Optical system for obstacle detection

Abstract

Optical system for detecting obstacles The invention relates to an optical system for a vehicle for detecting obstacles, characterized in that light receiving means (32) comprise a plurality of focusing devices (9, 91, 92, 93), each focusing device (9, 91, 92, 93) being configured to focus the light onto the same receiving surface of one or more photonic receivers (321) and oriented differently from the other focusing devices, the optical system (1) comprising means for selectively activating (100) at least one of the focusing devices (9, 91, 92, 93). (Figure 2)

Description

Title of the invention: Optical system for detecting obstacles

[0001] The present invention relates to the fields of optics and electronics, and finds a particular application in the automotive field. It relates more precisely to an optical system integrating an obstacle detection function, which can be installed in a vehicle.

[0002] In recent vehicles, sets of light-emitting diodes are commonly used to produce external lighting devices such as dipped headlights or signaling lights. These sets of diodes allow energy savings while providing vehicles with light signatures specific to each brand, and are anticipated as future means of communication between vehicles or with road infrastructures, thanks to an optical communication technology such as VLC (for "Visible Light Communication") for example.

[0003] Indeed, the bandwidth of a white light-emitting diode with a side dimension of one millimeter is approximately 2 MHz (MegaHertz), and may therefore be sufficient to enable light communication between vehicles or between a vehicle and a road infrastructure. However, this bandwidth is not suitable for obstacle detection type applications. Such an application is generally carried out optically in certain vehicles using LiDAR (Light Detection And Ranging) technology based on infrared laser emitters allowing analysis of the reflected signal over a bandwidth of the order of several tens of MegaHertz, or even a few hundred MegaHertz. LiDAR systems embedded in vehicles are nevertheless very expensive.

[0004] The inventors have however discovered that such an obstacle detection application is possible by using light-emitting diodes that emit light in the visible spectrum, by increasing their bandwidth, either by equalization techniques, or by using diodes smaller than 300 micrometers, or by combining these techniques. This application may require the use of a specific type of light-emitting diode drive unit such as a high-speed control unit or a laser control unit. The light-emitting diodes used for this application are also blue-light light-emitting diodes adapted to emit white light.

[0005] Thanks to this discovery, the inventors have made it possible to replace the expensive means of LiDAR technology in a vehicle with specific optical systems based on light-emitting diodes, which perform an obstacle detection function. and also perform regulatory signaling or lighting functions.

[0006] However, the cost issue remains a current issue for the implementation of such an optical system, particularly since it is necessary to have a large number of photoreceptors to achieve high-resolution detection over a large, expanded overall detection field.

[0007] The present invention falls within this context and aims to remedy at least in part the aforementioned drawbacks by providing an optical system integrating an obstacle detection function, which allows a large detection field without it being necessary to oversize the photoreceptor means.

[0008] To this end, the invention proposes an optical system for a vehicle enabling the detection of obstacles, the optical system comprising:

[0009] - light emitting means comprising at least one photonic emitter capable to emit a high-frequency coded light signal towards the exterior of the vehicle, said light signal being included at least in a predefined range of wavelengths,

[0010] - light receiving means comprising at least one photonic receiver capable of receiving a reflected light signal contained in light arriving from outside the vehicle and heading towards the photonic receiver, said light comprising the reflected light signal and uncoded light, the reflected light signal originating from a reflection on an obstacle, of the light signal emitted by the light emission means, and at least one device for focusing the light arriving from outside the vehicle to direct it towards the photonic receiver,

[0011] - obstacle detection means, and

[0012] - means for demodulating the reflected light signal received by the receiver photonic, the obstacle detection means comprising means for calculating a distance to the obstacle as a function of a demodulated signal supplied by the demodulation means and the light signal emitted by the photonic transmitter,

[0013] the optical system being characterized in that the light receiving means comprise a plurality of focusing devices, each focusing device of said plurality of focusing devices being configured to focus the light onto the same receiving surface of one or more photonic receivers and oriented differently from the other focusing devices, the optical system comprising means for selectively activating at least one of the focusing devices.

[0014] By "uncoded light" we of course mean the part of the light heading towards the photonic receiver which does not include the high-frequency coded reflected light signal.

[0015] The predefined wavelength range is a useful range in which the light signal is received for decoding and corresponds for example to wavelengths for which the signal-to-noise ratio is most favorable, the light signal being able to be present also outside the predefined range of wavelengths. In an exemplary embodiment, the range of wavelengths can be in the visible spectrum, preferably between 420 nanometers (nm) and 460 nanometers (nm).

[0016] When the optical system is on board a vehicle, the light signal is emitted by the emitting means towards the outside of the vehicle, and the receiving means are configured to receive such a light signal having been reflected and arriving from outside the vehicle.

[0017] The demodulation means have in particular the function of analyzing the received light and identifying the uncoded light, that is to say the part of the light heading towards the photonic receiver not comprising the high-frequency coded light signal, in order to keep only the coded light signal and to be able to determine where the obstacle is located having reflected and returned to the vehicle this coded signal previously emitted by the vehicle's transmitting means.

