WO2018109350A1

WO2018109350A1 - Protection device used in a lensless imaging detection system and lensless imaging detection system using said device

Info

Publication number: WO2018109350A1
Application number: PCT/FR2017/053503
Authority: WO
Inventors: Pierre-Alexandre Setier; Anais ALI CHERIF; Pierre BLANDIN; Guilhem Couderc; Yves Fouillet
Original assignee: Commissariat à l'énergie atomique et aux énergies alternatives; Horiba Abx Sas
Priority date: 2016-12-16
Filing date: 2017-12-11
Publication date: 2018-06-21
Also published as: FR3060747A1; FR3060747B1; EP3555594A1

Abstract

The invention relates to a protection device intended to be used in a system for detecting objects of interest dispersed in a sample, said system comprising: - a source (1) of light radiation intended to emit light radiation (10) in a main direction (X); - an image sensor (2); - a transparent display zone (Z) intended to receive said sample and positioned between said source (1) of light radiation and said sensor (2), and said sensor (2) being arranged to acquire an image of the sample on its surface on the basis of radiation transmitted through the display zone by said radiation source; - said device comprising protection means to be interposed between the source (1) of light radiation and said display zone (Z) in order to protect said display zone from the deposition of impurities.

Description

Protective device used in a lensless imaging detection system and a lensless imaging detection system employing said device

Technical field of the invention

The present invention relates to a protection device used in a system for detecting objects of interest in a sample, and to a detection system using said protection device.

State of the art

To analyze objects of interest contained in a sample, such as for example cells, bacteria or viruses, it has recently been proposed imaging systems without lenses. These systems have the advantage of being inexpensive compared to conventional solutions such as optical microscopes.

Such a system consists of a source of light radiation, typically a light diode, which illuminates a transparent display chamber in which the sample to be analyzed is placed,

Below the chamber, the system includes a sensor, generally of the CMOS type, which acquires the images. These images are holograms, resulting from the interference between the light field diffracted by the objects of interest and the light field of the bottom that has passed through the viewing chamber without being diffracted. Once acquired images, they are processed by a suitable processing unit.

Then, depending on the intended application, from the images obtained, the processing unit will be adapted to perform different types of programs, for example cell counting and / or tracking of species positions in the sample.

The principle of lensless imaging detection has already been described in the state of the art, in the context of different inventions. This is particularly the case in patent applications US2014 / 160236A1, FR3028038A1, US9212985B2.

The document WO2014 / 071962A1 also describes a system for optical analysis of a sample, of imaging type without a lens.

James L Flewellen's 2012 publication "Digital Holography Microscopy For Three-Dimensional Studies of Bacteria" proposes a digital holographic microscope (DHM) that can be used in both "inline" and "off-axis" modes. . Simple analysis of holographic images, without reconstruction, is limited to low concentration samples. A holographic reconstruction step makes it possible to implement an analysis on samples of higher concentration. However, the images must be acquired in a clean environment, that is, without dust. Each impurity that slips between the sensor and the radiation source will have an image on the sensor and will therefore be able to be taken into account in the processing performed.

To limit the presence of impurities, it is possible to work in white enclosures equipped for example with dust filtration systems, but this is particularly restrictive. It is also possible to act on the processing of acquired images, but this is often accompanied by a loss of information.

Furthermore, it is proposed to use supports or disposable cards so that the transparent walls of the viewing chamber, which are crossed by the light radiation, are as clean as possible, and devoid of dust the time of the day. 'analysis. However, the deposition of impurities on the card remains possible after unpacking and once installed. Another solution is to directly inject the sample to be analyzed into a reusable viewing chamber, so that the support remains permanently in the detection system. However, the latter practice always poses the problem of depositing dust on the support and causes difficulties in the processing of the images obtained.

