Photonic sensor assembly of an optical system configured for obstacle detection

Abstract

Title of the invention: Photonic sensor assembly of an optical system configured for obstacle detection. The present invention relates to a photonic sensor assembly (32) comprising an electrically insulating support (50), photonic receivers (321, 322) positioned on the electrically insulating support (50) and forming a light-receiving zone, and a protective wall (70) disposed to cover the reception zone. The photonic sensor assembly (32) is characterized in that a filling material (78) is interposed between the reception zone and the protective wall (70). Abstract figure: Figure 2

Description

Title of the invention: Photonic sensor assembly of an optical system configured for obstacle detection

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

[0002] In modern motor vehicles, light-emitting diode (LED) assemblies are commonly used to create external lighting devices such as low-beam or signal lights. These LED assemblies can also be used, in addition to their lighting functions, for obstacle detection.

[0003] It is particularly possible to use light-emitting diodes (LEDs) in LiDAR (Light Detection and Ranging) technologies. Such LiDAR technologies, which are otherwise very expensive, utilize optical systems already installed on the vehicle for regulatory signaling and lighting applications. These existing optical systems are adapted for obstacle detection. For example, it is known to increase the bandwidth of LEDs, which emit light in the visible spectrum, to use equalization techniques, to use LEDs smaller than 300 micrometers, or to combine these techniques. The LEDs used are, for example, blue LEDs adapted to emit white light.

[0004] In this context, it is known that optical systems have photonic receiving devices capable of receiving and processing a light signal from outside the vehicle.

[0005] These photonic receiving devices include, for example, photodiodes arranged on an electrically insulating support. In addition to this electrically insulating support, the photodiodes are surrounded by air and are further protected by a protective wall. It is then necessary to manage optical crosstalk phenomena, in which the successive passage of the light signal from outside the vehicle through the protective wall and the air creates unwanted reflections, i.e., interference. This interference, resulting from the successive passage through different media with different refractive indices, can distort the information received by the photodiodes and, consequently, the detection of obstacles by the optical system.

[0006] Furthermore, ambient light can saturate the photodiodes, which are then unable to transmit information related to obstacle detection.

[0007] The present invention aims to overcome this drawback by proposing a photonic sensor assembly in which interference due to unwanted reflections of the light signal at each change of material is limited by the presence of a material disposed between the photodiodes and the protective wall, this material also preventing saturation of the photonic receptors of the photonic sensor assembly.

[0008] The main object of the present invention is a photonic sensor assembly comprising an electrically insulating support, photonic receptors positioned on the electrically insulating support and together forming a light-receiving zone, and a protective wall arranged to cover the receiving zone. According to the invention, a filling material is interposed between the receiving zone and the protective wall.

[0009] The photonic sensor assembly according to the invention is intended to equip an automotive optical system for obstacle detection applications. The photonic sensor assembly, also called a photonic sensor device, comprises photonic receivers, in particular a sensor equipped with single-photon avalanche diodes (SPADs). These photonic receivers are arranged on an electrically insulating support, on which they form a receiving area for a light signal. This light signal provides information on the presence of obstacles within a road scene around the automotive vehicle. It is understood that the photonic receivers contribute to forming a sensor for the light signal within the photonic sensor assembly.

[0010] The photonic sensor assembly also includes a protective wall, which is located opposite the electrically insulating support with respect to the photonic receptors. This protective wall is, for example, transparent or translucent in a certain particular configuration. The protective wall protects the photonic receptors against shocks or scratches that could damage them.

[0011] The photonic sensor assembly includes a filling material disposed between the photonic receiver area and the protective wall. In other words, the filling material is a layer interposed between the photonic receivers and the protective wall. The filling material is thus disposed within a volume delimited, in a direction perpendicular to the electrically insulating support, by the receiver area and the protective wall, this volume being further delimited laterally, that is to say in planes parallel to the electrically insulating support, by a protective material different from the protective wall.