[0018] According to the invention, there is a single photonic receiver or a single set of photonic receivers which are capable of receiving the rays having passed through distinct focusing devices. Having a plurality of focusing devices allows the optical system to cover a larger detection field than it would if a single focusing device were provided opposite the same reception surface. It is thus possible to detect a greater quantity of light information and to increase the obstacle detection performance of the system.

[0019] According to the invention, the receiving means are configured so that a beam of light rays, transmitted from one of the focusing devices to a single receiving surface formed by one or more photonic receivers, is distinct from a beam of light rays transmitted from another of the focusing devices. To this end, the optical system is particular in that each focusing device is provided with an orientation which is specific to it and which is distinct from that of the other focusing devices, the focusing devices however being configured to focus the external light onto the same receiving surface.

[0020] The orientation of a focusing device is defined by the optical axis of this focusing device and it is thus notable that according to the invention the optical axes of at least two focusing devices intersect each other. In this way, these focusing devices are arranged opposite different zones of the road scene, and an assembly, formed by one of the focusing devices and the photonic receiver(s) forming a reception surface common to all the focusing devices, can be dedicated to the obstacle detection of a particular zone of the road scene.

[0021] But this requires knowing where the light rays come from to enable locate where the obstacle is in the overall detection field of the optical system when such an obstacle is detected.

[0022] In this context, the optical system comprises means for selectively activating at least one focusing device. It is thus possible to control, at a given instant in the obstacle detection period, which focusing device(s) are active, i.e. through which focusing device(s) the rays coming from the outside are likely to pass to be directed towards the surface of the photonic receiver(s).

[0023] According to an optional characteristic of the invention, the means for selectively activating at least one of the focusing devices comprise a means for adjusting the optical transmissivity of said at least one focusing device.

[0024] The optical system is configured to control the adjustment means in order to modify the optical transmissivity of the at least one signaling device. The optical system is thus able to define in which zone an obstacle detected by the detection means is located, due to the quantity of light that such or such focusing device is likely to let through at the time of detection of the obstacle.

[0025] According to an optional feature of the invention, the means for selectively activating at least one of the focusing devices are configured to selectively activate the focusing devices according to a predefined activation sequence. According to one embodiment, the focusing devices are activated for a predefined duration, during an activation cycle which is repeated in a loop in said activation sequence. By way of example, an activation cycle may consist of the successive activation of all the focusing devices one after the other.As an alternative example, an activation sequence may include more regularly activating focusing devices of the plurality of focusing devices that are dedicated to obstacle detection in the center of the road scene than focusing devices of the plurality of focusing devices that are dedicated to obstacle detection on the sides of the road scene.

[0026] According to an optional feature of the invention, said activation sequence is variable depending on the speed of the vehicle. In particular, when the vehicle is traveling at low speed, all the focusing devices can be activated at regular intervals and for the same duration, whereas when the vehicle is traveling at high speed, the focusing devices of the plurality of focusing devices which are dedicated to obstacle detection in the center of the road scene are activated more frequently than the focusing devices of the plurality of focusing devices which are dedicated to obstacle detection on the sides of the road scene.

[0027] According to an optional characteristic of the invention, the means for adjusting the optical transmissivity of a focusing device is configured to switch from a state active state of passing light rays from the given predefined wavelength range to an inactive state of blocking these light rays.

[0028] We then speak both of the active / inactive state of the transmissivity adjustment means which is associated with a focusing device and of the active / inactive state of the focusing device itself.

[0029] According to an optional characteristic of the invention, each focusing device is equipped with a transmissivity adjustment means, the transmissivity adjustment means of the focusing devices being controlled synchronously, one of the adjustment means being in an active state while the other adjustment means are in an inactive state.

[0030] This makes it easy to identify at a given detection moment which focusing device the rays that reached the photonic receiver(s) passed through.

[0031] According to an optional characteristic of the invention, the demodulation means receive information on the active and inactive states of the means for adjusting the transmissivity of the focusing devices.

[0032] According to an optional characteristic of the invention, the optical transmissivity adjustment means is controlled to have a time in which it remains active of the order of ten milliseconds. In other words, the control instructions sent to the adjustment means are such that the latter remains in a state capable of allowing the rays to pass towards the photonic receiver(s) for the order of ten milliseconds before resuming a configuration for blocking the light rays.

[0033] According to an optional characteristic of the invention, the transition time of a means for adjusting the transmissivity of a focusing device between an active state, respectively inactive, and an inactive state, respectively active, is less than 5 ms.

[0034] According to an optional characteristic of the invention, the means for adjusting the transmissivity of a focusing device is a liquid crystal element.

[0035] According to an optional characteristic of the invention, the photonic receiver(s) are arranged on a common electronic circuit support.

[0036] According to an optional characteristic of the invention, the focusing devices have optical properties which differ from one focusing device to another.

[0037] The focusing devices may comprise one or more lenses and / or a microlens array. The thickness and / or shape of these lenses may vary from one focusing device to another. These different configurations may result in a wider detection field from one focusing device to another and therefore a modification of the detection resolution of the optical system for a given area of ​​the road scene. For example, a focusing device surrounded by other focusing devices may be used. focusing devices, and intended to detect obstacles in a central area of ​​the road scene, can be specifically configured to have a small detection field and allow high resolution, while focusing devices intended to detect obstacles at the periphery of the road scene can be configured to cover larger detection fields and therefore generate lower resolution detection, which may not be a problem when this low resolution detection concerns verges of the road scene.

