OPTICAL PARTICLE DETECTOR

Description

DOMAINE TECHNIQUE DE L'INVENTION

[0001] The present invention relates to the field of optical particle detection in general, and more particularly to particles of micrometer or even nanometer size. Its particularly advantageous, but not limiting, applications include air quality monitoring, the detection of microbiological species, the detection of explosive powders, and alarm systems such as those that identify smoke particles to detect fires. ETAT DE LA TECHNIQUE

[0002] Particle detectors are generally based on analyzing the scattering of light by particles. These detectors typically include optical sensors configured to measure the scattering of light by particles.

[0003] The detectors include a light source that illuminates a channel through which the particles to be detected pass.

[0004] If particles are present in the illuminated area, they will both absorb the light from the source and deflect it away from the main direction of propagation, a phenomenon known as scattering. The angular scattering efficiency is characteristic of the shape, size, refractive index, and concentration of the particles. Recording this angular scattering efficiency therefore allows for the analysis of these various particle parameters.

[0005] Regarding optical particle detection, there are two main detection methods.

[0006] The first method is an obscuration measurement, which is the measurement of light absorption through a cloud or accumulation of particles. This measurement allows the particle concentration to be determined using Beer-Lambert's law if the composition of the particle cloud is known beforehand.

[0007] The second method is a measurement of light scattered off-axis. This measurement allows the particle concentration to be determined according to light scattering theories, for example, Mie theory (Ref: Bohren and Huffmann, Absorption and scattering of light by small particles, Ed. Wiley and Sons, 1983). To analyze the nature of the cloud particles, one can, for example, perform an angular measurement of the scattering, using a goniometer consisting of a photodetector mounted on a rotating arm, or using a discrete array of photodetectors.

[0008] This type of detector has the disadvantages of being very complex, very expensive, and not very robust. Therefore, it cannot be easily transported. Furthermore, it cannot be considered for use in low-cost alarm or measurement systems. However, for example, in the field of fire detection in homes or in the field of air quality monitoring, it is essential to offer solutions that are both cost-effective and highly robust.

[0009] Other optical detection methods have also been proposed.

[0010] For example, optical particle counters operate on the two principles mentioned above, with the particularity that the particle-light interaction zone is geometrically limited by the focusing of a laser source and / or by a microfluidic channel. This geometric limitation of the active zone makes it possible to detect single particles rather than clouds.

[0011] Other optical methods involve observing particles by processing images obtained by microscopy or by holographic reconstruction.

[0012] These methods also exhibit relatively low robustness and high cost.

[0013] US patent 5,719,667 describes a particle detector for a cytometer. This detector comprises a cell 110 through which a fluid containing particles flows. An optical system allows rays scattered by the same particle in different directions to converge onto a single photodetector.

[0014] Document EP 1 987 389 describes a cytometer. Lenses collimate beams from a channel towards a photodetector.

[0015] US document 2014 / 0226158 describes a device for determining particle characteristics.

[0016] These systems do not allow for precise particle detection.

[0017] In order to improve the robustness of particle detectors and reduce their cost, solutions have been proposed to integrate optical detectors into chips using microelectronics and photonics technologies.

[0018] Document FR2963101 describes such a solution. This solution involves a light source carried by a waveguide that illuminates a channel etched into a silicon substrate, through which particles will flow. The diffraction of the incident light by these particles is detected by two peripheral photodetectors embedded in the silicon substrate.

[0019] This solution reduces the sensor's size. However, it is extremely difficult to obtain sufficiently precise and complete information about the particles with this type of solution.

[0020] It is particularly difficult, if not impossible, to analyze or determine the nature of the particles.

[0021] The US2016 / 0077218 A1 document also describes a detector formed on a chip and comprising a photodetector array used to directly image the radiation scattered by particles. With this solution as well, it is difficult to analyze or precisely determine the nature of the particles.

[0022] There are still other methods, this time non-optical, for detecting particles.

[0023] Among these non-optical detection methods, gravimetric measurement involves measuring the mass of an accumulation of particles. A variant consists of measuring the mass of a single particle using an oscillating balance.

[0024] Another non-optical method, particle detection by ionization, involves measuring the change in current induced by an ionized air chamber when particles are present. Furthermore, beta attenuation measurement involves measuring the attenuation of a beta radioactive source through a cloud of particles using a Geiger counter.

[0025] However, the non-optical methods proposed to date present levels of complexity even higher than optical detection methods.

[0026] There is therefore a need to propose a solution to improve the accuracy of information relating to particles, in order for example to determine their nature, while presenting a limited level of complexity or cost and a satisfactory response time.

[0027] This is the objective of the present invention. RESUME DE L'INVENTION

[0028] The present invention relates to a detector according to claim 1 and a method for manufacturing the detector according to claim 13, the detector comprising at least: • a channel intended to receive at least one fluid comprising particles and configured to receive at least one incident light ray emitted by a light source; • at least one array of photodetectors configured so that at least some of the photodetectors receive light rays from the source and scattered by the particles present in the channel.

[0029] The detector further includes at least one optical system intended to be traversed by at least a part of the light rays after their scattering by the particles and before their reception by the photodetectors.

[0030] Each optical system is associated with a photodetector array and presents at least one image focal plane.

[0031] The detector is configured so that, for each optical system, said image focal plane is optically coupled to the photodetector array so that all rays scattered by the particles in parallel directions before passing through the optical system arrive, after passing through the optical system, at the same point in the photodetector array associated with that optical system.

[0032] At least one optical system is convergent so as to converge the light rays from the source and not scattered by the particles towards an image focus located on the image focal plane of the optical system.

[0033] The detector comprises a plurality of optical systems, each optical system being associated with an array of photodetectors, the plurality of optical systems being arranged so as to extend around at least a part of the channel.

[0034] This allows the collection, at the level of the photodetector array, of light rays scattered at a larger scattering angle, particularly if the optical systems are arranged continuously, or at several discrete scattering angles if the optical systems are not arranged continuously. The invention thus makes it possible to increase the accessible diffraction pattern. This allows for the collection of more information about the particles. The accuracy of the analysis and identification of the nature of the particles is therefore improved.

[0035] Thus, at least one optical system is convergent so as to converge the light rays passing through it onto the array of photodetectors associated with this optical system.

[0036] However, the optical system is not configured to collimate the rays.

[0037] The combination of the channel, at least one array of photodetectors and at least one optical system makes it possible to significantly improve the accuracy of the detection and analysis of particles present in the channel, while offering a fast response time.

[0038] Indeed, the claimed detector avoids dazzling the photodetectors with the source beam, or at least only dazzles a small area of ​​the photodetectors. Often, the beam produced by the source, especially when collimated upon impact with the particle, has an optical power several orders of magnitude greater than the power of the rays scattered by the particles. Consequently, the photodetectors receiving the source beam cannot identify scattered rays. Reducing the blinding zone makes it possible to measure particle scattering at low angles of deviation, that is, for scattered rays very close to the beam. The invention thus provides richer information regarding particle scattering. Therefore, the invention improves the accuracy of detection and analysis.