[0012] In prior art photonic receiving devices, the volume occupied by the filling material was filled with air. Since the filling material is disposed of in a pre-existing volume within the photonic sensor assembly, it does not complicate the manufacturing operations of said photonic sensor assembly. Furthermore, it does not interfere with a replacement of the protective wall if necessary, particularly if it is damaged.

[0013] The presence of a filling material helps to limit the interference phenomena previously generated by the successive passage through the protective wall and the air. In the prior art, light rays passed through the protective wall, were at least partially reflected upon passing through the receiving zone, and these reflected light rays struck the protective wall before being reflected again towards the receiving zone, thus creating a detection signal even in the absence of obstacles. The filling material also has a filtering function in order to select only the wavelengths used in obstacle detection, thereby preventing the saturation of the photonic receptors.

[0014] According to an optional feature of the invention, the filling material is a transparent resin.

[0015] The filler material is an optically transparent resin or an optically clear resin. The filler material is, for example, sand-cured adhesive silicone.

[0016] According to an optional feature of the invention, the filling material is in contact with the receiving area and in contact with the protective wall.

[0017] In other words, the filling material fills an entire volume between the receiving area and the protective wall.

[0018] According to an optional feature of the invention, the photonic sensor assembly includes a protective material covering a portion of the electrically insulating support devoid of photonic receptors and surrounding the receiving area and the protective wall.

[0019] The photonic receptors are, for example, arranged in a central area of ​​the electrically insulating support, with the protective material covering a peripheral area devoid of these photonic receptors. The protective material is, for example, a thermosetting resin such as epoxy.

[0020] According to an optional feature of the invention, the filling material is configured to generate at least a bandwidth of light rays over a given wavelength range. In this way, the filling material is capable of blocking a portion of the light spectrum, namely the portion of the light spectrum that is not intended to carry information relating to the reflection of a light signal by a potential obstacle.

[0021] Depending on the embodiment, the filling material is configured to form a single bandwidth or a plurality of bandwidths. The filling material then acts as a filter layer. The sensitivity of the sensor formed by the photonic receptors depends on the quality of the filtering function of the filling material. In particular, the bandwidth is configured to block light other than blue light, which contains the information necessary for obstacle detection.

[0022] According to an optional feature of the invention, the filling material includes a high-pass filter.

[0023] This high-pass filter integrated into the filling material blocks light rays with a wavelength shorter than 420 nm. In other words, the composition of the filling material allows it to absorb wavelengths shorter than 420 nm. Thus, the cutoff wavelength of the filling material is approximately 420 nm.

[0024] According to an optional feature of the invention, the filling material includes a low-pass filter.

[0025] This low-pass filter integrated into the filling material blocks light rays with a wavelength greater than 460 nm. In other words, the composition of the filling material allows it to absorb wavelengths with a value greater than 420 nm.

[0026] According to an optional feature of the invention, the filter of the filling material is made in the form of a dye embedded in the filling material and configured to block light rays of a given wavelength.

[0027] This dye is thus configured to block a portion of the light spectrum. More specifically, the dye only allows blue light to pass through.

[0028] In alternative embodiments, the filling material is configured to allow red light to pass through.

[0029] The filling material is, according to the embodiments, either in solid form, or it is a material in liquid form which undergoes a hardening operation at the end of which it is made solid.

[0030] According to an optional feature of the invention, the photonic sensor assembly includes a filter film disposed on the protective wall.

[0031] This filter film constitutes an additional means of preventing the saturation of photonic receptors.

[0032] According to an optional feature of the invention, the protective wall comprises an inner face in contact with the filling material and an outer face in contact with the filter film.

[0033] It is understood that the filter film is disposed on an external surface of the assembly photonic sensor. Thus, the filter film is opposed to the filling material with respect to the protective wall.

[0034] According to an optional feature of the invention, the filter film is a low-pass filter.

[0035] The low-pass filter of the filter film is then added to the high-pass filter of the filling material. The high-pass filter is included in the filling material rather than in the filter film because the latter has, comparatively, a greater thickness of material which allows it to block UV rays.

[0036] According to an optional feature of the invention, a refractive index of the filling material is substantially equivalent to a refractive index of the protective wall and / or the receiving area.