[0038] According to an optional characteristic of the invention, the focusing devices are produced separately and arranged at a distance from each other.

[0039] Alternatively, at least two focusing devices are produced in one piece by forming an optical block within which zones of different orientation and / or dimensions and / or shapes are formed to produce distinct focusing devices.

[0040] According to an optional characteristic of the invention, the receiving means further comprise means for filtering the light heading towards the at least one photonic receiver, these filtering means being arranged downstream and / or upstream of the focusing devices. These filtering means are in particular capable of increasing the signal-to-noise ratio between the light signal contained in the light heading towards the photonic receivers and the uncoded light heading towards these photonic receivers. The filtering means are for example wavelength filtering means, such as for example a blue light filter. Here, the terms “upstream” and “downstream” are defined with respect to the direction of propagation of the light signals heading towards the photonic receiver.

[0041] For example, the filtering means comprise a high-pass filter, with a cut-off wavelength greater than or equal to the upper limit of the predefined range of wavelengths, and a low-pass filter, with a cut-off wavelength less than or equal to the lower limit of the predefined range of wavelengths. The high-pass filter allows only very little passage of the components of the light whose wavelengths are less than its cut-off wavelength, and the low-pass filter allows only very little passage of the components of the light whose wavelengths are greater than its cut-off wavelength.

[0042] According to an optional feature of the invention, the photonic receivers are respectively formed of single-photon avalanche diodes, the light transmitted by each of the different focusing devices being focused onto the same set of these diodes. Alternatively, the photonic receivers may be PIN (positive-intrinsic-negative) photodiodes or simple PN (positive-negative) junction photodiodes.

[0043] According to an optional characteristic of the invention, the light emitting means are capable of forming a lighting beam and / or performing a signaling function.

[0044] The invention also relates to a method for detecting obstacles implementing an optical system as previously mentioned, during which the demodulation means provide the obstacle detection means with a demodulated signal, and during which the means for selectively activating at least one of the focusing devices are implemented at regular intervals, so that the focusing devices are activated in turn, information relating to the activation state of each of the focusing devices being known to the obstacle detection means.

[0045] The information relating to the activation state may consist of information on the change of state of each focusing device as soon as the active or inactive state, i.e. the state of transmission or blocking of the light rays, is caused to change, or it may consist of a list of the different states of each focusing device during a defined cycle. It is specified that this information is known to the obstacle detection means, which covers both a case where the information is directly sent to these obstacle detection means and a case where the information is considered by the demodulation means which process the information for the obstacle detection means.

[0046] The invention also relates to a vehicle comprising an optical system according to the invention. The vehicle according to the invention has advantages similar to those of the optical system according to the invention.

[0047] Other characteristics and advantages of the invention will become apparent from the following description on the one hand, and from several examples of embodiment given for informational and non-limiting purposes with reference to the attached schematic drawings on the other hand, in which:

[0048] [Fig. 1] represents an optical system for a vehicle integrating an obstacle detection function on a road scene,

[0049] [Fig.2] schematically represents the receiving means of the optical system of [Fig.l], according to a first embodiment of the invention;

[0050] [Fig.3] schematically represents a first operating state of the receiving means of [Fig.2];

[0051] [Fig.4] schematically represents a second operating state of the receiving means of [Fig.2];

[0052] [Fig.5] schematically represents a third operating state of the receiving means of [Fig.2];

[0053] [Fig.6] schematically represents the receiving means of the optical system of [Fig.l], according to a second embodiment of the invention.

[0054] [Fig.l] now represents the operation of such an optical system 1 of obstacle detection. The obstacle detection uses, on the face of the vehicle integrating this function, emitting means 12 comprising a plurality of photonic emitters, for example in each optical unit of the vehicle when the optical system is intended to detect frontal obstacles, and receiving means 32 comprising a plurality of photonic receivers, also present in this example in each optical unit of the vehicle. The plurality of photonic emitters of the emitting means 12 comprises for example two blue light-emitting diodes 121, 122, adapted to emit white light.

[0055] The light-emitting diodes 121, 122 each comprise, for example, a layer of Galium-Indium Nitride (InGaN) on which is deposited a light color conversion layer generally called phosphor in the bibliography. Thus, they are suitable for producing a light beam of a daytime running light.

[0056] The photonic receivers can in particular be constituted by photon avalanche photodiodes or SPAD photodiodes (from the English "Single-Photon Avalanche Diode") for increasing the reception gain, such as the SPAD photodiodes referenced 321, 322. Of course, [Fig.l] only comprises two light-emitting diodes and two photodiodes for simplicity. Many more photodiodes are preferentially used, and the daytime running lights can use many more diodes.

[0057] The plurality of light-emitting diodes is capable of emitting a high-frequency coded light signal s2 towards the exterior of the vehicle, and the plurality of photodiodes is capable of receiving a corresponding reflected light signal s2, arriving from the exterior of the vehicle.

[0058] In order to form the light signal si coded at high frequency, each optical block comprises a source 10 of electrical signals in voltage squares and a control unit 3, connected upstream of the light-emitting diodes 121, 122. To send the light signal si, the source 10 provides a square signal whose width 1 of the squares is, in an exemplary embodiment, approximately 10ns (nanoseconds), the frequency of the signal being 50MHz. The duty cycle of the signal is, in this example, less than or equal to 50%.

