OPTICAL PARTICLE DETECTOR

Description

TECHNICAL FIELD OF THE 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 applications include, for example, optical particle counting and angular analysis of the scattering of one or more particles.

[0002] Particularly advantageous, but not exhaustive, application areas include: air quality control, detection of microbiological species, detection of explosive powder, fire detection, and alarm systems with low sensitivity to false positives. STATE OF THE ART

[0003] Particles are microscopic solid, liquid, or wet solid objects suspended in the air. Their sizes range from a few tens of nanometers to a few tens of micrometers. These particles originate from various sources such as forest fires, construction sites, industrial sites, motor vehicles, etc.

[0004] When the concentration of these particles exceeds a certain threshold, they have a harmful impact on the environment and / or health. Therefore, some countries have set maximum concentration limits. For example, the European Union allows maximum concentrations of 50 µg / m³ for particles between 10 µm and 2.5 µm in size and 25 µg / m³ for particles smaller than 2.5 µm.

[0005] It is therefore necessary to accurately detect the presence and concentration of these particles by size range.

[0006] Various particle detection methods exist, such as gravimetric detection methods, ionization methods, beta attenuation methods, aerodynamic mobility or electrical mobility measurement methods, and optical detection methods.

[0007] These latter methods are advantageously simpler to implement and more widespread.

[0008] Optical particle detectors are generally based on detecting the interaction between light and particles. In practice, the particles to be detected pass through an area illuminated by a light source. The intersection between the illuminated area and the potential area of ​​particle presence is called the detector's useful detection volume. This useful detection volume is contained within the detector's field of view. The useful detection volume can correspond to the illumination volume.

[0009] If particles are present in the useful detection volume, they will absorb some of the light coming from the source and deflect another part of this light away from the main direction of propagation, according to the phenomenon of scattering.

[0010] A first method of optical detection, called obscuration measurement, consists of measuring the absorption of light through a cloud of particles or an accumulation of particles. This measurement makes it possible to determine the concentration of particles using Beer-Lambert's law if the composition of the particle cloud is known beforehand.

[0011] A second method involves analyzing light scattered off-axis. Angular analysis of scattered light is performed using a scattering diagram. This allows for the determination of the shape, size, refractive index, and concentration of particles. For example, particle size, refractive index, and concentration can be determined from light scattering theories, such as Mie theory (Ref: Bohren and Huffmann, Absorption and scattering of light by small particles, Ed. Wiley and Sons, 1983).

[0012] Optical particle counters operate on the principles described above. Their distinguishing feature is that the detection volume is geometrically limited, for example, by focusing a laser source and / or using a microfluidic channel and / or employing a system of aerodynamic lenses. This geometric limitation of the detection volume allows for the detection of single particles rather than clouds.

[0013] One solution for producing such optical particle counters or detectors while improving their robustness and reducing their cost is to integrate these counters / detectors into miniaturized chips using microelectronics and photonics technologies.

[0014] Document FR3062209 describes such an integrated detector. This detector includes, in particular, a discrete assembly of photodetectors forming a retina, as well as reflective surfaces to project onto the retina the image of the light scattered by the particle(s). A scattering pattern characteristic of the particle is thus obtained.

[0015] One drawback of this detector is that it does not allow for the separation of the scattering patterns of several particles simultaneously present in the detection volume. Indeed, as illustrated in the figure 1When several particles 10₁, 10₂ are illuminated simultaneously within the useful detection volume 100, their respective scattering patterns S₁, S₂ formed on the retina 20 overlap to form a total scattering pattern S₀ with low resolution. This overlap results in a loss of information on the individual patterns S₁, S₂. It then becomes difficult to discern the individual optical and geometric properties of the particles, to estimate the individual positions of the particles, and In short, to count the particles.

[0016] There figure 2A This presents a simulation of an image formed on the retina of such a detector by illuminating a spherical particle with a diameter of 5 µm. This image makes it easy to determine the scattering pattern of this particle.

[0017] There figure 2BThis presents a simulation of an image formed on the retina of such a detector by simultaneously illuminating three spherical particles with diameters of 1 µm, 2 µm, and 5 µm, respectively. This image does not allow differentiation of the scattering patterns of each particle.

[0018] The angular analysis performed by such a detector is therefore not suitable for the simultaneous detection of several particles.

[0019] Furthermore, the light intensity associated with the scattering of particles with larger diameters is much greater than the light intensity associated with the scattering of particles with smaller diameters. In this case, the scattering pattern of a large-diameter particle can obscure that of a small-diameter particle. The comparison of figures 2A, 2B illustrates this problem of detector blinding by the diffusion diagram of the largest diameter particle.

[0020] Another drawback of the detector described in document FR3062209 is the difficulty in detecting small-diameter particles in the presence of large-diameter particles. Reliable detection of these small-diameter particles is crucial, as they are generally the most hazardous to health.

[0021] A known solution for avoiding the analysis of multiple simultaneous scattering is to reduce the detection volume, for example, by reducing the cross-section of the light beam emitted by the source. By geometrically limiting the particle / light interaction area, the probability of multiple simultaneous scattering is reduced. However, reducing the detection volume also reduces the probability of a particle being illuminated by the beam. The detector's sensitivity is therefore decreased.

[0022] To compensate for this decrease in detection sensitivity, it is possible to guide the particle flow towards the reduced useful volume, for example by using a small cross-section fluidic channel or by means of an aerodynamic lens.

[0023] In this case, however, the fluidic response time of the detector is considerably longer. This fluidic response time corresponds to the time required for a particle to pass through the fluidic channel and be detected. An excessively long response time is particularly detrimental to alarm system applications.

[0024] One way to reduce this response time is to use an additional system to force flow convection, such as a fluidic pump or a fan. This significantly increases the complexity and cost of such a miniature detector.

[0025] Another solution to avoid analyzing multiple simultaneous diffusions is to perform a preliminary dilution step of the particle stream before it passes through the detection volume. The particle stream to be analyzed can thus be mixed with a pre-filtered air stream. This solution also makes the detector more complex and reduces its sensitivity.

[0026] Documents US5101113A and US2014 / 152986A1 disclose alternative particle analysis systems. These systems aim to reduce multiple particle detection by using angular filters combined with lens arrays to focus scattered signals onto detectors. The complexity of these systems is high, resulting in lower reliability and greater bulk.

[0027] Therefore, there is a need to reduce or even eliminate at least some of the drawbacks of prior art detectors. One objective of the present invention is to address this need.

[0028] Another objective of the present invention is to provide a solution for discerning diffusion patterns that originate from multiple and simultaneous diffusions.

[0029] Another objective of the present invention is to propose a solution enabling individual analysis of each of said diffusion diagrams, in order to determine individual optical (e.g. refractive index) and / or geometric (e.g. diameter) properties of the particles. SUMMARY OF THE INVENTION

[0030] To achieve these objectives, the present invention proposes an optical particle detector for simultaneously detecting at least one first particle and at least one second particle within a useful detection volume designed to house a fluid carrying particles and to be traversed by incident light rays emitted by at least one primary source. The first and second particles form, respectively, first and second secondary sources, which, when located within the useful detection volume and scattering a portion of the incident light rays, emit, respectively, first scattered light rays and second scattered light rays. This detector comprises a retina formed by a plurality of photodetectors capable of receiving scattered light rays.

[0031] Advantageously, this detector further comprises at least one reticle interposed between the useful detection volume and the retina, and this reticle comprises: at least one optical passage zone allowing passage to the retina of a part of the first scattered light rays (called first scattered part) and a part of the second scattered light rays (called second scattered part), and at least one optical blocking zone preventing passage to the retina of a part of the first scattered light rays (called first blocked part) and a part of the second scattered light rays (called second blocked part).

[0032] At least one of the aforementioned optical passage and blocking zones: is separated from the retina by a minimum distance Z taken along an optical axis (O) normal to the retina, i.e. an axis normal to a plane in which extends mainly a face of the retina turned towards the reticle if the retina is flat, also has at least one dimension a taken along a direction transverse to the optical axis.

[0033] The reticle and the retina are configured, in particular the minimum distance Z and the dimension a, so that the first scattered part is received by a first set of photodetectors whose distribution delimits on the retina a first figure taken from a spot and a shadow, the second scattered part is received by a second set of photodetectors whose distribution delimits on the retina a second figure taken from a spot and a shadow, said second figure being at least partly distinct from the first figure when the first and second parts passing through at least one optical passage zone together define an angle θ ij whose value is at least equal to an angular resolution δθ of the detector.

[0034] This optical detector does not include a lens between the reticle and the retina. The absence of a lens improves the detector's compactness. It also improves the detector's robustness and / or reliability.

[0035] If there is a plurality of particles in the useful volume, the above definition applies to each pair of particles belonging to that plurality of particles.

[0036] For each scattering particle, the scattering pattern received by the photodetectors is, for example, derived from the convolution product of the scattering pattern of the particle by the figure (spot or shadow) projected onto the retina through the reticle.

[0037] The reticle may be dark. In this case, it blocks most of the rays scattered by the scattering particle in question and projects a portion of the scattered light onto the retina as a spot, through at least one optical passage zone, also called the optical aperture. The area occupied by the reticle in the optical blocking zone is greater than the area occupied by the reticle in the optical passage zone. Thus, in this case, the image formed on the retina is a spot.

[0038] With a dark reticle, the spots are easily distinguishable. This type of reticle limits the overlapping of the signatures of each scattering particle. Furthermore, this type of reticle offers very good contrast. In addition, signature analysis is possible across almost the entire spot, even if there are more than three particles.

[0039] The reticle can be clear. In this case, it allows most of the rays scattered by the scattering particle to pass through and projects a shadow onto the retina, formed by at least one area of ​​optical blockage, also called an opaque surface. The area occupied by the at least one area of ​​optical transmission is greater than the area occupied by the at least one area of ​​optical blockage. Thus, in this case, the figure formed on the retina is a shadow.

[0040] With a clear reticle, the analysis area is very large. The projected shadow provides precise and easily identifiable positional information.

[0041] To combine the advantages of dark and light reticles, the reticle can also be designed with sections where the optical transmission areas are larger than the optical blocking areas, and other sections where the optical blocking areas are larger than the optical transmission areas. The reticle of this detector is therefore configured to filter the first and second light rays scattered by the first and second particles, respectively, before the scattered rays are received by the retina. This helps to at least partially prevent these first and second scattered light rays from overlapping on the retina. It also prevents retinal blinding, since not all of the first and second scattered light rays reach the retina.In the case of a dark reticle with one or more optical apertures, this also prevents other rays, such as those from stray light, from reaching the retina. This detector therefore exhibits reduced sensitivity to stray light.

[0042] Indeed, during the development of the present invention, it became apparent that known miniaturized detectors of the prior art have drawbacks related to stray scattering of the source beam on the various detector elements. In these known detectors, since the source beam is several orders of magnitude brighter than the light scattered by the particles, stray scattering can be sufficient to cause noise or even blind the retina, making angular analysis difficult or even impossible. Stray scattering is less problematic for large detectors (i.e., centimeter-sized), because the various scattering elements are farther from the retina and are generally outside the detector's field of view.

[0043] With the detector according to the present invention, after filtration by the dark reticle, the retina thus receives only the first and second scattered parts.

[0044] By cutting off a portion of the first and second scattered light rays, the probability of their overlap on the retina decreases. Specifically, as the first and second particles pass through the detection range, there are necessarily positions within this range where the first and second scattered particles do not overlap on the retina. This allows us to separate the first and second scatter patterns formed by the first and second scattered particles received simultaneously by the retina.

[0045] As illustrated in the figure 3 and unlike the device illustrated in the figure 1Only the first 31 and second 32 scattered parts contribute respectively to the formation of a first and a second scattering pattern S1, S2 on the retina 20. The first scattering pattern S1 therefore corresponds to a sampling of the complete scattering pattern of the first particle 101. Similarly, the second scattering pattern S2 corresponds to a sampling of the complete scattering pattern of the second particle 102. The dark reticle 30 advantageously allows such sampling to be performed by filtering the first and second scattered light rays kd1, kd2. In particular, the complete scattering pattern of the first particle 101 is mainly sampled at an angle θj between the scattered rays kd1 of the first scattered part 31 and the optical axis O.The complete scattering diagram of the second particle 10 2 is mainly sampled at an angle θ i between the scattered rays kd 2 of the second scattered part 32 and the optical axis O. The optical axis O is perpendicular to the retina 20 and more precisely perpendicular to the face of the retina 20 turned towards the dark reticle 30.