[0039] Furthermore, the detector according to the invention may have a large channel, typically a large channel width (maximum dimension measured in a plane perpendicular to its principal axis of extension). This facilitates the movement of the fluid, and therefore of the particles, within the channel by natural convection and even in the absence of a pump, which is essential for the rapid detection and / or analysis of particles.

[0040] However, thanks to the claimed detector, this large channel dimension does not create positional blur of the particles or creates very limited blur.

[0041] Indeed, with a conventional detector lacking an optical system like that of the detector according to the invention, if a cloud contains particles located at random positions and these particles project scattering patterns translated according to their relative positions, and if the distances separating the photodetectors are of the same order of magnitude as the distances separating the particles in the cloud, then positional blur is expected. This positional blur is all the more significant as the channel width increases. This positional blur leads to a decrease in the sensor's sensitivity as well as a loss of contrast in the information conveyed by the particles' radiation pattern.

[0042] There figure 2 illustrates, in a very schematic way, a solution to the problem of positional blur and the blind spot. In the example shown on this figure 2 , the imager, i.e. the array 230 of photodetectors 231 coincides with the image focal plane 151 of the optical system 15.

[0043] This figure will be described in more detail in the detailed description that follows. However, it appears immediately on this figure 2 , that thanks to the optical system 15, all the scattered rays 12a, 12a' by the particles 61, 61' along parallel directions arrive at the same point of the array 230 of photodetectors 231. In this example the photodetector 231a therefore receives all the light rays 12a, 12a' scattered by the particles 60, 60' along parallel directions.

[0044] Furthermore, the claimed detector ensures that the area of ​​the photodetector array 230 231 impacted by the main beam, i.e., the blinding zone 118, is either a point on the image focal plane 151 (if the source beam is collimated) or, at most, has a very small surface area (particularly if the source beam is not collimated). This area corresponds to the image focus located on the image focal plane 151. Thus, very few photodetectors 231e are blinded. Moreover, light rays 12c', 12d' scattered at very small angles around the main propagation direction 105 of the incident light received by the channel 20 will be detected. Indeed, the photodetectors 231c, 231d, which receive these light rays 12c', 12d', are not blinded.

[0045] Thus, with the claimed detector, all scattered light rays oriented in the same direction fall on a single point on the imager. Scattered light rays oriented at two different angles upon reaching the optical system fall on two distinct points on the imager. All scattered light rays oriented at the same angle (i.e., the same scattering angle) upon reaching the optical system fall on the imager, distributed along the same circle. These rays, scattered by the same particle along non-parallel directions but at the same scattering angle, thus arrive at the same circle on the imager.

[0046] Thus, the rays scattered by the same particle reach photodetectors in concentric circles or arcs of circles depending on their respective diffraction angles.

[0047] Thus, the resulting image is an angular image of the scattering of a particle cloud, and this image is independent of the individual position of each particle. We can therefore consider the resulting image to be a spatial Fourier transform of the cloud's radiation.

[0048] Therefore, compared to solutions such as those described in the prior art FR2963101 or US2016 / 0077218 A1 mentioned above, the invention offers a particularly effective solution for improving the accuracy or sensitivity of information relating to particles, in order for example to determine their nature, while presenting a limited level of complexity, a limited cost and a satisfactory response time.

[0049] It should be noted that, according to one embodiment of the invention, each optical system is not necessarily convergent. Thus, it is possible to have no optical system configured to converge the light rays passing through it. In this case, the detector does not offer the advantages mentioned above regarding the reduction of the blind spot.

[0050] The present invention also relates to a system comprising a detector according to any one of the preceding claims, wherein the system is taken from: a fire alarm system, a fire detection system, a fluid quality analysis system such as air or water, a pollution alarm system, an explosive powder detection system, a microbiological species detection system.

[0051] The present invention also relates to a method for manufacturing a particle detector, comprising at least the following steps: • Provide at least one optical circuit comprising at least one optical system, preferably a plurality of optical systems. • Provide at least one optronic circuit comprising at least one substrate carrying at least one photodetector array, preferably a plurality of photodetector arrays. • Superimpose the optical circuit and the optronic circuit such that the image focal plane of the optical system is optically coupled to the photodetector array, so that all rays scattered by the particles along parallel directions before passing through the optical system arrive, after passing through the optical system, at the same point on the photodetector array associated with that optical system.

[0052] This process has the advantage, among others, of being easily reproducible and of allowing the obtaining of an accurate detector at a limited cost.

[0053] According to one embodiment, a point on the image focal plane of each optical system corresponds to a unique point on the photodetector array associated with that optical system.

[0054] According to an optional embodiment, the optical circuit further includes a passage and the optronic circuit further includes an aperture, and in which the superposition step of the optical circuit and the optronic circuit is carried out so as to arrange the passage and the aperture opposite each other to define at least part of the channel. BREVE DESCRIPTION DES FIGURES

[0055] The aims, objects, features and advantages of the invention will become clearer from the detailed description of embodiments thereof, which are illustrated by the following accompanying drawings in which: There figure 1 is a diagram illustrating the asymmetrical structure of optical systems with respect to the principal direction of propagation. In this non-limiting example, the detector comprises five optical systems. figure 2 illustrates, in a very schematic and enlarged manner, a portion of the figure 1 . This figure 2 clearly illustrates the advantages offered by the invention in terms of reducing angular blur and reducing the blind spot area. La figure 3 is a cross-sectional view in the (x, y) plane of a non-limiting example of a particle detector according to the invention. figures 4a et 4b illustrate, in a highly schematic way, top views of the optical circuit and the optronic circuit of the detector according to the example shown in figure 3 . THE figures 5a à 5e illustrate steps in an example of a process for forming the optical circuit equipping the detector according to the embodiment illustrated in figure 3 . THE figures 6a et 6b illustrate steps in an example of a process for forming the optronic circuit equipping the detector according to the embodiment illustrated in figure 3 . There figure 7 illustrates the assembly stage of the optical circuit and the optronic circuit obtained at the end of the steps shown on the figures 5e And 6b . There figure 8a , illustrates, in a very schematic way, the optical system equipping the optical circuit used in the embodiments shown on the figures 3 , 5a has 5e And 7 . There figure 8b ,illustrates, in a very schematic way, an alternative optical system to the one represented in figure 8a . There figure 9 is a diagram illustrating an alternative embodiment to that of the figure 1 On this figure 9 The asymmetrical structure of the optical systems comprises seven optical systems distributed around the channel. figure 10 is a diagram illustrating an alternative embodiment to that of the figure 1 On this figure 10 The asymmetrical structure of the optical systems comprises three optical systems distributed around the channel. For the sake of brevity, on these figures 9 et 10 Photodetector arrays are not shown.