[0059] To enable the transmission of this signal having such a high frequency level, the control unit 3 comprises for example a pre-equalization stage, possibly associated with an amplifier stage. It is therefore an electronic device. Instead of or in addition, the light-emitting diodes 121, 122 are chosen to be smaller than 300 micrometers so as to naturally have a cut-off frequency greater than 50 MHz.

[0060] The light signal sent by the diodes 121, 122 encodes a sequence specific "slots" or light peaks of width 1 of 10ns, this sequence repeating cyclically. In other words, the light signal si is modulated according to a specific data sequence, called modulating. The sequence of slots is defined so as to easily evaluate a time shift between its emission and its reception as explained below.

[0061] The reflection of the light signal s on an obstacle 6 gives rise to the reflected light signal s2 of sufficient light power to be captured by the photodiodes 321, 322.

[0062] The receiving means 32 comprise, in addition to the photodiodes 321, 322, at least one focusing device 9 configured to focus the light onto the photodiodes 321, 322. As illustrated, the receiving means 32 may comprise filtering means 8 for filtering the light from the reflected light signal s2, in particular so as to only allow the blue component of this light to pass through, and a focusing device 9 focusing the component resulting from the filtering of the light towards the photodiodes 321, 322. The blue light emitted by the diodes 121, 122 generally has a light intensity lower than that of the illumination of the sun, but approaches it for wavelengths close to 460nm (nanometers). The modulation of the reflected signal s2 makes it possible to distinguish it from external light pollution in the process of demodulating this reflected light signal s2.

[0063] More precisely, the photodiodes 321, 322 capture the blue components of the reflected light signal s2 and of the ambient light, for example sunlight, and provide an electrical signal to an electronic control device 13 which amplifies it and provides it to demodulation means 38. The electronic control device 13 optionally comprises, in addition to an amplifier stage, a post-equalization stage. The photodiodes 321 and 322 being SPAD photodiodes, the electrical signal that they provide is equivalent to a count Nb of the photons received as a function of time t by each of the photodiodes 321, 322. Thresholding means 34 adjust the detection level of these photodiodes so as to separate in the intensity of the light signal received by the photodiodes 321, 322, the portion of light intensity due to sunlight.This thresholding corresponds to keeping in the counting signal Nb as a function of time t, only the values ​​extending beyond a number of photons corresponding to the luminous intensity of the blue component of sunlight, which gives rise to a thresholded light signal s3. Such thresholding makes it possible to remove the component due to sunlight from the received electrical signal. Of course, here we call a thresholded light signal in reality an electrical or digital signal corresponding to the thresholding of the received reflected light signal s2.

[0064] The demodulation means 38 also comprise means 36 for correlating the thresholded light signal s3 once demodulated, with the light signal si sent by the diodes 121, 122. These correlation means 36 determine a time shift r between the demodulated thresholded light signal s3 and the sent light signal s1, and transmit this time shift r to obstacle detection means 40 of the vehicle. The obstacle detection means 40 convert this time shift r into a distance relative to the obstacle 6, and therefore make it possible to detect this obstacle. Described otherwise, the demodulation means 38, from the reflected light signal 2 received by the photodiodes 321, 322, are capable of providing the obstacle detection means 40 with at least one value representative of a time shift r between, on the one hand, the reflected light signal s2 and, on the other hand, the light signal s1 emitted by the photonics 121, 122.

[0065] A first embodiment of the receiving means 32 will now be described in more detail, in particular with reference to FIGS. 2 to 5.

[0066] The receiving means 32 comprise in particular a printed circuit board 42, at least one photonic receiver 321 and electronic components 44 associated with this photonic receiver, and optical elements 46 forming focusing devices 9, the focusing devices being according to the invention configured to focus the light which passes through them respectively towards the same reception zone, that is to say the same photonic receiver.

[0067] It should be noted that in the illustrated example the receiving means comprise a single photonic receiver or a single set of photonic receivers, a set which can be formed from a matrix of around ten or hundreds of photodiodes glued to each other and controlled by the same electronic components. Throughout the description, it should be understood that when a single photonic receiver is mentioned, the aim is to cover one or more photonic receivers forming a single reception zone on which several focusing devices are focused.

[0068] However, without departing from the context of the invention, it is possible to have several sets of photonic receivers, since, in accordance with what is illustrated, several focusing devices are associated with the same photonic receiver or set of photonic receivers.

[0069] The photonic receivers consist of photodiodes, here of the SPAD type for Single Photon Avalanche Diode. Each photonic receiver is fixed on the printed circuit board 42.

[0070] The electronic components 44 associated with the photonic receiver form part of the electronic control device 13 previously mentioned and their function is in particular to recover the electrical output signals from the photonic receiver 321, when light is focused on this photonic receiver, to then transmit them to the demodulation means 38. The electronic components 44 can if necessary amplify the electrical signals before supplying them to the demodulation means 38.

[0071] The focusing devices 9 are arranged between the road scene and the at least one photonic receiver 321. According to the invention, each focusing device 9 is configured to focus the light on the same photonic receiver 321 while being oriented differently from the other focusing devices 9.

