Telemetry optical system for automated vehicles with light-emitting module for light beam

Abstract

The present invention relates to an optical system (1) for an automated vehicle, the system comprising a light-emitting module (2) having an optical module (21) and a control unit (22), wherein the optical module (21) comprises a first light source (23a) capable of emitting a first light beam (Fia) having a spectrum (Sl) with a first peak (P1) at a wavelength shorter than the intermediate wavelength, and a second light source (23b) capable of emitting a second light beam (Flb) having a spectrum (S2) with a second peak (P2) at a wavelength longer than the intermediate wavelength, the intermediate wavelength being longer than 490 nm, the control unit (22) configured to control the first and second light sources to emit the first and second light beams simultaneously, the control unit comprising a modulation unit (22a) capable of receiving a data sequence (Seq), the modulation unit (22a) configured to modulate the emitted first light beam based on the received data sequence.

Description

[Technical Field]

[0001] The present invention relates to the field of lighting and / or light signaling for automated vehicles, and functions for detecting objects by automated vehicles and calculating the distance between the object and the vehicle. More precisely, the present invention relates to lighting and / or signaling systems for automated vehicles that can perform telemetry functions by emitting light. [Background technology]

[0002] In the field of autonomous vehicles, it is a known practice to use pulsed light beams emitted by optical modules of optical systems for autonomous vehicles to perform a given photometric function.

[0003] Conventionally, light sources used to emit this light beam are controlled by pulse-width modulated (PWM) electrical signals. Thus, the light source is periodically activated and deactivated by this PWM signal. This is because the emitted light beam consists of multiple light pulses, but the intervals between these pulses are at a frequency high enough that they are no longer distinguishable to the human eye. The intensity of the emitted light beam depends on the duty cycle of this PWM signal, and by adjusting this duty cycle, the intensity can be controlled, thus enabling the performance of photometric functions.

[0004] In addition to performing one or more photometric functions (e.g., daytime running lights or low-beam illumination), this type of optical module can perform a variety of functions. For example, the light source of the optical module can be controlled to carry a data sequence by pulses of the emitted light beam. A light receiving module can then be installed in the optical system to receive the emitted light beam after it has been reflected from an object near the vehicle. The computing unit of the automated vehicle can then determine the flight time of the emitted light beam (after detecting the data sequence in the received light beam), and thus determine a numerical value for the distance between the vehicle and the object.

[0005] In this way, the light beam can maintain its original function (i.e., perform photometric functions) while enabling the optical system to perform telemetry functions. This can be particularly advantageous, for example, for driver assistance functions and in situations of automatic or semi-automated driving.

[0006] However, this type of system, based on the use of a light-emitting module capable of performing both photometric illumination and data transmission, has drawbacks. Specifically, the light-receiving module intended to receive the light beam carrying the data, whether located in the same vehicle or in a different vehicle, must be equipped with at least one photodetector to convert this light beam into an electrical signal. This is for demodulating the signal and extracting the data sequence from it.

[0007] However, under certain conditions, considering the sources of stray light in the vehicle's environment (e.g., urban lighting, automatic vehicle lighting from oncoming or following vehicles, or even sunlight) and the properties of various objects in that environment (especially their reflectivity), this photodetector can have a significantly degraded signal-to-noise ratio. This degradation of the signal-to-noise ratio can reduce the accuracy of the calculation unit in determining the distance from the target object, or even lead to false detections.

[0008] In this situation, the decision was made to use specific frequencies where normalized sunlight is less bright or even nonexistent. This is particularly true for the blue wavelength range between 430nm and 460nm in the visible spectrum. Therefore, if the light source of the light-emitting module emits a light beam with a peak at one of these wavelengths, it is possible to use a filter in the light-receiving module that blocks the wavelength band where sunlight is too bright, leaving only a narrowed bandwidth centered on this emitted wavelength (where sunlight is less bright). This improves the signal-to-noise ratio.

[0009] However, this solution is not entirely satisfactory. Specifically, the photometric function must meet legal requirements, particularly in terms of luminous intensity (luminous flux) and color. For example, daytime running lights (DRLs) are legally limited to a maximum luminous intensity of 1200 cd and must consist of white light. Typically, a light-emitting diode (LED) with a blue light generator is used, with a phosphorescent element associated with the blue light generator that can convert some of this blue light into yellow light. White light is then formed by additive color mixing of the remaining blue light and the yellow light.

[0010] However, the blue component of this light accounts for only about 30% of its energy (in other words, radiometric analysis, i.e., relative to the total energy of the light), and less than 10% (i.e., relative to the energy of the portion of the light visible to the human eye, weighted by the sensitivity curve of the human eye). The power of this blue component may be insufficient for detection under poor lighting conditions or at long distances. One solution to maintain a sufficient signal-to-noise ratio would be to increase the luminous intensity power of each pulse of the emitted light beam. However, this solution would lead to an enhancement of both the blue and yellow components of the emitted light beam, and therefore an enhancement of the average power of the emitted light beam. This would be unsuitable for performing the intended photometric function. Another solution would be to increase the number of light sources, but this solution is rather incompatible with the compactness and cost requirements imposed in the field of lighting and light signaling for automated vehicles. [Overview of the Initiative]

[0011] Thus, there is a need for an optical system for automated vehicles that can perform both a given legally defined photometric function and a telemetry function, is efficient, and has an optimal signal-to-noise ratio in all weather conditions, including bright sunlight.

[0012] This invention aims to satisfy this need within the scope of this context.

[0013] To that end, the present invention relates to an optical system for an automated vehicle, comprising a light-emitting module including an optical module and a control unit, wherein the optical module includes a first light source capable of emitting a first light beam having a first peak in a spectrum below an intermediate wavelength, and a second light source capable of emitting a second light beam having a second peak in a spectrum above an intermediate wavelength, the intermediate wavelength being 490 nm or greater, and the control unit is designed to control the first and second light sources to emit the first and second light beams simultaneously, and the control unit includes a modulation unit capable of receiving a data sequence, the modulation unit is designed to modulate the emitted first light beam based on the received data sequence.

