,j generated by the elementary acquisition modules 32i,j and is able 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 has to be processed by the calculation unit, thus achieving a compression of the elementary detection signals Sdei,j.

[0060] For these purposes, the calculation unit 4 is therefore configured to estimate the value 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 a modulated data sequence Seq_m in this demodulated binary sequence Seq_di,j. If detected, the calculation unit 4 may then determine the time of flight τ separating the emission of said emitted modulated light beam F1 from the reception of said received light beam F2.

[0061] In this way, the calculation unit 4 is able to perform the function of detecting and assessing the position of objects on the road, as will be explained with reference to [Figure 2], which shows the ranging method implemented by the lighting system 1.

[0062] As indicated above, the lighting module 21 can selectively perform various functions through the same emission surface, such as a first function called DRL (DRL stands for Daytime Running Light) and a second function called "position light."

[0063] To be able to activate either of these functions, the calculation unit 4 receives, in step E0, a command to activate either of these first and second photometric functions.

[0064] This command may originate, for example, from a central computer (not shown) in the vehicle and may be determined by the central computer based on information from various sensors, such as traffic parameters of the vehicle, cameras photographing the road, steering wheel angle sensors, or navigation systems.

[0065] In response to the received command, the calculation unit determines the duty cycle τ1 or τ2 according to the photometric function indicated by the command, and generates the first modulation data sequence Seq_m1 or the second modulation data sequence Seq_m2.

[0066] For these purposes, the calculation unit generates, in a step E0', an initial pseudorandom binary sequence Seq0 of maximum size.

[0067] Next, in step E1, the calculation unit periodically generates either: a. Generate the first modulated data sequence Seq_m1 from an initial sequence Seq0, where the first modulated data sequence has a first duty cycle τ1. b. Generate the second modulated data sequence Seq_m2 from the initial sequence Seq0, where the second modulated data sequence has a second duty cycle τ2.

[0068] It should be noted that the number of bits in the first modulation data sequence Seq_m1 is the same as the number of bits in the second modulation data sequence Seq_m2, regardless of whether the duty cycle is τ1 or τ2. Furthermore, considering the photometric function that the lighting module 21 must perform, the value of the first duty cycle τ1 is greater than the value of the second duty cycle τ2, specifically by a factor of 10. In other words, the number of bits of the value "0" in the first sequence Seq_m1 is greater than the number of bits of the value "0" in the second sequence Seq_m2.

[0069] The calculation unit 4 transmits the modulation data sequence Seq_m1 or Seq_m2 thus generated to the modulation unit 22 of the light emitting module 2 for the purpose of emitting a light beam F1 or F1' by the light emitting module 2.

[0070] In a second step E2, the modulation unit 22 modulates the light beam emitted by the lighting module 21 on the basis of this data sequence Seq_m1 or Seq_m2 to obtain a modulated light beam F1 or F1'.

[0071] It should be noted that in the described example, each light pulse of the light beam F1 or F1′ emitted by the lighting module 21 corresponds to a bit of value “1” in the modulation sequence Seq_m1 or Seq_m2. The average power of the portion of the light beam F1 / F1′ comprising the sequence Seq_m1 or Seq_m2 is therefore defined by the relationship between the number of bits of value “1” in this sequence Seq_m1 or Seq_m2 and the total number of bits in this sequence, the duration of the pulses and the peak power Pp of these pulses.

[0072] Thus, as long as the peak illumination power Pp of each of the data sequences Seq_m1 or Seq_m2 is the same, the average power of the light beam F1 modulated by the first sequence Seq_m1 will be substantially greater than the average power of the light beam F1' modulated by the second sequence Seq_m2. Specifically, due to the relative values ​​of the duty cycles τ1 and τ2, this first beam F1 will contain more light pulses and / or longer light pulses than the second beam F1'. Thus, without affecting the peak illumination power Pp of the pulses, the light beam F1 may perform a fairly high-intensity photometric function, such as a daytime running light, while the light beam F1' may perform a weaker photometric function, such as a position light.

[0073] The light beam F1 / F1' is thus emitted and reaches an object O located in the vehicle's surroundings, which reflects it towards the light receiving module 3.

[0074] Thus, depending on the angular position of the object O, the light beam F2 received by the light receiving module 3 is reflected by the elementary acquisition module 32 i,j It is concentrated in one of the

[0075] Therefore, if the lighting conditions in the vicinity of the vehicle are particularly bright, sunlight is added to the light beam F2 received by the light receiving module 3. The light beam F2 received by the light receiving module 3 is therefore composed of a part of the light beam F1 / F1' reflected by the object O and noise, e.g. noise generated by parasitic light sources such as city lighting, vehicle lighting or even the sun.