[0072] The orientation of a focusing device 9 is defined by its optical axis 54 and it is notable in [Fig.2] that the optical axes 54 of the focusing devices 9 are not parallel to each other but intersecting two by two.

[0073] In other words, according to the invention, the photonic receiver 321 can receive light having previously passed through one of the focusing devices or light having previously passed through another of the focusing devices. The light received by this photonic receiver 321 comes from at least one of the focusing devices 9 which are dedicated to it.

[0074] In the example illustrated in [Fig.2], the arrangement of the photonic receiver 321 and the focusing devices is such that a first focusing device 91 is capable of directing the light having passed through it towards the photonic receiver 321, that a second focusing device 92 is capable of directing the light having passed through it towards the same photonic receiver and that a third focusing device 93 is capable of directing the light having passed through it towards the photonic receiver 321.

[0075] Of course, it is understood that the optical system 1 according to the invention is such that an n-th focusing device 9 is capable of directing the light having passed through it towards the same photonic receiver 321.

[0076] Each focusing device 9 is here represented in the form of a converging lens, capable of directing the external rays towards a focal zone corresponding to the zone of the printed circuit board on which the photonic receiver 321 is arranged. It should be understood that this focusing device 9 could, without departing from the context of the invention, be formed of a plurality of lenses or a matrix of microlenses, and where appropriate additionally comprise mirrors, since these optical elements are configured to give the focusing device 9 the converging properties mentioned previously.

[0077] In this way, a singular detection field 90 specific to each focusing device 9 is defined. In [Fig.2], the singular detection fields 90 of the three focusing devices 9 associated with the same photonic receiver 321 are illustrated in dotted lines.

[0078] The detection field 900 of the optical system 1 according to the invention is defined by the addition of the singular detection fields 90 of each of the focusing devices. It is notable according to the invention that the singular detection fields 90 are differently oriented, which makes it possible to achieve a wide detection field 900 of the optical system 1 with narrower singular detection fields 90, and therefore easier and less expensive to implement for a given detection resolution.

[0079] The configuration of the optical system 1 according to the invention, with focusing devices 9 which are focused on the same photonic receiver or set of photonic receivers but which are oriented differently from one to another to generate a specific orientation of the singular detection fields 90, makes it possible to increase the overall detection field 900 of the optical system and it can make it possible, if the focusing devices 9 have optical properties different from one another to have an angular aperture specific to each focusing device, to have different resolutions within the same detection field 900 of the optical system 1, with different angular apertures from one singular detection field 90 to another and therefore different detection resolutions.

[0080] In the example illustrated, and without this configuration being limiting, the focusing device arranged in the center, that is to say surrounded by the other focusing devices and oriented facing the road scene, here the second focusing device 92, is configured to have a narrower angular aperture than that of the neighboring focusing devices 91, 93 arranged on the periphery. In this way, the photonic receiver 321 or the photonic receiver assembly, when it receives the light having passed through the second focusing device 92, can detect obstacles in the given angular range with better resolution.In this example, there is a central detection zone, materialized by the second focusing device 92, with a narrow singular detection field, and therefore a high detection resolution, and two peripheral detection zones, materialized by the first and third focusing devices 91, 93, with a wide singular detection field, and therefore with a lower resolution, it being understood that the extent of the detection field changes while the surface of the receiving means and therefore the density of the detection elements remains the same. This is particularly advantageous because it makes it possible to combine both a high detection resolution for the road scene directly in front of the vehicle, where the risk of collision with an obstacle is the highest, and a wide detection field of the optical system, without having to multiply the number of photonic receivers.

[0081] It should be noted that the illustrated example shows more particularly receiving means 32 of an optical system 1 intended to detect frontal obstacles, with a detection field 900 which extends in front of the vehicle in a longitudinal direction, considering this longitudinal direction as the direction of elongation and main circulation of the vehicle. Of course, what is described here can be applied to optical devices arranged in other areas of the vehicle, and for example to an optical system for detecting lateral obstacles, with the longitudinal direction replaced by the transverse direction.

[0082] In order to detect within the road scene the precise location of a potential obstacle having reflected the light emitted by the optical system with the coded signal, the obstacle detection means 40 must be able to determine which zone of the overall detection field 900 has returned the reflected light signal in the direction of the receiving means, that is to say which singular detection field 90 is concerned by this reflection of the reflected light signal. In other words, the optical system 1 is configured so that the obstacle detection means can associate information relating to the existence of a time shift between the emitted light signal and a reflected light signal and information relating to the focusing devices to determine through which focusing device the light the reflected light signal has passed.

[0083] For this purpose, the optical system 1 according to the invention comprises means for selectively activating the focusing devices 9 which make it possible to recover identification data from an active focusing device and the obstacle detection means 40 are configured to take into account both the information relating to the demodulated signal coming back from the demodulation means 38, and therefore the time shift of the coded light signal, and the information relating to the identification of the active focusing device at the time of the appearance of the time shift.

[0084] An exemplary embodiment will be more particularly described with selective activation means which are formed by means for adjusting the optical transmissivity of the focusing devices. It should however be noted that the selective activation means could take other forms, provided that they make it possible to identify with certainty where the light impacting the photonic receiver in question at a given instant comes from.