The object of the invention is therefore to propose a protection device intended to be used in a detection system as defined above and making it possible to overcome the drawbacks of the prior solutions by proposing a solution in which the dust or other impurities , slipping between the radiation source and the sensor, will not interfere with the analysis of the sample.

Presentation of the invention

This object is achieved by a protection device intended to be used in an object detection system of interest dispersed in a sample, said system comprising:

A source of light radiation intended to emit light radiation in a main direction,

An image sensor, A transparent viewing zone intended to receive said sample, said viewing zone being positioned between said source of light radiation and said sensor, said radiation source being intended to emit said light radiation in the direction of said viewing zone so as to illuminate said light source; zone following at least one plane, said object plane, and said sensor being arranged to acquire on its surface an image of the sample from the radiation transmitted through the viewing zone by said radiation source,

Said device comprising protection means to be inserted between the source (1) of light radiation and said viewing zone (Z) to protect said viewing area from the deposition of impurities, said protection means comprising at least one transparent protective surface configured to form a deposition surface of the impurities, said surface being arranged at a distance which is chosen sufficient from the viewing area so that any impurity deposited thereon forms a diffraction pattern on the image acquired by the sensor which is much larger, less contrasted and more diffuse than diffraction patterns from the diffraction of the objects of interest of the sample present in the viewing area.

It is understood from the foregoing that the object of the invention is to allow the impurities to be deposited on the protective surface rather than in the viewing zone and then to position the protective surface in a suitable manner with respect to the visualization so that the diffraction patterns from the impurities that are present are sufficiently different from those that come from the objects of interest present in the viewing area. By the expression "differs sufficiently", it is meant that these diffraction patterns must be easily distinguishable from those derived from objects of interest.

In the solution of the invention, it is therefore not a question of trying to remove the impurities, nor of removing the diffraction images resulting from the impurities by adjusting the coherence length of the source but rather of adapting to the presence of impurities and to ensure that they generate diffraction patterns sufficiently different from those of the objects of interest.

The solution of the invention can operate whatever the coherence length chosen for the source of light radiation. However, it is necessarily of particular interest when the coherence length of the source is high. In this situation, the principle of the invention makes it possible to place the protective surface in the coherence zone of the source, so as to ensure that the impurities present in this zone are deposited on the protective surface rather than in the viewing area, and thus produce diffraction images more diffuse and less contrasting than those from the objects of interest present in the viewing area.

According to one particularity of the invention, the protection means are chosen so as to define said protective surface at said sufficient distance taking into account the size of the objects of interest targeted in the sample with respect to the size of the impurities, the intensity of the light radiation emitted by said source of light radiation, the position of the source of light radiation with respect to the sensor, the resolution of the sensor employed and the position of the viewing area relative to the sensor.

To ensure that the diffraction patterns from the impurities are sufficiently different from those of the objects of interest, these different input parameters will have to be taken into account.

According to another feature, the protective surface is flat.

According to a particular embodiment, the protection means comprise a protection piece comprising said protective surface.

According to a particularity, the protection piece has a first so-called upper face forming the protective surface and bearing means opposed to said upper face, and intended to be supported on the support of the system and one or more lateral faces arranged between said upper face and said support means.

According to another feature, the support means comprise a lower face opposite to said upper face and parallel thereto.

According to a particular embodiment, said piece is made of a transparent solid material.

According to another particular embodiment, said piece is hollow and defines an internal volume filled with a gas, gas mixture or vacuum.

According to a feature, said piece has a thickness defined between its upper face and its lower face corresponding to said positioning distance of the protective surface.

According to a particular embodiment, the protective part comprises a lid formed of a plate and a collar on its periphery, said surface of protection being arranged on the plate, said flange being arranged to form said support means against the support at the periphery of said viewing chamber.

According to one feature, the device comprises means for fixing said protection piece.