[0076] In a third step E3, the basic acquisition module 32 i,j Each of the binary numbers Seq_d is thus demodulated using its demodulation unit 34. i,j and the demodulation unit 34 sends it to the calculation unit 4.

[0077] The calculation unit 4 therefore calculates for each demodulated binary sequence Seq_d received i,j In the fourth step E4, 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 between i,j Estimate the value of .

[0078] 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 regardless of what photometric function is performed by the emitted light beams F1 / F1'.

[0079] The calculation unit 4 therefore calculates for each demodulated binary sequence Seq_d i,jThe cross-correlation for multiple time shifts is evaluated using a circular convolution product between the modulated sequence Seq_m1 or Seq_m2 delayed by each time shift.

[0080] Considering the autocorrelation and cross-correlation properties of the modulation sequence, the correlation function F i,j is therefore the time of flight of the light beam F1, i.e. the time when the light beam is emitted by the light emitting module 2 and the time when the light beam is received by the elementary acquisition module 32 of the light receiving module 3. i,j The modulation sequence Seq_m1 or Seq_m2 delayed by this shift is the demodulated binary sequence Seq_d, ignoring noise. i,j corresponds substantially to

[0081] In a fifth step E5, the calculation unit 4 calculates the value of each elementary acquisition module 32 i,j Each correlation function Fcorr associated with i,j The maximum value Fcorr_max of is identified and compared to a threshold Vs.

[0082] If this maximum value Fcorr_max is greater than the threshold Vs, the basic acquisition module 32 associated with this correlation function Fcorr_j i,j The demodulated binary sequence Seq_d transmitted by i,j In this case, it is assumed that the modulation sequence Seq_m1 or Seq_m2 is detected by the calculation unit 4. Therefore, this basic acquisition module 32 i,j and the calculation unit 4 may then, in a sixth step E6, estimate 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 the distance d separating the object O from the vehicle.

[0083] An example of an embodiment of a calculation unit that allows the generation of modulation sequences Seq_m1 and Seq_m2, whose duty cycle can be controlled and which have autocorrelation and cross-correlation properties that meet the needs of the present invention, will now be described with reference to [Figure 3].

[0084] The computation unit 4 pre-generates a first initial pseudo-random binary sequence Seq0 of maximum size, for example using a linear feedback shift register.

[0085] The calculation unit 4 then generates the second initial number sequence Seq0' by cyclic sampling of the first initial number sequence, so that each bit of the second initial number sequence Seq0' has the value of one bit of the first initial number sequence Seq0, and its rank corresponds to the value obtained by multiplying the rank corresponding to the rank of the bit of the second initial number sequence to be calculated by a coefficient calculated according to the length of the first initial number sequence Seq0, modulo the length of the first initial number sequence Seq0.

[0086] This second initial sequence Seq0' is circularly shifted by a value Δ1 in the calculation of the first modulation sequence Seq_m1 and by a value Δ2 in the calculation of the second modulation sequence Seq_m2, the value Δ2 being 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.

[0087] Finally, the calculation unit uses an "exclusive OR" function to combine the first initial sequence Seq0 with the circular shift (Δ1) of the second initial sequence Seq0' to generate a first modulated data sequence Seq_m1, and combines the first initial sequence Seq0 with the circular shift (Δ2) of the second initial sequence Seq0' to generate a second modulated data sequence Seq_m2. Therefore, the first modulated sequence Seq_m1 and the second modulated sequence Seq_m2 belong to the same Kasami number sequence set, and are so-called "Kasami" sequences.

[0088] The above description clearly explains how the present invention achieves the objectives of providing an illumination system with an illumination module capable of simultaneously performing two different photometric and distance measurement functions, with the performance of the distance measurement function remaining substantially constant regardless of the performance of the photometric function. These objectives are achieved in particular by setting the value of the duty cycle of the data sequence modulating the light beam emitted by the illumination module depending on the photometric function that the illumination module is to perform.

[0089] In any case, the present invention is not limited to the embodiments specifically described herein, but in particular extends to all equivalent means and any technically functional combinations of these means. In particular, it is possible for the light-emitting module to have other configurations, in particular for the light-emitting module to employ other types of light sources than those described, such as laser diodes, VCSELs, SLEDs, or RGB diodes. It is also possible for photometric functions other than those described to be performed, in particular low-beam lighting functions or stop-light or tail-light signaling functions. Furthermore, it is also possible to use methods for generating modulation sequences other than those described.