[0056] The accompanying drawings are provided by way of example and are not intended to limit the scope of the invention. These drawings are schematic representations and are not necessarily to scale for practical applications. In particular, the relative dimensions of the various layers, optical systems, reflective surfaces, channels, photodetectors, and other structures are not representative of reality. DESCRIPTION DETAILLEE DE L'INVENTION

[0057] It is specified that, within the framework of the present invention, the terms "on," "overcome," "cover," or "underlying," or their equivalents, do not mean "in contact with." Thus, for example, the deposition of a first layer on a second layer does not necessarily mean that the two layers are directly in contact with each other, but it does mean that the first layer at least partially covers the second layer, either by being directly in contact with it or by being separated from it by at least one other layer or element.

[0058] Unless specifically stated otherwise, technical features described in detail for a given embodiment may be combined with technical features described in the context of other embodiments described by way of example and not limitation.

[0059] In the context of the present invention, the term "particle," or its equivalents, is defined as a constituent of a physical system considered elementary with respect to the properties under study. For example, a particle is a piece of matter whose largest dimension is less than a few millimeters (10⁻³ meters), preferably one millimeter, and preferably a few tens of micrometers (10⁻⁶ meters), and preferably less than one micrometer, or even on the order of a nanometer (10⁻⁹ m). More generally, particles have a size of 40 Å (10⁻¹⁰ m) and are therefore considered optically continuous. In general, they are objects composed of matter whose dimensions are small compared to the dimensions of the particle flow channel.

[0060] In what follows, the term "diffraction", "diffusion" or their equivalents refer to the phenomenon by which a propagation medium produces a distribution, in many directions, of the energy of an electromagnetic wave, light for example.

[0061] In this description, a material is considered transparent if it allows at least 50% of light radiation to pass through, preferably at least 75% and advantageously at least 90%.

[0062] In what follows, the term "reflection" or its equivalents refers to the phenomenon of re-emission of incident light from an element or surface. In this description, an element is considered reflective if it re-emits at least 50% or more of the incident light. A reflectivity coefficient ranges from 0% for a non-reflective element to 100% for an element that fully reflects incident light.

[0063] Before proceeding with a detailed review of embodiments of the invention, optional features that may be used in combination or alternatively are listed below: In one example, at least one optical system has an optical axis, and at least one optical system is convergent so that light rays converge toward the optical axis before reaching the photodetector array. The detector is configured so that, preferably for each optical system, the image focal plane is optically coupled to the photodetector array. This ensures that rays scattered by particles in different directions before reaching, and therefore before passing through, the optical system arrive, after passing through the optical system, at distinct points on the photodetector array associated with that optical system. Thus, if the size of the photodetectors is sufficiently small, the rays scattered by the particles in different directions before reaching the optical system arrive, after passing through the optical system, at distinct photodetectors on the photodetector array.The detector is then capable of identifying and differentiating rays scattered at different scattering angles. The detector is configured so that the image focal plane of the optical system is optically coupled to the photodetector array, such that all rays scattered by a particle in non-parallel directions and at the same scattering angle, before reaching the optical system and therefore before passing through it, arrive at distinct points on the photodetector array associated with that optical system, these points being located on the same circle.

[0064] This allows us to reconstruct a complete scattering diagram. For example, we can obtain a representative value of the scattered intensity for each scattering angle. This enables a very precise analysis of the particles. The optical system is convergent so that the light rays from the source converge to at least one image focus located on the image focal plane of the optical system. More precisely, the optical system is convergent: ∘ so that the light rays from the source that have not been deflected by the particles converge to one image focus, called the principal image focus, located on the image focal plane; ∘ and so that the rays scattered by the particles converge to other image focuses, called secondary image focuses, which are located on the image focal plane. Each optical system is associated with an array of photodetectors and has a single image focal plane. In one embodiment, each optical system is convergent so that the light rays passing through each optical system converge. Thus, both blurring and the blind spot are considerably reduced.The detector does not include any optical elements between the optical system and the particles. In other words, all elements that modify the scattered rays, particularly their direction, belong to the optical system. For example, the image focal plane of the optical system is optically coupled to the photodetector array such that each point of the image focal plane of the optical system corresponds optically, according to a bijective function, to a point of the photodetector array associated with that optical system. There is a bijective correspondence between each point of the image focal plane of at least one optical system and each point of the photodetector array. For example, the image focal plane of the optical system coincides with the photodetectors of the photodetector array associated with that optical system. Thus, in this embodiment, the imager is placed at the image focal plane of the optics, typically a converging lens.This is therefore the most direct coupling. This makes the manufacturing process more reliable and reduces the detector's size. For example, the image focal plane of the optical system is located at a distance (i.e., a non-zero distance) from the photodetectors of the photodetector array associated with this optical system.

[0065] For example, an intermediate element, such as a transparent layer, is placed between the system, the image focal plane and the photodetectors.

[0066] In this embodiment, the intermediate layer and the optics are configured such that there is a one-to-one correspondence between each point of the grating and each point of the image focal plane. According to one embodiment, this intermediate layer is provided that it does not deviate the light rays.

[0067] Other types of coupling can be implemented between the image focal plane and the photodetector array. For example, the intermediate layer can be designed to converge or, conversely, diverge the light rays. In one embodiment, each optical system within the plurality of optical systems presents a unique image focal plane. In another example, the plurality of optical systems is arranged to extend around the entire channel. This allows for an increased diffraction pattern, further improving the accuracy of the analysis and identification of the particle nature. In yet another example, the plurality of optical systems is arranged continuously around the entire channel, enabling the collection of the scattering pattern over 180° or even 360°. The invention thus allows for the collection of a greater quantity of information, thereby improving particle detection and the identification of their parameters, such as size, optical diffraction index, or nature.In one example, the photodetector arrays associated with the optical systems form a photodetector matrix. This matrix may be rectangular or non-rectangular. Thus, in this example, there is no discontinuity between the different arrays associated with the different optical systems. In another example, each optical system has at least one image focal plane and one optical axis. The detector is configured so that all rays scattered by the particles along parallel directions before passing through the optical system converge at the same point on the image focal plane. The detector is configured so that all rays scattered by the particles at the same angle, for example, relative to the optical axis, before reaching and thus passing through the optical system, converge at the same circle on the image focal plane.Since the detector is configured so that each point of the image focal plane corresponds bijectively to a point in the photodetector array, all these rays scattered along parallel directions reach the array forming a circle or a point. In one example, the photodetectors of the photodetector arrays are arranged along curves with iso-values ​​of the scattering angles. In another example, the number N of optical systems is odd, preferably N = 3, 5, or 7. In yet another example, the detector is configured so that the scattering pattern of the particles has an axis of symmetry that coincides with a principal direction of propagation of the incident light radiation propagating in the channel. Preferably, the optical systems of the plurality of optical systems are distributed asymmetrically with respect to said principal direction of propagation.

[0068] One difficulty arising from a conventional assembly of several optical systems is that the lens tips of these systems exhibit aberrations. Furthermore, the areas at the interface between two lenses may not be imaged correctly.

[0069] By planning an asymmetrical assembly of lenses with respect to the main direction of propagation, we can find the unimaged angles which are in the vicinity of the boundary of two lenses because the scattering information is also carried by the symmetrical angles (with respect to the main direction of propagation) which are not at the boundary of two lenses.