[0046] Therefore, the dark reticle 30 allows for the spatial separation of the S1 and S2 diffusion diagrams on the retina 20. As illustrated in the figure 3The position of the bright peak S1 forming the first scattering pattern S1 (θj) is directly related to the angle θj at which the first particle 101 is seen through at least one aperture 301 of the dark reticle 30. Similarly, the position of the bright peak S1 forming the second scattering pattern S2 (θi) is directly related to the angle θi at which the second particle 102 is seen through at least one aperture 301 of the dark reticle 30. Consequently, two particles 101, 102 located at different positions within the useful detection volume 100 project bright peaks S1, S2 at different positions on the retina 20. The bright peaks S1, S2 are thus separated on the retina 20, at their vertices, by a separation distance L Vertices and at the level of their bases by a separation distance L Bases.

[0047] More precisely, L Bases corresponds to the smallest distance between the base BS 1 formed by peak S 1pic and the base BS 2 formed by peak S 2pic. It is not the distance between the vertices SS 1 and SS 2 of these peaks S 1pic and S 2pic. BS 1, BS 2, SS 2, and SS 2 are referenced in figure 3A peak may have a general cone shape (for example, when the aperture is a pinhole). Alternatively, a peak may also have a shape that extends along a straight curve (in the case of an aperture or optical passage forming a straight slit) or along a curvilinear curve (in the case of an aperture or optical passage forming a curved slit or a closed contour). The LBases distance then corresponds to the smallest distance between two adjacent peaks belonging to the projection diagrams of two particles and corresponding to identical areas of the aperture. LBases is measured on the surface of the retina 20 where the first 31 and second 32 scattered parts arrive.

[0048] Advantageously, at least one optical passage zone is further configured so that this separation between the first and second scatter diagrams S1, S2 is sufficiently resolved on the retina 20, that is to say, it corresponds to a separation distance Ls between the spots T1, T2, or a distance L Bases between the bases of the peaks of the light diagrams or a distance L Vertes between the vertices of the peaks of the light diagrams, greater than or equal to K times a step Lpix between two adjacent photodetectors of the retina 20, with K=2, preferably K=5, preferably K=10, preferably K=20.

[0049] The Lpix pitch is measured in a plane parallel to a face of the retina 20 facing the dark reticle 30 if the retina is flat. The Lpix pitch corresponds to the smallest distance between the centers of two adjacent photodetectors.

[0050] The at least one passage zone is preferably dimensioned according to the separation distance LS and the desired angular resolution δθ of the detector, for example δθ on the order of 2°. In particular, the dimension a of the at least one passage zone is such that, a = Z . tan δθ − L s Z p Z + Z p where Zp is the minimum distance separating the useful detection volume from at least one passage zone, along the optical axis O. This dimension a is therefore also a function of the distances Z and Zp, which determine the detector's clearance depth along its optical axis O. The dimension a can alternatively be determined based on the separation distance LVertices or the separation distance LBases. In this case, simply replace Ls with LVertices or LBases in the formula above.

[0051] Preferably, but optionally, the detector presents a field of view defined by an angle FOV = atan( L / 2z) where L is a lateral dimension of the retina taken in a plane parallel to a face of the retina facing the dark reticle if the retina is flat, Z being the distance separating the dark reticle from the retina, and the useful detection volume is contained within this field of view. The field of view has a vertex extending from at least one aperture and an axis of symmetry parallel to the optical axis. The useful detection volume of this detector can thus be significantly increased, and have, for example, a diameter of 100 µm to 2 mm. Furthermore, the entire useful detection volume can be projected onto the retina through at least one aperture. The detection sensitivity of the detector is improved.

[0052] This detector thus offers superior detection sensitivity and useful detection volume compared to existing miniaturized detectors, while maintaining a simple and inexpensive design, and a short fluidic response time.

[0053] Thus, the present invention proposes an effective solution for improving current detectors. It provides a miniaturized optical particle detector capable of distinguishing scattering patterns resulting from multiple and simultaneous scattering events. Preferably, this detector also allows for the individual analysis of each of these scattering patterns, so as to determine the individual optical (e.g., refractive index) and geometric (e.g., diameter) properties of the particles. Preferably, this detector also exhibits good detection sensitivity and / or a short fluidic response time. Preferably, this detector also allows for the analysis of a large detection volume (e.g., with a diameter of 100 µm to 2 mm).

[0054] The present invention also relates to a system comprising such a detector, and at least one primary source.

[0055] According to an optional embodiment, the at least one primary source comprises a first primary source emitting incident light rays having at least one first wavelength and a second primary source emitting incident light rays having at least one second wavelength different from the first wavelength, said first and second primary sources having first and second principal emission directions respectively configured to intersect within the useful detection volume. This system advantageously allows for the creation of polychromatic images of the scattering patterns.

[0056] The present invention further relates to a method for manufacturing such a particle detector, comprising at least the following steps: Provide an optically transparent block having a first face and a second face opposite the first face; deposit on the first face an opaque or reflective coating, for example a carbon or metallic layer; optionally, drill the transparent block in a direction substantially normal to the first and second faces, for example by laser etching, deep wet etching, or reactive ion etching (RIE), to create a through fluidic channel; form at least one aperture in the coating at the location of said at least one pattern, for example by etching, to create a dark reticle comprising said opaque or reflective coating and said at least one aperture. For example, form at least one pinhole or slit pattern on the coating of the first face, for example by lithography or deposition.Optionally, deposit an opaque layer on the surfaces of the block substantially normal to the first and second faces, for example by spraying paint. Assemble, for example by gluing, the block and a retina comprising a plurality of photodetectors, at the level of the second face of the block. BRIEF DESCRIPTION OF THE FIGURES

[0057] 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 This schematically illustrates in cross-section a detector and the scattering patterns of two particles formed on the retina of this detector according to the prior art. FIGURE 2A presents a simulation of an image formed on the retina of the detector of the prior art illustrated in the FIGURE 1, from the diffusion of a spherical particle 5 µm in diameter. The FIGURE 2B presents a simulation of an image formed on the retina of the detector of the prior art illustrated in the FIGURE 1 , from the simultaneous scattering of three spherical particles with diameters of 1 µm, 2 µm, and 5 µm respectively. The FIGURE 3 schematically illustrates in cross-section a detector according to an example of an embodiment of the invention and the scattering diagrams of two particles formed on the retina of this detector. FIGURE 4 schematically illustrates in cross-section a detector according to another embodiment of the present invention. FIGURE 5 schematically illustrates, in perspective view, a detector according to another embodiment of the present invention. FIGURES 6A to 6J schematically illustrate patterns of the passage zones of a detector's reticle according to different embodiments of the present invention. FIGURES 7A and 7Bschematically illustrate a projection of scattered rays onto a reticle of a detector according to an embodiment of the present invention. FIGURES 8A and 8B schematically illustrate a projection onto a retina of rays scattered through a passage zone of a detector according to an embodiment of the present invention. FIGURE 9 schematically illustrates, in perspective view, a detector according to another embodiment of the present invention. FIGURE 10 schematically illustrates, in perspective view, a detector according to another embodiment of the present invention. FIGURE 11 presents a simulation of an image formed on the retina of the detector illustrated in the FIGURE 9 , from the simultaneous scattering of three spherical particles with diameters of 1 µm, 2 µm, and 5 µm respectively. The FIGURE 12 illustrates a clear reticle according to an embodiment of the present invention. The figure 13Aillustrates the projection onto the retina of a scattering pattern from a scattering particle, through the clear reticle shown in the figure 12 . There figure 13B illustrates the projection onto the retina of two scattering diagrams from two scattering particles, through the clear reticle shown in the figure 12 . There figure 13C illustrates the projection onto the retina of three scattering diagrams from three scattering particles, through the clear reticle shown in the figure 12 . There FIGURE 14 illustrates a reticle according to an embodiment of the present invention. The FIGURE 15A schematically illustrates, in top view, a detector comprising a reticle and a fluidic channel passing through the reticle, according to an embodiment of the present invention. FIGURE 15Bschematically illustrates, in top view, a detector comprising a reticle and a fluidic channel passing through the reticle, according to another embodiment of the present invention. FIGURE 16 schematically illustrates, in perspective view, a detector comprising a reticle and a fluidic channel passing through the reticle, according to another embodiment of the present invention. FIGURE 17 schematically illustrates in cross-section a detector comprising a reticle and a fluidic channel passing through the reticle, according to another embodiment of the present invention. FIGURES 18A to 18G schematically illustrate steps in a manufacturing process for a detector according to an embodiment of the present invention. FIGURES 19A and 19B schematically illustrate steps in a manufacturing process for a detector according to another embodiment of the present invention. FIGURE 20Aschematically illustrates, in perspective view, a system comprising a detector according to one embodiment of the present invention and a primary source according to a first embodiment. FIGURE 20B schematically illustrates, in perspective view, a system comprising a detector according to one embodiment of the present invention and a primary source according to a second embodiment. FIGURE 21A schematically illustrates, in perspective view, a system comprising a detector and two primary sources according to an embodiment of the present invention. FIGURE 21B schematically illustrates in perspective view a system comprising a detector and two primary sources according to another embodiment of the present invention.

[0058] The drawings are provided as examples and are not intended to limit the scope of the invention. They are schematic representations of the principle intended to facilitate understanding of the invention and are not necessarily to scale with practical applications. In particular, the dimensions of the various structures (particles, reticulum, retina) are not representative of reality. DETAILED DESCRIPTION OF THE INVENTION

[0059] Before beginning a detailed review of embodiments of the invention, it is recalled that, optionally, the invention includes at least one of the following optional features which may be used in combination or alternatively.

[0060] According to an optional embodiment, the second figure is offset on the retina relative to the first figure. According to an optional embodiment, the smallest distance Ls corresponding to this offset between these two figures is greater than or equal to 2*Lpix when the first and second parts passing through at least one optical passage zone together define an angle θij whose value is at least equal to an angular resolution δθ of the detector, Lpix being the spacing between two adjacent photodetectors of the retina.

[0061] According to one embodiment, the distance Ls between the figures projected onto the retina is non-zero. The retinal photodetectors 30 capture light rays scattered by only one of the particles 10₁, 10₂. In other words, a single photodetector does not capture rays scattered by more than one particle. Thus, photodetector blinding or overlap of the diagrams on one of the photodetectors will be avoided.

[0062] According to an optional embodiment, dimension a is configured such that a = Z . tan δθ − L s Z p Z + Z p where Zp is the minimum distance separating the useful detection volume from at least one of said optical passage and blocking zones.

[0063] According to an optional embodiment, the reticle and the retina are configured, in particular the minimum distance Z and the dimension a, so as to generate on the retina a first diffusion diagram S1 formed by the first diffused part, and a second diffusion diagram S2 formed by the second diffused part.

[0064] According to an example implementation, the first and second diffusion diagrams S1, S2 are distinct. They are offset.

[0065] According to one embodiment, said first and second scatter diagrams S1, S2 are distinct when the first and second parts passing through at least one optical passage zone together define an angle θij whose value is at least equal to an angular resolution δθ of the detector, Lpix being the step between two adjacent photodetectors of the retina.

[0066] According to an example embodiment, the first and second diffusion diagrams S1, S2 each form at least one bright peak S1pic, S2pic. These bright peaks S1pic, S2pic are distinct. They are offset.

[0067] According to one embodiment, the first and second scattering patterns S1, S2 each form at least one luminous peak S1pic, S2pic corresponding to at least one optical passage zone and each having a basis BS1, BS2. The bases BS1, BS2 of each scattering pattern S1, S2 are offset on the retina by a separation distance LBases ≥ 2*Lpix when the first and second parts passing through at least one optical passage zone together define an angle θij whose value is at least equal to an angular resolution δθ of the detector, Lpix being the spacing between two adjacent photodetectors of the retina. Preferably, LBases ≥ 5*Lpix. Preferably, LBases ≥ 10*Lpix.Preferably, the peak S1, S2 of each diagram includes at least one vertex SS1, SS2, with the highest point of the base BS1, BS2 located at a height of peak S1, S2 equal to 10% of the height HS1, HS2 of the vertex SS1, SS2, and preferably located at a height of peak S1, S2 equal to 5% of the height of the vertex SS1, SS2. The distance L Bases is measured at the highest point of the base BS1, BS2. Thus, it is possible for two adjacent peaks to overlap in areas located below the bases (partial overlap of the spots). These areas exhibit low light intensities. However, at the bases, the diagrams do not overlap.