The invention also relates to a system for detecting objects of interest dispersed in a sample, comprising:

An image sensor,

A transparent viewing zone intended to receive said sample, said viewing zone being positioned between said source of light radiation and said sensor, said radiation source being intended to emit said light radiation in the direction of said viewing zone so as to illuminate said light source; zone following at least one plane, said object plane (P), and said sensor being arranged to acquire on its surface an image of the sample from the radiation transmitted through the viewing zone by said radiation source,

said system comprising:

A protection device according to that defined above, interposed between the radiation source and said viewing area.

According to a particular embodiment, the viewing zone is located in a viewing chamber integrated into a support.

According to another feature, the viewing chamber comprises two opposite walls traversed by said radiation and said upper wall and lower wall, said upper wall having a first so-called inner face, located in the viewing chamber and a second face, said outer face. located outside said viewing chamber.

According to another feature, the viewing chamber comprises two opposite walls traversed by said radiation and said upper wall and lower wall, said upper wall having a first so-called inner face, located in the viewing chamber and a second face, said outer face. located outside said viewing chamber, and in that said protective surface of the protective device is formed by the outer face of said upper wall. According to another particular embodiment, the viewing zone is located on the surface of a support.

According to another particular embodiment, the viewing zone is located in a viewing cavity formed by a recess formed on the surface of a support.

Advantageously, the protective surface is positioned at a distance from the sensor surface of between 1 and 100% of the total distance between the radiation source and the surface of the sensor.

According to one feature, the system comprises a housing adapted to receive said protective device removably.

According to another particularity, the source of light radiation comprises at least one light emitting diode or laser.

According to another particularity, the sensor is of the CMOS type. Brief description of the figures

Other features and advantages will appear in the detailed description which follows in conjunction with the appended figures listed below:

Figures 1 A and 1 B illustrate the principle of the invention. In Figure 1A, the system is in accordance with the state of the art and in Figure 1B, the detection system is according to the invention, that is to say provided with a protective surface.

FIG. 2 represents an image obtained with a detection system according to the state of the art, that is to say without a protective surface within the meaning of the invention.

- Figure 3A shows an image obtained with a detection system according to the invention, that is to say including a protective surface inserted at a height of 2 cm above the surface of the sensor.

FIG. 3B represents an image obtained with a detection system according to the invention, that is to say including a protective surface inserted at a height of 12 cm above the surface of the sensor.

FIGS. 4A and 4B show, respectively in a cross-sectional view and in a view from above, a first variant embodiment of a support including a viewing zone intended to receive a light radiation from the system.

FIGS. 5A and 5B show, respectively in cross-sectional view and in plan view, a second variant of FIG. providing a support including a viewing area for receiving light radiation from the system.

Figures 6A and 6B show, respectively in a cross-sectional view and in a view from above, a third embodiment of a support including a viewing area for receiving a light radiation system.

Figures 7A to 7C show various embodiments of the invention.

Detailed description of at least one embodiment

In the remainder of the description, an axis (X) is defined which extends in a vertical direction. The terms "upper", "lower", "above", "below", "high" and "low" are to be understood by taking this vertical axis (X) as a reference. This axis (X) corresponds to the main direction of illumination by the source of light radiation. The heights that will be defined below are in particular to be considered along this axis (X).

The detection system of the invention operates on the principle of lensless imaging which is known and which has already been described in the state of the art, especially in the documents already listed above.

The solution of the invention described below applies to any detection system working in holography. It may be an arm or two arms, type inline ("inline") or off-axis ("off-axis").

The invention is implemented independently of the coherence length of the source of light radiation.

The system of the invention is described for an application for detecting objects of interest dispersed in a fluid and thus forming a sample to be analyzed. The objects of interest are, for example, non-exhaustively, particles, droplets, microbeads, blood cells such as white blood cells, red blood cells or platelets, bacteria, cell aggregates.