[0014] An intermediate wavelength of 490 nm is advantageous. Alternatively, the intermediate wavelength may be longer than 490 nm to encompass the wavelength corresponding to blue-green light. If applicable, an intermediate wavelength of 510 nm, preferably 500 nm, is preferable.

[0015] Blue-green light can be used, for example, to perform a signaling function for autonomous driving mode.

[0016] The present invention thus proposes decomposing a light beam intended to perform a photometric function into two light beams. These light beams include a first light beam having a spectrum that is substantially blue when the first light source generally emits blue light, and substantially blue-green when the first light source generally emits blue-green light. Thus, considering the spectral profile of light emitted by the sun in particular, it becomes possible to perform telemetry functions with an excellent signal-to-noise ratio.

[0017] The first light beam is, for example, a pulsed beam, where each pulse corresponds to one or more consecutive highs in the data sequence, and the interval between two consecutive pulses corresponds to one or more consecutive lows in the data sequence. Each pulse of the modulated first light beam is emitted with a peak luminous power such that the average luminous power of the modulated and emitted first light beam is thus determined by the peak luminous power and the duty cycle of the modulated data sequence (the data sequence for modulation). Thus, detecting the presence of this data sequence in the first light beam after reflection from an object in the vicinity of the vehicle makes it possible to detect the presence of this object and calculate its distance from the vehicle.

[0018] The second light beam has a spectrum with a peak in the visible range, which complements the spectrum of the first light beam so that a whole light beam of white light is produced as a result of the simultaneous emission of the first and second light beams. In this invention, "simultaneous emission" should be understood as meaning that the first and second light beams perform all or part of the same photometric function together. This whole light beam performing the photometric function may result from either additive mixing of the first and second light beams, or from pulses of these first and second light beams occurring alternately at frequencies high enough to appear white to the human eye.

[0019] According to the present invention, each light beam is emitted by its own (one or more) light source. In particular, it is conceivable to use one or more light sources to emit each of the light beams. In this way, it is possible to increase the power of the pulses emitted by the (one or more) first light sources. This is to improve the efficiency and signal-to-noise ratio of the telemetry function performed by the first light beam, while adapting the power of the second light beam emitted by the (one or more) second light sources to meet the legal requirements of the photometric function performed by the overall light beam.

[0020] It is advantageous that the first light source is designed to have a first peak in the spectrum of the emitted first light beam, which falls within the range of 380 nm to 490 nm, preferably 420 nm to 460 nm, and the second light source is designed to have a second peak in the spectrum of the second light beam, which falls within the range of 520 nm to 580 nm, or even 530 nm to 555 nm. Preferably, the first light source is designed to have a full width at half maximum (FWHM) in the spectrum of the first light beam, which falls between 15 nm and 30 nm, and the second light source is designed to have a full width at half maximum in the spectrum of the second light beam, which falls between 70 nm and 140 nm. In other words, the first light source generally emits blue light, thereby significantly increasing the power of the pulses constituting the first light beam. The second light source generally emits yellow light, which generally complements the blue light. The intensities of the first and second light beams can be modulated (particularly throughout each duty cycle) to obtain a statutory white overall light beam.

[0021] It is advantageous that the first light source is designed so that the spectrum of the emitted first light beam has a first peak that falls within the range of 480 nm to 510 nm, preferably 490 nm to 500 nm, and the second light source is designed so that the spectrum of the second light beam has a second peak that falls within the range of 520 nm to 680 nm, or even 585 nm to 680 nm. Preferably, the first light source is designed so that the spectrum of the first light beam has a full width at half maximum (FWHM) that falls between 15 nm and 30 nm, and the second light source is designed so that the spectrum of the second light beam has a full width at half maximum that falls between 70 nm and 140 nm. In other words, the first light source generally emits blue-green light, thereby significantly increasing the power of the pulses constituting the first light beam. The second light source generally emits orange (e.g., yellow-orange) light that complements the blue-green light. The intensities of the first and second light beams can be modulated (particularly throughout each duty cycle) to obtain a statutory white overall light beam.

[0022] Preferably, the first light source and at least the second light source are designed such that the overlap band between their spectra is substantially zero. Alternatively, the first light source and at least the second light source are configured such that the overlap band between their spectra extends beyond a given wavelength (for example, 460 nm if the first light source generally emits blue light, or 500 nm if it generally emits blue-green light). This overlap band is, for example, the band in which the spectral power of the first and second light beams is higher than 10% of the peak spectral power of the first light beam. Such an overlap band can be considered substantially zero if its width is less than 5 nm. These characteristics ensure, in particular, that photons from the second light beam are not added to the first light beam in the portion used to perform the telemetry function of the first light beam. The photons of the second light beam may generate noise that could worsen the system's signal-to-noise ratio for performing this telemetry function, especially if the receiving module intended to perform the telemetry function is equipped with a blue filter (blue transmission filter).

[0023] In one exemplary embodiment, the first light source comprises a generator capable of emitting the first light beam, and the first light source does not have a photoluminescent element. In the case of the first light source, the generator is preferably a semiconductor generator. The semiconductor may be, for example, gallium nitride (GaN) capable of emitting blue-green light and / or blue light and / or ultraviolet light (in response to an electric current passing through it by electroluminescence).

[0024] When appropriate, the second light source may include a generator capable of emitting light rays. For example, in the case of the second light source, the generator is preferably a semiconductor generator capable of emitting yellow light, orange light, or yellow-orange light. The semiconductor may be, for example, gallium phosphide (GaP), gallium arsenide phosphide (GaAsP), or silicon carbide (SiC) that can emit light rays of yellow light, orange light, or yellow-orange light (by electroluminescence, in response to the current passing through itself).