[0037] The term "equivalent" means that the refractive index is the same as, or differs by no more than 10% from, that of the protective wall or the receiving area. This minimizes refraction between the protective wall and the filling material, and / or between the filling material and the receiving area, thereby improving the efficiency of the entire photonic sensor assembly.

[0038] According to an optional feature of the invention, a refractive index of the filling material is between a refractive index of the protective wall and a refractive index of the receiving area.

[0039] The closer the refractive index of the filling material is to the refractive index of the protective wall, the greater the quantity of light rays that can reach the photonic receivers. Conversely, the closer the refractive index of the filling material is to that of the receiving area, the more the phenomenon of stray rays and interference is limited, it being understood that a non-negligible quantity of light rays may in this case fail to penetrate the receiving means beyond the protective wall. The refractive index is thus chosen based on a compromise between, on the one hand, the efficiency of the photonic sensor assembly, which requires the passage of a sufficient quantity of light rays, and, on the other hand, the need to avoid optical crosstalk.

[0040] According to an optional feature of the invention, the refractive index of the filling material corresponds to an average between the refractive index of the protective wall and the refractive index of the receiving area.

[0041] Such a configuration makes it possible to limit crosstalk as much as possible within the photonic sensor assembly, the reflections then being substantially equivalent between the protective wall and the filling material on the one hand and the filling material and the receiving area on the other hand.

[0042] According to an optional feature of the invention, the refractive index of the the filling material is closer to the refractive index of the receiving area than to the refractive index of the protective wall.

[0043] According to an optional feature of the invention, the refractive index of the filling material is closer to the refractive index of the protective wall than to the refractive index of the receiving area.

[0044] These are two alternative configurations, in which the refractive index of the filling material is respectively similar to the refractive index of the receiving area and similar to the refractive index of the protective wall. In the first case, the reflection of light rays is non-negligible as they pass from the protective wall to the filling material, while in the second case, the reflection of light rays is non-negligible as they pass from the filling material to the receiving area. To avoid crosstalk resulting from such reflections, it is possible in both cases to add an anti-reflective coating to the interface between the filter film and the protective wall.

[0045] According to an optional feature of the invention, the refractive index of the filling material is between 1.3 and 3.5.

[0046] The refractive index of the filling material may be, in particular, around 1.3 when it is desired to have a nearly identical refractive index between the protective wall and the filling material, while a refractive index of the filling material may be around 3.5 when it is desired to have a nearly identical refractive index between the filling material and the receiving area. For example, when the filling material is silicone, its refractive index is 1.4, and for a glass protective wall, its refractive index is between 1.5 and 1.7.

[0047] The invention further relates to an optical system for detecting obstacles in a motor vehicle comprising a photonic emitter configured to emit a high-frequency coded light signal, the light signal being at least within a predefined range of wavelengths in the visible spectrum, preferably a range of wavelengths between 420 and 460 nanometers, a photonic sensor assembly according to any one of the preceding claims configured to receive a reflected light signal from a reflection on an obstacle of the light signal emitted by the photonic emitter, means for detecting obstacles, and means for demodulating the reflected light signal, the obstacle detection means comprising means for calculating a distance to the obstacle as a function of a demodulated signal provided by the demodulation means and the light signal emitted by the photonic emitter.

[0048] The optical obstacle detection system according to the invention is integrated within a motor vehicle. In addition to the obstacle detection function, the optical system is also configured for lighting and / or signaling functions. The optical system comprises a photonic emitter and a photonic sensor assembly, respectively configured to emit and receive a light signal. Based on a delay between the light signal received by the photonic sensor assembly and the light signal emitted by the photonic emitter, the optical system is able to detect the presence of obstacles and, if applicable, their distance from the motor vehicle.