[0068] According to one embodiment, the first and second scattering patterns S1, S2 each form at least one luminous peak S1pic, S2pic corresponding to at least one optical passage zone and having a vertex SS1, SS2. The vertices SS1, SS2 of each scattering pattern S1, S2 are offset on the retina by a separation distance LVertices ≥ 10*Lpix when the first and second parts passing through at least one optical passage zone together define an angle θij whose value is at least equal to an angular resolution δθ of the detector, Lpix being the spacing between two adjacent photodetectors of the retina. Preferably, LVertices ≥ 20*Lpix.

[0069] If there are a plurality of particles in the useful volume, the definitions above apply to each pair of particles belonging to that plurality. Indeed, if there are a plurality of particles, there are a plurality of spots and a plurality of diffusion patterns.

[0070] According to one embodiment, the first and second shadows B1, B2 formed on the retina by at least one optical blocking zone are distinct. They are offset.

[0071] According to one embodiment, the first and second shadows B1, B2 are partially superimposed on the retina.

[0072] In one example, the optical passage zone forms at least one opening bounded by the optical blocking zone, with the first and second figures each representing a spot (or illuminated spot). The optical passage zone is thus surrounded, preferably entirely, by the optical blocking zone. The boundary of the optical passage zone is defined, or is constituted, preferably entirely, by the optical blocking zone.

[0073] In one example, the optical passage zone forms at least one opening surrounding, preferably entirely, the optical blocking zone, with the first and second figures each representing a shadow. The optical blocking zone is thus surrounded, preferably entirely, by the optical passage zone. The boundary of the optical blocking zone is defined, or is constituted, preferably entirely, by the optical passage zone.

[0074] As an example, at least one optical passage zone comprises at least one pattern of either a pinhole or a slit. The pinhole pattern projects a spot onto the retina for each of the scattering particles. This spot forms the scattering diagram S(θj) of the scattering particle in question and corresponds only to the light rays scattered by this particle passing through the pinhole and forming approximately a scattering angle θj with the optical axis. This allows the scattering diagrams of different particles to be limited to easily discernible spots on the retina. The slit pattern projects a line onto the retina for each of the scattering particles. This line forms the scattering diagram S(θi...θj) of the scattering particle in question and corresponds only to the light rays scattered by this particle passing through the slit and forming approximately a scattering angle within the range of angles [θi...θ j ] relative to the optical axis. This allows us to obtain a scattering diagram that provides more information about the scattering particle.

[0075] In one example, at least one optical passage zone comprises at least one pinhole pattern and at least one slit pattern, these patterns being partially overlapped. This facilitates the reading of the pattern projected onto the retina, for example, by using a pattern recognition algorithm. The combination of the circular shape of the pinhole and the straight or curved shape of the slit is thus easily discernible on the retina.

[0076] According to one example, at least one pinhole motif has a diameter approximately twice the width of at least one slit motif, said width being taken along a direction normal to the tangent to the slit at the point considered.

[0077] According to one example, at least one slit pattern is straight or curved.

[0078] As an example, at least one optical passage zone comprises a plurality of pinhole patterns. These pinhole patterns can be connected, for example by one or more slits, to form an optical passage zone. These pinhole patterns can also be separated from each other to form several apertures or optical passage zones. A plurality of pinhole patterns allows a plurality of corresponding spots to be projected onto the retina for each of the scattering particles. According to the principle of reversibility of light, it is thus possible to estimate the position of a given scattering particle from the positions of the spots on the retina and the angles these spots form with respect to the axes passing through the corresponding pinholes and parallel to the optical axis. For example, two spots obtained through a double pinhole allow two "return" rays to be traced that intersect at the estimated position of the scattering particle.In the case of an optical passage zone comprising N pinholes (for example N between 2 and 10), it is possible to cross 2 out of N rays. N 2 and therefore to estimate a position of the diffusing particle averaged from N 2 values.

[0079] The use of N pinholes allows for a precise estimation of the particle's position. This yields a scattering diagram sampled over N scattering angles. This enables, for example, an improved comparative theory / measurement analysis of the scattering diagram. The analysis of the particle's nature is thus enhanced.

[0080] In one example, the optical passage zone includes at least one curved slit pattern with a negative curvature directed towards a center of the reticle. Such a pattern compensates for a positive curvature induced by a medium of thickness Z located between the reticle and the retina, which has a refractive index higher than that of the particle. This medium distorts the scattering pattern projected onto the retina through the slit.

[0081] A curvature opposite to this distortion allows the diffusion pattern to be "straightened," and makes it possible, for example, to obtain a diffusion pattern in the form of a line on the retina. This makes the diffusion pattern easier to read.

[0082] According to one example, the optical passage area includes at least one curved slit pattern with a positive curvature directed towards a periphery of the reticle.

[0083] In one example, the slit pattern forms a closed outline.

[0084] In one example, the closed contour is a ring. This facilitates the observation of Mie alternations, which appear as lobes in the diffusion diagram, according to Mie theory.

[0085] In one example, the closed contour is an ellipse. This allows for the optimization of the observation of Mie alternations, in the case where the incident rays illuminating a given particle are substantially parallel to the plane in which the reticle extends.

[0086] As an example, at least one optical passage zone comprises a plurality of optical passage zones, each presenting at least one pattern chosen from a pinhole and a slit. This facilitates the reading of the pattern projected onto the retina and improves the recognition of the scattering pattern. It also allows for a richer scattering pattern, that is, one containing more information about the scattering particle. Some or all of these apertures or optical passage zones may be distinct, i.e., separated from one another, or conversely, overlap, intersect, or touch.

[0087] According to an example, at least one optical passage zone has a characteristic size a such that a ≥ 10.Lpix.(Z / (Z+Zp), where Zp is the minimum distance separating the useful detection volume from at least one of said optical passage and blocking zones and Lpix is ​​the step between two adjacent photodetectors.

[0088] As an example, at least one optical passage zone has a passage area Sa less than 50% of the total reticle area, preferably less than 10% of the total reticle area. This ensures good readability of the scattering pattern. It also increases the likelihood of avoiding overlap of the scattering patterns of several particles present simultaneously in the detection volume.

[0089] According to one example, the angular resolution δθ of the detector is on the order of 2°.

[0090] For example, the minimum distance Z p separating the useful detection volume from at least one of said optical passage and blocking zones is such that 0,2.2 ≤ Z p ≤ 2. Z.

[0091] As an example, all photodetectors have the same dimensions. In particular, they all have the same width.

[0092] In one example, the detector further includes at least one fluidic channel for guiding particles to the useful detection volume, with the channel passing through the reticle at an orifice formed in the reticle. This improves the detector's detection sensitivity while maintaining a compact and small footprint.

[0093] In one example, at least one optical passage zone comprises a plurality of optical passage zones distributed around the orifice. Such a distribution allows for the differentiation of analysis zones, for example, a front scattering zone that filters and receives scattered rays propagating in the direction of the incident rays, and a backscattering zone that filters and receives backscattered rays propagating in the opposite direction to the incident rays.

[0094] According to one example, the plurality of optical passage zones comprises at least a first optical passage zone and at least a second optical passage zone located on either side of the channel orifice. This first optical passage zone has a smaller characteristic dimension, preferably at least half the size of a characteristic dimension of the second optical passage zone. Such a first optical passage zone is, for example, adapted to the front scattering area of ​​the detector, which is brighter. The use of fine, high-resolution patterns for this first optical passage zone, in conjunction with the front scattering area, allows for the formation of a proportionally fine and high-resolution first scattering pattern. Such a second optical passage zone is, for example, adapted to the back scattering area of ​​the detector, which is less bright.The use of large patterns for this second optical passage zone associated with the backscattering zone improves the detection sensitivity of backscattered rays, in order to obtain a second backscattering diagram.

[0095] According to one example, the plurality of photodetectors of the retina includes at least a first zone of photodetectors adapted to receive first and second parts scattered through at least a first optical passage zone, and at least a second zone of photodetectors adapted to receive first and second parts scattered through at least a second optical passage zone, the first zone of photodetectors comprising photodetectors different from those of the second zone of photodetectors.

[0096] For example, the first photodetector zone contains smaller and more numerous photodetectors than the second photodetector zone. This improves the retinal resolution in the first zone. Alternatively, the first photodetector zone may have a higher photodetector density than the second photodetector zone.

[0097] For example, the second zone of photodetectors contains more sensitive photodetectors than those in the first zone. For instance, the photodetectors in the second zone are larger and / or have a higher gain than those in the first zone. This improves the retina's sensitivity in the second zone.

[0098] In one example, the detector further includes opaque walls connecting the reticle and the retina, forming at least one closed contour to define a dark chamber in which the first and second scattered parts propagate. This dark chamber is optically open only at at least one optical passage zone of the reticle. This dark chamber limits the illumination of the retina. This reduces the probability that other rays, for example from stray scatter, will penetrate the dark chamber and disrupt the image formed on the retina.

[0099] As an example, the internal surfaces of the walls of this dark room are absorbent.

[0100] In one example, the detector further comprises at least one first chromatic filter configured to filter the first and second scattered parts exhibiting a first wavelength, and at least one second chromatic filter configured to filter the first and second scattered parts exhibiting a second wavelength different from the first. The first and second chromatic filters can, for example, be arranged respectively at the first and second optical passage zones. Alternatively, or in combination, the chromatic filters can be arranged respectively at the first and second patterns of the same optical passage zone. Thus, the pattern specifically filters a color of the illumination, and the scattering pattern projected onto the retina can be formed by different chromatic parts.Alternatively, the first and second chromatic filters can, for example, be placed on the first and second photodetector zones, respectively. In another example, the detector comprises three chromatic filters (typically red, green, and blue) deposited on three photodetector zones of the retina. This allows for the acquisition of three images corresponding to the diffusion patterns of the three colors.

[0101] The optical detector does not include a lens between the reticle and the retina. Therefore, and advantageously, no converging lens is required for the detector. The absence of such lenses improves the detector's compactness. This also improves the detector's robustness and / or reliability.

[0102] According to one example, in the system according to the invention, the first and second principal emission directions of the first and second primary sources are non-collinear and form an angle α between them.

[0103] According to another example, in the system according to the invention, the first and second principal emission directions of the first and second primary sources are collinear and the first and second incident light rays propagate in opposite directions.

[0104] In one example, the system includes a third source emitting third incident light rays having at least one third wavelength different from the first and second wavelengths, and the third primary source has a third principal emission direction configured to intersect the first and second principal emission directions within the useful detection volume. The first, second, and third wavelengths are preferably taken from red, green, blue, and near-infrared, and the detector includes three chromatic filters filtering three colors preferably taken from red, green, blue, and near-infrared.

[0105] 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.

[0106] The present invention applies to any type of particles carried by a fluid, whether liquid and / or gaseous.

[0107] The fluid present or flowing within the useful detection volume 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 fluid quality analysis system such as for air, and a pollution alarm system.

[0108] Alternatively, the fluid can be a liquid such as water. This is the case for detectors integrated into microbiological species detection systems.

[0109] The present invention aims in particular to simultaneously produce scatter diagrams of several particles within a detector fabricated using conventional microfabrication technologies. It is understood that this detector can, if necessary, produce a scatter diagram of a single particle.

[0110] 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 studied.

[0111] The term particle refers specifically to a solid, liquid, or wet solid object suspended in a fluid such as air, and whose size is microscopic. 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 greater than 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 cavity or channel through which the particles circulate.

[0112] The "size" or "diameter" of a particle refers to the maximum distance between two points on the particle. Typically, a particle is considered to be an object with spherical geometry, so its size corresponds to the diameter of the sphere.

[0113] In what follows, the term "absorption" or its equivalents refers to the phenomenon by which the energy of an electromagnetic wave is transformed into another form of energy, for example, by heat dissipation. In this description, a material is considered absorbing if it absorbs at least 50% of a light radiation, preferably at least 75%, and advantageously at least 90%. It can be characterized by an absorption factor between 0 and 1.