[0025] When appropriate, the second light source may include a generator capable of emitting light rays and a photoluminescence element capable of absorbing most of the light rays and emitting a second light beam. As an example, the semiconductor may be, for example, gallium nitride (GaN) that can emit light rays of blue-green light and / or blue light and / or ultraviolet light (by electroluminescence, in response to the current passing through itself). When appropriate, the semiconductor and / or the addition ratio of the semiconductor may be different between the first and second light sources so that the peak of the spectrum of the first light beam is distinct from the peak of the spectrum of the second light beam.

[0026] As an example, the photoluminescence element may be in the form of a resin containing garnet, silicate, aluminate, oxynitride, quantum dot particles, or perovskite (scheelite) that can absorb blue-green light, blue light, or ultraviolet light and (by photoluminescence, in response to excitation by this light) emit light rays of yellow light. The photoluminescence element is arranged on the generator of the second light source so that most of the light rays of blue light or ultraviolet light excite this element and (by photoluminescence) emit light rays of orange light. Thus, when the light source is supplied with power, it mainly emits light rays of yellow light, orange light, or yellow-orange light.

[0027] Thus, the light source may be a laser light source, a light-emitting diode, a vertical cavity surface emitting laser (VCSEL), or a superluminescent diode (SLED).

[0028] As a variant, the second light source may include a plurality of light elements each capable of emitting light rays of different colors (particularly, red or green). Changing the luminous intensity of each of these light elements can be used to change the color of the second light beam. Thereby, the first light beam can be supplemented so that the overall light beam becomes white.

[0029] In one embodiment, the control unit includes a drive unit for supplying power to the second light source, and the control unit is designed to control the drive unit using a pulse-width modulated signal (pulse-width modulated signal) having a duty cycle higher than the duty cycle of the received data sequence. The duty cycle of the data sequence is determined, for example, by the ratio between the number of high values and the total length of the data sequence. In the present invention, the first light source is controlled at a high frequency such that the pulses forming the first light beam follow at a frequency exceeding 100 kHz or exceeding 1 MHz, whereas the second light source is controlled at a low frequency of about 1 kHz. A high duty cycle is used such that the pulses of the second light beam have a time range sufficient for the overall light beam resulting from the first and second light beams to appear white to the human eye.

[0030] It is advantageous that the control unit is designed to determine the duty cycle of the pulse-width modulated signal from at least the duty cycle of the received data sequence and the peak power setting value of the pulse group forming the first light beam. In particular, the control unit may be designed to determine the duty cycle of the pulse-width modulated signal from the duty cycle of the received data sequence, the peak power setting value of the pulse group forming the first light beam, and the setting value of the photometric function intended to be brought about at least partially by the first and second light beams.

[0031] In one embodiment, the optical module comprises an optical unit capable of receiving first and second light beams, the optical unit having a common emission surface for the first and second light beams. The emission surface should be understood as a virtual wall, surface, or portion of the optical unit through which the first and second light beams are emitted. Thus, the optical unit may include lenses, light guides, reflectors, or some combination of these optical elements. In this embodiment, the optical unit thus is a common optical unit designed to project and / or deflect and / or shape the light rays emitted by the first and second light sources to form the first and second light beams.

[0032] In an exemplary embodiment of the present invention, the optical unit comprises a light guide having at least one coupling surface for first and second light beams, the guide being designed so that the light rays coupled through the coupling surface propagate within the guide by internal total internal reflection. Where appropriate, the guide comprises a decoupling element capable of separating the coupling of light rays propagating within the guide toward a common exit surface, and the guide comprises a mixing section between the coupling surface and the decoupling element for the first and second light beams coupled to the light guide. This mixing section is used to spatially homogenize the color of the overall light beam, so that this color and the illuminated appearance of the light guide meet the statutory requirements of the photometric function intended to be performed by the overall light beam.

[0033] The light guide has a generally cylindrical shape, and it is advantageous that the cross-section of the mixing portion of the guide is polygonal. The cross-section of the guide in the mixing portion may have, for example, a square or hexagonal profile. These shapes are used in particular to optimize the mixing of the first and second light beams.

[0034] The light guide may have an elliptical or circular cross-section (at the level of the main portion having a common exit surface), and the decoupling element may have a prism and / or diffuser and / or protrusions formed on at least the wall of the main portion opposite to the exit surface. The light guide may, for example, have a connecting portion between the mixing portion and the main portion. This connecting portion is designed to continuously connect the polygonal cross-section of the mixing portion to the elliptical or circular portion of the main portion.

[0035] As an example of a modification, the cross-section of the mixing section may be identical to the cross-section of the main section of the light guide, which has a common exit surface, and the length of the cross-section of the mixing section may be sufficient for the first and second light beams to mix along this section.

[0036] In another exemplary embodiment, the light guide may have the form of a guide sheet (light guide plate) with a coupling member (e.g., a collimator). Rays coupled to the sheet via the coupling member propagate through total internal reflection from the opposing walls of the guide sheet until they reach a decoupling member. The decoupling member is designed to deflect these rays toward a common exit surface of the guide sheet. Where appropriate, the mixing portion may be a translucent portion of the guide sheet, a diffusing member provided on the walls of the guide sheet, or a portion of the guide sheet without a decoupling member, as long as is sufficient to mix the first and second light beams.

[0037] The system is advantageous in that it comprises at least two first light sources, the first and second light sources facing the same coupling plane of the light guide, and the first light sources may surround the second light sources. For example, the system may comprise a plurality of first light sources aligned along a first direction and a plurality of second light sources aligned along a separate second direction intersecting the plurality of first light sources. As a variation, the first light sources may (completely or partially) surround one or more second light sources. These various configurations also promote the mixing of the first and second light beams within the light guide.

[0038] It is advantageous that the dimensions of the second light source may exceed those of the first light source.