[0049] Other features, details and advantages of the invention will become clearer upon reading the following description on the one hand, and the illustrative and non-limiting examples of embodiments given with reference to the accompanying drawings on the other hand, in which:

[0050] [Fig.1] illustrates, schematically, an optical obstacle detection system for a motor vehicle according to the invention, comprising in particular a photonic emitter and a photonic sensor assembly;

[0051] [Fig.2] illustrates, schematically, a perspective view of the photonic sensor assembly of [Fig.1], a portion of a protective wall of this sensor assembly having been partially removed;

[0052] [Fig.3] illustrates, schematically, a cross-sectional view of the photonic sensor assembly of [Fig.1] as a whole;

[0053] [Fig.4] illustrates, schematically, a cross-sectional view of part of the photonic sensor assembly of [Fig.1].

[0054] The features, variants, and different embodiments of the invention can be combined in various ways, provided they are not incompatible or mutually exclusive. In particular, variants of the invention may be conceived comprising only a selection of features, described hereafter in isolation from the other described features, if this selection of features is sufficient to confer a technical advantage and / or to differentiate the invention from the prior art.

[0055] In the figures, the elements common to several figures retain the same reference.

[0056] Fig. 1 schematically illustrates the operation of an optical obstacle detection system 1. This optical system 1 is integrated within a motor vehicle in order to perform, on the one hand, an obstacle detection function, and on the other hand, at least one lighting function such as a lighting function or a signaling function.

[0057] Obstacle detection uses, on the face of the vehicle integrating this function, at least one photonic emitter 12, for example in each optical block of the vehicle where the optical system 1 is intended to detect frontal obstacles, and at least one photonic sensor assembly 32, also in each optical unit of the vehicle. The photonic emitter 12 comprises, for example, two blue light-emitting diodes 121, 122, adapted to emit white light. The light-emitting diodes 121, 122 are, for example, adapted to produce a light beam of a daytime running light.

[0058] The photonic sensor assembly 32, which will be described in more detail below, is, for example, a sensor comprising photonic receivers 321, 322, here in the form of single-photon avalanche photodiodes or SPAD photodiodes (from the English Single-Photon Avalanche Diode) such as the SPAD photodiodes referenced 321, 322. For illustrative purposes, [Fig. 1] shows only two light-emitting diodes 121, 122 and two photodiodes 321, 322 for simplicity. Many more photodiodes are preferentially used, and daytime running lights can use many more diodes.

[0059] The photonic emitter 12 is capable of emitting a high-frequency coded light signal outside the vehicle, and the photonic sensor assembly 32 is capable of receiving a corresponding reflected light signal s2, arriving from outside the vehicle.

[0060] In order to form the high-frequency coded light signal s 1, each optical block includes a source 10 of voltage square wave electrical signals 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 wave signal of width 1.

[0061] The light signal Σ sent by the diodes 121, 122 of the photonic emitter 12 encodes a specific sequence of "spots" or light peaks of width 1, this sequence repeating cyclically. In other words, the light signal Σ is modulated according to a specific data sequence, called a modulating sequence. The sequence of spots is defined so as to easily evaluate a time lag between its emission and its reception as explained below.

[0062] The reflection of the light signal si on an obstacle 6 gives rise to the reflected light signal s2 of sufficient light power to be captured by the photodiodes 321, 322 of the photonic sensor assembly 32.

[0063] The photonic sensor assembly 32 comprises, for example, in addition to the photodiodes 321, 322, a blue light filter 8 for filtering the light from the reflected light signal s2 so as to allow only the blue component of this light to pass through, and a lens 9 focusing this component towards the photodiodes 321, 322. The blue light emitted by the diodes 121, 122 generally has a lower luminous intensity than sunlight, but approaches it for wavelengths close to 460 nm. Modulation of the reflected signal s2 makes it possible to distinguish it of external light pollution in a demodulation process of this reflected light signal s2. The demodulation process makes it possible in particular to eliminate, in the reflected light signal s2, parasitic light signals emitted by other vehicles.