It will be seen that according to the configuration of the viewing zone Z, the sample to be analyzed can be placed:

In a viewing chamber 30 made in a support,

- On the surface of a support 3 used or,

In a cavity 300 made in a support 3. Without limitation, the support 3 can be in any possible form, for example in the form of a card (for example in credit card format), a cartridge, a blade, a box of Petri ... In the support 3, more precisely but without limitation, a viewing chamber 30 has transparent walls that can be traversed over its height by the light radiation 10 which must illuminate the sample. By way of example and in a nonlimiting manner, these transparent walls are therefore at least arranged in two planes substantially perpendicular to the axis (X) defined above and therefore correspond to its upper wall 31 and to its bottom wall 32. These two walls each have an inner face 310a, 320a located in the viewing chamber 30 and an outer face 310b, 320b located outside of the viewing chamber 30.

Without limitation, a support 3 will be made of a fully transparent material and may include, substantially in its middle, the viewing chamber 30, which is placed in the sample to be analyzed. It may comprise fluidic or even microfluidic channels (not shown) opening into said chamber and used to inject the sample into the chamber. Advantageously but in a non-limiting manner, the support 3 is made of a transparent material such as glass, PMMA (polymethyl methacrylate), COC ("Cyclic Olefin Copolymer" - cycloolefin polymer) or other similar material. The support 3 may be positioned removably or fixed in a suitable housing of the system. The housing will be advantageously accessible from outside the system.

The sample to be analyzed comprises objects of interest 4 dispersed in a fluid. The objects of interest, subjected to a light radiation, form diffraction patterns on the sensor. By way of example, the objects of interest typically have a diameter of between 1 and 100 μm.

The source 1 of light radiation comprises for example a point source such as a light emitting diode. Optionally, a diaphragm, not shown, may be used to increase the spatial coherence of the light radiation emitted by the light-emitting diode. Any other source of coherent or partially coherent light radiation may be provided, such as for example a laser diode. The sensor 2 is intended to acquire images of the light radiation transmitted through the viewing zone, in which the sample to be analyzed is placed. The image acquired by the sensor 2 comprises a plurality of diffraction patterns 40 each derived from the diffraction of the light radiation on an object of interest contained in the sample. The sensor 2 will for example be adapted to acquire several successive images at a defined rate (for example a rate of 40 images per second). As shown in the appended figures, each acquired image comprises several distinct diffraction figures, each generated by the diffraction of the light radiation on an object of interest. For spherical or approximately spherical objects, each figure is formed of a circular central zone, whose intensity is homogeneous, and of concentric rings surrounding said central zone and having alternately low and high intensities. For objects of less regular shape, we obtain comparable spots but without symmetry of revolution.

The sensor 2 used is preferably of the CMOS type (for "Complementary Metal Oxide Semiconductor"). In a variant, it may be of the CCD (for "Charge Coupled Device") type.

The system may or may not include a processing unit, comprising at least one microprocessor and storage means, responsible for recovering the images acquired by the sensor and for processing them according to a determined analysis program (counting, position tracking). .).

As shown in FIG. 1A, in a known manner, the source 1 of light radiation emits light radiation 10 towards the viewing zone Z. In the remainder of the description, it will be assumed that the viewing zone Z is struck by the radiation following at least one object plane, which may be a median object plane P.

Without limitation, in the case of a viewing zone Z included in a viewing chamber 30 integrated in a support 3 (FIGS. 4A and 4B), the light radiation 10 first strikes the outer surface 310b of the upper wall. 31 of the support. The light radiation 10 passes through the upper wall 31 of the support. Then it crosses the viewing room in several planes superimposed objects, in which there are objects of interest. In FIGS. 1A and 1B appended, the median object plane P is represented at all these object planes, this median object plane being that which passes through the viewing zone Z in the middle of its height. Finally, the radiation diffracted by the objects of interest 4 passes through the bottom wall 32 of the support to strike the surface of the sensor 2. The technical problem solved by the invention is particularly understandable with reference to FIG. 1A, on which the sample to be analyzed is placed in a viewing chamber 30.