[0039] In one embodiment of the present invention, the system comprises a light-receiving module capable of receiving a light beam, the light-receiving module comprising at least one basic capture module having a photodetector capable of converting the received light signal into an electrical signal. Where appropriate, the system comprises a computing unit designed to generate a modulated data sequence and to send the modulated data sequence to a modulation unit to emit a first light beam modulated by the light module, the computing unit being designed to determine the time of flight between the emission of the modulated and emitted first light beam and the reception of the light-receiving beam, from the electrical signal converted by the photodetector based on the light-receiving beam received by the light-receiving module.

[0040] The light-receiving module is advantageous to have multiple basic capture modules arranged in a matrix, each equipped with a photodetector capable of converting the received optical signal into an electrical signal. For example, a set of photodetectors can form a sensor, such as a single electronic component. Also, for example, each photodetector may have a width and / or length of less than approximately 10 microns. This makes it possible to obtain a basic capture module with a light-receiving range of at most 0.1°, and thus improve the spatial resolution of the light-receiving module.

[0041] The photodetector of each basic capture module is preferably an avalanche photodiode. This type of photodetector is also known as a single-photon avalanche diode (SPAD). Thus, a silicon photomultiplier (SiPM) can be formed by pairs of avalanche photodiodes. This type of photodetector detects the incidence of a single photon (for example, 10 6 By detecting with a high gain (of a certain degree), the deterioration of the signal-to-noise ratio due to external conditions can be compensated for.

[0042] According to one embodiment of the present invention, the light-receiving module may include an optical unit positioned in front of the basic capture module.

[0043] The system is advantageous in that it comprises a demodulation unit connected to a photodetector, the demodulation unit being designed to extract a data sequence called a demodulated data sequence from the electrical signal converted by the photodetector. Where appropriate, a computing unit can receive the data sequence demodulated by the demodulation unit from the electrical signal converted by the photodetector based on a light beam received by a photodetector module, the computing unit is designed to calculate the value of a correlation function between the demodulated data sequence and the modulated data sequence, and to determine the time of flight between the emission of the modulated first light beam and the reception of the photodetector beam from the value of the correlation function.

[0044] In other words, in this embodiment, the arithmetic unit can calculate the value of a correlation function between the demodulated data sequence and the modulated data sequence. Each value of the correlation function is associated with the value of the time shift of the modulated or demodulated data sequence used to calculate that value of the correlation function.

[0045] The arithmetic unit is designed to generate the initial modulated data sequence from an initial pseudorandom binary sequence. A pseudorandom binary sequence (PRBS) is a data sequence consisting of high values ​​(i.e., "1") and low values ​​(i.e., "0"). Sequences of this type have particularly advantageous properties. Specifically, their autocorrelation function is maximum for a time shift of zero (i.e., when the sequence is compared to itself) and substantially lower than this maximum value for any other time shift (i.e., when the sequence is compared to its own time-shifted version). Furthermore, the cross-correlation function between two pseudorandom binary sequences is smaller than the maximum value of the autocorrelation function of those sequences. Finally, sequences of this type are generally generated using a linear feedback shift register (LFSR), which creates a periodically recursive sequence of the pattern of the pseudorandom binary sequence.

[0046] Considering the autocorrelation properties of the pseudo-random binary sequence, the correlation function thus calculated will be maximum with respect to the time shift value corresponding to the time of flight of the modulated light beam, from emission, reflection, to reception (even with high noise). Therefore, the calculation unit can accurately determine this time shift value associated with the maximum value of the correlation function and derive the distance between the object from which the beam was reflected and the automated vehicle. Furthermore, considering the cross-correlation properties, it is unlikely that the reception of a modulated light beam emitted by an equivalent system in another automated vehicle would lead to a false detection. Finally, it should be understood that detection is performed on the complete data sequence rather than a single pulse to improve the signal-to-noise ratio.

[0047] In one embodiment of the present invention, the arithmetic unit is designed to calculate the respective values ​​in the correlation function between the demodulated data sequence and the initial modulated data sequence by determining the numerical value of the cross-correlation between the initial delayed modulated data sequence and the demodulated data sequence for a given duration, which is associated with the respective values. In other words, each value of the correlation function is thus associated with the time shift value of the initial modulated data sequence used to calculate its value in the correlation function. Thus, the arithmetic unit is designed to determine the time shift value associated with the maximum value of the cross-correlation function.

[0048] It is advantageous for the basic acquisition module to be equipped with a blue light filter. In addition to the fact that the spectral characteristics of light emitted by the sun can be used to improve the signal-to-noise ratio when the telemetry function uses a blue beam, it should be noted that when the first light beam is emitted from a semiconductor light source (e.g., a light-emitting diode), this light beam is obtained from a blue light generator that emits photons faster than the conversion rate of the photoluminescent element. Therefore, in situations where obstacles are detected by analyzing the time of flight of the light beam, if the digitization is based solely on blue light, the resolution of the digitization of the time of flight will inevitably be higher than if it is based on a different frequency range or on the entire visible spectrum. Thus, by using a blue light filter, the uncertainty in detecting the distance of obstacles from the vehicle is reduced.

[0049] The blue light filter may include a bandpass optical filter positioned in front of the photodetector. The optical filter is designed to transmit a certain wavelength range, with a width of substantially less than 20 nm, and the filter has a transmission peak at substantially 450 nm. In this invention, “width of the filter's wavelength range” should be understood as meaning the wavelength range in which the filter's transmittance is at least 80%. In this invention, “transmission peak of the filter” should be understood as meaning the wavelength range of the filter in which the filter's transmittance is maximum.

[0050] Alternatively, if the first light source emits blue-green light, the basic capture module may be equipped with a blue-green light filter to provide similar advantages to those provided by a blue light filter when a blue first light source is used. Similarly, the blue-green light filter may comprise a bandpass optical filter positioned in front of the photodetector. The optical filter is designed to transmit a certain wavelength range, with the width of that range being substantially less than 20 nm, and to have a transmission peak at wavelengths within approximately 10 nm of around 494 nm.