[0114] In what follows, the term "diffusion" or its equivalents refers to the phenomenon by which a propagation medium produces a distribution, in many directions, of the energy of an electromagnetic wave, light for example.

[0115] 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. It can be characterized by a reflection factor between 0 and 1.

[0116] The detector according to the invention comprises a "reticle." This reticle refers to a surface comprising at least one optical passage zone, preferably transparent, and at least one optical blocking zone, preferably opaque. In the following description, the optical passage zone of the reticle is also referred to as the "transparent surface," "optical aperture," or "aperture," for the sake of brevity. These terms are equivalent and designate an interface, surface, or volume through which light rays can pass. The optical aperture may be a physical opening formed by air or a vacuum, or filled with a transparent material. In the following, the optical blocking zone of the reticle is referred to as the "opaque surface." These terms are equivalent and designate an interface, surface, or volume through which light rays are blocked.

[0117] A surface is said to be "opaque" when it is not penetrated by light radiation of a given wavelength, or when it is penetrated by less than 10%, and preferably less than 5%, of that light radiation. This radiation is, for example, absorbed by the opaque surface. Alternatively, this radiation can be reflected specularly or scattered by the opaque surface. These three phenomena are not mutually exclusive.

[0118] The opaque surface can be formed by depositing a layer of a reflective material, such as gold or silicon-aluminum (AISi). Alternatively, the opaque surface can be formed by depositing a layer of an absorbent material, such as black resin or colloidal graphite. It can also be formed by applying an adhesive film (black or reflective) cut to create the opening.

[0119] The space of thickness Z between the dark reticle and the detector is preferably transparent. This space is, for example, formed of a vacuum or air. Alternatively, it can comprise or be made of a transparent material, for example, glass or a transparent polymer.

[0120] A material that is "transparent to a given wavelength" or simply "transparent" is defined as a material that allows at least 90% of the light intensity of light with that wavelength to pass through.

[0121] The transparent optical aperture can be formed by a pinhole or a slit. A pinhole is a hole of very small diameter and very thin thickness. A very small diameter is, for example, between 5 µm and 500 µm. A very thin thickness is, for example, between 100 nm and 100 µm. A slit is characterized by its width and length, and possibly by its curvature. The width is, for example, between 5 µm and 500 µm. The length is, for example, between 500 µm and 2 mm.

[0122] In this application, the diameter, width, and length are measured along directions transverse to the optical axis O, in the plane of the dark reticle. Thus, these transverse directions are measured in planes substantially parallel to the surface of the retina facing the dark reticle. The diameter or width corresponds to dimension a of the optical aperture. The thickness or depth is measured along the optical axis O.

[0123] The retina typically takes the form of a matrix of photodetectors constituting pixels of the detector.

[0124] The "useful volume," or "detection volume," is the intersection between the illumination beam(s) and the volume of probable particle presence that the detector can detect. In other words, it is the volume defined by the intersection of the illumination beam, the particle beam, and the detector's field of view. This is the volume used for detection.

[0125] In this application, the beam is specifically configured to illuminate particles off-axis O. For example, the beam is configured to illuminate particles off-axis O, such that the useful detection volume has a lateral extension of at least approximately 50 µm, or even at least 100 µm, relative to the detector's optical axis. The beam can thus typically have a beam size ranging from a few tens of µm to a few hundred µm.

[0126] The field of view is the solid angle for which the detector is sensitive to electromagnetic radiation.

[0127] In the context of the present invention, a light diagram expresses or illustrates the spatial distribution of a parameter that is a function of the light intensity received by the retinal photodetectors. Thus, a light diagram can be a representation of such a parameter as a function of its position on an axis or on a plane, or more generally on a flat or curved surface bearing the photodetectors. The parameter expressed can, for example, be the light intensity or be proportional to the light intensity.

[0128] For each scattering particle, the scattering pattern received by the photodetectors is typically derived from the convolution product of the scattering pattern of the particle by the figure (spot or shadow) projected onto the retina through the reticle.

[0129] A reticle is considered a dark reticle when the optical passage area forms at least one aperture delimited by the optical blocking area. In this case, the ratio of opaque to transparent surfaces is greater than 1, preferably much greater than 1. The opaque surface(s) of the reticle occupy a majority of its total surface area. The reticle is therefore "dark" and includes one or more optical apertures.

[0130] A reticle is considered "clear" when the optical passage area forms at least one opening surrounding the optical blocking area. In this case, the ratio of transparent to opaque surfaces is greater than 1, preferably much greater than 1. The transparent surface(s) of the reticle occupy a majority of its total area. The reticle is therefore "clear" and includes one or more optical blocking areas.

[0131] In the case of a dark reticle, the periphery of the figure (spot) surrounds the first set of photodetectors. The first set of photodetectors is circumscribed within the figure.

[0132] In the case of a bright reticle, the periphery of the figure (shadow) is surrounded by the first set of photodetectors. Thus, the arrangement of the first set of photodetectors is the negative of the figure (shadow).

[0133] The beam(s) of light are emitted by one or more corresponding primary sources. These primary sources can be polychromatic or monochromatic. The light emitted by these sources preferably belongs to the visible spectrum extending to the near-ultraviolet and near-infrared, that is, to a wavelength range between 300 and 1000 nm. The "wavelength" of the source or the "first wavelength" of the first source refers to wavelengths of interest.

[0134] In the case of a polychromatic source, this wavelength of interest can be the most intense wavelength emitted by the source. It can also refer to a range of wavelengths on the order of tens of nanometers, for example on the order of 100 nm, preferably on the order of 50 nm.

[0135] In the case of a monochromatic or quasi-monochromatic source, the wavelength of interest is the single wavelength emitted by that source or the wavelength primarily emitted by that source.

[0136] In the following text, this wavelength of interest is also referred to as "color" for ease of reading. This definition of color does not directly correspond to the colors of the rainbow (the visible electromagnetic spectrum). It specifically includes "colors" from the near-infrared and near-UV regions, and / or excludes colors resulting from the mixing of disjoint colors of the electromagnetic spectrum, such as purples.

[0137] A structural element is defined as a layer "based" on a material A, a layer comprising only that material A, or that material A and possibly other materials, for example, dopant elements or alloying elements. Thus, if a transparent block is described as "polymer-based," this means that it can be formed solely of polymers, or of polymers and possibly other materials, for example, an inorganic oxide.

[0138] 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 application of a coating to a structural element does not necessarily mean that they are directly in contact with each other, but rather that the coating at least partially covers the structural element, either by being directly in contact with it or by being separated from it by at least one other layer or element.

[0139] 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 without limitation. In particular, the number of openings, the different opening patterns, and / or the different channel shapes illustrated in the figures may be combined to form another embodiment that is not necessarily illustrated or described. Such an embodiment is obviously not excluded from the invention.

[0140] The terms "approximately," "about," and "on the order of" mean "within 10%" or, when referring to angular orientation, "within 10°" and preferably "within 5°." Thus, a direction approximately normal to a plane means a direction at an angle of 90±10° to the plane.

[0141] To determine the detector's optical properties, measurements of opacity (absorption and / or reflection spectra), transparency (transmission spectrum), and field of view (solid angle of detection) can be performed. Spectrometry and integrating sphere techniques, for example, can be used to carry out these measurements.

[0142] Simulation methods, for example ray tracing calculations using the Monte Carlo method, can also be used to determine the scattering pattern(s) obtained through a detector. The effective separation of scattering patterns from several particles detected simultaneously can be an indicator of the implementation of a detector as described in the present invention.

[0143] A first simplified example of a detector according to the invention will now be described with reference to the figure 3 , to understand how it works.

[0144] For the sake of clarity, the case of an opening in the reticle resulting in T1 and T2 spots (dark reticle) will be described in more detail. The case of a dark area in the reticle (light reticle) resulting in B1 and B2 shadows, which can be considered the negative of the first case, can be easily deduced from this first case described below. This case with a light reticle will be described in detail, for example with reference to the figures 12 to 13C .

[0145] As illustrated in the diagram of the figure 3The detector 1 is designed to detect at least two particles 10₁, 10₂ within a useful volume 100. This useful volume 100 is a region of space that receives illumination and through which the particles 10₁, 10₂ circulate. The possibilities and conditions for illuminating this useful volume 100 are described in the "Illumination Beam" section later in this description. The region of space may be open or delimited by material elements. In particular, it may extend within a particle transport channel or towards the mouth of such a channel, for example, at an outlet of this channel. Some embodiments of the detector including such a channel are described in the "Transit Channel" section later in this description.

[0146] When the particles 101, 102 are in the useful volume 100, they receive incident light rays emitted by a primary source (not shown), then in turn emit scattered light rays kd1, kd2. These two particles 101, 102 then form secondary sources 21, 22 which illuminate the detector 1.

[0147] The term primary source is not limited to a specific type of source. This primary source can be a light source that itself generates light within the useful volume 100. It can also be a device comprising a light-generating source and associated with an optical device for guiding the light into the useful volume 100 and / or a beam-forming device comprising light rays passing through the useful volume 100.

[0148] Detector 1 is configured to filter and receive part of the scattered light rays kd 1, kd 2. It advantageously includes a reticle 30 to filter the scattered light rays kd 1, k d2, and a retina 20 to receive only the rays kd 1, k d2 filtered by the reticle 30.

[0149] The reticle 30 comprises an opaque surface 300 and at least one optical aperture 301. In the illustrated example, the optical aperture 301 has a surface area much smaller than the optical blocking zone. The reticle is of the dark reticle type. It is preferably flat and parallel to the retina 20. The detector embodiments described and illustrated below are based on such a flat, dark reticle parallel to the retina, so as to facilitate understanding of the invention. The reticle and / or the retina may alternatively have a curvature. In this case, a direction perpendicular to the retina means a direction perpendicular to the tangent to the retina at the point considered, for example, at the intersection between the retina and the optical axis. The reticle and the retina may not be parallel to each other.For example, a curved retina and a curved reticulum forming concentric spheres whose center is positioned at the level of the useful volume can be implemented within a detector according to the invention. In this case, the examples of detector embodiment and dimensioning can be adapted. mutatis mutandis.

[0150] The aperture 301 is configured to allow passage of a portion 31 of the scattered rays k d1 and a portion 32 of the scattered rays kd 2. The characteristics of this aperture 301, in particular its shape and dimensions, are described in the corresponding sections "shape of the aperture" and "dimensions of the aperture".

[0151] The scattered parts 31, 32 form angles θj, θi respectively with the optical axis O of the detector. The angular distance between the particles 101, 102, i.e., the angle formed by the scattered parts 31, 32 entering the aperture 301, is denoted θij = θj + θi. θ, θj, and θi are referenced in figure 3 .

[0152] Parts 31 and 32 are projected onto the retina 20, forming the scattering patterns S1(θj) and S2(θi), respectively, also denoted S1 and S2 for brevity. Their respective positions on the retina 20 depend on the angles θj and θi. Preferably, these scattering patterns S1(θj) and S2(θi) each exhibit a luminous peak, referenced respectively as S1pic and S2pic in this example. LBases is the distance between the bases BS1 and BS2 of these peaks S1pic and S2pic, and LVertices is the distance between the vertices PS1pic and PS2pic of these peaks S1pic and S2pic. The distance between the spots T1 and T2 formed by the projection of the first and second scattered parts onto the retina 20 is denoted Ls.

[0153] The detector, in particular the minimum dimension of the aperture 301 as well as the minimum distance Z taken along the optical axis O between the reticle 30 and the retina 20 is configured so as to be able to distinguish the spots T1, T2 and the diffusion diagrams S 1 (θ j ), S 2 (θ i ).

[0154] Thus, when the particles are sufficiently far apart (typically when they together define an angle θij whose value is at least equal to the angular resolution δθ of the detector), the distances Ls, LBases, and LVertices are non-zero. Furthermore, the Lpix step size of the retinal photodetectors20 is small enough that these distances Ls, LBases, and LVertices allow the photodetectors to separately identify the T1 and T2 spots and the scattering patterns S1(θj), S2(θi) when θij ≥ δθ.