In FIG. 1A, it can indeed be seen that if a dust 5 or other impurity is deposited on the external face 310b of the upper wall 31 of the viewing chamber 30, this latter will form a diffraction pattern 50 on the image acquired by the sensor 2. Figure 2 illustrates this phenomenon. In FIG. 2, it is indeed noted on the generated hologram that it is difficult to differentiate the diffraction patterns 40 originating from the diffraction of the light radiation on the objects of interest of the sample to be analyzed, diffraction patterns 50 from the diffraction of light radiation on dust or impurities that have deposited on the outer face of the upper wall of the display chamber.

In this configuration, it is understood that the invention is therefore intended to prevent dust or impurities deposited on the outer face 310b of the upper wall 31 of the display chamber 30 from disturbing the analysis and in particular, be considered as an object of interest of the sample by the processing unit during the processing of the image acquired by the sensor 2. The invention is particularly of interest when the support 3 remains permanently in the system and it is therefore exposed to dust or ambient impurities. Other benefits will be listed below.

The invention therefore consists in providing the system with a protection device provided with protection means comprising at least one transparent protective surface 6 which is interposed between the radiation source and the viewing chamber. The protection means are thus arranged for:

Protect, preferably in a hermetic manner, the viewing zone Z of the impurity deposit on its surface and,

- Thanks to the protective surface 6, deport the deposit of dust and impurities in a plane sufficiently far from the object plane P of the viewing zone Z, while allowing the light radiation 10 to pass.

According to the invention, the dust or impurities which are deposited on this protective surface 6 will be visible on the image acquired by the sensor 2, but their diffraction patterns will be much more spread out and less contrasted. Thus they will not be considered during the processing implemented by the processing unit UC. The protective surface 6 will preferably be flat and located in a plane perpendicular to the axis (X).

According to the invention, this protective surface 6 has several important characteristics:

It is the first surface encountered by the light radiation 10;

It is the surface most exposed to the deposit of dust or impurities, so that the dust is preferentially deposited on it, rather than on other surfaces;

It must be transparent and advantageously regular to let the light radiation 10 emitted by the source 1 without degrading;

It must be positioned at a height H sufficient relative to the surface of the sensor to move enough dust out of the object plane P in which the viewing chamber is located. Sufficient height means a height H for which the dust is sufficiently outside this object plane P of the viewing zone Z, so that they can not be considered during the image processing.

FIG. 1B illustrates the principle of the invention, in comparison with the known solution of FIG. 1A, in which the protective surface within the meaning of the invention is not present. In FIG. 1B, the protective surface 6 is in fact positioned at a sufficient height H so that the dust 5 which is deposited thereon form diffraction patterns 50 on the image acquired by the sensor 2 which are much more large, less contrasted and more diffuse than the diffraction patterns 40 from the diffraction of objects of interest 4 of the sample present in the display chamber.

To determine the positioning height H of the protective surface 6 with respect to the surface of the sensor 2, the following parameters, referenced in FIG. 1B, must be taken into account:

The height Htot of the source 1 of light radiation with respect to the surface of the sensor,

The height Hp of the object plane (P) with respect to the surface of the sensor, In addition, the following condition must also be respected:

The height H is always greater than the height Hp and always lower than the height Htot.

From these different elements and according to the height Hp of the object plane (P) relative to the surface of the sensor 2, the height H of the protective surface will be between 1% and 100% of the total height Htot (100% corresponding to the height of the radiation source relative to the surface of the sensor).

This height H chosen for the position of the protective surface 6 corresponds indeed to the height for which the diffraction spots obtained for a dust on the surface of the sensor 2 will have a diameter of first minimum (corresponding to the diameter of the ring the darker) at least twice that of a particle to be detected.

The lower the height Hp of the object plane (P) with respect to the surface of the sensor, the lower the height H is.