[0051] In one embodiment of the present invention, the light-emitting module is located within the front headlamp of an automated vehicle. It is advantageous that the light-receiving module and the light-emitting module are located within the front headlamp of an automated vehicle.

[0052] In this case as well, it is advantageous that the light-emitting module is designed so that the first and second light beams contribute, all or part, to performing a predetermined statutory photometric function together.

[0053] This could be, for example, a daytime running lamp (DRL) that has the advantage of emitting light at low intensity over a wide area.

[0054] The present invention also relates to a front headlamp for an automatic vehicle equipped with a light-emitting module (and optionally a light-receiving module) according to the present invention.

[0055] Herein, the present invention will be described using examples that are merely illustrative and not intended to limit the scope of the invention, and based on the accompanying drawings. [Brief explanation of the drawing]

[0056] [Figure 1] A diagram schematically and partially illustrating an automated vehicle system according to one exemplary embodiment of the present invention. [Figure 2] A schematic and partial diagram illustrating one exemplary embodiment of each light source in the system shown in Figure 1. [Figure 3] Figure 2 schematically and partially shows the emission spectra of light beams simultaneously formed by the light sources shown. [Figure 4] A schematic and partial diagram illustrating an example of the operation of the system in Figure 1 when telemetry is performed. [Figure 5] This figure schematically and partially shows an exemplary embodiment of the optical unit in the light-emitting module of the system shown in Figure 1. [Modes for carrying out the invention]

[0057] In the following explanation, elements that are identical in structure and function and appear in various diagrams are given the same reference numerals unless otherwise specified.

[0058] Figure 1 shows an exemplary embodiment of the present invention: an automated vehicle system 1.

[0059] System 1 comprises a light-emitting module 2 designed to emit a light beam F1 and a light-receiving module 3 intended to receive a light beam F2.

[0060] In the example described, the light-emitting module 2 and the light-receiving module 3 are located within the same front headlamp of the automatic vehicle. Without departing from the scope of the present invention, modules 2 and 3 may be located in different locations on the automatic vehicle.

[0061] The light-emitting module 2 comprises an optical module 21 designed to emit a light beam F1 and a control unit 22.

[0062] The optical module 21 comprises a first light source 23a capable of emitting light rays and an optical unit 24 designed to project these light rays to form a first light beam F1a. The optical module 21 also comprises a second light source 23b capable of emitting light rays, and the optical unit 24 is designed to project these light rays to form a second light beam F1b.

[0063] In the present invention, the optical unit 24 thus has a common emission surface for the first and second light beams F1a and F1b. The optical unit may also conveniently include one or more reflectors, one or more lenses, one or more apertures, one or more light guides, or one or more collimators, or some combination of these optical elements. Specific embodiments of the optical unit 24 will be described later.

[0064] Figure 2 shows an exemplary embodiment of light sources 23a and 23b, and Figure 3 shows the spectra of the light beams simultaneously formed by these light sources 23a and 23b.

[0065] The light source 23a includes a semiconductor generator 23a1, such as gallium nitride (GaN), capable of emitting blue light rays (by electroluminescence in response to an electric current passing through it) intended to form a first light beam F1a. The generator 23a may be positioned within a reflective cavity. The light source 23a also lacks a photoluminescent element intended to convert all or part of these blue light rays into light rays of another color. The spectrum S1 of the first light beam F1a thus has an emission peak P1 at 445 nm and a full width at half maximum FWHM1 at 20 nm.

[0066] The light source 23b also includes a semiconductor generator 23b1, such as gallium nitride (GaN), capable of emitting blue light rays (in response to an electric current passing through it via electroluminescence). The light source 23b also includes a photoluminescent element 23b2 superimposed on the generator 23b1. The photoluminescent element 23b2 is in the form of an organic or inorganic encapsulant, particularly a resin containing cerium-doped yttrium aluminum garnet (CE:YAG), which absorbs blue light and emits yellow, orange, or yellow-orange light rays (in response to excitation by this light via photoluminescence).

[0067] The photoluminescent element 23b2 is positioned on the generator 23b1 such that the majority of the blue light rays emitted by the generator 23b1 excite this element 23b2 (by photoluminescence) to emit yellow, orange, or yellow-orange light rays. These yellow, orange, or yellow-orange light rays are intended to substantially collectively form the second light beam F1b.

[0068] The spectrum S2 of the first light beam F1b thus has an emission peak P2 at 550 nm and a full width at half maximum FWHM2 at 100 nm.

[0069] As shown in Figure 3, the positions of emission peaks P1 and P2, and the full widths at half maximum FWHM1 and FWHM2, ensure that the overlap band between spectra S1 and S2 extends beyond a wavelength of 460 nm.

[0070] Thus, when the first and second light beams F1a and F1b are emitted simultaneously (under the control of control unit 22), they form an overall light beam with a spectrum corresponding to the superposition of emission spectra S1 and S2 as shown in Figure 3. Depending on the power of light beams F1a and F1b, the color of this overall light beam may appear white to the human eye.

[0071] As long as the overall light beam appears white, it is possible to use this light beam (partially or completely) to contribute to performing a predetermined (especially legally defined) photometric function. In this case, the optical unit 24 is designed so that the overall light beam's photometric distribution satisfies the requirements of that function. For example, the overall light beam may be configured to contribute to performing a daytime running lamp (DRL) function.

[0072] It should be noted that the present invention is not limited to a combination of a single first light source 23a and a single second light source 23b, and the number of first and second light sources can be changed without departing from the scope of the present invention. Similarly, without departing from the scope of the present invention, it is conceivable to change the semiconductor component ratio of the generators 23a1, 23b1 and / or photoluminescence elements 23b2 of one of the first and second light sources 23a, 23b, and / or the other, in order to shift the peaks P1, P2 of the spectra S1 and S2, and / or change the magnitude of the full width at half maximum FWHM1, FWHM2. In particular, it is conceivable to replace the second light source 23b described in Figure 2 with chips that emit red light and green light, respectively. These chips are selectively controllable to control the color of the light beams they emit in order to complement the first light beam F1a to form a substantially white overall light beam.