Claims

1. a lighting module (21) capable of emitting a light beam (F1, F1'), the spectrum of which has at least a portion within the visible spectrum, and a modulation unit (22) capable of receiving data sequences, referred to as modulation data sequences (Seq2a, Seq2b), and configured to modulate the emitted light beam using the received data sequences; b) a light receiving module (3) capable of receiving the light beam (F2), said light receiving module comprising an elementary acquisition module (32) equipped with a photodetector capable of converting the received light signal into an electrical signal (Sel); A lighting system (1) for a motor vehicle, comprising: the lighting system (1) for the motor vehicle is capable of receiving a first command to emit a given first photometric function, and is configured, upon receiving the first command, to generate a first modulation data sequence (Seq2a) having a first duty cycle and to transmit the first modulation data sequence to the modulation unit (22) for the purpose of emitting a first modulated light beam (F1) by the lighting module (21); 1. A lighting system (1) for an automotive vehicle, wherein the calculation unit is capable of receiving a second command to emit a given second photometric function, and wherein the calculation unit is configured, upon receiving the second command, to generate a second modulation data sequence (Seq2b) having a second duty cycle different from the first duty cycle and to transmit the second modulation data sequence to the modulation unit (22) for the purpose of emitting a second modulated light beam (F1′) by the lighting module (21).

2. 2. The lighting system (1) of claim 1, characterized in that the modulation unit is configured to control the lighting modules such that the first and second light beams have the same peak lighting output, and the calculation unit is configured such that the first and second modulation data sequences are binary sequences and such that the first modulation data sequence includes a number of bits with value "0" that is different from a number of bits with value "0" in the second modulation data sequence.

3. 3. The lighting system (1) according to claim 2, characterized in that the calculation unit is configured such that the number of bits of the first modulation data sequence is the same as the number of bits of the second modulation data sequence.

4. 4. The ranging system according to claim 1, wherein the calculation unit is configured to: generate a first initial pseudo-random binary sequence and a second initial sequence by cyclic sampling of the first initial sequence; generate the first modulated data sequence by combining, using an "exclusive-or" function, the first initial sequence with the second initial sequence after being cyclically shifted by a first shift; and generate the second modulated data sequence by combining, using an "exclusive-or" function, the first initial sequence with the second initial sequence after being cyclically shifted by a second shift different from the first shift.

5. 5. The lighting system (1) according to claim 1, wherein the calculation unit (4) is configured such that the first modulation data sequence (Seq2a) has a first duty cycle that is greater than the duty cycle of the second modulation data sequence (Seq2b).

6. 6. The lighting system (1) according to claim 1, wherein the lighting module (21) comprises a light source (23), and the modulation unit (22) is configured to control the light source (23) for the purpose of emitting the first modulated light beam (F1) by the lighting module upon receiving the first modulation data sequence, and to control the light source (23) for the purpose of emitting the second modulated light beam (F1') by the lighting module upon receiving the second modulation data sequence.

7. 7. The lighting system (1) according to any one of claims 1 to 6, characterized in that the calculation unit is configured to determine, based on the electrical signal converted by the photodetector from the received light beam, a time of flight (τ) separating the emission of the emitted first or second modulated light beam from the reception of the light beam received by the light receiving module (3).

8. 8. The lighting system (1) according to claim 7, characterized in that the lighting system (1) comprises a demodulation unit (33) connected to the photodetector and configured to extract a data sequence (Seq3), called demodulated data sequence, from the electrical signal (Seq1) converted by the photodetector, the calculation unit (4) being able to receive the data sequence demodulated by the demodulation unit from the electrical signal converted by the photodetector from the light beam (F2) received by the light receiving module (3), the calculation unit being configured to estimate a value of a correlation function (Fcorr) between the demodulated data sequence and the first or second modulated data sequence (Seq2a) and to determine, based on the value of the correlation function, a time of flight (τ) separating the emission of the first or second emitted modulated light beam (F1) from the reception of the received light beam.

9. 9. The lighting system (1) according to any one of claims 1 to 8, characterized in that the light emitting module (2) is arranged in a front headlamp of the motor vehicle.

10. 10. The lighting system (1) of claim 9, wherein the lighting module (21) is configured such that the first modulated light beam (F1) contributes wholly or partially to the execution of a photometric function on a first rule corresponding to the first command, and the second modulated light beam (F1) contributes wholly or partially to the execution of a photometric function on a second rule corresponding to the second command.

11. 11. The lighting system (1) of claim 10, wherein the lighting module (21) is configured such that the first modulated light beam (F1) contributes wholly or partly to performing a first signaling function of "daytime running light" and the second modulated light beam (F1) contributes wholly or partly to performing a second signaling function of "position light".

Images