[0155] This angular resolution δθ corresponds to the smallest angular separation θij = θj + θi between the two scattering particles 101, 102 that the detector is capable of detecting. If θij ≥ δθ, then the distances Ls, LBases, and LVertices are non-zero, and detector 1 is capable of discriminating between the two spots T1, T2 or the two peaks S1pic and S2pic. Detector 1 will identify the presence of each of the two particles 101, 102.

[0156] For example, for an aperture 301 separated from the retina 20 by a distance Z, the minimum separation distance L Vertices is equal to: The Summits = Z (tan θ i + tan θ j ). The minimum separation distance Lvertex allowing the distinction on the retina of the diffusion diagrams S1(θj), S2(θi) corresponds to the linear resolution of detector 1.

[0157] The sizing of detector 1 according to the desired resolution is described in more detail in the section "Detector sizing". A manufacturing process for such detector 1 is also described in the corresponding section "Manufacturing process".

[0158] According to a possibility illustrated in the figure 4 The reticle 30 of detector 1 comprises several apertures 301, 302. This allows for an enriched scattering diagram for each of the scattering particles. For clarity, only one particle 101 is shown on the figure 4This particle 101 scatters a first part 311 of light rays through the first aperture 301, and a second part 312 of light rays through the second aperture 302. These first and second parts 311, 312 form a scattering diagram S1(θ1, θ2). The scattering diagram S1(θ1, θ2) can include several discrete portions, for example the spots S1(θ1) and S1(θ2) seen through the apertures 301, 302 respectively at angles θ1, θ2.

[0159] This enriched scattering diagram S1(θ1, θ2) makes it possible, in particular, to determine the position of particle 10 within the useful detection volume. This position corresponds, according to the principle of reversibility of light, to the intersection of the light rays forming parts 311, 312.

[0160] In this case with several apertures 301, 302, the distances Ls, L Bases and L Vertes correspond to the distances between the spots, bases and vertices of the scattering diagrams formed by the rays scattered by two particles through only one of the apertures 301, 302. Shape of the opening and / or dark surface

[0161] For clarity, different shapes of a single opening are described in this section. It is understood that these shapes can be applied to multiple openings and / or darkened surfaces. Furthermore, multiple openings and / or darkened surfaces can combine different shapes depending on the various advantages associated with each shape.

[0162] A shape can be transparent (as in the case of openings) or opaque (as in the case of dark surfaces). Thus, a pinhole camera can be a transparent disc or a hole (as in the case of openings) or an opaque disc (as in the case of dark surfaces). Each shape or pattern can therefore be adapted. mutatis mutandisin the case under consideration.

[0163] The simplified diagrams illustrated by the figures 3 and 4 are based on simple pinhole-shaped apertures (301, 302). The pinhole pattern projects a T1, T2 spot onto the retina for each scattering particle. The corresponding scattering diagram thus includes a peak-shaped portion (S1 peak, S2 peak) for each particle, making it easier to interpret the scattering diagram.

[0164] There figure 5 illustrates an aperture 301 in the form of a slit. This slit pattern allows for an enriched scattering diagram for each scattering particle. For clarity, only one particle 10 1 is shown on the figure 5This particle 101 scatters a plurality of light rays through the first aperture 301. The light rays received by the retina 20 are contained between parts 311 and 312 passing through each end of the slit. These light rays contained between parts 311, 312 form a scattering pattern S1 (θ1 < θ < θ2). This scattering pattern S1 (θ1 < θ < θ2) preferably includes a continuous portion, formed by a continuum of spots S1(θ) seen through the aperture 301 under a continuum of scattering angles θ between θ1 and θ2.

[0165] The slit is not necessarily straight, it can be curved.

[0166] THE figures 6A to 6JThese illustrate different possible shapes for a reticle aperture. These shapes are typically combinations of slits and pinholes, enriching and facilitating the reading of the corresponding scatter diagrams. All the shapes below can be combined and / or repeated several times to form one or more apertures and / or dark areas of the same detector. The detector according to the invention is not limited to the examples of shapes mentioned below. Other shapes of apertures and / or dark areas are conceivable.

[0167] THE Figures 6A and 6B illustrate a shape resulting from the combination of a rectilinear slit pattern 312 and a pinhole pattern 311, located for example at the center of the slit pattern 312. The slit can be oriented along the direction of the continuum of diffusion angles that one wishes to detect and analyze, for example a horizontal direction ( figure 6A ) or a vertical direction ( figure 6B ).

[0168] There figure 6C illustrates a form resulting from the combination of a straight slit pattern 312 and several pinhole patterns 311, for example two pinholes located at the ends of the slit pattern 312.

[0169] There figure 6D illustrates a form resulting from the combination of the motifs of the Figures 6A and 6B This shape allows for the detection and analysis of diffusion angle continua in orthogonal directions, for example, the horizontal and vertical directions. The shape of the figure 6D comprises two straight slits 312 which intersect, preferably at their midpoint, and preferably at a right angle. A pinhole 311 is formed at the intersection of the two slits 312.

[0170] THE figures 6E and 6F illustrate forms resulting from the combination of several rectilinear slit patterns 312 and several pinhole patterns 311. The shape of the figure 6E adds to that of the figure 6Da pinhole camera at each end of the slits 311. The shape of the figure 6F It comprises several straight slits placed side by side at their ends, each with a pinhole at its end. The contour formed by this succession of slits and pinholes can be open, forming, for example, three segments orthogonal to each other. Alternatively, this contour can be closed.

[0171] There figure 6GThis illustrates a shape resulting from the combination of several curvilinear 311-c slit patterns and several pinhole 311 patterns. The curvilinear 311-c slit patterns here exhibit a so-called negative curvature, that is, one extending towards the center of the reticle or aperture. Such a negative curvature compensates for a distortion induced by the medium between the reticle 30 and the retina 20, in cases where this medium has a refractive index n+ greater than that of the scattering particle. This shape allows, for example, the projection onto the retina 20, in the presence of this medium with a refractive index n+, of a pattern similar to that projected by the shape illustrated in figure 6F , in the absence of this medium with a refractive index of n + . The geometry of this shape therefore has a "rectifying" effect on the projection of the diffusion diagram onto the retina.

[0172] There figure 6HThis illustrates a shape resulting from the combination of several straight slit patterns 312 and several pinhole patterns 311. In this example, the directions of the diffusion angle continua to be detected are not orthogonal. The slits are straight and are juxtaposed to form a closed contour. A pinhole is formed at each juxtaposition of two adjacent slits. In this example, the closed contour is a triangle, equilateral in this non-limiting example.

[0173] In general, the shapes illustrated by the figures 6C, 6E, 6F, 6G, 6H These techniques facilitate the reading of the diffusion pattern projected onto the retina. In particular, diffusion patterns comprising a plurality of circular spots, such as those obtained through a plurality of pinholes, are easily identifiable using pattern recognition algorithms.

[0174] THE figures 6I and 6Jillustrate shapes comprising curvilinear 311+c slit patterns exhibiting a so-called positive curvature, that is, extending towards the periphery of the reticle or aperture. Such a shape may have a closed contour, such as a ring ( figure 6I ) or an ellipse ( figure 6J ) for example. A ring aperture shape allows, in particular, the observation of Mie alternations, which appear as lobes in the angular scattering diagram, according to Mie theory. An elliptical aperture shape optimizes the observation of Mie alternations, especially when the incident rays illuminating the scattering particle are substantially parallel to the plane in which the reticle extends, as illustrated in the figure 7A .

[0175] In this case, the rays 10₁(θ₁), 10₁(θ₂), 10₁(θ₃) scattered respectively at angles θ₁, θ₂, θ₃ form coaxial cones around the direction of the incident rays ki. These so-called "iso-θ" cones are projected onto the reticle 30 respectively along hyperbolas P₁(θ₁), P₂(θ₂), P₃(θ₃) (on the figure 7A (The illustrated hyperbolas do not correspond exactly to the projected rays, for reasons of clarity). These hyperbolas P1(θ1), P2(θ2), P3(θ3) "iso-θ" are the locus of the Mie lobes. A slit following a trajectory T orthogonal to the "iso-θ" hyperbolas is therefore optimized for observing the alternations of these Mie lobes. In the case of the hyperbolas P1(θ1), P2(θ2), P3(θ3), this trajectory T is an ellipse ( figure 7B ).

[0176] In general, the aperture and / or dark surface may exhibit any combination of pinhole, straight slit, negative curvilinear slit, and positive curvilinear slit patterns. Sizing of the opening and / or the dark surface

[0177] The characteristic size or dimension a of the opening and / or dark surface is a linear dimension: it is for example the diameter of a circular hole or the width of a slit.

[0178] The aperture is preferably large enough to obtain good resolution of the projected diffusion diagrams. As illustrated in the figure 8AFor a particle 10, located at a distance Zp from the reticle 30 of the detector, the scattering pattern of this particle or the spot projected onto the retina 20 through an aperture 301 of dimension a has a dimension La. This dimension La depends on the dimension a, the distance Z separating the reticle 30 from the retina 20, and the distance Zp separating the particle 10 from the reticle 30. In particular, La = a*(Z+Zp) / Zp.

[0179] Z and Zp are measured along directions parallel to the optical axis (O). Z and Zp are measured along directions perpendicular to a plane in which the retina 20 extends mainly, or more precisely, a face of the retina 20 turned towards the reticle 30.

[0180] For given Z and Zp, the dimension a is chosen such that La > Lpix, where Lpix is ​​the step size between two adjacent photodetectors, i.e., one pixel step of the retina. Preferably, the dimension a is chosen such that La is between 1 and 20 pixel steps (1 Lpix < La < 20 Lpix), and preferably such that La is approximately equal to 10 pixel steps (La ≈ 10 Lpix). The detector thus exhibits good linear resolution.

[0181] The aperture is preferably also small enough to avoid overlapping of the projected diffusion patterns. As illustrated in the figure 8BFor two particles 10⁻¹ and 10⁻² exhibiting an angular separation θ₁ᵢ (with θ₁ᵢ ≥ δθ, δθ being the detector resolution) and located at a distance Zp from the reticle 30, the spots T₁ and T₂ projected onto the retina 20 through the aperture 301 of dimension a are separated by a distance Ls. The dimension a is chosen such that Ls is preferably greater than or equal to 2*Lpix, preferably Ls ≥ 5*Lpix, and preferably Ls ≥ 10*Lpix. The spots T₁ and T₂ are thus clearly distinct on the retina 20. It is then possible to separately identify these spots and the corresponding scattering patterns. Counting the 10⁻¹ and 10⁻² particles and analyzing them is therefore straightforward.

[0182] The sizing of the aperture therefore depends on the distances Z and Zp, the angular resolution δθ of detector 1 and the separation distance Ls: a = Z . tan δθ − L s Z p Z + Z p

[0183] In the case of an aperture with a combination of slit and pinhole patterns, the slit width is preferably half the pinhole diameter. In this case, dimension 'a' corresponds to the slit width. Generally, dimension 'a' is the smaller of the pinhole diameter and the slit width.

[0184] In the case of multiple apertures, the total area of ​​these apertures, measured in the plane of the dark reticle, is preferably less than 50% of the dark reticle area, and preferably less than 10% of the dark reticle area. This limits the overlapping areas of the diffusion patterns projected through these apertures on the retina. The readability of the diffusion patterns is improved.

[0185] This ability of detector 1 to distinctly identify the scattering pattern S1, S2 of each particle 101, 102 can also be characterized with respect to the distance L Bases expressing the offset between the bases BS1, BS2 of each scattering pattern S1, S2 formed by the same pattern of the aperture 301.

[0186] Thus, we can predict that the minimum distance Z and the aperture 301, in particular the dimension a, are configured so that L Bases ≥ 2*Lpix when the first 31 and second 32 diffused parts passing through the aperture 301 together define an angle θ ij ≥ δθ. Preferably, L Bases ≥ 5*Lpix. Preferably, L Bases ≥ 10*Lpix.

[0187] Preferably, the base BS1, BS2 is measured at a height of peak S1, S2 equal to 10% of the height HS1, HS2 of vertex SS1, SS2, and preferably located at a height of peak S1, S2 equal to 5% of the height of vertex SS1, SS2. The heights HS1, HS2 of vertices SS1, SS2 are illustrated in figures 3 .

[0188] This ability of detector 1 to distinctly identify the scattering diagram S1, S2 of each particle 101, 102 can also be characterized with respect to the distance L Vertices expressing the offset between the vertices SS1, SS2 of the scattering diagrams S1, S2.