[0070] There figure 1 will be described in detail in the section relating to the detailed description. However, it appears immediately on this figure 1 that the zones Z1' and Z2, located at the boundary between two adjacent lenses, will not be imaged or will be poorly imaged. However, the information carried by the light rays arriving in these zones can be recovered in the zones Z1 and Z2', which are symmetrical to zones Z1' and Z2 with respect to the principal direction of propagation. Furthermore, thanks to the asymmetrical assembly of the optical systems, these zones Z1' and Z2 are not located at the boundary between two optical systems and will be perfectly imaged.

[0071] This allows the angular image to be reconstructed with perfect precision. In one example, the detector comprises an optical circuit, the optical circuit comprising a plurality of optical systems. In another example, the detector comprises an optical circuit forming a single unit. This means, for example, that the optical circuit is formed as a single piece. It can be manipulated in its entirety by grasping any one of its parts. Manipulating one of the optical systems of the optical circuit results in the manipulation of the plurality of optical systems. This single unit is distinct from the optronic circuit.

[0072] According to an example of an embodiment, an optical circuit also presents a passage forming at least part of the channel.

[0073] According to another example, the detector includes an optical circuit that does not form a single unit.

[0074] According to one example, the detector also includes an optronic circuit comprising a substrate carrying at least one of the photodetector array and said source, the optronic circuit having an opening opposite the passage.

[0075] The optical circuit forms a single unit. Preferably, before assembly of the optical and optronic circuits, the optronic circuit forms a single unit separate from the optical circuit. In one example, the optical circuit and the optronic circuit are superimposed and preferably in contact. This particular example applies both to cases where the optical circuit is not a single unit and to cases where it is a single unit. This specific example allows for a very complete particle scattering diagram. It thus significantly improves the accuracy of the information gathered about the particles. Furthermore, this embodiment has the advantage of considerably reducing the system's footprint. In particular, the area occupied by the optronic circuit is reduced. Similarly, the area occupied by the optical circuit is reduced.

[0076] The optical circuit extends between two parallel planes P1, P2. The optronic circuit extends between two parallel planes P3, P4. P1, P2, P3 and P4 are parallel.

[0077] The interface formed between the optical circuit and the optronic circuit is a plane parallel to P1, P2, P3 and P4. If the optical circuit and the optronic circuit are in contact, this interface corresponds to P2 and P3. In one example, the photodetector arrays extend, preferably all in the same plane, and the optical systems include reflective optics configured to reflect the rays scattered by the particles toward that plane. In another example, the detector further includes at least one source configured to emit at least one incident light beam and a substrate. At least one of the photodetector arrays and the source is carried by the substrate. In another example, the detector includes several optical systems, and the focal planes of the optical systems are coplanar. This simplifies the implementation of the circuit carrying the imagers.In one example, the detector further comprises at least one source configured to emit at least one light beam and a substrate, and at least one photodetector array and the source are mounted on the substrate, preferably on a front face of the substrate. In one example, the channel extends along a principal extension direction. The at least one photodetector array extends primarily in a plane (yz) perpendicular to said principal extension direction (x) of the channel. The detector comprises said source, said source emitting light beam along a principal emission direction parallel to said principal extension direction (x) of the channel and perpendicular to said plane (yz) in which at least one photodetector array extends primarily.According to one example, said at least one optical circuit comprises: at least one lens defining said image focal plane optically coupled to the photodetector array, at least two reflective optics, comprising for example reflective surfaces, configured to reflect the rays emitted by the source back to said at least one lens.

[0078] The present invention finds its preferred field of application in the detection of particles of various sizes, preferably in the microscopic or even nanometric range. For example, the present invention can be used to detect particles from fumes, explosive powder, polluting particles, dust particles, allergen particles such as pollen and mold spores, carcinogenic particles, or biological particles such as bacteria, viruses, or exosomes.

[0079] The present invention applies to any type of particles carried by a fluid, whether liquid and / or gaseous.

[0080] The fluid present or flowing in the channel is, for example, air. This is the case for detectors integrated into the following systems: a fire alarm system, a fire detection system, an explosive powder detection system, a system for analyzing the quality of a fluid such as air, and a pollution alarm system.

[0081] Alternatively, the fluid can be a liquid such as water. This is the case for detectors integrated into microbiological species detection systems.

[0082] A simplified example of a detector according to the invention will now be described with reference to figures 1 et 2 , to understand how it works.

[0083] The detector includes a channel 20 intended to receive at least one fluid containing 60 particles. On the figure 1 , channel 20 extends in a direction parallel to the x-axis of the orthogonal xyz coordinate system.

[0084] The detector also includes an optical input allowing a light source 210 to emit light rays into channel 20. The light beam from source 210 is preferably collimated as it enters channel 20. Conventional optics can be used for this purpose. Inside channel 20, the beam has a principal propagation direction 105 parallel to the y-axis.

[0085] The light rays of this beam, when they reach a particle 60, are deflected with respect to this main direction of propagation 105.

[0086] The detector includes optical systems 15a-15e arranged to collect the light rays scattered by the particles 60. Each optical system 15a-15e has an image focal plane and converges all the light rays scattered by the particles along parallel directions into a single point on this image focal plane.

[0087] Furthermore, a 230a-230e array of photodetectors 231 is associated with each optical system 15a-15e. Each photodetector 231 may consist of, or be composed of, a photodiode. Each array of photodetectors 231 may or may not form a photodetector matrix. Alternatively, the photodetectors 231 in the array may be distributed along curves with equal diffraction angles, as will be explained in detail later.

[0088] The 230a-230e arrays of photodetectors 231 and the optical systems 15a-15e are coupled so that the light rays scattered by the particles along parallel directions all arrive at the same point of an array 230a-230e of photodetectors 231. In this way, the invention makes it possible to reduce, or even eliminate, the angular blur which is usually induced when particles, positioned randomly, project scattering patterns translated according to their relative positions and when the distance separating these particles is of the same order of magnitude as the distance separating the photodetectors of an array.

[0089] On the contrary, the invention provides that all parallel rays fall on a single point on the imager. Thus, the image obtained is an angular image of the scattering of a particle cloud. This image is independent of the individual position of each particle. The resulting image is therefore a spatial Fourier transform of the radiation from the particle cloud. Consequently, the invention makes it possible to considerably increase the sensitivity of the detector and the contrast of the information conveyed by the particle radiation pattern.

[0090] There figure 2 is a partial and enlarged view of the dotted area referenced "A" in figure 1 On this figure 2 The light rays 12a and 12a' are scattered by the particles 60 and 60' along parallel directions. The same is true for the pairs of light rays 12b, 12b' and 12c, 12c'.

[0091] In this figure, the optical system includes a converging lens 150 which converges the light rays towards its image focal plane 151.