[0064] More specifically, the photodiodes 321, 322 capture the blue components of the reflected light signal s2 and 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. Since the photodiodes 321 and 322 are SPAD photodiodes, the electrical signal 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 involves retaining in the time-counting signal Nb only those values ​​exceeding a number of photons corresponding to the intensity of the blue component of sunlight, resulting in a thresholded light signal s3. Such thresholding eliminates the component due to sunlight from the received electrical signal. Here, a "thresholded light signal" is defined as an electrical or digital signal that actually corresponds to the thresholding of the received light signal s2.

[0065] The demodulation means 38 include the thresholding means 34 which are implemented by software or analog means from an unthresholded electrical signal from the photodiodes 321, 322.

[0066] The demodulation means 38 also include correlation means 36 of the thresholded light signal s3, once demodulated, with the light signal si sent by the diodes 121, 122 of the photonic emitter 12. These correlation means 36 determine a time shift r between the demodulated thresholded light signal s3 and the sent light signal si, 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 thus enable the detection of this obstacle. Described differently, 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, at least a representative value of a time shift r between on the one hand the reflected light signal s2 and on the other hand the light signal emitted si by the photonics 121, 122.

[0067] The photonic sensor assembly 32 of the optical system 1 will now be detailed with respect to figures 2 to 4.

[0068] The photonic sensor assembly includes an electrically insulating support 50 which This is a printed circuit board, or PCB, for example, made of epoxy resin. This electrically insulating substrate 50 comprises a first face 52 and a second face 54 opposite each other in a direction perpendicular to a principal extension plane of the electrically insulating substrate 50. The first face 52 receives a plurality of electrical connection terminals 56, which take the form of solder points. The second face 54 carries an electronic chip 58 made up of different layers of semiconductors and metallic deposits. The electronic chip 58 is attached to the electrically insulating substrate 50, for example by gluing. This electronic chip 58 is made of a substrate within which the photonic receptors 321, 322 are inserted; these photonic receptors 321, 322 correspond to SPAD photodiodes as previously described.The photonic receivers 321, 322 form a light receiving zone which is configured to receive the reflected light signal s2 arriving from outside the motor vehicle and containing information on the presence of possible obstacles.

[0069] On an edge of the receiving area formed by the photonic receivers 321, 322, the photonic sensor assembly 32 includes cathodic connection terminals 60. These cathodic connection terminals 60 are connected to the electrical connection terminals 56 by means of metal wires 62, which for this purpose pass through the electrically insulating support 50. The metal wires 62 are, for example, gold wires.

[0070] As can be particularly seen in Figures 2 and 3, the electronic chip 58 does not extend over the entire second face 54 of the electrically insulating support 50. The electronic chip 58 is in fact arranged in a central area 64 of the electrically insulating support 58, that is to say, at a distance from its end edges connecting the first face 52 and the second face 54. The electrically insulating support 50 includes, between the central area 64 and its end edges, a peripheral area 66. The metal wires 62 pass through the electrically insulating support 50 at the level of this peripheral area 66, that is to say, around the electronic chip 58.

[0071] Since the metal wires 4 are very thin and therefore easily pulled out, the photonic sensor assembly 50 includes a protective material 68 arranged over these metal wires 4. More generally, the protective material 68 covers the peripheral area 66 of the electrically insulating support 50, and extends around the electrical chip 58 and therefore around the receiving area formed by the photonic receivers 321, 322. The protective material is, for example, a sand-colored thermosetting resin.

[0072] The protective material 68 also extends around a protective wall 70 which covers the receiving area. This protective wall 70, for example a pane of glass, is configured to allow light rays to pass through to the receiving area formed by the photonic receptors 321, 322, and is, for example, transparent. The protective wall 70 protects the photonic receptors 321, 322 from external damage or dust.

[0073] The protective wall 70 has an inner face 72 facing the receiving area and an outer face 74 oriented towards an outside of the photonic sensor assembly 32. If the inner face 72 is facing the receiving area, it is nevertheless at a distance from it so that there is a non-zero distance between the inner face 72 of the protective wall 70 and the electronic chip 58 carrying the photonic receptors 321, 322 which form the receiving area.

[0074] In certain embodiments, the outer face 74 of the protective wall 70 is covered by a filter film 76, which is shown in [Fig. 4]. The filter film 76 is configured to block a portion of the light spectrum, so as to prevent saturation of the photonic receptors 321, 322 that the protective wall covers.