[0189] Thus, we can predict that the minimum distance Z and the aperture 301 are configured so that LVertices ≥ 10*Lpix when the first 31 and second 32 parts passing through the aperture 301 together define an angle θij ≥δθ. Preferably, LVertices ≥ 20*Lpix. Detector sizing

[0190] The detector is characterized in particular by its angular resolution δθ, by the distance Z separating the dark reticle 30 from the retina 20, by its field of view FOV and the dimension L of the retina, and by the distance Zp separating the useful detection volume 100 from the dark reticle 30.

[0191] The angular resolution of the detector is preferably on the order of 2°.

[0192] The retina comprises a plurality of photodetectors forming pixels. A pixel pitch Lpix is ​​typically on the order of a few microns, for example, 0.5 µm < Lpix < 20 µm. The retina is preferably a CMOS-type imager. The width L of the retina is typically on the order of a few millimeters, for example, 1 mm < L < 5 mm.

[0193] The field of view FOV depends on the distance Z and the width L of the retina, such that FOV = atan(L / 2Z).

[0194] The field of view (FOV) is typically on the order of a few tens of degrees, for example, 30° < FOV < 90°, preferably around 60°. This field of view can be chosen according to the desired detection volume. In particular, the entire detection volume is preferably contained within this FOV. The distance Z can therefore be adapted according to the distance Zp separating the detection volume from the dark reticle. Specifically, the distance Z is chosen such that 0.5Zp ≤ Z ≤ 20Zp, for example, 100 µm ≤ Z ≤ 2 mm.

[0195] The dark reticle 30 is maintained at a distance Z from the retina 20 by a structural element. This structural element can be in the form of struts, side walls, or a transparent block, for example.

[0196] According to an embodiment illustrated in the figure 9The detector 1 resembles a housing comprising the retina 20 as a "base" and the dark reticle 30 as a "lid." This housing has lateral walls 202 extending between the retina 20 and the dark reticle 30 and forming a closed contour around the internal space 201 located between the retina 20 and the dark reticle 30. The lateral walls have a height Z and are preferably opaque. They can be assembled on the sensitive surface of the retina, adjacent to the active area of ​​the retina containing the photodetectors, or on the sides of the retina, around the sensitive surface of the retina. The internal surfaces of these walls 202, facing the internal space 201, are preferably absorbent. This limits stray reflections within the housing, according to the well-known principle of the camera obscura. This improves the accuracy of the detector 1.

[0197] In this example, detector 1 includes an aperture 301 with the pattern shown in figure 6D A detector 1 comprising side walls as illustrated here may also include other openings and / or other opening patterns.

[0198] According to an embodiment of detector 1 illustrated in the Figure 10 The structural element supporting the dark reticle 30 at a distance Z from the retina 20 is a transparent block 200. Thus, in this example, light rays propagate within the material of this block. The block 200 is preferably monolithic. It contains no voids or air within it.

[0199] The dark reticle 30 is formed on the upper surface of the transparent block. In one option, an anti-reflective coating is deposited between the dark reticle 30 and the upper surface of the transparent block 200. This limits or even eliminates reflections of scattered light rays k d1 at the aperture 301, particularly at the upper surface of the transparent block 200 exposed through the aperture 301. This anti-reflective coating notably improves the sensitivity of the detector.

[0200] Alternatively, if the transparent block 200 extends into the aperture 301, or if the aperture 301 is filled with another transparent material, so as to form a transparent surface flush with the opaque surface 300 of the dark reticle 30, the anti-reflective coating can be deposited above the dark reticle, on the transparent and opaque surfaces.

[0201] The lateral surfaces 300b of the transparent block 200 are preferably opaque. For example, they are covered by an opaque coating, and preferably by an opaque and absorbent coating. The retina 20 is thus attached to a block forming a dark chamber open only at the optical aperture 301. On the Figure 10 , a particle 10 1 receiving incident rays ki and scattering scattered rays k d1 is illustrated. A part 51 of the scattered light rays k d1 is stopped by the dark reticle, and a part 31 of the scattered light rays k d1 is transmitted through the dark reticle, through the aperture 301. This part 31 propagates in the transparent block 200 to the retina 20, to form the scattering diagram S 1 .

[0202] The transparent block 200 can be made of a transparent material such as glass, optical polymer, silicone, plastic, or a sol-gel compound. In this case, the transparent block has a higher refractive index than the useful detection volume (typically air). The S1 scattering pattern projected through such a transparent block is slightly distorted by refraction. This distortion is not problematic in practice. It may be characteristic of the use of such a detector. Furthermore, it can be corrected by adapting the shape of the aperture (example of a negative curvature pattern illustrated in the...). figure 6G ).

[0203] The opening pattern 301 shown here is an example of a combination of cross patterns ( figure 6D ) and ring ( figure 6I ).

[0204] When several particles are illuminated simultaneously in the useful detection volume, the retina receives several scattering patterns projected through the dark reticle.

[0205] There figure 11 presents a calculation result based on Mie theory, which was projected by ray tracing using a Monte Carlo method. This result shows three scattering diagrams S1, S2, S3 obtained for three particles of different sizes (polystyrene spheres of 1, 2, and 4 µm) detected by detector 1, illustrated in the Figure 10 In this example, if pattern 301 is an aperture delimited by an optical blocking zone, then the reticle is a dark reticle. In this case, each scattering diagram S1, S2, S3 forms a spot of light on the retina 20.

[0206] As mentioned previously, these S1, S2, and S3 scattering patterns are slightly distorted by refraction. Nevertheless, these S1, S2, and S3 scattering patterns are clearly distinct on the retina. It is therefore perfectly possible to count the particles. For example, it is possible to distinguish on each S1, S2, and S3 pattern the pinhole pattern located at the intersection of two slits. L12 corresponds to the distance between this pattern formed by the S1 pattern and the pattern formed by the S2 pattern. L13 corresponds to the distance between this pattern formed by the S1 pattern and the pattern formed by the S3 pattern. L23 corresponds to the distance between this pattern formed by the S2 pattern and the pattern formed by the S3 pattern. It is also possible to determine the geometric (diameter) and optical (refractive index) parameters of each of the particles, after analysis of the S1, S2, S3 scattering diagrams.The detector can notably be coupled to a system with such analysis capabilities, for example a microprocessor and an ad calculation routine. hoc.

[0207] According to an embodiment illustrated in Figures 12 , 13A , 13B And 13C , at least one optical blocking zone has a surface area smaller than that of at least one optical passage zone.

[0208] Thus, a clear reticle 30 comprising an opaque surface 300 in the shape of a cross, for example, and a transparent surface 301 surrounding the opaque surface 300 may be preferred to the examples described above. Other patterns of opaque surface 300 may, of course, be used. For example, and without limitation, the aperture patterns illustrated and described previously may form the opaque surface(s) 300 of the clear reticle 30 according to this embodiment. The opaque surface(s) 300 and the aperture(s) 301 of the clear reticle 30 may thus be inverted with respect to the previous examples, so as to obtain a negative projection of the diffusion patterns on the retina.

[0209] There figure 13A illustrates the projection onto the retina 20 of a scattering diagram S1 from a single scattering particle, through the clear reticle 30 illustrated in the figure 12This diffusion diagram is delimited by a shadow corresponding to the opaque cross present on the clear reticle 30.

[0210] In this case, the S1 scattering pattern occupies a large portion of the retinal surface 20. This allows for the collection of a greater amount of information contained in the scattering pattern. Information regarding the size and nature of the scattering particle can be determined from this S1 scattering pattern. The projected shadow B1 formed by the opaque surface 300 allows the position of the scattering particle to be determined. It confirms that only one particle has been detected.

[0211] There figure 13B illustrates the projection onto the retina 20 of two scattering diagrams S1, S2 from two scattering particles, through the clear reticle 30 illustrated in the figure 12 .

[0212] The rays scattered by these scattering particles reach the retina 20 over a major part of its surface and form the superposition of the scattering diagrams S1 + S2. The opaque surface 300 blocks these scattered rays and forms two shadows B1, B2 on the retina 20. The projected shadow B1 corresponds to the first scattering particle and the projected shadow B2 corresponds to the second scattering particle.

[0213] The superposition of the S1 + S2 scattering diagrams is difficult to use. It creates a bright background on the retina, mixing the information carried by the S1 and S2 diagrams. On the other hand, the projected shadows B1 and B2 can be used to determine at least the position, preferably also the size, and ideally also the nature of the scattering particles.

[0214] Shadow B1 receives no scattered rays from the first particle. However, shadow B1 receives at least some scattered rays from the second particle. Therefore, shadow B1 contains scattering information related to the second particle.

[0215] Similarly, shadow B2 receives no scattered rays from the second particle. However, shadow B2 receives at least some scattered rays from the first particle. Therefore, shadow B2 contains scattering information related to the first particle.

[0216] The overlapping areas 321 and 322 of shadows B1 and B2 receive neither the scattered rays from the first particle nor the scattered rays from the second particle. The contrast with the background light is greatest in these overlapping areas 321 and 322.

[0217] Information relating to the positions of the particles can be determined from the positions of the shadows projected B1, B2 on the retina 20, and / or the positions of the overlapping areas 321, 322 on the retina 20.

[0218] Information relating to particle sizes can be determined from the surfaces of shadows projected B1, B2 on the retina 20, and / or the surfaces of overlapping areas 321, 322 and / or the shape ratios of these surfaces on the retina 20.

[0219] Information relating to the nature of the particles (e.g. their refractive index) can be determined from the contrast ratio of the shadows projected B1, B2 on the retina 20.

[0220] The size and refractive index of a particle are typically coupled quantities. They can be evaluated both by analyzing the surfaces of the shadows on which the (unmixed) Mie alternations appear and by analyzing the contrast ratios.

[0221] Information regarding the size and nature of the first particle can be determined from the portion of the diffusion diagram for this first particle contained in B2. Information regarding the size and nature of the second particle can be determined from the portion of the diffusion diagram for this second particle contained in B1.

[0222] Thus, this embodiment makes it possible to determine a great deal of information relating to the particles.

[0223] There figure 13Cillustrates the projection onto the retina 20 of three scattering diagrams S1, S2, S3 from three scattering particles, through the clear reticle 30 illustrated in the figure 12 .

[0224] The superposition of the S1 + S2 + S3 scattering diagrams is difficult to use. It creates a bright background on the retina, mixing the information carried by the S1, S2, and S3 diagrams. However, the projected shadows B1, B2, and B3 can be used to determine at least the position, preferably also the size, and ideally also the nature of the scattering particles, according to the principle described above for the case of two scattering particles.

[0225] In this case, however, only the overlapping zones 321, 322, and 323 between shadows B1, B2, and B3 are likely to contain a portion of the scattering diagram relating to a single scattering particle. Specifically, the overlapping zones 321 and 322 of shadows B1 and B2 receive neither the scattered rays from the first particle nor the scattered rays from the second particle. Conversely, the overlapping zones 321 and 322 receive at least some of the scattered rays from the third particle. These overlapping zones 321 and 322 therefore contain scattering information relating to the third particle. The overlapping zones 323 and 324 of shadows B2 and B3 receive neither the scattered rays from the second particle nor the scattered rays from the third particle. Similarly, the overlapping zones 323, 324 receive at least some of the rays scattered by the first particle.These overlapping areas 323, 324 therefore contain diffusion information relating to the first particle.

[0226] Information relating to the positions of the particles can be determined from the positions of the shadows projected B1, B2, B3 on the retina 20, and / or the positions of the overlapping areas 321, 322, 323, 324 on the retina 20.

[0227] Information relating to particle sizes can be determined from the surfaces of shadows projected B1, B2, B3 on the retina 20, and / or the surfaces of overlapping areas 321, 322, 323, 324 and / or the shape ratios of these surfaces on the retina 20.

[0228] Information relating to the nature of the particles can be determined from the contrast ratio of the shadows projected B1, B2, B3 on the retina 20.

[0229] The size and refractive index of a particle are typically coupled quantities. They can be evaluated both by analyzing the surfaces of the shadows on which the (unmixed) Mie alternations appear and by analyzing the contrast ratios.