[0092] According to a first embodiment illustrated on this figure 2 The image focal plane 151 coincides with the imager formed by the array 230 of photodetectors 231. Thus, the refracted rays 13a, 13a' corresponding to the parallel scattered rays 12a, 12a' arrive at the same point of the image focal plane 151, ideally on the same photodetector 231a of the array 230. The same is true for the refracted rays 13b, 13b' corresponding to the parallel scattered rays 12b, 12b'.

[0093] According to an alternative embodiment, but also illustrated on this figure 2 The image focal plane 151 does not spatially coincide with the imager formed by the array 230' of photodetectors 231a'-231d'. Indeed, the photodetectors 231a'-231d' are contained within a plane 234 located at a distance from the image focal plane 151 of the lens 150. In this case, an intermediate element 300 is provided, configured so that each point of the image focal plane 151 corresponds, bijectively, to a point of the array 230'. Thus, in this embodiment as well, the invention makes it possible to reduce, or even eliminate, positioning blur.

[0094] This intermediate element 300 can be configured so as not to deflect the rays arriving at the image focal plane 151, as illustrated in this figure 2 In another embodiment, the intermediate element 300 is a converging optic, which can be advantageous for reducing the size of the photodetector array relative to the size of the optical system. Furthermore, in the case of semiconductor photodiodes, this also helps reduce dark noise. Indeed, the dark current is proportional to the surface area of ​​the photodiode.

[0095] According to another embodiment, the intermediate element 300 is a diverging optic, which can be advantageous for enlarging the angular scattering diagram at the level of the grating and thus for analyzing the scattering of particles with even greater precision.

[0096] By reducing or eliminating positioning uncertainty, the invention allows for a channel with a cross-sectional area of ​​20 mm, measured in the yz plane. This enables a high fluid flow rate through natural convection. The invention therefore improves detector response time even without a pump. This advantage is particularly important in alarm systems, such as fire alarm systems.

[0097] This figure 2 It also clearly shows that the optical system allows the beam passing through channel 20 to converge into a limited area, or even a point on the image focal plane 151 and therefore on the grating 230, 230'. Indeed, the parallel rays 111a, 111b passing through channel 20 and not scattered arrive at a small area, or even at a single point on the grating 230. The blinding zone 118 is therefore very limited. Ideally, it is limited to an area corresponding to a photodetector 232e. This area corresponds to the image focus (also called the principal image focus). Outside this area, the photodetectors are not blinded and can therefore provide the information necessary for the detection and analysis of particles. This is the case, for example, of photodetectors 231c, 231c' and 231d, 231d' which are in the immediate vicinity of the blind zone 118.Thus, the invention makes it possible to detect very small diffusion angles, which makes it possible to further enrich the diffusion diagram and improve the accuracy of detection and analysis.

[0098] As illustrated in figure 1 It is advantageous to arrange several optical systems 15a-15e around the channel 20. Preferably, an array 230 of photodetectors 231 is associated with each of the optical systems 15a-15e. Preferably, but not limited to, the optical systems completely surround the channel 20. Preferably, they form a continuous perimeter around the channel. Thus, the detector can recover the scattered rays in all directions of the yz plane. The complete scattering pattern of the particles can therefore be obtained.

[0099] It should be noted that according to an alternative embodiment, the optical systems do not completely surround channel 20 and / or are not arranged continuously around channel 20.

[0100] Also advantageously, the optical systems 15a-15e are arranged around the channel in a non-symmetrical manner with respect to the main direction of propagation 105 of the light radiation in the channel 20.

[0101] As previously mentioned, the lens tips induce aberrations, and the angular zones Z1', Z2 at the boundary between two lenses introduce risks of misalignment. Considering that the 60 particles have no preferred orientation and are considered statistically spherical, the scattering pattern on these 60 particles exhibits an axis of symmetry that coincides with the principal propagation direction 105 of the light radiation in the channel 20. In theory, a 180° scattering pattern is complete since it is symmetrical with respect to the principal propagation direction 105.By planning an asymmetrical assembly of optical systems 15a-15e with respect to this main propagation direction 105, we can find the angular zones Z1', Z2 not or poorly imaged which are in the vicinity of the boundary of two lenses because the scattering formation is also carried by the angular zones Z1 and Z2', respectively, symmetrical with respect to this direction 105, these symmetrical angular zones Z1 and Z2' not being located at the boundary between two lenses.

[0102] For example, in order to avoid taking into account the angular zones Z1', Z2 which are not imaged or are poorly imaged, one of the following solutions, or even a combination of these solutions, can be implemented: Do not include photodetectors to collect the rays from these areas. In this case, the rays from these areas reach substrate 201 without encountering any photodetectors. Do not include electrical connections for the photodetectors, which are positioned to collect the rays from these areas. This embodiment has the advantage of simplifying the arrangement of the photodetectors on the optronic circuit, particularly when they form arrays, as the exclusion of some of the photodetectors is then handled during the electrical connections. Include a mask between the image focal plane and the photodetectors to block or absorb the rays from these areas. The mask is configured to absorb some, and preferably all, of the incident light. Include a signal processing step to remove the information from the photodetectors that received the rays from these areas.

[0103] Preferably, an odd number of optical systems are used. In the example illustrated in figure 1 Five optical systems are used. The embodiments illustrated in figures 9 et 10 The detector comprises seven and three optical systems respectively to completely surround channel 20. In other embodiments, a greater number of optical systems may be provided. As indicated above, the configuration and relative arrangement of these optical systems are asymmetrical with respect to the principal propagation axis 105 of the light rays.

[0104] Thus, the schematic illustrations of figures 1 et 2 These features clearly demonstrate the advantages of the invention in terms of reducing positioning flux, minimizing the blind spot, and increasing the extent of the detected angular radiation pattern. All these effects contribute to improving the quantity and accuracy of information obtained on particle scattering. They also enhance the detector's sensitivity and response time.

[0105] The invention thus makes it possible to significantly improve the detection and analysis of the nature of particles.

[0106] A particular example of a detector according to the invention will now be described with reference to figures 3 And 4This particular example provides a very complete particle scattering diagram. It thus significantly improves the accuracy of the information gathered about the particles. Furthermore, this embodiment allows for a substantial reduction in the detector's footprint. In particular, its surface area, measured perpendicular to the main channel extension, and its thickness, measured parallel to the main channel extension, can be very small.

[0107] The detector comprises an optical circuit 100 and an optronic circuit 200 whose assembly defines the channel 20.

[0108] The optical circuit 100 comprises several optical systems 15a-15e arranged around the passage forming part of the channel 20. Each optical system includes several diopters 150a-150d, spherical, aspherical, or free-form, segmented between air and a transparent dielectric material. This transparent dielectric material can, for example, be a polymer-based resin.

[0109] Each optical system also includes reflective optics. These reflective optics include, or are formed, for example, of one or more reflective surfaces 160a-160b. On the figures 5b , 8a et 8b These reflective surfaces (160) are illustrated by thick dashed lines. These reflective optics are formed, for example, using a metallic deposit such as gold, aluminum, or interfering dielectric mirrors.