[0085] In the example illustrated in [Fig.2], each focusing device 9 comprises a means 100 for adjusting the optical transmissivity of the focusing device.

[0086] The means 100 for adjusting the transmissivity of a focusing device 9 may be configured, in its preferred embodiment, to have an active light-transmitting state or an inactive light-blocking state.

[0087] The transmission state of a transmissivity adjustment means 100 consists of a state in which the associated focusing device 9 allows the transmission of at least the predefined range of given wavelength. In other words, when the coded signal is transmitted over a predefined range of wavelength in the range of 405 to 450 nm, to emit light in the blue color, the active transmission state and the inactive blocking state are considered with respect to this predefined range of wavelengths.

[0088] The transmissivity adjustment means 100 of a focusing device 9 is a device which allows a rapid transition time from one state to another, and in particular from a state blocking the rays destined for the photonic receiver 321 to a state allowing the transmission of these rays to the photonic receiver. The rapid transition time is of the order of 5 ms. This transition time is at least 2 times shorter than the duration of an active state of an adjustment means.

[0089] In particular, the transmissivity adjustment means 100 is a liquid crystal element. In the example illustrated, this liquid crystal element is here represented in the form of a screen arranged opposite the corresponding focusing device 9, and downstream of the latter considering the path of the rays to the photonic receiver 321, but it could be envisaged that the adjustment means are integrated into the focusing device.

[0090] All of the adjustment means 100 for the transmissivity of the focusing devices are controlled synchronously, at least one of the adjustment means 100 being in a different state from the others, and in particular a transmission state while the other adjustment means are in a blocking state.

[0091] The adjustment means 100 are controlled by control instructions 1a emanating from the control device 13, as shown diagrammatically in [Fig.2]. In the example of a liquid crystal element, the control instruction is an instruction to activate or deactivate a power supply. These instructions can in particular be sent according to cycles during which all the focusing devices are made active once, these cycles being repeated infinitely.

[0092] As mentioned previously, the decoding means 38 receive the transmission and blocking states of the means for adjusting the transmissivity of the focusing devices, whether in the form of a detail of the different successive cycles, or a detail of each change of state of the adjustment means.

[0093] In the example illustrated, the focusing devices 9 are made in one piece, forming a single optical body 94 which can facilitate the assembly of the optical system 1.

[0094] The optical body 94 is thus formed from a plurality of optical zones 96 respectively forming one of the focusing devices 9, each of the optical zones being connected to a neighboring optical zone by a neutral zone 98 having the sole function of mechanical strength of the assembly.

[0095] These neutral zones 98 can be covered, on one or other of the faces of the optical body 94, with an opaque coating preventing the passage of light rays towards the photonic receiver(s), this opaque coating having the same function as the light absorption means previously mentioned. In a manner Alternatively, these neutral areas can be formed from an opaque material.

[0096] [Fig.2] also shows filtering means 8 capable of increasing the signal-to-noise ratio between the reflected light signal s2 contained in the light heading towards the photonic receiver(s), and the uncoded light contained in this light.

[0097] These filtering means 8 shown schematically in [Fig.2] downstream of each of the focusing devices 9, considering the direction of propagation of the light towards the photonic receiver(s), could be arranged upstream of the focusing devices in accordance with what has been shown in [Fig.l]. Similarly, these filtering means 8 are here shown in the form of a single plate common to each focusing device 9 but they could alternatively be formed in several separate pieces respectively arranged between a focusing device and the photonic receiver.

[0098] These filtering means 8 have the function of obtaining a light representative of the reflected light signal s2 despite the sunlight which interferes with this reflected light signal s2. They may consist of a high-pass filter and / or a low-pass filter. The high-pass filter may for example have a cut-off wavelength of the order of 420 nm and be made for example of a layer of tinted resin. This high-pass filter has the function in particular of preventing ultraviolet rays from passing towards the photonic receiver(s). The low-pass filter may for example have a cut-off wavelength of the order of 430 nm and its function in particular of reducing the quantity of light received by the photonic receiver(s) of the receiving means.

[0099] Figures 3 to 5 illustrate different operating states of the optical system, with a sequencing of the activation of the focusing devices. In [Fig.3], the first focusing device 91 is made active, while in [Fig.4], it is the second focusing device 92 which is made active and in [Fig.5], it is the third focusing device 93 which is made active.

[0100] In each of these operating states, only one focusing device is made active and the other focusing devices are made inactive simultaneously. The very short transition time, less than 5 ms, from one state to the other, makes it possible to consider that the transitions from one state to the other of each focusing device are simultaneous. In this way, only the active focusing device transmits the light reflected by an obstacle, as well as the ambient light, to the photonic receiver

[0101] As mentioned, the detection means receive for each operating state information on the active / inactive state of each focusing device.