[0075] According to the invention, the photonic sensor assembly 32 comprises a filling material 78 which is intercalated between the receiving area on the one hand and the protective wall 70 on the other hand. More specifically, the filling material 78 extends, in a direction perpendicular to the plane of the electrically insulating support 50, between this receiving area and the protective wall, and is laterally bordered by the protective material 68. Thus, this filling material 78 extends from the electronic chip 58, in which the photonic receivers 321, 322 are inserted to form the receiving area, to the inner face 72 of the protective wall 70. The filling material 78 is in contact with both the receiving area and the protective wall 70, so that the entire distance between the inner face 72 of the protective wall 70 and the electronic chip 58 is occupied by the filling material 78.

[0076] The filling material 78 is a transparent resin, for example silicone. During a manufacturing process of the photonic sensor assembly 32, the filling material 78 is placed on the electronic chip 58 and more particularly on the receiving area formed by the photonic receptors 321, 322, being bordered by the protective material, and then it is covered by the protective wall 70.

[0077] The filling material 78 serves to improve the detection accuracy of the photonic sensor assembly by limiting the presence of reflected light rays that could distort obstacle detection by creating interference. Figure 4 illustrates this principle. In Figure 4, the light arriving from outside the motor vehicle, and in particular here in the case where this light carries the reflected light signal s2, is represented by a solid black arrow. The principal path of these light rays, carrying the reflected light signal s2, is such that the rays Light rays pass successively through each layer of the stack formed by the filter film 76, the protective wall 70, and the filling material 78 to reach the receiving zone. More specifically, the light rays pass through the filter film 76, enter the protective wall 70 through its outer face 74, exit through its inner face 72, pass through the filling material 78, and then reach the receiving zone formed by the photonic receptors 321 and 322.

[0078] Each layer of the stack formed by the filter film 76, the protective wall 70, the filling material 78, and the receiving zone has a given refractive index. The transition from one layer to another, depending on the difference in refractive index between the two successive layers, is likely to generate reflected light rays. It is understood that each of these reflected light rays within the stack can generate, through successive reflections, parasitic rays that are responsible for optical crosstalk. More specifically, the presence of parasitic light rays that are successively reflected between the different layers of materials forming the photonic sensor assembly 32 increases the time lag r between the light signal s2 received by this photonic sensor assembly 32 and the light signal si emitted by the photonic emitter 12, which risks disrupting the analysis of this time lag r.

[0079] The greater the difference between two successive refractive indices, the greater the quantity of reflected light rays, such an increase following, for example, Fresnel's laws. The use of the filling material 78 makes it possible to limit the difference between the refractive indices of the materials successively traversed by the light signal s2 and consequently to have a significant impact on the reduction or absence of reflected light rays at the moment of a change of material, which improves the accuracy of the photonic sensor assembly 32 by limiting optical crosstalk.

[0080] The receiving area is here subdivided into pixels 80, with, by way of non-limiting example of the invention, one pixel 80 per photonic receiver 321, 322. As shown in [Fig. 4], the receiving area has a first pixel 80A, a second pixel 80B, a third pixel 80C, and a fourth pixel 80D. In order to allow for precise obstacle detection, it is necessary that the light signal s2 be received by only one given pixel 80, for example, the second pixel 80B as illustrated, and thus to limit the presence of stray rays that are reflected within the material. The filling material 78 prevents the creation of stray light rays that would be reflected when passing from one layer to another towards a pixel other than the second pixel 80B, namely any one of the first pixel 80A, third pixel 80C and fourth pixel 80D.

[0081] More specifically, thanks to the filling material 78 in place of air, The difference in refractive index between the protective layer and the filling material is reduced. This limits the number of light rays reflected outwards when they attempt to enter the photonic sensor assembly 32, but it also limits the reflectivity of light rays already reflected and tending to exit the photonic sensor assembly, as illustrated by the white arrows with black outlines in [Fig. 4]. In this way, the amount of stray rays that can propagate within the photonic sensor assembly through successive reflections is limited.