[0110] These optics project the spatial Fourier transform of the radiation from the particles 60 present in channel 20 onto an image focal plane 151 (yz) perpendicular to the principal extension direction of the channel (x direction). These optics also collimate the beam emitted by the source 210 within channel 20, and then project this beam onto a spatially reduced area at the image focal plane to minimize blinding, as described above.

[0111] Preferably, the focal planes of the optical systems 15a-15e of the optical circuit 100 are coplanar (parallel to the yz plane in the example of the figure 3 ).

[0112] The optronic circuit 200 is a circuit fabricated on a substrate 201, preferably a semiconductor, for example monocrystalline silicon. This optronic circuit 200 carries an array 230 of photodetectors 231 associated with each optical system. Thus, on the figure 3 The 230d network is associated with the 15d optical system.

[0113] Preferably, the photodetectors 231 of the array 230 follow the curves 232 of the iso-values ​​of the scattering angles, that is to say the projection by lenses of coaxial cones centered on the direction 105. These curves 232 of the iso-values ​​of the scattering angles thus form arcs or portions of rings.

[0114] Alternatively, the photodetectors 231 of each array 230 form a matrix of photodetectors 231. It can also be foreseen that the same matrix forms the whole of the arrays 230.

[0115] As previously stated, each optical system 15 is optically coupled with the associated array 230 of photodetectors 231 in such a way that there is a bijective optical correspondence between each point of the image focal plane 151 of the output 102 of the optical system 15 and each point of this array 230.

[0116] For example, we can predict that the plane 234 containing the photodetectors of the 230d array coincides with the image focal plane 151d of the optical system 15d. In this case, the contact plane between the optical circuit 100 and the optronic circuit 200 coincides with the image focal plane 151 of the optical systems 15 and the plane 234 containing the photodetectors of the 230d array.

[0117] Alternatively, an intermediate element 300 can be provided which imposes a distance d between the image focal planes 151 of the optical systems and the arrays 230 of photodetectors 231. This distance d is referenced in figure 3 .

[0118] Preferably, the photodiode arrays are aligned opposite the optical systems. In alternative embodiments, the intermediate element 300 provides optical coupling between the optical systems 15a to 15d and the photodetector arrays 231 to ensure bijective matching, without the optical systems being aligned with the photodetector arrays. This embodiment is not illustrated in the figures.

[0119] As illustrated in the example of the figure 3 The optronic circuit 200 also includes the source 210.

[0120] The source is, for example, a surface-emitting light source, such as a surface-emitting LED or a VCSEL (vertical-cavity surface-emitting laser). This circuit optionally contains an electronic processing system. This circuit 200 also contains a through-hole 250, which, when combined with the passage 140 of the optical circuit 100, defines at least part of the channel 20.

[0121] Preferably, the substrate 201 has a front face 202, which carries, or at least through which are accessible, the source 210 and the arrays 230 of photodetectors 231.

[0122] As illustrated in this example, the optical circuit 100 extends between two parallel planes P1, P2. The optronic circuit 200 extends between two parallel planes P3, P4. P1, P2, P3, and P4 are parallel when the optical circuit 100 and the optronic circuit 200 are superimposed. The planes P1, P2, P3, and P4 are parallel to the YZ plane of the xyz coordinate system shown in figure 3 .

[0123] The interface formed between the optical circuit 100 and the optronic circuit 200 is a plane parallel to P1, P2, P3 and P4. If the optical circuit and the optronic circuit are in contact, this interface corresponds to P2 and P3.

[0124] There figure 4a illustrates, in top view, the arrangement in the yz plane, of five optical systems 15a-15e which completely surround channel 20.

[0125] There figure 4b illustrates, in top view, the arrangement in the yz plane, of five 230a-230e arrays of photodetectors which completely surround channel 20.

[0126] The source 210 is arranged so that the beam passing through the channel 20 defines a main propagation direction 105. The optical systems 15a-15e and the gratings 230a-230e are arranged asymmetrically with respect to this direction 105. As explained above, this allows for a correct image of the scattering pattern from 0° to 180°.

[0127] The optronic system 200 is thus formed of segments 260a-260e which preferably surround the channel 20 and preferably form a continuous perimeter. Segment 260a carries source 210. It collects backscattered radiation. Segment 260b collects back-side and side scattering radiation. Segment 260c collects forward-side and side scattering radiation. Segment 260d collects forward scattering radiation. Segment 260e collects side scattering radiation.

[0128] Thus, the set formed by the optical systems 15a-15e collects all the rays scattered by the particles 60. The entire radiation pattern can thus be determined.

[0129] There figure 4b The electrical outputs 233 of the detectors are also shown. If the electronic processing system is deferred, then there are as many electrical outputs as there are photodiodes. If the electronic processing system is integrated, then there are only the electrical outputs of the circuit after processing.

[0130] With reference to the figure 3 An example of an optical circuit 100 will now be described in detail. This optical circuit 100 is specifically configured to: collimater, at least in channel 20 the beam from source 210, this collimated beam having a direction (y) parallel to the plane 234 (yz) in which the arrays 230a-230d of photodetectors 231 extend and perpendicular to the main direction (x) of extension of channel 20, bring back to the plane 234 (yz) the rays scattered by the particles 60, so that these rays are collected by the photodetectors 231.

[0131] For this purpose, the optical circuit 100 has an entrance 101 through which the rays 111a, 111b emitted by the source 210 enter. In this example, the rays 111a, 111b illustrate the contour of the beam emitted by the source. Preferably, this entrance 101 is positioned directly above the source 210. A first lens 150a, forming two diopters, is positioned directly above the entrance 101 so as to allow the rays 111a, 111b to pass through it. The rays refracted 112a, 112b by this lens 150a are reflected by a first reflective surface 160a. The reflected rays 113a, 113b by this reflective surface 160a pass through a second lens 150b which preferably forms part of the wall of the channel 20. This lens 150b preferably allows the collimation of the beam 114a, 114b passing through the channel 20. Some of the rays of this beam are deflected by the particles 60. These scattered rays are referenced 12a, 12b, 12c.Some of these scattered rays 12a, 12b pass through a lens 150c of a second optical system 15d. The scattered rays 121a, 121b that have passed through the lens 150c are reflected by a reflective surface 160d of this second optical system 15d. This reflective surface 160d reflects 122a, 122b these scattered rays towards a lens 150d of this second optical system 15d.

[0132] The 150d lens is configured to direct the rays 122a, 122b onto the 230d array of photodetectors 231. The rays exiting the 150d lens are referenced 117a, 117b in figure 3 They escape from the optical system through optical output 102d.

[0133] The optical system 150d is configured so that all the rays scattered by the particles along parallel directions in the channel 20 arrive at the image focal plane 151d of this optical system 150d at the same point and arrive at the same point of the array 230d of photodiodes 231. On the other hand, as before, the rays scattered by the particles along non-parallel directions in the channel 20 arrive at the image focal plane 151d of this optical system 150d at distinct points and then also arrive at distinct points of the array 230d of photodiodes 231.