[0230] Information relating to the size and nature of the first particle can be determined from the portion of the diffusion diagram of this first particle contained in the overlap areas 323, 324. Information relating to the size and nature of the third particle can be determined from the portion of the diffusion diagram of this third particle contained in the overlap areas 321, 322.

[0231] According to an embodiment illustrated in the figure 14The reticle 30 comprises at least one optical blocking zone 300 (opaque surfaces) and at least one optical passage blocking zone 301 (transparent surfaces). In this example, the reticle has several zones 300 and several zones 301. The zones 300 and zones 301 are in the same proportion. The total area of ​​the optical passage zones 301 is equal to the total area of ​​the optical blocking zones 300, to within X%, with X less than 15%, preferably X less than 10%, and preferably X less than 2%.

[0232] This allows us to combine the advantages of direct analysis from parts of diffusion diagrams transmitted through the dark reticle, and the advantages of indirect analysis from shadows projected through the light reticle.

[0233] Various patterns of transparent and opaque surfaces, with or without symmetry, can be integrated into the reticle 30. figure 14This illustrates an example combining straight and curved slit patterns, and solid or recessed patterns of roughly triangular shape. These patterns preferably alternate opaque and transparent portions. Canal crossing

[0234] In one embodiment, detector 1 includes a fluidic channel. This fluidic channel is configured to guide the flow of particles to be analyzed to the useful detection volume. This optimizes the detector's efficiency.

[0235] The fluidic channel preferably passes through the detector, preferably from one side to the other and along the optical axis O. The detector thus exhibits improved compactness. figures 15A to 17 illustrate examples of detector implementation including a fluidic channel.

[0236] As illustrated in Figures 15A and 15BFor example, this fluidic channel 110 can open at an orifice 310 through the dark reticle 30. The orifice 310 is, for example, centered on the reticle 30. Alternatively, the orifice 310 can be located on one side of the reticle. It can have a square, rectangular, round, or other cross-section.

[0237] In the case of a fluidic channel 110 passing through the reticle 30, the reticle 30 preferably comprises at least two openings 301, 302 located on either side of the orifice 310 ( figure 15A ). The two openings 301, 302 are preferably arranged along the propagation axis of the incident rays ki.

[0238] The two openings 301, 302 can have dimensions a 1 , a 2different. They may correspond to different areas 210, 220 of the retina, located approximately directly above apertures 301, 302 along the optical axis. This optimizes the detection of scattered rays according to the direction of the incident rays ki. On the figure 15A The incident rays ki propagate from the primary source towards the first aperture 301, in the plane of the sheet. When a scattering particle is located above the orifice 310, some of the scattered rays are scattered in the direction of propagation of the incident rays ki, while some of the scattered rays are backscattered, in the opposite direction. The intensity of the backscattered portion is lower than that of the portion scattered "frontally" (in the direction of propagation). The first aperture 301 can therefore have a width a 1 smaller than the width a 2 of the second aperture 302. This improves the resolution of the first part of the diffusion pattern projected through the first aperture 301, and improves the detection of the second part of the diffusion pattern projected through the second aperture 302.

[0239] The first zone 210 of the retina may contain photodetectors adapted to frontal scattering conditions. The second zone 220 of the retina may contain photodetectors adapted to backscattering conditions.

[0240] Front scattering is generally brighter than back scattering, which is usually less bright. Therefore, the first zone 210 can contain relatively smaller and more numerous photodetectors, while the second zone 220 can contain relatively larger and more sensitive photodetectors. This improves the resolution of the first part of the scattering pattern formed on the first zone 210 and enhances the detection of the second part of the scattering pattern formed on the second zone 220.

[0241] The openings 301, 302 and zones 210, 220 of the retina can thus be adapted according to the lighting and diffusion conditions.

[0242] There figure 15BThis presents a more general embodiment in which the reticle 30 comprises four apertures 301, 302, 303, 304 and the retina comprises four corresponding zones 210, 220, 230, 240. The apertures 301, 302, 303, 304 and the zones 210, 220, 230, 240 are distributed around the traversing fluidic channel 110, in planes normal to the optical axis along which the channel 110 extends, that is, in planes parallel to the plane of the sheet. The two apertures 301, 302 are preferably arranged along the axis of propagation of the incident rays ki, as in the preceding embodiment. The third and fourth openings 303, 304 are preferably arranged on either side of the axis of propagation of the incident rays ki.

[0243] The first aperture 301 is thus dedicated to front diffusion, the second aperture 302 is thus dedicated to back diffusion, and the third and fourth apertures 303, 304 are thus dedicated to lateral diffusion.

[0244] In general, the number of apertures in the reticle and / or retinal zones of the detector according to the invention can vary. This number can, for example, be odd. The aperture pattern(s) are not necessarily symmetrical on either side of the orifice. They are preferably optimized according to the scattering zone (frontal, lateral, backscatter).

[0245] A detector 1 comprising a through fluidic channel 110 is illustrated in the figure 16 .

[0246] The fluidic channel 110 passes through the retina 20, the transparent block 200, and the dark reticle 30 along the entire height of the detector 1. Each element (retina, block, reticle) is, for example, pre-drilled and then assembled to form the fluidic channel. The walls 111 of the fluidic channel 110 are thus formed directly within the transparent block 200 and the retina 20.

[0247] The cross-section of this fluidic channel 110 has dimensions ranging from 100 µm to 2 mm. This cross-section can have a rectangular, square, circular, elliptical, oblong shape, etc.

[0248] In this non-limiting example, the aperture patterns 301, 302 of the dark reticle 30 are formed of at least one pinhole and / or at least one slit, arranged for example in the shape of a cross as illustrated in the figure 6D . The openings 301, 302 are advantageously distributed on either side or around the fluidic channel 110 passing through.

[0249] According to this embodiment, the structural element maintaining the dark reticle at distance Z from the retina is a transparent block, and this transparent block is perforated to form the channel. Alternatively, the structural element can take the form of struts or side walls. In this case (not illustrated), additional internal walls are used to form the channel.

[0250] Preferably, the walls 111 of channel 110 are opaque or coated with an opaque material. This prevents stray light rays from reaching the retina.

[0251] According to an embodiment illustrated in the figure 17The cross-section of channel 110 is not constant along the height of detector 1, that is, in a direction substantially perpendicular to the principal plane in which the retina 20 extends. In particular, the walls 111 can be inclined so as to reduce the cross-section of channel 110 at the orifice 310. Thus, the inlet of channel 110 has a larger cross-section than that of the orifice 310, which forms the outlet of channel 110. The channel therefore forms a conical particle injection nozzle. This makes it possible to concentrate and accelerate the flow of particles 101, 102 within the useful detection volume 100. The sensitivity of detector 1 is thereby improved.

[0252] The particle injection nozzle can alternatively have a pyramidal shape with a square base, or a narrowing of any shape. Manufacturing process

[0253] THE figures 18A to 18GThese diagrams illustrate steps in a manufacturing process for a detector comprising a dark reticle and a through channel. In this embodiment, the detector's structural element is a transparent block. Naturally, additional steps can be inserted between those mentioned below.

[0254] The first step is to provide 400 a transparent substrate 40. This substrate 40 can be made of glass, for example Borofloat 33 glass. It can be in the form of a plate with a diameter of 200 mm and a thickness Z = 725 µm.

[0255] An opaque layer 42 is deposited over the entire plate. This opaque layer 42 can be made of metal, for example gold (Au), and have a thickness of approximately 100 nm. A bonding layer 41, for example titanium (Ti) 10 nm thick, can be deposited prior to the deposition of the opaque layer 42 ( figure 18A). The opaque layer 42 can alternatively be made of copper (Cu), aluminum-silicon alloy (AISi), or carbon (C).

[0256] A second step consists of etching 401 a plurality of channels 110 across the entire thickness of the substrate 40, for example by deep laser etching ( figure 18B ).

[0257] A third step consists of forming 402 of the 301 openings by photolithography ( figure 18CIn a known manner, a layer of photosensitive resin 43 is deposited and then exposed through a mask containing aperture patterns, so as to transfer these patterns. The exposed resin layer is then developed to partially expose the opaque layer 42 at the level of the transferred aperture patterns. An etching, for example by wet etching, of the opaque layer 42 at the exposed areas is then carried out to form the apertures 301 containing said aperture patterns. The resin layer is then removed (a step called "stripping" in Anglo-Saxon terminology). The dark reticle(s) are thus formed.

[0258] A fourth step consists of separating 403 the different transparent blocks 1a, 1b, 1c each comprising a channel 110 and at least one aperture 301, so as to form a plurality of detectors ( figure 18DThis step can be done by laser drilling, for example using a femtosecond laser.

[0259] An optional cleaning step can be performed to remove engraving or drilling residue from the free surfaces of the transparent block (at the openings 301, the channel 110, the lateral surfaces 300b, as illustrated in the figure 18E ).

[0260] Preferably, but optionally, an opacification step is performed on the walls of channel 110 and the lateral surfaces 300b. The surface 300 and the openings 301, 302 of the dark reticle are masked beforehand. A masking or protective layer 44 is applied, for example. The walls of channel 110 and the lateral surfaces 300b are then made opaque, for example by spraying black paint ( figure 18F ).

[0261] The masking layer is then removed. The resulting transparent block has opaque lateral surfaces 300b. It is surmounted by a dark reticle 30 comprising a reflective opaque surface 300 and openings 301, 302. It is further traversed by a channel 110 delimited by opaque walls ( figure 18G ).

[0262] In an alternative embodiment, the photosensitive resin is black and absorbent. The stripping and opacification steps are thus advantageously eliminated. The resulting dark reticle 30 comprises an absorbent opaque surface 300.

[0263] According to another embodiment illustrated in figures 19A, 19B The transparent block 200c is formed from a molded transparent polymer. The channel 110 is therefore obtained directly after molding.

[0264] According to this example, caches 44 in the shape of the opening patterns are then placed on either side of channel 110 ( figure 19A ). These 44 covers can be made from a protective film cut and glued onto the surface of the 200c transparent block.

[0265] An opacification step by paint spraying is then carried out. All surfaces can thus be covered with absorbent black paint, except for the surfaces masked by the masks 44. By removing the masks 44, the resulting transparent block has opaque lateral surfaces 300b. It is surmounted by a dark reticle 30 comprising an absorbent opaque surface 300 and optical apertures 301, 302. It is also traversed by a channel 110 delimited by opaque walls ( figure 19B ).

[0266] According to another possibility, the opaque surface 300 is formed by sticking a previously cut opaque plastic film at the canal orifice and optical openings.

[0267] The resulting transparent block is then assembled with a retina (CMOS imager) to form the detector. For example, an optical adhesive is applied to the side of the imager containing the photodetectors. The transparent block is then positioned opposite this side and aligned with the imager, preferably using pre-defined alignment patterns. This step can be performed using a pick-and-place machine, such as those offered by Datacon.

[0268] The block is then glued and sealed to the imager by thermal curing of the adhesive. The manufacturing cost of such a detector is thus significantly reduced. Beam of light

[0269] The detector according to the invention can be coupled with various light sources within the useful detection volume 100. These light sources are described below. They can form a detection system with the detector according to the present invention. They can also constitute a separable component of the detector that can be used independently of the detector.

[0270] There figure 20A This illustrates a cylindrical incident beam ki, for example collimated, emitted by a source 11a. The resulting useful detection volume 100 is thus cylindrical. By combining such a useful detection volume 100 with a detector 1 comprising a pinhole aperture 301, the particle count 10₁, 10₂ can be biased. This bias can occur, in particular, when the particles 10₁, 10₂ and the pinhole 301 are substantially aligned in the same direction, that is, when θ ij < δθ , as illustrated in the figure 20AIn this case, the scattered parts 31, 32 through the pinhole form a single scattered beam, resulting in a single pattern or spot S(θ) on the retina 20. The scattering patterns of the two particles 10₁, 10₂ are partially indistinguishable. It is then very difficult to distinguish the two particles 10₁, 10₂. One solution may be to use a more complex aperture pattern, for example as illustrated in figures 6C to 6J .

[0271] An illustrated alternative solution to the figure 20BThis involves modifying the illumination beam and, consequently, the useful detection volume 100. A source 11b emitting an elliptical or flattened beam can reduce or even eliminate the risk of two particles 10₁, 10₂ aligned with the pinhole scattering simultaneously. This reduces the risk of overlapping the signatures of the particles 10₁, 10₂ on the retina. The cross-section of this beam therefore has a large dimension and a small dimension, and the large dimension is preferably perpendicular to the optical axis O. The ratio between the large dimension and the small dimension is, for example, on the order of 5:1; preferably, this ratio is on the order of 10:1.