[0073] In addition to this photometric function, the first light beam F1a enables system 1 to perform the function of detecting and calculating the position of objects on the road. This will be explained with reference to Figure 4, which shows the telemetry method performed by optical system 1 using the optical module 21.

[0074] For this purpose, System 1 comprises a processing unit 4 and a control unit 22. The control unit 22 includes a modulation unit 22a intended to control the first light source 23a, and also includes a drive unit 22b intended to control the power supply to the second light source 23b.

[0075] In the first stage, the arithmetic unit 4 periodically generates an initial data sequence Seq. In the example described, the initial sequence Seq is a pseudo-random binary sequence (also called an M-sequence) of the largest size (composed of "(multiple) 0s" and "(multiple) 1s") with a 50% duty cycle.

[0076] In the second stage, the modulation unit 22a modulates the first light beam F1a emitted by the first light source 23a of the optical module 21 by controlling, for example, the power supply sent to the first light source 23a based on the data sequence Seq.

[0077] In the example described, the modulation unit 22a includes a generator of pulse frequency modulated control signals. This control signal can be used to control the switching power supply (not shown) of the first light source 23a. Conventionally, the frequency set value of this control signal (set by the modulation unit 22a) can be used to control the average power thus sent to the first light source 23a, and therefore to control the luminosity of the first light beam F1a.

[0078] Thus, the modulation unit 22a converts the data sequence Seq into a modulation signal (a signal for modulation) and uses this modulation signal to modulate the initial control signal. In other words, the first light beam F1a emitted under the control of the modulated signal Sseq consists of a train of light pulses. The pulses are successive at a variable frequency, but the frequency is high enough that the human eye can no longer distinguish between them (for example, higher than 100 kHz or higher than 1 MHz, especially between 50 MHz and 100 MHz). Furthermore, the amplitude, width, and / or position of each pulse with respect to the period enable the first light beam F1a to transport the data sequence to the photoreceiving module 3.

[0079] In the example described, note that each optical pulse corresponds to a bit with the value "1" in the modulated data sequence Seq. The average power of the portion of the first optical beam F1a containing the sequence Seq is thus the number of bits with the value "1" in this first sequence Seq relative to the total number of bits in this sequence Seq, and the duration (pulse width) T of each pulse. p And the peak power P of these pulses p It is determined by [the following].

[0080] It should also be noted that other types of modulation, particularly pulse code modulation (PCM), pulse amplitude modulation (PAM), pulse width modulation (PWM), or pulse position modulation (PPM), can be similarly employed within the scope of the present invention.

[0081] In parallel with the second stage, the control unit 22 determines the duty cycle DC, and the drive unit 22b controls the power supply to the second light source 23b according to this duty cycle.

[0082] In the example described, the drive unit includes a generator of a control signal Spwm that is pulse-width modulated based on a duty cycle DC. This control signal can be used to control the switching power supply (not shown) of the second light source 23b. Conventionally, the duty cycle DC of this control signal (set by the control unit 22) can be used to control the average power thus sent to the second light source 23b, and therefore to control the luminosity of the second light beam F1b.

[0083] In other words, the second light beam F1b emitted under the control of the signal Spwm consists of a train of light pulses. The pulses are successive at a variable frequency, but the frequency is high enough that the human eye can no longer distinguish between them (however, it is considerably lower than that of the first light beam F1a, for example, around 1 kHz). Note that in the illustrated embodiment, the drive unit 22b is a low-frequency type, while the modulation unit 22a is a high-frequency type.

[0084] Furthermore, the duty cycle DC is the duration T of each pulse of the second light beam F1b. H The period T of these pulses is the duration T of each pulse in the first light beam F1a. p The control unit 22 will determine that it will be significantly longer than that.

[0085] More precisely, in this invention, the peak power P of each pulse of the first light beam F1a p This can be significantly increased compared to known solutions, but only as long as this power increase does not affect the power of the second light beam F1b. Thus, it becomes possible to extend the detection range of the telemetry function and reduce the signal-to-noise ratio.

[0086] However, the average power of the overall light beam formed by the first and second light beams F1a and F1b is regulated by the legal requirements surrounding the photometric function that this overall light beam must perform. This includes the duty cycle of the data sequence Seq and the peak power P. p Depending on the type of photometric function that the overall light beam must perform, the calculation unit 4 can thus determine the duty cycle DC such that the ratio of blue to yellow in the overall light beam is correct and the legal requirements for the photometric function are met.

[0087] The light beam, consisting of the first and second light beams F1a and F1b, is thus emitted until it reaches an object O located around the vehicle and is reflected by the object towards the light receiving module 3. The light beam F2 received by the light receiving module thus consists of the portion of the overall light beams F1a and F1b that has been reflected by object O, and noise (for example, that generated by sources of stray light (such as city lighting, vehicle lighting, and even sunlight)).

[0088] As shown in Figure 1, the light receiving module 3 includes an optical unit 31, and multiple basic acquisition modules 32 are provided downstream of the optical unit 31. The light receiving module 3 also includes a demodulation unit 33.

[0089] Each basic capture module 32 comprises a photodetector 32a and a blue light filter 32b positioned in front of the photodetector 32a. The light beam F2 received by the light receiving module 3 is thus focused by the optical unit 31 (after passing through the filter 32b) onto one or more photodetectors 32a.

[0090] Each filter 32b is a bandpass blue light filter (blue band light transmission filter) whose transmission peak is centered at a wavelength of 450 nm, allowing light rays with wavelengths between 440 and 460 nm to pass through, while the remaining light is absorbed by this filter.