[0082] The presence of the filling material 78 has the same effect at the boundary with the receiving area, reducing the refractive index difference compared to a configuration where air is present. The amount of rays reflected by the receiving area is reduced, and any potential impacts in terms of the amount of stray rays that could affect a pixel other than the intended one are reduced accordingly. This prevents distortion of the time-shift analysis r.

[0083] A refractive index of the filling material 78 is chosen according to a refractive index of the protective wall 70 and / or according to a refractive index of the receiving area, i.e. of the electronic chip 58. In particular, it may be sought to have a refractive index of the filling material substantially equivalent to a refractive index of the protective wall and / or of the receiving area, in order to locally limit reflections at the level of the diopter formed by the change of medium, at the passage between the protective wall and the filling material on the one hand and between the filling material and the receiving area on the other hand.

[0084] The refractive index of the protective wall 70 is, for example, on the order of 1.5, while the refractive index of the receiving area is between 1.3 and 3.5. A refractive index of 3.5 corresponds to the substrate of the electronic chip 58 that has been doped with silicon particles. In these examples, the refractive index of the filling material is between 1.3 and 3.5.

[0085] More specifically, the refractive index of the filling material 78 can be between the refractive index of the protective wall 70 and the refractive index of the receiving area. In this context, the refractive index of the filling material 78 can be an average of the refractive index of the protective wall 70 and the refractive index of the receiving area. Thus, if the refractive index of the protective wall 70 is 1.5 and the refractive index of the receiving area is 3.5, then the refractive index of the filling material 78 is 2.5. For example, in this case, there would be 5% reflection between the protective wall 70 and the filling material 78, and 5% reflection between the material of filling 78 the reception area.

[0086] Choosing such an average value for the refractive index of the filling material 78 makes it possible to limit the potential reflections of light on both sides of the filling material equally, thus offering a good compromise between the efficiency and accuracy of the system. It ensures that a moderate amount of light rays cannot penetrate the filling material 78 after passing through the protective wall, thereby ensuring the efficiency of the system because a large amount of information is processed. At the same time, it ensures that a moderate amount of the rays that have passed through the filling material are not reflected at the entrance to the receiving zone, thus limiting the creation of stray rays that can generate false detections and reduce the accuracy of the optical system.

[0087] It is possible to vary the refractive index of the filler material 78 according to the proportion of titanium dioxide-charged particles present in the silicone. The higher the proportion of titanium dioxide-charged particles, the higher the refractive index of the filler material 78.

[0088] In addition to preventing the creation of stray light rays, the filling material 78 can act as a filter within the photonic sensor assembly 32, so as to allow only the portion of the light spectrum necessary for obstacle detection to pass to the photonic receptors 321, 322. To this end, the filling material 78 is configured to generate, depending on the embodiment, one or more bandwidths configured to block a portion of the light spectrum by filtering certain wavelengths. The bandwidth(s) formed in the filling material 78 are specifically configured to allow the passage of blue light, which corresponds to the portion of the light spectrum used in obstacle detection. The width and center of this or these transmission bands are set by adjusting the cutoff wavelengths of filters present within the photonic sensor assembly 32.

[0089] Thus, in certain embodiments, the filling material 78 includes a high-pass filter. Such a high-pass filter is configured to prevent the passage of a portion of the light spectrum to the photonic receptors 321, 322. In this case, the high-pass filter blocks light rays with a wavelength shorter than 420 nm; in other words, the cutoff wavelength of the filling material 78 is 420 nm.

[0090] In a first embodiment, the filling material comprises, in addition to the high-pass filter, a low-pass filter configured to block light rays with wavelengths greater than 460 nm. It is understood that the combination of the high-pass filter and the low-pass filter makes it possible to allow only light to pass through. photonic receptors 321, 322 that light rays whose wavelength is between 420 and 460 nm.