[0272] The propagation direction of the source beam is not necessarily parallel to the plane of the dark reticle 30. It is nevertheless chosen so as not to directly dazzle the retina 20 of the detector through the dark reticle 30. Depending on one possibility, the source beam can be focused, diverging or convergent.

[0273] In one embodiment, the illumination of the particle(s) within the useful detection volume comprises several wavelengths or colors. This allows, in particular, for a more refined analysis of a particle, and specifically reduces uncertainties in estimating its size. Such color analysis is described, for example, in the publication "S. Wang, X. Xiao, T. Deng, A. Chen, M. Zhu, A Sauter mean diameter sensor for fire smoke detection, Sensors & Actuators: B. Chemical 281 (2019) 920-932".

[0274] In one example, the detection area is illuminated by two (or more) collinear beams of the same direction and different wavelengths. Alternatively, a single "white" beam, whose spectral width can extend across the visible spectrum, illuminates the detection area.

[0275] Such polychromatic collinear light sources can be combined with a detector comprising a color-sensitive retina. The retina's photodetectors can, for example, include red, green, or blue colored filters. In particular, "red" photodetectors (i.e., those containing a red filter) can be alternated with "blue" and "green" photodetectors. The set of "red," "green," and "blue" photodetectors preferably forms a Bayer mosaic. This allows for the creation of three "colored" scattering diagrams, corresponding to the three colors of the photodetectors. Such a detector enables color analysis of the particles to be detected.

[0276] There figure 21A presents another configuration allowing for color analysis of the particles to be detected.

[0277] According to this embodiment, the particle(s) to be detected are illuminated by at least two beams kir, kib of different colors with different propagation directions. These beams may have a non-zero angle β between their propagation directions. These beams may optionally be collinear and counter-propagating (β = 180°). There may be three or more beams. They may exhibit colors within the silicon absorption range, particularly in the visible spectrum, for example green, blue, red, and / or in the near-UV and / or near-infrared (NIR) ranges.

[0278] The detector 1 associated with this lighting configuration advantageously includes an aperture 301 that separates the scattered rays according to the propagation directions of the incident beams. The geometry of the aperture 301 pattern is chosen based on these propagation directions.

[0279] In the example illustrated at the figure 21AThe particle 10₁ is illuminated by two beams k₀r and kₐb, whose propagation directions are parallel to the plane of the dark reticle 30 and form an angle β of approximately 90° between them. The pattern of aperture 30₁ can therefore be formed by combining a portion of a first ellipse aligned (along its major axis) with the propagation direction of the k₀r beam, and a portion of a second ellipse aligned (along its major axis) with the propagation direction of the kₐb beam. The major axes of the first and second ellipses form the angle β between them. The first ellipse is optimized for the color of the k₀r beam, for example, red, and the second ellipse is optimized for the color of the kₐb beam, for example, blue. This optimizes the transmission of the colored Mie lobes for the particle 10₁. The diffusion diagram (S 1r , S 1b ) formed on the retina 20 is therefore a superposition of the two colored diffusion diagrams S 1r , S 1b .

[0280] The two colored scattering patterns S1r and S1b are shifted by the angle β in the plane of the retina. Furthermore, they exhibit optimal light intensity due to the alignment of the major axes of the ellipses with the propagation directions of the source beams. This allows for optimal differentiation between the two colored scattering patterns S1r and S1b. Such a detector therefore also enables color analysis of the particles to be detected.

[0281] Another embodiment of a system comprising a detector and colored sources is illustrated in the figure 21B According to this example, the dark reticle 30 comprises at least two colored apertures 301r, 302b, adapted to the colors of the incident beams k ir, k ib. These apertures 301r, 302b are separated from each other and can have different patterns. For example, they form concentric rings or ellipses, as illustrated in figure 21BIn practice, apertures 301r and 302b can be covered by a colored filter. For example, the k-ir beam is red, and aperture 301r is covered with a red filter that preferably transmits only the red 31r scattered rays. The k-ib beam is blue, and aperture 302b is covered with a blue filter that preferably transmits only the blue 31b scattered rays. As another example, the k-ir beam is NIR, and aperture 301r is covered with a NIR filter that preferably transmits only the NIR 31r scattered rays. The k-ib beam is red, and aperture 302b is covered with a red filter that preferably transmits only the red 31b scattered rays. The red and NIR filters can be made from inexpensive layers. This reduces the cost of the detector.According to another more general example, the kib beam exhibits a color associated with a first wavelength and the kir beam exhibits a color associated with a second wavelength, with the first wavelength strictly less than the second wavelength.

[0282] Each aperture can thus be specific to one of the colors of the light source. Consequently, colored scattering patterns S1b, S1r of the particle 101 are projected onto the retina 20 of detector 1. These colored patterns S1b, S1r are separated on the retina. Such a detector therefore allows for color analysis of the particles to be detected, even if the retina is not color-sensitive. This detector can also operate with different polychromatic sources, for example, collinear polychromatic sources, as illustrated in the figure 21BIt is also possible to use a white beam and limit the color analysis to just a few colors.

[0283] The invention is not limited to the embodiments described above. The invention is limited by the scope of claims 1-15.

[0284] In general, examples of detectors with an aperture producing T1 and T2 spots can be transposed, barring incompatibilities, to detectors with a dark surface producing B1 and B2 shadows, and vice versa. Thus, the characteristics, technical effects, and advantages mentioned regarding embodiments with a dark reticle are valid for embodiments with a light reticle.

Claims

1. Optical detector (1) for particles (10i, 10j), referred to as lensless, designed to simultaneously detect at least one first particle (101) and at least one second particle (102) within a useful detection volume (100) intended to accommodate a fluid carrying particles (10i, 10j) and to be traversed by incident light rays (ki) emitted by at least one primary source (11a, 11b) said first and second particles (101, 102) respectively forming first and second secondary sources (21, 22) respectively emitting, when located within the useful detection volume (100) and diffusing part of the incident light rays (ki), first diffused light rays (kd1) and second diffused light rays (kd2), said detector (1) comprising a retina (20) made up of a plurality of photodetectors capable of receiving diffused light rays, said detector (1) furthermore comprising at least one reticle (30) interposed between the useful detection volume (100) and the retina (20), said reticle (30) comprising: - at least one optical passage area (301, 302) allowing a pathway to the retina (20) for a part (31) of the first diffused light rays (kd1) and a part (32) of the second diffused light rays (kd2), said portions of the first and second diffused light rays being referred to as the first (31) and second (32) diffused parts, respectively, - at least one optical blocking zone (300) preventing a passage to the retina (20) of a part (51) of the first diffused light rays (kd1) and a part (52) of the second diffused light rays (kd2), at least one of said optical passage and blocking zones (301, 300): - being separated from the retina (20) by a minimum distance Z measured along an optical axis (O) perpendicular to the retina, - further having at least one dimension taken in a direction transverse to the optical axis (O), the reticle (30) and the retina (20) being configured, in particular the minimum distance Z and the dimension a, such that: - the first diffused part (31) is received by a first set of photodetectors the distribution of which delimits on the retina a first figure taken from a spot (T1) and a shadow (B1), - the second diffused part (32) is received by a second set of photodetectors the distribution of which delimits on the retina a second figure taken from a spot (T2) and a shadow (B2), said second figure (T2, B2) being at least in part distinct from the first figure (T1, B1) when the first (31) and second (32) parts passing through the at least one optical passage area (301, 302) together define an angle θij the value of which is at least equal to an angular resolution δθ of the detector (1), said optical detector (1) being characterised in that it does not comprise a lens between the reticle (30) and the retina (20).

2. Optical detector (1) according to the preceding claim, wherein the reticle (30) and the retina (20) are configured, particularly the minimum distance Z and the dimension a, such that the second figure (T2, B2) is offset relative to the first figure (T1, B1) on the retina (20), the smallest distance Ls corresponding to this offset between these two figures (T1, T2, B1, B2) being greater than or equal to 2*Lpix, when the first (31) and second (32) diffused parts passing through at least one optical passage area (301, 302) together define an angle θij the value of which is at least equal to an angular resolution δθ of the detector, Lpix being the pitch between two adjacent photodetectors of the retina.

3. Optical detector (1) according to the preceding claim, wherein said dimension a is configured so that a = Z . tan δθ − L s Z p Z + Z p where Zp is the minimum distance separating the useful detection volume from at least one of said optical passage and blocking areas (301, 300).

4. Optical detector (1) according to any one of the preceding claims, wherein the reticle (30) and the retina (20) are configured, in particular the minimum distance Z and the dimension a, so as to generate on the retina (20) at least a first diffusion diagram S1 formed by the first diffused part (31) and a second diffusion diagram S2 formed by the second diffused part (32), said at least first and second diffusion diagrams S1, S2 each forming at least one light peak (S1peak, S2peak) corresponding to the at least one optical passage area (301, 302) and having a base (BS1, BS2), the bases (BS1, BS2) of each diffusion diagram S1, S2 being offset on the retina (20) by a separation distance LBases ≥ 2*Lpix when the first (31) and second (32) parts, passing through the optical passage area (301), together define an angle θij the value of which is at least equal to an angular resolution δθ of the detector (1), Lpix being the pitch between two adjacent photodetectors of the retina (20).

5. Optical detector (1) according to the preceding claim, wherein the peak S1Pic, S2pic of each diagram comprises at least one vertex (SS1, SS2), the base (BS1, BS2) being located at a height of the peak (S1Pic, S2Pic) equal to 10% of the height (HS1, HS2) of the vertex (SS1, SS2), and preferably located at a height of the peak (S1pic, S2pic) equal to 5% of the height (HS1, HS2) of the vertex (SS1, SS2).

6. Optical detector (1) according to any one of the preceding claims, wherein the at least one optical passage area (301, 302) comprises at least one pinhole pattern and at least one slit pattern, said patterns being partially superimposed.

7. Optical detector (1) according to any one of the preceding claims, wherein the optical passage area (301, 302) comprises a plurality of pinhole patterns.

8. Optical detector (1) according to any one of the preceding claims, wherein the optical passage area (301, 302) comprises at least one curved slit pattern (311-c) having a curvature directed towards the centre of the reticle (30).

9. Optical detector (1) according to any one of the preceding claims, wherein the dimension a is such that a ≥ 10.Lpix.(Z / (Z+Zp)), where Zp is the minimum distance separating the useful detection volume (100) from at least one of said optical passage and blocking areas (301, 300), and Lpix is the pitch between two adjacent photodetectors of the retina (20).

10. Optical detector (1) according to any one of the preceding claims wherein the distances Z and Zp are such that 0.2.Z ≤ Zp ≤ 2. Z where Zp is the minimum distance separating the useful detection volume (100) from at least one of said optical passage and blocking areas (301, 300).

11. Optical detector (1) according to any one of the preceding claims, wherein the useful detection volume (100) is contained within an angle FOV = atan (L / 2z), where L is a lateral dimension of the retina (20) taken in a plane parallel to a face of the retina (20) that is oriented towards the reticule (30), said angle FOV having a vertex extending from at least one opening (301, 302) and an axis of symmetry parallel to the optical axis (O), with said FOV angle defining a field of view of the optical detector (1).

12. Optical detector (1) according to any one of the preceding claims, furthermore comprising at least one fluidic channel (110) configured to guide the particles (10i, 10j) to the useful detection volume (100), the at least one channel (110) passing through the reticle (30) at an orifice (310) formed in the reticle (30).

13. Optical detector (1) according to the preceding claim, wherein the at least one optical passage area (301, 302) comprises a plurality of optical passage areas (301, 302, 303, 304) distributed around the orifice (310).

14. Optical detector (1) according to the preceding claim, wherein the plurality of optical passage areas (301, 302, 303, 304) comprises at least one first optical passage area (301) and at least one second optical passage area (302) located on either side of the orifice (310) of the channel (110).

15. Optical detector (1) according to the preceding claim, wherein said at least one first optical passage area (301) has a characteristic dimension (a1) at least two times smaller than a characteristic dimension (a2) of the at least one second optical passage area (302).