[0102] [Fig.3] illustrates a first operating state in which a first means transmissivity adjustment device 101, associated with the first focusing device 91, is controlled to allow total transmissivity of the light. Almost all of the light rays, and potentially those carrying the light signal reflected by an obstacle, reaching the first focusing device 91 pass through the latter and pass through the first transmissivity adjustment means 101, here a liquid crystal screen as mentioned above. Simultaneously, a second transmissivity adjustment means 102, associated with the second focusing device 92, is controlled to prevent the transmissivity of the light. Almost all of the light rays, and potentially those carrying the light signal reflected by an obstacle, reaching the second focusing device 92 are blocked by the second transmissivity adjustment means 102, here a liquid crystal screen as mentioned above.Likewise, simultaneously, a third transmissivity adjustment means 103, associated with the third focusing device 93, is controlled to prevent the transmissivity of the light. Almost all of the light rays, and potentially those carrying the light signal reflected by an obstacle, reaching the third focusing device 93 are blocked by the third transmissivity adjustment means 103.

[0103] This first operating state is obtained by selective control of the transmissivity adjustment means 100 associated with each focusing device 9. In a synchronized manner, the first adjustment means 101 is made active while the second and third adjustment means 102, 103 are made inactive.

[0104] It is understood that in this first operating state, the light coming from the photonic receiver can only come from one of the focusing devices, here the first focusing device 91, since simultaneously, the other focusing devices 92, 93, by appropriate control of the associated transmissivity adjustment means 102, 103 are inactive and prevent the passage of light. In the event of effective detection of an obstacle during this first operating state, the optical system 1 and in particular the obstacle detection means 40, is thus able to determine that the obstacle is present in the portion of the overall detection field which corresponds to the singular detection field 90 of the focusing device 9 active at the time of the effective obstacle detection, that is to say here the first focusing device 91.

[0105] After a given time, for example of the order of ten milliseconds, the adjustment means 100 are again controlled so that the active adjustment means becomes inactive, to prevent the light rays likely to pass through the associated focusing device from reaching the photonic receiver, and so that one of the other adjustment means, previously inactive, becomes active and allows the light rays likely to pass through the associated focusing device to reach the photonic receiver.

[0106] [Fig.4] illustrates a second operating state then obtained, in which the first transmissivity adjustment means, associated with the first focusing device 91, is controlled to be inactive and prevent the transmission of light. Simultaneously, the second transmissivity adjustment means, associated with the second focusing device 92, is controlled to be active and allow the passage of light rays towards the photonic receiver 321. Almost all of the light rays, and potentially those carrying the light signal reflected by an obstacle, reaching the second focusing device 92 are focused on the photonic receiver 321.In accordance with what happened during the first operating state, the light coming from the photonic receiver 321 can only come from one of the focusing devices, here the second focusing device 92, since simultaneously, the third transmissivity adjustment means, associated with the third focusing device 93, is controlled to prevent the transmissivity of the light.

[0107] It is thus understood that in the event of effective detection of an obstacle during this second operating state, the optical system is thus able to determine that the obstacle is present in the portion of the overall detection field which corresponds to the singular detection field of the active focusing device at the time of effective obstacle detection, i.e. here the second focusing device 92.

[0108] This second operating state is maintained for the same duration as the duration of the first operating state previously described. Then, the adjustment means are again controlled so that the active adjustment means becomes inactive, and one of the other adjustment means previously inactive, here the third focusing device 93, becomes active.

[0109] [Fig. 5] illustrates a third operating state then obtained, in which each of the first and second transmissivity adjustment means, respectively associated with the first and second focusing devices 91, 92 is controlled to be inactive and prevent the transmission of light. Simultaneously, the third transmissivity adjustment means 103, associated with the third focusing device 93, is controlled to be active and allow the passage of light rays towards the photonic receiver. Almost all of the light rays, and potentially those carrying the light signal reflected by an obstacle, reaching the third focusing device 93 are focused on the photonic receiver 321. In accordance with what happened during the other operating states, the light coming from the photonic receiver 321 can only come from one of the focusing devices, here the third focusing device 93.

[0110] In the event of effective detection of an obstacle during this third operating state, the optical system is thus able to determine that the obstacle is present in the portion of the overall detection field which corresponds to the detection field singular of the active focusing device at the time of effective obstacle detection, i.e. here the third focusing device.

[0111] A cycle of controlling the transmissivity adjustment means is carried out by the successive implementation of the operating states described previously. The sequence continues, if necessary, with n-th operating states if the optical system 1 is equipped with more than three focusing devices associated with the same focusing surface, ensuring that during this cycle each of the adjustment means has been made active once.

[0112] Once the cycle is completed, a new cycle, identical to the previous one, is triggered, so that the different operating states are carried out in a loop at regular intervals. This ensures effective monitoring of the entire global detection field of the optical system, by only making obstacle detection inactive in a singular detection field for a few tens of milliseconds, which is too little to generate a risk of non-detection.

[0113] [Fig.6] illustrates a second embodiment, which differs from the above in that the focusing devices are made separately from each other, fixing means specific to each focusing device having to be provided to ensure their fixing within the optical system.

[0114] In accordance with what has been described previously for the first embodiment, the focusing devices 9 are oriented differently from one focusing device to another so that the optical detection field 900 of the optical system is formed by the juxtaposition of singular detection fields 90, each singular detection field being specific to a focusing device with all the focusing devices which are focused on the same photonic receiver or the same set of photonic receivers.

[0115] Here again, in this second embodiment, the means for selectively activating the focusing devices are formed by liquid crystal screen type films, which respectively constitute a means for adjusting the transmissivity of the focusing device with which they are associated. The control of the selective activation means is in accordance with what was previously described for the first embodiment.