For example, without limitation, for a total height Htot of 15 cm and a height Hp of the object plane of 1 mm, the height H is between 2 and 5 cm. If the height Hp is greater than 1 cm, the height H is for example between 5 and 12 cm. Exemplary embodiments will be described hereinafter with reference to FIGS. 3A and 3B.

The protection device and the height of the protective surface must be selected in particular according to the size of the objects of interest present in the sample.

Depending on the various parameters mentioned above, it should be noted that it will be easy to choose the height H to which the protective surface must be positioned above the sample to obtain the desired effect.

Different solutions can be implemented to achieve the protection device. In a first solution shown in both Figure 1 B and shown in Figure 7A, it is formed of a piece 60 independent. This solution will be particularly suitable for being associated with a support comprising a viewing chamber 30 integrated in the support 3 as shown in Figures 4A and 4B. The piece is indeed positioned directly in contact with the outer face 310b of the upper wall 31 of the viewing chamber 30. It thus forms an additional thickness above said chamber, said thickness partly defining the height H of the protective surface. The dust is thus deposited on the protective surface 6 and not on the outer face of the upper wall of the viewing chamber. This piece 60 is positioned on the upper wall so as to leave no space between it and the upper wall of the viewing chamber. It has for example a shape with two opposite parallel faces and one or more lateral faces, forming for example a parallelepiped or a cylindrical (for example of revolution). Its two opposite faces, one of which defines the protective surface 6, are perpendicular to the axis (X). These two faces are transparent. It can be made of the same material as that used for the support 3 and already defined above. It can be full or hollow. In the case where it is hollow, its internal volume is for example filled with a gas, gas mixture (ex: air) or is empty. The part 60 thus formed can be housed in a housing adapted to the upper wall 31 of the chamber 30. According to various embodiments, it can be made integral with the support (for example by gluing, screwing ...) on the wall upper chamber or kept fixed in the system and independent of the support. In the latter case, it must be positioned sufficiently close to the upper wall 31 of the chamber to prevent dust from sliding between the two elements.

In a second solution shown in FIG. 7B, the protection device comprises a lid-shaped part 61 which thus comprises a plate 610 on which the protective surface is formed and a flange 61 1. This solution will in particular be perfectly adapted to be associated with a support whose viewing zone Z is not closed, as in FIGS. 5A, 5B and 6A, 6B. But it will also be adapted for a viewing chamber configuration as shown in Figures 4A and 4B. This cover 61 indeed encompasses the viewing zone Z (located in a cavity 300 of the support in FIG. 7B) in a sufficiently tight manner by bearing on the support 3 around the zone Z by its flange 61 1, the surface of protection 6 then being formed by the outer face of said plate 610 and is thus positioned above the viewing zone Z. As for the first solution, this cover 61 can be made integral with the support, by any possible means of fixation (glue, screws, etc.) or permanently maintained in the system independently of the support. In the latter case, the connection between the flange 61 1 and the support 3 must be sufficiently tight to prevent dust or impurities from becoming lodged in the space between the chamber 30 and the cover 61. Similarly, the protective surface 6 is advantageously perpendicular to the axis (X) and parallel to the upper face 31 of the support 3.

In a third solution shown in FIG. 7C, the protection device is integrated in the support 3. This solution will be perfectly suitable for a solution where the viewing zone Z is located in a viewing chamber integrated into the support as shown in FIGS. 4A and 4B. The protection means of the protective device are thus formed by the thickness of the upper wall 31 of the support. The protective surface 6 is therefore formed directly by the outer face 310b of the upper wall 31 of the viewing chamber. In this solution, the upper wall 31 of the viewing chamber 30 has a greater thickness, which allows to deport its outer face 310b upwards and thus to move the critical area of dust deposit outside the object plane P.

Other solutions could of course be envisaged, while retaining the characteristics defined above.