[0134] According to the same principle, all the parallel rays forming the collimated beam passing through channel 20 (the beam being schematically delimited by the two rays 114a, 114b), and which are not scattered by the particles 60, arrive at the same point on the image focal plane 151d and therefore at the same point on the imager. They thus only dazzle a small area of ​​the imager, ideally a single photodetector. The path of the rays of the collimated beam that are not scattered by the particles 60 is illustrated by references 115a, 115b, 116a, 116b, 117a, 117b.

[0135] Thus, the optical systems 15a, 15d are convergent such that the light rays not scattered by the particles 111a, 111b and the light rays scattered by the particles 12a-13a, 12b-13b converge towards at least one image focus located on the image focal plane 151d of the optical system 15d. More precisely, the optical system 15d is convergent, ∘ so that the light rays from the source 210 and which have not been deflected by the particles 60 converge towards an image focus, which can be designated as the principal image focus, and located on the image focal plane 151d; ∘ and so that the rays scattered 12a-13a, 12b-13b by the particles 60 converge towards other image focuses, designated as secondary image focuses, which are also located on the image focal plane 151d.

[0136] As illustrated in the example figure 3 Each of the 150a-150d lenses consists of one or more spherical or aspherical diopters. According to other examples not shown, each lens may consist of segmented diopters.

[0137] According to an advantageous but not limiting embodiment, as illustrated in figure 8a The optical elements 150 can be covered entirely or partially with an anti-reflective coating 153. The reflective surfaces 160 are obtained, for example, by metallization. Some or all of the other surfaces of the optical system 15 can be covered with an absorbing surface 155 formed, for example, of a dark film, such as black paint. On the figures 5b , 8a et 8b , these absorbing surfaces 155 are illustrated by thick continuous lines.

[0138] In these examples, the optical systems 15 each comprise two optical elements. Each optical element comprises two diopters. Preferably, each optical element is a spherical or aspherical lens 150 in this example. The optical system 15 includes a support 156. The support 156 carries the reflective optics, such as the reflecting surface 160. The support 156 also carries the two lenses 150, 150. These two lenses 150, 150 are preferably attached to the support 156. The implementation of this type of optical system will be described in detail with reference to the figures 5 à 7 This optical system comprises five diopters. Within this optical system, light rays propagate through the lenses and into the air.

[0139] According to another example of implementation, illustrated in figure 8b The optical system 15' comprises a single optical piece 150'. This optical piece 150' has three diopters. A first diopter 153a is configured to direct the incident rays onto a second diopter forming a reflective optic (reflecting surface 160). This second diopter 160 is configured to reflect the rays towards a third diopter 153b.

[0140] The first 153a and third diopter 153b, for example, are coated with an anti-reflective coating. On the figures 5d , 8a et 8b These anti-reflective coatings are illustrated by alternating short and long thick lines. Other surfaces are preferably covered with an absorbent surface 155, for example, a dark film.

[0141] In this embodiment, the optical component 150' is monolithic. It is preferably formed from a single piece. It has no aperture. Within this optical system, the light rays do not propagate through air but only through the material, for example, a polymer-based resin. This improves the robustness of the optical system. Furthermore, it reduces manufacturing and alignment errors among the various optical elements forming the same optical system. This embodiment thus simplifies the process, reduces costs, and improves measurement accuracy.

[0142] THE figures 5 à 7 illustrate an example of a detector manufacturing process according to the figure 3 .

[0143] THE figures 5a à 5e illustrate the implementation of optical circuit 100.

[0144] The optical circuit 100 can be made in two parts 157, 170 by embossing or by injection molding of a transparent dielectric material, for example a polymer-based resin.

[0145] A first part 157 defines the supports 156 for the lenses 150. This first part 157 also acts as a support for the reflective surfaces 160.

[0146] This first part 157 is, for example, obtained by molding from a mold formed from parts 401 and 402 illustrated in figure 5a .

[0147] A second part 170 carries the lens assembly 150. This part 170 is obtained, for example, by molding from a mold formed by parts 501 and 502 illustrated in figure 5c .

[0148] Once each of the parts 157, 170 is molded, its material is hardened, for example with a thermal annealing step, and then it is demolded. This yields the parts 157, 170 whose shapes are illustrated in figures 5b et 5d .

[0149] If necessary, the lenses 150 intended to form part of the channel are tilted to provide a clearance angle that facilitates the demolding step. This tilt can be compensated for by the other optical elements of the optical circuit 100.

[0150] Preferably, each of the molded parts is the size of a wafer, that is to say a slice of semiconductor material obtained by conventional microelectronic processes, typically a disk of 200 or 300 mm.

[0151] Once the parts have hardened, the surfaces are then polished. It is necessary to have optically high-quality surfaces, that is, surfaces with low roughness. To form the reflective surfaces 160, some walls of the supports 156 are metallized (for example, with gold or aluminum). It is also possible to deposit anti-reflective coatings 153 on the diopters of the lenses 150 and to deposit an anti-reflective coating 155, for example, black absorbent paint, on surfaces other than the mirrors and the diopters of the lenses.

[0152] These different layers are illustrated on the figures 5b et 5d .

[0153] The two parts 157 and 170 are then assembled. In the illustrated example, this assembly is carried out wafer to wafer, for example with adhesive or with a plasma surface treatment. This step is shown schematically in figure 5e .

[0154] THE figures 6a et 6b illustrate an example of a process for manufacturing the 200 optronic circuit of the figure 3 .

[0155] Starting from a semiconductor substrate 201, for example monocrystalline silicon, photodetectors, for example photodiodes, are fabricated. Preferably, the light source 210 is also fabricated from this substrate 201. This light source 210 is preferably a surface emission source.

[0156] Preferably, the photodetectors, the 210 source, and even the processing electronics, are manufactured using conventional microelectronic and optoelectronic techniques. This step is illustrated schematically in 6a.

[0157] A deep etching is then performed throughout the substrate 201 to structure the opening 250, which will partially define the fluidic channel 20. This opening 250 is through-hole. This step is shown schematically in figure 6b .

[0158] Finally, as illustrated in figure 7 The optical circuit 100 is hybridized with the optronic circuit 200 by aligning the optics opposite the photodiodes. The assembly, preferably wafer-to-wafer, can be carried out with optical adhesive or with a plasma surface treatment.

[0159] In view of the preceding description, it is clear that the invention offers an effective solution for improving the sensitivity and accuracy of the detector as well as its response time.

[0160] The invention is not limited to the embodiments described but extends to any embodiment falling within the scope of claim 1.

[0161] In particular, any of the variants proposed below can be envisaged and implemented in combination with any of the embodiments described above.

[0162] One alternative approach involves using a second material, preferably a dielectric, to create achromatic refractive optics, instead of making optical systems from a single material. This allows, for example, the relocation of light rays with different wavelengths to a single point.

[0163] It is also possible to expect the optical circuit 100 to receive light beams of different wavelengths. For example, the optical system 100 can be optically coupled with several optical sources, these optical sources emitting different wavelengths. This allows, in particular, for a more precise analysis of their nature.

[0164] Another advantageous approach is to implement polarization control, either at the source or via a polarizing lens. This allows for two scattering diagrams, ultimately improving the analysis.