[0116] Furthermore, and in accordance with what has been described for the first embodiment, [Fig.6] shows filtering means 8 capable of increasing the signal-to-noise ratio between the reflected light signal s2 contained in the light heading towards the photonic receiver and the uncoded light contained in this light.

[0117] Of course, the invention is not limited to the examples which have just been described and numerous adjustments can be made to these examples without departing from the scope of the invention. By way of example, the invention is not limited to the use of light-emitting diodes capable of emitting blue light, the high-frequency coded light signal being able to be emitted in another wavelength range.

[0118] Finally, the characteristics of the different variant embodiments of the invention envisaged in this application can be combined to achieve the invention, to the extent that these variants are not incompatible with each other.

Claims

Claims

1. Optical system (1) for a vehicle enabling the detection of obstacles, the optical system (1) comprising: - light emitting means (12) comprising at least one photonic emitter capable of emitting a high-frequency coded light signal (si) towards the outside of the vehicle, said light signal being included at least in a predefined range of wavelengths, - light receiving means (32) comprising at least one photonic receiver (321) capable of receiving a reflected light signal (s2) contained in light arriving from outside the vehicle and heading towards the photonic receiver, said light comprising the reflected light signal (s2) and an uncoded light, the reflected light signal (s2) coming from a reflection on an obstacle (6), of the light signal (si) emitted by the light emitting means,and at least one focusing device (9) for the light arriving from outside the vehicle to direct it towards the photonic receiver, - means for demodulating (38) the reflected light signal (s2) received by the photonic receiver, and - obstacle detection means comprising means for calculating a distance to the obstacle as a function of a demodulated signal supplied by the demodulation means (39) and the light signal (si) emitted by the photonic transmitter, the optical system (1) being characterized in that the light receiving means (32) comprise a plurality of focusing devices (9, 91, 92, 93), each focusing device (9, 91, 92, 93) of said plurality of focusing devices being configured to focus the light on the same receiving surface of one or more photonic receivers (321) and oriented differently from the other focusing devices,the optical system (1) comprising means for selective activation (100) of at least one of the focusing devices (9, 91, 92, 93).,

2. Optical system (1) according to claim 1, wherein the means for selectively activating at least one of the focusing devices (9, 91, 92, 93) comprise means for adjusting (100) the optical transmissivity of said at least one focusing device.

3. An optical system (1) according to claim 2, wherein the means (100) for adjusting the optical transmissivity of a focusing device (9, 91, 92, 93) is configured to switch from an active state of passing light rays of the given predefined wavelength range to an inactive state of blocking these light rays.

4. An optical system (1) according to claim 3, wherein each focusing device (9, 91, 92, 93) is equipped with a transmissivity adjustment means (100, 101, 102, 103), the transmissivity adjustment means of the focusing devices being driven synchronously, one of the adjustment means being in an active state while the other adjustment means are in an inactive state.

5. Optical system (1) according to one of claims 3 or 4, in which the demodulation means (38) receive information on the active and inactive states of the adjustment means (100, 101, 102, 103) of the transmissivity of the focusing devices.

6. Optical system (1) according to one of claims 3 to 5, in which the means (100, 101, 102, 103) for adjusting the optical transmissivity is controlled to have a time in which it remains active of the order of ten milliseconds.

7. Optical system (1) according to one of claims 3 to 6, in which the time taken for a means (100, 101, 102, 103) for adjusting the transmissivity of a focusing device to switch between an active state, respectively inactive, and an inactive state, respectively active, is less than 5 ms.

8. Optical system (1) according to one of claims 2 to 7, wherein the means (100, 101, 102, 103) for adjusting the transmissivity of a focusing device is a liquid crystal element.

9. An optical system (1) according to any preceding claim, wherein the focusing devices (9, 91, 92, 93) have different optical properties from one focusing device to another.

10. Optical system (1) according to any one of the preceding claims, in which the receiving means (32) further comprise means (8) for filtering the light heading towards the at least one photonic receiver (321), these filtering means (8) being arranged downstream and / or upstream of the focusing devices (9, 91, 92, 93).

11. Optical system (1) according to any one of the preceding claims, wherein the photonic receiver(s) (321) are respectively formed of single-photon avalanche diodes, the light transmitted by each of the different focusing devices (9, 91, 92, 93) being focused on the same set of these diodes.

12. Optical system (1) according to any one of the preceding claims, in which the light emitting means (12) are capable of forming an illumination beam and / or of fulfilling a signaling function.

13. A method for detecting obstacles implementing an optical system (1) according to one of claims 1 to 12, during which the demodulation means (38) provide the obstacle detection means (40) with at least the value representative of the time shift between, on the one hand, the reflected light signal (s2) received by the photonic receiver (321) and, on the other hand, the light signal sent (si) by the photonic transmitter, and during which the selective activation means (100) of at least one of the focusing devices (9, 91, 92, 93) are implemented at regular intervals, so that the focusing devices (9, 91, 92, 93) are activated in turn, information relating to the activation state of each of the focusing devices (9, 91, 92, 93) being known to the obstacle detection means (40).

14. Vehicle comprising an optical system (1) according to any one of claims 1 to 11.

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