Figures 2 to 3B provide a better understanding of the principle of the invention and its interest. Figures 2 to 3B were obtained by observing blood diluted ^1/1000 in a PBS buffer solution (for "Phosphate Buffered Saline"). The sample is placed in a viewing chamber as shown in FIG. 4A, 100 μιη thick, and the bottom of this chamber is 1 mm thick. The bottom of the chamber is positioned at approximately 500 μιη from the surface of the sensor 2. Thus we have the height Hp = 1.5 mm. The light source is a laser diode, positioned 15 cm from the surface of the sensor (Htot = 15 cm).

In Figure 2, the detection system is provided with no protective surface. It can be seen in the generated image that the deposited dust forms diffraction images 50 which can be confused with the diffraction images 40 which correspond to the objects of interest to be analyzed. The treatment is thus made difficult by the presence of dust in the object plane P of the viewing area. Conversely, in FIG. 3A, with a protective surface 6 positioned at a sufficient height H above the object plane P of the viewing zone, it can be seen on the image acquired by the sensor 2 that the dust which are deposited on the surface form diffraction patterns 50 much more spread out and with a lower contrast than the diffraction patterns 40 which correspond to the objects of interest of the sample. In this solution, as in Figures 1 B and 7A, the protective surface is formed by the thickness of a part 60 positioned on the outer face of the upper wall of the viewing chamber. The piece has for example a thickness of 1 cm, so as to be at a sufficient height H of the surface of the sensor, as already described above, for example at least 2 cm.

For its part, FIG. 3B illustrates the image obtained with a protective surface 6 positioned at a height H of 12 cm, that is to say corresponding to 80% of the total height Htot between the surface of the sensor 2 and the source 1 of light radiation. As in FIG. 3A, it can be seen in FIG. 3B that the dusts deposited on the protective surface 6 form diffraction patterns 50 that are even more spread out and more diffuse than in FIG. 3A. They will not be considered during the analysis of the sample.

Advantageously, it is possible to provide a solution for adjusting the position of the protective surface (the height H defined above), so as to adapt the system to the intended application, to the size of the objects of targeted interest with respect to the size of the impurities, the intensity of the light radiation emitted, the position of the light source (the height Htot defined above), the resolution of the sensor employed or the position in height of the viewing chamber (the height Hp of the object plane defined above). According to the solution used described above, it will be for example:

For the first solution, to use interchangeable parts each having a different thickness;

For the second solution, to use interchangeable lids each having a collar of different height;

- For the third solution, to provide different supports each having an upper wall of different thickness. The invention described above, therefore, has a number of advantages, which:

It is simple to implement because it can consist simply of adding a transparent piece on the upper wall of the viewing chamber;

It solves the problem of deposition of dust or impurities on the viewing area, a situation that occurs frequently when the support that is intended to receive the sample remains permanently in the system or even when the support is disposable;

It can easily adapt to the intended application and the different operating constraints, in particular by adjusting the height position of the protective surface.

Claims

1. Protective device for use in an object detection system of interest dispersed in a sample, said system comprising:

A source (1) of light radiation for emitting light radiation (10) along a main direction (X),

An image sensor (2),

A transparent viewing zone (Z) intended to receive said sample, said viewing area being positioned between said source (1) of light radiation and said sensor (2), said source (1) of radiation being intended to emit said light radiation; (10) towards said viewing area so as to illuminate said area along at least one plane, said object plane (P), and said sensor (2) being arranged to acquire on its surface an image of the sample from radiation transmitted through the viewing area by said radiation source,

Said device being characterized in that it comprises means of protection to be inserted between the source (1) of light radiation and said viewing zone (Z) to protect said viewing area from the deposition of impurities, said protection means comprising at least one transparent protective surface (6) configured to form a deposition surface of the impurities, said surface being arranged at a sufficient distance from the viewing area so that any impurities deposited thereon form a diffraction pattern (50) on the image acquired by the sensor (2) which is much larger, less contrasted and more diffuse than diffraction patterns (40) resulting from the diffraction of the objects of interest (4) of the present sample in the viewing area.