[0091] Alternatively, in a second embodiment, the filling material 78 comprises only the high-pass filter as previously mentioned but lacks a low-pass filter. In this case, the filter film 76 carried by the outer face 74 of the protective wall 70 acts as a low-pass filter, i.e., this filter film 76 is configured to have a cutoff wavelength of approximately 460 nm.

[0092] By way of example, the filtering function of the filler material 78 is achieved through the presence of dyes. Thus, the filler material 78 includes a dye, for example, configured to block light rays with a wavelength shorter than 420 nm. Generally, the dye is configured to allow only light rays corresponding to blue light to pass through.

[0093] The present invention thus proposes a photonic sensor assembly of an optical obstacle detection system in which the presence of a filling material between photonic receptors of the photonic sensor assembly and a protective wall thereof makes it possible on the one hand to limit the unwanted reflected rays which would lead to erroneous detections and on the other hand to prevent saturation of the photonic receptors by filtering a part of the light spectrum.

[0094] The present invention is not limited to the means and configurations described and illustrated herein and also extends to any equivalent means and configuration as well as to any technically operative combination of such means.

Claims

Claims

1. A photonic sensor assembly (32) comprising an electrically insulating support (50), photonic receivers (321, 322) positioned on the electrically insulating support (50) and together forming a light receiving area, and a protective wall (70) arranged to cover the receiving area, the photonic sensor assembly (32) being characterized in that a filling material (78) is interposed between the receiving area and the protective wall (70).

2. The photonic sensor assembly (32) of the preceding claim, wherein the filler material (78) is a transparent resin.

3. A photonic sensor assembly (32) according to any preceding claim, wherein the filler material (78) is in contact with the receiving area and in contact with the protective wall (70).

4. A photonic sensor assembly (32) according to any preceding claim, comprising a protective material (68) covering a portion of the electrically insulating support (50) devoid of photonic receivers (321, 322) and encircling the receiving area and the protective wall (70).

5. A photonic sensor assembly (32) according to any preceding claim, wherein the filler material (78) is configured to generate at least one bandwidth of light rays of a given wavelength range.

6. A photonic sensor assembly (32) according to any preceding claim, wherein the filler material (78) comprises a high-pass filter.

7. The photonic sensor assembly (32) of any one of claims 1 to 5, wherein the filler material (78) comprises a low-pass filter.

8. A photonic sensor assembly (32) according to any preceding claim, comprising a filter film (76) disposed on the protective wall (70).

9. Photonic sensor assembly (32) according to the preceding claim, in which the protective wall (70) comprises an internal face (72) in contact with the filling material (78) and an external face (74) in contact with the filter film (76).

10. A photonic sensor assembly (32) according to any one of the claims- claims 8 and 9 in combination with claim 6, wherein the filter film (76) is a low-pass filter.

11. A photonic sensor assembly (32) according to any one of claims 1 to 10, wherein a refractive index of the filler material is substantially equivalent to a refractive index of the protective wall and / or the receiving area.

12. A photonic sensor assembly (32) according to any preceding claim, wherein a refractive index of the filler material (78) is between a refractive index of the protective wall (70) and a refractive index of the receiving area.

13. Photonic sensor assembly (32) according to the preceding claim, in which the refractive index of the filling material corresponds to an average between the refractive index of the protective wall and the refractive index of the receiving zone.

14. The photonic sensor assembly (32) of any one of claims 11 to 13, wherein the refractive index of the filler material (78) is between 1.3 and 3.

5.

15. Optical system (1) for detecting obstacles of a motor vehicle comprising a photonic transmitter (12) configured to emit a high-frequency coded light signal (si), the light signal (si) being at least included in a predefined range of wavelengths in the visible spectrum, between 420 and 460 nanometers, a photonic sensor assembly (32) according to any one of the preceding claims configured to receive a reflected light signal (s2) resulting from a reflection on an obstacle of the light signal emitted by the photonic transmitter, means (38) for demodulating the reflected light signal (s2), and obstacle detection means (40) comprising means for calculating a distance to the obstacle as a function of a demodulated signal provided by the demodulation means (38) and the light signal (si) emitted by the photonic transmitter (12).

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