[0091] When sunlight conditions near the vehicle are particularly bright, sunlight is added to the light beam F2 received by the light receiving module 3. Sunlight (in the visible spectrum) is considerably brighter than light from photometric functions such as daytime running lights. Therefore, the light beam F2 received by the light module 3 consists of the light beams F1a and F1b emitted by the light-emitting module 2, and sunlight. The intensity level of this beam F2 significantly exceeds that of beam F1 in the visible wavelength range. On the other hand, due to some absorption of light by the atmospheric layer, there are valleys in the solar spectrum where the light is weak or even zero. This is particularly true for wavelengths between 440 and 460 nm in the visible spectrum.

[0092] Each filter 32b can thus be used to minimize, firstly, the influence of the sun, and secondly, the component of the second light beam F1b that results in beam F2. The latter is achieved by eliminating all frequencies of beam F2 except for the range containing the peak wavelength of the spectrum of the emitted first light beam F1a.

[0093] Thus, the filter 32b can be used to leave only the components of the beam F2 corresponding to the light rays from the first light source 23a (note that the light rays of yellow light are emitted by the second light source 23b with a longer reaction time, considering the delay brought in by photoluminescence). Therefore, by performing detection exclusively based on the blue light received by the light receiving module 3, the resolution of calculating the flight time of the light beam F2, and / or the data transmission speed between the light emitting module 2 and the light receiving module 3 is improved.

[0094] The photodetectors 32a are the same, and each is formed by an avalanche photodiode of a silicon photomultiplier. These photodiodes are dispersedly arranged in an array. Note that the dimensions of each photodetector are in the micrometer range. Thus, the assembly forms a sensor whose spatial resolution of light reception is about 1° or even about 0.1°. And the detection ability of that sensor is particularly high by using an avalanche photodiode (even under deteriorated capture conditions).

[0095] In the third stage, each of the photodetectors 32a converts the portion of the light beam F2 it receives into an electrical signal Sel and sends the electrical signal to the demodulation unit 33. And in the fourth stage, the demodulation unit 33 can extract what is called a demodulated data sequence Seq2 from the electrical signal.

[0096] In the example to be described, the demodulation unit 33 can, for example, count the number of photons received by the basic capture module 32 during the time interval corresponding to the pulse duration T p from the electrical signal Sel. And the demodulation unit 33 can determine whether this amount of photons corresponds to the pulse of the first light beam F1a, and thus whether it corresponds to a bit having the value "1" or a bit having the value "0" by performing threshold processing (binarization) with respect to the value determined from the peak power P p .

[0097] Thus, the demodulated binary sequence (demodulated binary sequence) Seq2 is sent to the arithmetic unit 4. In the fifth stage, the arithmetic unit 4 calculates the value of the correlation function Fcorr between the modulated sequence Seq and the demodulated sequence Seq2.

[0098] Thus, the calculation unit 4 calculates the numerical value of the cross-correlation (as a result of circular convolution) between the modulated sequence Seq and the demodulated sequence Seq2, which are delayed according to each of the time shift values, for a given number of time shift values.

[0099] Considering the autocorrelation and crosscorrelation properties of the pseudo-random binary sequence, the correlation function Fcorr is thus maximized with respect to a time shift value corresponding to the time of flight between the moment when the light beams F1a and F1b are emitted by the light-emitting module 2 and the moment when they are received by the light-receiving module 3. Thus, the modulated sequence Seq, delayed by this value, effectively corresponds to the demodulated sequence Seq2 (excluding noise).

[0100] In the sixth stage, the calculation unit 4 checks the maximum value of this correlation function Fcorr and calculates the value τ of the time of flight (of the light beams F1a and F1b between object O and the vehicle) associated with this maximum value.

[0101] In the seventh stage, the calculation unit 4 calculates the distance d between object O and the vehicle.

[0102] Here, an exemplary embodiment of the optical unit 24 will be described with reference to Figure 5.

[0103] In the example shown in Figure 5, the optical unit 24 includes a cylindrical light guide 5 formed from a single solid component made of, for example, polymethyl methacrylate (PMMA) or polycarbonate (PC).

[0104] This light guide 5 has a coupling surface 51 (i.e., an incident surface), and the first and second light sources 23a and 23b are positioned facing the coupling surface 51.

[0105] In the example described, the optical module 21 comprises three first light sources 23a aligned along one diagonal of the coupling surface 51, and two second light sources 23b aligned along another diagonal of the coupling surface 51 intersecting the first diagonal. Other arrangements of the first and second light sources 23a and 23b are also conceivable without departing from the scope of the present invention.

[0106] The light guide 5 comprises three parts: a mixing portion 52 extending from the coupling surface 51, a connecting portion 53 extending from the mixing portion 52, and a main portion 54 extending from the connecting portion 53.

[0107] The coupling surface 51 is used to couple (connect) light rays to the light guide 5. These light rays are emitted by the first and second light sources 23a and 23b and enter the guide 5 through this coupling surface 51. Thus, the light rays propagate through the light guide 5 by internal total internal reflection.

[0108] Furthermore, the mixing section 52 has a hexagonal cross-section S52 and lacks any decoupling members used to stop the propagation of light rays due to total internal reflection. This hexagonal cross-section is thus used to optimize the mixing of light rays emitted by the first and second light sources 23a and 23b in order to spatially homogenize the color of the overall light beam.

[0109] The main portion 54 has a substantially circular cross-section S54 and is provided with a plurality of prisms 54a on a portion of its periphery. These prisms 54a define the exit surface 54b of the light guide 5 on the opposite portion of the periphery of the main portion 54.

[0110] These prisms 54a form a decoupling member used to reflect light rays propagating within the guide toward the exit surface 54b (by total internal reflection). Therefore, the exit surface 54b is a common exit surface for light rays emitted by the first and second light sources 23a and 23b.

[0111] It should be understood that, without departing from the scope of the present invention, an optical system equipped with a blue-green first light source can also obtain the same advantages, particularly if the optical system is equipped with a blue-green light filter.