2. Device according to claim 1, characterized in that the protection means are chosen so as to define said protective surface (6) at said sufficient distance taking into account the size of the objects of interest targeted in the sample by relative to the size of the impurities, the intensity of the light radiation emitted by said source (1) of light radiation, the position of the source (1) of light radiation relative to the sensor (2), the resolution of the sensor (2) employed and the position of the viewing area (Z) with respect to the sensor (2).

Device according to claim 1 or 2, characterized in that the protective surface (6) is flat.

4. Device according to one of claims 1 to 3, characterized in that the protection means comprise a protective member comprising said protective surface (6).

5. Device according to claim 4, characterized in that the protective part has a first so-called upper face forming the protective surface (6) and support means opposite said upper face, and intended to be supported on the support (3) of the system and one or more lateral faces arranged between said upper face and said support means.

6. Device according to claim 5, characterized in that the support means comprise a lower face opposite to said upper face and parallel thereto.

7. Device according to claim 6, characterized in that said piece (60) is made of a transparent solid material.

8. Device according to claim 6, characterized in that said piece (60) is hollow and defines an internal volume filled with a gas, gas mixture or vacuum.

9. Device according to claim 7 or 8, characterized in that said piece has a thickness defined between its upper face and its lower face corresponding to said positioning distance of the protective surface (6).

10. Device according to claim 5, characterized in that the protective part comprises a cover (61) formed of a plate (610) and a flange (61 1) on its periphery, said protective surface (6) being arranged on the plate, said flange (61 1) being arranged to form said support means against the support (3) at the periphery of said viewing chamber (30).

1 1. Device according to one of claims 4 to 10, characterized in that it comprises means for fixing the protective part.

An object detection system of interest dispersed in a sample, comprising:

An image sensor (2),

A transparent viewing zone (Z) intended to receive said sample, said viewing area being positioned between said source (1) of light radiation and said sensor (2), said source (1) of radiation being intended to emit said light radiation; (10) in direction of said viewing area so as to illuminate said area along at least one plane, said object plane (P), and said sensor (2) being arranged to acquire on its surface an image of the sample from the radiation transmitted to through the viewing area by said radiation source,

said system being characterized in that it comprises:

A protection device according to that defined in claims 1 to 1 1, arranged between the source (1) of radiation and said viewing area (30).

13. System according to claim 12, characterized in that the viewing zone (Z) is located in a viewing chamber (30) integrated in a support (3).

14. System according to claim 13, characterized in that the viewing chamber (30) comprises two opposite walls traversed by said radiation and said upper wall (31) and lower wall (32), said upper wall (31) comprising a first face said inner face (310a), located in the viewing chamber and a second face, said outer face (310b) located outside said viewing chamber.

15. System according to claim 13, characterized in that the viewing chamber (30) comprises two opposite walls traversed by said radiation and said upper wall (31) and lower wall (32), said upper wall having a first face said face. internal (310a), located in the viewing chamber and a second face, said outer face (310b) located outside said viewing chamber, and in that said protective surface (6) of the protection device is formed by the outer face of said upper wall.

16. System according to claim 12, characterized in that the viewing area is located on the surface (31) of a support (3).

17. The system of claim 12, characterized in that the viewing zone is located in a viewing cavity (300) formed by a recess formed on the surface of a support.

18. System according to one of claims 12 to 17, characterized in that the protective surface (6) is positioned at a distance (H) from the sensor surface of between 1 and 100% of the total distance ( Htot) present between the source (1) of radiation and the surface of the sensor.

19. System according to one of claims 12 to 18, characterized in that it comprises a housing adapted to receive said protective device removably.

20. System according to one of claims 12 to 19, characterized in that the source (1) of light radiation comprises at least one light emitting diode or laser.

21. System according to one of Claims 12 to 20, characterized in that the sensor (2) is of the CMOS type.