[0165] Another variation involves recycling the light using a mirror cavity to allow the light from the source to make multiple passes through the channel, thus improving the sensor's sensitivity. These mirrors are preferably placed between the source and the image of the source formed by the optical system. Therefore, these mirrors would be positioned above the glare zone. Naturally, these mirrors would not be positioned above photodetectors that are not located within the glare zone. An example of this mirror positioning is illustrated in figure 3 by reference 180. REFERENCES

[0166] 100. Optical circuit 101. Optical input 102. Optical output 105. Main direction of light propagation in the channel 111. Rays emitted by the source 112, 113, 114. Refracted and / or reflected rays 118. Blind spot 12. Light rays scattered by the particle 121, 122. Rays refracted by a lens after scattering by a particle 13. Light rays at the output of the optical system 140. Passage 15. Optical system 150. Lens 151. Image focal plane 152. Optical axis 153. Anti-reflective surface 155. Absorbing surface 156. Support 157. Support piece 160. Reflective surface 170. Optical piece 180. Mirror 20. Channel 60. Particle(s) 200. Optronic circuit 201. Substrate 202. Front panel 210. Source 211. Main emission direction 230. Photodetector array 231. Photodetectors 232. Iso-value curves 233. Electrical outputs of the photodetectors 234. Plan containing the photodetectors 250. Aperture 260. Segments 300. Intermediate element 401, 402. Mold part 501, 502. Mold part

Claims

1. Particle detector (60) comprising at least: - one channel (20) intended to receive at least one fluid comprising particles (60) and configured to receive at least one light radiation (111a, 111b, 114a, 114b) emitted by a light source (210); - at least one photodetector (231) network (230) configured such that at least some of the photodetectors (231) receive light beams emitted by the source and diffused by the particles (60) present in the channel (20); in which - the detector further comprises at least one optical system (15) configured to be passed through by at least some of the light beams after their diffusion by the particles (60) and before they are received by the photodetectors (231), - each optical system (15) is associated with a photodetector (231) network (230) and has an image focal plane (151), - the detector is configured such that said image focal plane (151) of the optical system (15) is optically coupled to the photodetector (231) network (230), such that all the beams diffused by the particles (60) along parallel directions before passing through the optical system (15) reach, after passing through the optical system (15), one same point of the photodetector (231) network (230) associated with this optical system (15), - the at least one optical system (15) is convergent, so as to make the light beams coming from the source and not diffused by the particles converge towards an image focus located on the image focal plane (151) of the optical system (15), - said image focal plane (151) of the optical system (15) is optically coupled to the photodetector (231) network (230), such that all the beams diffused by the particles (60) along non-parallel directions before passing through the optical system (15) reach, after passing through the optical system (15) distinct points of the photodetector (231) network (230) associated with this optical system (15) characterised in that the detector comprises a plurality of optical systems (15b, 15c, ...), each optical system (15b, 15c, ...) being associated with a photodetector (231) network (230), the plurality of optical systems (15b, 15c, ...) being disposed so as to extend around at least one part of the channel (20).

2. Detector according to the preceding claim, wherein the image focal plane (151) of the optical system (15) is either combined with the photodetectors (231) of the photodetector (231) network (230) associated with this optical system (15), or is located at a distance from the photodetectors (231) of the photodetector (231) network (230) associated with this optical system (15).

3. Detector according to any one of the preceding claims configured such that said image focal plane (151) of the optical system (15) is optically coupled to the photodetector (231) network (230) such that all the beams diffused by a particle (60) along non-parallel directions and along one same diffusion angle, with respect to an optical axis of the system, before passing through the optical system (15) reach, after passing through the optical system (15), distinct points of the photodetector (231) network (230) associated with this optical system (15), these points being located over one same circle.

4. Detector according to any one of the preceding claims, wherein the plurality of optical systems is disposed so as to extend around all of the channel (20), and preferably disposed continuously around all of the channel (20).

5. Detector according to any one of the preceding claims, wherein the photodetectors (231) of the photodetector (231) network (230) are disposed along isovalue curves (232) of diffusion angles.

6. Detector according to any one of the preceding claims, wherein the number N of optical systems is odd, preferably with N = 3, 5 or 7.

7. Detector according to any one of the preceding claims, configured such that a diffusion figure of the particles (60) has an axis of symmetry which coincides with a main propagation direction (105) of the incident light radiation (111a, 111b, 114a, 114b) propagating in the channel (20), and wherein the optical systems (15) of the plurality of optical systems are distributed non-symmetrically with respect to said main propagation direction (105).

8. Detector according to any one of the preceding claims, comprising an optical circuit (100) forming a one-piece assembly, the optical circuit (100) comprising the plurality of optical systems (15) and further having a passage (140) partially forming at least the channel (20), the detector also comprising an optronic circuit (200) comprising a substrate (201) carrying at least one from among the photodetector (231) network (230) and said source (210), the optronic circuit (200) having an opening (250) facing the passage (140), the optical circuit (100) and the optronic circuit (200) being superposed and preferably in contact.

9. Detector according to any one of the preceding claims, wherein the photodetector (231) networks (230) extend, preferably all, in one same plane (231) and wherein the optical systems (15) comprise reflective optics configured to reflect the beams diffused by the particles (60) in the direction of said plane (234).

10. Detector according to any one of the preceding claims, further comprising said at least one source (210) configured to emit said at least one light beam and a substrate (201), and wherein the at least one photodetector (231) network (230) and the source (210) are carried by the substrate (201), preferably by a front face (202) of the substrate (201).

11. Detector according to any one of the preceding claims, wherein the channel (20) extends along a main extension direction (x), wherein the at least one photodetector (231) network (230) extends mainly into a plane (234) (yz) perpendicular to said main extension direction (x) of the channel (20), and the detector comprising said source (210), said source (210) emitting a light radiation along a main emission direction (211) parallel to said main extension direction (x) of the channel (20) and perpendicular to said plane (234) (yz), into which the at least one photodetector (231) network (230) mainly extends.

12. System comprising a detector according to any one of the preceding claims, wherein the system is taken from among: - an anti-fire alarm system, - a fire direction system, - a system for analysing the quality of a fluid such as air or water, - an anti-pollution alarm system, - an explosive powder detection system, - a microbiological species detection system.

13. Method for manufacturing a particle (60) detector according to any one of claims 1 to 11, the method comprising at least the following steps: - providing at least one optical circuit (100) comprising at least one optical system (15), preferably a plurality of optical systems, - providing at least one optronic circuit (200) comprising at least one substrate (201) carrying at least one photodetector (231) network (230) and preferably a plurality of photodetector (231) networks (230), - superposing the optical circuit (100) and the optronic circuit (200) such that said image focal plane (151) of the optical system (15) is optically coupled to the photodetector (231) network (230) such that all the beams diffused by the particles along parallel directions before passing through the optical system (15) reach, after passing through the optical system (15), one same point of the photodetector (231) network (230) associated with this optical system (15).