[0112] The above description clearly explains how the present invention achieves its stated objectives, namely, an optical system for an automated vehicle capable of performing both a given legally defined photometric function and a telemetry function, and in particular, how it can increase the power of the light beam component that performs the telemetry function without increasing the number of light sources, while satisfying the legal requirements for the photometric function. These objectives are achieved, in particular, by a light-emitting module having two light sources, one of which is dedicated to performing the telemetry function and the other which complements the first one to perform the photometric function.

[0113] In no event is the present invention limited to the embodiments specifically described herein, but in particular extends to all equivalent means and any technically functional combination thereof. In particular, the light-emitting module may use light sources of other types than those described (e.g., laser diodes, VCSELs, SLEDs, RGB diodes, etc.) or optical units of other types than those described (e.g., guide sheets, etc.) so that the light-emitting module has a different configuration. It may also perform photometric functions other than those described (in particular, low-beam illumination, position lights (parking lights), and turn signal functions). Wavelength ranges other than those described are also possible.

Claims

1. An optical system (1) for an automated vehicle, comprising a light-emitting module (2) having an optical module (21) and a control unit (22), wherein the optical module (21) comprises a first light source (23a) capable of emitting a first light beam (F1a) having a spectrum (S1) having a first peak (P1) below an intermediate wavelength, and a second light source (23b) capable of emitting a second light beam (F1b) having a spectrum (S2) having a second peak (P2) above the intermediate wavelength, the intermediate wavelength being 490 nm or greater, and the control unit (22) being designed to control the first and second light sources to emit the first and second light beams simultaneously, and the control unit comprising a modulation unit (22a) capable of receiving a data sequence (Seq), the modulation unit (22a) being designed to modulate the emitted first light beam based on the received data sequence,

2. The optical system (1) according to the claim, characterized in that the intermediate wavelength is 490 nm.

3. The optical system (1) according to the claim, characterized in that the first light source (23a) is designed such that the spectrum (S1) of the emitted first light beam (F1a) has a first peak (P1) that falls within the range of 380 nm to the intermediate wavelength, and the second light source (23b) is designed such that the spectrum (S2) of the second light beam (F1b) has a second peak (P2) that falls within the range of 520 nm to 580 nm.

4. The optical system (1) according to the claim, characterized in that the first and second light sources (23a, 23b) are designed such that the overlap band between their spectra (S1, S2) is substantially zero.

5. The optical system (1) according to any one of the above claims, characterized in that the first light source (23a) comprises a generator (23a1) capable of emitting the first light beam (F1a), and the first light source does not have a photoluminescent element, and the second light source (23b) comprises a generator (23b1) capable of emitting a light ray and a photoluminescent element capable of absorbing most of the light ray and emitting the second light beam (F1b).

6. The optical system (1) according to any one of the claims, wherein the control unit (2) comprises a drive unit (22b) for supplying power to the second light source (23b), and the control unit is designed to control the drive unit using a pulse-width modulated signal (Spwm) having a duty cycle (DC) higher than the duty cycle of the received data sequence (Seq).

7. The control unit (2) sets at least the duty cycle of the received data sequence (Seq) and the peak power setpoint (P) of the pulse group forming the first light beam (F1a). ｐ The optical system (1) according to the claim, characterized in that it is designed to determine the duty cycle (DC) of the pulse-width modulated signal (Spwm) from the above.

8. The optical system (1) according to any one of the above claims, characterized in that the optical module (21) comprises optical units (24, 5) capable of receiving the first and second light beams (F21a, F21b), and the optical units (24, 5) have a common emission surface (54b) for the first and second light beams.

9. The optical system (1) according to the claim, wherein the optical unit (24) comprises a light guide (5) having at least one coupling surface (51) for the first and second light beams (F1a, F1b), the guide being designed so that the light rays coupled via the coupling surface propagate within the guide by total internal reflection, the guide comprising a decoupling element (54a) capable of separating the coupling of the light rays propagating within the guide toward the common exit surface (54b), and the guide comprising a mixing portion (52) between the coupling surface and the decoupling element for the first and second light beams coupled to the light guide.

10. The optical system (1) according to the claim, characterized in that the light guide (5) has a substantially cylindrical shape, and the cross-section (S52) of the mixing portion (52) of the guide is polygonal.

11. An optical system (1) according to any one of the claims, comprising: a light receiving module (3) capable of receiving a light beam (F2), the light receiving module comprising at least one basic capture module (32) having a photodetector (32a) capable of converting the received light signal into an electrical signal (Sel); a calculation unit (4) designed to generate a modulated data sequence (Seq) and to send the modulated data sequence to the modulation unit (22a) in order to emit the first light beam (F1a) modulated by the optical module (21); and the calculation unit being designed to determine the time of flight (τ) between the emission of the modulated and emitted first light beam and the reception of the light receiving beam, from the electrical signal converted by the photodetector based on the light receiving beam received by the light receiving module (3).

12. The optical system (1) according to the claim, further comprising a demodulation unit (33) connected to the photodetector (32a), wherein the demodulation unit (33) is designed to extract a data sequence (Seq2) called a demodulated data sequence from an electrical signal (Sel) converted by the photodetector, and the calculation unit (4) is capable of receiving a data sequence demodulated by the demodulation unit from an electrical signal converted by the photodetector based on a light beam (F2) received by the light receiving module (3), and the calculation unit is designed to calculate the value of a correlation function (Fcorr) between the demodulated data sequence and the modulated data sequence (Seq), and to determine the time of flight (τ) between the emission of the modulated and emitted first light beam (F1) and the reception of the light receiving beam from the value of the correlation function.

13. The optical system (1) according to either claim 11 or 12, characterized in that the basic capture module (32) includes a filter that transmits light corresponding to the first peak (P1) of the first light beam (F1a), for example, blue light or blue-green light.

14. The light system (1) according to any one of the claims, characterized in that the light-emitting module (2) is located inside the front headlamp of an automatic vehicle.

15. The optical system (1) according to the claim, wherein the light-emitting module (2) is designed so that the first and second light beams (F1a, F1b) together contribute, either fully or partially, to performing a predetermined statutory photometric function.

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